W1 Basics of Metabolism

Question 1

4 pathways to metabolize dietary components

Answer 1

fuel oxidative pathways

fuel storage and mobilisation pathways

biosynthetic pathways

detoxification/waste disposal pathways

Question 2

two advantages of storing energy in form of fatty acids

Answer 2

1. carbon in fatty acids almost completely reduced > oxidation yield more energy
2. not as hydrated as monosaccharides > can pack more closely in storage tissues

Question 3

relationship between melting point and degree of unsaturation in fatty acids

Answer 3

higher degree > more kinks > cannot pack closely + van Der Waals less effective > less stable > lower melting point

Question 4

angles representing N-C and C-C bonds

Answer 4

N-C: phi
C-C: psi

Question 5

definition of pKa value

Answer 5

pH at which half the molecules of an amino acid in solution have side chains that are charged, half are uncharged

Question 6

two types of coenzymes

Answer 6

1. activation-transfer: participate directly in catalysis by forming covalent bond with a portion of the substrate
2. oxidation-reduction: transfer of electrons

Question 7

examples of activation-transfer coenzymes

Answer 7

thiamine pyrophosphate, coenzyme A, biotin and pyridoxal phosphate

Question 8

definition of Vmax and Km

Answer 8

Vmax: maximal velocity that can be achieved at an infinite concentration of substrate

Km: concentration of substrate required to reach half Vmax

Question 9

definition of heterotropic interaction

Answer 9

effector molecules different from substrate molecules

Question 10

definition of homotropic interaction

Answer 10

when binding of one substrate molecule to an active site alters binding properties of other identical substrate molecules in the same enzyme

Question 11

phosphorylation of -OH of which amino acids are reversible, covalent changes?

Answer 11

Ser, Thr or Tyr

Question 12

main signals used to regulate metabolism

Answer 12

insulin, glucagon, catecholamine, glucocorticoids and growth hormone

Question 13

three organisations of multi enzymes carrying out a metabolic pathway

Answer 13

1. enzyme may exist as physically separate, soluble entities
2. enzymes of a pathway are collected to form a discrete multi enzyme complex
3. enzymes common to a pathway reside together as a membrane-bound system

Question 14

advantages of compartmentalising particular metabolic pathways within specific organelles

Answer 14

regulate uncontrolled behaviour

diffusion restricted, product of one reaction is released close to the next enzyme in a pathway

selective permeability of membrane can control rate of movements of metabolites

ion-gradients formed by certain enzymatic reaction can influence other enzymatic reactions

Question 15

what are some common electrophiles

Answer 15

protonated imines, phosphate groups and protons

Question 16

what are some common nucleophiles

Answer 16

oxyanions, carbonions, deprotonated amines, imidazole side chain of histidine