CMB311 Ch.25 Test With
Complete Solution
What is cellular respiration (aerobic respiration)? What are the three stagesof
cellular respiration (aerobic respiration)? What is oxidative phosphorylation?
- ANSWER - metabolic process leading to uptake of O2 and release of CO2
producing ATP
- Acetyl-CoA production
- Acetyl-CoA oxidation (citric acid cycle)
- Electron transport chain and oxidative phosphorylation-> re oxidation of
the reduced cofactors is coupled to the synthesis of large amounts of ATP
What is glycolysis? How does it fit into the "three stages of aerobic
respiration"? - ANSWER - Glycolysis is the initial stage of cellular respiration,
occurring in the cytoplasm
How many ATP, NADH and pyruvate molecules does it produce (from one
glucose)? What are the fates of pyruvate from glycolysis? - ANSWER - 2 ATP,
2 NADH, 2 Pyruvate
What are the basics of glycolysis? - ANSWER - incomplete glucose oxidation
- happens in cytoplasm
- 1 glucose (6-carbon) splits to form 2 molecules of pyruvate(3-carbon)
- no carbon released
- 2 NAD+ reduced to 2 NADH
,- 2 ATP produced
What is glycolysis "preparation" phase? What are the five reactions in the
prep phase? What are the substrates, products, enzymes, and special
characters for each reaction? What are the structures of the molecules
involved in each reaction? - ANSWER - glucose mol converted to two triose
phosphate mol. (glyceraldehyde 3-phosphate, GAP) at the expense of 2 ATP
STEP 1- formation of glucose 6-phosphate-- ATP hydrolysis drives the rxn
(couple rxn cost 1 ATP)
- negative charge traps
- intro pyruvate
STEP 2- Isomerization-- make C1 avail for phosphorylation, prepare for
cleavage
STEP 3- second phosphorylation-- "commitment step"; cost 1 ATP; fructose
6-phosphate (F-1), fructose 1,6-biphosphate (6-bisP), phosphofructokinase-1
(PFK-1)
STEP 4- Adol cleavage(actual glycolytic rxn)-- proceeds in forward direction
bc rxn products removed quickly, "pulling" the rxn in the direction of the
cleavage; 6-bisP-> dihydroxyacetone phosphate + glyceraldehyde
3-phosphate
STEP 5- Isomerization-- ketose<-> aldose; triose phosphate isomerase
What is glycolysis "payoff" phase? What are the five reactions in the payoff
phase? What are the substrates, products, enzymes, and special characters
for each reaction? What are the structures of the molecules involved in each
reaction? - ANSWER
,What is substrate-level phosphorylation? (How is it different from oxidative
phosphorylation?) - ANSWER
Does the "standard free energy change" (standard delta G) reflect the "real
free energy change" in the cells (delta G)? - ANSWER - some steps are pos
but the overall standard free energy is neg
- at actual cellular concentrations of intermediates, the free energies of all
the steps are either neg or close to zero (actual delta G)
How can NAD+ be regenerated for glycolysis through lactate and alcohol
fermentation? What are the enzymes involved? - ANSWER - reduced NADH is
re-oxidized in non-energy-generating rxn. both regen. NAD+ to allow
glycolysis to cont.
What are the chemical logics in glycolysis? - ANSWER achieves 3 important
things
- energy production (ATP NADH)
- precursor production (3-phosphoglycerate feeds into other pathways)
- breakdown of glucose into pyruvate to feed the TCA cycle
- glucose is split into 2 identical trioses (after isomerization)
- simplifies metabolism, only one set of enzymes needed downstream
- phosphorylation traps intermediates inside the cell, prepare for phosphoryl
group transfer in payoff
- isomerization positions carbonyl (glu to fruc) to make C1 avail for
phosphorylation, prepare for cleavage into 2 triose mols
How do other monosaccharides enter glycolysis? (in general, no detail) -
, ANSWER feeder pathways
Why metabolic pathways need to be regulated? What are the control points
in glycolysis - ANSWER - to control the rate of the respective pathway and
whether it is turned on or shut off
- hexokinase
-phosphofructokinase-1
-pyruvate kinase
What is hexokinase? What are isoenzymes (isozymes)? What are the two
types of hexokinase isozymes? How are they different? Is hexokinase
inhibited by glucose-6-phosophate in liver? - ANSWER - used to keep glucose
in the cell: enzymes introducing PO4 on glucose, using ATP
- hexokinases I-III
- low Km: .1 mM, located in all tissues except liver
- inhibited by glucose 6-phosphate
- glocokinase
- high Km: 10 mM, primarily in liver (pancreas, small intestine, and brain)
- not inhibited by glucose 6-phos
Why we say that phosphofructokinase regulation is complex? How does
fructose-2,6-biosphosphate regulate phosphofructokinase (positive or
negative) - ANSWER - ATP is required, ut if high, can also bind to allosteric
site and inhibit PFK-1
- this is relived by AMP, which competes with ATP for binding at the
Complete Solution
What is cellular respiration (aerobic respiration)? What are the three stagesof
cellular respiration (aerobic respiration)? What is oxidative phosphorylation?
