UNIT 1 2022.ppt
- 2. UNIT I Introduction Cell structure and function Genetic information, and protein structure Cell metabolism Homoeostasis Cell growth, reproduction, and differentiation
- 4. Concept of evolution • Jean Baptistae Lamarak (1801) • Charles darwin (1859) 4
- 5. 5 Methods of Science • The scientific method refers to the model for research developed by Francis Bacon (1561–1626). This model involves the following sequence: 1. Identifying the problem 2. Collecting data within the problem area (by observations, measurements, etc.) 3. Sifting the data for correlations, meaningful connections, and regularities 4. Formulating a hypothesis (a generalization), which is an educated guess that explains the existing data and suggests further avenues of investigation 5. Testing the hypothesis rigorously by gathering new data 6. Confirming, modifying, or rejecting the hypothesis in light of the new findings
- 6. 6 Living Organism • A living organism may be defined as a complex unit of physicochemical materials that is capable of self-regulation, metabolism, and reproduction. • Furthermore, a living organism demonstrates the ability to interact with its environment, grow, move, and adapt.
- 7. 7 What Are the Main Characteristics of organisms? 1. Made of CELLS 2. Require ENERGY (food) 3. REPRODUCE (species) 4. Maintain HOMEOSTASIS 5. ORGANIZED 6. RESPOND to environment 7. GROW and DEVELOP 8. EXCHANGE materials with surroundings (water, wastes, gases)
- 8. 8 Five Kingdoms and their chief characteristics • Unicellular organisms that lack a nucleus and many of the specialized cell parts, called organelles. Such organisms are said to be prokaryotic (pro =‘‘before’’; karyotic =‘‘kernel,’’ ‘‘nucleus’’) and consist of bacteria. • All of the other kingdoms consist of eukaryotic (eu = ‘‘true’’) organisms, which have cells that contain a nucleus and a fuller repertory of organelles.
- 9. Cell-basic unit of life • Smallest living form • Inside the cell some structure transport • Metabolize • Respire • Reproduce (Meiosis) • Multiply (Mitosis) • Energy producing • Keep information 9
- 10. 10 Prokaryotes • Nucleoid region (center) contains the DNA • Surrounded by cell membrane & cell wall (peptidoglycan) • Contain ribosomes (no membrane) in their cytoplasm to make proteins
- 11. 11 Eukaryotes • Cells that HAVE a nucleus and membrane-bound organelles • Includes protists, fungi, plants, and animals • More complex type of cells
- 12. 12 Cells and Cell Theory • In 1665, Robert Hooke used a microscope to examine a thin slice of cork (dead plant cell walls). Hooke called them “CELLS” because they looked like the small rooms that monks lived in called “Cells” • In 1673, Leeuwenhoek (a Dutch microscope maker), was first to view organism (living things) Cell Theory • In 1838, a German botanist named Matthias Schleiden concluded that all plants were made of cells • In 1839, a German zoologist named Theodore Schwann concluded that all animals were made of cells
- 13. 13 Beginning of the Cell Theory • In 1855, a German medical doctor named Rudolph Virchow observed, under the microscope, cells dividing • He reasoned that all cells come from other pre-existing cells by cell division
- 14. 14 CELL THEORY • All living things are made of cells • Cells are the basic unit of structure and function in an organism (basic unit of life) • Cells come from the reproduction of existing cells (cell division)
- 15. 15 Cell Structure and Function
- 16. 16 Organelles • Very small (Microscopic) • Perform various functions for a cell • Found in the cytoplasm • May or may not be membrane-bound Plant Cell
- 17. 17 Cell or Plasma Membrane Outside of cell Inside of cell (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains • Composed of double layer of phospholipids and proteins • Surrounds outside of ALL cells • Controls what enters or leaves the cell • Living layer
- 18. 18 • Jelly-like substance enclosed by cell membrane • Provides a medium for chemical reactions to take place • Contains organelles to carry out specific jobs • Found in ALL cells Cytoplasm of a Cell cytoplasm
- 19. 19 • Controls the normal activities of the cell • Contains the DNA in chromosomes • Bounded by a nuclear envelope (membrane) with pores • Usually the largest organelle • Each cell has fixed number of chromosomes that carry genes • Genes control cell characteristics The Control Organelle - Nucleus
- 20. 20 Nucleolus • Inside nucleus • Cell may have 1 to 3 nucleoli • Disappears when cell divides • Makes ribosomes that make proteins
- 21. 21 Cytoskeleton • Helps cell maintain cell shape • Also help move organelles around • Made of proteins • Microfilaments are threadlike & made of ACTIN • Microtubules are tube-like and made of TUBULIN Cytoskeleton Microtubules Microfilaments
