Week 2 - Bioenergetics and Exercise Metabolism

Question 1

Bioenergetics

Answer 1

Flow and exchange of energy within a living system.

The conversion of food (fats, proteins, carbohydrates) into usable energy for cell work (chemical –> mechanical).

Question 2

Metabolism

Answer 2

sum of all the chemical reactions that occur in the body (anabolic and catabolic).

Question 3

Explain the two types of reactions in the body.

Answer 3

1) Anabolic reactions: synthesis of molecules (glucose being stores as glycogen)

2) Catabolic reactions: release of chemical energy through the breakdown of molecules to simpler molecules (glycogen broken down into glucose)

Question 4

What is the difference between endergonic and exergonic chemical reactions?

Answer 4

Endergonic
> requires energy to be added to the reactants
> Ex: Glycogen formation or ATP synthesis
> Overall increase in energy
> Energy in products greater than reactants

Exergonic
> releases energy
> Ex: ATP hydrolysis
> Overall decrease in energy
> Energy in reactants greater than products

Question 5

Coupled reactions

Answer 5

Liberation of energy in an exergonic reaction drives an endergonic reaction.

Question 6

Oxidation and oxidised electron carriers

Answer 6

Oxidation is the loss of electron (OIL)

Oxidised electron carriers include NAD+ and FAD

Question 7

Reduction and reduced electron carriers

Answer 7

Reduction is the gain of electrons (RIG)

Reduced electron carriers include NADH and FADH2

Question 8

Enzymes

Answer 8

They act as catalyst in chemical reactions in the body by lowering the activation energy required for a reaction to occur (They increase the rate of product formation.)

Question 9

Match the classification of enzyme with the description.

Kinase, dehydrogenases, oxidases, isomerases

a) Remove hydrogen atoms
b) Catalyze oxidation-reduction reactions involving oxygen
c) Rearrangement of the structure of molecules
d) Add a phosphate group

Answer 9

A = Dehydrogenases
B = Oxidases
C = Isomerases
D = Kinase

Question 10

How does cellular environment factors influence enzyme activity during exercise?

Answer 10

Temperature - exercise increases temp slightly which improves enzyme activity, but after 40degrees enzymes become denatured.

pH - exercise produces H+ ions which reduces pH and inhibits enzyme activity with roles in ATP production.

Question 11

Describe the two pathways that produce ATP and how they differ.

Answer 11

Anaerobic pathway (substrate-level phosphorylation) - doesn’t involve oxygen, ATP-PC system and glycolysis (leading to lactate).

Aerobic pathway - requires oxygen, oxidative phosphorylation, fat and carb oxidation, dependent on cardiorespiratory system to deliver adequate oxygen.

Question 12

What is the net gain of glycolysis if
a) glucose is the substrate
b) glycogen is the subtsrate

Answer 12

a) 2ATP, 2NADH, 2 pyruvate/lactate, 2H+
b) 3ATP, 2NADH, 2 pyruvate/lactate, 2H+

Glycogen in the muscle doesnt require phosphorylation by ATP but is phosphorylated by inorganic phosphate instead.

Question 13

How is NAD+ reformed?

Answer 13

In the absence of oxygen, pyruvate is converted into lactate (PDH) and tis allows the recycling of NAD+ that allows glycolysis to continue.

Question 14

Describe the Citric acid cycle (Krebs cycle/TCA cycle) and list the products.

Answer 14

completes the oxidation (removes electrons) of acetyl-coa (formed from fuels: fats, CHO, protein) to provide electrons for the ETC.

Products of x1 Acetyl-CoA = ATP, 1FADH2, 3NADH, 4H+, 2CO2, CoA

Question 15

Aerobic ATP production

Answer 15

32 ATP (38ATP)

Question 16

Amount of ATP produced
a) per NADH
b) per FADH

Answer 16

a) 2.5ATP per NADH
b) 1.5ATP per FADH

Question 17

Define oxygen deficit and explain how it’s created?

Answer 17

Discrepancy between initial demand for oxygen and the amount of available oxygen (O2 uptake).

