Proteins

Question 1

proteins

Answer 1

• polymers composed of AA

- provide structure, regulate metabolism, hormone control, catalyst

Question 2

amino acids

Answer 2

-amine group and carboxyl group attached to am alpha carbon (w an R group)

Question 3

Fischer projection of an AA

Answer 3

drawn with the amino group on the left (L-enantiomer)

Question 4

zwitterions

Answer 4

-AA in the form of a neutral ion, having both positive and negative charges

Question 5

amphoteric

Answer 5

-AA act as either bases or acids depending on the environment

Question 6

isoelectric point (pI)

Answer 6

-intermediate pH at which the AA is electrically neutral

Question 7

titration of AA

Answer 7

1. when adding base, the carbonyl group loses its proton first, then the amino group loses its acidic proton
2. 2 moles of base must be added to deprotonate one mol of AA
3. buffering capacity is greatest at the 2 dissociation constants (Ka1 and Ka2)

Question 8

Henderson-Hasselbalch equation

Answer 8

pH=pKa+log([CB]/[CA])

Question 9

non polar AA

Answer 9

• R-groups are saturated hydrocarbons

- hydrophobic

Question 10

polar AA

Answer 10

• R-groups are polar, uncharged

- hydrophilic

Question 11

acidic AA

Answer 11

• R-group contains a carboxyl group

- negative charge

Question 12

basic AA

Answer 12

• R-group contains an amino group

- positive charge

Question 13

peptides

Answer 13

-composed of AA subunits (residues) linked by peptide bonds

Question 14

reactions of peptides

Answer 14

-peptide bonds b/w carboxyl group and amino group is formed via condensation reaction (water is lost)

Question 15

trypsin

Answer 15

protein that cleaves at the carboxyl end of arginine and lysine

Question 16

amino-terminal (N-terminal)

Answer 16

terminal AA with a free alpha-amino group, on left

Question 17

carboxyl-terminal (C-terminal)

Answer 17

terminal with a free carboxyl group, on right

Question 18

primary structure of proteins

Answer 18

-sequence of AA

determined using a lab procedure called sequencing

Question 19

secondary structure

Answer 19

• local structure of the neighboring AA, governed by H bond interactions
• alpha helix and beta sheet

Question 20

alpha helix

Answer 20

-rod-like structure in which the peptide. chain coils clockwise, H bonds b/w carboxyl O atoms and amine H atoms 4 residues away

Question 21

beta pleated sheet

Answer 21

• peptide chains lie along each other in rows; rippled

- H bonds b/w carbonyl O atoms and amine H atoms

Question 22

tertiary structure

Answer 22

-3D shape of the protein

Question 23

disulfide bond

Answer 23

2 cysteine molecules become oxidized to form cystine, create loops in tertiary structure

Question 24

fibrous proteins

Answer 24

• sheets or long strands

- collagen

Question 25

globular protein

Answer 25

• spherical in shape

- myoglobin

Question 26

quaternary structure

Answer 26

• ways in which more than one polypeptide subunit arranges

- ex: Hb

Question 27

conjugated proteins

Answer 27

-derive part of their function from covalently attached molecules called prosthetic groups (at least one portion is not made of protein)

Question 28

lipoproteins, glycoproteins, and nucleoproteins

Answer 28

proteins with lipid, carbohydrate, and nucleic acid prosthetic groups

Question 29

denaturation (melting)

Answer 29

-process in which proteins lose their 3D shape and revert to random-coil state

Question 30

renature

Answer 30

-regain structure and function if the reagent is removed