Lecture 18 - Metabolism and Metabolic Adaptations

Question 1

What is Anabolism? What are some examples and usages

Answer 1

Sum of all synthesis reactions
Synthesis reactions
Energy Storage
Tissue building/maintenance
Releases Energy

Question 2

What is Catabolism? What are some examples and usages?

Answer 2

Sum of all breakdown reactions
breakdown reactions
Energy provision
Tissue breakdown
Requires Energy

Question 3

What is Human Calorimetry?


Answer 3

Measurement of human heat production

Question 4

What is Exercise Calorimetry?


Answer 4

Measurement of human heat production, equivalent of energy used during exercise

Question 5

Compare and Contrast Direct vs Indirect Calorimetry
Direct:

Answer 5

Direct:
Measurement of heat production in a metabolic chamber
Physical work converted to heat energy
Very rare

Indirect:
Measurement of oxygen consumption (VO2)
Relationship between amount of heat produced (in chamber) and amount of oxygen used (measured)

Question 6

What is closed circuit indirect calorimetry


Answer 6

Involves recirculating the subject’s exhaled air back to them after removing carbon dioxide and replenishing oxygen
Chamber starts at 100% O2
CO2 is absorbed (typically by lime soda) and exhaled air is replenished
Reduction in gas volume reflects O2 used
Changes in gas concentrations within the circuit are measured to determine oxygen consumption and carbon dioxide production

Question 7

What is open circuit calormetry

Answer 7

Involves analysing the differences in gas concentrations between inhaled and exhaled air
Subjects breathe in a controlled environment, and air entering and leaving the system is analysed
Oxygen consumption and carbon dioxide production are calculated based on these differences

Question 8

Why do we recirculate exhaled air during closed circuit indirect calorimetry?


Answer 8

By recirculating the subject’s exhaled air and adjusting the concentrations of oxygen and carbon dioxide within the closed circuit, researchers can maintain precise control over environmental conditions such as temperature, humidity, and gas composition.

Question 9

What is the numerical relation between heat production and volume of oxygen?


Answer 9

1 L of O2 ~ 21 kJ (5 kcal)

Question 10

What is the conversion between a calorie and a kilojoule?


Answer 10

1 kcal = 4.18 kJ

Question 11

What is calorimetry, what does it measure and why do we use it when referring to metabolism?

Answer 11

Calorimetry can be used to study metabolic processes indirectly by measuring the heat released or absorbed during those processes.
Metabolism involves a series of biochemical reactions that occur within an organism to sustain life, including both catabolic processes (breaking down of molecules to release energy) and anabolic processes (building up of molecules using energy).

Question 12

What is RER?

Answer 12

Respiratory Exchange Ratio.
Represents the relationship between the amount of carbon dioxide (CO2) produced and the amount of oxygen (O2) consumed during metabolism
RER = VCO2 / VO2

Question 13

What RER values correspond to the fuel substrate being utilized for energy production?

Answer 13

RER = 0.70 using ~ 100% fats
RER = 0.85 using mixture of fats & CHO
RER = 1.00 using ~ 100% CHO

Question 14

What does an RER of 1 Indicate

Answer 14

Indicates that the body is utilizing an equal mix of carbohydrates and fats as energy sources

Question 15

What is the main substrate(s) used at rest [in aerobic conditions] and what are the main things that may influence substrate use?

Answer 15

Substrates:
Fats
Carbohydrates (CHO)

Question 16

What are the main things that may influence substrate use at rest?

Answer 16

Content of last food intake:
More carbohydrates (CHO) in the meal leads to the utilization of more CHO as a substrate.

Time since last food intake:
Longer duration since the last meal results in increased utilization of fat as a substrate.
Fat as the main substrate during overnight sleep:
During overnight sleep, when there’s typically a longer duration since the last meal, fat becomes the primary substrate for energy production.
This reliance on fat metabolism helps sustain energy levels during prolonged fasting periods.

Question 17

What is the main substrate(s) used during exercise and what is the MAIN determinant for type of substrate? (Bonus: List 2 other determinants)

Answer 17

Intensity of exercise is a major determinant.
Low-intensity exercise primarily utilizes fats.
Higher-intensity exercise predominantly uses carbohydrates (CHO).
Duration
2) Fitness Level

Question 18

How does duration influence substrate use during exercise

Answer 18

Duration:
Longer duration exercise tends to use more fat as a substrate.
Longer duration exercise is often of lower intensity.
Initially high intensity exercise tends to decrease in intensity as glycogen stores are depleted, leading to increased fat utilization.

Question 19

How does fitness level influence substrate use during exercise

Answer 19

Fitness level:
Fitness level influences the intensity of sustainable long-duration exercise.
Higher fitness levels may allow for sustained higher intensity exercise, possibly favouring CHO utilization.

Question 20

Why can fitter people train for longer and more intensely and still favor fat metabolism?

Answer 20

Increased Aerobic Capacity: Raising the VO2max threshold
Enhanced Fat Utilization: With improved fitness, the body becomes better at utilizing fat as a fuel source
Improved Metabolic Efficiency: Adaptations including increased mitochondrial density, improved mitochondrial function, and enhanced enzyme activity involved in energy metabolism

Question 21

What principles of training affect the metabolic adaptation in question?

Answer 21

Metabolic adaptations are specific to:
– Frequency
– Intensity
– Time (Duration of session)
– Type

Question 22

Describe the metabolic adaptations of substrate levels on endurance (E), sprint/interval (S), resistance (R) and circuit resistance (CR) training


Answer 22

All - Increase ATP & PC stores in muscle

Question 23

Describe the changes in muscle fibre mitochondria on endurance (E), sprint/interval (S), resistance (R) and circuit resistance (CR) training

Answer 23

E, S, CR - Increase number and size
R - Decreased number and size

Question 24

Describe the changes in muscle enzyme activity on endurance (E), sprint/interval (S), resistance (R) and circuit resistance (CR) training


Answer 24

All - Increase PFK, variable glycolytic enzymes

Question 25

Describe the changes in use of O2 on endurance (E), sprint/interval (S), resistance (R) and circuit resistance (CR) training

Answer 25

E, S, CR - Increased myoglobin, decreased O2 deficit
R - No significant change in VO2