Week 7: Post Absorptive Metabolism

Question 1

What is an example of nutrients being converted from on form to another?

Answer 1

Fat can be obtained directly from food, or synthesised from protein or CHO

Question 2

Glycogen as an energy store?

Answer 2

Needed in a hurry stored in the form of CHO

Question 3

Fat as an energy store?

Answer 3

Huge energy reserve, can be stored in kg quantities

Question 4

ATP is?

Answer 4

Adenosine triphosphate - present in every cell and contains three phosphate bonds, two of which are high-energy bonds

Question 5

What is phosphocreatine?

Answer 5

Creatine phosphate - in muscle used to transfer phosphate group to ADP during contraction

Reformed during recovery or when ATP in excess

Question 6

Flight or fright response is what?

Answer 6

When the body has stored enough ATP and creatine phosphate to supply energy for only a few seconds

Question 7

What happens when glucose enters the cell?

Answer 7

It is converted into glucose - 6 - phosphate by glucokinase or hexokinase enzymes

Question 8

What does the liver do to glucose 6 phosphate?

Answer 8

Can convert it back to glucose as it has phosphate enzymes

Question 9

What are the 4 possible fates of glucose?

Answer 9

1. Aerobic metabolism to generate energy when oxygen is available
2. Anaerobic metabolism to generate energy when oxygen is limited
3. Glycogen synthesis to provide a short term energy store
4. Fat synthesis as a long term energy store

Question 10

What is stage 1 of aerobic glucose metabolism?

Answer 10

Glycolosis.

• occurs in the cell cytoplasm
• conversion of glucose to glucose 6 phosphate then to 2 pyruvate molecules

Produces: 2 ATP and 4H

Question 11

What is stage 2 of aerobic glucose metabolism?

Answer 11

The conversion of pyruvate to acetyl coA
- after the facilitated transport of pyruvate into the mitochondria by a carrier protein.

Produces 4H but no ATP

Question 12

What is stage 3 of aerobic glucose metabolism?

Answer 12

The citric acid cycle KREBS CYCLE

- occurs in the mitochondria and produces 16H and 2ATP

Question 13

What is stage 4 of aerobic glucose metabolism?

Answer 13

Oxidative phosphorylation

• occurs in mitochondria to capture energy from the H atoms and store it as ATP.
• involves the H carrier molecule NAD+
• needs O2

Produces water and 34ATP

Question 14

What is the total ATP produced from aerobic glucose metabolism??

Answer 14

38 ATP

Question 15

What limits the amount of glucose taken up by a cell?

Answer 15

Insulin and the capacity of the glucose carrier molecules

Question 16

What does insulin stimulate?

Answer 16

Glycogen synthesis

Question 17

Does conversion of glucose to pyruvate require oxygen?

Answer 17

No

Question 18

what two different fates can pyruvate undergo?

Answer 18

Depending on availability of O2 within the cell, pyruvate can undergo aerobic or anaerobic metabolism

Question 19

What is produced from anaerobic metabolism?

Answer 19

Lactic acid

Question 20

Why cant cells stored large amounts of glucose in solution?

Answer 20

Cells would rupture due to high osmotic pressure

Question 21

What happens in glycogenesis?

Answer 21

Glucose - glucose 6 phosphate - glucose 1 phosphate - uridine diphosphate glucose - glycogen

Question 22

What happens to excess glucose?

Answer 22

Converted to fat for long term storage

energy for this process is supplied by the pentose phosphate pathway

Question 23

What is the Pentose Phosphate Pathway?

Answer 23

An independent and cyclical pathway that occurs in liver and fat cells

Question 24

What happens on each cycle of the penthose phosphate pathway?

Answer 24

6 molecules of glucose enter the pathway and 5 come out (5-C sugar) with one CO2 and H

H atoms can be oxidised to give ATP but normally are used in fat synthesis

Glucose - acetyl coA - fatty acids - triglycerides

Question 25

What happens if free fatty acids are taken up by the liver?

Answer 25

Three different fates:

1. patrial breakdown for transport out of the liver as smaller free fatty acids (catabolism)
2. complete breakdown to provide energy (catabolism)
3. conversion to triglycerides for storage (anabolism)