ATP & Respiration (DONE) Flashcards
What is ATP, giving the function and structure of ATP in your answer.
(3 marks)
- Nucleotide
- Used in muscle contraction, DNA/RNA/protein synthesis, active transport, movement of chromosomes during mitosis and meiosis and nerve transmission.
- Made up of ribose sugar, 3 phosphate groups and an adenine base
Why is ATP often referred to as the ‘universal energy currency’?
Used by all organisms to provide energy for all reactions in all cells.
Describe the reversible reaction of ATP to
ADP +Pi.
- ATP is catalysed by ATPase into ADP + Pi. This is an exergonic reaction and a hydrolysis reaction.
- ADP is catalysed by ATP synthase. This is an endergonic reaction and a condensation reaction.
How much energy is released from 1 phosphate group in ATP in every molecule of ATP?
30 kJ per mol
What is the importance of ATP as an energy carrying molecule?
(4 marks)
- ATP is released slowly and not all at once, otherwise there would be too much energy wasted and heat produced would damage cells
- Only 1 enzyme needed to catalyse ATP
- 1 Step reaction
- ATP can’t be transported from cell to cell
Describe in full detail the process of glycolysis.
(6 marks)
- Takes place in the cytoplasm and is anaerobic meaning it requires no oxygen
- 2 ATP is required for the phosphorylation of glucose to form hexose bisphosphate
- Hexose bisphosphate is unstable and forms two molecules of triose phosphate (TP).
- Each TP molecule loses two hydrogen atoms by dehydrogenation catalysed by dehydrogenase
- The hydrogen atoms are picked up by NAD forming NADH2 for each TP molecule (2 in total)
-TP is converted into pyruvate (3 carbons) by the substrate level phosphorylation, which also releases 2 molecules of ATP per TP molecule
What are the net products of glycolysis?
(3 marks)
- 2 x Pyruvate
- 2 NADH2
- 2 ATP molecules (net)
What is meant by substrate level phosphorylation
- ADP + Pi join to form ATP
- The energy is derived directly from a reaction
Describe in full detail what occurs in the Link reaction.
(4 marks)
- Pyruvate diffuses down a concentration gradient into the mitochondrial matrix
- It is decarboxylated by decarboxylase, releasing carbon dioxide
- It is dehydrogenated by dehydrogenase, release two hydrogen atoms, which are picked up by NAD to be reduced into NADH2
- Acetate/acetyl is formed which attaches to Coenzyme A to form acetyl Coenzyme A.
What is the Krebs Cycle, what can it be known as, where does it take place and what are the products after 2 cycles?
- Series of enzyme controlled oxidation-reduction reactions
- Citric Acid cycle
- In the mitochondrial matrix
Products are: - 2 Coenzyme A - 4 CO2 (diffuse out)
- 2 ATP (substrate level) - 2 FADH
- 6 NADH
Describe/Draw the steps of the Krebs Cycle
(6 marks)
Refer to booklet for diagram
- Acetyl Coenzyme A enter Krebs cycle from link reaction and combines with a 4C compound (oxaloacetate) to form a 6C compound
- At the same time coenzyme A is regenerated
- 6C compound is decarboxylated and dehydrogenated (reducing NAD) to a 5C compound
- 5C compound is decarboxylated, dehydrogenated (reducing NAD) to a 4C compound. Substrate level phosphorylation occurs generating 1 ATP
- 4C compound is dehydrogenated (reducing FAD to FADH2 this time) to another 4C compound
- 4C compound is dehydrogenated (reducing NAD) to oxaloacetate (OOA) a 4C compound
How does cyanide prevent aerobic respiration?
(5 marks)
- Non-competitive respiratory inhibitor
- Binds to the final electron carrier of oxygen
- Prevents electrons and protons passing to the oxygen to form water
- Prevents the proton gradient forming between the inter-membrane space and matrix
- Chemiosmosis stops and no ATP is produced from the ETC/ no energy derived from oxygen
Why does aerobic respiration happen and what is the effect of it?
(4 marks)
- There is insufficient oxygen in the cell to act as the final electron acceptor
- NADH and FADH can not release hydrogen/re oxidised and so can not accept Hydrogen from Krebs or Link
- Krebs/Link stop
- Aerobic respiration only carries out glycolysis in the cytoplasm.
How does aerobic respiration occur in animal cells?
(4 marks)
- Glycolysis
- NADH passes its hydrogen atoms to pyruvate; NAH is regenerated for TP
- Pyruvate becomes the final electron acceptor
- Lactic acid/lactate is formed
How does aerobic respiration occur in yeast?
(4 marks)
- Pyruvate is decarboxylated via decarboxylase
- Forms ethanal and releases carbon dioxide
- NADH passes 2*Hydrogen atoms to ethanal to form ethanol.
- NAD is regenerated
