Chapter 2: Defining and Measuring Energy

Question 1

Bioenergetics

Answer 1

The process of converting food into biologically useful forms of energy

Question 2

Energy

Answer 2

Ability to perform work

Question 3

What forms does work exist in?

Answer 3

Chemical, electrical, mechanical, and transportation

Question 4

The Law of Conservation of Energy

Answer 4

First law of thermodynamics.
Within a closed system, energy is neither created nor destroyed.
It can be transformed from one form of energy to another.

Question 5

How does the first law of thermodynamics relate to humans?

Answer 5

Humans don’t create or lose energy, we transfer energy from one form to another.
Consume food and then transform it into a variety of chemical forms.

Question 6

How is energy used in the human body?

Answer 6

Energy exists in a state of potential energy when being stored for future use.
It is converted into kinetic energy when it is released to perform work.
High-energy phosphate compounds store and release energy.

Question 7

High-energy phosphate compound

Answer 7

Adenosine triphosphate (ATP)

Question 8

ATP

Answer 8

Used in chemical reactions in the body.
Stores energy in its phosphate bonds.
Protein molecule (adenine) combines with a sugar molecule (ribose) to form adenosine.
Source of energy in all cells

Question 9

How is energy released in the human body?

Answer 9

Released in one rapid step.
Occurs when phosphate group is removed from ATP.
Catalyzed by the enzyme ATPase (starts reaction and speeds it up).

Question 10

What influences the amount of energy we need to perform an activity?

Answer 10

As intensity of physical activity increases, so do our energy needs.
May need large total amount or a high rate.

Question 11

Calorie (kilocalorie/kilojoule)

Answer 11

1000 little calories (c)
Used by food labels
Kilojoules divided by 4.2 = kilocalories

Question 12

calorie (c)

Answer 12

The heat required to raise the temperature of 1 gram of water by 1 degree Celsius

Question 13

What are the energy values of each macronutrient?

Answer 13

CHO = 4.2 kcal/g (food labels rounded to 4 kcal/g)
Protein = 5.7 kcal/g but nitrogen cannot be oxidized by humans therefore 4.2 kcal/g (food labels rounded to 4 kcal/g)
Fats = 9.4 kcal/g (food labels rounded to 9 kcal/g)
Alcohol = 7.0 kcal/g (slightly less if liver cells are damaged)

Question 14

What do we have to be cautious about when discussing caloric values?

Answer 14

All caloric values for humans are only estimates.
We cannot directly measure the true potential energy from food.
Strict calorie counting is not recommended because values are not accurate on food labels.

Question 15

Energy balance

Answer 15

Energy in = energy out

Question 16

How do we analyze energy intake?

Answer 16

Energy intake is estimated by analyzing daily food and beverage intake through self-report using a food diary.

Question 17

What are the issues with food diaries?

Answer 17

Lots of error on types and amounts of foods consumed.
Difficult to estimate beverage intake.
Food intake typically underestimated by 10-20%.
Social desirability bias

Question 18

Total energy expenditure (TEE)

Answer 18

Total amount of energy needed in a day
Involves resting metabolism, thermic effect of food, and physical activity.

Question 19

What are the two major components of TEE?

Answer 19

Basal metabolic rate (BMR) and resting metabolic rate (RMR)

Question 20

Basal metabolic rate (BMR)

Answer 20

The energy needed to keep the body alive at complete rest.
Minimal amount of energy needed to sustain life.
Measured in the morning after a fast in a lab setting.

Question 21

Resting metabolic rate (RMR)

Answer 21

Resting metabolism.
Not under the same control as BMR.
About 10% higher than BMR.
About 70% of TEE is attributed to RMR.

Question 22

What are the factors that affect RMR?

Answer 22

Gender, genetics, age, height, thyroid hormone, starvation, amount of fat-free mass, exercise, environmental temperature/altitude, and caffeine.

Question 23

Is estimating RMR accurate?

Answer 23

All equations used have a large error.
Can underestimate by up to 18% or overestimate by up to 15%.
Those who have more muscle will have more error when using these equations.

Question 24

Thermic effect of food

Answer 24

Energy required for the digestion and absorption of food.
Involves a small part of overall energy expenditure, about 10%.
Proteins increase TEF more than CHO.

Question 25

Physical Activity

Answer 25

The most significant way to increase energy expenditure.
Many ways to measure so must be cautious.