MEDICAL BIOCHEMISTRY: LECTURE NOTES
WEEK 1:
Lecture 1: Human Metabolism
● Carbohydrates:
○ (glucose) only source of food our brain can use
● Proteins:
○ made of amino acids (combined through peptide
bonds)
■ used to make glucose
● Fat/triglycerides
○ palmitate = energy source
● The Big Three Metabolites:
○ Glucose 6-phosphate
○ Pyruvate
○ Acetyl CoA
● Sources of Acetyl CoA:
○ fatty acid (palmitate)
○ ketone body /acetoacetate
○ glucose
○ pyruvate
○ ethanol
○ amino acid (alanine) = indirectly
,● Fates of Fuels:
○ glucose
■ oxidation → energy
■ storage → glycogen
■ synthesis → many compounds
○ Amino acids
■ oxidation → energy
■ storage → no storage (turn into fat/protein)
■ synthesis → protein and nitrogen compounds
○ Fats
■ oxidation → energy
■ storage → TG (not regulated)
■ synthesis → membrane lipids
● Energy carriers:
○ ATP
○ GTP
○ NAD(P)H (NADH from TCA cycle)
○ FADH
● Acetyl CoA:
○ two carbons released as CO2
○ hydrogens released ad H2O
● ATP:
○ has High Energy Phosphate Bonds
■ broken to release energy
● Endothermic vs. Exothermic reactions:
○ Exothermic = generate energy (release it)
○ Endothermic = require energy (take it up)
● Mitochondria:
○ Outer membrane
○ Inner membrane
■ Electron transport chain (ETC)
■ ATP Synthase = generate ATP
■ B-oxidation of Fatty acids = degrade FA
● synthesis in cytosol
● How does the body regulate ATP synthesis?
○ ATP synthase uses energy from proton gradient
(protons from NADH)
, ■ converts ADP to ATP
● when all is converted = No NADH → NAD+ = NO TCA cycle
○ need NAD+ to form a-ketoglutarate (part of TCA cycle)
● accumulation of NADH = NO TCA cycle
○ due to stop recycling by OXPHOS
● Enough ATP:
○ excess Acetyl CoA and citrate → fatty acids
● After a meal:
● Between meals: release energy
○ release Amino acids
○ release TG
○ protein break down = urine is yellow due to urea (negative nitrogen balance)
, ● Negative nitrogen
balance = protein breakdown (after good night sleep)
○ amino acids are used in the liver to make glucose for the brain (only source of
energy)
○ nitrogen excretion (release of urea) is very high after 12 h of fasting
● Back up system: Ketone bodies
○ examples: B-hydroxybutyrate, acetoacetate
○ generated from fatty acids
○ produced after long starvation (3 days)
■ can be used by the brain
○ prevent breakdown of essential proteins
WEEK 1:
Lecture 1: Human Metabolism
● Carbohydrates:
○ (glucose) only source of food our brain can use
● Proteins:
○ made of amino acids (combined through peptide
bonds)
■ used to make glucose
● Fat/triglycerides
○ palmitate = energy source
● The Big Three Metabolites:
○ Glucose 6-phosphate
○ Pyruvate
○ Acetyl CoA
● Sources of Acetyl CoA:
○ fatty acid (palmitate)
○ ketone body /acetoacetate
○ glucose
○ pyruvate
○ ethanol
○ amino acid (alanine) = indirectly
,● Fates of Fuels:
○ glucose
■ oxidation → energy
■ storage → glycogen
■ synthesis → many compounds
○ Amino acids
■ oxidation → energy
■ storage → no storage (turn into fat/protein)
■ synthesis → protein and nitrogen compounds
○ Fats
■ oxidation → energy
■ storage → TG (not regulated)
■ synthesis → membrane lipids
● Energy carriers:
○ ATP
○ GTP
○ NAD(P)H (NADH from TCA cycle)
○ FADH
● Acetyl CoA:
○ two carbons released as CO2
○ hydrogens released ad H2O
● ATP:
○ has High Energy Phosphate Bonds
■ broken to release energy
● Endothermic vs. Exothermic reactions:
○ Exothermic = generate energy (release it)
○ Endothermic = require energy (take it up)
● Mitochondria:
○ Outer membrane
○ Inner membrane
■ Electron transport chain (ETC)
■ ATP Synthase = generate ATP
■ B-oxidation of Fatty acids = degrade FA
● synthesis in cytosol
● How does the body regulate ATP synthesis?
○ ATP synthase uses energy from proton gradient
(protons from NADH)
, ■ converts ADP to ATP
● when all is converted = No NADH → NAD+ = NO TCA cycle
○ need NAD+ to form a-ketoglutarate (part of TCA cycle)
● accumulation of NADH = NO TCA cycle
○ due to stop recycling by OXPHOS
● Enough ATP:
○ excess Acetyl CoA and citrate → fatty acids
● After a meal:
● Between meals: release energy
○ release Amino acids
○ release TG
○ protein break down = urine is yellow due to urea (negative nitrogen balance)
, ● Negative nitrogen
balance = protein breakdown (after good night sleep)
○ amino acids are used in the liver to make glucose for the brain (only source of
energy)
○ nitrogen excretion (release of urea) is very high after 12 h of fasting
● Back up system: Ketone bodies
○ examples: B-hydroxybutyrate, acetoacetate
○ generated from fatty acids
○ produced after long starvation (3 days)
■ can be used by the brain
○ prevent breakdown of essential proteins
