Macromolecules – Day 1

PROTEINS

BACKGROUND

• “molecule of action”

• Cause most things in your body to happen – to do work

• Sources of protein:

• Location of protein within your body: muscles, hair, fingernails, in cells as enzymes

EWW!

STRUCTURE OF PROTEIN

• All proteins have the same basic structure:– They are unbranched polymers of amino acids

(a.a.)

Polymer: long chain of connected units – each unit is a monomer

• In proteins specifically, the “chain” is a polypeptide and each “link” is an amino acid

• The linkage that forms between a.a. units is called a peptide bond

Amino Acids (a.a.)

• There are 20 different a.a.• 8 of the 20 a.a. are essential a.a. which the

human body cannot produce so these a.a. must be obtained from food

• All a.a. have the same basic structure:– They are small molecules with a central carbon atom

attached to:• An amino group• A carboxyl group• A hydrogen atom• *A side chain (R)* - the structure of the R makes each

a.a. different

Diagram of Amino Acid Structure

Structure of Protein Con’t

• Proteins can have one hundred to thousands of a.a. in their chain

• a.a.’s may appear in a protein many times

• The order of the a.a.’s determines the shape of the protein

• The shape of the protein determines its job

Diagram of a Protein (polypeptide):

LEUCINE SERINE

LYSINE

CYSTEINE

Amino Acid (monomer)

Peptide Bond

ENZYMES

• Type of protein that speeds up chemical reactions

• Needed to speed up almost every reaction that occurs in living organisms

• Reusable• The active site is the location where the

chemical reactions take place– E.g. salivary amylase – breaks down sugars

in your mouth

HORMONES

• Type of protein that acts as a chemical messenger

• E.g. insulin – regulates blood sugar levels

• E.g. Human growth hormone (HGH)

DENATURATION OF PROTEINS

• Changing the shape of the protein caused by changes in the environment may/does stop the protein from doing its job

• Protein’s functions usually return when environmental factor is removed, as long as the peptide bonds between a.a. have not been broken

Denaturation Con’t

• Denaturation of proteins (including enzymes) can be caused by exposure to:– Extremely high temperatures (above 40oC)– Acids/bases (pH)– Salty environments– High sugar

Application of Denaturing Proteins

• Fever above 39oC is dangerous since it may denature critical brain enzymes, leading to seizures and possibly death

• Straightening/curling hair with treatments denatures proteins in hair causing hair to straighten or curl

Application of Denaturing Con’t

• Curing meats or vegetables in vinegar – preserves food by denaturing enzymes in bacteria that cause food to spoil– Fruit and vegetables turn brown when

exposed to air due to enzyme reactions: blanching fruit and veg (dipping quickly in boiling water) denatures enzymes that cause them to turn brown (or could squeeze lemon juice = acidic)