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AQA A-Level Biology A > Pack 1 - Biological Molecules > Flashcards

Pack 1 - Biological Molecules Flashcards

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1
Q

Why do some scientists believe that all life on earth originated from a common ancestor?

A

The cells of all living organisms contain only a few groups of carbon-based compounds that act in similar ways.

This also proves indirect evidence for evolution.

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2
Q

What are two uses of carbohydrates within living organisms?

A

Main use: Used by cells as respiratory substrates.

Secondary use: To form structural components in plasma membranes and cell walls

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3
Q

What are three uses of lipids within living organisms?

A

Bilayer of plasma membranes

Certain hormones

Respiratory substrates

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4
Q

What is the most common component of cells?

A

Water

(Hence, our search for life elsewhere in the universe involves a search for liquid water).

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5
Q

What is the definition of a monomer?

A

Monomers are the smaller units from which larger molecules are made.

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6
Q

What is the definition of a polymer?

A

Polymers are molecules made from a large number of monomers joined together.

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7
Q

Give three examples of a monomer

A

Monosaccharides

Amino acids

Nucleotides

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8
Q

Define condensation reaction

A

A condensation reaction:
Joins two molecules together (forming a chemical bond)

Involves the elimination of a water molecule.

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9
Q

Define hydrolysis reaction

A

A hydrolysis reaction:
Breaks a chemical bond between two molecules

Involves the use of a water molecule.

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10
Q

Name 3 common biological molecules throughout all species on Earth

A

Carbohydrates

Lipids

Water

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11
Q

What monomer makes up proteins/polypeptides?

A

Amino acids

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12
Q

What monomer makes up polysaccharides?

A

Monosaccharides

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13
Q

What monomer makes up starch?

A

a-glucose

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14
Q

What monomer makes up glycogen?

A

a-glucose

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15
Q

What monomer makes up cellulose?

A

b-glucose

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16
Q

What monomer makes up DNA?

A

DNA nucleotide

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17
Q

What monomer makes up RNA?

A

RNA nucleotide

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18
Q

Define organic (in biochemistry)

A

Carbon based (excluding eg. CO2)

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19
Q

Give an example of a condensation reaction

A

Alcohol + Carboxylic Acid -> Ester (+Water)

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20
Q

What does hydrolysis literally mean?

A

Hydro - Water

Lysis - Breaking

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21
Q

Give an example of a hydrolysis reaction

A

Digestion

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22
Q

What does carbohydrate literally mean?

A

Carbo - Carbon
Hydrate - Water
CH20

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23
Q

What does monosaccaride literally mean?

A

Mono - One

Saccharide - Sugar

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24
Q

What does mono- mean?

A

One

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25
Q

What does di- mean?

A

Two

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26
Q

What does tri- mean?

A

Three

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27
Q

What does tetra- mean?

A

Four

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28
Q

What does penta- mean?

A

Five

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29
Q

What does hexa- mean?

A

Six

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30
Q

What does hepta- mean?

A

Seven

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31
Q

What is the molecular formula of Glucose?

A

C6H12O2

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32
Q

What is the general formula of a monosaccharide?

A

CnH2nOn

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33
Q

What is the general name of a sugar?

A

(number) -ose

Eg. Hexose such as glucose

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34
Q

Name 6 monosaccharides

A

Glucose
Fructose
Galactose

Mannose
Ribose
Deoxyribose

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35
Q

What is the hydroxyl group configuration of a-glucose?

A

/<=>\

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36
Q

What is the hydroxyl group configuration of b-glucose?

A

/<=>/

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37
Q

What is the definition of an isomer?

A

A molecule with the same chemical formula but in a different arrangement

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38
Q

How does fructose differ from a-glucose?

A

a-glucose b-glucose
CH2OH H
<=> H <=> CH2OH

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39
Q

What is the main use of monosaccharides within living organisms?

A

Energy from respiration

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40
Q

What is the food test for reducing sugars?

A

Add Benedict’s solution to the sample
Mix and heat in a water bath

Look for a brick-red precipitate to form which indicates the presence of reducing sugar

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41
Q

Name 3 disaccharides

A

Maltose
Sucrose
Lactose

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42
Q

What monosaccharides does maltose consist of?

A

a-glucose

a-glucose

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43
Q

What monosaccharides does sucrose consist of?

A

a-glucose

fructose

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44
Q

What monosaccharides does lactose consist of?

A

a-glucose

galactose

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45
Q

What monosaccharide is found in maltose, sucrose and galactose?

A

Glucose (a)

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46
Q

Describe the bonds between the monosaccharides of maltose, sucrose and lactose

A

1,4

glycosidic

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47
Q

What type of bond is formed when monosaccharides join together?