- 22. 22 Centrioles • Found only in animal cells • Paired structures near nucleus • Made of bundle of microtubules • Appear during cell division forming mitotic spindle • Help to pull chromosome pairs apart to opposite ends of the cell
- 23. 23 Mitochondrion (plural = mitochondria) • “Powerhouse” of the cell • Generate cellular energy (ATP) • More active cells like muscle cells have MORE mitochondria • Both plants & animal cells have mitochondria • Site of CELLULAR RESPIRATION (burning glucose)
- 24. 24 MITOCHONDRIA • Surrounded by a DOUBLE membrane • Has its own DNA – Mitochondria come from cytoplasm in the egg cell during fertilization – Therefore you inherit your mitochondria from your mother! • Folded inner membrane called CRISTAE (increases surface area for more chemical reactions) • Interior called MATRIX
- 25. 25 Endoplasmic Reticulum - ER Two kinds of ER ---ROUGH & SMOOTH • Network of hollow membrane tubules • Connects to nuclear envelope & cell membrane • Functions in Synthesis of cell products & Transport
- 26. 26 Rough Endoplasmic Reticulum (Rough ER) • Has ribosomes on its surface • Makes membrane proteins and proteins for EXPORT out of cell • Proteins are made by ribosomes on ER surface • They are then threaded into the interior of the Rough ER to be modified and transported
- 27. 27 Smooth Endoplasmic Reticulum • Smooth ER lacks ribosomes on its surface • Is attached to the ends of rough ER • Makes cell products that are USED INSIDE the cell • Makes membrane lipids (steroids) • Regulates calcium (muscle cells) • Destroys toxic substances (Liver) Includes nuclear membrane connected to ER connected to cell membrane (transport)
- 28. 28 Ribosomes • Made of PROTEINS and rRNA • “Protein factories” for cell • Join amino acids to make proteins • Process called protein synthesis • Can be attached to Rough ER OR Be free (unattached) in the cytoplasm
- 29. 29 Golgi Bodies • Stacks of flattened sacs • Have a shipping side (trans face) and receiving side (cis face) • Receive proteins made by ER • Transport vesicles with modified proteins pinch off the ends Transport vesicle CIS TRANS
- 30. 30 Golgi Bodies Look like a stack of pancakes Modify, sort, & package molecules from ER for storage OR transport out of cell
- 31. 31 Lysosomes • Contain digestive enzymes • Break down food, bacteria, and worn out cell parts for cells • Programmed for cell death (AUTOLYSIS) • Lyse (break open) & release enzymes to break down & recycle cell parts)
- 32. 32 Lysosome Digestion • Cells take in food by phagocytosis • Lysosomes digest the food & get rid of wastes
- 33. 33 Vacuoles • Fluid filled sacks for storage • Small or absent in animal cells • Plant cells have a large Central Vacuole • No vacuoles in bacterial cells • In plants, they store Cell Sap • Includes storage of sugars, proteins, minerals, lipids, wastes, salts, water, and enzymes
- 34. 34 Chloroplasts • Found only in producers (organisms containing chlorophyll) • Use energy from sunlight to make own food (glucose) • Energy from sun stored in the Chemical Bonds of Sugars Surrounded by DOUBLE membrane Outer membrane smooth Inner membrane modified into sacs called Thylakoids Thylakoids in stacks called Grana & interconnected Stroma – gel like material surrounding thylakoids
- 35. 35 Chloroplasts • Contains its own DNA • Contains enzymes & pigments for Photosynthesis • Never in animal or bacterial cells • Photosynthesis – food making process
- 36. 36 Genetic information and protein structure
- 37. Genetic information • Genetic information is in the chromosomes found in the nucleus. – necessary for reproduction of species and therefore, its propagation on earth. – It is coded along the length of a polymeric molecule composed of four types of monomeric units. This polymeric molecule is deoxyribonucleic acid (DNA). – It is the chemical basis of heredity which is organised into genes, the fundamental units of genetic information. Genes control the synthesis of various types of ribonucleic acid (RNA). 37
- 38. • Nucleic acid is a polynucleotide consisting of nucleotides as the repeating subunits. Each nucleotide is made up of three components are, (i) pentosugar, (ii) nitrogenous base and (iii) phosphate. • This linkages repeated many times to build up large structures containing hundreds to millions of nucleotides within a single giant molecule. – Pentosugar: It is a type of cyclic 5 carbon sugar, which connects two phosphate groups The type of sugar molecule in DNA is deoxyribose, where as in RNA is ribose. – Nitrogenous base: Nucleic acids contains 5 major heterocyclic bases, adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U). First four bases are common in DNA, in case of RNA thymine is replaced with uracil – Phosphate: A phosphate group is attached to the 5’ carbon of the sugar by a phosphodiester linkage. This phosphate group is solely responsible for the strong negative charge of the nucleic acids. 38
