L05 & L06 - METABOLISM

Question 1

What is a catabolic pathway?

Answer 1

Break down complex molecules into simple molecules and release energy

Question 2

What is an anabolic pathway?

Answer 2

Form a complex molecule from smaller simple molecules. Requires energy usually in the form of ATP

Question 3

What are the products of glycolysis?

Answer 3

• 2 net ATP
• 2 NADH

Question 4

What are the products of pyruvate decarboxylation?

Answer 4

• CO2
• NADH

Question 5

What complex regulates pyruvate decarboxylation and how is the complex regulated?

Answer 5

• PDH complex
• Regulated by feedback which influences kinases
• Has an active and inactive form
• Increase in pyruvate –> increase in the kinase that activates the enzyme
• Increase in acetyl CoA –> increase in the enzyme that deactivates the kinase

Question 6

What are the products of the TCA cycle?

Answer 6

One molecule of pyruvate:

• 3NADH
• FADH2
• GTP
• 2CO2

Question 7

What is the energy usage of gluconeogenesis in order to produce 1 glucose molecule

Answer 7

• 4ATP
• 2NADH
• 2 GTP
• 2 Pyruvate

Question 8

Give two other molecules that are not pyruvate that can be used to form Acetyl CoA

Answer 8

• Fatty acids
• Amino acids

Question 9

Where does glycolysis occur?

Answer 9

Cytosol

Question 10

What are the 3 irreversible steps in glycolysis?

Answer 10

1, 3 and 10

Question 11

What is the enzyme that catalyses step 3 in glycolysis?

Answer 11

Phosphofructokinase

Question 12

Name the main enzyme in glycolysis and the main enzyme in gluconeogenesis

Answer 12

• Phosphofructokinase
• 1,6 - bisphosphatase

Question 13

When is phosphofructokinase switched on and when is it switched off?

Answer 13

• Switched on when ATP is low
• Switched off when ATP is abundant

Question 14

In the TCA cycle, which molecule are the carbon atoms lost from?

Answer 14

Lost from the oxaloacetate molecule

Question 15

What is NAD derived from and what does it act as?

Answer 15

• Vitamin B3 (Vitamin Niacin)
• acts as a coenzyme

Question 16

What is FAD derived from?

Answer 16

• Vitamin B2

Question 17

What are anaplerotic reactions, give 3 examples?

Answer 17

• Reactions that fill in missing metabolites for important metabolic pathways
• Direct conversion of pyruvate to oxaloacetate
• Oxaloacetate/ aspartate conversion which is important for malate/ aspartate shuttle
• Malate to pyruvate conversion

Question 18

What catalyses the transport of electrons in the ETC and what can it be inhibited by?

Answer 18

• Cytochrome C
• Inhibited by cyanide, carbon monoxide and azide

Question 19

Explain how new borns generate heat energy.

Answer 19

They use brown adipose tissue - this is more rare compared to white adipose tissue.

The membrane has an uncoupling protein channels. When H+ is transported into the inner membrane, the uncoupling protein transports them back into the cytosol. The energy stored in the electrochemical gradient will be released at heat energy

Question 20

Which enzyme converts pyruvate to acetyl choline?

Answer 20

pyruvate dehydrogenase

Question 21

Give 3 ways metabolism is controlled

Answer 21

• Enzyme levels
• Enzyme activities
• Substrate availability

Question 22

What inhibits the control points of the TCA cycle?

Answer 22

• ATP
• NADH
• Acetyl CoA