1. Cellular Functioning Chapter 5

2. CELLULAR MEMBRANES

3. Plasma Membrane’s Role Physical isolation – Ions & nutrient in, wastes & secretions out – Allows a concentration gradient to develop Regulates exchange with environment – Maintains homeostasis – Selective permeability Polarity (hydrophobic vs. hydrophilic) Charge (charged vs. uncharged) Size (large vs. small) Genes not necessary to arrange – Structure and function similar in all life

4. The Fluid Mosaic Model Integral proteins – Channels – Carriers Peripheral proteins Cell – cell recognition Phospholipid bilayer – Hydrophilic heads – Hydrophobic tails Fluidity – Cholesterol – Temperature

5. Types of Transport Passive Active Energy required Movement against a concentration gradient Maintains disequilibrium Energy not required Movement ‘down’ a concentration gradient Maintains dynamic equilibrium Specific types – Diffusion – Osmosis

6. Reviewing Terms Solute Solvent Solution Concentration

7. Simple Diffusion Movement of MOLECULES ‘down’ their concentration gradient – Small, nonpolar molecules E.g. O 2 in and CO 2 out of red blood cells – Each substance is independent Continues until equilibrium = no NET movement

8. Facilitated Diffusion Integral proteins move MOLECULES ‘down’ their concentration gradient – Large, polar molecules E.g sugars, AA’s, ions, and water – Are specific to substances Channels can open or close; carriers change shape Rate increases with an increase in protein number

9. Osmosis Movement of WATER ‘down’ its concentration gradient – Water binds to solute in solution – More solute = less free water = less water available to move Depends on TOTAL solute concentration and permeability water molecules glucose molecules

10. Tonicity Ability of a solution to cause a cell to gain or lose water – Depends on [solutes] that can’t cross PM relative to that in the cell Hypotonic solutions have a ___?__ [solute] than the cell – Water moves ____?______ Animal = lyse Plant = turgor pressure (central vacuole) Hypertonic solutions have a ___?__ [solute] than the cell – Water moves ____?______ Animal = crenation Plant = plasmolysis Isotonic solutions have ___?__ [solute] as the cell – Water shows no NET movement Plant = flaccid

11. Active Transport Movement of molecules against their concentration gradient ATP is energy source Maintains disequilibrium

12. Applying These Concepts Diffusion overview Practice problem – “Cell” is impermeable to sucrose Movement of solutes? Movement of water? Solution type? Resulting ‘cell’ shape?

13. Bulk Transport Exocytosis removes ‘stuff’ from inside the cell – Golgi apparatus to PM Endocytosis brings ‘stuff’ into the cell – PM pinches in to form vesicles Phagocytosis Pinocytosis Receptor-mediated

14. ENERGY REACTIONS

15. Energy Capacity to cause change or rearrange matter – Kinetic energy: energy of movement or objects in motion Heat: random movement of particles associated with KE – Potential energy: stored energy as a result of structure or location Chemical energy: PE available for release to do work Cells transform chemical energy into usable energy

16. Chemical Reactions Exergonic releases energy – Reactants have more PE than products – Cellular respiration converts stored energy to usable energy Endergonic needs a net input of energy – Products have greater PE than reactants – Photosynthesis converts energy-poor reactants to energy rich sugars Degree of energy change is equal to the differences in PE

17. The Importance of ATP Powers all cellular work ATP + H 2 O ADP + phosphate + E release – Reversible because phosphate can rejoin ADP – Process of phosphorylation, phosphate binds to a molecule to energize it

18. The Role of Enzymes Proteins that increase the rate of reaction w/o being consumed – Generally end in ‘-ase’ and are named for substrates – Lower the E A barrier Energy of activation (E A ) is the energy needed to be overcome to start a reaction Net change of energy is the same with or without

19. Enzymatic Reactions 3D shape determines reactivity Synthetic or degradative Enzyme activity factors – Temperature and pH denature – Buffers help regulate – Concentrations

20. Enzyme Inhibitors Competitive – Resembles substrate and competes for binding – Increasing [substrate] can compensate Noncompetitive – Binds elsewhere than at active site – Causes conformational change so substrate can’t bind Facilitates feedback inhibition which prevents overproduction of a substance by the cell