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Biology > 3. Biological Molecules > Flashcards

3. Biological Molecules Flashcards

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1
Q

What is covalent bonding?

A

Atoms are stable when they have a full outer shell of electrons
Atoms achieve this by sharing their outer shell electrons
This also creates a strong covalent bond between the atoms

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2
Q

What is a condensation reaction?

A

Occurs when two molecules are joined together with the removal of water

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3
Q

What is hydrolysis ?

A

Occurs when two molecules are split apart with the addition of water

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4
Q

What are condensation and hydrolysis reactions used for?

A

The bonding and splitting apart of biological molecules in living things

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5
Q

What are monomers?

A

The single units that join together to make polymers

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6
Q

What are polymers?

A

Multiple monomers joined together to form a polymer chain

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7
Q

What is the monomer and polymer for carbohydrates?

A

Monomer=monosaccharides

Polymer= polysaccharide

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8
Q

What is the monomer and polymer for proteins?

A

Monomer= amino acids

Polymer=polypeptides and proteins

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9
Q

What is the monomer and polymer for nucleic acids?

A 
Monomer= nucleotides 
Polymer= DNA and RNA
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10
Q

What do water molecules consist of?

A

2 hydrogen atoms each covalently bonded to one oxygen atom

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11
Q

Why is water polar?

A

Oxygen molecules consist of 2 hydrogens and 1 oxygen.
The oxygen atom is slightly negative and the hydrogen atoms are slightly positive.
When this happens the molecule is describes as polar.

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12
Q

What is a hydrogen bond?

A

A weak interaction which happens wherever molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen atom.
They are not very strong but do provide stability

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13
Q

What is specific heat capacity?

A

The energy needed to raise the temperature of 1 gram of a substance by 1 °C

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14
Q

What is the specific heat capacity of water?

A

It is high

4.2 j/kg°C

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15
Q

What gives water a high specific heat capacity?

A

The hydrogen bonds between water molecules can absorb a lot of energy, so it takes a lot of energy to break them

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16
Q

Why is it important that water has a high specific heat capacity?

A

It means that water doesn’t experience rapid temperature changes, which is one of the properties that make it a good habitat as the temperature doesn’t get too hot or too cold so the organisms inside die.

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17
Q

What is latent heat of evaporation?

A

How much energy it takes to evaporate a substance

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18
Q

Why does water have a high latent heat of evaporation?

A

It takes a lot of thermal energy to break the hydrogen bonds within the water molecules so a lot of energy is used up when water evaporates

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19
Q

Why is water’s high latent heat of evaporation useful for its function?

A

It means it’s useful for cooling things (why some mammals sweat when they’re hot)
When sweat evaporates, it cools the surface of the skin because it takes a lot of thermal energy to evaporate water, so when it does it takes a lot of thermal energy with it.

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20
Q

What is glucose?

A

A monosaccharide with six carbon atoms (so it is a hexose monosaccharide)
There are 2 forms
Alpha (α)and beta (β)

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21
Q

What is the structure of alpha glucose?

A

Has a ring of 5 carbons and one oxygen
It has one carbon covalently bonded to carbon 5
It has a H2O molecule bonded to carbon 1
The hydrogen is above the plane and the hydroxyl (OH) is below

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22
Q

What is the structure of beta glucose?

A

Has a ring of 5 carbons and one oxygen
It has one carbon covalently bonded to carbon 5
It has a H2O molecule bonded to carbon 1
The hydrogen is below the plane and the hydroxyl (OH) is above

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23
Q

What is the function of glucose?

A

It is the main energy source in animals and plants.
A reactant in respiration, the energy released is used to make ATP
Its structure makes it soluble so it can be easily transported.
Its chemical bonds contain lots of energy

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24
Q

What is the formula for glucose?

A

C6H12O6

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25
Q

What is the molecular formula of alpha glucose?

A

C6 H12 O6

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26
Q

What is the role of alpha glucose?

A

Energy source, component of starch and glycogen which are energy stores

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27
Q

What type of sugar is alpha glucose?

A

Hexose

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28
Q

What is the molecular formula of beta glucose?

A

C6 H12 O6

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29
Q

What is the role of beta glucose?

A

Energy source, component of cellulose which provides structural support in plant cells

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30
Q

What type of sugar is beta glucose?

A

Hexose

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31
Q

What is the molecular formula of ribose?

A

C5 H10 O5

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32
Q

What is the role of ribose?

A

Component of ribonucleic acid (RNA and NAD)

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33
Q

What type of sugar is ribose?

A

Pentose

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34
Q

What is the molecular formula of deoxyribose?

A

C5 H10 O4

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35
Q

What is the role of deoxyribose?

A

Component of deoxyribonucleic acid (DNA)

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36
Q

What type of sugar is deoxyribose?

