Lecture - Biochemical Synthesis 1

Question 1

Key biochemical species

Answer 1

• amino acids

- fatty acids

Question 2

NEcesary precursors

Answer 2

• Purines
• Pyrimidines
• Ribose
• Cholesterol
• Porphyrins

Question 3

Energy rich compounds for storage or export

Answer 3

• Fatty acids

- Ketone bodies

Question 4

Providion of reducing power

Answer 4

• NADH
• NADPH
• Glutathione

Question 5

DEtoxification and excretion

Answer 5

• Urea
• Mono-oxygenases
• glucuronidation

Question 6

Biochemical species that cannot be synthesized

Answer 6

• Vitamins (except vit D)
• Essential amino acids
• essential fatty acids

Question 7

Essential and non-essential amino acid

Answer 7

• Essential aa: required in diet, cannot be synthesized

- non essential aa: not required in fiet, synthezised from ingested precursors

Question 8

Essential amino acids

Answer 8

• lysine
• histidine
• threonine
• methionine
• Phenylalanine
• Tryptophan
• Isoleucine, Leucine, Valine

Question 9

Non essential amino acid

Answer 9

• Arginine
• Aspartate
• Glutamate
• Asparagine
• Glutamine
• Alanine
• GLycine
• Serine
• Cysteine
• Proline
• Tyrosine

Question 10

Conversion of L-phenylalanine to L-tyrosine

Answer 10

• requires phenylalanine hydroxylase

- requires vitamine B

Question 11

Synthesis of neurotransmitters from L-tyrosine

Answer 11

• tyrosine hydroxylase
• dopa decarboxylase
• dopamine b-hydroxyklase
• PNMT
• forms dopa then dopamine then norepinephrine and then epinephrine

Question 12

Example of aa synthesis : Glutamate

Answer 12

• Glutamate can form a-ketoglutarate via the glutamate dehydrogenase enzyme
• glutamate is a precursor for several other AA: Glutamine, Proline, Arginine

Question 13

Synthesis of FA: two important carriers

Answer 13

• coenzyme A

- Acyl carrier protein (ACP)

Question 14

Synthesis of FA: the committed step

Answer 14

• when acetyl coA becomes malonyl co A (2C -> 3C)

- acetyl coA receives a carbon dioxide froup from bicabonate

Question 15

Synthesis of FA: fatty acid dynthase complex

Answer 15

After malonyl coA, becomes condensed into 1C

• then a bunch of reductions forms butyryl ACP
• after butyryl ACP is formed, chain length increases by two carbons each cycle
• maximum chain length via Fatty acid synthase complex is 16C

Question 16

3 ways to nomenclature fatty acid

Answer 16

• numbering from COOH: 1
• numbering from carbon after COOH: a,b,y,w
• Numbering from last carbon: w1, w-2…

Question 17

Synthesis of longer chain FA and desaturation

Answer 17

• some very long chain FA required for membrane function
• desaturation: insertion of double bonds
• enzymes on cytoplasmic face of ER facilitate elongation and desaturation reaction

Question 18

Cis vs trans fatty acid

Answer 18

CIS

• kinked
• natural form and major configuration in natuyre
• can synthesize ourselves, melting temp drops - more liquid

TRANS

• not kinked
• possible to make synthetically
• tend to pack and crystallize early

Question 19

Essential fatty acids

Answer 19

• unsaturated FA with double bond beyoung C9
• desaturating enzymes cannot process this far from C1
• some essential fatty acids are required for synthesis of important biochemicals

N6- can be obtained in a wide variety of food
N3- more limited

Question 20

Synthesis of cholesterol

Answer 20

• Acetyl coA -> Aetoacetyl coA -> HMG CoA -> Mevalonate
• statins inhibit HMG CoA to mevalonate : lower cholesterol but secondary effect include enhanced clearance of cholesterol rich lipoproteins
• Mevalonate -> C5 -> C10 -> C15 -> C30 (sqalene) -> C27 (cholesterol)

Question 21

Synthesis of C10 and C15 is suppressed by biphosphonates

Answer 21

• but C15 is needed for protein prenylation (Ras) and Heme A (coenzyme Q10)

Question 22

What is synthesized from cholesterol?

Answer 22

• steroids

- bile salts