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AQA A-Level Biology > Biological Molecules > Flashcards

Biological Molecules Flashcards

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1
Q

What is a monomer?

A

a small unit which larger molecules are made from

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2
Q

What is a polymer?

A

molecules made from large numbers of monomers joined together

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3
Q

Carbohydrates, proteins, lipids, and nucleic acids contain which elements? (2)

A

Carbon and Hydrogen

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4
Q

What type of bond can carbons form? and how many per carbon?

A

4

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5
Q

What are the three types of carbohydrates?

A

Monosaccharides, Disaccharides and Polysaccharides

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6
Q

What is a monosaccharide?

A

A single sugar monomer

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7
Q

What is the function of a monosaccharide?

A

energy for respiration, building blocks for polymers.

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8
Q

What are two examples of monosaccharides?

A

Ribose and Glucose

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9
Q

What is a Disaccharide?

A

Two monosaccharides joined together via a condensation reaction (which forms a glycosidic bond)

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10
Q

What is the function of a Disaccharide?

A

Sugar found in germinating seeds (maltose), mammal milk sugar (lactose)

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11
Q

What are two examples of Disaccharides?

A

Maltose, Sucrose, Lactose

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12
Q

What is a Polysaccharide?

A

A polymer formed by many monosaccharides joined by a glycosidic bond in a condensation reaction

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13
Q

What is the function of a Polysaccharide?

A

energy stores in plants, structural- cell wall

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14
Q

When does a condensation reaction occur?

A

When monomers combine together by covalent bonds to form polymers (polymerisation) or macromolecules and water is removed

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15
Q

What happens in the hydrolysis of polymers?

A

Covalent bonds are broken when water is added

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16
Q

What is a reducing sugar?

A

A sugar that can donate electrons

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17
Q

What happens when reducing sugars donate electrons?

A

The carboxyl group becomes oxidised and the sugars become the reducing agent

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18
Q

What is the test for sugars?

A

Benedict’s test

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19
Q

Why can reducing sugars be detected via Benedict’s test?

A

They reduce the soluble copper sulphate to insoluble brick-red copper oxide

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20
Q

What are two examples of a reducing sugar?

A

glucose, fructose, galactose

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21
Q

What is a non-reducing sugar?

A

A sugar that can’t donate electrons or be oxidised

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22
Q

How are non-reducing sugars detected?

A

They are hydrolysed and then put through benedict’s test

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23
Q

Why are non-reducing sugars hydrolysed before they are tested with Benedict’s solution?

A

To break the disaccharide into its two monosaccharides

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24
Q

What is an example of a non-reducing sugar?

A

Sucrose

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25
Q

What is the molecular formula for glucose?

A

C6 H12 O6

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26
Q

What are the two types of glucose?

A

α (alpha) glucose, β (beta) glucose

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27
Q

What is the difference between α and β glucose?

A

The hydroxyl group on the right side of the ring is below the ring in α glucose, and in β glucose it is above the ring

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28
Q

What is removed from the glucose when a glycosidic bond is formed?

A

one water molecule

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29
Q

What type of reaction forms glycosidic bonds?

A

condensation reaction

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30
Q

How is a glycosidic bond broken?

A

When water is added in a hydrolysis reaction

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31
Q

What are the three ways the chains in a polysaccharide can be organised?

A

Branched/unbranched, Folded, Straight

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32
Q

What is starch?

A

The storage polysaccharide of plants

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33
Q

What is glycogen?

A

The storage polysaccharide for plants and fungi

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34
Q

What are the two groups of lipids?

A

Triglycerides and phospholipids

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35
Q

What is a triglyceride?

A

Three fatty acid chains attached to a glycerol molecule

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36
Q

What are the monomers of a triglyceride?

A

Glycerol and fatty acids

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37
Q

What are the two types of fatty acids?

A

Saturated and unsaturated

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38
Q

What type of bonds are in a saturated fatty acid?

A

the bonds between the carbons in the ‘tail’ are all single bonds

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39
Q

What are the two types of unsaturated fatty acids?

A

Mono-unsaturated and Poly-unsaturated

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40
Q

What is a mono-unsaturated fatty acid?

A

A fatty acid that has single bonds between carbon atoms

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41
Q

What is a poly-unsaturated fatty acid?

A

A fatty acid that has double bonds between carbon atoms

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42
Q

What are the functions of triglycerides?

A

Energy storage, Insulation, Buoyancy, Protection

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43
Q

What is a phospholipid?

A

two fatty acids bonded to a glycerol molecule with a phosphate group

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44
Q

Which part of the phospholipid is hydrophobic and which part is hydrophilic?

A

The head (glycerol and phosphate group) is hydrophilic and the tails are hydrophobic.

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45
Q

What is the role of a phospholipid?

A

It’s the main component of cell membranes

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46
Q

What is the chemical test for lipids?

A

The emulsion test

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47
Q

Describe the chemical test for lipids and the positive and negative results.

