Peptides and Proteins

Question 1

Amphoteric

Answer 1

Can accept a proton ( decrease pH (acidic) so pH < pKa)

Can donate a proton (Increase pH (basic) so pH > pKa)

Question 2

Isoeletric point

Answer 2

pKa1 + pKa2
_____________ = pI
2

Question 3

pKa of Carboxilic acid group (in acidic conditions)

Answer 3

~ 2

Question 4

pKa of Amino group (in basic conditions)

Answer 4

~ 9-10

Question 5

Oligopeptide

Answer 5

2-20 amino acid residues

Question 6

Polypeptide

Answer 6

20+ amino acid residues

Question 7

Peptide bond

Answer 7

Functional group -C(O)NH - formed when an nucleophillic amino group attacks an electrophilic carbonyl through a condensation (dehydration) reaction

**Reverse = Hydrolysis rxn to break a peptide bond

Question 8

Primary structure

Answer 8

Covalent Peptides; Linear sequence of amino acids

Question 9

Secondary Structure

Answer 9

Hydrogen Bonds; local folded structures that form within a polypeptide due to interactions between atoms of the backbone (alpha helix and beta sheets)

Question 10

Tertiary Structure

Answer 10

Hydrophillic / Hydrophobic bonds; 3D structure of the polypeptide (Salt bridges and disulfide bridges)

Question 11

Quaternary Structure

Answer 11

Interactions between 2+ polypeptide chains (molecules coming together)

Question 12

Conjugated Proteins

Answer 12

Amino acids + Other molecule such as organic molecules

Ex: Lipoprotein (lipids); Glycoprotein (cabohydrates) ; Nucleoprotein (nucleic acids)

Question 13

Denaturation

Answer 13

Disruption of tertiary structures of protein (causes loss of 3D structure / shape)

Question 14

Temp. Denaturation

Answer 14

Increase the kinetic energy of molecules overcoming the hydrophobic interactions, making the protein unfold

Question 15

Solute Denaturation

Answer 15

Interfere with secondary, tertiary and quaternary structures by disrupting hydrogen bods and disulfide bridges

Question 16

Detergent Denaturation

Answer 16

Can solubilize proteins

Question 17

Amino Acid Placement in Proteins

Answer 17

Hydrophobic amino acids tend to reside inside proteins

Hydrophillic amino acids tend to reside on the outside of proteins