1. Unit 2: Metabolic Processes Metabolism
SBI4U – Ms. Richardson

2. Metabolic Rate
Amount of energy consumed by the organism in a given time
Measures the overall rate at which energy-yielding reactions of cellular respiration occur
Increases when work is being done

3. 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: 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

4. Metabolic Pathways We don’t eat just glucose
Molecules can enter glycolysis and the Krebs cycle at different points

5. Amino group  ammonia (waste)
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

6. 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

7. Regulation – Feedback Inhibition
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