Process of Cellular Respiration (HL) Flashcards
What are electron carriers?
Electron carriers are molecules involved in respiration that accept or donate their electrons. NAD+ and FAD are electron carriers, they are oxidizing agents
Write the redox reactions of NAD+ and FAD:
NAD+ + 2e- + 2H+ –> NADH + H+
NADH –> NAD+ + 2e- + 2H+
FAD + 2e- + 2H+ –> FADH2
FADH2 –> FAD + 2e- + 2H+
What is phosphorlyation and what does it do to a molecule?
Phosphorylation is when a phosphate ion is added to a molecule, it makes the molecule less stable and more reactive or “activates” it. Phosphorylation is endergonic (endothermic)
Example: phosphorylation of
Adenosine diphosphate (ADP) to Adenosine triphosphate (ATP)
What are the 2 types of phosphorylation? Describe them briefly and where do they occur?
- Substrate-level phosphorylation, which is when a phosphate ion is added from a donor molecule/compound (this happens in glycolysis and the Krebs cycle)
- Oxidative Phosphorylation, which is when phosphorylation is coupled with oxidation (this happens in the electron transport chain)
What is the name of the process in which a phosphate ion is removed from ATP, and is it exergonic or endergonic?
Hydrolysis, dephosphyrlation is exergonic since it releases energy
What is the main respiratory substrate in respiration?
Glucose
what are the stages involved in aerobic respiration in order
and what are the stages involved in anaerobic respiration in order?
Aerobic: 1. Glycolysis, 2. Link Reaction,
3. Krebs Cycle, 4.Oxidative Phosphorylation
Anaerobic: 1. Glycolysis, 2. Fermentation
(Anaerobic respiration stops at glycolysis, this is why it only produces 2 molecules of ATP while aerobic produces 36)
Where does each stage of aerobic respiration occur?
Glycolysis: Cytoplasm
Link reaction: Matrix of mitochondria
Krebs Cycle: Matrix of Mitochondria
Oxidative phosphorylation: involves the electron transport chain and chemiosmosis and occurs at the inner membrane of the mitochondria
What are the 4 main stages of glycolysis in detail? (7 marks)
- Phosphorylation:
Glucose + 2ATP —> Fructose-1,6-biphosphate
- Lysis: Splitting of Fructose to 2 triose phosphate
Fructose-1,6-biphosphate —> 2 Triose phosphate
- Oxidation:
dehydrogenase enzyme removes H from each molecule of triose phosphate, then each triose phosphate is oxidized to form another 3 carbon molecule which is glycerate-3-phosphate
2 Triose phosphate →2 Glycerate-3-phosphate
4H + 2NAD → 2NADH + 2H+
- Dephosphorylation: Phosphates are transferred from the intermediate substrate molecules to form four ATP through substrate-linked phosphorylation
4 Phosphate group+ 4ADP → 4ATP
This results in the production of pyruvate
2 Glycerate-3-phosphate → 2 Pyruvate
4 ATP molecules are produced in total, but 2 are used in phosphorylation as well so a net of 2 are produced
Describe and explain the Link Reaction in detail
The link reaction links glycolysis to the krebs cycle
It starts with oxidative decarboxylation, which produces CO2 by removing a carbon from each pyruvate molecule and results in 2C molecule
The 2C molecule is then oxidised (dehydrogenation) to produce an acetyl compound, hereby reducing NAD+ to NADH
The acetyl compound combines with coenzyme A and forms acetyl coenzyme A
pyruvate + NAD + CoA → acetyl CoA + carbon dioxide + reduced NAD
What is a coenzyme?
A coenzyme is a non protein molecule that helps an enzyme carry out its function and is not used up in the reaction.
Describe and explain the krebs cycle in detail
*The krebs cycle (sometimes called the citric acid cycle) is a series of enzyme controlled reactions
*2 two carbon acetyl coenzyme A (CoA) molecules enters the cycle to meet a 4C compound, the 4C compound accepts the 2C acetyl CoA fragments to form a 6 carbon molecule
*The 6C molecule is decarboxylised to form 2 CO2 molecules as waste gas
*Hydrogen atoms are released by the oxidation of the 6C compounds
*NAD+ and FAD are reduced by these hydrogen atoms:
3 NAD+ and 1 FAD → 3NADH + H+ and 1 FADH2
*One ATP is formed by Substrate-level phosphorylation, a phosphate group from an intermediate molecule is added to a molecule of ADP
What is oxidative phosphorylation (the final stage of aerobic respiration) comprised of?
The electron transport chain, and chemiosmosis
What is an example of a Coenzyme used in respiration?
NAD+ and FAD
How many reduced NAD+ and FAD are produced in different stages of respiration from one glucose molecule?
NAD+:
Glycolysis: 2
Link reaction: 2
Krebs cycle: 6
FAD:
Krebs cycle: 2
NOTE: at all stages there is a doubling (2x) of reduced NAD and FAD. This is because one glucose molecule is split in two in glycolysis and so these reactions occur twice per single molecule of glucose.
