Exam 1 - Animal Energetics

What is bioenergetics?

The study of how energy flows through living organisms

What are the 3 types of physiological work?

Biosynthesis, Generation of external work, and maintenance

What is metabolism?

Entire set of chemical processes that convert food into energy

What is metabolic rate?

The speed at which an animal consumes energy

Metabolic rates are significant for 3 reasons:

1. Provides quantitate measurement of total activity of all physiological work ((can also provide insight into cost of changes in environmental conditions)

2. Determines now much food is needed for survival (supply> demand )

3. Measures the drain the animal places on its ecosystem

Animals rely on aerobic respiration to fuel physiological work. What is that?

Break down of organic molecules using O2 to produce energy ( atp+ Heat)

What are 3 important points to remember?

1. Cells must make their own ATP.

2. ATP is not stored by cells- its made to order

3. The rate a cell can conduct physiological work is dependent upon the rate that cell can make ATP

What are ways to determine metabolic rate?

1. Direct Calorimetry: HEAT
2. Indirect calorimetry: O2 and/or CO2

You catch a frog from a pond on a cool summer day. The frog feels cool to the touch. Can you use direct calorimetry to measure this frog’s metabolic
rate? Why or why not?

Yes- All forms of physiological work produce heat but production is low (comparatively). Bodies are poorly insulated so heat is easily exchanged
with environment.

Why is measuring an animal’s rate of oxygen consumption (indirect calorimetry) a good proxy for its overall metabolic rate?

Change in rate of O2 consumption (Δ O2 /time) represents:


• Rate of oxygen use by mitochondria in body tissues


• Rate of cell respiration in body tissues


• Indirect estimate of rate of energy production & use at time of measurement

What is direct calorimetry?

the direct measurement of heat production in
the body. Upon oxidation, the energy within our organic fuel
molecules is transferred into:
• ~40% ATP (used for physiological work)
• ~60% metabolic heat (released). Based on 1st law of thermodynamics

What is indirect calorimetry?

estimates energy use by measuring rates
of gas exchange. Rates of O2 use most common measurement (CO2 production can also be tracked).

What are the pros of direct calorimetry?

Highly accurate for resting state

Measures both aerobic and anaerobic metabolism

What are the cons of direct calorimetry?

Expensive, large, long measurement period, not accurate during exercise, and only terrestrial animals

What are the pros of indirect calorimetry?

Measurements under all conditions, short measurement period, less expensive, requires less space, terrestrial and aquatic organisms

What are the cons of indirect calorimetry?

Can only measure aerobic metabolism and equipment can be cumbersome to subject

What is respirometry?

Technique used to measure gas exchange (O2 consumption, CO2 release) to determine the metabolic rate of living things

What is closed / static respirometry?

animal housed in fully sealed container filled with volume of air or water

What is open / flow-through respirometry?

Animal housed in an open container and draws O2 from a stream of air/water

What is intermittent flow through respirometry?

• Animal housed in open container


• Flow ”closed” off during measurement phase


• Flow resumed during non-measurement 
phases

What are some factors that affect metabolic rate?

Activity level & environmental temperature, food, age, gender, time of day, etc

When measuring & comparing metabolic rates its important to:

1. Standardize for factors that affect metabolic rate

2. Obtain accurate measurements of baseline metabolic rate
   • Animals must maintain minimal metabolic rate for basic functions:
   • Cell maintenance, Cell Respiration, Circulation, Ion balance

What are the differences and similarites between BMR and SMR?

BMR:

• endotherm, non growing, comfortable temperature range, 1300-1800 kcal/day (expensive!!)

SMR:

• Ectotherm, specific to a temperature, 60 kcal/day

Both

• at rest, fasting, non-stressed

What is routine metabolic rate (RMR)?

energy used to maintain basic bodily functions during normal, routine activity

What is the effect of activity on Mr?

When considering aerobically fueled activity humans and most animals - metabolic rate will increase with activity

Why does metabolic rate increase with
activity?

ATP production is needed due to muscles needing more

How do the relationships between activity level and metabolic rate differ between terrestrial, aquatic, and flying vertebrates?

Aquatic vertebrates show the smallest increase in metabolic rate with activity (J-shaped), terrestrial vertebrates show an intermediate increase (linear), and flying vertebrates show the steepest increase due to the high energetic cost of flight (U-shaped).

What is main factor driving the differences in the trendlines between the animal groups?

The differences in trendlines are driven by variation in the energetic cost of locomotion imposed by the medium in which animals move (air vs water vs wind)

When do metabolic transitions occur?

At the start and end of vertebrate exercise

What is EPOC?

Excess postexercise oxygen consumption - It’s the extra oxygen your body uses after you finish exercising to recover and return to its normal (resting) state.

What is aerobic metabolic scope (or maximal aerobic capacity)?

It is the peak rate at which an animal can synthesize ATP through aerobic catabolism (cellular respiration).

What does aerobic metabolic scope estimate about an animal?

It estimates how intensely an animal can exercise during the “pay-as-you-go” phase, when ATP demand is met aerobically

How do physiologists commonly use aerobic metabolic scope?

Physiologists often use it as an estimate of an animal’s overall performance capacity.

At what biological levels does aerobic metabolic scope differ?

It differs among phyletic groups (taxa), among species within a phyletic group, and among individuals within a species.

Rough Rule of Thumb:

For vertebrates MMR (or VO2max ) is generally ~4-10x more than resting O2
consumption

How is AMS calculated?

Calculated from the difference between
MMR and baseline MMR

Energy available for processes above &
beyond basic costs of sustaining life:

Locomotion, digestion, growth and reproduction

Why is aerobic scope an important measurement?

it reflects an animal’s capacity to perform energy-demanding activities using aerobic metabolism

What is Tₒpt (Optimal Temperature) on a temperature–performance curve?

The temperature at which an organism has the highest fitness, with the most energy available for non-essential processes (e.g., growth, reproduction, activity).

What is Tcrit (Critical Temperature)?

A high or low temperature where the animal is alive but passive. Survival is time-limited, and energy is only sufficient for essential maintenance processes.

What is Tpejus?

A weakened state where the amount of energy available for activities above basal metabolism is limited, and additional stressors can be fatal.

How does maximal aerobic capacity respond to endurance training?

Maximal aerobic capacity (VO₂max) increases with endurance training, showing that it is a plastic trait that responds to training and selection.

What physiological changes occur with endurance training?

Endurance training increases VO₂max, muscle citrate synthase activity, and muscle cytochrome c oxidase activity, reflecting enhanced mitochondrial and aerobic capacity.

By how much does endurance training typically increase VO₂max in sedentary individuals?

Endurance training typically increases a sedentary person’s VO₂max by ~10–30%.

What does the training protocol in the endurance study involve?

Participants completed 60 minutes/day of vigorous cycling, 5 days per week, for 7 weeks; most before–after changes were statistically significant except testosterone.

1. Compare Basal (Standard) MR between vertebrate groups (of similar sizes). What trend(s) do you observe? Explain

Resting rates of O2 consumption of fish, amphibians, reptiles are typically lower (1/10th to 1/4) than basal rates for mammals

Compare maximal MR of non-mammalian verts to resting MR of mammals. What trend do you observe? Discuss implications

Peak rates of O2 consumption of fish, amphibians, reptiles are at same order of
magnitude as basal rates for mammals

What is specific dynamic action?

increase in metabolic rate after feeding that occurs due to the energy required for digestion, absorption, transport, and assimilation of nutrients.

Protein rich meals result in higher
SDAs than carbohydrate rich or
fatty meals

Cost of digesting a protein rich
meal can be 25-30% of the total
energy value of the meal