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Biology Chapter 1 (AQA) > Proteins > Flashcards

Proteins Flashcards

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1
Q

What are globular proteins?

A

Proteins formed by compact amino acid chains, then folded into intricate chains that resemble spheres

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2
Q

Are globular proteins soluble or insoluble?

A

Soluble

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3
Q

Give an example of a globular protein

A

Insulin

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4
Q

Where is insulin produced?

A

In the pancreas

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5
Q

What does insulin do?

A

It aids the bodies ability to regulate energy and metabolise sugars

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6
Q

What does insulin illustrate?

A

A proteins ability to act as a biological messenger

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7
Q

What can proteins act as?

A

Biological transport mechanisms, biological messengers and they can play a role in the structure of animal cells

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8
Q

What are conjugated proteins?

A

Proteins that function in interaction with other chemical groups

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9
Q

How are conjugated proteins attached?

A

By weak covalent bonds

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10
Q

Are conjugated proteins soluble or insoluble in water?

A

Soluble in water

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11
Q

What are proteins?

A

Long chains of amino acids

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12
Q

Give an example of a conjugated protein

A

Haemoglobin and catalase

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13
Q

What are fibrous proteins?

A

A protein with an elongated shape, forming a rod or wire like shape

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14
Q

What do fibrous proteins provide?

A

Structural support for cells and tissues

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15
Q

Give examples of fibrous proteins

A

Keratin, elastin and collagen

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16
Q

Are fibrous proteins insoluble or soluble in water?

A

Insoluble

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17
Q

What enzymes break down proteins?

A

Protease enzymes

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18
Q

What is a prosthetic group?

A

A non-protein component in globular proteins

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19
Q

What are proteins without a prosthetic group called?

A

Simple proteins

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20
Q

What is formed when a lipid and a protein combine?

A

A lipoprotein

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21
Q

What is formed when a carbohydrate combines with a protein?

A

A glycoprotein

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22
Q

What is a cofactor?

A

A prosthetic group formed by metal ions and vitamins

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23
Q

Give an example of a prosthetic group

A

A haem group which contains an iron ion

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24
Q

What contains a haem group?

A

Catalase and haemoglobin

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25
Q

What bonds form between amino acids?

A

Peptide bonds

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26
Q

How does the protease enzyme denature the protein?

A

It breaks the bonds, altering the structure, it first breaks the hydrogen bonds, then the ionic bonds and then the disulphide bridges

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27
Q

What changes in the structure of amino acids?

A

The R group, but all amino acids have the same general formula

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28
Q

What are the four structures of proteins?

A
  • primary structure
  • secondary structure
  • tertiary structure
  • quarternary structure
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29
Q

How many naturally occurring amino acids are there?

A

20, each with there own R group

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30
Q

How is a polypeptide chain formed?

A

Condensation reactions when amino acids are added to a dipeptide

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31
Q

How many polypeptides does one protein consist of?

A

One polypeptide chain

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32
Q

What is polymerisation?

A

The process by which condensation reactions take place to form a polypeptide from amino acids

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33
Q

What are the types of proteins?

A
  • Structural
  • Catalytic
  • Signalling
  • Immunological
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34
Q

What are structural proteins?

A

They are the main component of body tissues such as muscles, skin, hair and ligaments

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35
Q

What are catalytic enzymes?

A

All enzymes are proteins catalysing many biochemical reactions

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36
Q

What are signalling proteins?

A

Hormones and receptors (many of these are proteins)

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37
Q

What are immunological proteins?

A

Antibodies

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38
Q

Where is a disulphide bridge formed?

A

Between two cystine amino acids

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39
Q

What does the primary structure look like?

A

A long chain of amino acids joined by polypeptide bonds

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40
Q

What does the primary structure of the protein determine?

A

It’s shape and function

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41
Q

What are the two secondary structures?

A

Alpha helix and beta pleated

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42
Q

What bonds do the secondary structure contain?

A

Weak hydrogen bonds

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43
Q

How are weak hydrogen bonds formed?

A

Between the positive charge on the hydrogen and the negative charge on the oxygen

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44
Q

What do the hydrogen bonds cause in the secondary structure?

A

The long polypeptide chains to twist into a 3D helix

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45
Q

What is the tertiary structure?

A

The 3D protein structure which is further folded and twisted to give it a more complex 3D structure

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46
Q

How in the tertiary structure maintained?

A
  • Disulfide bonds
  • Ionic bonds
  • hydrogen bonds
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47
Q

What are disulphide bonds?

A

Bridges formed between cystine, they are strong and difficult to break

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48
Q

What are ionic bonds?

