Protein Structure Flashcards

1
Q

What is definition of proteins?

A

Fundamental functional molecules of cell

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2
Q

What do proteins provide?

A
Carrier functions
Metabolic functions 
Form parts of cellular machinery 
Make up structural scaffold 
Sensing molecules
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3
Q

Describe the structure of amino acid?

A

Tetrahedral arrangement of atoms with alpha carbon at its centre
Carboxyl + amine group attached to central carbon
Variable side chain= R group
Hydrogen

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4
Q

What happens to amino acid at low pH?

A

NH2 group accepts H+ to become NH3+

H+ AA acts as base

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5
Q

What happens to amino acid at high pH?

A

The COOH group loses a proton to form COO-

OH- behaves as acid with loss of H+

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6
Q

What are 2 isomers of amino acid called?

How are they different?

A

L amino acid => found in naturally occurring proteins of living organism
D amino acid => found in cell walls of some bacteria

When viewed along axis of hydrogen C-alpha bond, L would read CORN clockwise, D would read CORN in anti-clockwise direction

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7
Q

What is a residue?

A

Each repeating unit of a polypeptide chain

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8
Q

Describe the structure of beta sheets ( secondary structure)?

A

H bonds are formed between beta sheets to stabilise sheet
2 different arrangements where sheet is parallel or antiparallel=> they are formed H bonding between adjacent beta strands connected by loops either in antiparallel or parallel arrangement

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9
Q

Describe the structure of alpha helix?

A

Right handed helix

Stabilised by H bonds between 2 amino acids, 4 residues apart

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10
Q

Describe the tertiary structure?

A

Formed from folding of secondary structure into more densely packed generally globular structure

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11
Q

Give an example of proteins that require cofactors?

A

Haem of haemoglobin
NAD
FAD
Zn2+ , Mg2+ or Other ions

Note that organic cofactors= coenzymes

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