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LQB381 > Amino Acids & Polypeptides > Flashcards

Amino Acids & Polypeptides Flashcards

1
Q

Amino Acids: the building blocks of proteins

A
  • proteins are polymers of amino acids

- the type and squence of amino acids dictates the structure and function of proteins

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2
Q

How many Common Amino Acids are there?

A

20

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3
Q

At a physiological pH amino acids are zwitterions meaning

A

they both contain positive and negative charges, and their net charge is zero

  • amino acid group is positive; H+ acceptor (i.e. is basic)
  • carboxyl group (COO-) is negative and is a H+ donor (i.e. acidic)
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4
Q

Amino group is an ______ of H+, and it is normally in its protonated form (NH+3). It has a ____ charge

A

acceptor, positive

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5
Q

Carboxyl group is a H+ _____ and is in the ________ (___)

A 
donor,
carboxylate form (COO-)
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6
Q

What does an Amino Acid Look like:

A
  • amino acid group (NH3+)
  • carboxyl group (COO-)
  • negative charge
  • hydrogen ion
  • variable side chain (R): unique for each amino acid
  • it varies in structure, size, and electric charge. it influence their Solubility in water
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7
Q

Chiral Molecule:

A

Alpha carbon is attached to four different groups

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8
Q

Amino Acids Mirror Images: Enanitomer

A

?

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9
Q

Polymerisation of Amino Acids:

A
  • Amino acids polymerise to form peptides & proteins via peptide bonds
  • 1 molecule of water is released during the formation of the peptide bond (condensation)
    Peptide bonds are covalent bonds that link amino acids together to form peptides, and proteins
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10
Q

Amino Acids are classified based on their chemistry of their R-group, these are:

A
  • Non-poalr/hydrophobic/aliphatic
  • Aromtaic
  • Hydrophillic polar (uncharged
  • Hydrophillic polar (charged)
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11
Q

Non-polar/hydrophobic/aliphatic Amino Acids

A
  • R-group is hydrophobic
  • the side chains tend to cluster together in centre of protein
  • stablise a protein by inducing a hydrophic effect
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12
Q

Aromatic Amino Acids:

A
  • R-Group has aromatic rings (e.g. benzene rings)
  • absorbs UV light
  • Contribute to hydrophobic effect
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13
Q

Hydrophilic polar (uncharged) Amino Acids

A
  • side chains are water soluble (causes them to be commonly exposed on protein surface)
  • can form intramolecular H bonds
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14
Q

Hydrophilic Polar (charged) Amino Acids

A
  • the most hydrophilic side chains

form ionic bonds between positive and negative ions

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15
Q

Features of Amino Acids (structure & Properties

A
  • An alpha carbon is bound to: primary amino group, caboxyl group, hydrogen, R-group
  • at physiological pH amino acids are zwitterions
  • have a chiral centre
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16
Q

Features of Amino Acid - An Alpha carbon bound to each of the following:

A
  • a primary amino group (in this case NH3+)
  • a carboxyl group (COO-) bonded on the same carbon
  • a hydrogen
  • a variable functional group (R-group) which dictates its properties inc: electric charge, size, structure, solubility
17
Q

An Alpha carbon bound to a Function Group (R-Group) in an amino acids dictates what?

A

properties such as:

  • electric charge
  • size
  • structure
  • solubility
18
Q

Features of Amino Acid - Have a Chiral Centre

A
  • C bonded to 4 different groups & therefore asymetric
  • either L-form or D-form (stereoismers)
  • mirror images of eachother (when paired referred to as enatiomers)
  • have same physical and chemical properties
  • L-Form more common
19
Q

Amino Acids are Amphoteric meaning they

A

donate and accept H+ and can act as either acid or base

20
Q

Acid Base proprties of amino acids:

A

?

21
Q

Amino Acids polymerise to form:

A

AA polymerise to form pepides/proteins

22
Q

Polymerasation of Amino Acids

A
  • peptide bonds are covalent & planar
  • Alpha amino group of one AA displaces the hydroxy group pf another AA
  • 1 x H2O molecule is released (condensation reaction)
23
Q

Ionic element to peptide bond of AA

A
  • There is an ionic element as C=O double bond transfers to be C=N double bond, leaving extra elecron from C=O to bond with oxygen = creates oxygen anion and creates a more stable C=N bond
  • decreases rotation around this bond
24
Q

How many AA’s in a peptide

A

2-50

25
Q

How many AAs in a polypeptide

A

> 50 in a single chain

26
Q

How many AAs in a protein

A

> 50 AA residues from one or more polypeptide chains, making 3d structure

27
Q

Levels of Protein Structure:

A

Primary Protein structure
Secondary Protein Structure
Tertiary Protein structure
Quaternary Protein Structure

28
Q

Primary Protein strcuture

A

Sequence of a chain of amino acids

29
Q

Secondary Protein Structure

A

local folding of the polypeptide chain into helices of sheets

30
Q

Tertiary Protein Structure

A

3D folding pattern of a protein due to side chain interactions

31
Q

Quaternary Protein Structure

A

Protein consisting of more than one amino acid chain

32
Q

Peptide and Protein Structure

A
  • to achieve its function a newly translated peptide must fold into its 3D structure
  • a peptide may also have post translational modifications added (e.g. phosphorylation)
  • a new peptide may also be cleaved by enzymes to take its functional shape
  • Composition = set of amino acids in polypeptide chain
  • Sequence = order of amino acids in the chain
33
Q

Amino Acid side chains dictate conformation of polypeptide chains - Conformation is dictated by:

A
  • Ionic bonds between basic and acidic amino acids
  • H-Bonds beween polar amino acids
  • Disulfide bonds between Cystines
  • Van der Waals forces between two hydrophobic amino acids
34
Q

Hydrophobic Amino Acids:

A
  • Glycine (Gly)
  • Methionine (Met)
  • Proline (Pro)
  • Leucine (Leu)
  • Isolecuine (Iso)
35
Q

Aromtaic Amino Acids:

A
  • Tyrosine (Tyr)
  • Tryptophan (Trp)
  • Phenylalanine (Phe)
36
Q

Hydrophillic Uncharged Amino Acids

A
  • Cysteine (Cys)
37
Q

Hydrophillic charged Amino Acids

A
  • Lysine (Lys)
  • Arginine (Arg)
  • Histidine (His)
  • Glutamic acid/glutamate (glu)
  • Aspartic Acid/Aspartate (Asp)

LQB381 (11 decks)

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