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Proteins Flashcards

1
Q

What is a protein?

A

A macromolecule consisting of the elements carbon, hydrogen, oxygen and nitrogen, made of one or more polypeptide chains.

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2
Q

If the monomer is an amino acid, what is the polymer?

A

A peptide

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3
Q

Which groups are constant in an amino acid and which change to determine what amino acid it is?

A

Constant - amine, carboxyl, hydrogen

Change - R group

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4
Q

How many amino acids found in cells?

A

20

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5
Q

How many nonessential amino acids? Why are they non essential?

A

5, can be synthesised from other amino acids

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6
Q

How many essential amino acids? Why are they essential?

A

9, can only be found in our diet

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7
Q

How many ‘conditionally’ essential? Why are they thus?

A

6, only needed in infants and growling children

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8
Q

What are the terminals in an amino acid?

A

N terminal- amine group

C terminal- carboxyl group

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9
Q

What can an amino acid do in terms of hydrogens (protons)? WHAT IS THIS CALLED?

A

it can lose hydrogens from the CARBOXYL group, it can ‘mop up’ hydrogens from the AMINE group - AMPHOTERIC

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10
Q

Which groups in amino acids react to form peptides? What do they each give?

A

The amine group and carboxyl group.
The amine group gives H
The carboxyl group gives OH

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11
Q

What is the bond formed between two amino acids?

A

Peptide bond
O H
|| |
C—N

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12
Q

What is formed when two amino acids react?

A

A dipeptide

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13
Q

What is formed when more than 2 amino acids join?

A

A polypeptide.

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14
Q

What are the levels of protein synthesis?

A

Primary, Secondary, Tertiary, Quaternary

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15
Q

What is the primary structure?

A

The SEQUENCE of amino acids in the polypeptide chain.

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16
Q

What importance does the primary structure have?

A

It influences the shape the proteins fold into, and so influences the protein’s function.
Influences WHERE the hydrogen bonds form

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17
Q

What is the secondary structure?

A

The secondary structure is the result of formation of hydrogen bonds between different amino acids in the same chain

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17
Q

Where are the hydrogen bonds in an alpha helix

A

Between every first and fourth amino acid in the same polypeptide chain

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18
Q

Where are the hydrogen bonds in beta pleated sheet?

A

Between layers of the same polypeptide chain

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19
Q

How do hydrogen bonds formed between amino acids?

A

Between the double bonded oxygen and the hydrogen between R groups

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20
Q

What is the tertiary structure of a protein?

A

This is the interaction of Rgroups between different amino acids in the same polypeptide chain to determine the proteins shape when it folds

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21
Q

Name the different types of R group interactions in the tertiary structure, form weakest to strongest

A

Van der Waals (hydrophobic/hydrophilic)
Hydrogen
Ionic
Disulfide bridges (covalent)

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22
Q

How do you disulphide bridge bonds arise?

A

When the protein contains cysteine , which contains sulfur.

23
Q

What determines whether the amino acid chain forms an alpha helix or beta pleated sheet?

A

The load/sequence of amino acids in the chain.

24
What does high-temperature do to proteins?
High temperature will break the Van der Waals - hydrophobic/hydrophilic - attractions in the tertiary structure and the protein will unravel and lose its shape and will not be able to perform its function anymore
25
What is quaternary structure of a protein?
This is the interactions between different polypeptide chains
26
What is quaternary protein?
A protein consisting of more than one polypeptide chain
27
What are the quaternary proteins we are supposed to know?
Catalase, haemoglobin, insulin, collagen, keratin, elastin
28
What is a globular protein?
Soluble proteins with a roughly spherical shape
29
Name the globular proteins we need to know
Haemoglobin catalase insulin
30
Why are globular proteins spherical in shape?
Due to the tertiary structure. The hydrophobic amino acids abounded towards the interior whereas the hydrophilic amino acids are towards the exterior and there is an equal proportion of hydrophobic and hydrophilic amino acid that the protein had a globular shape.
31
Why are globular proteins soluble?
The hydrophilic amino acids face outwards and can interact with the water molecules
32
What is the structure of haemoglobin
- 4 polypeptide chains, 2 alpha globin 2 beta globin - Each polypeptide chain has a haem group associated with it - the haem group is a prosthetic group which contains iron
33
What is a conjugated protein and give examples?
A conjugated protein is a protein with a prosthetic group which is a non-protein component Haemoglobin Catalase
34
What is the role of iron in haemoglobin and why is this useful?
Iron allows haemoglobin to bind with oxygen reversibly which is useful because the blood may need to be oxidised or reduced depending on its pH
35
Describe the function of haemoglobin
Haemoglobin transports oxygen around the blood
36
What is the structure of catalase?
Catalase is a tetramer which means it has four polypeptide chains - 4 haem groups - Very similar to haemoglobin except the haem groups are not attached to the polypeptide chains
37
What is the function of catalase?
Catalase breaks down hydrogen peroxide which is a natural waste product in the human body and is poisonous
38
What does the iron do in catalase?
It catalyses the breakdown of hydrogen peroxide
39
Why is catalase being an antioxidant important?
It breaks down hydrogen peroxide into water and oxygen and this is important because oxidation leads to free radicals which produces chain reactions which are dangerous
40
Describe what insulin is (cell)
Insulin is a peptide hormone it cannot diffuse through the phospholipid bilayer so must attach to a receptor with a complimentary shape outside the cell so it can enter
41
Describe the structure of insulin
2 polypeptide chains one starts with alpha helix and one ends with a beta pleated sheet - disulfide bonds between chains due to cysteine
42
What is a fibrous protein?
It is a long and insoluble protein
43
Why are fibrous proteins long
They are made up of a repetitive, limited range of amino acids
44
Why are fibrous proteins insoluble?
They have a higher proportion of hydrophobic R groups then hydrophilic R groups so cannot fully arrange themselves so that the hydrophobic R groups are in the interior of the protein CANNOT INTERACT W WAER
45
Where is collegan and found?
Skin tendons Cartilage
46
What is the structure of collagen
2 polypeptide chains wrapped around each other in a helix Hydrogen bonding between the chains stabilises and strengthens the structure Cross linking covalent between collagen molecules stabilises
47
What is the structure of keratin
2 polypeptide chains with lots of cysteine and so lots of disulphide bridges lots of covalent bonds so very strong and rigid inflexible
48
Where is keratin found
Hair skin nails
49
What does keratin do in the -skin and what is it doing the -nails and hair
Skin- gives epithelial cells strength | Hair and nails- gives strength and inflexibility
50
What does keratin do to compensate for a lack of sulphur
It makes saline and hydrogen bonds to connect the polypeptide chains
51
Where is elastin found
Blood vessels, alveoli, arteries
52
What does elastin do
It expands and contracts and allows the structure to return back to its original length/shape
53
What is the structure of elastin
Many monomers calld tropoelastin connected together via interactions between the hydrophobic areas which is stabilised by cross links (covalent bonds) between lysine rich areas
54
What does elastin do in arteries
When blood passes through with lots of pressure all the elastin expands and when the blood goes back the artery contracts again
55
which amino acids dont end with an -ine and why
if they have an acidic R group
56
describe the peptide bond
- due to electron arrangement, acts as a double bond | - stiff and limited rotation

Biology (25 decks)

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