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1.1 introduction-to-cells

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Eran Earland

1. The cell theory states that all living things are composed of cells, cells are the basic unit of structure and function in living things, and new cells are produced from existing cells. 2. Unicellular organisms carry out all the functions of life within a single cell, including metabolism, reproduction, response to stimuli, homeostasis, excretion, nutrition, and growth. These functions can be observed in organisms like Paramecium and Chlorella through processes like contracting vacuoles and photosynthesis. 3. As cells increase in size, their surface area to volume ratio decreases, limiting their ability to exchange materials and wastes. This limitation on cell size is an important factor in the cell theory.

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Genetics Molecular Biology Ecology Cell Biology Plant Biology Evolution
1.1 introduction-to-cells
Understandings Statement Guidance 1.1.U1 According to the cell theory, living organisms are composed of cells. 1.1.A1 Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae. 1.1.U2 Organisms consisting of only one cell carry out all functions of life in that cell. Students are expected to be able to name and briefly explain these functions of life: nutrition, metabolism, growth, response, excretion, homeostasis and reproduction. 1.1.A2 Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism. Chlorella or Scenedesmus are suitable photosynthetic unicells, but Euglena should be avoided as it can feed heterotrophically. 1.1.U3 Surface area to volume ratio is important in the limitation of cell size. 1.1.U4 Multicellular organisms have properties that emerge from the interaction of their cellular components.
Applications and Skills Statement Guidance 1.1.U5 Specialized tissues can develop by cell differentiation in multicellular organisms. 1.1.U6 Differentiation involves the expression of some genes and not others in a cell’s genome. 1.1.U7 The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development and also makes stem cells suitable for therapeutic uses. 1.1.A3 Use of stem cells to treat Stargardt’s disease and one other named condition. 1.1.A4 Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues. 1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1) Scale bars are useful as a way of indicating actual sizes in drawings and micrographs.
Pre-class notes and Flipped Video • Watch the video and use the bullet points as a guide as you watch THEN • Fill in Notes up to the end of Part 1
THE ORIGINS OF CELL THEORY: The discovery of cells was linked to the development of the microscope 1590: Zacharias Janssen invents the compound microscope 1665: Robert Hooke studies cork and names the structures “cells” 1675: Anton van Leeuwenhoek discovers unicellular organisms 1838: Matthias Schleiden suggests that all plants are made of cells 1839: Theodor Schwann suggests that all animal were made from cells 1858: Rudolph Virchow suggests all cells come from cells
CELL THEORY STATES THAT: All living organisms are made of one or more cells Cells are the smallest units of life Cells only be formed from the division of other cells All cells exhibit the features of living organisms: TASK: What are the features that make something ‘living’? 1.1.U1 - According to the cell theory, living organisms are composed of cells.
1.1U2 Organisms consisting of only one cell carry out all functions of life in that cell. • Metabolism – Living things undertake essential chemical reactions • Reproduction – Living things produce offspring, either sexually or asexually • Sensitivity – Living things are responsive to internal and external stimuli • Homeostasis – Living things maintain a stable internal environment • Excretion – Living things exhibit the removal of waste products • Nutrition – Living things exchange materials and gases with the environment • Growth – Living things can move and change shape or size Mnemonic: MR SHENG
THE CELL THEORY DEBATE… Create a table for arguments for cell theory, and those that question it with atypical cells. Skeletal muscle is made of large fibres (30mm) and have multiple nuclei Fungal hyphae have multiple nuclei and are not clearly divided The microscope has shown all living things to made of cells or cell products Cells removed from tissue can grow independently for a short amount of time Nothing smaller than a cell has been found to be able to carry out all the functions of life Life may have originated from smaller organelles (mitochondria & chloroplasts) that then became encapsulated within cells Phloem sieve cells have few internal organelles and their metabolism is controlled by companion cells Giant algae can grow to 100mm despite having just 1 nucleus Experiments by Pasteur and Redi proved spontaneous generation of cells did not occur 1.1 A1 Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae.
FOR AGAINST THE CELL THEORY DEBATE… Skeletal muscle is made of large fibres and have multiple nuclei The microscope has shown all living things to be made of cells or cell products Cells removed from tissue can grow independently for a short amount of time Nothing smaller than a cell has been found to be able to carry out all the functions of life Life may have originated from smaller organelles (mitochondria & chloroplasts) that then became encapsulated within cells Fungal hyphae have multiple nuclei and are not clearly divided Phloem sieve cells have few internal organelles and their metabolism is controlled by companion cells Experiments by Pasteur and Redi proved spontaneous generation of cells did not occur Giant algae can grow to 100mm despite having just 1 nucleus Exceptions/Discrepencies that you need to know about! 1.1 A1 Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae.
Striated muscle fibres: Muscle cells fuse to form fibres that may be very long (>300mm) Consequently, they have multiple nuclei despite being surrounded by a single, continuous plasma membrane Challenges the idea that cells always function as autonomous units Aseptate fungal hyphae: Fungi may have filamentous structures called hyphae, which are separated into cells by internal walls called septa Some fungi are not partitioned by septa and hence have a continuous cytoplasm along the length of the hyphae Challenges the idea that living structures are composed of discrete cells Giant Algae Certain species of unicellular algae may grow to very large sizes (e.g. Acetabularia may exceed 7 cm in length) Challenges the idea that larger organisms are always made of many microscopic cells
How does this paramecium show the functions of life? 1.1 A2 Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.
