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Biochem test 3
lectures 23-25
121
Biochemistry
03/13/2011

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Term
What is oxidation (general)
Definition
gives up electrons/reducing equivalents
Term
What is reduction (general)
Definition
gains electrons/reducing equivalents
Term
If something has a very negative E (reduction potential) it is called:
Definition
reductant
Term
If something has a most positive E (reduction potential) it is called:
Definition
oxidant
Term
What is delta E?
Definition
E (ox) - E (red)
Term
in terms of delta E, delta G =
Definition
-nFdeltaE
Term
location of electron-transfer chain complexes
Definition
inner membrane of mitochondria
Term
What is the matrix and what is inside
Definition
area inside the inner membrane of the mitochondria
pyruvate dehydrogenase, TCA cycle enzymes, and Fatty-acid oxidation enzymes
Term
general purpose of electron transfer chain
Definition
takes electrons from nutrients and gives them to oxygen
Term
what are nutrients oxidized by?
Definition
TCA cycle, fatty-acid oxidation, pyruvate dehyrdogenase
Term
where do the electrons go when nutrients are oxidized?
Definition
FADH2, NADH, UQH2
Term
what is the energy released from redox reactions at electron-transfer chain complexes used for?
Definition
pumping protons from membrane to cytosol
Term
what is the concentration gradient of protons (charge) used for?
Definition
ADP + P >>> ATP
Term
where is ATPase located
Definition
inner mitochondrial membrane
Term
What is Complex I called?
Definition
NADH dehydrogenase
Term
Complex I reaction

NADH + UQ >>>
Definition
NAD+ + UQH2
Term
Complex I:

1 NADH = how many protons?
Definition
4 protons (because reaction is very exergonic)
Term
What is Complex II called
Definition
succinate dehydrogenase
Term
Complex II reaction:

succinate + UQ >>>
Definition
fumarate + UQH2
Term
Complex II:

1 succinate = how many protons
Definition
0 (reaction is not exergonic enough)
Term
what does glycerol-3-phosphate dehydrogenase do?
Definition
oxidizes glycerol-3-phosphate in the cytosol; reducing equivalents go from cytosol to inner mitochondrial membrane
Term
what is UQH2 used for?
Definition
in complex III
reduces cytochrome c
Term
What is complex III called
Definition
cytochrome bc1 complex
Term
What is the reaction of Complex III

UQH2 + Cyt c(Fe3+) >>>
Definition
UQ + Cyt c(Fe2+)
Term
Complex III:

1 uqh2 = HOW MANY protons
Definition
2 protons
Term
What is complex IV called?
Definition
Cytochrome C oxidase
Term
What is the reaction of Complex IV

4 Cyt C(Fe2+) + O2 + 4H+ >>>
Definition
4 Cyt C(Fe3+) + 2 H2O
Term
Complex IV:

1 H2O produced = how many protons
Definition
4 protons
Term
Overall, where do high energy electrons from nutrients go and what do they form
Definition
oxygen
water
Term
What is reduction potential?
Definition
The tendency for a species to gain electrons
Term
In what way do electrons move spontaneously?
Definition
from reductants (negative) to oxidants (more positive)
Term
Examples of reductants
Definition
carbos, fats
Term
example of oxidant
Definition
oxygen (electron-acceptor)
Term
example of oxidant
Definition
oxygen (electron-acceptor)
Term
The higher the delta E>>>
Definition
the lower the delta G, so reaction is spontaneous and releases energy
Term
How do protons come back into mitochondria after being pumped out?
Definition
ATP synthase
Term
what provides the energy to pump H+ out of the mitochondria
Definition
the redox reactions at the complexes
Term
list electron carriers from lowest potential to highest potential
Definition
NADH>UQ>Cyt C>O2

