Structure of cell and its components
- 1. Structure of a basic cell, special features of prokaryotes, plant and animal cells
- 2. • All Living Organisms are Made Up of functional basic Unit of life Called Cells • There Are 2 Basic Types of Cells: Prokaryotic and Eukaryotic – Prokaryotic cells are more primitive, small and without nucleus and organelles • Bacteria, blue-green algae – Eukaryotic cells are more advanced, larger, contain nucleus and organelles • All higher species: animals, plants, fungi, protozoa Cells
- 3. Prokaryotic Cells • Small Prokaryotic Cells are Simple but Fast – Size: bacteria 1-10 micron dia. – Small cells such as bacteria divide fast (~ 20 min) – Have no nucleus: DNA less protected, mutates faster – Prokaryotic cells consist of a single closed compartment that is surrounded by the plasma membrane, – has a relatively simple internal organization
- 5. Eukaryotic Cells • Large Eukaryotic Cells are Slow but Versatile – Size: typically 10-100 micron dia.; volumes typically 1000 times larger than prokaryotes – Have nucleus: DNA better protected, slow mutation rate – Organelles allow many activities to take place within the same cell
- 6. • Eukaryotes comprise • all members of the plant and animal • and the fungal kingdoms, which exist in both multicellular forms and and unicellular forms (yeasts), • primitive; zoan, animal), which are exclusively unicellular.
- 7. similarities between prokaryote and eukaryote • The major similarities between the two types of cells (prokaryote and eukaryote) are: • 1.They both have DNA as their genetic material. 2.They are both membrane bound. 3.They both have ribosomes. 4.They have similar basic metabolism 5.They are both amazingly diverse in forms.
- 8. Difference between prokaryotes and eukaryotes • The major and extremely significant difference between prokaryotes and eukaryotes is that eukaryotes have a nucleus and membrane- bound organelles, while prokaryotes do not. • The DNA of prokaryotes floats freely around the cell; the DNA of eukaryotes is held within its nucleus.
- 9. The defining characteristic of eukaryotic cells is nucleus which is bounded by a double membrane. The outer nuclear membrane is continuous with the rough endoplasmic reticulum, a factory for assembling proteins. Golgi vesicles process and modify proteins, mitochondria generate energy, lysosomes digest cell materials to recycle them, peroxisomes process molecules using oxygen, and secretory vesicles carry cell materials to the surface to release them.
- 10. Differences between prokaryotes and eukaryotes • Additional obvious differences between prokaryotes and eukaryotes include: • Size Eukaryotic cells are, on average, ten times the size of prokaryotic cells. • Genomic composition and length The DNA of eukaryotes is much more complex (in both size and organisation) and than the DNA of prokaryotes. • Cell Wall Prokaryotes have a cell wall composed of peptidoglycan, a single large polymer of amino acids and sugar. Many types of eukaryotic cells also have cell walls, but none made of peptidoglycan.
- 13. Structure of Eukaryotic cells
- 14. Basic cell structures Plasma Membrane—A Cell's Protective Coat Cytoskeleton—A Cell's Scaffold Cytoplasm—A Cell's Inner Space Genetic Material—DNA and RNA Organelles Nucleus—A Cell's Center Ribosome—The Protein Production Machine Mitochondria and Chloroplasts—The Power Generators Endoplasmic Reticulum and the Golgi Apparatus— Macromolecule Managers Lysosomes and Peroxisomes—The Cellular Digestive System
- 15. Cytosol • Cytosol is the liquid matrix of the cell- mostly water (cytosol + organelles except nucleus = cytoplasm) • Contains salts, dissolved molecules, enzymes, etc. • Glycolysis (energy metabolism: anaerobic) takes place in cytoplasm
- 16. Organelles • The largest organelle in a eukaryotic cell is generally the nucleus, which houses most of the cellular DNA. • In addition to the nucleus, several other organelles are present innearly all eukaryotic cells: • the mitochondria, • the rough and smooth endoplasmic reticula, • Golgi vesicles, peroxisomes, • Animal cells, but not plant cells, contain lysosomes, • Chloroplasts (plants) • Both plant cells and some single-celled eukaryotes contain one or more vacuoles,
- 17. Cell Membrane • The Cell Membrane Separates the Cytoplasm From the External World – Cell membrane is made of phospholipid & protein – Barrier to movement of things in and out of the cell- hydrophobic molecules pass through it more readily than hydrophilic ones – Specialized transport mechanisms: selectively move materials across the membrane – Supported on inside by protein filaments (cytoskeleton)
- 18. Nucleus The nucleus, the largest organelle in animal cells, is surrounded by two membranes The inner nuclear membrane defines the nucleus itself. The outer nuclear membrane is continuous with the rough endoplasmic reticulum, and the space between the inner and outer nuclear membranes is continuous with the lumen of the rough endoplasmic reticulum The two nuclear membranes appear to fuse at nuclear pores, the ringlike complexes composed of specific membrane proteins through which material moves between the nucleus and the cytosol. Nucleus is filled with chromatin composed of DNA and proteins; in dividing cells is site of mRNA and tRNA synthesis.
