Chp 6 energy metabolism
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Chp 6 Energy Metabolism. Energy metabolism: - Catabolism: processes breaking down organic molecules to release energy - Anabolism: processes using energy to construct molecules Why animals need energy?. Energy is needed for work

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Chp 6 Energy Metabolism

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Chp 6 energy metabolism

Chp 6Energy Metabolism

  • Energy metabolism:

    - Catabolism: processes breaking down organic molecules to release energy

    - Anabolism: processes using energy to construct molecules

    Why animals need energy?


Fundamentals of animal energetics

Energy is needed for work

Animals can use chemical, electrical and mechanical energies (high grade energy) for work but not thermal energy (low grade energy).

Efficiency of energy transformation = output/input of high-grade

Efficiency: Always less than 1.

Ex: glucose  70%ATP + 30% heat

Fundamentals of Animal Energetics


Energy use

Energy use

  • Energy (food) is used for:

    • Maintenance

    • Growth (biosynthesis)

    • Work

  • However, each conversion is inefficient

    •  heat formation

    • Usable energy: from feces(?!), body matter


Metabolic rate meaning and measurement

Metabolic rate: Meaning and Measurement

  • Energy for work + heat comes from energy consumed

  • Rate of energy consumption = metabolic rate

  • Energy is measured in calories or joules

  • Calorie: amount of heat needed to raise the temperature of 1 gm of water by 1oC.

  • Metabolic rate = consumption of energy: calories/unit of time or watts

  • Significance of metabolic rates:

    • 1 - determines the amount of food an animal will need

    • 2 - the total rate of heat production is proportional to the total activity of all its physiological mechanisms

    • 3 - an animal’s metabolic rate represents the use of food resources of this animal’s ecosystem


Metabolic rate measurement

Direct measurement

Indirect measurement

By respirometry

(box 6.4)

By measuring the chemical-energy content of the organic matter that enters and leaves the animal’s body

Metabolic rate measurement

___


Metabolic rate

Metabolic rate

  • Read p 149

  • Under aerobic metabolism, carbohydrates, proteins and lipids are burnt and produce CO2

  • The rate of O2 consumption and CO2 formation vary with the 3 gps of nutrients (table 6.1)

  • Respiratory quotient (lungs) R = moles CO2 produced /moles O2 consumed

  • For convenience, O2 consumption is used to estimate the metabolic rate

    Allows to estimate the kind of food that has been burned

    Because this is cumbersome to calculate, the number 20.2J/ml O2 is used to calculate the MR from O2 consumption


Factors that affect metabolic rates

2 main factors:

physical activity

external temperature

Other factors:

Age

Food ingestion

Gender

Time of the day

Body size

Reproductive condition

Hormonal state

Psychological stress

For aquatic animal, the salinity of ambient water

The food effect: specific dynamic action (SDA) = calorigenic effect of ingested food, especially proteins

The SDA is about 25%-30% of the energy value of the meal.

Factors that affect metabolic rates


Chp 6 energy metabolism

  • Basal metabolic rate = BMR = metabolism rate at rest, at thermoneutral zone, in homeotherms

  • Thermoneutral zone = temperature at which the BMR is minimal

  • Standard Metabolic Rate = MR of a poikilotherm while it is 1) fasting, 2) resting


Metabolic rate size and activity

The maximal MR (Mmax) during strong aerobic exercise tends to be 10 x the BMR

The number of mitochondria per cells is higher in smaller species

Smaller species have also a more extensive respiratory tubes and circulatory vessels

Metabolic rate, size and activity


Heart size and heart

Heart size is proportional to body size

However, smaller bodies have a higher MR

How to provide the body with enough O2 to sustain a more intense MR?

Heart size and Heart ?


Relationship between size and metabolic rate

The total BMR increases with size, however, it does not proportionally increase with weight

Weight-specific metabolic rate: relationship constant through homeo and poikilotherms (allometric relationship)

M = aWb

b = 0.65-0.75

a varies with groups

Relationship between size and metabolic rate


Heart size and heart1

Heart size is proportional to body size

However, smaller bodies have a higher MR

How to provide the body with enough O2 to sustain a more intense MR?

Heart size and Heart ?


Heart size and heart2

Heart size is proportional to body size

However, smaller bodies have a higher MR

How to provide the body with enough O2 to sustain a more intense MR?

By having an increased Heart Rate and an increased Respiratory Rate

Ecological consequences:

Smaller species need more food per unit of body weight

Smaller species draw more resources from the ecosystem

Smaller species accumulate more toxins than larger one.

Heart size and Heart ?


Energetics of food and growth

Proteins and carbohydrates = 4 kCal/gm, lipids – 9 kCal/gm

Energy absorption efficiency = absorbed/ingested energy

Growth growth efficiency= chemical-bondd energy of tissue added by growth (net)/ingested energy

Net growth efficiency = chemical-bond energy of tissue added by growth (net)/absorbed energy

Growth efficiency declines with age

Energetics of food and growth


Practical consequences

Farming and aquaculture: animals are slaughtered when they have reached their peak growth.

Afterward, there is a decrease in the investment

All life processes cost energy

Mental effort costs some, however, brain maintenance is overall costly

Practical consequences


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