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- 40. 40 Proteins • Proteins are polymers (macromolecules) made of monomers called amino acids • All proteins are made of 20 different amino acids linked in different orders • Proteins are used to build cells, act as hormones & enzymes, and do much of the work in a cell Arginine
- 41. 41 Protein Functions in the Body • There are many different proteins in your body, and they perform different functions. Proteins functions include: – Contributing to enzyme activity that promotes chemical reactions in the body – Signaling cells what to do and when to do it – Transporting substances around the body – Keeping fluids and pH balanced in the body – Serving as building blocks for hormone production – Helping blood clot – Promoting antibody activity that controls immune and allergy functions – Serving as structural components that give our body parts their shapes Storage Structural Transport
- 42. 42 Primary Protein Structure The primary structure is the specific sequence of amino acids in a protein called polypeptide •Amino acids have in common a central carbon C atom to which are attached a hydrogen atom (H), amino group (NH2), and carboxyl group (COOH) •Joined by peptide bond where carboxyl group of one amino acid condenses with an amino group of next to eliminate water
- 43. 43 Secondary structure The conformation of the polypeptide by twisting or folding is referred to as secondary structure. Alpha helix •Residues per turn with a hydrogen bond between C=O of nth amino acid and NH of residue n+4th amino acid •In globular proteins, alpha helix vary considerably in length ranging from four or five amino acids to every forty residues •The average length is around ten residues corresponding to three turns •The rise per residue of an alpha helix is 1.5A along the helical axis which corresponds to about 15A from one end to the other of an average alpha helix •The width of the alpha helix is around 4A. •Almost all observed alpha helix is right-handed helix in a protein •Alanine, glutamine leucine, and methionine are strong helix-forming amino acids •Proline, Glycine, Tyrosine, and serine occur in the helix rarely. Beta sheet •Build up from different regions of the polypeptide chain •Beta strands are 5 to 10 aa residues and interact in parallel or antiparallel to form pleated sheets. •Beta sheets can also combine into mixed beta sheets with some beta strands pairs parrel and some anti-parallell.
- 44. 44 Tertiary structure • Alpha helix and beta sheets fold up compact into super secondary structures or domains called tertiary structure • One important tertiary interaction is the di sulphide bond. Di sulphide bond is formed between the sulphur atoms of cysteine residues. • Disulphide provides mechanical strength to the protein and also determines the chemical properties by stabilizing the correct active conformation. • Major stabilizing factor in the tertiary structure of the protein is • Hydrophobic interaction • Polar and non polar amino amino acid interaction • Salt bridges between oppositely charged amino acids. • Hydrogen bonding in the interior of the protein Quaternary structure • Protein in its active form exists as an aggregate of more than one folded polypeptide. The macromolecular structure so build-up is called the quaternary structure • Non covalent interactions and disulphide bridges are responsible for quaternary structure
- 45. 45 Protein Structures or CONFORMATIONS Hydrogen bond Pleated sheet Amino acid (a) Primary structure Hydrogen bond Alpha helix (b) Secondary structure Polypeptide (single subunit) (c) Tertiary structure (d) Quaternary structure
- 47. 47 Cell metabolism • Energy is the ability to do work. • Living things need to acquire energy; this is a characteristic of life. • Cells use acquired energy to: – Maintain their organization • Carry out reactions that allow cells to develop, grow, and reproduce
- 48. 48 ATP: Energy for Cells • ATP (adenosine triphosphate) is the energy currency of cells. • ATP is constantly regenerated from ADP (adenosine diphosphate) after energy is expended by the cell. • Use of ATP by the cell has advantages: • 1) It can be used in many types of reactions. • 2) When ATP → ADP + P, energy released is sufficient for cellular needs and little energy is wasted.