- ANSWER - metabolic process leading to uptake of O2 and release of CO2
producing ATP
- Acetyl-CoA production
- Acetyl-CoA oxidation (citric acid cycle)
- Electron transport chain and oxidative phosphorylation-> re oxidation of
the reduced cofactors is coupled to the synthesis of large amounts of ATP
What is glycolysis? How does it fit into the "three stages of aerobic
respiration"? - ANSWER - Glycolysis is the initial stage of cellular respiration,
occurring in the cytoplasm
How many ATP, NADH and pyruvate molecules does it produce (from one
glucose)? What are the fates of pyruvate from glycolysis? - ANSWER - 2 ATP,
2 NADH, 2 Pyruvate
What are the basics of glycolysis? - ANSWER - incomplete glucose oxidation
- happens in cytoplasm
- 1 glucose (6-carbon) splits to form 2 molecules of pyruvate(3-carbon)
- no carbon released
- 2 NAD+ reduced to 2 NADH
,- 2 ATP produced
What is glycolysis "preparation" phase? What are the five reactions in the
prep phase? What are the substrates, products, enzymes, and special
characters for each reaction? What are the structures of the molecules
involved in each reaction? - ANSWER - glucose mol converted to two triose
phosphate mol. (glyceraldehyde 3-phosphate, GAP) at the expense of 2 ATP
STEP 1- formation of glucose 6-phosphate-- ATP hydrolysis drives the rxn
(couple rxn cost 1 ATP)
- negative charge traps
- intro pyruvate
STEP 2- Isomerization-- make C1 avail for phosphorylation, prepare for
cleavage
STEP 3- second phosphorylation-- "commitment step"; cost 1 ATP; fructose
6-phosphate (F-1), fructose 1,6-biphosphate (6-bisP), phosphofructokinase-1
(PFK-1)
STEP 4- Adol cleavage(actual glycolytic rxn)-- proceeds in forward direction
bc rxn products removed quickly, "pulling" the rxn in the direction of the
cleavage; 6-bisP-> dihydroxyacetone phosphate + glyceraldehyde
3-phosphate
STEP 5- Isomerization-- ketose<-> aldose; triose phosphate isomerase
What is glycolysis "payoff" phase? What are the five reactions in the payoff
phase? What are the substrates, products, enzymes, and special characters
for each reaction? What are the structures of the molecules involved in each
reaction? - ANSWER
,What is substrate-level phosphorylation? (How is it different from oxidative
phosphorylation?) - ANSWER
Does the "standard free energy change" (standard delta G) reflect the "real
free energy change" in the cells (delta G)? - ANSWER - some steps are pos
but the overall standard free energy is neg
- at actual cellular concentrations of intermediates, the free energies of all
the steps are either neg or close to zero (actual delta G)
How can NAD+ be regenerated for glycolysis through lactate and alcohol
fermentation? What are the enzymes involved? - ANSWER - reduced NADH is
re-oxidized in non-energy-generating rxn. both regen. NAD+ to allow
glycolysis to cont.
What are the chemical logics in glycolysis? - ANSWER achieves 3 important
things
- energy production (ATP NADH)
- precursor production (3-phosphoglycerate feeds into other pathways)
- breakdown of glucose into pyruvate to feed the TCA cycle
- glucose is split into 2 identical trioses (after isomerization)
- simplifies metabolism, only one set of enzymes needed downstream
- phosphorylation traps intermediates inside the cell, prepare for phosphoryl
group transfer in payoff
- isomerization positions carbonyl (glu to fruc) to make C1 avail for
phosphorylation, prepare for cleavage into 2 triose mols
How do other monosaccharides enter glycolysis? (in general, no detail) -
, ANSWER feeder pathways
Why metabolic pathways need to be regulated? What are the control points
in glycolysis - ANSWER - to control the rate of the respective pathway and
whether it is turned on or shut off
- hexokinase
-phosphofructokinase-1
-pyruvate kinase
What is hexokinase? What are isoenzymes (isozymes)? What are the two
types of hexokinase isozymes? How are they different? Is hexokinase
inhibited by glucose-6-phosophate in liver? - ANSWER - used to keep glucose
in the cell: enzymes introducing PO4 on glucose, using ATP
- hexokinases I-III
- low Km: .1 mM, located in all tissues except liver
- inhibited by glucose 6-phosphate
- glocokinase
- high Km: 10 mM, primarily in liver (pancreas, small intestine, and brain)
- not inhibited by glucose 6-phos
Why we say that phosphofructokinase regulation is complex? How does
fructose-2,6-biosphosphate regulate phosphofructokinase (positive or
negative) - ANSWER - ATP is required, ut if high, can also bind to allosteric
site and inhibit PFK-1
- this is relived by AMP, which competes with ATP for binding at the
