Week 7 - Metabolism and Energy Balance

Catabolism and Anabolism

Catabolism - Breaking down of molecules

Anabolism - Building larger molecules

Quick energy

Pyruvate —> lactate

• anaerobic without O2

When O2 is available,

• lactate —> pyruvate

Glucose undergoes _____ to form _____

glycolysis

pyruvate

REVERSIBLE

Pathway of lactate

(Liver converts it into glucose —> fed to muscles) ONGOING cycle

• cori cycle allows our body to continuously produce energy anaerobically during strenous exercise

Slow release of energy

Pyruvate —> acetyl-CoA (aerobic)

• ONE way ONLY!

Fats (Glycerol + Fatty acids)

Stores twice the energy per unit compared to protein and carbs

Glycerol (3 carbon compound)

• easily converted into glucose/pyruvate because both are 3 carbon compounds

Fatty acids

• break down directly into acetyl-CoA via beta oxidation

• beta oxidation splits 2 carbon atoms and converts it to form acetyl CoA

Amino acids

Build protein, synthesize hormones and NT

• oxidative deamination takes place- the nitrogen-containing amino group is removed

• next step depends on the amino acid (pyruvate, acetyl coa, TCA cycle)

Satiety vs Satiation

Satiety - feeling of being full after a meal

Satiation - stops us from eating during a meal

Amount of energy used in a day is based on

1.Basal metabolism - basic processes (50-65%)

2.Physical activity (30-50%)

3.Thermic effect of food - energy used to process food, depends on composition (10%)

Estimated energy requirement

BMR x activity factor x injury factor

Basal metabolic rate

Male: (10 x weight kg) + (6.25 x height cm) - (5 x age yrs) + 5

Female: (10 x weight kg) + (6.25 x height cm) - (5 x age yrs) - 161

Feasting

excess protein —> inefficient (metabolically costly)

excess glucose —> inefficient (metabolically costly)

excess fats —> efficient (stored directly with little energy loss)

What is fasting and what are the 3 key adaptations to make up for the lack of energy?

Not meeting energy requirements

1. Glucose production ( from amino acids and glycerol)

2. Alternate fuel (bodies back up brain fueled by ketone bodies, shift to ketosis)

• causes suppresion of appetite

• hormones slow metabolism

3. Energy conservation - symptom of starvation

• muscle wasting

• decrease heart rate, respiratory etc..

• impaired vision

What happens after 24 hours

glycogen stores dwindle, body breaks down protein in muscle and lean tissue to amino acids to synthesize glucose for the brain and nervous system

• liver converts fats to ketone bodies as an alternative source of energy for the brain

• ketosis induced by insufficient carbohydrate intake

What is appetite?

Desire to eat without feeling hungry

Reduce satiation

• foods high in fructose (desserts)

Which metabolic reaction occurs when a cell uses energy

ATP releases a phosphate group and becomes ADP

During the first few days of a fast what energy source provides about 90% of the glucose needed to fuel the body

Protein