A

Bonds formed between carboxyl and amino groups that are not involved in the formation of peptide bonds, they are weaker than disulphide bridges

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49
Q

What are hydrogen bonds like?

A

Hey are numerous but they are weak and easily broken

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50
Q

What is the bond between two amino acids?

A

A dipeptide bond

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51
Q

How are peptide bonds formed?

A

The joining of amino acids by a condensation reaction

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52
Q

What are the four groups in an amino acids?

A
  • Amino group
  • Carboxyl group
  • Hydrogen atom
  • R side group
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53
Q

Where does the peptide bond form?

A

Between the carbon atom of one amino acid and the nitrogen atom of another

54
Q

Where is the water produced in the condensation reaction

A

The OH from the carboxyl group and the H from the amino group

55
Q

What is the process of the formation of a polypeptide

A

Polymerisation

56
Q

Why can hydrogen bonds form between proteins?

A

The NH group has an overall positive charge whilst the O has an overall negative charge so they are therefore polar

57
Q

What is the test for proteins?

A

The biuret test

58
Q

What does the biuret test detect?

A

Peptide bonds

59
Q

How do you carry out the biuret test?

A
  • Place a sample of the solution in a test tube and add equal volume of sodium hydroxide solution at room temperature
  • Add a few drops of very dilute (0.05%) copper (II) sulfate solution and mix gently
60
Q

What result identifies a protein?

A

Purple coloration

61
Q

What is the negative result?

A

The solution remains blue

62
Q

What is the primary structure of collagen?

A

An unbranded polypeptide chain

63
Q

What is the secondary structure of collagen?

A

Very tightly wound

64
Q

What is the tertiary structure of collagen?

A

The chain is twisted into a second helix

65
Q

What is the quarternary structure of collagen?

A

Three polypeptide chains would together

66
Q

Where is collagen found?

A

Tendons

67
Q

How do autotrophic green plants produce amino acidsz?

A

As a product of photosynthesis

68
Q

How do heterotrophic organisms gain their amino acids?

A

From plants through food chains

69
Q

What do simple proteins have in their structure?

A

Only amino acids

70
Q

Give examples of simple proteins

A

Albumins, globulins and scleroproteins

71
Q

What do conjugated proteins contain?

A

Amino acids and some other type of chemical molecule

72
Q

What is the prosthetic group in a a nucleoprotein?

A

Nucleic acids

73
Q

What is the prosthetic group in a phosphoprotein?

A

Phosphoric acid

74
Q

What is the prosthetic group in lipoprotein?

A

A lipid

75
Q

What does haemoglobin contain?

A

4 poly peptide chains each of which has a porphyrin ring which contains the iron ion

76
Q

What does pH affect?

A

How the amino acids and proteins ionise

77
Q

How does the carboxylic acid group ionise?

A

RCOOH <=> RCOO- + H+

78
Q

How does the amino group ionise?

A

RNH2 + H+ <=> RNH3+

79
Q

How does a high pH effect the ionisation of the carboxylic acid?

A

The reaction will be pushed to the left

80
Q

How does a high pH effect the ionisation of the amine group?

A

The reaction will be pushed to the right

81
Q

In a high pH environment with the amino acids be positively or negatively charged?

A

The amino acids will predominantly be positively charged cations

82
Q

How does a low pH effect the ionisation of the carboxylic acid?

A

The reaction will be pushed to the right

83
Q

How does a low pH effect the ionisation of the amine group?

A

The reaction will be pushed to the left

84
Q

In a low pH environment with the amino acids be positively or negatively charged?

A

The amino acids will predominantly be negatively charged anions

85
Q

When will a zwitterion form?

A

When there is an intermediate hydrogen ion concentration where the forward and the backwards rates of reaction for the ionisation of the carboxylic acid and the ionisation of the amine group are equal

86
Q

Why will a zwitterion form?

A

Because the amino acid will carry 50% of the amine groups uncharged and 50% of the amine groups charged and will carry 50% of the carboxylic acid group charged and 50% of the carboxylic acid group uncharged

87
Q

What will pH of zwitterion formation dictate?

A

The isoelectric point

88
Q

Why do different enzymes have different optimum pH’s?

A

Because the isoelectric point is different for each specific amino acid or protein

89
Q

What is the iso-electric point?

A

The pH at which the amino acids or protein carry no net charge/ carry equal amounts of negative and positive charges

90
Q

Will the charge on the active sites of an enzymes affect the capability of the enzyme to join with its specific substrate?

A

Yes, that’s why enzymes tend to work best at specific pH’s

91
Q

How does pH affect solubility?

A

At the IEP opposite charges attract making protein molecules clump together and precipitate. At other pH’s the protein will only carry like charges which will repel molecules from each other which can increase the solubility.