remember electrons move from reductants to oxidants
Term
What is the path of electrons on Complex I
Definition
NADH>>>FMN>>>FeS>>>UQ
Term
How many electrons can FAD and FMN carry?
Definition
2
Term
How many electrons can FeS carry?
Definition
1
Term
How many electrons can UQ carry?
Definition
2
Term
What is the path of electrons on Complex II?
Definition
succinate>>>FADH2>>>2FE2+>>>UQH2
Term
essentially what does complex III do
Definition
uses the UQH2 from complexes I and II and other pathways to reduce cytochrome c
Term
Characteristics of QH2
Definition
lipid soluble, 2-electron carrier
Term
characteristics of cytc
Definition
water-soluble electron carrier
Term
what is the transmembrane protein of complex III
Definition
b cytochrome (with hemeb's)
Term
what happens to cytochrome C at Complex III
Definition
reduced
Term
What happens to cytochrome C at Complex IV
Definition
gets re-oxidized
Term
how many cyt C's are needed to reduce oxygen to water
Definition
4
Term
If Complex I is inhibited, what happens to ETC>
Definition
UQH2 is still regenerated by other reactions
only complex III and IV pump protons, so there's a smaller gradient and less ATP is made
NADH builds up, inhibiting dehydrogenase reactions
Cells will start converting pyruvate to lactate to regenerate NAD+
Term
How much energy is required to pump 1 mole of H+ out of the mitochondria?
Definition
20 kJ
Term
If electrons are donated from NADH,how many protons are pumped across the mitochondria from one reducing equivalent?
Definition
10
Term
If UQH2 donates electrons (not NADH), how many protons are pumped from one reducing equivalent?
Definition
6
Term
what do uncouplers do?
Definition
deplete the proton gradient without making ATP
Term
2 domains of Complex V
Definition
F0 and F1
Term
structure of domain F0
Definition
membrane-bound protein channel
Term
structure of F1 domain
Definition
extends into matrix
3 alpha and 3 beta subunits
Term
Where is the binding site for ADP and Pi
Definition
on beta subunits of complex V
Term
what happens to the F0 domain on the complex V as protons move from outside to inside
Definition
it rotates
Term
what happens when the F0 domain rotates
Definition
the beta subunits on the F1 domain changes shape (tight to open to loose)

1 proton = 1/3 of rotation
Term
what is the tight-conformation of the beta subunits
Definition
ATP is tightly bound
Term
what is the open conformation of the beta subunits of F1
Definition
exchanges ATP for ADP+P
Term
What is the loose conformation of the beta subunit of F1 domain
Definition
ADP+P is bound to it
Term
How many ATP produced using 1 reducing equivalent of NADH
Definition
10 H+ pumped across membrane
---------------------------- =
4 H+ to make 1 ATP

2.5 ATP
Term
How many ATP produced using 1 reducing equivalent of UQH2?
Definition
6 protons pumped across membrane
-------------------------------- =
4 protons through ATP synthase

1.5 ATP
Term
what are the 2 shuttle systems used to get reducing equivalents from cytosol to mitochondria?
Definition
Glycerol Phosphate shuttle
Malate Shuttle
Term
what is the pathway of the glycerol-phosphate shuttle?
Definition
NADH reduces dihydroxyacetone to glycerol-3-phosphate
glycerol-3-phosphate is oxidized back into dihydroxyacetone, and UQ is reduced to UQH2
energy is lost
Term
pathway of malate shuttle system?
Definition
NADH reduces oxaloacetate to malate
Malate enters mitochondria
Malate is oxidized to oxaloacetate while NAD+ is reduced to NADH
Term
what triggers insulin release from the pancreas
Definition
glucose present in the bloodstream
Term
which 3 pathways does insulin activate?
Definition
glycolysis, glycogen synthesis, and fatty-acid synthesis

(pathways that USE glucose)
Term
what 2 pathways does insulin inhibit?
Definition
gluconeogenesis, glycogenolysis

(pathways that MAKE glucose)
Term
what is reciprocal regulation?
Definition
glucagon has the opposite effect of insulin in carbohydrate metabolic pathways

