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BIO2242 > Lecture 16 - Energy metabolism > Flashcards

Lecture 16 - Energy metabolism Flashcards

1
Q

Hypoxia

A

Oxygen in limited supply

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2
Q

Anoxia

A

No oxygen in environment

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3
Q

Glycolysis

A

Key anaerobic pathway (especially in vertebrates)

Produces 2 ATP per glucose molecule

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4
Q

Lactate

A

The end product of anaerobic glycolysis

Pyruvate oxidized to lactate via enzyme lactate dehydrogenase.

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5
Q

What are the effects of lactic acid?

A

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

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6
Q

Goldfish vs Human anaerobic metabolism.

A

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

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7
Q

Other less toxix end products than lactate

A

Alanine, succinate, octopine

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8
Q

Facultative anaerobes

A

Rely on anaerobic metabolism for extended periods

Intertidal vertebrates

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9
Q

Obligate anaerobes

A

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

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10
Q

Oysters and oxygen

A

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

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11
Q

Reasons to avoid anaerobic metabolism

A
  1. End products are usually toxic

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

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12
Q

To maintain constant body temp

A

Heat production must be equal to heat loss

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13
Q

H = Q = C (Tb-Ta)

A

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

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14
Q

BMR

A

Basal Metabolic Rate

Lowest rate of metabolism in an animal

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15
Q

What happens when Ta is below Tlc

A

Heat production at cost of ATP

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16
Q

What happens when Ta is above Tlc

A

Passive Decreasing Insulation until Tb=Ta

17
Q

What happens when Ta is above Tuc

A

Active evaporative cooling

18
Q

Endotherm vs Ectotherm Aerobic capacity

A

Endotherms have higher aerobic capacity

19
Q

Why is Metabolism Important?

A

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

20
Q

What are the Basic Requirements of Bomb Calorimetry?

A
  • Sealed reaction vessel
  • Sample ignited electrically in presence of pure oxygen
  • Temperature rises of water expected
21
Q

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

A
  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.
22
Q

What are the Features of ATP?

A
  • Ubiquitous in living cells
  • “Electricity” of cellular metabolism (chemical storage of energy)
  • Can be cleaved from ATP -> ADP + P + energy
23
Q

Name and Explain Both Metabolic Pathways:

A

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

24
Q

Explain the Steps of Aerobic Metabolism:

A
  1. NAD+ (nicotine-adenine dinucleotide) reduced to NADH
  2. Glucose oxidised to pyruvate
  3. Complete oxidation to CO2 and H2O requires oxygen
24
Q

Explain the Steps of Aerobic Metabolism:

A
  1. NAD+ (nicotine-adenine dinucleotide) reduced to NADH
  2. Glucose oxidised to pyruvate
  3. Complete oxidation to CO2 and H2O requires oxygen
25
Q

Explain the Steps of Anaerobic Metabolism:

A
  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.

26
Q

What are the Two Types of Anaerobes?

A

Facultative Anaerobes:
Rely on anaerobic metabolism for extended periods

Obligate Anaerobes:
Cannot survive in the presence of significant amounts of oxygen (e.g. - protozoans)

27
Q

What is Oxygen Debt?

A

The resynthesis of depleted ATP and phosphocreatine, replenishing myoglobin.

28
Q

The Effect of Temperature on Metabolic Rate:

A

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
29
Q

What is Assimilation Efficiency?

A

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

30
Q

Which Food Has the Highest Assimilation Efficiency?

A

Highest to Lowest:

Nectar -> Vertebrate Tissue -> Grains and Seeds -> Herbivory

31
Q

What are the Types of Urinary Energy Loss?

A

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)

32
Q

What is Specific Dynamic Action (SDA)?

A

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.
33
Q

What is the Mechanistic Basis of Specific Dynamic Action?

A

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.)
34
Q

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?

A

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).

BIO2242 (33 decks)

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