Metabolism Fuel Selection

Question 1

Muscle contractions use ______ to fuel the _____ and ______ interaction. What happens to the rate of use of ATP if the contraction is faster?

Answer 1

ATP. Actin and myosin. The rate of use increases.

Question 2

At rest, why would the muscles be using ATP?

Answer 2

To maintain ion gradients

Question 3

What should the concentration of ATP be? What is it goes below a certain concentration?

Answer 3

5mM. If it goes below 3mM the cells die.

Question 4

What happens if a cell stops doing work?

Answer 4

ADP is not formed causing the rate of proton movement into the matrix to decrease and there is no regeneration of carriers.

Question 5

The rate of ATP synthesis is exactly matched to ______?

Answer 5

ATP use

Question 6

During gentle exercise does the rate of ATP generation need to be increased?

Answer 6

Yes

Question 7

How can we increase the rate of ATP?

Answer 7

Through greater availability of ADP:
Increase ATP synthase
Dissipate the proton gradient
Increase electron transport
Increase availability of h/e strippers
Fuel oxidation can increase

Question 8

During exercise what can happen to fatty acids?

Answer 8

Fatty acids can liberate a lot of NADH as carbon atoms in them contain a lot of reduced carbon.

Question 9

Why isn’t glucose stored in as much excess as fat?

Answer 9

Major storage is glycogen and it is a long polymer and very hydrophilic which is heavy and takes up a lot of space.

Question 10

What is the most readily available pathway of fuel oxidation?

Answer 10

Most readily available is glucose as glucose transporters are on the cells surface.

Question 11

What is an important consideration when using glucose for energy?

Answer 11

Use will lower blood glucose and so glucose homeostasis is needed to keep at 5mM. Insulin down and glucagon up.

Question 12

During exercise what happens to the Krebs cycle?

Answer 12

Increase in activity to provide more NADH for the electron transport chain.

Question 13

What are some of the things that increase during exercise?

Answer 13

INcrease in enzymes for glycolysis and puruvate. Rise in levels of glucose transporters which live in Golgi apparatus and move to the cell surface when exercise is commenced.

Question 14

Effects of low insulin and high glucagon? How long does this take to happen?

Answer 14

Stimulation of glycogen breakdown in liver and fat breakdown in adipose tissue. 5-10 minutes.

Question 15

Why do we recycle glucose?

Answer 15

Glucose stores are limited and we cant convert fatty acids into glucose.

Question 16

How do we conserve glucose?

Answer 16

Fatty acids substitute glucose for fuel and prevent glucose from being wastefully oxidised. Glucose entering the cycle goes to lactate instead.

Question 17

What is the sequence of events of which fuels will be burnt by the body in light exercise?

Answer 17

Initially glucose.
After several minutes fatty acids take over released from the adipose tissue.
Glucose still gets into the muscles - but only taken as far as lactate.
Lactate goes to the liver for resynthesis for glucose (gluconeogenesis).

Question 18

During moderate exercise what are the effects of increased consumption of ATP?

Answer 18

Enzymes in krebs cycle and fatty acid to carbon dioxide increase. The enzymes that catalyse fatty acid oxidation quickly reach maximum capacity.

Question 19

During moderate exercise fatty acid oxidation alone cant maintain ATP production so what happens?

Answer 19

Inhibition of glucose oxidation is removed. Glucose oxidation occurs so there is less glucose recycling and liver glycogen stores are depleted faster.

Question 20

During moderate exercise, if the increase in pace occurs what else increases?

Answer 20

Glucose oxidation as fatty acid oxidation is already at full capacity.

Question 21

During strenuous exercise what are the limits on oxidation?

Answer 21

Speed of oxidation of blood glucose as the rate of supply and transport from blood cant keep up.

Question 22

What happens during strenuous exercise to muscle glycogen?

Answer 22

It is broken down.

Question 23

What are the demands of the most strenuous exercise.

Answer 23

ATP production cant be met by oxidative phosphorylation and so need to top up with glycolysis. Very inefficient and blood lactate levs will rise. This glucose must come from the muscle as transport from liver is at max.

Question 24

When glycogen has run out what is used for ATP production?

Answer 24

Fatty acid oxidation.

Question 25

You cannot perform what exercise if there is no glycogen.

Answer 25

Sprinting

Question 26

What type of muscles does sprinting use? What are the features of this muscle type?

Answer 26

Type 2b. Poor blood supply, lots of contractile filaments, few mitochondria and very rapid consumption of ATP

Question 27

Why can’t you use fatty acid or blood glucose for energy while sprinting?

Answer 27

Fatty acid poor oxygen supply and blood glucose as there is a delay in transporter recruitment and so poor fuel supply.

Question 28

What is used for energy for sprinting? What are the issues associated with the use of muscle glycogen?

Answer 28

Muscle glycogen. It is very fast but creates an issue of regeneration of the h/e- carrier. ATP generation is inefficient and so only 2ATP per glucose. Lots of lactate is made

Question 29

How can the body ‘buy time’ while waiting for glycogenolysis to begin?

Answer 29

Creatine phosphate is an instant store of ATP which can be released for quick energy - 5 seconds but enough.