Chapter 3Proteins

PROTEINS

• A polymer made of the monomers called amino acids

• 20 types of amino acids

Purpose

• Mostly for structure: skin, muscle, fingernails, hair

Proteins

• -CONTAIN C, H, O, N (always)Contain: -COOH -NH2 group (amino group)-R group

What is the “R” group?

• Variable part of the amino acid

• Amino Acid Chart (handout)

Amino Acid ExamplesHow do they differ?

• alanine • glycine

Peptide Bond

• Formation of a peptide bond between two amino acids by dehydration synthesis

Peptide Bonds

• Form between Amino Acids

Protein Bonds

• peptide bond = the bond that holds amino acids together in protein molecules

• dipeptide = two connected amino acids

• polypeptide = 3 or more connected amino acids

Peptide Bonds: join amino acids

Forming/Breaking Peptide Bonds

POLYPEPTIDE (many) Bonds

Between amino acids

Types of Proteins

• 1. structural- support (collagen, keratin, elastin)-spider silk, hair, skin, fingernails

Type of Proteins

• 2. Contractile-movement=muscles, flagella

Types of Proteins

• 3. Storage proteins-such as ovalbumin (in eggs), seeds, nuts

Type of Proteins

• 4. Defensive- antibodies

Types of Proteins

• 5. Transport - include hemoglobin that carries iron (attract oxygen in red blood cells)

Types of Proteins

• 6. Signal - Hormone -chemical messengers

• (EX: insulin

• thyroxin)

0Type of Proteins

• 7. Enzymes- -speed up chemical reactions

• Lactase, • sucrase

Type of Proteins

• 8. Receptor Proteins• Intercellular communication• Bind to specific proteins

(like hormones)

• Receptor Proteins

Levels of Protein Structure

• Primary structure

• is its unique sequence of amino acids

• determined by inherited genetic info

•

Levels of Protein Structure

• Secondary Structure

• most protein have segments repeatedly coiled or pleated in patterns

• result of H-bonds

Note the H-bonds (between -O of carbonyl and -H of amino):

coiling and pleating

Protein Structure

• Tertiary Structure• a. folding on itself

• b. hydrophobic

• a type of weak bond (disulfide, H-bonds, and ionic bonds)

• Cross-links between R-groups

Tertiary Folding: disulfide bridges

• Disulfide bridges formed between cysteine amino acids

• (Look at cysteine’s structure)

Disulfide Bridges

• Formed when cysteine’s sulfur join• You Tube Videos Disulfide Bonds

Use the Amino Acid Reference Sheet

• Select the type of tertiary interaction as• (1) disulfide (2) ionic• (3) H bonds (4) hydrophobic

• A. Leucine and valine• B. Two cysteines• C. Aspartic acid and lysine• D. Serine and threonine

ANSWERS

• Select the type of tertiary interaction as• (1) disulfide (2) ionic• (3) H bonds (4) hydrophobic

• A. 4 Leucine and valine• B. 1 Two cysteines• C. 2 Aspartic acid and lysine• D. 3 Serine and threonine

Protein Structure

• Quaternary Structure

• two or more subunits joined into one functional macromolecule

Two Basic Shapes

• Fibrous• Strands• Like

hair, nails,skin, muscle fibers

• Globular• Blobs• Like

hemoglobin, insulin, hormones, antibodies

Quaternary: combination of other shapes

collagen

• Identify the level of protein structure• 1. Primary 2. Secondary• 3. Tertiary 4. Quaternary

• A. Beta pleated sheet• B. Order of amino acids in a protein• C. A protein with two or more peptide

chains• D. The shape of a globular protein• E. Disulfide bonds between R groups

• Identify the level of protein structure• 1. Primary 2. Secondary• 3. Tertiary 4. Quaternary• ANSWERS• 2 Beta pleated sheet• 1 Order of amino acids in a protein• 4 A protein with two or more peptide• chains• 3 The shape of a globular protein• 3 Disulfide bonds between R groups

Video Stuff

• Protein Denaturation Video (McGraw-Hill)

• Interactive Animations: Protein Folding

• Protein Structures Animation

• No Sound,but great molecular models

Denaturation• Disruption of secondary, tertiary and

quaternary protein structure by:• heat/organics (Break apart H bonds and

disrupt hydrophobic attractions) • acids/ bases (Break H bonds between

polar R groups and ionic bonds)• heavy metal ions (React with S-S bonds to

form solids)• agitation (Stretches chains until

bonds break)

NOTE:

• Denaturation does not break the primary structure

• Denaturation of an egg with a strong acid video

Protein Extra Credit OPP

• Can bring in up to 5 labels (no repeats) for 1 point each with a protein term circled:– protein– peptide– amino

• Proteins are Active

• DO PROTEIN ACTIVITY