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Biochemistry > Chapter 2 : Proteins > Flashcards

Chapter 2 : Proteins Flashcards

1
Q

What are proteins

A

A molecule composed of amino acids joined together by peptide bonds

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2
Q

How many amino acids are there in total

A

20

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3
Q

What is the basic monomer of proteins

A

amino acids

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4
Q

What are the three major groups of an amino acid ?

A

amino group (NH2) , carboxyl group ( COOH) and the side chain

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5
Q

What group gives the identity of the amino acid

A

the side chain

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6
Q

What kind of shape do amino acids have ?

A

tetrahedral shape

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7
Q

True or false , the central carbon on an amino acid is not chiral

A

False , the central carbon is chiral

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8
Q

What are the two enantiomers of all amino acids ?

A

L and D

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9
Q

Between the L and the D isomer, which one is mostly found in proteins

A

The L isomer

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10
Q

How many different types of amino acids are there?

A

5

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11
Q

Non-polar Aliphatic Amino acids

A
  • Nonpolar
  • Water insoluble ( CH bonds)
  • 7 amino acids
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12
Q

Aromatic Amino Acids

A
  • Contain an aromatic group
  • nonpolar
  • Able to absorb UV light
  • 2 amino acids
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13
Q

Polar Uncharged Amino Acids

A
  • Contain polar bonds ( OH, SH, or NH)
  • contain no charges
  • more soluble in water
  • 6 amino acids
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14
Q

Acidic Amino Acids

A
  • side chain is a COOH group
  • weak acids but exist as COO- at neutral pH
  • 2 amino acids
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15
Q

Basic Amino Acids

A
  • Contain net positive charges at neutral pH
  • contain amine group as side chain which is protonated
  • 3 amino acids
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16
Q

How many dissociable hydrogens does every amino acid have AT LEAST ?

A

2 hydrogens

17
Q

pK1

A

1/2 of the amino acid molecules have lost H from the COOH

- falls between pH of 2.0-2.4

18
Q

pK2

A

1/2 of amino acid molecules have lost H+ from NH3 group

- falls between pH of 9.0-9.8

19
Q

Where do peptide bonds form?

A

Between the carboxyl group of the 1st aa and the amine group of the 2nd amine

20
Q

What is a biproduct of a peptide bond

A

water, dehydration synthesis

21
Q

True or False, the peptide bond is a single bond which has resonance form in a double bond

A

True, the double bond inhibits rotation creating stability and polarity in the protein backbone

22
Q

How many levels of protein structure are there ?

A

4

23
Q

Primary structure

A

sequence of amino acids

24
Q

Secondary structure

A

hydrogen bonding between adjacent amino acids to create α-helix or β-pleated sheet

25
Q

Teritary structure

A

complete 3D shape of the polypeptide chain

26
Q

Quarternary structure

A

structure that results after two or more interacting polypeptide chains come together

27
Q

True or false, the primary structure contains all the info for the final 3D shape

A

True

28
Q

True or false, the backbone of the protein is 3D

A

False, the backbone of a protein is planar

29
Q

α-Helix

A
  • found in secondary structure
  • All H bonds are parallel to the axis
  • helices can be right or left handed
30
Q

β –pleated sheet

A
  • formed from the protein backbone
  • can either be parallel or antiparallel
  • side chains extend out perpendicularly
31
Q

β-turn

A

When the β-sheet is formed , the turn allows fo the backbone to bend, turn or reorient

32
Q

Hydrophobic protein interactions

A

Nonpolar side chains cluster to avoid interaction resulting in protein folding

33
Q

Ionic protein interactions

A

Attractions or repulsions between opposite or like charges on the side chains

34
Q

Van Der Waal protein interactions

A
  • quick dipole-dipole reactions resulting in fluctuations in electron distribution
35
Q

Denaturation

A

the process which protein function begins to degrade due to the surrouding eniorment

Biochemistry (8 decks)

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