Intro To Metabolism

Question 1

Interconversion of chemical compounds in the body, the pathways taken by individual molecules, their interrelationships, and the mechanisms that regulate the flow of metabolites through the pathways

Answer 1

Metabolism

Question 2

Three categories of metabolic pathways

Answer 2

1. Anabolic pathways
   - synthesis of larger and more complex compounds from smaller precursors
   - endothermic
2. Catabolic pathways
   - breakdown of larger molecules commonly involving oxidative reactions
   - exothermic
   - producing reducing equivalents
   - mainly via respiratory chain, ATP
3. Amphibolic pathways
   - occur at the crossroads of metabolism
   - act as links between anabolic and catabolic pathways (e.g. CAC)

Question 3

A 70 kg adult human being requires how much MJ or kcal a day?

Answer 3

8-12 MJ or 1920-2900 kcal

Question 4

Obesity vs emaciation?

Answer 4

If intake of metab fuels is consistenly greater than energy expenditure = surplus stored, largely as TAG in adipose tissue leading to OBESITY

If intake of metab fuels is consistenly lower than energy expenditure = negligible reserves of fat, carbs, and aa arising from protein turnover are used for energy-yielding metab rather than replacement protein synthesis leading to EMACIATION, wasting, and, eventually, death

Question 5

Gluconeogenesis

Answer 5

Process of synthesizing glucose from noncarbohydrate precursor (e.g. lactate, aa, and glycerol).

Question 6

What controls the extent to which tissues take up and oxidize glucose and formation & utilization of TAGs and Glycogen?

Answer 6

Insulin and glucagon

Question 7

Types of Diabetes

Answer 7

Diabetes Mellitus
Type I: impaired synthesis and secretion of insulin

Type II: impaired sensitivity of tissues to insulin action

Question 8

All products are digested to a common product ____ which is oxidized by ___.

Answer 8

1. Common product: acetyl-CoA

2. Oxidized by CAC

Question 9

Pathway that is a source of ribose for nucleotide and nucleic acid synthesis and source of reducing equivalents (NADPH) for FA synthesis

Answer 9

Pentose Phosphate Pathway

Question 10

Triose phosphate intermediates in glycolysis give rise to

Answer 10

Glycerol moiety of TAGs

Question 11

Body’s main fuel reserve

Answer 11

TAG

Question 12

FA may be oxidized to ___ (Beta-oxidation)

Answer 12

Acetyl-CoA

Question 13

Three fates of Acetyl-CoA which underwent beta-oxidation

Answer 13

1. Acetyl-CoA from glycolysis —> Oxidized to CO2 + H2O via CAC
2. Precursor for cholesterol and other steroid synthesis
3. In the liver, used to form ketone bodies, acetoacetate, 3-hydroxybutarate (impt fuels in prolonged fasting and starvation)

Question 14

Essential vs Nonessential amino acids; Dispensable vs. Indispensable amino acids?

Answer 14

Essential (Indispensable) Amino Acids - must be supplied in the diet because they CANNOT be synthesized by the body

Nonessential (Dispensable) Amino Acids - supplied in diet but can be formed from metabolic intermediates by TRANSAMINATION (using amino group from other amino acids)

Question 15

After deamination, amino nitrogen is excreted as?

Carbon skeletons remaining after transamination may be what? (3)

Answer 15

1. Urea
2. Carbon skeleton remaining may be:
   A. Oxidized to CO2 via CAC
   B. Used to synthesize glucose (gluconeogenesis)
   C. Form ketone bodies or acetyl-CoA which may be oxidized or used for FA synthesis