- 49. 49 Function of ATP • Cells make use of ATP for: • Chemical work – ATP supplies energy to synthesize macromolecules, and therefore the organism • Transport work – ATP supplies energy needed to pump substances across the plasma membrane • Mechanical work – ATP supplies energy for cellular movements
- 50. 50 Two types of metabolic reactions Anabolism • larger molecules are made • requires energy Catabolism • larger molecules are broken down • releases energy Hydrolysis • a catabolic process • used to decompose carbohydrates, lipids, and proteins • water is used • reverse of dehydration synthesis Dehydration synthesis • type of anabolic process • used to make polysaccharides, triglycerides, and proteins • produces water
- 51. Carbohydrate metabolism • Carbohydrate metabolism is a fundamental biochemical process that ensures a constant senergy supplyto living cells. • During digestion, carbohydrates are broken down into simple, soluble sugar glucose that can be transported across the intestinal wall into the circulatory system to be transported throughout the body and absorbed into the cell • Once the absorbed glucose is transported to the tissues, cellular respiration begins • on glycolysis, a process where glucose is oxidized, releasing the energy stored in its bonds to produce ATP. The last step in glycolysis produces the product pyruvate • The pyruvate molecules generated during glycolysis are transported across the mitochondrial membrane into the inner mitochondrial matrix, where they are metabolized by enzymes in a pathway called the Krebs cycle • During the Krebs cycle, high-energy molecules, including ATP, NADH, and FADH2, are created. NADH and FADH2 then pass electrons through the electron transport chain in the mitochondria to generate more ATP molecules • important pathways in carbohydrate metabolism – pentose phosphate pathway conversion of hexose sugars into pentoses, – glycogenesis -conversion of excess glucose into glycogen, stimulated by insulin, – glycogenolysis conversion of glycogen polymers into glucose, stimulated by glucagon – gluconeogenesis de novo glucose synthesis 51
- 52. Amino acid Metabolism Amino acid biosynthesis • Amino acids derive mainly thorugh intermediate of glycolysis and citric acid cycle or pentose phosphate pathway. Amino acid Catbolism • Removal or exchange of functional groups • Involves transamination, deamination, and decarboxylation • Releases excess nitrogen in the form of ammonium (NH4+), which then enters the urea cycle, is converted into urea, and excreted through the urine • Catabolism of the remaining carbon skeleton • In general, all 20 AAs can be broken down into 1 of 6 intermediates: pyruvate, acetyl-CoA, oxaloacetate, alpha- ketoglutarate, succinyl-CoA, and fumarate. • Ketogenic AAs metabolize to acetyl-CoA, later used in the citric acid cycle, ketogenesis, or fatty acid synthesis. • Glucogenic AAs are converted into glucose through gluconeogenesis. • Some AAs are both glucogenic and ketogenic. 52
- 53. • Fatty Acid Metabolism 53
- 55. Metabolic relationships among the major human organs: brain, muscle, heart, adipose tissue, and liver Organ Energy Reservoir Preferred Substrate Energy Sources Exported Brain None Glucose (ketone bodies during starvation) None Skeletal muscle (resting) Glycogen Fatty acids None Skeletal muscle (prolonged exercise) None Glucose Lactate Heart muscle Glycogen Fatty acids None Adipose tissue Triacylglycer ol Fatty acids Fatty acids, glycerol Liver Glycogen, tri acylglycerol Amino acids, glucose, fat ty acids Fatty acids,glucos e, ketone bodies
- 56. 56 Homoeostasis
- 57. 57 Homoeostasis Definition : Maintenance of the relative stability of the physical and chemical aspects of the internal environment within a range compatible with cellular function. Maintaining a constant internal environment with all that the cells need to survive (O2, glucose, minerals, ions, and waste removal) is necessary for individual cells. The processes by which the body regulates its internal environment are referred to as homeostasis. Components : 1) sensor 2) afferent pathway 3) integration center or comparator 4) efferent pathway 5) effector organ(s) • Physiological control systems are the nervous system, endocrine system, and immune system through feedback mechanisms.