Source: http://umanitoba.ca/Biology/BIOL1030/Lab1/biolab1_3.html#Ciliophora Homeostasis – contractile vacuole fill up with water and expel I through the plasma membrane to manage the water content Reproduction – The nucleus can divide to support cell division by mitosis, reproduction is often asexual Metabolism – most metabolic pathways happen in the cytoplasm Growth – after consuming and assimilating biomass from food the paramecium will get larger until it divides. Response – the wave action of the cilia moves the paramecium in response to changes in the environment, e.g. towards food. Excretion – the plasma membrane control the entry and exit of substances including expulsion of metabolic waste Nutrition – food vacuoles contain organisms the paramecium has consumed 1.1 A2 Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.
How does this algae show the functions of life? Source: http://www.algae.info/Algaecomplete.aspx 1.1 A2 Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.
Homeostasis – contractile vacuole fill up with water and expel I through the plasma membrane to manage the water content Reproduction – The nucleus can divide to support cell division, by mitosis (these cells are undergoing cytokinesis) Metabolism – most metabolic pathways happen in the cytoplasm Growth – after consuming and assimilating biomass from food the algae will get larger until it divides. Response – the wave action of the cilia moves the algae in response to changes in the environment, e.g. towards light. Excretion – the plasma membrane control the entry and exit of substances including the difussion out of waste oxygen Nutrition – photosynthe sis happens inside the chloroplasts to provide the algae with food 1.1 A2 Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.
SURFACE AREA TO VOLUME RATIO •As an organism increases in size, its surface area to volume ratio decreases. This can be easily seen by comparing the following cubes •Volume increases more rapidly than the surface area 1.1 U3 Surface area to volume ratio is important in the limitation of cell size.
SURFACE AREA LIMITS CELL SIZE… •Cell surface is needed for the transport of food into the cell, heat in and out, and waste products out of the cell •Rate of metabolism is a function of a cells volume •As cell size increases the surface area is no longer sufficient to allow these exchanges at a rate that supports life. •This prevents cells from being big! •Experiment  Phenylthalein cubes and acid! http://www.youtube.com/watch? v=xuG4ZZ1GbzI 1.1 U3 Surface area to volume ratio is important in the limitation of cell size.
SURFACE AREA LIMITS CELL SIZE… •Experiment  Phenylthalein cubes and acid! http://www.youtube.com/watch? v=xuG4ZZ1GbzI 1.1 U3 Surface area to volume ratio is important in the limitation of cell size.
1.1 U3 Surface area to volume ratio is important in the limitation of cell size.
In summary: •The rate of metabolism of a cell is a function of its mass / volume •The rate of material exchange in and out of a cell is a function of its surface area •As the cell grows, volume increases faster than surface area (leading to a decreased SA:Vol ratio) •If the metabolic rate is greater than the rate of exchange of vital materials and wastes, the cell will eventually die •Hence the cell must consequently divide in order to restore a viable SA:Vol ratio and survive •Cells and tissues specialized for gas or material exchange (e.g. alveoli) will increase their surface area to optimize the transfer of materials 1.1 U3 Surface area to volume ratio is important in the limitation of cell size.
1.1.U4 Multicellular organisms have properties that emerge from the interaction of their cellular components. Emergent properties arise from the interaction of component parts. The whole is greater than the sum of its parts. Multicellular organisms are capable of completing functions that individual cells could not undertake - this is due to the interaction between cells producing new functions.
As a model consider the electric light bulb. The bulb is the system and is composed of a filament made of tungsten, a metal cup, and a glass container. We can study the parts individually how they function and the properties they posses. These would be the properties of : •Tungsten •Metal cup •Glass container When studied individually they do not allow the prediction of the properties of the light bulb. Only when we combine them to form the bulb can these properties be determined. There is nothing supernatural about the emergent properties rather it is simply the combination of the parts that results in new properties emerging. Source: http://en.wikipedia.org/wiki/File:Gluehlampe_01_KMJ.jpg 1.1.U4 Multicellular organisms have properties that emerge from the interaction of their cellular components.
End of Part 1 – Take a Break • Make note of any questions you have so you remember to ask next class • Bring a device to do the online Google quiz • Scope of Next class • Warm Up & questions • Added insight and connections to other topics • Practice • Quick check Google quiz
https://www.youtube.com/watch? v=hKnRKy5Wu7c
Below is a link to a whole bunch of mindfulness guided meditations you can use at home and an app • https://www.youtube.com/wat ch? v=6p_yaNFSYao&list=RD6p_yaN FSYao&start_radio=1&t=0
UNICELLULAR ORGANISMS •Some organisms are composed of only one cell. • eg: Paramecium, Chlamydomonas, Euglena, Chlorella, Amoeba •This single cells has to carry out all the activities essential to living organisms. • ie: obtaining food, excreting waste products, producing offspring
Prokaryotic versus Eukaryotic Classification of Life into Kingdoms 6 Kingdoms 3 Domains Cell Cycle, Mitosis, Meiosis, Binary Fission Genetics and Gene Expression
EMMERGENT PROPERTIES Interaction between different cells to create new functions Allows multicellular organisms to complete functions that individual cells cannot E.g. Cell  Tissue  Organ  System Recall – 1.1 U4 Multicellular organisms have properties that emerge from the interaction of their cellular components.
