Proteins Flashcards

1
Q

What is the structure of an amino acid

A
R group
Amine Group (NH2)
Carboxyl Group (COOH)
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2
Q

How are peptide bonds formed

A

X-COOH + NH2-Y -> X-C(O)N(H)-Y + H2O

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3
Q

What is the start and end of the polypeptide

A
Start = N-Terminus
End = C-Terminus
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4
Q

What is an example of a protein with one polypeptide chain

A

Myoglobin

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5
Q

What is an example of a protein with 2 polypeptide chains

A

A and B chains of insulin

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6
Q

What is an example of a protein with 3 polypeptide chians

A

Collagen Helix of tendons and bones

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7
Q

What is an example of a protein with 4 polypeptide chains

A

the two alpha and beta subunits of haemoglobin

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8
Q

what are the 2 classes of R groups

A

Hydrophilic and Hydrophobic

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9
Q

What are the 3 divisions of the hydrophilic class of R groups

A

Acidic
Neutral
Basic

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10
Q

Which 3 groups make up the six hydrophilic side chains

A

=O

  • OH
  • NH
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11
Q

Which 1 group makes up the 2 acidic side chains

A

X-COO-

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12
Q

Which 1 group makes up the three basic side chains

A

-NH

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13
Q

What is the primary structure

A

order of the covalent polypeptide sequence

Location of Disulphide bridges, prosthetic groups, glycosylation

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14
Q

What is secondary structure

A

3-D Arrangement of ONLY the polypeptide main chain, stabilised by only hydrogen bond

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15
Q

What is the tertiary structure

A

3-D arrangement of amino acid side chains with each other and the main chain
Stabilised by hydrogen bonds, salt bridges, hydrophobic interactions, disulphide bridges

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16
Q

What is the quaternary structure

A

3-D assembly of individual protein subunits for a protein made from multiple polypeptide chains

17
Q

What are the two main types of secondary structure

A

Alpha Helix

Beta Pleated Sheet

18
Q

What is the Alpha Helix

A

The helical arrangement of a single protein maintain that repeats itself approximately every fourth residue

19
Q

What are the 6 features of the Alpha Helix

A

Rond-like with the R groups outside
All C=O and N-H maintain groups bonded by hydrogen bonds
All H-bonds are parallel to the helix
N-H forms H-bond to C=O which is 4 residues forward
3.6 residues per turn
Always right-handed for reason of the L-amino acids

20
Q

What are the 5 features of the Beta Pleated Sheet

A

Both Parallel and antiparallel sheets
All H-bonds are between separate main chains and perpendicular to the direction of the main chain
Extended main chain with the R-Groups alternating up and down
All the C=O and N-H groups are H-bonded
Beta Turns

21
Q

What is an antiparallel beta sheet

A

N-Termini are at opposite ends

22
Q

What are parallel beta sheet

A

N-Termini are at the same end

23
Q

What are the 2 features of a beta turn

A

Sharp reversal in the direction of polypeptide chain over just 4 AA residues
Sterically demanding, so a Gly residue is often located in middle of the turn

24
Q

What are the 5 features of globular proteins

A

Compact
Soluble in water
2ry structure is made of both alpha helices, beta sheets, and loop structures
4ry structure held together by non-covalent bonds
Functions in all aspects of metabolism

25
What are the 5 features of fibrous proteins
``` Extended structure Insoluble in water 2ry structure made on one type only 4ry structure held by covalent bridges Functions in structure of the body or cell ```
26
4 general examples of globular proteins
Enzymes Transport Immune Response Hormones
27
6 general examples of fibrous protein function
``` Tendons Bones Muscle Hair Ligaments Skin ```
28
Name 3 specific examples of fibrous proteins
Alpha-Keratin Elastin Collagen
29
How is Alpha-Keratin organised
the subunit contains two alpha-helices, cross-linked by disulphide bridges Assembled to form fibres
30
What 3 things is alpha keratin used for
Hair Nails Outer layer of skin
31
How is Elastin organised
Cross-linked subunits connected by covalent bonds
32
What 4 things is Elastin used for
Connective tissue Large arteries Ligaments Lung Wall
33
How is collagen organised
Triple Helix secondary structure Assembly of tropocollagen into fibres Chemical cross linkage
34
What 5 things is collagen used used
``` Connective tissue Skin Tendons Cartilage Bones ```
35
Give 3 examples of a globular protein
Haemoglobin IgG Fibrinogen