A

Add ethanol to the sample being tested and then shake it, then add the mixture to a test tube of water. If lipids are present, the solution will turn cloudy, and the more lipid present, the cloudier the solution will be. If there is no lipid present, the solution remains clear.

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48
Q

What are proteins?

A

polymers made of amino acids

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49
Q

What determines the function of amino acids?

A

The sequence, type and number

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50
Q

What do proteins make up?

A

Enzymes, cell membranes, hormones, immunoproteins, transport proteins, structural proteins, contractile proteins

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51
Q

How are dipeptides formed?

A

Condensation reaction between two amino acids

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52
Q

How are polypeptides formed?

A

Condensation reaction between 3 or more amino acids

53
Q

How are peptide bonds broken?

A

In a hydrolysis reaction- the water breaks the peptide bond and it gets broken down into amino acids

54
Q

How many levels of structure are there in proteins?

A

4- primary, secondary, tertiary, quaternary

55
Q

What is the primary structure of proteins?

A

Amino acids bonded by covalent peptide bonds

56
Q

What is the secondary structure of proteins?

A

It happens when the negatively charged nitrogen and oxygen atoms form with a positively charged hydrogen atom to form hydrogen bonds

57
Q

What shapes can form in secondary structured proteins due to the hydrogen bonds>

A

α-helix and β-pleated sheet

58
Q

When does the α-helix shape occur?

A

When the hydrogen bonds are formed between every fourth peptide bond

59
Q

When does the β-pleated sheet shape form?

A

When the protein folds so that two parts of the polypeptide chain are parallel to each other so hydrogen bonds form between the parallel peptide bonds

60
Q

What types of proteins have secondary structures?

A

Fibrous proteins (collagen and keratin)

61
Q

What does the secondary structure relate to?

A

The hydrogen bonds forming between the amino group and the carboxyl group

62
Q

How can the hydrogen bonds be broken in secondary structured proteins?

A

High temperatures and pH changes

63
Q

What is the tertiary structure of proteins?

A

The 3D configuration when R groups interact

64
Q

How is the tertiary structure different from the secondary structure of proteins?

A

The tertiary structure has additional bonds forming between the R groups

65
Q

What are the additional bonds in the tertiary structure of proteins? (Where are they found?)

A

Hydrogen (between R groups), Disulphide (only found between cysteine amino acids), Ionic (found between charged R groups), Weak hydrophobic interactions (found between non-polar R groups)

66
Q

In what type of protein is the tertiary structure most common?

A

Globular proteins

67
Q

When does a protein have a quaternary structure?

A

When they have more than one polypeptide chain working together as a functioning macromolecule

68
Q

What is an example of a protein with a quaternary structure?

A

Haemoglobin

69
Q

How can disulfide bridges be broken?

A

Reduction (gaining electrons)

70
Q

What is the test for proteins?

A

The biuret test

71
Q

How is the biuret test carried out?

A

A few drops of a copper sulphate solution are added to the sample

72
Q

What does a positive test for proteins look like?

A

The solution changes from blue to lilac in colour when protein is present

73
Q

What are some features of globular proteins?

A

They are compact, spherical, and soluble in water

74
Q

Why are globular proteins spherical?

A

The non-polar hydrophobic R groups are in the center (away from the aqueous surroundings) the polar hydrophilic R groups are on the outside of the protein.

75
Q

What are fibrous proteins?

A

Long strands of polypeptide chains that have cross-linkages due to hydrogen bonds

76
Q

Do fibrous proteins have tertiary structures?

A

They have little or none

77
Q

Why are fibrous proteins insoluble in water?

A

They have large numbers of hydrophobic R groups

78
Q

What type of structure does haemoglobin have? (why?)

A

It has a quaternary structure (because it has 4 polypeptide chains (they are globin proteins and each has a prosthetic haem group))

79
Q

How are the 4 globin chains held together?

A

By disulphide bonds

80
Q

How are the globin chains arranged?

A

The hydrophobic R groups are facing inwards (to preserve the 3D spherical shape) and the hydrophilic R groups are facing outwards (helps to maintain solubility)

81
Q

What does the prosthetic haem group contain that makes it able to combine with an oxygen molecule?

A

It contains an iron II ion (Fe2+)

82
Q

How many oxygen molecules can each haemoglobin carry?

A

Each of the four haem groups can carry 4 oxygen molecules (so 8 oxygen atoms total)

83
Q

True or false: Collagen is the most common structural protein found in vertebrates.

A

True

84
Q

What type of protein is collagen?

A

Fibrous protein that is also insoluble

85
Q

How many polypeptide chains are needed to form collagen?

A

3

86
Q

What holds those polypeptide chains together in collagen and what shape does it form?

A

Hydrogen bonds and it forms a triple helix

87
Q

What other type of bond is present in collagen?

A

Covalent bonds

88
Q

Why are the covalent bonds there?

A

To form cross-links between R groups of amino acids in interacting triple helices. The cross-links hold the collagen molecules together to form fibrils

89
Q

Why are the collagen molecules positioned in the fibrils?