MULTICELLULAR ORGANISMS •Multicellular organisms consist of many cells. •These cells do not have to carry out many different functions. •Instead they can become specialised for one particular function and carry it out very efficiently. •This is called differentiation. • eg: muscle cell, nerve cell, xylem cell •Each cell has all the genes for the organism BUT only certain genes are turned on, the ones needed for that cells particular function. The others are switched off because the cell does not do that function.  Gene expression
• Differentiation is the process during development whereby newly formed cells become more specialized and distinct from one another as they mature • All cells of an organism share an identical genome – each cell contains the entire set of genetic instructions for that organism • The activation of different instructions (genes) within a given cell by chemical signals will cause it to differentiate
Extensions & Connections Gene Packaging •Within the nucleus of a eukaryotic cell, DNA is packaged with proteins to form chromatin • Active genes are usually packaged in an expanded form called euchromatin that is accessible to transcriptional machinery • Inactive genes are typically packaged in a more condensed form called heterochromatin (saves space, not transcribed) Differentiated cells will have different regions of DNA packaged as euchromatin and heterochromatin according to their specific function
STEM CELLS Unspecialised and undifferentiated cells with 2 key qualities 1. Self renewal  Can divide and replicate 2. Potency  Capable of differentiation  Derived from embryos or from the placenta/umbilical cord
https://www.youtube.com/watch? v=9xdEsuroJaE&feature=player_emb edded
This cell Can form the Embryo and placenta This cell Can just form the embryo Fully mature
Kinds of Stem CellsKinds of Stem Cells Stem cellStem cell typetype DescriptionDescription ExamplesExamples TotipotentTotipotent Each cell can developEach cell can develop into a new individualinto a new individual Cells from early (1-Cells from early (1- 3 days) embryos3 days) embryos PluripotentPluripotent Cells can form any (overCells can form any (over 200) cell types200) cell types Some cells ofSome cells of blastocyst (5 to 14blastocyst (5 to 14 days)days) MultipotentMultipotent Cells differentiated, butCells differentiated, but can form a number ofcan form a number of other tissuesother tissues Fetal tissue, cordFetal tissue, cord blood, and adultblood, and adult stem cellsstem cells
Stem Cells retain the capacity to divide and can differentiate along divergent pathways. Totipotent Can differentiate into any type of cell. Pluripotent Can differentiate into many types of cell. Multipotent Can differentiate into a few closely-related types of cell. Unipotent Can regenerate but can only differentiate into their associated cell type (e.g. liver stem cells can only make liver cells). Image from: http://en.wikipedia.org/wiki/Stem_cell
Stem cells can be used to replace damaged or diseased cells with healthy, functioning ones This process requires: •The use of biochemical solutions to trigger the differentiation of stem cells into the desired cell type •Surgical implantation of cells into the patient’s own tissue •Suppression of host immune system to prevent rejection of cells (if stem cells are from foreign source) •Careful monitoring of new cells to ensure they do not become cancerous
Examples of Stem Cell Therapy 1. Stargardt’s Disease •An inherited form of juvenile macular degeneration that causes progressive vision loss to the point of blindness •Caused by a gene mutation that impairs energy transport in retinal photoreceptor cells, causing them to degenerate •Treated by replacing dead cells in the retina with functioning ones derived from stem cells
Examples of Stem Cell Therapy 2. Parkinson’s Disease •A degenerative disorder of the central nervous system caused by the death of dopamine-secreting cells in the midbrain •Dopamine is a neurotransmitter responsible for transmitting signals involved in the production of smooth, purposeful movements •Consequently, individuals with Parkinson’s disease typically exhibit tremors, rigidity, slowness of movement and postural instability •Treated by replacing dead nerve cells with living, dopamine- producing ones
Other Therapeutic Examples Leukemia: Bone marrow transplants for cancer patients who are immunocompromised as a result of chemotherapy Paraplegia: Repair damage caused by spinal injuries to enable paralysed victims to regain movement Diabetes: Replace non- functioning islet cells with those capable of producing insulin in type I diabetics Burn victims: Graft new skin cells to replace damaged tissue
Treatment of Stargardt’s Disease Juvenile Macular Degeneration 1.1.A3Use of stem cells to treat Stargardt’s disease and one other named condition.