A

Pentose

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37
Q

What is the difference between ribose and deoxyribose?

A

Ribose has an OH molecule on both carbon 2 and 3

Deoxyribose has an OH on carbon 3 but just an H on carbon 2.

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38
Q

What are monosaccharides joined together by?

A

Glycosidic bonds

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39
Q

How are glycosidic bonds formed?

A

A hydrogen atom on one monosaccharide bonds to the hydroxyl group on the other releasing a molecule of water. This is a condensation reaction

40
Q

What are disaccharides?

A

Two monosaccharides bonded together

41
Q

What monosaccharides make up maltose?

A

2 alpha glucose

42
Q

What monosaccharides make up sucrose?

A

Alpha glucose

fructose

43
Q

What monosaccharides make up lactose?

A

Beta galactose

Alpha glucose

44
Q

What monosaccharides make up cellobiose?

A

2 Beta glucose

45
Q

What are homopolysaccharides?

A

Polysaccharides composed of a single type of sugar monomer

46
Q

What is the respiration equation?

A

Glucose + Oxygen — (energy to make ATP) — Carbon dioxide + water

47
Q

What are the functions of polysaccharides?

A

Glucose molecules are joined together into polysaccharides, to create an energy store.

48
Q

How do plants and animals store energy?

A

Plants store energy as starch in chloroplasts and membrane bound starch granules.
Animals store energy as glycogen in cells of the muscle and liver

49
Q

What makes polysaccharides good stores of energy?

A

Glycogen and starch are compact so they don’t occupy much space in the cell.
Polysaccharides hold glucose in chains so they can be ‘snipped off’ by hydrolysis when needed for respiration.
Polysaccharides are less soluble in water due to their large size so they don’t effect the water potential of the cell.

50
Q

What are the 3 types of polysaccharide energy sources?

A

Amylose and amylopectin in plants

Glycogen in animals

51
Q

What is the structure on amylose ?

A

A chain of alpha glucose molecules, it has glycosidic bonds between carbon 1 & 4.
It coils into a spiral shape with hydrogen bonds holding the spiral in place.
Hydroxyl (OH) groups on carbon 2 are situated on the inside of the coil making the molecule less soluble and maintaining the coil’s structure.

52
Q

What is the structure on amylopectin ?

A

Like amylose with bonds between carbons 1 & 4 but also has branches formed by glycosidic bonds between carbons 1 & 6.
It coils into a spiral shape, but with branches emerging from the spiral.

53
Q

What is the structure on glycogen ?

A

Like amylopectin it has glycosidic bonds between carbon 1 & 4 and 1 & 6 which forms branches.
The 1-4 bonds are smaller so glycogen has less tendency to coil.
However, it has more branches which makes it more compact and easier to remove monomer units as there are more ends.

54
Q

What is cellulose?

A

It found in plants, forming cell walls.
It is a tough, insoluble and fibrous substance.
It is a homopolysaccharide made from long chains of beta glucose molecules.

55
Q

What is the structure of cellulose?

A

Beta glucose molecules have glycosidic bonds between carbon 1 & 4.
They are straight because every other beta glucose molecule in the chain is rotated 180 degrees.
The hydroxyl group on carbon 2 enables hydrogen bonds to be formed between chains.

56
Q

How does cellulose form plant cell walls?

A

When 60-70 cellulose chains bond together they form microfibrils , which are up to 10-30nm in diameter.
These are bundled together into macrofibrils containing up to 400 microfibrils.

57
Q

What are the properties of cellulose and cellulose cell walls?

A

Micro and macrofibrils have a high tensile strength due to the glycosidic and hydrogen bonds.
Macrofibrils run in all directions in the wall for extra strength.
It is difficult to digest cellulose because the glycosidic bonds between the glucose molecules are hard to break.

58
Q

How do the properties of cellulose cell walls help its function?

A

Plants don’t have a rigid skeleton, so each cell has strength to support the plant.
The cell wall is fully permeable.
It has a high tensile strength which prevents the cell from bursting when turgid.
The wall also protects the delicate cell membrane.

59
Q

What are lipids?

A

A group of substances that are soluble in alcohol rather than water.
They contain large amounts of carbon and hydrogen and small amounts of oxygen.
They are insoluble in water because they are not polar so do not attract water molecules.

60
Q

What are the 3 most important lipids in living things?

A

Triglycerides, phospholipids and cholesterol

They are macromolecules not polymers

61
Q

What are macromolecules?

A

Very large, organic molecules

62
Q

What are saturated fatty acids?

A

There are no C=C bonds in the molecule

63
Q

What are unsaturated fatty acids?

A

There is a double bond between two of the carbon atoms, which means that fewer hydrogen atoms can be bonded to the molecule

64
Q

What does monounsaturated and polyunsaturated mean?

