Cell Biology. a review! Cell Theory & Cell Structures

Transcription

1 Cell Biology Cell Theory & a review! Cell Structures Cell Theory refers to the idea that cells are the basic unit of structure and function of all living things. Cells are either prokaryotic or eukaryotic 1

2 Prokaryotic (before nucleus ) Lacks membranebound nucleus Single, usually circular genophore of DNA Lacks membrane bound organelles Structurally Simple Metabolically diverse Adapted to most types of environments Eukaryotic (true nucleus ) Have a membranebound nucleus Possess membrane bound organelles Structurally complex May have a cell wall 2

3 Eukaryotic Cells Cell Theory All organisms are composed of one or more cells Either unicellular or multicellular Unicellular - Amoeba Multicellular - Polar Bear 3

4 Cell Theory All cells come from pre-exisiting cells Via binary fission, mitosis, or meiosis Cell Size Surface Area / Volume Ratio Amount of surface area affects the ability to get materials in and out of a cell A cells increase in volume, the proportionate amount of surface area decreases 4

5 eukaryotic A basic cell consists of ^! Cytoplasm - contains organelles (functional units of the cell) - cytoskeleton Nucleus - contains DNA Cell Membrane - protects - regulates what enters/exits Cell Structures (a brief overview) 5

6 The Nucleus - the boss Site of DNA Genetic blueprint Provides instructions that guide cell s life processes Nuclear Envelope Protective double membrane Regulatory body, perforated with pores Continuous with the ER Nucleoplasm Nuclear fluid Rich in chromatin Form chromosomes during cell division Site of mrna (transcription) and trna formation Nucleolus rrna synthesis Assembly of ribosomes Site of protein synthesis Receives instruction from nucleus 6

7 Ribosomes Site of protein synthesis (assembly of a.a. into protein) Two subunits (small and large) Consist of rrna and protein molecules Found on the ER (Rough ER) Polysomes - ribosomes that are clumped together, free floating in cytoplasm Also found in mitochondria and chloroplasts Polyribosomes Several ribosomes with a single mrna molecule Nuclear Envelope - nuclear pores 7

8 Endomembrane System Inner membrane An internal highway within the cell Several interrelated membrane bound compartments found in eukaryotic cells Includes Rough ER, Smooth ER, Golgi Apparatus Endoplasmic Reticulum (ER) Present in all nucleated cells System of membrane-bound channels in cytoplasm that serve as routes of transport of materials between various parts of cytoplasm and nucleus = communication network in the cell 8

9 Rough ER Processing and modification of proteins (Translation) Lined with ribosomes Smooth ER NO ribosomes present Site of lipid (steroid) synthesis Storage and transport detoxification 9

10 Golgi Apparatus System of membranous sacs Collects, sorts, packages and distributes materials such as proteins and lipids Import/export center EXPORT Modifies proteins for export out of cell Forms secretory vesicles Exocytosis of proteins (eg. Insulin), lipids (eg. estrogen), waste products 10

11 IMPORT Forms the lysosome Lyse = to break aprt Some = body Digestion (hydrolytic) vesicle Lysosomes contain digestive enzymes: Acid Hydrolase Digestion of Incoming Nutrients Autodigestion (Recycling) 11

12 Vacuoles Membranous sacs that store substances (water, pigments, toxins) Helps maintain cell turgidity (shape) Energy-based Organelles Chloroplast Site of photosynthesis Mitochondria Site of cell respiration 12

13 Chloroplast A pigment (chlorophyll) filled plastid Chlorophyll is located in the thylakoid membranes Captures solar energy required for photosynthesis and the production of CHO s. In PLANTS, ALGAE & CYANOBACTERIA only Site of photosynthesis Structure: Double-membrane Stroma Grana Thylakoids Chloroplasts contain: Their own DNA Ribosomes Enzymes 13

14 Mitochondria Found in all eukaryotic cells (both plants & animals) Site of cellular respiration 14

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16 ATP (Adenosine Triphosphate) Energy Currency A nucleotide Does work High Energy Bond Sugar, Fat and Proteins can make ATP!!! Plasma Membrane & Cytoplasm All cells are surrounded by a cell membrane (aka plasma membrane, lipid bilayer, phospholipid bilayer) The material inside of a cell is the cytoplasm The plasma membrane is a semipermeable lipid bilayer that regulates what enters / exits a cell 16

17 Fluid Mosaic Model Contains a variety or mosaic of biological molecules (primarily proteins and lipids) Membrane is not solid but fluid with phospholipids and proteins that shift 17

18 Cell Wall Semi-rigid, permeable layer that helps maintain cell shape and chemical equillibrium In PLANT cells Composed of cellulose Cytoskeleton Maintains cell shape Assists in movement of cell and organelles Anchors organelles Three types of macromolecular fibers Actin Filaments Intermediate Filaments Microtubules 18

19 Actin Filaments Anchored to plasma membrane Allows intestinal microvilli to expand and contract Found in pseudopods allowing ameoboid movement Play role in cell division in animals Intermediate Filaments Intermediate in size between actin filaments and microtubules Function: Support nuclear envelope Cell-cell juntions (ie, those holding skin cells tightly together) 19

20 Microfilaments Two intertwined strands of actin Function Cell shape (cytoskeleton) Muscle contraction Cell motility Cell division Cytoplasmic streaming Microtubule Operation 20

21 Extensions of the Cell Membrane CILIA & FLAGELLA: Hairlike projections that aid in cell movement They are membrane-bound cylinders enclosing a matrix area The matrix consists of microtubules in a pattern 21

22 Centrioles Short cylinders with a pattern of microtubule triplets Help organize microtubules during animal cell division Maybe involved with microtubule formation and in the organization of cilia and flagella Flagella Sperm tail Motility (movement/swim) Cilia Hair-like Sweeping motion Eg. In oviducts sweep ovum/zygote toward uterus Eg. In Bronchi sweep up mucus coated debris, moving it upward to be coughed or swallowed 22

23 1. Nucleolus 2. Nucleus 3. Ribosome 4. Vesicle 5. Rough endoplasmic reticulum 6. Golgi apparatus (or "Golgi body") 7. Cytoskeleton 8. Smooth endoplasmic reticulum 9. Mitochondrion 10. Vacuole 11. Cytosol 12. Lysosome 13. Centriole 23

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