Q&A Flashcards
The rate-limiting step in glycolysis is catalysed by:
a) hexokinase
b) phosphofructokinase-1
c) glyceraldehyde phosphate dehydrogenase
d) phosphoglycerate kinase
e) pyruvate kinase
B - phosphofructokinase-1
Which of the following statements about the beta oxidation of fatty acids is INCORRECT?
a) Fatty acids are transported into the mitochondria via the carnitine carrier
b) In a series of four enzymatic steps, the fatty acid chain is shortened by 2 carbon atoms
c) In the two oxidation steps, two molecules of NADH are formed
d) The reduced co-enzymes are re-oxidised in the mitochondrial electron transport chain
e) High rates of fatty acid degradation can inhibit glycolysis
C - In the two oxidation steps, two molecules of NADH are formed
(Because in beta oxidation 1 FADH2 and 1 NADH is formed)
- The conversion of myristoyl-CoA (14:0) to lauryl-CoA (12:0) and 1 mol of acetyl-CoA by the β-oxidation pathway results in the net formation of:
a) 1 FADH2 and 1 NADH
b) 1 FADH2 and 1 NADPH
c) 1 FADH2, 1 NADH, and 1 ATP
d) 2 FADH2 and 2 NADH
e) 2 FADH2, 2 NADH, and 1 ATP
A - 1 FADH2 and 1 NADH
During fatty acid synthesis, what molecule is directly added to fatty acid chains on the fatty-acid synthase complex?
a) Malonyl-CoA
b) Acetyl-CoA
c) Pyruvate
d) Palmitoyl-CoA
e) Citrate
A - Malonyl-CoA
How does uncoupling protein 1 (thermogenin) disrupt the ETC?
It works essentially the same as DNP but it’s our body’s natural way of producing heat in brown adipose tissue (which has a high mitochondria concentration)
How does DNP (2,4-dinitrophenol) disrupt the ETC?
- Disrupts the H+ gradient by binding to the H+ and transporting it across the membrane (DNP is lipid soluble)
- Negates ATP synthase so no ATP production. NRG lost through dissipation of heat = fatal hyperthermia
How does cyanide disrupt the ETC?
- It inhibits complex 4 (cytochrome oxidase).
- Same electronic structure as oxygen. Cytochrome is a haem type molecule.
- Binds to Fe atom & destroys its redox potential
… therefore = inhibition of complex 4
How does oligomycin disrupt the ETC?
- It inhibits ATP synthase
- Inhibits F0 and so the flow of H+ is prevented.
… therefore = No ATP synthesis
What are the 3 classes of inhibitors of the electron transport chain?
- Ones that block the flow of electrons
- Ones that block ATP synthase function
- Ones that uncouple electron transport & ATP synthesis by destroying the proton gradient
In proteins, which amino acid complexes with the iron-sulfur clusters?
Cysteine
Where does fatty acid catabolism occur?
Fatty acid to fatty acyl CoA in the cytoplasm
Fatty acyl transferase 1 & 2 transport Fatty acyl CoA to mitochondrial matrix and the rest occurs in the mitochondrial matrix.
Where does fatty acid synthesis occur?
In the cytoplasm - mainly in the liver.
How many ATPs do you get when 1 mol of NADH from glycolysis is transported to the ETC via malate-aspartate shuttle?
2.5 ATP
How many ATPs do you get when 1 mol of NADH from glycolysis is transported to the ETC via glycerol-3-phosphate shuttle?
1.5 ATP
True or false?
The citric acid cycle occurs in the cytoplasm.
False. It occurs in the mitochondrial matrix.
Name an aminase enzyme
Glutamine synthetase
Name a transaminase enzyme
Aminotransferase
Name 2 de-aminase enzymes
Glutaminase and glutamate dehydrogenase
What is the purpose of the Pentose Phosphate Pathway?
- Alternative (parallel) pathway to glycolysis.
- Synthesis of NADPH for:
- Fatty acid synthesis
- Cholesterol and nucleotide synthesis - Production of Ribose-5-phosphate for nucleic acids.
What happens to citrate when ATP levels are too high?
ATP levels high = TCA cycle off, citrate levels therefore accumulate, so citrate is exported from the matrix to the cytoplasm to be a shuttle for acetyl CoA (shuttles from matrix to the cytoplasm)