A 
Monounsaturated = there is only one C=C bond 
Polyunsaturated = there are multiple C=C bonds
65
Q

What effect does C=C bonds have on a fatty acid?

A

It changes the shape of the hydrocarbon chain, giving it a kink where the double bond is.
These kinks push the molecules apart slightly so they are more fluid and their melting point is lower.

66
Q

How do 3 fatty acids bond to a glycerol molecule to form a triglyceride?

A

Through a condensation reaction.
A water molecule is produced from the hydrogen from the hydroxyl of the glycerol and the OH from the carboxyl.
The covalent bond formed is known as an ester bond

67
Q

What are the 5 functions of triglycerides?

A

Energy source, insulation, buoyancy, protection and energy store

68
Q

How are triglycerides good energy sources?

A

They can be broken down in respiration to release energy and generate ATP.
The Ester bonds are hydrolysed then the glycerol and fatty acids are broken down to carbon dioxide and water.

69
Q

How are triglycerides good energy stores?

A

Because triglycerides are insoluble in water, they can be stored without affecting the water potential of the cell.

70
Q

How do phospholipids act in water?

A

The phosphate group is polar so is attracted to water.
However, the fatty acid tails are non-polar so they are repelled by water.
Therefore, they may form a layer on the surface of water with the tails sticking out.
They may form micelles, tiny balls with tails tucked inside.

71
Q

What does hydrophilic mean?

A

Attracted to water

e.g. the head of the phospholipid

72
Q

What does hydrophobic mean?

A

Repelled by water

e.g. the tail of a phospholipid

73
Q

What does amphipathic mean?

A

When a molecule has both hydrophobic and hydrophilic elements

74
Q

What is the phospholipid bilayer?

A

When amphipathic phospholipids form membranes around cells and organelles.
Either side of the membrane is an aqueous solution.
The phospholipids form a bilayer with 2 rows of phospholipids, the tails point onwards and the heads point outwards into the solution.

75
Q

What are the properties of the phospholipid bilayer?

A

The individual phospholipids are free to move, but will not move into any position where their hydrophobic tails are exposed to water, providing some stability.
It is only possible for small, non-polar molecules to pass through the tails.
This lets the membrane control what goes in and out of the cell.

76
Q

What is cholesterol?

A

A type of lipid which is not made from glycerol or fatty acids.
It is a small hydrophobic molecule, which means it can sit in the middle of the hydrophobic part of the bilayer

77
Q

What is the function of cholesterol?

A

It regulates the fluidity of the membrane, preventing it from becoming too fluid or too stiff

78
Q

What are the functions of proteins?

A

Form structural components of animals e.g. muscles are made of protein
They can act as enzymes
Membranes contain proteins that act as carriers and pores for active transport across the membrane and facilitated diffusion.

79
Q

What is an ‘R’ group?

A

Found in amino acids
It does not stand for a particular element, but is different in each amino acid.
e.g. in glycine, it is an H atom

80
Q

What are amino acids joined together by?

A

Peptide bonds

81
Q

How are peptide bonds formed and broken?

A 
Formed= condensation reaction
Broken= hydrolysis
82
Q

Which enzymes catalyse the formation and breaking of peptide bonds?

A

Protease enzymes break peptide bonds during digestion

They also break down protein hormones so their effects aren’t permanent.

83
Q

What is the primary structure of proteins?

A

The sequence of amino acids found in a molecule

84
Q

What is the secondary structure of proteins?

A

When an amino acid either coils into an alpha helix or a beta pleated sheet.

85
Q

What is the quaternary structure of proteins?

A

A protein structure that consists of more than one polypeptide chain.

86
Q

What is the tertiary structure of proteins?

A

The overall three-dimensional shape of a protein molecule.

87
Q

What are fibrous proteins?

A

Have a regular, repetitive sequence of amino acids, usually insoluble in water.
This allows them to form fibres, which usually have a structural function

88
Q

What are globular proteins?

A

Tend to roll up into spherical shapes.
Hydrophilic groups are on the outside.
Water molecules bind to them making them soluble in water.
They often have specific shapes which helps them to take up roles as enzymes, hormones and haemoglobin

89
Q

What are examples of fibrous proteins?

A

Collagen
Keratin
Elastin

90
Q

What are examples of globular proteins?

A

Haemoglobin
Insulin
Pepsin

91
Q

What is the test for starch?

A

Iodine solution

Positive= yellow-brown —> blue black

92
Q

What is a reducing sugar?

A

Substances that can give electrons to other molecules

93
Q

What is the test for a reducing sugar?

A

Heat with Benedict’s solution

Positive= blue —> green —> yellow —> orange

94
Q

What is the test for lipids?

A

Mix with ethanol and filter

Positive = cloudy white

95
Q

What is the test for proteins?

A

Biuret test
Negative= blue
Positive= deep purple

Biology (13 decks)

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