MCAT Biochemistry Ch. 12 Bioenergetics & Regulation of Metabolism

Proceeds through ATP cleavage, which is transfer of high-energy phosphate group from ATP to another molecule. This activates or inactivates the target molecule. The overall free energy of the reaction can be determined by taking the sum of the free energies of the individual reactions.

• Soluble
  • NADH, NADPH, FADH₂, ubiquinone, cytochromes, & glutathione
• Membrane-Bound
  • FMN, bonded to complex I of the electron transport chain
• * Flavoproteins

Subclass of electron carriers in mitochondria & chloroplasts derived from riboflavin (vitamin B2)

• Flavin Adenine Dinucleotide (FAD)
• Flavin Mononucleotide (FMN)

Insulin secretion high, anabolic metabolism prevails

Observed in short-term fasting overnight, transition to catabolic metabolism

• Insulin secretion decreases
• Glucagon & catecholamine secretion increases

• Dramatic increase in glucagon & catecholamine secretion
• Most tissues rely on fatty acids
• At maximum, 2/3 of the brain's energy can be derived from ketone bodies
  • Red blood cells still rely completely on glucose for energy

• Blood Glucose
  • Insulin: decreases blood glucose by increasing cellular uptake
  • Glucagon: increases blood glucose by promoting gluconeogensis & glycogenolysis of the liver
• Secretion:
  • Insulin: pancreatic β-cells, regulated by blood glucose levels
  • Glucagon: pancreatic α-cells, stimulated by low glucose & high amino acid levels
• Anabolic Metabolism
  • ​Insulin increases rate

Increase blood glucose in response to stress by:

• Mobilizing fat stores (lypolysis)
• Inhibiting glucose uptake
• Increasing impact of glucagon & catecholamines

Act through sympathetic nervous system to:

• Promote glycogenolysis
• Increase basal metabolic rate

Modulate impact of other metabolic hormones & have direct impact on basal metabolic rate

• T₃: more potent than T₄, but has shorter duration of activity & available in lower concentrations in blood
• T₄: effect on metabolic rate has latency of several hours but may last for several days; precursor to T₃ converted to T₃ at the tissues

• Maintain blood glucose levels by glycogenolysis & gluconeogenesis in response to pancreatic hormone stimulation

• Stores lipids under influence of insulin
• Releases lipids (lipolysis) under influence of epinephrine

Metabolism differs based on current activity & fiber type

• Resting Muscle:
  • Conserves carbs in glycogen stores
  • Uses free fatty acids from bloodstream
• Active Muscle:
  • May use anaerobic metabolism
    • short, high intensity exercise
  • May use oxidative phosphorylation of glucose
    • half and half w/ fatty acid oxidation for first hour of steady state exercise
  • May use direct phosphorylation for creatine phosphate
    • short burst, high intensity
  • May use fatty acid oxidation
    • half & half glucose for first hour steady state exercise
    • all fat in exercise lasting over 1 hour)

Uses fatty acid oxidation in both well fed & fasting states

Consume glucose in all metabolic states except starvation, where up to 2/3 of brain's fuel can come from ketone bodies