1. Why We Need to Eat
Section 9.1

2. Why We Need to Eat
Learning Goal: To explore why animals eat and how much energy we need to consume.
Success Criteria:
I know I am succeeding when I can…
explain that nutrients are used by the body for growth, repair and energy
explain the factors that affect metabolic rates
calculate basal metabolic rate (BMR)

3. Why We Need to Eat
all animals must eat to obtain materials for growth and repair and to obtain energy for all life processes

4. Nutrients
nutrients: are the chemicals that an organism needs in order to grow, build, and repair tissues, and to produce energy
the major nutrients are carbohydrates, proteins, lipids (fats), water, minerals,and vitamins

5. Metabolism
Metabolism: set of chemical reactions that occur in living organisms that are necessary to maintain life

6. Metabolism
Catabolism: the metabolic reactions that break down larger molecules into smaller subunits
Anabolism: the metabolic reactions that use energy to produce larger molecules from smaller subunits

7. Metabolism
metabolic rate: the rate at which the body converts stored energy into working energy

8. Factors that Affect Metabolic Rate
body size: The larger the body, the more energy is required to stay alive.

9. Factors that Affect Metabolic Rate Cont’d…
physical activity: Muscle burns more energy than fat, so physical activity requires more energy.

10. Factors that Affect Metabolic Rate Cont’d…
sex: Males are typically larger in size and have a greater proportion of muscle mass than females of the same size, age, and fitness level.

11. Factors that Affect Metabolic Rate Cont’d…
age: Metabolic rate decreases with age (in part due to decreased physical activity and the loss of muscle mass).

12. Factors that Affect Metabolic Rate Cont’d…
hereditary factors: Some individuals have a naturally high metabolic rate (i.e. the chemical energy obtained from food is very quickly converted into other forms of energy).

13. Measuring Energy
energy is measured using joules (J) or kilojoules (kJ) to refer to the energy requirements of
1 Calorie (C) = 4180 J

14. Measuring Energy Cont’d…
basal metabolic rate (BMR): the rate at which energy is used by an organism when it is at rest (i.e. minimum amount of energy required to keep you alive)
estimated using a calculation that takes into account four variables: height, weight, age, and sex
your energy requirements also depend on your activity level

15. Measuring Energy Cont’d…
The Harris–Benedict formulas for estimating BMR:
female
BMR = [ (9.5 x mass in kg) + (1.9 x height in cm) -(4.7 x age in years)]
male
BMR = [ (13.7 x mass in kg) + (5.0 x height in cm) – (6.8 x age in years)]

16. Measuring Energy Cont’d…
The Harris–Benedict formula uses the following activity factors in conjunction with the BMR to estimate the average individual daily energy requirement.
little or no exercise BMR x 1.2
light exercise or sports 1–3 days/week BMR x 1.375
moderate exercise or sports 3–5 days/week BMR x 1.55
vigorous exercise or sports 6–7 days/week BMR x 1.725
very hard exercise daily or sports & physical BMR x 1.9 job or x training daily

17. Measuring Energy Cont’d…
Sample Question: Tom is a 16-year-old student who is 175 cm tall with a mass of 75 kg. Tom is a fairly active student who plays sports most weekdays. Estimate his average daily energy requirement.
female
BMR = [ (9.5 x mass in kg) + (1.9 x height in cm) -(4.7 x age in years)]
male
BMR = [ (13.7 x mass in kg) + (5.0 x height in cm) – (6.8 x age in years)]

18. Measuring Energy Cont’d…
your energy requirement varies with the type and amount of physical activity that you do

19. Why We Need to Eat
Learning Goal: To explore why animals eat and how much energy we need to consume.
Success Criteria:
I know I am succeeding when I can…
explain that nutrients are used by the body for growth, repair and energy
explain the factors that affect metabolic rates
calculate basal metabolic rate (BMR)

20. Homework
Answer 9.1 questions #2-5