https://www.youtube.com/watch?v=Kn3lgskKA08
1.1 introduction-to-cells
1.1 introduction-to-cells
1.1 introduction-to-cells
Stem cells can be derived from one of three sources: •Embryos (may be specially created by therapeutic cloning) •Umbilical cord blood or placenta of a new-born baby •Certain adult tissues like the bone marrow (cells are not pluripotent) The ethical considerations associated with the therapeutic use of stem cells will depend on the source •Using multipotent adult tissue may be effective for certain conditions, but is limited in its scope of application •Stem cells derived from umbilical cord blood need to be stored and preserved at cost, raising issues of availability and access •The greatest yield of pluripotent stem cells comes from embryos, but requires the destruction of a potential living organism
Artificial Stem Cell Techniques Stem cells can be artificially generated via nuclear transfer or nuclear reprogramming, with distinct benefits and disadvantages Somatic cell nuclear transfer (SCNT): Involves the creation of embryonic clones by fusing a diploid nucleus with an enucleated egg cell (therapeutic cloning) More embryos are created by this process than needed, raising ethical concerns about the exigency of excess embryos Nuclear reprogramming: Induce a change in the gene expression profile of a cell in order to transform it into a different cell type (transdifferentiation) Involves the use of oncogenic retroviruses and transgenes, increasing the risk of health consequences (i.e. cancer)
1.1 introduction-to-cells
1.1 introduction-to-cells
1.1 introduction-to-cells
End of Part 2 – Take a Break • Make note of any questions you have so you remember to ask next class • Bring a device to do the online Google quiz • Scope of Next class • Warm Up & questions • Added insight and connections to other topics • Practice Time • Quick check Google quiz
Microscopes – A Comparison Light Microscope SEM TEM 1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)
Electron Micrograph of a Cell Ref: Roberts etal
WHAT SIZE? •Although even the largest cell is too small to see with the unaided eye, it is important to have an understanding of the relative sizes of cells and organelles. •You need to know the relative units; • 10-3 of a metre = 1 millimetre or 1mm • 10-6 of a metre or 10-3 of a millimetre = 1 micrometre or 1μm • 10-9 of a metre or 10-6 of a millimetre or 10-3 of a micrometre = 1 nanometre or 1nm The most useful units for measuring the sizes of cells and structures within them are nanometres (nm) and micrometres (μm)
1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1) Relative Sizes of Biological Materials Eukaryotic cell (plant) = ~100 μm Eukaryotic cell (animal) = ~10 – 50 μm Organelle (e.g. mitochondrion) = ~1 – 10 μm Prokaryotic cell (bacteria) = ~1 – 5 μm Virus = ~100 nm Plasma membrane = ~7.5 nm Molecules (e.g. glucose) = ~1 nm Atoms = ~100 pm
1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1) You MUST show your work this way with units. This is good practice for all science and also math
1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1) 5mm = ? nm  5mm x 1000000nm = 5,000,000 nm 1mm 4.4cm = ?nm  4.4 cm x 10,000,000nm = 44,000,000 nm 1cm 6.8mm=? um  6.8mm x 1000 um = 6,800 um 1mm 3.5cm = ? um  3.5cm x10,000 um = 5,000,000 nm 1cm 7.1 um = ? cm  7.1 um x 1 cm = 0.00071 cm 10,000 um 1520nm = ?mm  1520nm x 1mm = 0.00152 mm 1000000mm
1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)
CALCULATING MAGNIFICATION Magnification = Image Size Real Size If the size of the bar was 2cm: Magnification = 20,000µm 5µm Magnification = 4,000 X Make sure the units are the same! (20,000µm = 2cm  the size of the bar!) 1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)
CALCULATING CELL SIZE •An Alternative is that the electron Micrograph states the magnification. •From this you can calculate the actual size: • Measure the dimension of the cell. 41mm • Divide this by the magnification. 41 / 750 = 0.055mm • Convert to a sensible unit. 0.055mm X 1000 = 55μm 750X TASK: Complete the magnification worksheet https://www.youtube.com/watch?v=L1d- 02yRsRE&list=UU0PKoMASr5dgW_v5-93d_mw 1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)
Finding Total Magnification and the Diameter of the Field of View When using a Microscope Power Total Magnification Diameter of FOV in mm Diameter in um High 400x 0.45 mm 450 um Medium 100x 1.8 mm 1800 um Low 40x 4.5 mm 4500 um Total Magnification = (power of the eye piece) x (Power of the objective lens) Field of View = diameter of circle you can see for each magnification Scale Bars: Images often carry a scale bar which is a line on the image that shows how long the line is in the real specimen. The easiest way to add a scale bar is to find the actual size of the specimen and then draw a line beside the specimen indicating the measurement Actual Size of Specimen: estimate how many could fit end to end across the diameter of the field of view, then use the following formula Size of Specimen = diameter of FOV # of objects the fit across Drawing Magnification: this is used to determine how many times bigger your drawing is than the actual size Drawing Magnification = drawing size Actual size
IB Microscope drawing and label requirements
Here is a great video going over this entire topic if you need a review. It is long though

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1.1 introduction-to-cells

  • 3. Understandings Statement Guidance 1.1.U1 According to the cell theory, living organisms are composed of cells. 1.1.A1 Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae. 1.1.U2 Organisms consisting of only one cell carry out all functions of life in that cell. Students are expected to be able to name and briefly explain these functions of life: nutrition, metabolism, growth, response, excretion, homeostasis and reproduction. 1.1.A2 Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism. Chlorella or Scenedesmus are suitable photosynthetic unicells, but Euglena should be avoided as it can feed heterotrophically. 1.1.U3 Surface area to volume ratio is important in the limitation of cell size. 1.1.U4 Multicellular organisms have properties that emerge from the interaction of their cellular components.
  • 4. Applications and Skills Statement Guidance 1.1.U5 Specialized tissues can develop by cell differentiation in multicellular organisms. 1.1.U6 Differentiation involves the expression of some genes and not others in a cell’s genome. 1.1.U7 The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development and also makes stem cells suitable for therapeutic uses. 1.1.A3 Use of stem cells to treat Stargardt’s disease and one other named condition. 1.1.A4 Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues. 1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1) Scale bars are useful as a way of indicating actual sizes in drawings and micrographs.
  • 5. Pre-class notes and Flipped Video • Watch the video and use the bullet points as a guide as you watch THEN • Fill in Notes up to the end of Part 1
  • 6. THE ORIGINS OF CELL THEORY: The discovery of cells was linked to the development of the microscope 1590: Zacharias Janssen invents the compound microscope 1665: Robert Hooke studies cork and names the structures “cells” 1675: Anton van Leeuwenhoek discovers unicellular organisms 1838: Matthias Schleiden suggests that all plants are made of cells 1839: Theodor Schwann suggests that all animal were made from cells 1858: Rudolph Virchow suggests all cells come from cells
  • 7. CELL THEORY STATES THAT: All living organisms are made of one or more cells Cells are the smallest units of life Cells only be formed from the division of other cells All cells exhibit the features of living organisms: TASK: What are the features that make something ‘living’? 1.1.U1 - According to the cell theory, living organisms are composed of cells.
