Lecture One And Two

Question 1

Define the components of your daily energy expenditure

Answer 1

1. Basal metabolic rate - the minimum energy required to sustain life
2. Energy for voluntary physical activity (+30/65/100%)
3. Diet-induced thermogenesis - energy required to process the food we eat

Question 2

Give approximate values for your daily energy expenditure:

Answer 2

Assuming moderate physical activity:
- a 70kg man = 12,000 kJ
- a 58kg woman = 9,500 kJ

Question 3

What are the essential dietary components?
Why are they essential?

Question 4

Explain the clinical consequences of protein deficiency in humans:

Answer 4

Kwashiorkor:
- symptoms include: apathetic, lethargic, anorexic
- There is generalised oedema and the abdomen is distended
- Serum albumin is low and anaemia is common

Question 5

Explain the clinical consequences of energy deficiency in humans:

Answer 5

Marasmus:
- The child (typically under 5) looks emaciated with obvious signs of muscle wasting and loss of body fat
- There is no oedema
- Symptoms: thin and dry hair, diarrhoea , anaemia

Question 6

What is the formula for BMI?

Answer 6

BMI = weight (kg) / height2 (m2)

Question 7

What are the BMI values?

Answer 7

1. Underweight = <18.5
2. Desirable weight = 18.5-24.9
3. Overweight = 25-29.9
4. Obese = 30-34.9
5. Severely Obese = >35

Question 8

Define obesity

Answer 8

• excessive fat accumulation in the adipose tissue which impairs health
• result of energy intake exceeding expenditure over a period of years

Question 9

Describe the factors involved in body weight regulation

Answer 9

Energy Expenditure = Energy Intake
- if intake exceeds expenditure, weight will increase
- if expenditure exceeds intake, weight will decrease

Question 10

Define cell metabolism

Answer 10

The chemical processes that occur within a living organism in order to maintain life.

Question 11

Explain the functions of cell metabolism:

Answer 11

1. Oxidative pathways - convert food into energy
2. Fuel storage and mobilisation - mobilise energy stores (glycogen) when not eating but increased energy required
3. Biosynthetic pathways - produce basic building blocks for cells
4. Detoxification pathways - remove toxins

Question 12

Describe the relationship between catabolism and anabolism

Answer 12

Catabolism - break down larger molecules into smaller ones, releasing energy, H atoms, and reducing power. They are oxidative pathways.

Anabolism - synthesise larger important molecules, using energy and H atoms from catabolism. They are reductive pathways.

Question 13

Why do cells need a continuous supply of energy?

Answer 13

There is a limited amount of ADP and ATP in the cell and the [ATP] is only sufficient for a few seconds of energy. Therefore ATP must be rapidly resynthesised from ADP using the free energy released during catabolism of fuel.
The rate of cellular ATP turnover is very high.

Question 14

Explain the roles of redox reactions within metabolism

Answer 14

• Oxidation is the loss of a hydrogen atom/electrons
• Reduction is the gain of a hydrogen atom/electrons
• These reactions always accompany one another
• When fuel molecules are oxidised, H atoms are initially transferred to carrier molecules which become reduced.

Question 15

Explain the roles of H-carrier molecules in metabolism

Answer 15

• Carrier molecules must cycle between ox and red processes to maintain cell function so act as carriers of reducing power
• OX FORM - NAD+, NADP+, FAD
• RED FORM - NADH + H+, NADPH + H+, FAD2H

Question 16

Explain the biological role of ATP

Answer 16

• the main source of energy within cells (currency)
• this is due to the high energy of bond hydrolysis of the phosphate groups
• it is stable is the absence of specific catalysts so the flow of energy can be controlled

Question 17

Explain the biological role of creatine phosphate (phosphocreatine)

Answer 17

• an energy store that can quickly be mobilised to increase metabolic activity
• creatine + ATP <—> creatine phosphate + ADP
• if [ATP] falls suddenly, the reaction reverses providing short-term boosts

Question 18

Explain the biological role of creatine kinase

Answer 18

• useful clinical marker of muscle damage - appears in blood after cell damage
• usually found in the cytoplasm of cells

Question 19

Explain the biological role of creatinine

Answer 19

• a breakdown product of creatine and creatine phosphate, usually produced at constant rate
• of muscle is wasting or damaged, it is excreted via the kidneys as urine
• can be used to assess kidney function and provide a measure of muscle mass

Question 20

What are the high energy signals?

Answer 20

• ATP
• NADH
• NADPH
• FADH2
  Reduced forms of the molecules

Question 21

Explain the roles of high energy signals in the regulation of metabolism

Answer 21

Activate anabolic pathways as there is sufficient energy in the cell for its requirements.

Question 22

What are the low energy signals?

Answer 22

• ADP/AMP
• NAD+
• NADP+
• FAD
  Oxidised form of molecules.

Question 23

Explain the roles of low energy signals in the regulation of metabolism

Answer 23

Activate catabolic pathways to generate more energy
- AMP is a very strong low energy signal
- with the help of adenylate kinase can increase ATP generation by glycolysis (2ADP —> ATP + AMP)
- also an activator of AMP kinase that regulates genes expression switching from anabolic to catabolic pathways