PROTEINSSBI4U

Ms. Manning

Most diverse molecules in living organisms.

Coded for by genes in the DNA Used as:

Structural building blocksCatalysis - enzymes ImmunityTransport of other molecules across the cell

membrane Monomer:

Amino acid

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FOUR OF THE 7 CLASSES OF PROTEINS

Structural

Contractile

Storage

Transport

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20 AMINO ACID MONOMERS

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STRUCTURE OF AMINO ACIDS

Amino group –NH2

Carboxyl group -COOH

Hydrogen -H

Side group -R

Amino

group

Carboxylgroup

R group

Side groups

Leucine -hydrophobic

Serine-hydrophillic

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Amino acids have a central carbon with 4 things bonded to it:

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LINKING AMINO ACIDSCells link amino acids together to make proteins

The process is called condensation or dehydrationPeptide bonds form to hold the amino acids together

Carboxyl

Amino Side

Group

Dehydration Synthesis

Peptide Bond

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PROTEIN STRUCTURE

1 A.A. = 1 A.A. monomer 2 A.A.’s = a dipeptide molecule Many A.A.’s = a polypeptide chain 1 or more polypeptide chains = a protein

molecule.

There are 4 levels of protein structure: 1. Primary Structure 2. Secondary Structure 3. Tertiary Structure 4. Quaternary Structure

http://www.youtube.com/watch?v=lijQ3a8yUYQ&feature=related

LEVELS OF STRUCTURE Primary A polypeptide chain

of A.A’s.

SECONDARY STRUCTURE

A.A. chain will pleat or coil or form a helix.

H bonds!

SECONDARY STRUCTURE Alpha helix Flexibility Polypeptide chain

tightly coiled held by H bonds

i.e. Keratin

http://www.youtube.com/watch?v=eUS6CEn4GSA&feature=related

SECONDARY STRUCTURE Beta pleated sheet Strength Parallel polypeptide

chains H-bonds i.e. silk proteins

http://www.youtube.com/watch?v=wM2LWCTWlrE&feature=related

TERTIARY STRUCTURE

Folded to form a specific shape (enzymes)

3. TERTIARY – 3D folding (more complex) of polypeptide held in place by:

Hydrophobic bonding of non-polar side chains

Ionic bonds between charged side chains

Covalent disulfide bridges of cysteines

FIBROUS VS. GLOBULAR Fibrous proteins are

strong and insoluble in water

eg. collagen, silk, keratin (main component in hair)

Globular proteins are spherical in shape,

Have a hydrophobic group on the inside, hydrophilic group on the outside.

Soluble in water. eg. enzymes, antibodies,

hormones

Protein consists of one or more polypeptides twisted and coiled into a specific shape Shape is determined by the ORDER of amino

acids

Many proteins are globular (rounded shape), especially enzymes.

4. QUARTERNARY – Two or more polypeptides wound together

HEMOGLOBIN

C3032H4816O872N780S8Fe4

Build it!!!

PROTEIN SHAPE ALSO INFLUENCED BY... Chemical and physical environmental factors

i.e. pH and temperature changes in environmental conditions may

cause changes in protein shape – called denaturation, protein becomes non-functional

Protein can resume shape under normal conditions if primary structure is maintained.

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DENATURATING PROTEINSChanges in temperature & pH can denature (unfold) a protein so it

no longer worksCooking denatures protein in eggs

Milk protein separates into curds & whey when it denatures

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CHANGING AMINO ACID SEQUENCESubstitution of one amino acid for

another in hemoglobin causes sickle-cell disease

(a) Normal red blood cell Normal hemoglobin

12 3

4 56

7. . . 146

(b) Sickled red blood cell Sickle-cell hemoglobin

2 314 5

67. . . 146

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OTHER IMPORTANT PROTEINS

• Blood sugar level is controlled by a protein called insulin

• Insulin causes the liver to uptake and store excess sugar as Glycogen

• The cell membrane also contains proteins

• Receptor proteins help cells recognize other cells

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INSULIN

Cell membrane with proteins & phospholipids

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