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biochemistry exam 3

Terms in this set (94)

what cofactor activates g6p dehydrogenase?
NADP+
can coenzyme A be transported across the ineer mitochondrial membrane?
nope
in the pyruvate dehydrogenase complex, ____ ____ is required for the activity of E1
thiamine pyrophosphate
the citric acid cycle produces ____ NADH per turn of the cycle
3
in the electron transport chain, the Q pool can exist in ___ different oxidation states
3
_______ (with appropriate cofactors and enzymes) can be made from malate, can be made from pyruvate, and CANNOT be transported across the inner membrane of the mitochondria
oxaloacetate
brown adipose tissue is rich in _____
mitochondria
the B form of glyocgen phosphorylase can be made more active by the presence of excess ____ in the muscle
AMP
cyclic AMP (cAMP)... 3 things
1) is made from ATP via the enzyme adenylate cyclase
2) can activate protein kinase A
3) is an important SECONDARY messenger
fructose 2,6 biphosphate is produced enzymatically by ____
PFK 2
what enzyme catalyzes the rate-determining step of the pentose phosphate pathway?
glucose-6-phosphate dehydrogenase
protein phosphatase 1 (PP1)... 3 things
1) can dephosphorylate PHOSPHORYLASE KINASE
2) can dephosphorylate GLYCOGEN SYNTHASE
3) can be ACTIVATED in the liver by excess glucose
gluconeogenesis usually starts in the ?
mitochondrial matrix
what part of ATP synthase rotates?
the gamma (y) subunit
in the electron transport chain, electrons flow from molecules that have a ___ electron affinity to molecules that have a _____ electron affinity
low electron affinity ----> high electron affinity
outline the synthesis of glycogen from glucose 6 phosphate. mention key enzymes.
do it
outline the breakdown of glycogen to glucose in the liver. mention key enzymes.
do it
discuss how one of the metabolic pathways below is REGULATED and how it communicates with other pathways.
a) citric acid cycle
b) pentose phosphate pathway
c) glycogen breakdown
d) gluconeogenesis
do it
draw the structure of g6p
do it
draw the structure of pyruvate
do it
draw the structure of lactate
do it
draw the structure of g1p
do it
draw the structure of ribose-5-phosphate
do it
draw the structure of glutathione
do it
briefly discuss the importance of the Q cycle and why electrons need to pass through the electron transport chain one-by-one
do it
outline electron flow down the ETC, starting with reduced cofactors
do it
draw a rouch sketch fo the mitochondrion within a eukaryotic cell and indicate where the following processes occur- ETC, CAC, PPP, glycolysis, and gluconeogenesis
do it!!
discuss briefly how ATP synthase works
do it
true/false: the liver stores glucose in the form of glycogen because glucose is the major fuel source for the liver
FALSE
true/false: glycogen synthase catalyzes the formation of B14 glycosidic bond in glycogen using G1P as a substrate
FALSE
name a characteristic of the a form of glycogen synthase
more active
commonly seen in the LIVER
UN phosphorylated
R state
true/false: phosphorylase kinase is partially activated via phosphorylation of the beta subunit
TRUE
describe the allosteric behavior of glycogen phosphorylase in the muscle or the liver.
MUSCLE:
less active B form
T state
increased by AMP
stabilized by ATP and G6P

