I. Chemical Reactions:
A. Metabolism:
1. metabolism - sum of all chemical reactions in a cell
a. catabolism - exergonic rxns (releases energy) for breakdown of larger molecules
b. anabolism - endergonic rxns (requires energy) for production of larger molecules
2. "energy" = electrons (stored in high-energy chemical bonds)
3. adenosine triphosphate (ATP) - common high-energy molecule
a. high energy phosphate bonds - formed by phosphorylation of ADP
b. ADP + Pi ---> ATP
4. coupled reactions
a. ATP synthesis (phosphorylation) is coupled to catabolic (exergonic) reactions
b. ATP splitting (dephosphorylation) is coupled to anabolic (endergonic) reactions
5. redox reactions
a. reduction = gain of electrons (or gain of hydrogen atoms)
b. oxidation = loss of electrons (or loss of hydrogen atoms)
c. reduction & oxidation always linked together
Why is a gain of energy or electrons termed "reduction"?
B. Enzymes
1. activation energy - amount of energy required to "drive" a chemical reaction
a. enzymes lower activation energy of a specific reaction
2. catalyst - increase rate of a reaction without be altered in that reaction
a. enzymes act as biological catalysts to speed up the rate of specific reactions
Do enzymes add energy to cause the chemical reaction to speed up?
3. specificity
a. of the hundreds of enzymes in a cell, each type only catalyzes a specific reaction
4. structure
a. enzymes are globular proteins dependant on 3-D conformation
5. apoenzyme - inactive protein part of an enzyme
6. cofactors/coenzymes
a. cofactors - inorganic molecules required to activate an enzyme
i. examples: Mg Zn Mn or other ions
b.coenzymes - organic molecules required to activate an enzyme
ii. examples: coenzyme A (pantothenic acid), NAD (niacin)
Is there an advantage to using cofactors/coenzymes
rather than simply producing a fully functional enzyme that does not require
any "activator" molecule?
7. holoenzyme - apoenzyme + coenzyme (or cofactor); active enzyme
8. active site - site 3-D "pocket" on enzyme where substrate binds
9. allosteric site - "other" site on enzyme, often where cofactor binds
10. Factors Affecting Enzyme Activity
a. pH, temp, substrate concentration
b. enzyme inhibitors
i. competative - competes with substrate
ii. noncompetative - binds to allosteric sites
How could you distinguish, in an experiment, between a competative and noncompetative enzyme inhibitor?
c. feedback regulation of enzymes
i. end-product regulation - example of threonine pathway
II. Glucose Metabolism:
A. Respiration and Fermentation
1. Compare & Contrast Respiration vs Fermentation
a. oxidative phosphorylation vs substrate-level phosphorylation
b. inorganic vs. organic end products
c. 38 (36 in euks.) ATP per glucose vs. 2 ATP per glucose
2. Compare & Contrast Aerobic vs Anaerobic Respiration
3. Glucose Catabolism Via Aerobic Respiration
a. glycolysis (net reaction only)
1 glucose + 2 ADP + 2Pi + 2 NAD+ -------> 2 pyruvic acid + 2 ATP + 2 NADH+H+
b. preparative step (per glucose net reaction only)
2 pyruvic acid + 2 ADP + 2 Pi-------> 2 acetyl CoA + 2 CO2 + 2 ATP + 2 NADH+H+
c. TCA cycle (two turns per glucose net reaction only)
2 acetyl CoA + 2 OAA + 2 ADP + 2 Pi + 6 NAD+ + 2 FAD+
-------> 2 OAA + 4 CO2 + 2 ATP + 6 NADH+H+ + 2 FADH2
d. oxidative phosphorylation (e- transport)
i. flavoproteins, coenzyme Q and cytochrome proteins embedded in membrane
ii NADH & FADH "deliver" electrons to membrane proteins
iii. membrane proteins use energy from electrons to pump protons out of cell (create proton gradient)
iv. 6 protons pumped out per NADH, 4 protons pumped out per FADH
Where in a eukaryotic cell does glycolysis, TCA cycle and electron transport occur? Is this the same in prokarotes?
e. final e- acceptor
i. aerobic: O2 accepts the "used" electron to form H2O
ii. anaerobic: SO4 , CO3, or NO3 , accepts electron to form H2S, CH4, or NO2
f. chemiosmosis
i. ATP synthase uses energy "stored" in proton gradient to synthesize ATP
ii. 1 ATP produced for each pair of protons returned into cell
iii. therefore, 3ATP produced for each NADH and 2ATP produced for each FADH
g. sum of aerobic glucose catabolism (overall net reaction) in prokaryotes
1 glucose + 38 ADP + 38Pi + 6 O2 -------> 6 CO2 + 38 ATP + 12H2O
Why do eukaryotes only get 36ATP/glucose while prokaryotes get 38ATP/glucose?
2. Fermentation
a. homolactic fermentation (net reaction only)
1 glucose + 2 ADP + 2Pi -------> 2 lactic acid + 2 ATP
b. alcohol fermentation (net reaction only)
1 glucose + 2 ADP + 2Pi -------> 2 ethanol + 2 CO2 + 2 ATP
c. heterolactic fermentation various other products
Why is it necessary for cells to convert pyruvic acid into lactic acid or alcohol if no more ATP is generated in that step?
3. Other Sources of Energy
a. lipids and amino acids as energy sources
b. glycerol => converted to pyruvate
c. fatty acids => beta oxidation to produce acetyl coA
d. amino acids are deaminated and enter the TCA cycle
Approximately how many ATP can be produced by using a single triglyceride rather than glucose?Or a single amino acid?
This is only a general outline.
There may be material that has been discussed in lecture that is not included in this outline
and there may be material on this outline that has not been discussed in lecture.
Any material discussed in lecture or listed in this outline is "fair game" for the test.