Introduction

Lipids, Proteins, and Carbohydrates

Biochemistry

Biochem is the study of biological materials Compounds of biological origin Chemistry of biological processes

Biological materials are primarily made up of: Lipids Proteins Carbohydrates

Lipids

Fat-like compounds that leave grease mark Insoluble in water but soluble in organic

solvents Fats are esters, reacting alcohol & organic

acid produces ester Alcohol in fats is always glycerol, The organic acid obtained from fats is called

fatty acid

Fatty Acids

Mono-carboxylic acids, -COOH Contain even number of H Have long & straight Carbon chain (20) Have 4 or less double bonds

R1-COO-R1’ l

R2-COO-R2’ A generic formula for a triglyceride l

R3-COO-R3’

Oils

Veg oils are liquid at room temp. (low melt point) VOs are less saturated than animal fats Less saturated oils has greater number of C=C Hydrogenation is adding H to C=C bonds to

make the oil saturated (solid) Degree of unsaturation is normally measured by

the Iodine number. It is grams of Iodine that is decolorized by 100 grams of fat.

Hydrolyzing Fats

Hydrolyzing fats with inorganic bases is called saponification (yields glycerol & soap)

Sodium hydroxide makes hard soap and potassium hydroxide or ammonium hydroxide make soft soap.

Fats become rancid when exposed to moist air, microorganisms act as catalysts to hyrolyze the fat

Oxygen and ozone in the air oxidize the C=C bonds, producing aldehydes, acids, and peroxides that are the cause of rancid odor.

Waxes

Waxes that cover the fur and feather, and top of the shiny plant-leaf and beeswax are compound lipids that are also esters.

Waxes like paraffin are pure hydrocarbons and NOT fats or esters.

Proteins

Introduction

Proteins make up our muscles, skin, and the biological catalysts called enzymes

Proteins do not accumulate in the body. Excess proteins breaks down in the body and

get excreted in the H2N-C-NH2

form of urea: ll

O We can manufacture protein through various

bacteria

Protein Structure

Proteins are polymers They are formed like strings of beads Small units of protein chains is called amino

acids About 20 amino acids make up all known

proteins The amino acids have both amine group and

the acid group attached to the same carbon atom (alpha amino acids)

Alpha amino acid structure

Chemical Structure of a common amino acid: H

l

H2N-C-COOH

ll R1

R1 is the organic “tail” of the amino acid

List of Amino Acids

AMINO ACID

THREE LETTER CODE

SINGLE LETTER CODE

glycine Gly G

alanine Ala A

valine Val V

leucine Leu L

isoleucine Ile I

methionine Met M

phenylalanine

Phe F

tryptophan Trp W

proline Pro P

lysine Lys K

arginine Arg R

histidine His H

AMINO ACIDTHREE

LETTER CODESINGLE

LETTER CODE

serine Ser S

threonine Thr T

cysteine Cys C

tyrosine Tyr Y

asparagine Asn N

glutamine Gln Q

aspartic acid Asp D

glutamic acid Glu E

Protein Polymers Forming a protein’s polymer chain involves a

condensation reaction between an acid group (-COOH) and an amine group (-NH2), with water as a product.

Structure of a 4 unit amino acid:

Polypeptide Chains

In a protein the polypeptide chain is the backbone of the molecule, holding it together by the covalent bonds (primary bonds)

Known protein polymers contain from a few dozen to half-a-million amino acid units

Proteins have a string-like secondary structure Alpha helix structure -- Coiled peptide Beta configuration ---- parallel strands Combined structures-- coiled, parallel, and tangled

sections

Hydrogen Bonds

Hydrogen bond form between O and N atoms Alpha helix configuration is held in shape by

H bonds between the C=O group on one loop and the N-H group across the way.

H bonds are fairly weak. Any external force that breaks these bonds simultaneously destroys the secondary structure, causing the protein to denature

For example heating and change in pH destroys H bond

Changing Proteins thru Other Bonds

Adding a substance that forms a stronger bond than H, it changes the shape of the protein.

For example Lead and Mercury in human body denatures many of the essential proteins in the body

Whole protein molecules cluster in a characteristic shape or structure. For example, tobacco mosaic virus molecules form a hollow tube

Proteins are somewhat water soluble and can be classified as precipitating colloids