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Biochem Quiz 6
Chapter 15 and 16
| Term | Definition |
|---|---|
| Three stages of generation of energy from food | 1) large molecules in food are broken down into smaller molecules in the process of digestion 2)small molecules are processed into key molecules of metabolism (acetyl CoA) 3) ATP is produced from the complete oxidation of acetyl CoA |
| Energy is required to meet three fundamental needs | 1) mechanical work of movement 2) active transport of molecules across membranes 3) biosynthesis of biomolecules and new cells |
| phototrophs | obtain energy from capturing sunlight |
| chemotrophs | obtain energy through oxidation of carbon fuels |
| basic principles govern energy manipulations in all cells | 1) metabolic pathways 2) ATP is energy currency all life 3) oxidation of C fuels = formation of ATP 4) # of rxn types and intermediates are common to many pathways 5)metabolic pathways highly regulated 6)enzymes organized in large complexes |
| metabolic pathways | molecules are degraded or synthesized stepwise in a series of reactions termed metabolic pathways |
| metabolism is composed of many interconnecting rxns | series of linked rxns that convert a specific reactant into a specific product the entire set of cellular metabolic rxns are called intermediary metabolism |
| catabolic pathways | combust carbon fuels to synthesize ATP or ion gradients |
| anabolic pathways | use ATP and reducing power to synthesize large biomolecules |
| amphibolic pathways | anabolically or catabolically, TCA cycle |
| two criteria for a metabolic pathway | 1) individual reactions must be specific 2) the pathway in total must be thermodynamically favorable |
| How do you make an unfavorable reaction in a pathway occur? | coupling it to a more favorable reaction |
| adenosine triphosphate (ATP) | universal currency of free energy, energy derived from fuels or light converted into, energy rich molecule due to the triphosphate unit containing two phosphoanhydride linkages, kinetically stable, thermodynamically unstable |
| ATP - thermodynamically unstable | negative charges - only lasts a minute in soln |
| ATP - kinetically stable | can stabilize with + charges, ideal regulatory molecules - added by kinases ad removed by phosphatases |
| ATP hydrolysis | exergonic, used to power a host of cellular functions, free energy liberated - drive non-spontaneous reactions, formed when fuel molecules are oxidized (chem) or light is trapped (auto) |
| keq | [products]/[reactants], e^-deltaG/RT, RT= (2.47) |
| phosphoryl-transfer potential | means of comparison, tracking the ability of different organic molecules to transfer a phosphoryl group to water, standard free energy of hydrolysis |
| standard free energy of hydrolysis | energy released during phosphoryl-transfer potential |
| ATP phosphoryl-transfer potential is high because: | 1) charge repulsion 2) resonance stabilization 3) increase in entropy 4) stabilization by hydration |
| ATP phosphoryl-transfer potential | intermediate among phosphorylated molecules - carrier of phosphoryl groups |
| ATP presence in cells | 2-8 mM - way beyond the Km of most enzymes that use ATP as a substrate, hydrotrope, helps proteins stay soluble despite high conc in cells |
| hydrotrope | amphipathic molecules that do not self-aggregate like lipids due to a small hydrophobic component |
| oxidation rxns | loss of electrons - coupled with reduction |
| redox | oxidation:reduction pair, C atoms oxidized to yield CO2 and the electrons are accepted by O2 to form water, more reduced = more energy when oxidized |
| What is a more efficient food source, fats or glucose? | fats because they are more reduced |
| activated carriers | small number of recurring activated groups in many metabolic pathways, transfer is highly exergonic, very kinetically stable -regulated by enzymes |
| NAD+ and FAD | carry activated electrons derived from the oxidation of fuels |
| Acetyl CoA | carries activated acyl groups |
| NADP+ | similar to NAD+ but active in anabolism |
| Coenzyme A | activated carrier of acyl groups such as the acetyl group, transfer is exergonic because the thioester is unstable |
| riboflavin b2 | redox FAD |
| nicotinic acid (niacin, B3) | NAD+ |
| pantothenic acid (B5) | coenzyme A |
| metabolic processes are regulated in there principal ways | 1) amt of enzyme 2) catalytic activity of enzymes 3) accessibility of substrates |
| amount of enzyme | quantity present can be regulated at the level of gene transcription |
| catalytic activity of enzymes | regulated allosterically or by reversible covalent modification, energy status of the cell is an important regulator |
| the accessibility of substrates | opposing reactions such as fatty acid synthesis and degradation may occur in different cellular compartments |
| energy charge | depends on the relative amts of ATP, ADP, and AMP, fluctuates, 0(all amp) to 1 (all atp), high energy charge inhibits ATP generating and stimulate ATP utilizing |
| phosphorylation potential | alternative index of the energy status of the cell, depends on the conc of inorganic orthophosphate |
| why is glucose such a prominent fuel in all life forms? | primitive biochemical systems because it can form under prebiotic conditions most stable hexose low tendency to non enzymatically glycosylate proteins |
| Glycolysis | converts one molecule of glucose to two molecules of pyruvate with the generation of four molecules of ATP enzymes are associated with one another evidence - enzymes are organized into complexes |
| Glycolysis: two parts | 1) traps glucose in the cell and modifies it so that it can be cleaved into a pair of phosphorylated 3-C compounds 2)oxidizes the 3-c compounds to pyruvate while generating 2 molecules of atp |
| step 1: hexokinase traps glucose in the cell and begins glycolysis | glucose enters cell through specific transport protein --> phosphorylated at the expense of ATP to form glucose - 6 - phosphate |
| Hexokinase | requires Mg2+ or Mn2+, catalyzes step one, employs substrate binding induced fit to minimize hydrolysis of ATP |
| Step 2: fructose 6-phosphate is generated from glucose 6-phosphate | glucose 6-phosphate --> glucose 6-phosphate, isomerase, readily reversible |
| step 3: fructose 1,6-bisphosphate is generated from fructose 6-phosphate | fructose 6-phosphate is trapped in the fructose form by the addition of a second phosphate to form fructose 1,6-bisphosphate, irreversible, phosphofructokinase |
| bisphosphate | two separate monophosphoryl groups are present |
| step 4: cleavage of fructose 1,6-bisphosphate to 3-c molecules | dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GAP), readily reversible - aldolase |
| step 5: triose phosphate isomerase rxn | DHAP cannot be processed to pyruvate - triose phosphate isomerase interconverts GAP and DHAP, allowing DHAP to be further metabolized |
| triose phosphate isomerase deficiency | lethal - severe hemolytic anemia |
| step 6: the oxidation of an aldehyde powers the formation of a compound having high phosphoryl transfer potential | oxidation of GAP - glyceraldehyde 3-phosphate dehydrogenase - 2 steps, oxidation of GAP (exer) to acid, acid to 1,3-bisphosphoglycerate from acid (ender), linked by thioester in active site of enzyme |
| step 7: atp is formed by phosphoryl transfer from 1,3-bisphosphoglycerate | oxidation of carbon atom - forms ATP, greater phosphoryl transfer potential that ATP |
| Step 8 | 3-phosphoglycerate is converted into 2-phosphoglycerate by phosphoglycerate mutase |
| step 9 | 2-phosphoglycerate undergoes a dehydration reaction, catalyzed by enolase, producing phosphoenolpyruvate (PEP) |
| step 10 | phosphoenolpyruvate is a high phosphoryl transfer compound because the presence of the phosphate traps the compound in the unstable enol tautomer. ADP is phosphorylated at the expense of PEP, generating ATP and pyruvate - pyruvate kinase |
Created by:
rorymcnaughton
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