92
Q

What happens to proteins at extremes of pH

A

The protein molecules will carry huge numbers of like charges (as the ionisations of the amine groups and the carboxylic acid groups will go almost to completion). These charges may exert a large repulsive force which breaks apart the hydrogen and ionic bonds holding the 3D structure together. Therefore the 3D structure therefore breaks apart and the protein is denatured.

93
Q

What is denaturation?

A

The loss of function of a protein caused by a loss of structure

94
Q

As well as ph what is another agent of denaturation?

A

Heat

95
Q

How does heat cause denaturation

A

It can disrupt the hydrogen and ionic bonds therefore causing the 3D structure to unravel.

96
Q

At what temperature do most proteins denature?

A

45 degrees

97
Q

Which bonds in proteins can withstand the higher temperatures?

A

Sulphur bonds therefore proteins containing the most sulphur bonds can withstand the highest of temperatures

98
Q

What are the functions of proteins?

A
  • Structural proteins
  • Enzymes
  • Hormones
  • Contractile proteins
  • Storage proteins
  • Transport proteins
  • Protective proteins
  • Buffers
  • Osmotic proteins
  • Toxins
99
Q

Give examples of structural proteins

A
  • Collagen
  • Elastin
  • Keratin
  • Lipoproteins
  • Fibroin
  • Sclerotin
  • Mucoproteins
100
Q

Give examples of enzymes

A
  • hydrolases such as; amylase, proteases and lipases used in digestion
  • oxido-reductases such as the dehydrogenase used in the metabolic cycle and ligases
101
Q

Give examples of hormones

A
  • somatotropin
  • pituitary growth hormone
  • insulin
102
Q

Give examples of contractile proteins

A
  • actin
  • myosin
  • dynein
103
Q

Give examples of storage proteins

A
  • ovalbumin
  • casein
  • lactalbumins
  • glutelins
  • gliadins
  • ferritin
104
Q

Give examples of transport proteins

A
  • haemoglobin
  • myoglobin
  • plasma albumin
  • transferritin
  • binding globulins
105
Q

Give examples of protective proteins

A
  • thrombin
  • fibrinogen
  • antibodies
106
Q

Give an example of a buffer

A

Haemoglobin

107
Q

Give an example of an osmotic protein

A

Plasma albumin

108
Q

Give examples of toxins

A
  • phospholipase
  • clostridium tetani
  • clostridium botulinum
  • diphtheria
  • ricin
109
Q

What is the function of ligases?

A

They enable molecules to be bond together using energy from ATP

110
Q

Where is actin and myosin found?

A

Muscles

111
Q

What does dynein make up?

A

The structure of cilia and flagella

112
Q

Why can’t amino acids be stored as just amino acids?

A

Because of the toxic amine groups

113
Q

How do you store amino acids?

A

As proteins

114
Q

What is ovalbumin, casein and lactalbumin?

A

Milk proteins

115
Q

What are glutelins and gliadins?

A

Cereal seed proteins

116
Q

What is ferritin?

A

A protein that binds up iron and stores it in the spleen, liver and red bone marrow

117
Q

How do transport proteins work?

A

By binding onto and releasing insoluble or inadequately soluble substances so they can be transported through the body

118
Q

What does haemoglobin do?

A

Transports oxygen in vertebrate blood

119
Q

What does myoglobin do?

A

Transports oxygen in muscles

120
Q

What does plasma albumin do?

A

Transports fatty acids in the blood

121
Q

What does transferritin do?

A

Transports iron through blood to the iron storage sites

122
Q

What do binding globulins do?

A

Transports insoluble thyroid hormones through the blood

123
Q

What are thrombin and fibrinogen?

A

Blood clotting factors which reduce bleeding during injury

124
Q

What are antibodies?

A

Proteins that react with antigens to neutralise them therefore giving protection against disease

125
Q

What is a buffer?

A

A substance that is resistant to changes in pH

126
Q

How does haemoglobin work as a buffer?

A

It reacts with hydrogen ions to form reduced haemoglobin which can buffer blood between 7.2 and 7.6

127
Q

How does plasma albumin work?

A

It maintains blood volume by maintaining the water level in blood plasma. Cell sap has the same role in plants

128
Q

What are phospholipases?

A

Enzymes found in snake venom which destroy cell membranes

129
Q

What are clostridium tetani, clostridium botulinum and diphtheria?

A

Bacteria that release toxic chemicals, harmful to humans

130
Q

What is ricin?

A

A toxic chemical that can cause jaundice

131
Q

What elements are present in proteins?

A

Carbon, hydrogen, oxygen and nitrogen are present (without including elements present in R groups)

Biology Chapter 1 (AQA) (32 decks)

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