7.4/14.1 PROTEINS

Protein’s have 4 levels of Structure:

1. Primary Structure = the order of amino acids that make up the polypeptide; amino acids are bonded together with peptide bonds

What determines the order of amino acids?

2. Secondary Structure – the repeated, regular structures that polypeptide chains make due to hydrogen bonding; usually twisted alpha helices or beta-pleated sheets

Alpha helix Beta pleated sheet

3. Tertiary Structure – 3D shape due to the bending and folding of the polypeptide; folds are the result of interactions between the R groups of amino acids

bonds include covalent bonds (disulfide bonds between sulfurs), hydrogen bonds, ionic bonds

** folding occurs after translation

4. Quaternary Structure – when 2 or more polypeptide chains come together to make a protein; other elements may also be involved

Prosthetic group

http://www.umass.edu/molvis/tutorials/hemoglobin/heme.htm

Fibrous vs. Globular Proteins

• Fibrous Proteins – long, narrow, and often insoluble in water – Ex: keratin – skin and hair– Ex: collagen – connective tissue– Ex: actin - muscles

Fibrous vs. Globular Proteins

• Globular Proteins – 3 dimensional and often water soluble– Ex: hemoglobin– Ex: insulin– Ex: enzymes– Ex: antibodies

Significance of Amino Acid Polarity

Non-Polar Amino Acids make up proteins that are typically hydrophobic and therefore found at inner parts of cell membrane, water insoluble

Polar Amino Acids make up proteins that are typically hydrophilic and therefore found protruding through cell membrane; water soluble

Enzyme-substrate specificity is also determined by polarity

Review Question!!!

What are the 6 functions of membrane-bound

proteins?

The 6 Functions Are…1. Channel for passive transport

2. Pump for active transport3. Hormone binding site

4. Enzyme5. Cell to cell communication

6. Attachment

Four Functions of Proteins:

1. Structure – collagen2. Movement – myosin and actin in muscles3. Gas transport – hemoglobin4. Defense – antibodies5. Enzyme – amylase6. Hormone - insulin Pick 4 to know!