Biochem- Vitamins

Front 1

How is rhodopsin formed in the eye? (start with all-trans retinal)

Back 1

All-trans retinal is converted via isomerase to 11-cis-retinal.

11-cis-retinal + opsin = rhodopsin (in retina)

Light induces the a change back to all-trans-retinal, and a this change triggers nerve impulse.

Front 2

What does light do to rhodopsin?

Back 2

Light induces a conformational change from 11-cis-retinal in rhodopsin to all-trans-retinal. This conformational change induces a nerve impulse.

Front 3

What vitamins are involved in REDOX donor/acceptor?

Back 3

23CK

Vitamin B2 (riboflavin)
Vitamin B3 (niacin)
Vitamin C (ascorbate)
Vitamin K (naphthoquinone)

Front 4

What vitamins are involved in stabilizing a transition state?

Back 4

16

Vitamin B1 (thiamin)
Vitamin B6 (pyridoxin)

They are electron sinks (escape route for the electrons). They stabilize the carbanion intermediate.

Front 5

What vitamins are involved in group transfer?

Back 5

5, 7, 9, 12, and lipoic acid.

Vitamin B5 (pantothenate)
Vitamin B7 (biotin)
Vitamin B9 (folate)
Vitamin B12 (cobalamin)

Front 6

List the names of the B vitamins.

Back 6

Vit B1 (thiamin)
Vit B2 (riboflavin)
Vit B3 (niacin)
Vit B5 (pantothenate)
Vit B6 (pyridoxin)
Vit B7 (biotin)
Vit B9 (folate)
Vit B12 (cobalamin)

Front 7

Vitamin B2 (riboflavin) is part of two important molecules. What are these two molecules?

Back 7

FAD (flavin adenine dinucleotide)
FMN (flavin mononucleotide)

Front 8

How many electrons and protons do FMN and FAD transfer in redox?

Back 8

2 electrons, and two protons. So FMN and FAD become reduced to FMNH2 and FADH2.

Front 9

Vitamin B3 (niacin or nicotinic acid) is part of two important molecules. What are the two important molecules?

Back 9

NAD+ (nicotinamide adenine dinucleotide)
NADP+ (nicotinamide adenine dinucleotide phosphate)

Front 10

How many electrons and protons do NADP+ and NAD+ transfer in redox?

Back 10

They transfer two electrons and one proton (i.e. a hydride ion).

So NAD+ and NADP+ become NADH and NADPH, respectively.

Front 11

Can niacin (nicotinic acid) be converted to nicotinamine?

Can nicotine (in cigarettes) be converted to nicotinamide?

Back 11

Niacin (nicotinic acid) can be converted to nicotinamide).

Nicotine cannot be converted to nicotinamide IN VIVO. It can only be converted in the presence of nitric acid.

Front 12

What is the substrate for ADP-ribosyl transferase?

Back 12

NAD+ is the substrate for ADP-ribosyl transferase. NAD+ is split into ADP-ribose and nicotinamide.
The ADP-ribose is attached to a protein.

This means protein ADP-ribosylation is dependent on Vit B3.

Front 13

What is vitamin K (naphthoquinone) a cofactor for?
What is this important for?

Back 13

Vit K is a cofactor for glutamyl carboxylase at the gamma C.

The extra negative charge created by the carboxyl is important for Ca binding. This happens in coagulation, bone homeostasis, and regulation of growth hormone.

Front 14

Once Vit K facilitates gamma carboxylation via glutamyl carboxylase, what reduces vit K back to its active form?

What is the pharmaceutical importance of this enzyme?

Back 14

Vit K epoxide reductase reduces Vit K using NADH to NAD+

This is important for pharmaceutical purposes because anticoagulants target this enzyme.

Front 15

Vitamin C (ascorbic acid) is involved in collagen synthesis via what enzyme?

Back 15

Prolyl hydroxylase.

It converts proline + alpha ketogluterate + Vit C to
hydroxyproline + succinate + dehydroascorbate

Front 16

What two vitamins are ROS scavengers?

What molecules return these vitamins to their original active state?

Back 16

Vit C and E reduce oxygen radicals (the vitamins become oxidized).

Molecules with small thiol groups such as glutathione and thioredoxin reduce the vitamins to their original (active) state.

Front 17

What is the active form of Vit B1?

Back 17

The active form of Vit B1 (thiamin) is TPP (thiamin pyrophosphate)

Front 18

What reactions do TPP catalyze?

Back 18

TPP stabilize carbanion intermediates by forming transient covalent bonds.

TPP catalyze decarboxylation of alpha keto acids.

Cofactor for pyruvate dehydrogenase (TCA cycle).
Cofactor for alpha ketogluterate dehydrogenase (TCA cycle).
Cofactor for alpha ketoacid dehydrogenase (branched chain aa metabolism)

And also a cofactor for transketolase (Pentose Phosphate shunt)

Front 19

What is the biologically active form of vit B6?

Back 19

Vit B6 (pyridoxin) has the biologically active form of P5P (pyridoxal-5-phosphate)

Front 20

What does Vit B6 (pyridoxin) stabilize the transitions state?
What is an example of an enzyme stabilized by Vit B6?

Back 20

It forms a Schiff base to stabilizes the carbanion state.

P5P is a cofactor for glycogen phosphorylase, a main enzyme for glycogenolysis.

Front 21

Know all the differences between NAD+ and FAD and their mechanisms (NAD+ accepts two electrons and one proton, while FAD accepts two electrons and two protons).

Back 21

Review from coursepack or flashcards. EXAM