Lecture 4 & 5 - Energy and Basal Metabolism l & ll

Through what type of metabolic reactions is energy from nutrients captured as ATP?

Redox reactions (reduction-oxidation).

According to the principles of energy metabolism, all metabolic reactions ultimately release _____.

Heat

How does the Second Law of Thermodynamics apply to energy transfer in animals?

Entropy (disorder) increases, meaning the transfer is not $100\%$ efficient.

Term: Metabolic Rate

Definition: The amount of energy an animal uses over a specific period of time, often expressed in $kcal$ per unit time.

What two gases are measured in indirect calorimetry to calculate metabolic rate?

Oxygen ($O_2$) consumed and carbon dioxide ($CO_2$) produced.

Which organ or tissue group contributes the highest percentage ($27\%$) to basal metabolic rate per $1\text{ kg}$ of tissue?

Liver and spleen.

Per $1\text{ kg}$ of specific tissue, what is the BMR contribution percentage of the brain?

$19\%$.

Per $1\text{ kg}$ of specific tissue, what is the BMR contribution percentage of skeletal muscle?

$18\%$.

Per $1\text{ kg}$ of specific tissue, what is the BMR contribution percentage of the kidneys?

$10\%$.

Per $1\text{ kg}$ of specific tissue, what is the BMR contribution percentage of the heart?

$7\%$.

In the breakdown of daily energy expenditure, what approximate percentage is attributed to resting metabolism?

$60\%$.

In the breakdown of daily energy expenditure, what approximate percentage is attributed to physical activity?

$32\%$.

In the breakdown of daily energy expenditure, what approximate percentage is attributed to the thermic effect of food?

$8\%$.

What metabolic process accounts for the energy required for digestion, absorption, and nutrient processing?

Thermic effect.

Which expression of BMR is most useful for determining total daily feed rations for a specific animal?

Whole-Body BMR (total $kcal/d$).

Formula: Mass-Specific BMR

$kcal / kg \text{ BW} / d$

Which expression method is considered most accurate for comparing the metabolic rates of different species fairly?

Metabolic Body Weight ($kcal / kg \text{ BW}^{0.75} / d$).

How does the whole-animal BMR of an elephant compare to that of a mouse?

The elephant has a higher whole-animal BMR.

How does the mass-specific BMR (energy per unit of body weight) of a mouse compare to that of an elephant?

The mouse has a much higher mass-specific BMR.

Why do smaller animals generally have a higher BMR per gram of body mass?

They have a larger surface area relative to volume, causing them to lose heat faster.

In terms of heat dynamics, heat is generated in the _____ of the animal and lost through the _____.

Volume (body tissues); Surface area (skin).

The average elephant weighs $220,000$ times more than a mouse but only requires about $10,000$ times more energy because larger animals use energy more _____.

Efficiently

According to Kleiber's "Surface Law," metabolic body size is calculated as the body weight to the power of _____.

$3/4$ (or $0.75$).

What term is used to describe the metabolic state where an animal breaks down its own tissue reserves because no external energy is provided?

Fasting Catabolism.

To assess Basal Metabolic Rate, the animal must be in a post-absorptive state, meaning it is currently _____.

Fasting (not actively digesting food).

What are the four primary conditions required to accurately measure an animal's Basal Metabolic Rate?

Awake, complete physical/mental rest, post-absorptive (fasting) state, and a thermoneutral environment.

Concept: Torpor

Definition: An energy-saving strategy where an animal dramatically lowers its metabolism.

What is the specific term for torpor that occurs during the summer?

Estivation

What is the specific term for torpor that occurs during the winter?

Hibernation

Metabolic rate is typically calculated by measuring $O_2$ consumed and $CO_2$ produced, a method known as _____.

Indirect calorimetry

How does the Surface Area to Volume ratio ($SA:V$) of a small cube ($1 \times 1 \times 1$) compare to a large cube ($3 \times 3 \times 3$)?

The small cube has a higher ratio ($6:1$) compared to the large cube ($2:1$).