biology chapter 4

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biology chapter 4
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2012-03-09 11:58:13
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biology chapter 4
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  1. energy
    the capapcity to do work. Energy exists in many different forms. Motion, light, sound, chemical bonds, electricity, heat and magnetism are some examples.
  2. 1st law of Thermodynamics
    Energy cannot be created or destroyed. Any system taken as a whole, including the universe, has aq given amount of energy. That energy may be distributed in different forms.
  3. 2nd law of thermodynamics
    energy disperses spontaneously. For example a hot pan gives off heat. We will never see all of that heat flow back into the air into the pan.
  4. Phosphorylations
    Atp readily gives up a phosphate group to other molecules and primes them to react. Such phosphate group transfers are known as this.
  5. ATP /ADP Cycle
    atp is the main energy carrier for so many reactions, you may infer, that cells have ways to renew it. When Atp gives up a phosphate group ADP(jadenosine diphophate forms. Atp for again when adp binds to inorganic phosphate or to a phosphate group that was split away from a different molecule
  6. atp adpcycle
    Regeneration atp by this cycle helps drive most metabolic reactions. cells store and retrieve energy when tehy convert one molecule to another.
  7. glucose
    high energy compound because cells can harvest energy inherent in its bonds to build other molecules.
  8. oxidation-reduction reactions
    one molecule gives up electrons (it becomes oxidized) to another ( which becomes reduced.)
  9. Electron transfer chains
    redox reactions occur in these , arrays of enzymes and other molecules that pass electrons from one to teh next. think electrons bouncing down a staircase
  10. metabolic pathways
    small molecules become assembled into larger molecules. biosynthetic pathways require energy inputs. cells use and store thousand of substances in order, enzyme mediated reaction sequences called metabolic pathways. not all are linear, straight line reaction to producs.
  11. chemical equilibrium
    metabolic reactions do not run only forward, from reactants to products. Most also run in reverse, with products being converted back into reactants at least to some extent. such reversible reaction tend toward chemical equilibrium. when teh reaction rate is the same in both directions.
  12. enzymes
    are catalyst that cna make reactions occur hundred to millions of times faster than they would on their own. enzyme molecules can work again and again; a reaction does not use them up or alter them.
  13. Substrates
    enzymes recognize only certain reactancts, which are called substrates. except for a few RNAs , all enzymes are proteins.
  14. active sites
    enzyme molecules are far larger than substrates. each has one or more active sites; which are pockets or crevices where substrates bind and where reactions doccur. Part of teh substrate molecules is complementary in shape, size, charge, and solubility to teh active site.
  15. transition state
    in this state substrate bonds are at the breaking point, and the reaction can run easily to product. When we talk about activation energy, we really are talking about the enrgy it takes to align reactive chemical groups, destabilize electric charges, and break bonds.
  16. cofactors
    are non protein compounds and metal ions that associate with certain enzymes and are required for their function. organic cofactors such as vitamins are coenzymes, and many of them contain metal ions.
  17. antioxidant
    the iron atom in each heme helps catalase break down hydrogen peroxide to water and oxygen. catalase an antioxident, also neutralizes other strong oxidizers such as free radicals, substances with unpaired electrons. free radicals are dangerously reactive by products of aerobic respiration, attackikng DNA, lipids, and other biological molecules.we make less catalase as we age, so free radicals accumulate
  18. feedback inhibition
    when the cell has made enough proteins, tryptophan synthesis will continue until its accumulation causes feedback inhibition. this means some result of a specific activity shuts down the activity. here tryptophan stops tryptophan synthesis.
  19. selective permeability
    the way the plasma membrane struction lets some substances but not other cross it in certain ways, at certain times, is called selective permeability. lipids of a membranes bilayer are mostly nonpolar, so they let small, nonpolar molecules such as Ox and COx slip across.
  20. concentration gradient
    is a difference in the number per unit volume of molecules (or ions) of a substance between two regions.
  21. diffusion
    is the net movement of like molecules or ions down a concentration gradient. It contriubutes to the movement of substances through the cytoplasm and across membranes. In multicelled species, it moves substances between body parts and between teh body and its environment.
  22. electric gradient
    is simply a difference in electric charge between adjoining regions. for example, every ion dissolved in fluid bathing a cell membrane contributes to the electric charge at one side or the other. opposite charges attract. so the fluid with more negative charge overall exerts the greatest pull on positively charged substances, such as sodium ions.
  23. pressure gradient
    fifth, as you will see shortly diffusion also may be affected by a pressure gradient. this is a difference in the pressure being exerted in two adjoining regions.
  24. passive transport,
    a concentraction gradient, electric, gradient, or both drive diffusion of a substance across a cell membrane, through the interior of a transport protein. the protein does not require an energy input to assist the movement
  25. active transport
    energy driven protein motors help move a specific solute across the cell membrane against its conc entration gradient
  26. calcium pump
    this active trasnporter helps keep the concentration of calcium in a cell at least a thousand times lower than its outside.
  27. sodium potassium pump
    is a cotransporter. when atp activates it, this pump binds sodium ions on one side of the membrane and releases them on the other side. the release favors the binding of potassium ions at a different site in the tunnel through teh trasnporter, which reverts to its orginal shape after the potassium ions, is released to the other side.
  28. osmosis
    is diffusion of water across a selectively permeable membrane, into a region where the water concentration is lower.
  29. hypotonic
    when two fluids have different solute concentrations, the one with fewere solutes in it is hypotonic with respect to the other.
  30. hypertonic
    is the fluid with more solutes.
  31. isotonic
    tonicity refers to relative solute concentrations of two fluids on opposite side of a membrane. two fluids that have the same solute concentration are isotonic.
  32. hydrostatic pressure
    is the force that any volume of fluid exerts against a wall, a membrane, or some structure enclosing it. (in plants , this pressure is called turgor. hydrostatic pressure that has built up in a cell can counteract any further inward diffusion of water.
  33. osmotic pressure
    the amount of hydrostaqtic pressure that must be applied in order to halt the osmosis of water into a hypotonic solution is called osmotic pressure.
  34. exocytosis
    by this a vesicle moves to the surface, and the protein studded lipid bilayer of its membrane fuses with the plasma membrane. as this exocytic vesicle is losing its identity, its contents are released to the surroundings.
  35. endocytosis,
    there are three pathways of this. but all take up substances near teh cell surface. a small patch of plasma membrane balloons inward and pinches off inside the cytoplasm, forming an endocytic vesicle that moves its contents to some organelle or store them in a cytoplasmic region.

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