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53 Cards in this Set

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  • Back
Where does CAC take place?
mitochondria
Can CAC occur anaerobically?
No, NADH and FADH2 would accumulate if O2 were not available for the electron transport chain
What is the primary function of CAC?
oxidation of acetyl CoA to carbon dioxide
What energy resovoirs are used by CAC?
NADH, FADH2, and GTP
What is the major control enzyme?
Isocitrate dehydrogenase
What activates isocitrate dehydrogenase and what inhibits it?
Activated by: ADP
Inhibited by: NADH
To what enzyme is alpha-Ketoglutarate dehydrogenase similar?
pyruvate dehydrogenase complex
What does lack of thaimine slow?
oxidation of acetyl CoA in the citric acid cycle
What does alpha-Ketodehydrogenase need?
thiamine, lipoic acid, CoA, FAD and NAD
What does succinyl CoA synthetase catalyze?
substrate-level phosphorylation of GDP to GTP
Where is succinate dehydrogenase found?
inner mitochondrial membrane
What does succinate dehydrogenase function as?
complex II of the electron transport chain
Where is the majority of O2 in tissue consumed?
in the electron transport chain
What is the main function of O2?
accept electrons at the end of the chain
What oxidizes NADH?
NADH dehydrogenase (Complex I)

(delivering its electrons to the chain and returning as NAD to enzymes that require it)
Across which membrane is the proton gradient kept?
inner membrane
How does CAC function?
catalytically
What does citrate do?
it carries acetyl CoA into cytolasm for fatty acid synthesis
Where does electron transport and oxidative phosphorylation occur?
mitochondrial inner membrane
(cell membrane in prokaryotes)
What do you call reactions leading to TCA intermediates?
anaplerotic reactions
How many carbons are lost when going from citrate to oxaloacetate?
two

Citrate 6 carbon atoms
Oxaloacetate 4 carbon atoms
What is used to reform citrate from oxaloacetate?
Acetyl CoA
Which one can be transported across the mitochondrial membrane, malate or OAA?
malate
What does PEP carboxykinase do?
synthesizes PEP from OAA
What are the three names for CAC?
Citric Acid Cycle
Tricarboxylic Acid Cycle
Krebs Cycle
What is the input in CAC?
acetyl units
What is the output in CAC?
CO2, ATP or GTP, reduced cofactors
In CAC, what is the only five carbon intermediate?
alpha-ketoglutarate
For alpha-ketoglutarate to proceed to the 4-carbon stage what must the alpha-ketoglutarate release?
CO2
What is seen in the last four intermediates (succinate, fumarate, malate, and oxaloacetate)?
progressive oxidation
What happens to carbon 2 in succinate?
it changes from CH2 to C=O

yielding a loss of 4 electrons
The regulating enzymes of the TCA cycle control flux through?
1. substrate availability/concentration
2. product inhibition
3. competitive feedback inhibition
What are the most crucial regulators of the TCA cyle?
its substrates, actyl Coa and OAA and its product NADH
Do the concentrations at which Acetyl CoA and OAA are found in the mitrochondria ever saturate citrate synthase?
no
The metabolic flux in TCA through enzymes varies with what?
substrate concentration and is controlled by substrate availability
In TCA, NAD+ levels are a measure of what?
electron transport activity
In TCA, adenine nucleotides are a measure of what?
measure of energy charge
How many steps are in the CA cycle?
8
How many are oxidation reactions, which ones?
3,4,6,8
What is the oxidizing agent in 3,4, and 8?
NAD+
What is the oxidizing agent in 6?
FAD
What is special about step 5?
a molecule of GDP is phosphorylated to produce GTP, this reaction is equivalent to the production of ATP
What are the 2 sources of NADH (reducing equivalents)?
CAC metabolism and the cytosol via the shuttle system
What does the ETS pathway do?
the pathway by which electrons from reduced fuels are transferred to molecular oxygen... reduced cofactors NADH and FADH2 deliver electrons to oxygen to make ATP
Outer membrane of mitochondrion, two facts?
contains porins and is relatively permeable for molecules smaller than 10,000 Da
Inner membrane of mitochondrion, three facts?
1. permeable to O2, CO2 and H2O
2. contains transport proteins that control passage of metabolites (ATP, ADP, pyruvate, Ca2+, P...)
3. important for compartmentalization between mitochondria and cytosol
What drives phosphate import into mitochondrion?
Transmembrane proton gradient
In CAC, released CO2 molecules don't coome directly from acetyl-CoA but from ?
oxaloacetate
How many moles of ATP/mol of glucose are produced aerobically?
aerobically-38
Metabolon Hypothesis
enzyme molecules are noncovalently associated in an assembly called the metabolon that is localized to a particular area in the cytoplasm or in an organelle
Amphibolic
both anabolic and catabolic
Catabolic
degradation, energy conservation
Anabolic
pathways use cyclic intermediates