5.1 Aerobic respiration

Question 1

Spec Points

Answer 1

i Know that cellular respiration yields ATP which is used as a source of energy
for metabolic reactions, and the process also generates heat.

ii Know the different stages in aerobic respiration, including:
● glycolysis in the cytoplasm
● link reaction
● Krebs cycle
● oxidative phosphorylation in mitochondria.

Question 1

Where does glycolysis take place ?

Answer 1

• Takes place in the cytoplasm

Question 2

What does glycolysis mean ?

Answer 2

Sugar - Splitting

Question 3

What does the process of glycolysis consist of ?

Answer 3

• The splitting of a 6 carbon glucose molecule into two 3 carbon pyruvate molecules

Question 4

What is the net gain of ATP molecules during glycolysis

Answer 4

• 2 ATP molecules

Question 5

How does the glucose molecule become trapped in the cytoplasm?

Answer 5

• It is too charged due to the adding of phosphates .

Question 6

Explain the stages of glycolysis

Answer 6

1 - 6C Glucose sub primed by 2 phosphate molecules on either side of 6C glucose

2 - 6C split into two 3GP molecules, phosphates still attached.

3 - Each GP is oxidised, realising 2 H molecules which are accepted by coenzyme NAD. Therefore reducing it

4 - 4 molecules of ATP is synthesized, this is done by removing the two phosphates at the start of the process and also getting two phosphates in the cytoplasm

Question 7

What are the alternative routes of pyruvate

Answer 7

• If there is insufficient oxygen, the pyruvate is converted into lactate in animals and ethanol in plants, this is used to regenerate NAD.

Question 8

Describe the link reaction

Answer 8

• Pyruvate reacts with Coenzyme A to form Acetylcoenzyme A + CO2
• Whilst this process occurs, oxidation of NADH occurs
• Remember, there are two link reactions which take place therefore two of each molecule produced

Question 9

Where does the krebs cycle take place

Answer 9

• Mitochondrial matrix

Question 10

Describe the process of the krebs cycle

Answer 10

• Acetyl-CoA combines with 4C compound in matrix to form 6C citrate
• Citrate is decarboxylated by removal of CO2
• Citrate is then oxidised by NADH
• 5C compound is then decarboxylated by the removal of CO2
• During the conversion of 5->4C, one molecule of ATP is synthesised
• 4C Compound is Oxidised 2x by NAD to produce 2xNADH and 1x by FAD to make FADH
• 4C Compound at the end is used to start the process again

Question 11

Where does the ETC take place

Answer 11

• Inner membrane of the mitochondria (Cristae)

Question 12

Explain the role of the Krebs Cycle

Answer 12

• Completely oxidises pyruvate, to release as much energy as possible
• To generate ATP directly
• To produce NADH and FADH

Question 13

Explain the electron transport chain step by step

Answer 13

• Reduced hydrogen carriers go to cristae and split to produce electrons and hydrogen ions
• Electrons are passed down the electron carriers as they move down each electron carrier
• Electrons lose energy as hydrogen ions are transported into inner membrane space via active transport
• H+ ions then travel down conc gradient into stalked particle (ATP Synthase) where they drive the rotation of ATP synthase to produce ADP+PI into ATP

Question 14

Why do the electrons lose energy as they are transported down the carriers

Answer 14

• As they provide energy for H+ ions to move into inter membrane space via

Question 15

How does FAD differ to NAD in regards to how they are received by electron carriers

Answer 15

• FAD joins the second electron carrier, where as NAD joins the first carrier

Question 16

Describe what happens to oxygen at the end of the electron transport chain

Answer 16

• Acts as an electron accepter
• Produces water

Question 17

What is chemiosmosis ?

Answer 17

• H+ Ions are actively transported into the intermembrane space , therefore this creates a concentration gradient (move back into matix)
• They are done this by moving into stalked particles, where the chemical gradient forces ATP synthase to rotate and produce ATP