Lecture 16 - Energy metabolism

Question 1

Hypoxia

Answer 1

Oxygen in limited supply

Question 2

Anoxia

Answer 2

No oxygen in environment

Question 3

Glycolysis

Answer 3

Key anaerobic pathway (especially in vertebrates)

Produces 2 ATP per glucose molecule

Question 4

Lactate

Answer 4

The end product of anaerobic glycolysis

Pyruvate oxidized to lactate via enzyme lactate dehydrogenase.

Question 5

What are the effects of lactic acid?

Answer 5

It dissociates and releases H+ ions which upset acid-base balance and has toxic effects

Question 6

Goldfish vs Human anaerobic metabolism.

Answer 6

Goldfish use ethanol dehydrogenase, which produces ethanol (can be diffused out through gills)
Only suitable in <5 degree water.

Question 7

Other less toxix end products than lactate

Answer 7

Alanine, succinate, octopine

Question 8

Facultative anaerobes

Answer 8

Rely on anaerobic metabolism for extended periods

Intertidal vertebrates

Question 9

Obligate anaerobes

Answer 9

Cannot survive in the presence of significant amounts of oxygen
Protozoans in termite guts and some parasites

Question 10

Oysters and oxygen

Answer 10

Some oysters don’t need oxygen and can survive purely on anaerobic metabolism

Question 11

Reasons to avoid anaerobic metabolism

Answer 11

1. End products are usually toxic

2. Anaerobic metabolism is less efficient (2 ATP vs 38 ATP)

Question 12

To maintain constant body temp

Answer 12

Heat production must be equal to heat loss

Question 13

H = Q = C (Tb-Ta)

Answer 13

Heat production = Heat loss = Thermal conductance(Body temperature - ambient temperature)

Question 14

BMR

Answer 14

Basal Metabolic Rate

Lowest rate of metabolism in an animal

Question 15

What happens when Ta is below Tlc

Answer 15

Heat production at cost of ATP

Question 16

What happens when Ta is above Tlc

Answer 16

Passive Decreasing Insulation until Tb=Ta

Question 17

What happens when Ta is above Tuc

Answer 17

Active evaporative cooling

Question 18

Endotherm vs Ectotherm Aerobic capacity

Answer 18

Endotherms have higher aerobic capacity

Question 19

Why is Metabolism Important?

Answer 19

Converting energetic and material resources from the environment into energy for fitness-enhancing processes of survival (e.g. - growth and reproduction).

Question 20

What are the Basic Requirements of Bomb Calorimetry?

Answer 20

• Sealed reaction vessel
• Sample ignited electrically in presence of pure oxygen
• Temperature rises of water expected

Question 21

What are the 1st and 2nd Laws of Thermodynamics?

Answer 21

1. Energy cannot be created or destroyed, but can be transformed from one form of energy into another.
2. There is inevitable degradation of useful energy into heat.

Question 22

What are the Features of ATP?

Answer 22

• Ubiquitous in living cells
• “Electricity” of cellular metabolism (chemical storage of energy)
• Can be cleaved from ATP -> ADP + P + energy

Question 23

Name and Explain Both Metabolic Pathways:

Answer 23

Catabolic Metabolism:
Breakdown of complex molecules into simpler ones (produces “building block” molecules and ATP)

Anabolic Metabolism:
Synthesis of macromolecules - produces cellular components and uses ATP

Question 24

Explain the Steps of Aerobic Metabolism:

Answer 24

1. NAD+ (nicotine-adenine dinucleotide) reduced to NADH
2. Glucose oxidised to pyruvate
3. Complete oxidation to CO2 and H2O requires oxygen

Question 24

Explain the Steps of Aerobic Metabolism:

Answer 24

1. NAD+ (nicotine-adenine dinucleotide) reduced to NADH 2. Glucose oxidised to pyruvate 3. Complete oxidation to CO2 and H2O requires oxygen

Question 25

Explain the Steps of Anaerobic Metabolism:

Answer 25

1. NAD+ reduced to NADH and glucose becomes 2 pyruvate (2ADP -> 2ATP) 2. 2 pyruvate becomes 2 lactate via NADH oxidation into NAD+. 3. Overall output of 2 ATP per glucose molecule. Note: Lactate can dissociate (if accumulated) and release H+ ions, upsetting the acid-base balance thus creating toxic effects.

Question 26

What are the Two Types of Anaerobes?

Answer 26

Facultative Anaerobes: Rely on anaerobic metabolism for extended periods Obligate Anaerobes: Cannot survive in the presence of significant amounts of oxygen (e.g. - protozoans)

Question 27

What is Oxygen Debt?

Answer 27

The resynthesis of depleted ATP and phosphocreatine, replenishing myoglobin.

Question 28

The Effect of Temperature on Metabolic Rate:

Answer 28

To maintain a constant body temperature, heat production (H) must equal heat loss (Q) -> H = Q = C(Tb - Ta) - C = thermal conductance - Tb = body temperature - Ta = ambient temperature

Question 29

What is Assimilation Efficiency?

Answer 29

Apparent assimilated energy (A) / Gross energy consumption (C) A = C - Fecal energy

Question 30

Which Food Has the Highest Assimilation Efficiency?

Answer 30

Highest to Lowest: | Nectar -> Vertebrate Tissue -> Grains and Seeds -> Herbivory

Question 31

What are the Types of Urinary Energy Loss?

Answer 31

Endogenous: Deamination and transamination of amino acids resulting from basal protein turnover. Exogenous: Deamination of amino acids ingested and absorbed in the food (depends on the feeding rate, food protein content and amino acid composition of the proteins) Waste Products -> Ammonia (Fish), Urea (Mammals), Uric Acid (Birds and Reptiles)

Question 32

What is Specific Dynamic Action (SDA)?

Answer 32

The heat increment of feeding: - Depends on the size, composition and temperature of the meal. - Depends on the animal's body size, composition, sex and age - Depends on the temperature, gas concentration and salinity of the environment.

Question 33

What is the Mechanistic Basis of Specific Dynamic Action?

Answer 33

Pre-Absorptive Contributions: - Occur prior to the passage of ingested nutrients into circulation - Eating and swallowing (a few % for most species; more for herbivores) - Gastric breakdown (cost depends on state of meal when entering stomach) - Intestinal peristalsis and absorption. Post-Absorptive Contributions: - Occur once nutrients are circulating - Substrate catabolism (major contributor) - Biosynthesis (e.g. - protein synthesis, glycogen from glucose, etc.)

Question 34

How do Animals Generate ATP When Oxygen is Limited or Unavailable? What are the Advantages and Disadvantages of This Pathway Compared to Pathways that Require Oxygen?

Answer 34

Animals generate ATP through anaerobic respiration when oxygen is limited. Advantages: - Produces ATP in absence of oxygen - Rapid production of energy Disadvantages: - Lactic acid accumulation can be toxic to host organism - Very inefficient process of producing ATP (2 ATP as opposed to aerobic respiration being 38 ATP).