Term
insulin increases the synthesis of which 2 enzymes
Definition
glucokinase and pyruvate kinase
Term
how is glucose transported into the cell
Definition
GLUT
Term
what is the effect of insulin on muscle and adipose
Definition
increase GLUT-4
Term
where is glucokinase found?
Definition
liver
Term
kinestics of glucokinase?
Definition
sigmoidal
Term
kinetics of hexokinase?
Definition
hyperbolic
Term
glucokinase: maximal activity in which state?
Definition
fed state
Term
when does liver use glucose
Definition
fed state
Term
when do cell types other than liver use glucose
Definition
fed and fasting states
Term
describe 2 active sites of PFK-2
Definition
one is a kinase active site and one is a phosphatase active site
Term
which active site on PFK-2 is activated by insulin
Definition
kinase
Term
when the kinase active site on PFK-2 is activated, what is synthesized?
Definition
F-2,6-BP>>>activates PFK-1>>>activates glycolysis
Term
which active site on PFK-2 is activated by glucagon?
Definition
phosphatase>>>hydrolyzes F-2,6-BP>>>removes activation of PFK-1 and slows down glycolysis
Term
what effect does insulin have on pyruvatekinase
Definition
activates it
Term
when ATP is present, what happens to pyruvatekinase?
Definition
it is inhibited, bc there is already lots of energy made, so glycoslysis doesn't need to happen
Term
which forms of pyruvatekinase is active and inactive?
Definition
phosphorylated is inactive, reverse is active
Term
when there is glucagon present, what doe sit do to pyruvatekinase?
Definition
glucagon = fasting state = not a lot of glucose present
activates kinase, which phosphorylates pyruvatekinaseand in turn inactivates it
Term
when there is insulin present, what happens to pyruvatekinase
Definition
insulin present = glucose in the bloodstream
activates phosphatase which dephosphorylates the pyruvatekinase, making it active and glycolysis proceeds
Term
what is the activity level of PDH controlled by?
Definition
energy state of cell
NAD+/NADH and ATP/ADP ratios
Term
which form of PDH is inactive?
Definition
phosphorylated PDH
Term
presence of NADH and acetyl coA does what to PDH?
Definition
PDH becomes inactive

NADH and acetyl coA are products, so that alloesterically inhibits it (high energy state)
also they activate kinase to phosphorylate and deactivate it
Term
what is TCA cycle regulated by?
Definition
energy level of cell
NAD+/NADH and ATP/ADP
Term
High NADH/NAD+ ratios will ____ dehydrogenase enzymes of TCA cycle
Definition
slow activity of
Term
what are the products of the TCA cycle and where do they go?
Definition
NADH and UQH2>>>electron transport chain
Term
why does production of ATP stimulate TCA cycle
Definition
increase in production of ATP will cause high rate of NADH oxidation by electron transfer chain and this stimulates TCA cycle to produce more NADH
Term
what does pyruvatecarboxylase do?
Definition
synthesizes oxaloacetate from pyruvate and CO2
Term
which 3 substrates generate UQH2?
Definition
succinate
glycerol phosphate
fatty acyl coA
Term
what is the pH in respiring mitochondria?
Definition
.75
Term
example of inhibitor of ATPase
Definition
oligomycin
Term
example of uncoupler
Definition
2,4 DNP
Term
2 allosteric inhibitors of PFK-1
Definition
citrate and ATP
Term
What does PFK-1 synthesize?
What does PFK-2 synthesize?
Definition
F-1,6-BP
F-2,6-BP
Term
which molecule has 2 active sites, kinase and phosphatase
Definition
PFK-2
Term
what activates pyruvatekinase?
Definition
Fructose-1,6-Bisphosphate
Term
which enzyme changes glucose to glucose-6-phosphate
Definition
hexokinase
Term
what does glucose-6-phosphate inhibit and what is this process called?
Definition
hexokinase; negative feedback inhibition
Term
what does fructose-2,6-bisphosphate activate?
Definition
PFK-1
Term
what is F-2,6-disphosphate controlled by?
Definition
insulin and glucagon
Term
what stimulates pyruvate kinase?
Definition
fructose-1,6-bisphosphate
Term
2 products of PDH
Definition
Acetyl CoA and NADH
Term
which 2 substrates cause inactivation of the kinase the phosphorylates PDH, keeping it active?
Definition
NAD+ and CoA
Term
what activates the phosphatase which removes the phosphate on PDH
Definition
Ca++ (from contracting muscles)
Term
what effect does "blocking" one of the complexes in the ETC have on the TCA cycle?
Definition
it shuts it down. no flux of electrons>>>buildup of NADH>>>goodbye TCA
Term
what is the rate-determining step of the TCA cycle
Definition
isocitratedehydrogenase
Term
in the TCA cycle, what does isocitrate get turned into?
Definition
alpha-ketoglutarate
Term
If there is a lot of ADP present in the TCA cycle, what happens?
Definition
stimulates TCA cycle bc it needs energy (ATP)
Term
what effect does ATP hav eon TCA
Definition
inhibition
Term
If TCA is going slowly and more energy is needed, what happens
Definition
if there's plenty of pyruvate, some of it will get converted into oxaloacetate