- 58. • Nervous System • The nervous system maintains homeostasis by controlling and regulating the other parts of the body. – A deviation from a normal set point acts as a stimulus to a receptor, which sends nerve impulses to a regulating center in the brain. The brain directs an effector to act in such a way that an adaptive response takes place. • The nervous system has two major portions: the central nervous system and the peripheral nervous system. • Regulating centers are located in the central nervous system, consisting of the brain and spinal cord. – The hypothalamus is a portion of the brain particularly concerned with homeostasis; it influences the action of the medulla oblongata, a lower part of the brain, the autonomic nervous system, and the pituitary gland. • The peripheral nervous system consists of the spinal nerves. The autonomic nervous system is a part of peripheral nervous system and contains motor neurons that control internal organs. It has two divisions, the sympathetic and parasympathetic systems. 58 Intrinsic homeostatic systems
- 59. • Endocrine System • The endocrine system consists of glands which secrete special compounds called hormones into the bloodstream. • Each hormone has an effect on one or more target tissues. In this way the endocrine system regulates the metabolism and development of most body cells and body systems. • For e.g. the endocrine system has sex hormones that can activate sebaceous glands, development of mammary glands, alter dermal blood flow, and release lipids from adipocytes etc besides governing reproduction. • In the muscular system, hormones adjust muscle metabolism, energy production, and growth. • In the nervous system, hormones affect neural metabolism, regulate fluid/electrolyte balance and help with reproductive hormones that influence CNS (central nervous system), development and behaviours. • In the cardiovascular system, hormones regulate heart rate and blood pressure. • Hormones also have anti-inflammatory effects and control the lymphatic system. 59
- 60. 60 • Negative feedback : a control system that causes the value of a physiological measurement to change in the direction opposite to the initial deviation from set point. • Positive feedback : a control system that causes the value of a physiological measurement to change in the same direction as the initial deviation from set point. Positive feedback hypothalamus (control center) output level (contraction) increases stretch receptors in cervix (sensor) uterine muscles (effector) oxytocin release (signal to turn on effector) uterus nerve signal to control center nerve endings (sensor) Negative feedback hypothalamus (control center) heat output (shivering) decreases Skeletal muscles (effector) nerve signal (temperature) to control center heat output (shivering) increases nerve signal to turn off effector nerve signal to turn on effector
- 61. 61 Cell growth, reproduction, and differentiation
- 62. Bacteria Reproduction Asexual, through binary fission No true sexual reproduction, since neither mitosis nor meiosis exist in prokaryotes Horizontal transfer of genetic material Transformation Transduction Conjugation Uptake of genetic material from the environment Transfer of genetic material between prokaryotes by viruses Direct transfer of genetic material from one prokaryote to another DNA cell wall
- 63. 63 Binary fission Daughter cells are identical copies (1) (2) (3) (4) (5) (6) Chromosome Plasma membrane Neither mitosis nor meiosis occurs in prokaryotes
- 64. 64 The Cell Cycle • Mitosis and meiosis are single steps in cell cycle • G1, S, G2, and M phases – Cells not in process of dividing are in G0 phase – Chromosomes are duplicated in preparation for the next round of division during interphase
- 65. 65 Control of the Cell Cycle • The stimuli for entering the cell cycle is in the form of growth factors and cytokines that are capable of inducing mitotic divisions • The cell cycle is highly regulated – Proteins whose concentrations rise & fall in a controlled manner • Cyclin and cyclin-dependent kinases (cdk) • p53 and pRb • Inhibitors of cdk • Internal checkpoints & guardians monitor cell health • Errors in this process can lead to uncontrollable growth and cancer
- 66. 66 • Cell cycle control is focused at 3 places: • G1 checkpoint • G2 checkpoint • M checkpoint – Before S phase (DNA synthesis) – At transition between G2 and M phase Control of the Cell Cycle
- 67. 67 Mitosis •Four phases –1. Prophase: chromosomes condense, spindle apparatus forms, nuclear envelope breaks down –2. Metaphase: chromosomes line up at equator of cell –3. Anaphase: sister chromatids separate –4. Telophase: new nuclear envelopes form, chromosomes unwind nuclear envelope pair of homologous, duplicated chromosomes sister chromatids of one duplicated homologue
- 68. 68 (d) Anaphase: Sister chromatids have separated, and one set has moved toward each pole. (a) Interphase in a seed cell: The chromosomes (blue) are in the thin, extended state and appear as a mass in the center of the cell. The spindle microtubules (red) extend outward from the nucleus to all parts of the cell. (b) Late prophase: The chromosomes (blue) have condensed and attached to the spindle microtubules (red). (e) Telophase: The chromosomes have gathered into two clusters, one at the site of each future nucleus. (c) Metaphase: The chromosomes have moved to the equator of the cell. (f) Resumption of interphase: The chromosomes are relaxing again into their extended state. The spindle microtubules are disappearing, and the microtubules of the two daughter cells are rearranging into the interphase pattern.
