Energy and Metabolism

Question 1

Define metabolism?

Answer 1

Is defined as the sum of all chemical reactions in which energy is made available and consumed in the body.

Question 2

What is energy used for and what do we get it from?

Answer 2

We get it from the nutrients in our food
We use it for: -contraction of muscle
-accumulation of ions and other molecules against conc.  graadietns
-biosynthesis
-waste disposal
-generation of heat

Question 3

What is gibbs free energy and when is it positive and negative?

Answer 3

Gibbs free energy is the difference in energy between substrate and product.
If product contains more energy it is +.
If product contains less energy it it - .

Question 4

Define exergonic and give an eg of this reaction type?

Answer 4

-Accompanied by release of energy

EG. ATP hydrolysis to ADP + Pi

Question 5

Define endergonic and givean eg of this reaction type?

Answer 5

-Accompanied by or requiring the absorption of energy, products of greater free energy than reactants.
EG. ADP +Pi ———> ATP + H2O

Question 6

Why do all cell types need to be able to make ATP?

Answer 6

As it cant be transferred between cells.

Question 7

Describe the events of the TCA cycle?

Answer 7

• 1st reaction : Acetyl CoA condenses with oxaloacetate to produce citrate.
• Then decarboxylation phase occurs and citrate is metabolised into the 4 carbon succinyl CoA. The loss of 2 carbon molecules results in 2 CO2 molecules being formed.
• Reductive phase, where succinyl CoA is metabolised to oxaloacetate, which will be able to restart the cycle with the next acetyl CoA.
• Cycle produces just 1 ATP, but importantly makes 3NADH and 1FADH2. Which feed directly into ETC.

Question 8

Describe events of electron transport chain?

Answer 8

Electrons passed along redox centres and produce energy as they do this, this energy would enable proteins to pump proteins against conc. gradient.
NADH and FADH2 enter at different points and donate electrons and protons.

Coenzyme Q passes e- from complexs 1- and cytochrome C passes e- from complexes 3-4.

Pumping of protons causes a build up of an electrochemical gradient, molecules try and go back but the only way back is through ATP synthase which rotates and forms ATP.

Question 9

Why is complex 2 in the ETC diferent?

Answer 9

Produces ATP, to enable other complexes to pump protons across membrane, complex 2 itself does not pump protons.

Question 10

Where does Krebs cycle occur?

Answer 10

In matrix of mitochondria

Question 11

Where does ETC occur?

Answer 11

In inner mitochondrial membrane

Question 12

Describe glycolysis?

Answer 12

• Energy investment; glucose molecules broken down into two glyceraldehyde 3-phosphate molecules and this uses 2ATP.
• Energy payoff; glyceraldehyde metabolised to 2xpyruvate. We also get 4 ATP produced and 2 NADH molecules.

Question 13

Where does glycolysis occur?

Answer 13

In the cytosol

Question 14

What is the fate of pyruvate in anaerobic conditions?

Answer 14

2xPyruvate converted to 2xlactate.

NAD is regenerated from NADH to keep glycolysis going.

Question 15

What is fate of pyruvate in aerobic conditions?

Answer 15

2xpyruvate transported into mitochondrion and converted to acetyl CoA by action of pyruvate dehydrogenase.

Question 16

Describe process of fatty acid metabolism?

Answer 16

• Fatty acids and glycerol are releaded from triglyceride stores in adipose tissue via lipase enzyme action.
• Are transported in the blood as a complex with albumin and are taken up by cells for oxidation.
• They are then modified by addition of acetyl CoA to enter mitochondria, they then need to travel to inner membrane and must do so through carnitine shuttle.
• It now undrgoes beta oxidation which produces 8acetyl coA molecules and 1 NADH and one FADH2.

Question 17

Describe protein metabolism?

Answer 17

• Transamination removes amine group from amino acid and transfers it to a keto acid.
• In turn keto acid transfers its ketone group to original amino acid. New amino acid and keto acid are formed.
• This will form intermediates of Kreb’s cycle.
• Amino acids often termed glucogenic or ketogenic, whether their products ultimately form glucose or other intermediates of TCA cycle.

Question 18

What are metabolic adaptation to starvation?

Answer 18

1-Fat; triaclyglycerols in adipose tissue which can prolong life for 3 months
2-Protein; can provide energy for 2 weeks. Spared for as long as possible to permit mobility.

Question 19

How can BMR be defined?

Answer 19

Represents energy needed to maintain basic function when person is lying relaxed in normal temperature, not sleeping.
Use Hans Bendect equation to calculate.

Question 20

What is BMI and what do the values show?

Answer 20

-Can be used to measure healthy weight:
less than 20 is underweight
20-25 is ideal weight
25-30 is overweight
more than 30 is obese

Question 21

How can BMI be calculated?

Answer 21

W/H squared

Question 22

Why is BMI limited?

Answer 22

Doesnt take into account other factors such as muscle mass and CV condition.

Question 23

How does fatigue occur and when can it be a problem?

Answer 23

When our energy is imbalanced with less energy being ingested than needed.
Can be problem if it accumulatees as this can lead to chronic fatigue syndrom and immune deficiencies.