Oxidative Phosphorylation

Question 1

What happens to the hydrogen atoms from the Krebs cycle?

Answer 1

The are carried by the coenzymes NAD and FAD into oxydative phosphorylation

Question 2

What are available in the cristae?

Answer 2

Proteins, lipids, traces of DNA and the enzymes and proteins needed for oxidative phosphorylation

Question 3

What is the site of oxidative phosphorylation?

Answer 3

The cristae

Question 4

Where do the mitochondria occur most frequently?

Answer 4

In metabolically active cells such as the liver, muscles and epithelial cells. Which all carry out active transport

Question 5

What is different about the mitochondria in metabolically active cells?

Answer 5

The cristae are more densely packed, allowing for a greater surface area of membrane incorporating enzymes and other proteins involved in oxidative phosphorylation

Question 6

How is the ETC formed?

Answer 6

The electrons from the Krebs cycle are transferred down a series of electron carriers which together form the ETC

Question 7

What happens to the reduced NAD and FAD?

Answer 7

They donate the electrons of the hydrogen atoms they are carrying to the first molecule in the ETC

Question 8

What happens to the electrons as they pass along the ETC?

Answer 8

They pass along the ETC in a series of oxidation-reduction reactions

Question 9

What is released as electrons pass down the ETC?

Answer 9

Energy

Question 10

What does the energy released from the ETC cause?

Answer 10

The active transport of protons across the inner mitochondrial membrane and into the inter-membrane space

Question 11

What happens to the protons in the inter-membranal space?

Answer 11

They accumulate, before they diffuse back into the mitochondrial matrix through ATP synthase channels embedded in the inner mitochondrial membrane

Question 12

What happens to the electrons at the end of the chain?

Answer 12

They combine with the protons that just diffuse through the ATP synthase channels and oxygen to form water

Question 13

What is the final electron acceptor in the ETC?

Answer 13

Oxygen

Question 14

What is the theory that describes the ETC?

Answer 14

Chemiosmotic theory

Question 15

What would happen if oxygen wasn’t there to accept the hydrogen atoms?

Answer 15

The hydrogen ions and electrons would ‘back up’ along the chain and respiration would come to a halt

Question 16

Why are electrons passed down a chain and not passed at once

Answer 16

The greater the energy that is released in a single step, the more of it is released as heat and then less is available for useful purposes

Question 17

What is significant amount electron carrier molecules in the ETC?

Answer 17

Each carrier is at a slightly lower energy level therefore the electrons move down a gradient allowing their energy to be released gradually

Question 18

What are the alternative respiratory substrates?

Answer 18

Lipids and proteins

Question 19

How are lipids respired?

Answer 19

• they are first hydrolysed to glycerol and fatty acids
• the glycerol is then phosphorylated to triose phosphate which can enter the glycolysis pathway and then the Krebs cycle
• the fatty acid is broken down into 2-carbon fragments which are converted to acetyl coenzyme A

Question 20

What does the oxidation of lipids produce?

Answer 20

2-carbon fragments of carbohydrate and hydrogen atoms which are used to produce ATP in oxidative phosphorylation

Question 21

Compared to carbohydrates, how much energy is released from respiring a lipid molecule?

Answer 21

More than double

Question 22

How are proteins respired?

Answer 22

• they are first hydrolysed to amino acids
• amino acids have their amino group removed in the process of destination before entering the Krebs cycle depending on the number of carbons they contain

Question 23

When respiring proteins, what happens to the different carbon length molecules?

Answer 23

• 3-carbon molecules are converted to pyruvate

- 4- and 5-carbon compounds are converted to intermediates in the Krebs cycle

Question 24

Why is the term oxidative phosphorylation used to describe the ETC?

Answer 24

The movement of electrons along the ETC is due to oxidation and the energy from the electrons combines with inorganic phosphate and ADP to form ATP in phosphorylation

Question 25

State one advantage of the folding of the cristae on the ETC

Answer 25

It provides a large surface area of membranes which incorporate the coenzymes NAD and FAD and electron carriers that transfer electrons along the chain

Question 26

Explain the role of oxygen in aerobic respiration

Answer 26

Oxygen is the final acceptor of the electrons and hydrogen ions in the ETC, without it, electrons would accumulate along the chain and respiration would cease

Question 27

As part of what molecule does oxygen leave as after being respired?

Answer 27

Water molecule