This is created as the initial ATP production during exercise is through anaerobic pathways but as we reach steady-state (1-4mins) ATP production is primarily aerobic.

Question 18

Excess post-exercise oxygen consumption (EPOC)

Answer 18

oxygen uptake remains elevated above rest during recovery from exercise.

Question 19

What is the magnitude and duration of EPOC influenced by?

Answer 19

the intensity of exercise

Question 20

Rate limiting enzymes
- Where are they found?
- What is activity regulated by?
- Examples

Answer 20

• Found early in a metabolic pathway
• Activity is regulated by modulators
• Ex: creatine kinase for ATP-PC system / phosphofructokinase for glycolysis

Question 21

3 reasons why endurance trained individuals have a lower 02 deficit than untrained individuals.

Answer 21

1) Greater regional blood flow to active muscle (e.g. more capillaries)
2) Increased cellular adaptation and efficiency
3) Increased mitochondrial volume in muscle fibers results in less lactate production at the beginning of exercise

Question 22

Briefly outline the components of the slow and fast (rapid) components of EPOC

Answer 22

Fast (alactacid) component of EPOC: resynthesis of energy sources such as ATP and phosphocreatine.

Slow (lactacid) component of EPOC: includes elevated HR, BR, body temp, E/NE and conversion of lactic acid to glucose. Muscle repair up to 12hrs after.

Question 23

Explain the basic concept of enzyme action.

Answer 23

The substrate binds to the enzyme active site to form an Enzyme-substrate complex.
The enzyme then catalyses the reaction and the products are released from the unaltered enzyme molecule.

Question 24

What does phosphorylation enable?

Answer 24

the coupling of an exergonic reaction to an endergonic one

Question 25

Explain the conversion of pyruvate to acetyl-coa.

Answer 25

Once in the mitochondria:
» Pyruvate is oxidised by NAD+, producing NADH + H+ (reduced form), and decarboxylated, producing a molecule of CO2 and a 2-carbon fragment of acetate bound to coenzyme A which forms acetyl-coa.

Question 26

Briefly describe the Electron transport chain.

Answer 26

NADH and FADH2 are re-oxidised releasing electrons and hydrogen atoms. Electrons then pass down a series of electron carriers which provides the energy for H+ to be pumped into the intermembrane space.

Question 27

Where is energy that is liberated from chemical bonds through metabolism stored?

Answer 27

• most is stored in ATP in skeletal muscle and to a lesser extent the brain
• some is stored in phosphocreatine

Question 28

For each molecule of glucose metabolized, how many molecules of 02 and C02 are produced?

Answer 28

6 molecules of C02 released from organic compounds.
6 molecules of H20 formed through the electron transport chain - this requires utilisation of 6 molecules of 02.
RER is 1

Question 29

A high level of __ in the muscle fiber would slow glycolysis by inhibiting its rate of limiting enzyme.

Answer 29

ATP

Question 30

Glycolysis

Answer 30

• The breakdown of glucose/glycogen into two molecules of pyruvate or lactate.
• Occurs in the cytosol

Question 31

At rest, what is the O2 consumption of a young adult? Using this answer, what would the oxygen consumption of a 70-kg adult be?

Answer 31

3.5 ml-kg-min
250ml/min OR 0.25L/min

Question 32

Where does most of the carbohydrate used as a substrate during high-intensity exercise come from?

Answer 32

muscle glycogen stores

Question 33

Identify the 3 possible mechanisms to explain the lactate threshold.

Answer 33

1) Accelerated rate of glycolysis due to epinephrine
2) Recruitment of fast-twitch muscle fibers
3) Reduces rate of lactate removal from the blood

Question 34

What gland is epinephrine released from?

Answer 34

adrenal medulla

Question 35

How can the depletion of muscle carb stores during exercise decrease the ability of the muscle to metabolize fat?

Answer 35

reduces the concentration of citric acid cycle intermediates

Question 36

Identify 3 factors by which blood glucose concentration is maintained fairly constant during exercise.

Answer 36

1) Elevated mobilization of FFA from adipose tissue
2) Increased rate of gluconeogenesis
3) Blocked entry of glucose into cells