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Biology > M1:03 Proteins and amino acids > Flashcards

M1:03 Proteins and amino acids Flashcards

1
Q

What percentage of the organic matter of a cell is made up of protein?

A

50%

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2
Q

What are proteins made up of?

A

large molecules made up of carbon, hydrogen, oxygen and nitrogen. some contain sulphur

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3
Q

Name the main functions of proteins

A
  • structural components eg of bone and muscle- membrane carriers and pores eg for active transport and facillitated diffusion - all enzymes are proteins - many hormones are proteins - antibodies are proteins -important for growth and repair in all organisms
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4
Q

What are all proteins made from?

A

amino acids

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5
Q

Why are proteins large molecules?

A

as they are polymers (large chains of monomers, ie amino acids)

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6
Q

What are amino acids?

A

monomers that make up proteins

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7
Q

describe the makeup of an amino acid

A

they all have the same basic structure, an amino group at one end (left) an acid group on the right and a carbon in between (with a H and an R group )

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8
Q

What is a ‘backbone’ in terms of amino acids?

A

amino acids joined end to end repeatedly.

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9
Q

How many types of naturally occuring amino acids are there?

A

20

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10
Q

What is glycine?

A

the simplest form of an amino acid.

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11
Q

How are amino acids differentiated?

A

their R groups are all different

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12
Q

Describe some charactertistics an R group could possess.

A

positively/negatively charged hydrophobic/hydrophillic

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13
Q

How do plants obtain amino acids?

A

they are able to manufacture the necessary amino acids, providing they can receive nitrate from soil

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14
Q

What is nitrate used for in plants?

A

it is converted into amino groups and bond to organic groups made from the products of photosynthesis

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15
Q

How do animals obtain proteins?

A

as part of their diet

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16
Q

What are amino acids used for in animals?

A

they are digested to amino acids which can then build other proteins

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17
Q

What are essential amino acids and how many are there?

A

8-10 of the 20 amino acids that cant be built from materials they take into the body

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18
Q

Where are most essential amino acids found?

A

in meat

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19
Q

How do vegetarians obtain essential amino acids?

A

via soy milk

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20
Q

Can animals store excess amino acids?

A

no

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21
Q

What is deamination and why is it necessary?

A

the process by which amino acids are removed, as too much amino group can turn toxic

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22
Q

Where does deamination take place in animals?

A

in the liver, where the amino groups are removed and converted into urea, which is removed in urine.

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23
Q

How do DIFFERENT amino acids join with each other?

A

via condensation reactions, forming covalent bonds

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24
Q

What is the bond formed between two amino acids and what is the new molecule formed?

A

peptide bonddipeptide

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25
Q

How are peptide bonds broken down?

A

hydrolysis, which uses a water molecule to break the bond

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26
Q

How are polypeptides formed?

A

by joining many dipeptides together

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27
Q

Why are amino acids in a polypeptide chains sometimes referred to as and why?

A

amino acid residues because part of the molecule is lost in the condensation reaction that produces the peptide bonds.

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28
Q

Where are proteins and polypeptide synthesised?

A

on the ribosomes

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29
Q

Describe protein synthesis

A

information is used in the form of messenger RNA (mRNA) to put amino acids in the right order to make a specific polypeptide chains.as the mRNA passes through the ribosome, amino acids join together one at a time

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30
Q

What determines the sequence of amino acids being produced?

A

the mRNA

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31
Q

What determines the function of each protein

A

its structure of its amino acids

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32
Q

What is a primary structure?

A

the primary structure is given by the specific sequence of amino acids that make up the protein

33
Q

How do you calculate the number of different amino acid combinations?

A

multiply the number of possibilities at each point eg if there is a peptide chain that is 4 amino acids long there would be 20x20x20x20 possibilities (160000)

34
Q

What catalyses the formation and breakages of peptide bonds?

A

protease enzymes

35
Q

Give 2 examples of protease enzymes

A

Hormone regulation ageing

36
Q

How is hormone regulation an example of protease enzymes in action?

A

as it is vital that hormones are broken down so that their effects arent permanent and can be controlled.

37
Q

How is ageing an example of protease enzymes in action?

A

As we get older, skin loses elasticity and becomes more wrinkled because older skin is less able to rebuild the protein collagen and other proteins that give younger skin its smooth and elastic properties

38
Q

What determines the order that amino acids are bonded together in?

A

DNA

39
Q

Why does the secondary structure form?

A

As when a longer chain forms, it prevents tangling and breaking by stabalising parts of the chain by coiling/ pleating it.

40
Q

What affects the amount of coiling/pleating of amino acids?

A

the types of amino acids being added to the chain/ the primary structure

41
Q

What are the three levels of structure

A

primarysecondary tertiary

42
Q

What happens when the secondary structure is formed?

A

a chain of amino acid coils into an alpha helix or folds into a beta pleated sheet held together by hydrogen bonds

43
Q

What bonds are present in the secondary structure?

