Download Unit 2: Metabolic Processes Metabolism and Energy

Unit 2:
Metabolic Processes
Metabolism
SBI4U – Ms. Richardson
Metabolic Rate
• Amount of energy consumed by the
organism in a given time
• Measures the overall rate at which energyyielding reactions of cellular respiration
occur
• Increases when work is being done
Basal Metabolic Rate
- Minimum amount of energy on which an
organism can survive
- Accounts for 60-70% of daily energy use in
humans
- Healthy adult male:
167 kJ/m2/h
- Healthy adult female:
150 kJ/m2/h
- Determined by measuring amount of thermal
energy lost by a person’s body over time (at rest)
- Decreases with age
- Body becomes more efficient at same tasks
- Less physical activity, less muscle
Metabolic Pathways
- We don’t eat just glucose
- Molecules can enter glycolysis and the Krebs
cycle at different points
Protein Catabolism
- First digested into amino acids (absorbed and used for
protein synthesis)
- Amino group is removed (deamination)
Amino group  ammonia (waste)
- Remaining parts of amino acid converted into an
intermediate of glycolysis/Krebs cycle
- Point of entry depends on amino acid
- Eg: leucine  acetyl-CoA
Lipid Catabolism
- Triglycerides break down into
glycerol and fatty acids
- Glycerol  glucose 
glycolysis
- Glycerol  DHAP
(dihydroxyacetone phosphate)
 G3P  glycolysis
- Fatty Acids  β-oxidation 
acetyl-CoA  Krebs
- Fats provide 38 kJ/g while
carbohydrates provide 16 kJ/g
Regulation – Feedback Inhibition
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Phosphofructokinase
- Enzyme with allosteric binding site for ATP
- When ATP is present, it binds to enzyme and inhibits it
Citrate
- First product of the Krebs cycle, can pass into cytoplasm and
inhibit phosphofructokinase
- As citrate is used, concentration decreases, inhibition
decreases and rate of glycolysis increases
NADH
- High [NADH] in cell indicates high ATP production
- NADH allosterically inhibits pyruvate dehydrogenase and
reduces acetyl-CoA being fed into Krebs cycle
- NADH production decreases