Chapter 4

Question 1

how are amino acids linked?

Answer 1

linked by amide bond formed between carboxyl group of one amino acid and and the amino group of the next

Question 2

what are the characteristics of peptide bonds?

Answer 2

resistant to hydrolysis so proteins are really stable

peptide bond is both hydrogen donor/acceptor

Question 3

What is an alpha helice?

Answer 3

helix: rod…within the rod the CO group of each amino acid is hydrogen bonded to the NH group of the amino acid

Question 4

what is beta strand made up of?

Answer 4

polypeptide chain nearly extended
strands are connected by NH to CO hydrogen bonds
can be parallel or mixed

Question 5

how can you account for the stability of the peptide bond when hydrolysis releases considerable amount of energy?

Answer 5

energy barrier must be crossed to go from polymerican state to hydrolized state

Question 6

why is rotation about peptide bond protonated? what are consequences of lack of rotation

Answer 6

peptide bond has partial double bond character which prevents rotation
lack of rotation constrains conformation of peptide backbone and limits possible structure

Question 7

what is a polypeptide backbone?

Answer 7

the nitrogen, alpha carbon, carbonyl carbon repeating unit

Question 8

what is the difference between the amino acid composition and the amino acid sequence

Answer 8

composition: refers to amino acids that make up protein
sequence: indentifies a unique protein

Question 9

what is the difference between an alpha helix and a beta strand?

Answer 9

helix: condensed, coiled structure
strand: fully extended polypeptide chain

**both structures stabilitzed by hydrogen bonds between polypeptide backbone

Question 10

list all of structures and how they are bonded

Answer 10

primary: peptide bond
secondary: local hydrogen bonds between componentsof polypeptide backbone
tertiary: “global” various types of non-covalent bonds between “r” groups that are far apart in primary structure
quaternary: vaious non covalent bonds between R groups on surface of subunits

Question 11

How would the following treatments contribute to protein denaturing?
( heat, hydrophobic detergents, large changes in pH)

Answer 11

Heat: increase thermal energy of chain
hydrophobic detergents: denature the protein by turning it inside out
large changes in pH: ionic interaction including hydrogen bonds would be disrupteddd