  • 8. 1.1U2 Organisms consisting of only one cell carry out all functions of life in that cell. • Metabolism – Living things undertake essential chemical reactions • Reproduction – Living things produce offspring, either sexually or asexually • Sensitivity – Living things are responsive to internal and external stimuli • Homeostasis – Living things maintain a stable internal environment • Excretion – Living things exhibit the removal of waste products • Nutrition – Living things exchange materials and gases with the environment • Growth – Living things can move and change shape or size Mnemonic: MR SHENG
  • 9. THE CELL THEORY DEBATE… Create a table for arguments for cell theory, and those that question it with atypical cells. Skeletal muscle is made of large fibres (30mm) and have multiple nuclei Fungal hyphae have multiple nuclei and are not clearly divided The microscope has shown all living things to made of cells or cell products Cells removed from tissue can grow independently for a short amount of time Nothing smaller than a cell has been found to be able to carry out all the functions of life Life may have originated from smaller organelles (mitochondria & chloroplasts) that then became encapsulated within cells Phloem sieve cells have few internal organelles and their metabolism is controlled by companion cells Giant algae can grow to 100mm despite having just 1 nucleus Experiments by Pasteur and Redi proved spontaneous generation of cells did not occur 1.1 A1 Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae.
  • 10. FOR AGAINST THE CELL THEORY DEBATE… Skeletal muscle is made of large fibres and have multiple nuclei The microscope has shown all living things to be made of cells or cell products Cells removed from tissue can grow independently for a short amount of time Nothing smaller than a cell has been found to be able to carry out all the functions of life Life may have originated from smaller organelles (mitochondria & chloroplasts) that then became encapsulated within cells Fungal hyphae have multiple nuclei and are not clearly divided Phloem sieve cells have few internal organelles and their metabolism is controlled by companion cells Experiments by Pasteur and Redi proved spontaneous generation of cells did not occur Giant algae can grow to 100mm despite having just 1 nucleus Exceptions/Discrepencies that you need to know about! 1.1 A1 Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae.
  • 11. Striated muscle fibres: Muscle cells fuse to form fibres that may be very long (>300mm) Consequently, they have multiple nuclei despite being surrounded by a single, continuous plasma membrane Challenges the idea that cells always function as autonomous units Aseptate fungal hyphae: Fungi may have filamentous structures called hyphae, which are separated into cells by internal walls called septa Some fungi are not partitioned by septa and hence have a continuous cytoplasm along the length of the hyphae Challenges the idea that living structures are composed of discrete cells Giant Algae Certain species of unicellular algae may grow to very large sizes (e.g. Acetabularia may exceed 7 cm in length) Challenges the idea that larger organisms are always made of many microscopic cells
  • 12. How does this paramecium show the functions of life? 1.1 A2 Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.
  • 13. Source: http://umanitoba.ca/Biology/BIOL1030/Lab1/biolab1_3.html#Ciliophora Homeostasis – contractile vacuole fill up with water and expel I through the plasma membrane to manage the water content Reproduction – The nucleus can divide to support cell division by mitosis, reproduction is often asexual Metabolism – most metabolic pathways happen in the cytoplasm Growth – after consuming and assimilating biomass from food the paramecium will get larger until it divides. Response – the wave action of the cilia moves the paramecium in response to changes in the environment, e.g. towards food. Excretion – the plasma membrane control the entry and exit of substances including expulsion of metabolic waste Nutrition – food vacuoles contain organisms the paramecium has consumed 1.1 A2 Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.
  • 14. How does this algae show the functions of life? Source: http://www.algae.info/Algaecomplete.aspx 1.1 A2 Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.
  • 15. Homeostasis – contractile vacuole fill up with water and expel I through the plasma membrane to manage the water content Reproduction – The nucleus can divide to support cell division, by mitosis (these cells are undergoing cytokinesis) Metabolism – most metabolic pathways happen in the cytoplasm Growth – after consuming and assimilating biomass from food the algae will get larger until it divides. Response – the wave action of the cilia moves the algae in response to changes in the environment, e.g. towards light. Excretion – the plasma membrane control the entry and exit of substances including the difussion out of waste oxygen Nutrition – photosynthe sis happens inside the chloroplasts to provide the algae with food 1.1 A2 Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.
  • 16. SURFACE AREA TO VOLUME RATIO •As an organism increases in size, its surface area to volume ratio decreases. This can be easily seen by comparing the following cubes •Volume increases more rapidly than the surface area 1.1 U3 Surface area to volume ratio is important in the limitation of cell size.
  • 17. SURFACE AREA LIMITS CELL SIZE… •Cell surface is needed for the transport of food into the cell, heat in and out, and waste products out of the cell •Rate of metabolism is a function of a cells volume •As cell size increases the surface area is no longer sufficient to allow these exchanges at a rate that supports life. •This prevents cells from being big! •Experiment  Phenylthalein cubes and acid! http://www.youtube.com/watch? v=xuG4ZZ1GbzI 1.1 U3 Surface area to volume ratio is important in the limitation of cell size.