A

So that there are staggered ends

90
Q

What is an enzyme?

A

A biological catalyst

91
Q

What is a catalyst?

A

Something that speeds up the rate of chemical reactions without being used up or changed

92
Q

What type of protein are enzymes?

A

Globular proteins

93
Q

What happens at an enzyme’s active site?

A

It is where the specific substrate binds to the enzyme which forms an enzyme-substrate complex

94
Q

What type of enzymes are produced and function inside the cell?

A

Intracellular enzymes

95
Q

What type of enzyme catalyses reactions outside cells?

A

Extracellular

96
Q

What type of enzyme normally carries out digestion? (Why?)

A

Extracellular enzymes (because macromolecules being digested are too large to enter the cell

97
Q

What can denature an enzyme’s active site?

A

Extremes of heat or pH

98
Q

What must happen for the reaction to occur when the substrate hits its respective enzyme?

A

It must hit it at the right orientation and speed

99
Q

What determines the shape of the active site?

A

The complex tertiary structure of the protein that makes up the enzyme

100
Q

True or False: the enzyme-substrate complex is formed permanently

A

False- it is temporary and the products are released

101
Q

What are the two types of enzyme reactions?

A

Catabolic and anabolic

102
Q

What is a catabolic reaction?

A

It is the breakdown of complex molecules into simpler products (more than one product is released)

103
Q

What are examples of catabolic reactions?

A

Cellular respiration and hydrolysis

104
Q

What is an anabolic reaction?

A

The building of more complex molecules from simpler ones by drawing two or more substrates into the active site and forming bonds between them and releasing a single product

105
Q

What are two examples of anabolic reactions?

A

Protein synthesis and Photosynthesis

106
Q

How do enzymes work in relation to energy change?

A

They lower the activation energy of a reaction which provides an alternative energy pathway.

107
Q

Why are enzymes highly specific?

A

Because of their globular shape (tertiary structured protein)

108
Q

Describe the induced fit model.

A

The substrate doesn’t fit perfectly into the active site at the start so the active site changes shape (conformational change) to allow the substrate to bind. The enzyme then breaks the substrate down and releases the products

109
Q

What happens if an enzyme is at a temperature which is lower than its specific optimum temperature?

A

-Molecules move slowly
-Lower frequency of successful collisions
-Substrate and enzymes collide with less energy, making it harder to form bonds

110
Q

What happens if an enzyme is at a temperature higher than its specific optimum temperature?

A

Reactions are faster as:
-Molecules move more quickly
-Higher frequency of successful collisions
-Substrate and enzymes collide with more energy (more likely that bonds are going to be formed)

111
Q

What happens when the enzyme becomes denatured?

A

-Bonds holding the enzyme molecule in its specific shape break
-Tertiary structure of protein changes
-Permanent damage to the active site- substrate can no longer bind to it

112
Q

What happens to enzymes at extremes of pH?

A

Hydrogen and ionic bonds (which are holding the tertiary structure of the protein) break because of an excess of H+ ions and OH- ions
-Alters the shape of the active site

113
Q

What do you use to investigate the effect of pH on the rate of an enzyme-catalysed reaction?

A

Buffer solutions of specific pH values

114
Q

What happens if you have a high concentration of enzymes?

A

There are more active sites so there is a higher chance of an enzyme-complex formation

115
Q

The greater the substrate concentration the ______ rate of reaction

A

higher

116
Q

What is the point of active site saturation?

A

Where all of the enzymes are being used but there are still substrates.

117
Q

What are the two types of enzyme inhibitors?

A

Competitive and non-competitive

118
Q

What is a competitive inhibitor?

A

A molecule that has a similar shape to the substrate molecules sp it ~competes~ with the substrate for the enzyme’s active site.

119
Q

What is a non-competitive inhibitor?

A

A molecule that binds to the enzyme at an alternative site which alters the shape of the site and stops the substrate from binding to it

120
Q

What is the role of DNA?

A

To store genetic information

121
Q

What is the role of RNA?

A

Transfer genetic code to ribosomes

122
Q

What are the components of DNA nucleotides?

A

-Deoxyribose sugar with hydrogen
-Phosphate group
-a nitrogenous base (A,C,G,T)

123
Q

What are the components of RNA nucleotides?

A

-a ribose sugar with hydroxyl group
-a phosphate group
-one nitrogenous base (A,C,G,U)

124
Q

What are the complimentary base pairs of DNA?

A

A+T
C+G

125
Q

Where are ribosomes located in cells?

A

In the cytoplasm or attached to the rough endoplasmic reticulum

126
Q

What happens at ribosomes?

A

Protein synthesis

127
Q

What is semi-conservative replication of DNA?

A

Where a parent cell copies its DNA before it divides so each of the 2 daughter cells get a single strand each from the parent cell

128
Q

Why is retaining one DNA strand important?

A

Genetic continuity

AQA A-Level Biology (11 decks)

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