BSI Lecture 32-33 Krebs Cycle and ETC Flashcards
T or F? The Kreb cycle occurs in the mitochondria.
True
T or F? Kreb cycle does not need oxygen.
False, requires oxygen
How many pyruvate enters the cell from 1 molecule of glucose?
2
What is produced when pyruvate is fully oxidized?
4 NADH, 1 FADH2, 1 ATP
How many ATP results from glycolysis and aerobic respiration?
32
How many ATP results from aerobic respiration?
25
______ is waste product that diffuses out of mitochondria, into blood, and expelled via the ______. (Krebs cycle)
CO2; lungs
T or F? Production via anaerobic respiration is dominant energy source in most tissues.
False, aerobic
Pyruvate is decarboxylated, oxidized, and a CoA is attached, this is done by what enzyme?
Pyruvate dehydrogenase
Pyruvate + NAD+ + CoA → acetyl-CoA + CO2 + NADH + H+, what enzyme is responsible for this?
Pyruvate dehydrogenase
T or F? Acetyl-CoA + Oxaloacetate → Citrate + CoA-SH (citrate synthase)
False, H2O needs to be added to the left side
Citrate is isomerized into cis-aconitase and then to isocitrate -hydroxyl group is moved from one carbon to another by _________.
Aconitase
T or F? Isocitrate is oxidized and decarboxylated to form ά-ketoglutarate and NADH + H+(isocitrate dehydrogenase)
True
T or F? ά-ketoglutarate is oxidized, decarboxylated, and CoA is attached to form succinyl-CoA and NADH + H+ (ά-ketoglutarate dehydrogenase)
True
T or F? A Pi molecule (from solution) attaches and displaces CoA and then the Pi is donated to ADP to form ATP → succinate (GTP can donate P to ADP) (succinyl-CoA synthetase)
False, Pi is donated to GDP to form GTP
Succinate oxidized to _______ + FADH2 (succinate dehydrogenase)
Fumerate
What is added to fumerate to form malate?
H2O
Malate is oxidized to _______ + NADH + H+ (malate dehydrogenase)
oxaloacetate
What are the rate limiting enzymes for the Krebs Cycle?
- Pyruvate dehydrogenase (PDH)
- Citrate synthase
- Isocitrate dehydrogenase
- ά-ketoglutarate dehydrogenase
T or F? ADP, NAD+ (low energy status) stimulates Krebs Cycle
True
T or F? ATP, NADH (high energy status) stimulates Krebs Cycle
False, inhibits not stimulate
T or F? ETC is a series of electron carriers (protein complexes) located in the outer mitochondrial membrane
False, inner not outer
As pairs of electrons are passed down the complexes, H+ are pumped into the intramembrane space resulting in an electrochemical gradient for H+ (proton motive force). Where did the electrons come from?
from NADH and FADH2
As H+ flows back down its electrochemical proton gradient, passing through a special H+ channel (ATPase synthase) back into the _______, ATP is synthesized
Matrix
NADH averages how many ATP?
2.5
FADH2 averages how many ATP?
1.5
Which of the 5 complexes pump protons into the innermembrane space?
1, 3, and 5
Complex I: NADH dehydrogenase complex, NADH is _______ to NAD+.
Oxidized
What enzyme shuttles electrons from complex I to complex III?
Coenzyme Q
Complex II: (Succinate dehydrogenase-ubiquinone oxidoreductase) Accepts electrons from _____ and passes them to _____.
FADH2; Coenzyme Q
T or F? Complex III: (Cytochrome b-c1 complex) passes the electrons to Complex IV.
False, to Cytochrome C then to to Complex IV
Complex IV: Cytochrome c oxidase complex (COX), where do the electrons go from here?
Oxygen picks up the electron and forms H2O with 2H+
_______ is the final electron acceptor.
Oxygen
T or F? 2H+ 2e- + ½ O2 → H2O
True
The enzymatic phosphorylation of ADP to ATP coupled to electron transfer from a substrate to molecular oxygen is called ___ ____
oxidative phosphorylation
T or F? Complex V: (ATP synthase); Forms a hydrophilic tunnel through the inner mitochondrial membrane allowing H+ to move into the matrix following their electrochemical gradient (aka mitochondrial membrane potential, proton motive force)
True
As H+ passes through the complex, ______ force is converted into ______ _______ energy: ADP + Pi→ATP
mechanical; chemical bond
T or F? NADH → 10 H+ pumped out and 4 H+ required to make 1 ATP via ATP synthase = 2.5 ATP
True
T or F? FADH2 → 6 H+ pumped out and 4 H+ required to make 1 ATP via ATP synthase = 1.5 ATP
True
Why does FADH2 make less ATP than NADH?
FADH2 passes its electrons to Complex II, electrons only passes through 2 pumps instead of 3.
T or F? Regulation of ETC: ADP, Pi, (low energy status) inhibits ETC
False, stimulates
T or F? Regulation of ETC: ATP (high energy status) inhibits ETC
True
Can pyruvate be oxidized to acetyl-CoA under anaerobic conditions?
No
How many protons does Complex 1 and 3 pump each?
4
How many protons does Complex 4 pump?
2
How many protons does it take to pass through complex 5 produce 1 ATP
4
Cyanide inhibits which complex?
Complex 3
How does shutting down the ETC shut down the Krebs Cycle?
NAD+ and FAD cannot be recycled and a build-up of NADH inhibits the Kreb Cycle.
How many NADH are produced in the Krebs Cycle (one cycle)?
3
How many FADH2s are produced in the Krebs Cycle (one cycle)?
1
How many ATP is produced during the Krebs Cycle (one cycle)?
1
