3.2. METABOLISM OF
MACRONUTRIENTS
IB SEHS
Starter
• Where do we get our energy from?
• How do we save energy?
Learning Objectives
Everyone will be able to
1. Distinguish between metabolism, anabolism
and catabolism.
2. State what glycogen is and its major sites of
storage
Energy metabolism
Metabolism are all the biochemical reactions in
living organisms required for the maintenance of
life. There are two different phases:
1. Anabolism: Construction. Conversion of
smaller molecules into larger ones. Requires Energy.
Ex: glucose into glycogen.
2. Catabolism: Destruction. Larger molecules
are converted into smaller ones. Release of Energy.
Ex: Triglycerids convert to glycerol and fatty acids.
Glycogen
• Glycogen is the storage form of glucose.
• Main storage location: Stored in the liver &
skeletal muscle
• Glycogenesis: Formation of glycogen out of
glucose molecules linked.
• Glycolysis: Glycogen is broken into pyruvate
and ATP
Metabolism of Glycogen
Triglyceride storage
• Make up 95 % of dietary fat
• One molecule = One glycerol molecule
+ Three fatty acids
• Main storage location: Adipose tissue &
skeletal muscle
• β- oxydation: Release of energy from breaking
down fatty acids to acetyl CoA
Hormonal regulation of energy
metabolism
• Hormones involved: Insulin, glucagon, cortisol
and growth hormones.
• Insulin role: After a meal, glucose in blood
rises, pancreas secretes insuline from its βcells, which increases the transport of glucose
into cells (muscle and liver) which promotes
glycogenesis.
Hormonal regulation of energy
metabolism
• Glucagon role: During fasting or exercise,
glucose in blood decreases, glucagon secreted
by α-cells from pancreas, promoting
glycogenolysis and lipolysis for energy supply.
• Adrenaline: Also increases with low glucose
levels and also promotes glycogenolysis and
lipolysis
Muscle glucose uptake during exercise
• Muscle contraction during exercise stimulates
translocation of glucose transporters from
inner cell into cell membrane, increasing the
uptake of glucose from blood.
• Insuline also stimulates glucose uptake from
blood BUT DURING PHASES OF NO EXERCISE