Chapter 8- Cellular metabolism (2)

Question 1

Where does the Krebs cycle take place?

Answer 1

Inside the mitochondrial matrix

Question 2

Citric acid cycle reactions oxidise what?

Answer 2

The remaining acetyl fragments of Acetyl-CoA to C02.

Question 3

The energy released from the oxidation of the remaining acetyl fragments is used to do what?

Answer 3

Reduce Coenzymes (NAD and FAD) and phosphorylate ADP to ATP.

Question 4

For each turn of the Krebs cycle, what is formed?

Answer 4

1- 2 carbons enter in the acetyl fragment of acetyl-CoA.

2- 2 separate carbons are oxidized and leave as CO2

3- Electron carriers are reduced: 3 NADH and 1 FADH2 are produced.

4- 1 molecule of GTP is produced

Question 5

What are carriers of high energy electrons and what are its uses?

Answer 5

NADH and FADH2 produced by the krebs cycle, transition reaction, and glycolysis

These electrons are used to reduce molecular oxygen to water giving a large amount of free energy.

This free energy is used to generate ATP.

Question 6

What is the process of oxidative phosphorylation?

Answer 6

The process in which ATP is formed as a result of the transfer of electrons from NADH or FADH2 to oxygen by a series of electron carriers.

Question 7

During oxidative phosphorylation, how are the electron carriers NADH and FADH2 reduced?

Answer 7

By the loss of their electrons whose energy is transferred into the ATP.

This is the major source of ATP in aerobic respiration.

Question 8

Electrons flow from NADH or FADH to O2. What does it occur through and what does it lead to?

Answer 8

This occurs through protein complexes on the inner membrane of the mitochondria.

This leads to pumping of protons out of the mitochondrial matrix through an electrochemical gradient.

ATP is then synthesised when protons flow back through the mitochondrial matrix through an enzyme called ATP synthase.

ATP synthase is used to restore the proton gradient.

Question 9

What is the overall equation for aerobic respiration?

Answer 9

Glucose + 6O2 = (arrow) 6CO2 + 6H2O+ 36 ATP’s

Question 10

When glucose availability exceeds the need for ATP, glucose energy is stored as what?

Answer 10

Glycogen

Question 11

Glycogen synthesis is also known as…

Answer 11

Glycogenesis

Question 12

Where is glycogen stored?

Answer 12

Liver and skeletal muscle cells

Question 13

Glucose storage is stimulated by what?

Answer 13

Insulin

Question 14

When is insulin secreted into the blood?

Answer 14

When blood glucose levels are high

Question 15

Glycogen breakdown is also known as what?

Answer 15

Glycogenolysis

Question 16

Where does glycogenolysis take place?

Answer 16

Liver

Question 17

What hormone stimulates glycogenolysis?

Answer 17

Glucagon

Question 18

When is glucagon secreted?

Answer 18

When blood glucose levels are low

Question 19

What is protein breakdown known as?

Answer 19

Proteolysis

Question 20

Polypeptides break down into amino acids through what process?

Answer 20

Hydrolysis

Question 21

What is deamination?

Answer 21

This is the removal of NH3 which is the amino group from a molecule.

Question 22

What does NH3 form and how is it removed?

Answer 22

NH3 forms ammonia which toxic and is removed from the body through urea.

Question 23

What is the remaining part of the carbon skeleton (keto acid) used for?

Answer 23

It can be used to make ATP

Question 24

What is the process of catabolism of lipids? (lipid metabolism)

Answer 24

1- Triglyceride is broken down into 3 fatty acids and glycerol when it is hydrolysed.

2- Beta oxidation- oxidation of fatty acid chains

• The reactive group of the fatty acid can bind to coenzyme A
• This initiates a cleavage of the 2 carbon chains at the end of the fatty acid chain.
• This then forms AcetylCoA which can then enter the Krebs cycle.

Question 25

What is gluconeogenesis?

Answer 25

This is when glucose can be formed from non-carbohydrate building blocks.

Question 26

Give an example of gluconeogenesis?

Answer 26

Breaking down proteins into keto acids which are carbon skeletons from the amino acid breakdown. Some of these carbon skeletons can then be converted into glucose.

This process occurs in the liver and is stimulated in times of great need.