- 69. 69 Parent Cell Chromosomes have been replicated Daughter Cells Each cell has the same genetic makeup as the parent cell Mitosis Each new nucleus is genetically identical to the parent nucleus
- 70. 70 Meiosis Characteristics of meiosis • 1. Occurs in sex cells (germ cells) and produces gametes • 2. A reductional division resulting in haploid cells • 3. Involves two sequential divisions resulting in four cells • 4. Produces cells that are genetically different because of genetic recombination (crossing-over).
- 71. 71 Parent Cell (2n) 1st division 2nd division Daughter Cells (1n) each chromosome has 2 chromatids Gamete Cells (1n) Meiosis
- 72. 72 Process of Meiosis Meiosis begins with a parent cell that is diploid results in four daughter cells that are haploid Meiosis I Prophase I. • chromatin condenses to form chromosomes and they remain joined at a central point called the centromere. • A large structure called the meiotic spindle also forms from long proteins called microtubules on each side, or pole, of the cell. Metaphase I • The pairs of homologous chromosome form tetrads. Within the tetrad, any pair of chromatid arms can overlap and fuse in a process called crossing-over or recombination. • The homologous pairs of chromosomes align on either side of the equatorial plate. Anaphase I The spindle fibers contract and pull the homologous pairs, each with two chromatids, away from each other and toward each pole of the cell. Telophase I The chromosomes are enclosed in nuclei. The cell now undergoes a process called cytokinesis that divides the cytoplasm of the original cell into two daughter cells. Each daughter cell is haploid and has only one set of chromosomes, or half the total number of chromosomes of the original cell.
- 73. 73 Meiosis II Mitotic division of each of the haploid cells produced in meiosis I. Prophase II • The chromosomes condense, and a new set of spindle fibers forms. The chromosomes begin moving toward the equator of the cell. Metaphase II • The centromeres of the paired chromatids align along the equatorial plate in both cells. Anaphase II • The chromosomes separate at the centromeres. The spindle fibers pull the separated chromosomes toward each pole of the cell. Telophase II • The chromosomes are enclosed in nuclear membranes. Cytokinesis follows, dividing the cytoplasm of the two cells. At the conclusion of meiosis, there are four haploid daughter cells
- 74. 74 Meiosis produces gametes for sexual reproduction • Multiplies number of cells but also reduces chromosome number in each daughter cell to exactly half the number present before meiosis • Daughter cells get 1 member of each homologous pair, i.e. 1 allele for each gene • Mitosis produces 2 daughter cells • Meiosis produces 4 daughter cells • All body cells in humans are diploid, except gametes • Cells with 1 member of each homologous pair are haploid
- 75. 75 Cell Differentiation • The process of altering the pattern of gene expression and thus becoming a cell of a particular type is called cell differentiation. • Presence of chemicals (or other influences) starts altering the decisions as to which genes will be turned on or off. • The zygote is a totipotent cell - its daughter cells can become any cell type. As the development proceeds, some of the cells become pluripotent - they can become many, but not all cell types. • Later on, the specificity narrows down further and a particular stem cell can turn into only a very limited number of cell types, e.g., a few types of blood cells, but not bone or brain cells or anything else. That is why embryonic stem cell research is much more promising than the adult stem cell research.
- 76. Differentiation of different tissues and organs 76