  • 18. SURFACE AREA LIMITS CELL SIZE… •Experiment  Phenylthalein cubes and acid! http://www.youtube.com/watch? v=xuG4ZZ1GbzI 1.1 U3 Surface area to volume ratio is important in the limitation of cell size.
  • 19. 1.1 U3 Surface area to volume ratio is important in the limitation of cell size.
  • 20. In summary: •The rate of metabolism of a cell is a function of its mass / volume •The rate of material exchange in and out of a cell is a function of its surface area •As the cell grows, volume increases faster than surface area (leading to a decreased SA:Vol ratio) •If the metabolic rate is greater than the rate of exchange of vital materials and wastes, the cell will eventually die •Hence the cell must consequently divide in order to restore a viable SA:Vol ratio and survive •Cells and tissues specialized for gas or material exchange (e.g. alveoli) will increase their surface area to optimize the transfer of materials 1.1 U3 Surface area to volume ratio is important in the limitation of cell size.
  • 21. 1.1.U4 Multicellular organisms have properties that emerge from the interaction of their cellular components. Emergent properties arise from the interaction of component parts. The whole is greater than the sum of its parts. Multicellular organisms are capable of completing functions that individual cells could not undertake - this is due to the interaction between cells producing new functions.
  • 22. As a model consider the electric light bulb. The bulb is the system and is composed of a filament made of tungsten, a metal cup, and a glass container. We can study the parts individually how they function and the properties they posses. These would be the properties of : •Tungsten •Metal cup •Glass container When studied individually they do not allow the prediction of the properties of the light bulb. Only when we combine them to form the bulb can these properties be determined. There is nothing supernatural about the emergent properties rather it is simply the combination of the parts that results in new properties emerging. Source: http://en.wikipedia.org/wiki/File:Gluehlampe_01_KMJ.jpg 1.1.U4 Multicellular organisms have properties that emerge from the interaction of their cellular components.
  • 23. End of Part 1 – Take a Break • Make note of any questions you have so you remember to ask next class • Bring a device to do the online Google quiz • Scope of Next class • Warm Up & questions • Added insight and connections to other topics • Practice • Quick check Google quiz
  • 25. Below is a link to a whole bunch of mindfulness guided meditations you can use at home and an app • https://www.youtube.com/wat ch? v=6p_yaNFSYao&list=RD6p_yaN FSYao&start_radio=1&t=0
  • 26. UNICELLULAR ORGANISMS •Some organisms are composed of only one cell. • eg: Paramecium, Chlamydomonas, Euglena, Chlorella, Amoeba •This single cells has to carry out all the activities essential to living organisms. • ie: obtaining food, excreting waste products, producing offspring
  • 27. Prokaryotic versus Eukaryotic Classification of Life into Kingdoms 6 Kingdoms 3 Domains Cell Cycle, Mitosis, Meiosis, Binary Fission Genetics and Gene Expression
  • 28. EMMERGENT PROPERTIES Interaction between different cells to create new functions Allows multicellular organisms to complete functions that individual cells cannot E.g. Cell  Tissue  Organ  System Recall – 1.1 U4 Multicellular organisms have properties that emerge from the interaction of their cellular components.
  • 29. MULTICELLULAR ORGANISMS •Multicellular organisms consist of many cells. •These cells do not have to carry out many different functions. •Instead they can become specialised for one particular function and carry it out very efficiently. •This is called differentiation. • eg: muscle cell, nerve cell, xylem cell •Each cell has all the genes for the organism BUT only certain genes are turned on, the ones needed for that cells particular function. The others are switched off because the cell does not do that function.  Gene expression
  • 30. • Differentiation is the process during development whereby newly formed cells become more specialized and distinct from one another as they mature • All cells of an organism share an identical genome – each cell contains the entire set of genetic instructions for that organism • The activation of different instructions (genes) within a given cell by chemical signals will cause it to differentiate
  • 31. Extensions & Connections Gene Packaging •Within the nucleus of a eukaryotic cell, DNA is packaged with proteins to form chromatin • Active genes are usually packaged in an expanded form called euchromatin that is accessible to transcriptional machinery • Inactive genes are typically packaged in a more condensed form called heterochromatin (saves space, not transcribed) Differentiated cells will have different regions of DNA packaged as euchromatin and heterochromatin according to their specific function
  • 32. STEM CELLS Unspecialised and undifferentiated cells with 2 key qualities 1. Self renewal  Can divide and replicate 2. Potency  Capable of differentiation  Derived from embryos or from the placenta/umbilical cord
  • 34. This cell Can form the Embryo and placenta This cell Can just form the embryo Fully mature
  • 35. Kinds of Stem CellsKinds of Stem Cells Stem cellStem cell typetype DescriptionDescription ExamplesExamples TotipotentTotipotent Each cell can developEach cell can develop into a new individualinto a new individual Cells from early (1-Cells from early (1- 3 days) embryos3 days) embryos PluripotentPluripotent Cells can form any (overCells can form any (over 200) cell types200) cell types Some cells ofSome cells of blastocyst (5 to 14blastocyst (5 to 14 days)days) MultipotentMultipotent Cells differentiated, butCells differentiated, but can form a number ofcan form a number of other tissuesother tissues Fetal tissue, cordFetal tissue, cord blood, and adultblood, and adult stem cellsstem cells