LIVER:
more active A form
R state

?
name one of the functions of protein phosphatase 1 (PP1)
1) shifts glycogen metabolism from degredation mode to synthesis mode
2) takes phosphate off glycogen synthase b, phosphorylase kinase, glycogen phosphorylase A
how does glucagon activate glycogen phosphorylase?
G-protein phosphorylation cascades
and it also converts glycogen phosphorylase B->A form
what is the rate determining step of the pentose phosphate pathway?
(1st step): G6P dehydrogenase
true/false: phase 2 (after the first 3 reactions of phase 1) of the pentose phosphate pathway is reversible
true
true/false NADPH is required for reductive biosynthesis in the cytosol
TRUE
true/false: phosphoglucomutase catalyzes the rate-determining step of glycolysis
false; the rate-limiting step of glycolysis is catalyzed by PFK : the conversion of G6P to F6P
true/false: glucose 6 phosphatase is active in adipose tissue
false; active in liver and adipose tissue
list several cofactors responsible for the activity of the PFK
activated by: AMP, F26BP,
inhibited by: ATP, citrate
true/false: succinate dehydrogenase is a soluble enzyme
false
true/false: fructose 26 BP activates fructose 16 B phosphatase
false
define anabolism
the process of building larger molecules from smaller ones
list several cofactors responsible for the activity of the pyruvate dehydrogenase complex (PDHC)
lipoic acid, NAD+, NADH, FAD, FADH2, thiamine pyrophosphate, coenzyme A
how is the pyruvate dehydrogenase complex (PDHC) regulated? 3 things
1) activated by F16BP
2) inhibited by NADH and acetyl coA
3) phosphorylation of PDH is mediated by pyruvate dehydrogenase kinase
briefly discuss regulation of the citric acid cycle
2 enzymes:
1) isocitrate dehydrogenase:
stimulated by: ADP
inhibited by: ATP and NADH
2) alpha-ketoglutarate dehydrogenase:
inhibited by: succinyl coA and NADH
the rate of the citric acid cycle is ___ when ATP is high
reduced
true/false: ubiquinone (oxidized coenzyme Q) can accept electrons from Complex I (NADH-Q oxioreductase) in the electron transport chain.
true
if oxaloacetate is lacking for the citric acid cycle, list at least one way it can be replenished. (2 enzymes)
1) pyruvate carboxylase
2) aspartate aminotransferase
list at least 2 exergonic steps of the citric acid cycle (3)
1) citrate synthase
2) isocitrate dehydrogenase
3) alpha-ketoglutarate dehydrogenase
what is the purpose of the glycerol 3-phosphate shuttle?
to move electrons from NADH into the mitochondria in muscle
what is ATP synthase used for and where does it get its energy from?
used for making ATP.
gets its energy from releasing the proton gradient into the mitochondrial matrix
what is the metal ion found in cytochrome c?
fe (iron)
what metal ions are important for electron transfer in complex IV?
Cu, Fe
what is the purpose of brown fat and how does it differ from other types of fat cells?
1) has uncoupling protein instead of ATP synthase
2) rich in mitochondria
3) used to generate heat
is citrate transported across the inner mitochondrial membrane?
YES
where do the components of complex II (succinate Q reductase) get electrons from predominantly?
FADH2
hydrolysis of triaclglycerols yields free fatty acids and glycerol in adipocytes. how can glyceol enter into gluconeogenesis?
>it can be transported to the liver
> glycerol kinase converts into glycerol 3 phosphate
> glycerol phosphte dehydrogenase converts that into dihydroxyacetone phosphate
how can pyruvate carboxylase be activated?
with acetyl coA
if ribose 5 phosphate is required, but NADPH is not required, how might the cell fulfill that requirement?
run PP in reverse, starting with fructose-6-P and glyceraldehyde 3 phosphate
list several metabolic fates of glucose 6 phosphate. why might the cell choose one path over the other? (4)
1) make it back into glucose
>when blood glucose is LOW
2) make it into glycogen
>when blood glucose is SUFFICIENT
3) make it into pyruvate
>when ATP is NEEDED
4) make it into ribose-5-phosphate
>when DNA/RNA/NAD+ is needed for NADP+ biosynthesis
why is PFK2 important?
controls the production and breakdown of F26BP
glucose is the primary fuel for ___
the brain
glucose is the ONLY fuel for ?
red blood cells
true/false: stage 1 of the PPP is reversible
false
transaldolases function in the ____
pentose phosphate pathway
which complex of the etc does not allow protons to be pumped out of the matrix?
complex II
the 3 irreversible steps of glycolysis have a ___ delta G
negative (spontaneous and may proceed)
biotin is a vitamin required by ___ ___ as a cofactor
pyruvate carboxylase
discuss regulation of F16BP
activated by: citrate and F16BPtase
inhibited by: AMP and F26BP
what are the 2 main steps of the cori cycle, and what is it important for?
1) lactate produced by muscle during contraction is released into the blood [GLYCOLYSIS]
2) liver removes the lactate and converts it into glucose, which can be released into the blood [GLUCONEOGENESIS]
IMPORTANT FOR RECYCLING
where are the 2 largest stores of glycogen?
liver and muscle
what enzyme converts G1P into G6P?
phosphoglucomutase
what is the key regulatory enzyme for glycogen DEGRADATION?
glycogen phosphorylase
what 2 hormones signal the need for glycogen BREAKDOWN?
epinephrine and glucagon (G PROTEIN CASCADES= cAMP)
what is glycogen SYNTHESIS catalyzed by?
UDP-glucose-pyrophosphorylase (irreversible)
what is glycogen SYNTHESIS regulated by?
glycogen synthase
how is PPP and glycolysis linked?
transketolase and transaldolase
the 1st stage of PPP is ___, while the 2nd stage is ____
1st stage= irreversible
2nd stage= reversible
draw the structure of glyceraldehyde
do it
the pyruvate dehydrogenase feeds ____ into the citric acid cycle
acetyl coA
what are the 3 steps of PDCH?
1) E1: decarboxylation
2) E2: oxidation
3) E3: formation of acetyl coA
what are the 2 fates of acetyl coA?
1) metabolism by the citric acid cycle
2) incorporation into fatty acids
discuss regulation of the PDHC
stimulated by: ADP and pyruvate
inhibited by: ATP, acetyl coA, and NADH
what does defective regulation of PDH result in?
lactic acidosis
in general, what's happening in the citric acid cycle?
CAC oxidizes the acetyl fragment of acetyl coA to CO2
what creates a proton gradient?
electron flow through the ETC
[oxidation of NADH and FADH2]
higher delta E= ____ affinity for electrons
higher
ETC is a series of ____ reactions
REDOX
Fe-S clusters are found in complexes __,___,and ___
I, II, and III
where does complex II get electrons?
FADH2
where is the Q pool located
inner mitochondrial membrane (reduced and oxidized Q)
what are the 3 forms of the catlytic B subunits of the f1 component of ATP synthase?
1) open (o)- nucleotides can BIND or be RELEASED
2) loose (l)- nucleotides are TRAPPED inside
3) tight (t)- ATP is synthesized from ADP +Pi
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