PROTEINS Flashcards

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1
Q

What are proteins?

A

Sequence of amino acids
1 or more polypeptides
C,N,H,O

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2
Q

What are amino acids?

A

Amine group, R group, hydrogen, carbon and carboxylic group

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3
Q

What is the variable part of an amino acid?

A

The R group

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4
Q

20 amino acids commonly found in cells

A

5 are non essential- body can make them from OTHER amino acids
9 are ESSENTIAL- made from what we eat
6 are conditionally essential- young children growing

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5
Q

How do plants get amino acids

A

Make their own amino acids from glucose and nitrate ions

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6
Q

How are peptides made?

A

Amino acids joining
Carboxylic acid and amine group react
Oh in one of AA react with H in another
Peptide bond froms, h20 released , peptidyl transferase

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7
Q

Polypeptide?

A

1 reguarly repeating backbone, NCCNCCNCC

And a variable part(different R chains)

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8
Q

Are polypeptides polar ?

A

Have polarity

Ends are different with amine at one end and carboxylic at the other

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9
Q

Primary level of protein

A
Specific sequence of amino acids 
PEPTIDE BONDS (carboxyl of one and amine of next)
Particular amino acids in the sequence influence how the peptide folds to give the proteins final shape, determining its function
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10
Q

SECONDARY level of protein

A

Coiling or folding of polypeptide backbone into a 3d shape

Folding takes place as the polypetide chain grows longer, to prevent tangling

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11
Q

Alpha helix( secondary level)

A

O,H,N of amino acids reacts
Stabilized by H bonds between oxygen of a C=O and hydrogen of N-H
R groups not involved

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12
Q

Beta pleated sheet( secondary level)

A

Backbone fully extended- NOT coiled
CHains lie parallel to one another, joined by H bonds
SHeet like structure
same bonding as alpha

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13
Q

TERTIARY level of protein

A

Final 3D shape( determines protein function)

Structure is stabilized by bonds between R groups

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14
Q

What are the interactions between R groups in tertiary structure

A

Disulphide bonds
Ionic
Hydrophilic and phobic interactions
Hydrogen

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15
Q

QUATERNARY level of protein

A

2 or more individual proteins( subunits)
Same interactions as in the 3rd structure BUT between different molecules
e.g. haemoglobin

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16
Q

What are globular proteins

A

VARIED amino acid sequence
Soluble in water
Compact and spherical
Form when proteins fold into 3rd stucture

17
Q

Insulin

A

GLOBULAR
Hormone involved in regulation of blood sugar concentration
Soluble ( blood)
Made of 2 polupeptide chains joined by disulphide bonds
ALPHA chain - starts with a chain
BETA CHAIN- ends with B pleated sheet

18
Q

Haemoglobin

A

GLOBULAR
4 polypeptides- 2 a and 2 b subuntis
Each subunit contains a prosthetic haem group
fe2+ able to combine reversibly with oxygen
HELIX , water soluble

19
Q

Catalase

A
GLOBULAR
Enzyme
Converts H202 - water and oxygen 
Used iron ion to assist 
4 subunits
20
Q

Congugated protein

A

Globular proteins that contain a non protein component called a proshetic group
WITHOUT a prosthetic group= simple

21
Q

Fibrous proteins

A
Long, insoluble 
Hydrophobic R group majorities 
Limited range of AA, higher packing
AA repetiitive -organised
long chains which run PARALLEL, cross bridges= stable 
Not usually 3d
22
Q

COLLAGEN

A

High tensile strength, insoluble, nonreactive
CONNECTIVE tissue
3 polypeptides wound together in a long and strong rope like structure( triple helix)
Flexible
Skin, tendon, ligaments

23
Q

ELASTIN

A

Found in elastic fibers
Stretch and recoil
QUATERNARY
Elastic fibres found in blood vessel walls, alveoli
Made from covalent joined elastic molecules

24
Q

KERATIN

A

Hair, skin, nails
Primary sequence contains many cysteine amino acids
Can form strong disulphide bonds
Strong, inflexible and insoluble
Degree of disulphide bonds determines flexibility

25
Q

Why are globular proteins soluble

A

Hydrophobic r groups get away from aqueous environments and hydrophilic on outside of the protein = soluble