  • 36. Stem Cells retain the capacity to divide and can differentiate along divergent pathways. Totipotent Can differentiate into any type of cell. Pluripotent Can differentiate into many types of cell. Multipotent Can differentiate into a few closely-related types of cell. Unipotent Can regenerate but can only differentiate into their associated cell type (e.g. liver stem cells can only make liver cells). Image from: http://en.wikipedia.org/wiki/Stem_cell
  • 37. Stem cells can be used to replace damaged or diseased cells with healthy, functioning ones This process requires: •The use of biochemical solutions to trigger the differentiation of stem cells into the desired cell type •Surgical implantation of cells into the patient’s own tissue •Suppression of host immune system to prevent rejection of cells (if stem cells are from foreign source) •Careful monitoring of new cells to ensure they do not become cancerous
  • 38. Examples of Stem Cell Therapy 1. Stargardt’s Disease •An inherited form of juvenile macular degeneration that causes progressive vision loss to the point of blindness •Caused by a gene mutation that impairs energy transport in retinal photoreceptor cells, causing them to degenerate •Treated by replacing dead cells in the retina with functioning ones derived from stem cells
  • 39. Examples of Stem Cell Therapy 2. Parkinson’s Disease •A degenerative disorder of the central nervous system caused by the death of dopamine-secreting cells in the midbrain •Dopamine is a neurotransmitter responsible for transmitting signals involved in the production of smooth, purposeful movements •Consequently, individuals with Parkinson’s disease typically exhibit tremors, rigidity, slowness of movement and postural instability •Treated by replacing dead nerve cells with living, dopamine- producing ones
  • 40. Other Therapeutic Examples Leukemia: Bone marrow transplants for cancer patients who are immunocompromised as a result of chemotherapy Paraplegia: Repair damage caused by spinal injuries to enable paralysed victims to regain movement Diabetes: Replace non- functioning islet cells with those capable of producing insulin in type I diabetics Burn victims: Graft new skin cells to replace damaged tissue
  • 41. Treatment of Stargardt’s Disease Juvenile Macular Degeneration 1.1.A3Use of stem cells to treat Stargardt’s disease and one other named condition.
  • 46. Stem cells can be derived from one of three sources: •Embryos (may be specially created by therapeutic cloning) •Umbilical cord blood or placenta of a new-born baby •Certain adult tissues like the bone marrow (cells are not pluripotent) The ethical considerations associated with the therapeutic use of stem cells will depend on the source •Using multipotent adult tissue may be effective for certain conditions, but is limited in its scope of application •Stem cells derived from umbilical cord blood need to be stored and preserved at cost, raising issues of availability and access •The greatest yield of pluripotent stem cells comes from embryos, but requires the destruction of a potential living organism
  • 47. Artificial Stem Cell Techniques Stem cells can be artificially generated via nuclear transfer or nuclear reprogramming, with distinct benefits and disadvantages Somatic cell nuclear transfer (SCNT): Involves the creation of embryonic clones by fusing a diploid nucleus with an enucleated egg cell (therapeutic cloning) More embryos are created by this process than needed, raising ethical concerns about the exigency of excess embryos Nuclear reprogramming: Induce a change in the gene expression profile of a cell in order to transform it into a different cell type (transdifferentiation) Involves the use of oncogenic retroviruses and transgenes, increasing the risk of health consequences (i.e. cancer)
  • 51. End of Part 2 – Take a Break • Make note of any questions you have so you remember to ask next class • Bring a device to do the online Google quiz • Scope of Next class • Warm Up & questions • Added insight and connections to other topics • Practice Time • Quick check Google quiz
  • 52. Microscopes – A Comparison Light Microscope SEM TEM 1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)
  • 53. Electron Micrograph of a Cell Ref: Roberts etal
  • 54. WHAT SIZE? •Although even the largest cell is too small to see with the unaided eye, it is important to have an understanding of the relative sizes of cells and organelles. •You need to know the relative units; • 10-3 of a metre = 1 millimetre or 1mm • 10-6 of a metre or 10-3 of a millimetre = 1 micrometre or 1μm • 10-9 of a metre or 10-6 of a millimetre or 10-3 of a micrometre = 1 nanometre or 1nm The most useful units for measuring the sizes of cells and structures within them are nanometres (nm) and micrometres (μm)
  • 55. 1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1) Relative Sizes of Biological Materials Eukaryotic cell (plant) = ~100 μm Eukaryotic cell (animal) = ~10 – 50 μm Organelle (e.g. mitochondrion) = ~1 – 10 μm Prokaryotic cell (bacteria) = ~1 – 5 μm Virus = ~100 nm Plasma membrane = ~7.5 nm Molecules (e.g. glucose) = ~1 nm Atoms = ~100 pm
  • 56. 1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1) You MUST show your work this way with units. This is good practice for all science and also math
  • 57. 1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1) 5mm = ? nm  5mm x 1000000nm = 5,000,000 nm 1mm 4.4cm = ?nm  4.4 cm x 10,000,000nm = 44,000,000 nm 1cm 6.8mm=? um  6.8mm x 1000 um = 6,800 um 1mm 3.5cm = ? um  3.5cm x10,000 um = 5,000,000 nm 1cm 7.1 um = ? cm  7.1 um x 1 cm = 0.00071 cm 10,000 um 1520nm = ?mm  1520nm x 1mm = 0.00152 mm 1000000mm
  • 58. 1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)
  • 59. CALCULATING MAGNIFICATION Magnification = Image Size Real Size If the size of the bar was 2cm: Magnification = 20,000µm 5µm Magnification = 4,000 X Make sure the units are the same! (20,000µm = 2cm  the size of the bar!) 1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)
