VITAMIN B3 and VITAMIN B2

Vitamin B3: Nicotinic acid and Vitamin B3- the nicotinamide coenzymes : NAD+ and NADP+ III.. Vitamin B2: Riboflavin and the Flavin Coenzymes FAD, FMN IV.. Differences between NAD/NADH

VITA MIN

B3 a nd V

ITAM IN B

2

Ha Thi Thuy Hoa K15 Honor Program

of Biology

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add pi cture

I Introduction

II Vitamin B3: Nicotinic acid and Vitamin B3-

the nicotinamide coenzymes : NAD+ and

NADP+

III Vitamin B2: Riboflavin and the Flavin Coenzymes FAD, FMN

IV Summary and Question

I INTRODUCTION

What is the most important function of Vitamin B ?

Why do we need vitamin B everyday?

 Play important roles

in cell metabolism.

carrying hydrogens and

metabolic reactions

II.Nictotinic acid

Nicotinamide adenine dinucleotide (phosphate)

Reaction of NAD

Differences between NAD/NADH and NADP/NADPH

 In many cells and tissues, the ratio NAD/NADH is high ,

therefore favoring hydride transfer from a substrate to NAD to form NADH.

->Role: NAD generally functions in oxidations – a part of

catabolic reaction.(oxidation such as pyruvate in the

mitochondrial matrix)

 By contrast, NADPH is generally at a higher concetration than NADP, favoring hydride transfer from NADPH to substrate.

->Role: NADPH is the usual coenzyme in reduction – as part of

an anabolic reaction (synthesis fatty acid in the cytosol)

Deficiency : Pellagra disease

Flavin adenine dinucleotide (FAD) Flavin

mononucleotide (FMN)

 Flavoprotein are enzymes that catalyze

oxidation-reduction reactions using either FMN or FAD as

coenzymes

 FMN and FAD bind tightly to proteins such as

succinate dehydrogenase(in Krebs cycle) They do not transfer electrons by diffusing from one enzymes

to another

 Under the reversible reduction, accepting either one

or two electrons in the form of one or two hydrogen atoms from a reduced substrate

 The fully reduced form : FADH2 and FMNH2

Reaction of Riboflavin

Function of flavoproteins

 Electrons carriers in oxidative phosphorylation (in

mitochondria)

 Serve as light receptors in cryptochromes in chloroplast in plant.

DIET OF VITAMIN B3

DIET OF VITAMIN B2

IV QUESTIONS AND CONCLUSION

1 How many electrons NAD and FAD can carry?

Answer: NADH can transfer 2 electrons and 1 proton while FAD can accept or donate electrons 1 or 2 at a time and also 1 or 2 protons.

 2 What is flavoprotein?

Answer: Flavoprotein are enzymes that catalyze

oxidation-reduction reactions using either FMN or FAD

as coenzymes FMN and FAD bind tightly to proteins.

 Text books: 1 Hoa Sinh hoc, Pham Thi Tran Chau, Tran Thi Ang 2 Principle of Biochemistry, Lehninger.

 http://en.wikipedia.org/wiki/NADH_dehydrogenase

 http://www.princeton.edu/~

achaney/tmve/wiki100k/docs/NADH_dehydrogenase.ht ml

 http://en.wikipedia.org/wiki/NADPH_oxidase

 http://

en.wikipedia.org/wiki/Nicotinamide_adenine_dinucleoti de

 http://en.wikipedia.org/wiki/Flavin_adenine_dinucleotid e

THANKS FOR YOUR ATTENTION

Figure 7.4 Coenzyme Action

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