Chapter 8

Question 1

Know the structure of an amino acid

Answer 1

-amino group, carboxyl group, hydrogen, alpha carbon
-R groups differ in their chemical and physical properties

Question 2

Know how amino acids are classified based on the structure and atomic makeup of their R group

Answer 2

-how they interact with water (hydrophobic/hydrophilic)
-whether they are basic or acidic
-whether they are polar or nonpolar

Question 3

Compare hydrophobic and hydrophilic amino acids to one another

Answer 3

hydrophobic: located in the interior of folded proteins in order to be kept away from water
hydrophilic:
-polar side chains: hydrophilic and tend to form hydrogen bonds with one another or with water molecules
-basic and acidic amino acids are strongly polar and hydrophilic
-basic: positively charged
-acidic: negatively charged
-charged groups can form IONIC bonds with one another and with other charged molecules

Question 4

Know the three special amino acids and describe the effect these amino acids have on the proteins that incorporate them

Answer 4

GLYCINE
-R group is hydrogen (symmetric)
-Nonpolar & small… the hydrogen side chain allows for freer rotation around the C-N bond
-effect=increases flexibility of the polypeptide backbone

PROLINE
-R group is linked back to the amino group
-effect:
-restricts rotation of the C-N bond
-puts constraints on the protein folding in the proline’s vicinity

CYETEINE:
-contains a -SH (sulfhydryl) group
-2 cysteines together can form S-S disulfide bonds: bridges that can connect different parts of the same protein or different proteins

Question 5

Know the properties of peptide bond formation

Answer 5

-carboxyl group of one amino acid reacts with the amino group of another amino acid
-releases a water molecule
-the C=O group in the peptide bond is a carbonyl group & the N-H is an amide group
-the free amino group is at the amino end of the peptide & the carboxyl group is at the carboxyl end
-polymer of amino acids connected by polypeptide bonds is a polypeptide

Question 6

Know and compare the four levels of protein structure

Answer 6

1. (Primary) = sequence of amino acids
2. (Secondary) = interactions between stretches of nearby amino acids
   -alpha helix and beta sheet
3. (Tertiary)= 3D shape of a protein
   -determines the protein’s function
4. (Quaternary) = protein subunits interacting with one another
   -combination of subunits influence the function of the protein

Question 7

Describe the processes of protein denaturation and renaturation

Answer 7

-denaturation= unfolding of proteins by chemical treatment or high temperatures; lose their function
-renaturation= refolding of protein in optimal conditions; regain function

Question 8

Know the functional role of chaperone proteins in the folding of polypeptides