Introduction to Metabolism

Question 1

What is metabolism?

Answer 1

it is a set of chemical reactions essential for life either catabolic or anabolic

Question 2

What is a catabolic reaction?

Answer 2

They involve the breakdown of organic matter - ultimately to produce energy by cellular repiration

Question 3

What is anabolic reactions?

Answer 3

the synthesis of complex compounds essential for life but which consume energy

Question 4

What are the steps of anabolism?

Answer 4

1) form precursors
2) form complex molecules from simple precursors
3) link these complex molecules together

Question 5

What are the stages of catabolism?

Answer 5

1) hydrolysis of complex molecules to their component building blocks
2) conversion of building blocks to acetyl CoA (or other simple intermediate)
3) oxidation of the simple intermediate

Question 6

What are our energy sources?

Answer 6

ATP = high energy phosphate group

NADH = high energy electrons - reducing power

NADPH = high energy electrons with reducing power

Question 7

How does the body ‘use’ ATP?

Answer 7

the hydrolysis of ATP into ADP gives the energy necessary to complete energetically unfavorable reactions

Question 8

What is free energy?

Answer 8

change in free energy is the energy available to do work- it predicts whether a reaction is favorable or not

Question 9

If change in free energy is positive, does that mean the reaction is unfavorable or favorable?

Answer 9

if delta G is positive, then it is an unfavorable reaction - it requires energy to go forward (endergonic reaction)

Question 10

If change in free energy is negative, does that mean the reaction is unfavorable or favorable?

Answer 10

that means the reaction is favorable = the biological process releases energy - it is exergonic

Question 11

Does Glucokinase require ATP to convert glucose to glucose 6 phosphate?

Answer 11

Yes

Question 12

How does NADH fuel unfavorable reactions?

Answer 12

indirectly- NADH goes through the Eletron transport chain contributing to the proton gradient that ATPase uses to make ATP -

The ATP is then used to fule unfavorable reactions

Question 13

What regulates energy metabolism?

Answer 13

Feedback inhibiton- ex, NADH can inhibit enzymes that produce it, and NAD+ can stimulate them

Phosphorylation/Dephosphorylation - ex. pyruvate dehydrogenase

Availability of intermediates- availability of oxaloacetate regulates citrate synthase activity

Oxygen availability - hypoxia/anoxia- leads to failure of oxidative phosphorylation

Question 14

What are the consequences of impaired enzyme action?

Answer 14

1) accumulation of substrate
2) deficiency of product
3) diversion to alternate product