Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PCAT: BIOLOGY > proteins > Flashcards

proteins Flashcards

1
Q

structure of amino acid

A

carboxyl, carbon then amine

  • all amino acids except glycine are chiral therefore optically active
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

almost all amino acids are __ enantioners

A

L

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

fisher projection for aino acids

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

acid base characteristics of amino acids

A
  • have acidic and basic functionality, amphoteric (act as acid or base depending on env)
  • have 2 protons that can dissociate, 2 Ka/Kb values
  • in sol can be zwitterionic (pos pos an neg charge)

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the isoelectic point

A
  • pH lies between pKa1 and pKa2
  • aa is neutral and exists as a zwitterion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

explain the titration of amino acids

A
  • amino acid acts as a buffer so pH changes slowly upon addition of base
  • @pKa1 +NH3CH2COOH = +NH3CH2COO-
  • when more base added all COOH deprot, mol is now electrically neutral (zwitterion) and pH =pI
  • pKa2 reached when past pI
  • after pKa2 mol mostly NH2CH2COO-
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

___ moles of base are requires to deprotonate 1 mole of mot amino acids

A

2 mol

one for COOH and one for NH3+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

where is the buffering capacity of amino acids greatest?

A

near Ka1 and Ka2

  • at isoelectric point bufferin capacity is minimal
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

how to determine how much prot and deprot aa you have

A

pH = pKa + log (depot/prot)

ex: 3.3 = 2.3 + log (deprot/prot)

1 = log(deprot/prot)

10 = deprot/prot

*10x as many zwitterions as fully protonated form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

non polar amino acids

A

alanine, valine, leucine, isoleucine, proline, phenylalanine, glycine and tryptophan

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

polar amino acids

A

methionine, serine, threonine, cysteine, tyrosine, asparagine, glutamine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

acidic amino acids

A
  • aspartic acid, glutamic acid, aspartate, glutamate
  • carry net eng charge at physiological pH
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

basic amino acids

A
  • carry net pos charge at physiological pH
  • arginine, lysine and histidine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

study amino acid structures

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are pepties

A

composed of amino acid subunits

  • also called residues
  • linked by peptide bonds

2 aa = dipeptide, 3= tripeptide, and many = polypeptide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

peptide reactions

A
  • aa joined by peptide (amide) bonds formed via condensation rxn
  • can hydrolyse by adding water w/ acid or base
17
Q

what does trypsin so to peptide linkages? what about chymotrypsin

A
  • certain enzymes digest chain at specific linkage
  • trypsin cleaves at COOH end of arg and lys
  • chymotrypsin cleaves COOH end oh phenylalanine, tyrosine and tryptophan
18
Q

peptide properties

A
  • terminal amino acid w/ a free alpha amino group = amino terminal (N terminal)
  • other is carboxy (C-terminal)
  • have 2 res structues so rotation along C-N bond is resticted
19
Q

what are proteins

A
  • polypeptides that can range from only a few -> thousands of aa
  • are enzymes, hormones, memrbane pores, receptors, elements of ell structure
  • have primary, secondary, tertiary and quat structures
20
Q

describe the primary structure of an amino acid

A
  • seq of amino acids listen from N term -> C term
  • other levels depend on this sequence
  • can determine primary strucute in lab vai sequencing
21
Q

what is secondary structure

A
  • local structure of neighbouring amino acids governed mianly by H bond interactions within and between peptide chains
  • A helix and B pleated sheet
  • most complex prot contain both
22
Q

describe the alpha helix

A
  • rod-like structure in whih peptide chain coils clockwise about central axis
  • helix is stab by intramol h bonding between carbonyl oxygen atoms and amine hydrogen atoms 4 residues away

-

23
Q

describe the beta pleated sheet

A
  • peptide chains lie alongside eachother in rows
  • intra mol h bondinh between carbonyl oxygen atoms on one chian and amine on another
  • r groups point above and below
24
Q

describe tertiary structure

A
  • 3D shapre of the protein determined by hydrophilic and hydrophobic interactions between R groupds and distribution of disulfide bonds
  • aa with hydrophobic R groups tend to be found closer together, and face inwards
  • hydrophilic aa arrange themselves with T groups interacting with aqueous env
25
Q

what is the effect of 2 cysteine mol

A
  • can form a disulfide bond, created loop in tertiary structure
26
Q

what happens when proline is present in chain

A
  • cannot fit into alpha helix, will cause a kink in the chain
27
Q

what are the 2 major classifications of proteins based on tertiary structure

A
  • fibrous (ex collagen) found in long sheets or strands
  • globular (ex myoglobin) spherical in shape
28
Q

what is quaternary structure

A
  • some proteins contain more than one polypeptide unit
  • quat structure refers to the way in which these subunits arrange themselves to yield a functional protien molecule
    ex: hemoglobin is composed of 4 polypeptide chains
29
Q

what are conjugated proteins

A
  • derive part of function from ovaletly attached molecules called prosthetic groups

*at least one portion of thier structure is not made of protein (could be orgnic mol or metal ions)

  • many vit are prosthetic groups
  • playmajor role in determining the function of proteins
    ex: the heme group in myo and hemoglobin
30
Q

what are proteins that have lipid, carbohydrate and nuceltic acid prosthetic groups refered to as

A

lipoproteins, glycoproteins and nucleoproteins respectively

31
Q

what are albumins and globulines

A
  • primry globular in nature and function as carriers or enzymes
32
Q

what are scleroproteins

A
  • fibrous proteins that act as structural proteins
33
Q

whar are chromoproteins

A

proteins bound to pigmented molecules

34
Q

what are metalloproteins

A

proteins complexed around a metal ion

35
Q

explain denaturing proteins

A
  • also called melting
  • protein loses 3 structure and revert to a random coil state
  • caused by detergent or changes in pH, temp or solute cnoc
  • weak intermolecular forced keeping the proteins table and functional are disrupted
  • damage usually permanent

*some gentle denaturing agents do not permanently disrupt the protein and remocal may allow protein to renature and therefore regain function

PCAT: BIOLOGY (18 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions