Citric Acid Cycle and Terminal Respiration Flashcards
What is the purpose of the citric acid cycle?
To generate NADH, FADH, carrying electrons for later on
How many dehydrogenase reactions occur in the cycle?
4 out of the 8
What are the net products of one cycle?
3 NADH, 2 Co2, 1 FADH2, 1 GTP
What is the first step of the citric acid cycle?
Oxaloacetate and acetyl CoA bind, and CoA is released, forming citrate.
How is the rate of the cycle regulated?
When ATP or NADH levels are high, the cycle is slowed down as we don’t need more energy.
When ADP or NAD+ levels are high, the cycle speeds up as we need energy.
What other compound can lead to the formation of Acetyl CoA and why?
Fatty acids. Because when our glucose levels are low glucagon levels rise and break down triglycerides into fatty acids
What is the role of insulin?
Insulin regulates our blood sugar level, breaking down sugar into Glc, Fru and Gal
What is the role of glucagon? (2)
Stimulates liver to break down glycogen into glucose. Breaks down triglycerides into fatty acids
What are other names of the citric acid cycle?
Krebs cycle and Tricarboxyllic acid cycle
Where does the citric acid cycle occur?
Mitochondrial matrix
How much ATP in total is formed per glucose molecule from products in the Krebs cycle?
24 ATP molecules. 12 in each pyruvate/Acetyl CoA
Does the Krebs cycle produce any ATP or O2 directly?
No. Electron carriers use electrons taken from the cycle later to form o2 and ATP
Which enzyme converts pyruvate to Acetyl CoA?
Pyruvate dehydrogenase
Which process is the conversion of Pyruvate to Acetyl CoA a part of?
Neither glycolysis nor citric acid cycle
What is the purpose of the citric acid cycle?
Oxidising Acetyl CoA, releasing CO2 and harvesting electrons along the way
What stimulates/inhibits pyruvate dehydrogenase?
High ADP and NAD+ stimulates it. High Acetyl CoA, ATP and NADH inhibit it
Where does inhibition of enzymes used in the cycle occur?
At parts of the cycle where CO2 is produced - Decarboxylation.
Define amphibolic in terms of the cycle
A pathway which serves both anabolic and catabolic processes.
What other products are formed in the cycle and how do they effect the cycle when taken out+ solution?
Proteins, Heme groups and nucleotide bases can be produced from the products of the cycle. However this reduces Oxaloacetate levels, so pyruvate must be converted directly to oxalacetate during gluconeogenesis to restore its levels and allow the cycle to continue.
What occurs during terminal respiration?
Electrons enter oxidative phosphorylation, producing H2O and ATP
How many protein complexes are involved in the electron transport chain?
4
What occurs in complex 1 of ECT?
NADH gives electron to flavin mononucleotide, sending NAD+ back to other processes
How do electrons from NADH enter the mitochondrial matrix?
Membrane is impermeable so G3P shuttle takes it to FAD in cell and forms FADH2
What are the three ways in which NADH and FADH2 are synthesised?
Glycolysis, citric acid cycle, oxidation of fatty acids in mitochondria
What occurs at complex II?
Succinate dehydrogenase enzyme takes electron from FADH2
Where do the taken electrons from Complexes 1 and 11 go?
Ubiquinone - a lipid structure
What do cytochromes do and what do they include?
They are proteins with heme groups and Fe2+, which accept protons and become Fe3+ before releasing them to the next complex and returning to Fe2+. Includes complex 3, cytochrome C and complex 4
What is Complex 3 made from?
Cytochrome b and c1
What is complex 4 made from?
Cytochrome a and a3, or known as cytochrome oxidase
What happens to the proton gradient as electrons are pushed through the ETC?
Protons are pushed out the matrix, creating a gradient for them to want to come in. The membrane is impermeable, so they must go through protein channels
How do protons return to the matrix?
Pass through F0 which is attached to enzyme F1, ATP synthase.
How many molecules of ATP can be synthesised by NADH and FADH2?
NADH can synthesise 3 as hydrogen is released at complexes 1, 3 and 4. FADH2 can synthesise only 2 as h+ is only released at complexes 3 and 4
What controls the rate of oxidative phosphorylation?
ATP rises, rate decreases. ADP rises, rate increases
How does ADP/ATP travel in/out the cell?
ADP/ATP antiport
What are the 2 ways that chemicals/drugs can affect oxidative phosphorylation?
Uncoupling and inhibition
Explain uncoupling in oxidative phosphorylation
Alternate h+ proton pump is placed on membrane so H+ can flow back in without the ATPase or F0 pump
Explain inhibition in oxidative phosphorylation
One of the complexes is inhibited, so no electrons can pass through, preventing H2O from being made and ATP cannot be synthesised. Metabolism slows down
