Intro to Metabolism & Biochemical Pathways

Question 1

When does weight gain/loss occur? What factors influence it?

Answer 1

Weight gain = sustained intake > expenditure

Weight loss = sustained intake less than expenditure

Question 2

3 components of Energy Balance (TEE)

Answer 2

1. Resting Metabolic Rate (RMR) = 75% in sedentary people, energy cost of keeping Na+ and K+ where they belong etc
2. Thermic Effect of Food (TEF) = 8% of TEE, the energy cost of digesting and distributing nutrients.
3. Energy Expended in Physical Activity (EEPA) = most variable component but 17% for sedentary

Question 3

RMR

Answer 3

• 75% of TEE in sedentary people
• Determined by lean body mass (lower % of TEE in athletes)
• Measured by indirect calorimetry
• Estimated from formulae

Question 4

TEF

Answer 4

• 8% of TEE
• Protein > Carb > Fat energy cost for foods
• Measured by indirect calorimetry

Question 5

EEPA

Answer 5

• 30-40% of TEE
• NEAT are the fidgety things you do
• Ratio of work to total energy = exercise/work efficiency
• Measured using pedometers, accelerometers or GPS
• Estimated by questionnaires

Note that TEE can be measured by “doubly labeled water”

Question 6

Energy Intake

Answer 6

Brain decides what, how much, and how often you eat.

• Based upon assessment of energy stores
• Based upon circulating hormones and nutrient levels.
  Stable weight: TEE=EI

Note: most people under-report food intake by 20-40%

Question 7

3 Key Nutrient Molecules

Answer 7

1. Glucose
2. FA
3. AAs

Question 8

3 ways nutrients are stored within the body

Answer 8

1. Fat
2. Glycogen
3. Protein

Fat stores have the most energy (120,000 kcal) and Carbs next (2,000 kcal)

Question 9

A loss of ___ of body protein is associated with severe malnutrition

Answer 9

30%

Question 10

Ways to estimate body fat

Answer 10

1. BMI
2. Skin fold thickness
3. Bioelectrical impedance
4. Body density measurements
5. DEXA

Question 11

If an individual is in protein balance, and fat and carbohydrate are overfed then ___ will be preferentially ____ and ___ will be stored

Answer 11

Carbohydrate is preferentially oxidized and fat will be stored.

• Smaller capacity for storing excess carbohydrate as glycogen
• Ppl in positive energy balance tend to accumulate body fat

Question 12

What gets broken down in negative energy balance and why?

Answer 12

• glycogen and protein in muscle to provide AA that can be converted to glucose for use by the brain
• lack of bio-molecules can result in organ dysfunction and disease

Question 13

Fed vs. Fasting
Anabolic vs. Catabolic
Positive vs. Negative Energy Balance

Answer 13

1. Fed vs. Fasted - with regard to the organism having eaten a meal.
   
   • Fed: insulin high, glucagon low
   • Fasted: insulin low, glucagon high
2. Catabolic vs. Anabolic
   
   • Catabolic: break down complex molecules
   • Anabolic: build complex molecules from simple ones
3. Postive vs. negative - similar to fed and fasted, but include states like exercise

Question 14

3 compartments to remember

Answer 14

1. Cytoplasm
2. Intracellular storage pools (glycogen, triglycerides, proteins)
3. Mitochondria

Question 15

9 Main Pathways

Answer 15

1. Glycolysis
2. TCA Cycle
3. Electron Transport
4. Gluconeogenesis
5. Glycogen
6. Pentose Phosphate Pathway (HMP Shunt)
7. De Novo Lipogenesis
8. Beta-oxidation and Ketogenesis
9. Urea Cycle