  • 60. CALCULATING CELL SIZE •An Alternative is that the electron Micrograph states the magnification. •From this you can calculate the actual size: • Measure the dimension of the cell. 41mm • Divide this by the magnification. 41 / 750 = 0.055mm • Convert to a sensible unit. 0.055mm X 1000 = 55μm 750X TASK: Complete the magnification worksheet https://www.youtube.com/watch?v=L1d- 02yRsRE&list=UU0PKoMASr5dgW_v5-93d_mw 1.1.S1 Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells. Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in drawings or micrographs. (Practical 1)
  • 61. Finding Total Magnification and the Diameter of the Field of View When using a Microscope Power Total Magnification Diameter of FOV in mm Diameter in um High 400x 0.45 mm 450 um Medium 100x 1.8 mm 1800 um Low 40x 4.5 mm 4500 um Total Magnification = (power of the eye piece) x (Power of the objective lens) Field of View = diameter of circle you can see for each magnification Scale Bars: Images often carry a scale bar which is a line on the image that shows how long the line is in the real specimen. The easiest way to add a scale bar is to find the actual size of the specimen and then draw a line beside the specimen indicating the measurement Actual Size of Specimen: estimate how many could fit end to end across the diameter of the field of view, then use the following formula Size of Specimen = diameter of FOV # of objects the fit across Drawing Magnification: this is used to determine how many times bigger your drawing is than the actual size Drawing Magnification = drawing size Actual size
  • 62. IB Microscope drawing and label requirements
  • 63. Here is a great video going over this entire topic if you need a review. It is long though

Editor's Notes

  • #2: Book for homework How you take notes is up to you
  • #3: Paper 1 – multiple choice Paper 2 – data based, short answer, 1 extended response Paper 3 – short answer, experimental skills, extended response
  • #11: Other arguments against: organs contain large amounts of extracellular material;e.g. vitreous humour of eye / mineral deposits in bone / xylem in trees
  • #35: CLICK! This diagram will eventually show the entire range of development, from fertilized egg to mature cell types in the body. Each cell in the 8-cell embryo, here in red, can generate every cell in the embryo as well as the placenta and extra-embryonic tissues. These cells are called CLICK! TOTIPOTENT stem cells. Why are they called totipotent? (wait for answers) Because one red cell can potentially make all necessary tissues for development. CLICK! During In Vitro Fertilization, can parents choose whether their baby is going to be a boy or a girl? (wait) Yes, there is a widely-practiced procedure called pre-implantation genetic diagnosis, where one cell is removed from the 8-cell embryo and its DNA is examined. What might you look for when trying to identify the embryo’s sex? (wait) If there’s an X and Y chromosome it’s a boy and if there are two X’s it’s a girl. The parents can decide whether to implant it. Also parents with a genetic disease might want to see if their baby has any identifiable genetic disorders and decide whether to implant based on this information. Pre-implantation genetic diagnosis doesn’t destroy the embryo. Scientists are attempting to adapt this pre-implantation genetic diagnosis procedure and use it to create a stem cell line from one single TOTIPOTENT cell, without destroying the embryo. The embryonic stem cells inside the blastocyst, here in purple, can generate every cell in the body except placenta and extra-embryonic tissues. These are called CLICK! PLURIPOTENT stem cells…why? (wait for answers) Because they can differentiate into all the 200+ cell types in the body, but they do not form the placenta. CLICK! Pluripotent stem cells can be isolated and grown in culture, or left to develop into more specialized cells in the body. CLICK! Adult stem cells or tissue-specific stem cells have restricted lineages. Adult stem cells show up when the three distinct layers form in the 14-day-old embryo, and are present in the fetus, baby, child, and so forth. Adult just means they’ve gone further down their lineage pathway than the initial stem cells in the embryo. They are called CLICK! MULTIPOTENT stem cells because they will only become mature cells from the tissue in which they reside. Adult stem cells are present throughout your life and replace fully mature CLICK!, yet damaged and dying cells. So to review (if time): TOTIPOTENT stem cells come from embryos that are less than 3 days old. These cells can make the TOTAL human being because they can form the placenta and all other tissues. PLURIPOTENT stem cells come from embryos that are 5-14 days old. Embryos and fetuses that are older than 14 days DO NOT contain pluripotent cells. These cells can form every cell type in the body but not the placenta. MULTIPOTENT stem cells are also called adult stem cells and these appear in the 14 day old embryo and beyond. At this point these stem cells will continue down certain lineages and CANNOT naturally turn back into pluripotent cells or switch lineages.
  • #36: Stem cells can be classified into three broad categories, based on their ability to differentiate. Totipotent stem cells are found only in early embryos. Each cell can form a complete organism (e.g., identical twins). Pluripotent stem cells exist in the undifferentiated inner cell mass of the blastocyst and can form any of the over 200 different cell types found in the body. Multipotent stem cells are derived from fetal tissue, cord blood and adult stem cells. Although their ability to differentiate is more limited than pluripotent stem cells, they already have a track record of success in cell-based therapies. Here is a current list of the sources of stem cells: Embryonic stem cells - are harvested from the inner cell mass of the blastocyst seven to ten days after fertilization. Fetal stem cells - are taken from the germline tissues that will make up the gonads of aborted fetuses. Umbilical cord stem cells - Umbilical cord blood contains stem cells similar to those found in bone marrow. Placenta derived stem cells - up to ten times as many stem cells can be harvested from a placenta as from cord blood. Adult stem cells - Many adult tissues contain stem cells that can be isolated.