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A Level Biology - 2.1.2 Biological molecules > Proteins > Flashcards

Proteins Flashcards

1
Q

How do proteins exist?

A

Not as long straight chains because the R group causes the polypeptide to fold

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2
Q

Why do R groups interact with each other?

A

Their different properties and this causes the poly tide to fold to form final protein

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3
Q

What is primary structure?

A

The sequence of amino acids in a polypeptide

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4
Q

How are amino acids held together?

A

By peptide bonds

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5
Q

What does the sequence of amino acids determine?

A

Where certain R groups occur which determines which bonds can occur and where, deciding the shape of the final protein e.g. enzymes and their active site

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6
Q

What is secondary structure?

A

The folding and coiling caused by hydrogen bonding between hydrogen and oxygen of nearby amino acids

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7
Q

What is an alpha helix?

A

It is when hydrogen bonds pull the peptide chain into coils

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8
Q

What are beta pleated sheets?

A

Polypeptide chains lying parallel in sheets held together by hydrogen bonds where the pattern forms pleats

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9
Q

What is tertiary structure?

A

Brought about by further folding of secondary structure caused by bonds and interactions between R groups

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10
Q

What are the 4 types of bonds within tertiary structure?

A

Hydrogen bonds, hydrophobic interactions, ionic bonds and disulfide bonds

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11
Q

What are hydrogen bonds?

A

Weak attraction caused by H being shared between 2 atoms

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12
Q

What are hydrophobic interactions?

A

Weak association between R groups that do not dissolve in water

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13
Q

What are ionic bonds?

A

Weak attraction between groups of opposite charge

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14
Q

What are disulfide bonds?

A

Strong covalent bonds between cysteine amino acids

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15
Q

What happened when all bonds break in tertiary structure?

A

Te protein experiences denaturalisation and the whole protein unravels

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16
Q

What is the order the bonds within tertiary structure break?

A
  1. Hydrophobic interactions
  2. Hydrogen bonds
  3. Ionic bonds
  4. Disulfide bonds
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17
Q

Where do hydrogen bonds form?

A

Also between hydrogen and nitrogen?

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18
Q

What do disulfide bonds form?

A

Between R groups containing -SH groups

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19
Q

What is quaternary structure?

A

The level of structure where two or more polypeptide subunits are bonded together, and the subunits can be identical or different.

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20
Q

What are 4 examples of quaternary structure?

A

Insulin - two different subunits, haemoglobin - two sets of identical subunits, antibodies - light and heavy chains and catalase with 4 different subunits.

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21
Q

What are the two shapes of proteins?

A

Globular or fibrous

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22
Q

What are characteristics of globular proteins?

A

Usually soluble in water and have metabolic roles

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23
Q

What are examples of globular proteins?

A

Haemoglobin, enzymes and antibodies

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24
Q

What are characteristics of fibrous proteins?

A

Usually insoluble and have structural roles

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25
Q

What are examples of fibrous proteins?

A

Silk, collagen and keratin

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26
Q

What type of protein is haemoglobin?

A

A conjugated protein

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27
Q

What is the structure of haemoglobin?

A

It has a quaternary structure with 2 alpha polypeptides, 2 beta polypeptides and 4 haem prosthetic groups

28
Q

How is haemoglobin shaped?

A

It is ball shaped with a hydrophilic group towards the exterior and hydrophobic towards the interior so is soluble.

29
Q

Where is haemoglobin located?

A

Within red blood cells

30
Q

What is the role of haemoglobin?

A

Transports oxygen from the lungs to be released in the tissue

31
Q

How many oxygen molecules can bind to haemoglobin?

A

One oxygen molecule to each iron in the 4 haem groups

32
Q

How is the shape important?

A

It is important to how well it can bind and release oxygen

33
Q

Where is the haem located?

A

In the centre of each subunit, so it’s protected from being oxidised and destroyed by the oxygen it transports

34
Q

What is insulin?

A

A hormone involved in blood glucose regulation

35
Q

Where is insulin transported?

A

In the blood so it needs to be soluble

36
Q

What do hormones do?

A

They fit into the specially shaped receptor proteins on cell surface membranes

37
Q

What does tertiary structure do for hormones?

A

It gives the hormone a precise shape to fit the receptor

38
Q

What is catalase?

A

An enzyme specific to a particular reaction

39
Q

What is catalase’s substrate?

A

Hydrogen peroxide

40
Q

Where does hydrogen peroxide come from?

A

ApIt is a common by-product of metabolism but it damages cells and organelles

41
Q

What is the structure of catalase?

A

It is a quaternary protein with 4 haem prosthetic groups

42
Q

How does catalase work?

A

Iron (II) ions are present which allows catalase to interact with hydrogen peroxide and speed up its breakdown which produces oxygen and water

43
Q

Where is catalase found?

A

In all cells

44
Q

What is the equation for the breakdown of hydrogen peroxide?

A

2H₂O₂ -> 2H₂O + O₂

45
Q

What are features of fibrous proteins?

A

They are insoluble molecules with high proportions of hydrophobic R groups and are not folded into complex 3D shapes, their amino acids usually have a limited range of small amino acids which leads to a very organised structure.

46
Q

What are examples of fibrous proteins?

A

Keratin, elastin and collagen

47
Q

Where is keratin found?

A

In hair, skin and nails

48
Q

Where is elastin found?

A

Walls of blood vessels and alveoli

49
Q

Where is collagen found?

A

Skin, tendons, ligaments and nervous tissue

50
Q

What does keratin contain?

A

A large proportion of sulfur containing amino acids with many strong bonds

51
Q

What is keratin like as a protein?

A

It is strong, inflexible and insoluble

52
Q

What determines the flexibility of keratin?

A

The number of bonds

53
Q

Where is elastin present?

A

Elastic fibres

54
Q

What is the structure of elastin?

A

It has a quaternary structure made of many stretchy molecules called tropoelastin

55
Q

Why is elastin flexible?

A

It is essential for lining arteries which need to expand and return to its original shape

56
Q

What is the structure of collagen?

A

It has a quaternary structure with each polypeptide chain a coil made of 1000 amino acids which 3 of the r wish together in a triple helix to form a molecule

57
Q

What are the amino acids in collagen?

A

Every 3rd amino acid is glycine and there are as many prolines and hydroxyproline amino acids and the R groups are small

58
Q

What do collagen molecules form?

A

Hydrogen bonds and covalent bonds called cross links with two other collagen molecules to form fibrils

59
Q

What do crosslinks do?

A

They are staggered along the molecules to give strentgh and flexibility

60
Q

What do fibrils for,?

A

They are joined by together to form a collagen fibre of quaternary structure

61
Q

What is collagen a component of?

A

Bone, cartilage, tendons and wall of arteries providing mechanical strength such as tendons, ligaments and skin

62
Q

What are tendons and ligaments?

A

They are mostly collagen with many fibres in large bundles and they connect skeletal muscle to bone, forming strong connections to pull bones for movement

63
Q

What is collagen’s purpose in skin?

A

The fibres form a mesh that is resistant to tearing

64
Q

How are bones formed?

A

From collagen plus calcium phosphate to make them hard

65
Q

How is collagen used cosmetically?

A

It is injected for example into lips to make them look fuller

A Level Biology - 2.1.2 Biological molecules (7 decks)

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