A

hydrogen bonds (also peptide bonds between the amino acids)

44
Q

Why are there so many hydrogen bonds in a secondary structure?

A

as they are individually weak but together they give the structure stability

45
Q

What is a tertiary structure?

A

overall 3D structure of the final polypeptide chain

46
Q

give an example of how a tertiary structure is vital for its function

A

a hormone must be specifically shaped in order to fit in the hormone receptor of a target cell

47
Q

What must an enzyme have to function and why?

A

must have an active site, with a shape that is complimentary to that of its substrate

48
Q

What are the 4 kinds of bonds that stabalise the tertiary structure

A

disulfide bonds ionic bonds hydrogen bonds hydrophyllic and hydrophobic bonds

49
Q

When is a disulfide bond used in tertiary structures?

A

When to cysteines (a type of amino acid containing sulphur) are close together

50
Q

When is a ionic bond used in tertiary structures?

A

When oppositely charged amino acids are close to each other (as the R-groups sometimes carry charge)

51
Q

When is a hydrogen bond used in tertiary structures?

A

whereever slightly charged R-groups are close to one another

52
Q

When is a hydrophobic bond used in tertiary structures?

A

in a water based enviroment, hydrophobic amino acids will be most stable if they are held together with water excluded

53
Q

When is a hydrophillic bond used in tertiary structures?

A

in a water based enviroment, hydrophyllic amino acids tend to be found on the outside in globular proteins with the hydrophobic amino acids in the middle

54
Q

What happens when you heat a protein?

A

the kinetic energy is increased, which causes the molecule to vibrate and break down some of the bonds holding the tertiary structure in place

55
Q

Why are the bonds in tertiary structure quite easily broken?

A

as they are not covalent bonds.

56
Q

What happens during denaturisation?

A

when enough heat is applied the whole tertiary structure can unravel and the protein will no longer function

57
Q

What are the two main catagories for 3D shape of proteins

A

globularfibrous

58
Q

Describe a globular protein

A

they tend to roll up into a compact globe, any hydrophobic R-groups are turned inwards towards the centre of the structure and the hydrophillic R-groups tend to be on the outside. making the protein water soluble as water can cluster around them

59
Q

Why are globular proteins soluble in water

A

as the hydrophillic R-groups are on the outside so the water molecules easily cluster around them.

60
Q

Describe fibrous proteins.

A

they form fibres, most of which have regular, repetitive sequences of AA and are usually insoluble in water.

61
Q

What is the role of globular proteins?

A

metabolic roles

62
Q

What is the role of fibrous roles?

A

structural roles

63
Q

Give some examples of globular proteins

A

-enzymes found in all organisms- plasma proteins and and antibodies found in the blood of mammals

64
Q

Give some examples of fibrous proteins

A

-collagen found in bone and cartilage-Keratin found in fingernails and hair

65
Q

What is a quaternary structure?

A

proteins that are made up of more than one polypeptide subunit joined together, or a polypeptide and an inorganic component.

66
Q

Give an example of proteins with quaternary structure

A

haemoglobin insulin

67
Q

What does haemoglobins quaternary structure consist of?

A

4 polypeptide subunits, 2 alpha and 2 beta

68
Q

is haemoglobin molecule soluble in water?

A

yes

69
Q

What is haemoglobins function?

A

to carry oxygen from the blood to the tissues

70
Q

What is in the haem group?

A

the part of the haemoglobin that contains an iron ion which is responsible for the colour of haemoglobin

71
Q

What is the colour of haemoglobin, and oxyhaemoglobin

A

haemoglobin- red/purpleoxyhaemoglobin - bright red

72
Q

What is a prosthetic groups?

A

a group that is not made of amino acids but are a part of the molecule, eg haem groups.

73
Q

What is collagen?

A

a fibrous protein that is made up of 3 polypeptide chains wound round each othereach of the 3 chains are in coils, made up of around 1000 amino acids with hydrogen bonds form between the chains giving it structural strength.

74
Q

How is the strength of collagen increased further?

A

hydrogen bonds between the 3 polypeptide chains, and each collagen molecules form covalent bonds called cross links with other collagen molecules next to it.

75
Q

How are collagen fibres formed?

A

Many collagen fibrils bonding together

76
Q

What is the function of collagen?

A

to provide mechanical strength in many areas

77
Q

Give 5 examples of how collagen provides mechanical strength in many areas?

A
  • in the walls of arteries, a layer of collagen prevents blood that is being pumped from the heart at high pressure from bursting the walls.
  • Tendons connect skeleton muscles to the bones, that are mostly collagen.
  • bones are formed from collagen, reinforced such as calcium phosphate to make them hard.- cartilage and connective tissue are made of collagen
  • cosmetic treatments using collagen are becoming increasingly popular, eg its injected in the lips to give them a fuller appearance
78
Q

Name the 5 key differences between haemoglobin and collagen

A

globular protein- fibrous proteinsoluble- insolublewide range of amino acids- 35% is glycinecontains prosthetic group haem- no haemalpha helix structure - left handed helix structure

Biology (10 decks)

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