- 19. Nucleolus Is the dense region within the nucleus and it is a subcompartment of the nucleus that is not bounded by a phospholipid membrane. Most of the cell’s ribosomal RNA is synthesized in the nucleolus
- 20. Mitochondria Principal sites of ATP production. It is bound by two membranes The outer membrane, composed of about half lipid and half protein, contains porins that render the membrane permeable to molecules having molecular weights as high as 10 kDa The inner membrane, which is much less permeable, is about 20 percent lipid and 80 percent protein The surface area of the inner membrane is greatly increased by a large number of infoldings, or cristae, that protrude into the matrix, or central Space.
- 21. The complete aerobic degradation of glucose to CO2 and H2O is coupled to the synthesis of 30 molecules of ATP. 2 molecules of ATP at cytoplasm and 28 molecules at Mitochodria. Thus Mitochodria are called “power plants” of the cell.
- 22. chloroplasts in the cells of plants and green algae contains an extensive internal system of interconnected membrane- bound sacs called thylakoids. The thylakoid membranes contain green pigments (chlorophylls) and other pigments that absorb light. Thylakoids often form stacks called grana Tube like structure connecting thylakoid from granum to granum- stroma lamellae.
- 23. endoplasmic reticulum extensive network of closed, flattened membrane-bounded sacs and they are fused to nuclear membrane. The smooth endoplasmic reticulum is smooth because it lacks ribosomes. Rough endoplasmic reticulum is studded with ribosomes. smooth endoplasmic reticulum
- 24. Rough endoplasmic reticulum (ER) functions in the synthesis, processing, and sorting of secreted proteins, lysosomal proteins, and certain membrane endoplasmic reticulum Smooth endoplasmic reticulum (ER) synthesizes lipids and detoxifies certain hydrophobic compounds (pesticides and carcinogens).
- 25. Golgi apparatus Golgi apparatus is a series of flattened membrane vesicles or sacs (cisternae) The stack of Golgi cisternae has three defined regions— the cis, the medial, and the trans. Transport vesicles from the rough ER fuse with the cis region of the Golgi complex, where they deposit their protein contents. these proteins then progress from the cis to the medial to the trans region. After proteins are modified in the Golgi complex, they are transported out of the complex by a second set of vesicles, which seem to bud from the trans side of the Golgi complex.
- 26. Plant Vacuoles Most plant cells contain at least one membrane bound vacuole. The number and size of vacuoles depend on both the type of cell and its stage of development; single vacuole may occupy as much as 80 percent of a mature plant cell Vacuoles store water, ions, and nutrients (e.g., sucrose, amino acids)
- 27. Lysosomes • Lysosomes Digest Materials within the Cell – Small vesicles surrounded by membranes – Lysosomes contain digestive enzymes that degrade worn-out intracellular organelles, as well as macromolecules (CHO, proteins and lipids) and particles (bacteria) taken in from outside the cell by endocytosis. – Involved in apoptosis (programmed cell death) – Lysozomes are acidic organelles and require an acid pH inside (~4.5)
- 28. Peroxisomes (degrades Fatty acids and toxic compounds) • Peroxisomes Deal with Reactive Oxygen Molecules Such as Peroxides – Contain the enzyme, catalase – Important in fat metabolism, oxidation of FA yields acetyl groups which are used in synthesis of cholesterol and other metabolites. – Various toxic molecules are degraded by peroxisomes expecially in kidney and liver cells
- 29. • The Cytoskeleton Determines the Shape of the Cell • Protein filaments that compose the cytoskeleton of the cell – Give the cell shape – Are used to transport structures within the cell (i.e., chromosomes in mitosis) – Are involved in movement of the whole cell • Three basic types of filaments: – Microfilaments (made of actin, 8-9 nm dia), and have a twisted two- stranded structure – Intermediate filaments (made of several proteins, 10-12 nm dia) – Microtubules (made of tubulin, 25 nm dia), hallow tube like structure Cytoskeleton
- 30. Microfilaments and Membrane-Binding Proteins Form a Skeleton Underlying the Plasma Membrane Intermediate Filaments Support the Nuclear Membrane and Help Connect Cells into Tissues Microtubules Radiate from Centrosomes and Organize Certain Subcellular Structures
- 33. Plant cells Animal cells Relatively larger in size Relatively smaller in size Cell walls almost present No cell walls present structure is very rigid. more flexible membranes Nucleus near cell wall Nucleus at the center Plastids occur in cytoplasm No plastids are found Lysosomes not usually evident Lysosomes occur in cytoplasm Centrioles present only in cells of lower plant forms Centrioles always present Large vacuoles filled with cell sap Vacuoles, if present, are small and contractile or temporary vesicles Plant cells have glyoxysomes Animal cells do not. Starch as food storage Stores glycogen in the cytoplasm Structural differences between Plant and Animal Cells