metabolism

Define (a) Anabolism (b) Catabolism

Anabolism: synthesis of large molecules from smaller ones, energy is absorbed; –genesis

Catabolism: breakdown of large molecules into smaller ones, energy is released; –lysis

Name and discuss glucose catabolism in (a) the absence of O2 (anaerobic) (b) in the presence of O2 (aerobic). Name and discuss the 3 sequential processes of cellular respiration

absence of O2/anaerobic: pyruvic acid converted into lactic acid; can lead to metabolic acidosis

presence of O2/aerobic: cellular respiration – 3 sequential processes:

1) Glycolysis: 10-step process in the cytosol that breaks down glucose into pyruvate

2) Citric Acid/Krebs Cycle: in mitochondrial matrix, turns twice for each glucose molecule

3) Electron Transport Chain: final stage of aerobic respiration to generate majority of theATP

What’s the net ATP produced in glycolysis? What’s the net ATP produced in anaerobic respiration? What’s the net ATP produced in aerobic respiration?

glycolysis: 2

anaerobic respiration: 2

aerobic respiration: 2/glucose molecule

Name and define two processes of glucose anabolism; what is the storage form of glucose in human cells? What are non-carbohydrate sources?

1) Glycogenolysis: synthesis of glycogen from glucose-6-phosphate stimulated by glycogen synthase

2) Gluconeogenesis: production of glucose from non-carbohydrate sources which occurs in liver

Storage form of glucose in human cells (specifically skeletal muscle & hepatocytes): glycogen

Non carbohydrate sources/Substrates for gluconeogenesis: lactate from pyruvic acid (pyruvate) from anaerobic respiration, glycerol (from lipolysis), amino acids (from protein breakdown)

Lipid Metabolism: Discuss (a) Lipogenesis (b) Lipolysis; what is beta oxidation? What are the ketone bodies?

a) Lipogenesis: anabolic process of converting excess glucose into triglycerides for storage once glycogen stores (limit 600g) are full

b) Lipolysis: catabolic breakdown of stored triglycerides into glycerol (energy production & gluconeogenesis) & fatty acids

c) Beta Oxidation: specific catabolic process by which fatty acids are broken down into smaller molecules like Acetyl CoA to enter the Krebs cycle

d) Ketone Bodies: acetone, acetoacetic acid, beta-hydroxybutyric acid; formed from fatty acids via an anabolic process = ketogenesis.

Protein Metabolism: (a) protein synthesis (b) protein breakdown; what is transamination?

protein synthesis: anabolic process of building proteins from amino acids, stimulated by insulin & growth hormone

protein breakdown: catabolic process of breaking down proteins into amino acids

TRANSAMINATION: reaction for the removal of an amine group where an amino acid & a keto acid are converted into a new amino acid & a new keto acid

Discuss the hormonal control of metabolism: Insulin, Cortisol, Glucagon, Catecholamines (Epinephrine and Norepinephrine), Growth hormone

Insulin: anabolic & HYPOglycemic hormone released in response to hypoglycemia (fed state) ⇒ lowers blood glucose levels by stimulating glucose uptake, glycogenesis, lipogenesis, & protein synthesis while inhibiting gluconeogenesis(anabolic process INHIBITED by insulin); glycolysis(catabolic process STIMULATED by insulin)

Cortisol: HYPERglycemic hormone released in response to hypoglycemia; major gluconeogenic hormone; stimulates protein catabolism in skeletal muscles to provide amino acids for gluconeogenesis & stimulates protein synthesis in liver to synthesize enzymes for gluconeogenesis

Glucagon: HYPERglycemic hormone released in response to hypoglycemia (fasting state); stimulates glycogenolysis, lipolysis, gluconeogenesis

Catecholamines(Epinephrine/Norepinephrine): HYPERglycemic hormones released in response to hypoglycemia; stimulate glycogenolysis & lipolysis to increase available energy sources

Growth hormone: HYPERglycemic hormone released in response to hypoglycemia; stimulates protein synthesis, lipolysis, gluconeogenesis; (all 4 = negative feedback to increase blood glucose levels by stimulating glycogenolysis, lipolysis, gluconeogenesis)