Metabolism & Enzymes

Here are 20 basic points on metabolism and enzymes:

1. First law of thermodynamics: The total amount of energy existing is constant. Energy can be added, removed, transfered, yet cannot be destroyed.

2. Second law of thermodynamics: Entropy (randomness) always increases. The free energy in the universe is constantly decreasing, entropic energy is always increasing. Free energy is used to determine order. The universe always leads towards entropy.

3. Third law of thermodynamics: Absolute Zero (-273.15 degrees celsius) is the lowest temperature hypothecially achievable. At this temperature, matter will cease to vibrate, and thus cease to exist.

4. Molecules store energy through their bonds. Ergo, it's called bond energy. Bond energy is the minimum energy required to break one mol of bonds between two types of atoms. A molecule with a larger bond (e.g. double bond) will generally have a larger amount of bond energy stored than a molecule with a smaller bond (e.g. single bond)

5. Exothermic reaction: when more energy is released during bond FORMATION than bond BREAKING, leading to a output of energy.

6. Endothermic reaction: when more energy isabsorbed to break the bonds than to form the new bonds, leading to an absorption of energy.

7. Spontaneous changes? Two factors determine a spontaneous change: Energy and Entropy. Exothermic reactions are favoured, and those that lead to an increase in entropy are also favoured. Thus, these will always occur spontaneously. However, those exothermic reactions that lead to a decrease in entropy will not be spontaneous at high temperatures. Conversly, endothermic reactions are not favoured by the universe, and neither are decreases in entropy, thus they are not spontaneous at all temperatures. Changes proceed only with a net input of energy. But, an endothermic reaction with an increase in entropy will be spontaneous at high temperatures, (still not spontaneous at low temperatures)

8. Free energy: Energy that can do work.  A change in free energy leads to an increase in entropy. All sources of free enegy in theworld, according to entropy, will become completely disordered and useless.

9. Exergonic reaction: Change in Gibbs free energy (decrease; negatively). Spontaneous

10. Endergonic reaction: Change in Gibbs free energy (increase; positively). Non-spontaneous.

11. For example, in cellular respiration, 2870 kJ of free energy per mol of glucose processed is made available to the cell for performing cellular work, thus change in G = -2870 kJ/mol used
      In photosynthesis, 2870 k of work is done by light energy for every mol of glucose formed in the overall process. This amount of free energy is absorbed in the overall processby te glucose, thus change in G = 2870 kJ/mol formed

12. ATP is the main source of free energy in living cells. When cell requires free energy to drive an endergonic raction, an enzyme called ATPase catalyzes the hydrolysi of

13. ATP contains adenine, attached to 5 carbon sugar ribose, which is bound to THREE phosphate groups (tri)

14. Redox reactions: LEO the lion goes GER = Losing Electrons is Oxidation, Gaining electrons is Reduction.

15. The substance that provides the electron is called the reducing agent; the substance that takes the electron is called the oxidizing agent.

16. Enzymes speed up endergonic and exergonic reactions by lowering the activation energy, but does not change the value of G.

17. To inhibit enzymes, there are inhibitors that are designed to stop an enzyme's actions.

18. The competitive inhibitor are similar to the enzyme's substrate (the reactant tht the enzyme acts on when catalyzing). They block the enzyme's activie side and prevent binding. Non-competitive inhibitors aren't shaped like the enzyme; they attach to anoher site and changes te enzyme's shape.

19. Allosteric sites are receptor sites that give room to substance to bind to in order tostimulate an enzyme's ability.

20. Feedback inhibition is a a method of metabolic control that a product formed later in a sequence of reactions alloseterically inhibits an enzyme that catalyuzes a reaction occurring earlier in the process..?