metabolism

Question 1

Define the terms metabolism, catabolism, anabolism, and identify the nutrients the body is able to use for fuel

Answer 1

• metabolism: chem. rxns of broken down and synthesis
• catabolism: breaking down a substance into smaller parts ( net result: energy release)
  - uses: glucose: FA, AA if needed
• anabolism: smaller compounds joined to make a larger compound (net result: energy use)
  - uses: AA, FA, glucose

Question 2

Explain the catabolic processes (anaerobic and aerobic) of breaking down glucose to produce
ATP

Answer 2

• anaerobic: glycolysis, occurs in the cytosol, yields 2 ATP/ glucose molecule
• aerobic: CAC/ ETC, occurs in the mitochondria, yields 30 ATP/glucose
  total 32 ATP/glucose

Question 3

Explain the catabolic process of breaking down fatty acids to produce ATP

Answer 3

1. the FA is bound to a Co-A
2. beta-oxidation occurs–> the FA chain is oxidized by NAD+ and FAD+, two carbons are removed
3. products of b-oxidation is FADH2, NADH, acetyl Co-A, and FA with fewer carbons –> FADH2 and NADH go to ETC, and acetyl Co-A go to CAC –> produce ATP
4. CoA binds to shorter FA and rounds of b-oxidation occur till its just acetyl Co-A

fat(triglycerides) –lipolysis–> FA –b-oxidation/CAC/ETC–> ATP

Question 4

Explain the catabolic process of breaking down amino acids to produce ATP

Answer 4

1. amino group removed from the AA and transferred to a a-ketoglutarate (transamination)
2. produces a carbon skeleton, and AA glutamate
3. carbon skeleton converted into compounds, which is oxidized
4. in the mitochondria of the hepatocyte, glutamate undergoes oxidative deamination, producing NH3 and a-ketoglutarate
5. some amino groups removed as ammonia are used int the synthesis of the new AA
6. remaining ammonia molecules are removed by the urea cycle which forms urea that is eliminated in the urine

proteins –> AA –> transamination –> pyruvate/ acetyl Co-A/ glucose/ other AA –>ATP

Question 5

Describe the processes of glycogenesis, glycogenolysis, and gluconeogenesis

Answer 5

• Glycogenesis: Conversion of glucose into glycogen for storage, primarily in the liver and muscles, facilitated by enzymes like glycogen synthase and branching enzyme.
• Glycogenolysis: Breakdown of glycogen into glucose-1-phosphate and glucose, releasing glucose into the bloodstream, primarily in the liver and muscles, mediated by enzymes like glycogen phosphorylase and debranching enzyme.
• Gluconeogenesis: Synthesis of glucose from non-carbohydrate precursors like lactate, glycerol, and amino acids, occurring mainly in the liver, facilitated by enzymes like pyruvate carboxylase and phosphoenolpyruvate carboxykinase.

Question 6

Describe the process by which fatty acids are synthesized and stored as triglycerides in adipose
tissue

Answer 6

• lipogenesis: process used to make FA and glycerol (from glucose) and/or to store triglyceride adipose
  1. glycerol made from glucose via glycolysis
  2. FA made when 2-carbon acyl units from acetyl Co-A are linked together
  3. one glycerol plus 3 FA make a triglyceride
• uses FA synthase

Question 7

Explain how nutrients may be converted to amino acids and lipids if needed

Answer 7

broken down and used if needed then stored if not needed

Question 8

Explain the metabolic fate of excess dietary proteins and carbohydrates

Answer 8

• Excess Dietary Proteins:
  - Broken down into amino acids during digestion.
  - Amino acids not immediately used for protein synthesis are converted to other compounds.
  - Excess amino acids can be deaminated and converted into intermediates for energy production or stored as fat.
• Excess Dietary Carbohydrates:
  - Converted into glucose during digestion.
  - Glucose is either used for immediate energy needs, stored as glycogen in the liver and muscles for short-term energy storage, or converted into fatty acids and stored as fat for long-term energy storage.
  - Excess glucose can also be converted into glycerol for triglyceride synthesis.

Question 9

Summarize the processes that occur in the absorptive (fed) and postabsorptive (fasted) states,
including the roles of insulin and glucagon

Answer 9

• absorptive (fed): as soon as nutrients are absorbed from the small intestine and enter the blood, lasts up to 4 hours
  - nutrients for immediate energy production, anabolic M to excess
  - insulin triggers glucose uptake by body cells and promotes anabolic M
• postabsorptive (fasted): no more nutrients available
  - catabolic M dominates
  - glucagon triggers catabolic M