Proteins Flashcards

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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
Q

What are the 5 features of fibrous proteins

A
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
Q

4 general examples of globular proteins

A

Enzymes
Transport
Immune Response
Hormones

27
Q

6 general examples of fibrous protein function

A
Tendons
Bones
Muscle
Hair
Ligaments
Skin
28
Q

Name 3 specific examples of fibrous proteins

A

Alpha-Keratin
Elastin
Collagen

29
Q

How is Alpha-Keratin organised

A

the subunit contains two alpha-helices, cross-linked by disulphide bridges
Assembled to form fibres

30
Q

What 3 things is alpha keratin used for

A

Hair
Nails
Outer layer of skin

31
Q

How is Elastin organised

A

Cross-linked subunits connected by covalent bonds

32
Q

What 4 things is Elastin used for

A

Connective tissue
Large arteries
Ligaments
Lung Wall

33
Q

How is collagen organised

A

Triple Helix secondary structure
Assembly of tropocollagen into fibres
Chemical cross linkage

34
Q

What 5 things is collagen used used

A
Connective tissue
Skin
Tendons
Cartilage
Bones
35
Q

Give 3 examples of a globular protein

A

Haemoglobin
IgG
Fibrinogen