Protein Part 1-Biochemistry-Lecture Slides, Slides of Biochemistry

Download Protein Part 1-Biochemistry-Lecture Slides and more Slides Biochemistry in PDF only on Docsity!

PROTEINS^ Protein^ Biochemistry

What are proteins?Proteins are macromoleculescomposed of amino acids linkedtogether through peptide bonds.

What do proteins do?

proteins

Movement^ Transport

Signaling

off on Regulation Immune

A B Catalysis

Section

Chemical

Components

of

Proteins

• • The average nitrogen content inproteins is about 16%, andproteins are the major source of Nin biological systems. • The protein quantity can beestimated.protein in 100g sample = N per gram x 6.25 x

§1.1 Amino Acids • The basic building blocks of proteins • About 300 types of AAs in nature, butonly 20 types are used for proteinsynthesis in biological systems. • A amino group, a carboxyl group, a Hatom and a R group are connected toa C atom. • The C atom is an optically activecenter.

Molecular weight Dalton:A unit of mass nearly equal to thatof a hydrogen atomGly

C^ NO^2

H^25

75

Ala^ C

NOH^327

89

Val^ C

NOH^5211

117

Leu^ C

NOH^6213

131

Ile^ C

NOH^6213

131

§1.1.a Classification^ •^ The R groups, also called side chains,make each AA unique and distinctive.^ •^ R groups are different in their size,charge, hydrogen bonding capabilityand chemical reactivity.^ •^ Aas are grouped as (1) non-polar,hydrophobic; (2) polar, neutral; (3)basic; and (4) acidic.

Polar and uncharged AAs • R groups are polar: -OH, -SH, and-NH^.^2 • R groups are highly reactive. • AAs are soluble in H

O, that is, 2

hydrophilic.

-^ R groups have one -NH

-^ R groups are positively charged atneutral pH (=7.0). •^ AAs are highly hydrophilic.

Basic AAs

Aspartic^ acid

glutamic^ acid

(Asp^ or^ D)^

(Glu^ or^ E)

Nomenclature

Starting from the carboxyl group, andnaming the rest carbon atomssequentially in Greek letters. ‐amino‐propionic

acid^

‐amino‐

‐guanidinovaleric

acid

(alanine)^

(arginine)

• CH COOCH 2 + NH 3 CH^ CHNH^22 NH NH C 2

CH^3 NH -CH^ COO+^3 ^

 