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Why size and shape matters

Why size and shape matters. Cells need to maximise their surface area to ensure the rapid movement of molecules. Prokaryotic vs. Eukarotic cells. My volume is small enough to meet the needs of molecules. I need lots of internal membranes and compartments to meet the needs of molecules.

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Why size and shape matters

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  1. Why size and shape matters • Cells need to maximise their surface area to ensure the rapid movement of molecules.

  2. Prokaryotic vs. Eukarotic cells My volume is small enough to meet the needs of molecules I need lots of internal membranes and compartments to meet the needs of molecules

  3. Two Basic Cell Types • .

  4. Two basic cell types

  5. Cellular Organization Cell  Tissue Organ Organ system Organism • Tissue – group of cells functioning together. • Organ – group of tissues functioning together. • Organ System – group of organs functioning together. • Organism – group of organ systems functioning together.

  6. Animal Cell

  7. Plant cell

  8. Prokaryotic cell-Bacteria

  9. Function of cell wall • structural support and protection, gives shape • acts as a filtering mechanism • is to act as a pressure vessel, preventing over-expansion when water enters the cell. • Plant cell wall made up of cellulose • Bacterial cell wall made up of

  10. Turgor Pressure- force exerted by the water entering (osmosis) the vacuole, which then swells exerting internal force on the cell wall • Causes “rigidity

  11. The Plasma Membrane

  12. Structure of plasma membrane • The plasma membrane is a continuous double-layer of phospholipids, interweaved with cholesterol and proteins. • Three classes of lipid molecules make up the plasma membranes - phospholipids, cholesterol and glycolipids. • The membrane is fluid, and the molecules are always moving.

  13. Function of cell membrane • Membrane defines the cell boundary and provides a permeability barrier. • Membranes regulate the transport of solutes. • Membranes detect electrical and chemical signals. • Membranes assist in cell to cell communication.

  14. How does the chemical nature of the membrane assist its function? • -flexible - allows to form vesicles to carry large molecules in and out of the cell • Hydrophilic and hydrophobic ends- they line up to form a barrier. • Bilayer- lipid soluble molecules enter and leave cells easily through the bilayer

  15. Membrane protein Structure Function • Membrane proteins function as 1. Enzymes—regulate chemical reactions within the cell 2. receptors—control the uptake of molecules 3. transport proteins—carriers, channels, and pumps get molecules across membrane into cell (integral) 4. anchors—cytoskeletal proteins/extracellular matrix proteins • Cell membrane contains integral proteins and peripheral proteins Integral proteins—all the way through the bilayerPeripheral proteins—poking only through one side of bilayer

  16. Function of membrane cholesterol • Cholesterol is an amphipathic molecule(has polar and non polar ends) Cholesterol makes the plasma membrane • Stable • Flexible

  17. Factors governing substances crossing a lipid layer 1)Size 2) degree of polarity 3) charged atoms Permeable to small molecules (oxygen, carbondioxide, ethanol) Lipid bilayer Permeable to hydrophobic molecules Not permeable to large hydrophilic molecules(glucose) and charged group of atoms and metallic ions.

  18. Solutions hypotonic hypertonic isotonic c Higher solute concentration Low solute concentration Same solute concentration v v

  19. Why are osmosis & diffusion important? • All living things have certain requirements they must satisfy in order to remain alive – maintain homeostasis • These include exchanging gases (usually CO2 and O2), taking in water, minerals, and food, and eliminating wastes. • These tasks happen at the cellular level. • Molecules move through the cell membrane by diffusion and osmosis.

  20. SimpleDiffusion • Simple diffusion is a passive process. • Area of high solute concentration to low solute concentration

  21. Osmosis • Osmosis is simple diffusion of water from a region of high water concentration through a semi-permeable membrane to a region of low water concentration. Low solute concentration to high solute concentration

  22. PASSIVE TRANSPORT ACTIVE TRANSPORT Simple diffusion

  23. Active Transport The protein involved are generally called “pumps”. The protein needs to be coupled with an energy providing reaction usually hydrolysis of ATP Importance of active transport -uptake of essential nutrients against the concentration gradient -allows removal of waste and secretory products against the concentration gradient

  24. BULK TRANSPORT

  25. BULK TRANSPORT Large quantity of liquid and solid materials are taken in and out of the cell by endocytosis and exocytosis

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