A

Glycosidic

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48
Q

What are disaccharides mainly used for in living organisms?

A

Respiration energy

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49
Q

Which disaccharide is commonly found in fruit?

A

Sucrose

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50
Q

Which disaccharide is commonly found in milk?

A

Lactose

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51
Q

Define polysaccharide

A

Polymers
Of many glucose (monosaccharide) monomers
Joined together
In chains

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52
Q

Name 3 common polysaccharides

A

Glycogen
Starch
Cellulose

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53
Q

What monosaccharide is glycogen made of?

A

a-glucose

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54
Q

What monosaccharide is starch made of?

A

a-glucose

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55
Q

What monosaccharide is cellulose made of?

A

b-glucose

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56
Q

What is the role of glycogen?

A

Animal energy storage (glucose) (liver)

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57
Q

What is the role of starch?

A

Plant energy storage (glucose)

58
Q

What is the role of cellulose?

A

Gives strength to plant cell walls

59
Q

How does glucose within starch bond?

A

Mostly 1,4

Occasionally 1,6 (which forms branches)

60
Q

Describe the structure of starch

A

Compact
Branched
Spherical
Insoluble

61
Q

Why is being insoluble important for starch?

A

No osmotic effect/
Does not affect water potential/
Does not leave cell

62
Q

Why is it important for starch to have a compact (coiled) structure?

A

So more energy can be stored

63
Q

Why is starch coiled?

A

Linked 1,4 and 1,6

64
Q

Why is it important that starch has branches?

A

So that it is readily hydrolysed

65
Q

What is the test for presence of starch?

A

Add iodine/potassium iodide to sample

Colour change to black/blue indicates presence of starch

66
Q

Describe the structure of glycogen

A

Compact
Very branched
Soluble

67
Q

How does glucose within glycogen bond?

A

Linked by 1,4

Many 1,6 as well

68
Q

What is the difference between starch and glycogen?

A

Starch is energy storage in plants

Glycogen is energy storage in animals

69
Q

Why is glycogen soluble in water?

A

Many 1,6 bonds
Leaving exposed hydroxyl groups
Which react with water

70
Q

Describe the structure of cellulose

A

Compact
In chains
No branches
Insoluble

71
Q

Why are cellulose chains able to bond?

A

Hydrogen bonds

72
Q

What do the OH bonds between cellulose chains create?

A

Hydrogen bonds

Forming cellulose fibrils

73
Q

What is the name of an OH group?

A

Hydroxyl group

74
Q

What must happen to enable the OH groups (of the monosaccharides) react to make a glycosidic bond?

A

Monosaccharides must get close together

75
Q

How do hydrogen bonds form?

A

Oxygen is electronegative so
O is δ-
H is δ+
Adjacent O and H are attracted to each other

76
Q

Is a hydrogen bond weak or strong?

A

Weak

77
Q

Are many hydrogen bonds together weak or strong?

A

Strong

78
Q

Why is cellulose polymers fully permeable?

A

Because there are gaps between the fibrils

79
Q

What are the links between two cellulose chains called?

A

Crosslinks

80
Q

Is the b-1,4 bond easy or difficult to break?

A

Difficult - resists digestion by enzymes

81
Q

How do herbivores such as cows manage to digest grass?

A

Don’t produce cellulase
So have to grow bacteria in stomach
Called a symbiotic relationship

82
Q

What cellular structure is made out of cellulose?

A

Plant cell walls

83
Q

Give 5 features of cellulose

A 
No branches
'Flip flop' structure
H bond crosslinks
Long chains
Bonds difficult to break
84
Q

Why does cellulose’s lack of branches link to its function?

A

Close together chains making it insoluble

85
Q

How does cellulose’s flip flop structure relate to its function?

A

Makes a large molecule due to long, repeating chains

Hydrogen bonds

86
Q

How are cellulose’s H bond crosslinks related to its function?

A

Provide strength in large numbers

87
Q

How does cellulose’s long-chained structure link to its function?

A

Provides structural rigidity

88
Q

How does cellulose’s difficult-to-break bonds link to its function?

A

They resist digestion

89
Q

Name two groups of lipids (fats)

A

Triglycerides

Phospholipids

90
Q

What do triglycerides consist of?

A

Three fatty acids

One glycerol

91
Q

What bonds do lipids form?

A

Ester

92
Q

What is the functional group called on a fatty acid?

A

Carboxyl (acid) group

93
Q

What is the chain on a fatty acid called

A

C Skeleton

94
Q

What is the general formula for a fatty acid C skeleton

A

(CH2)n(CH3)

95
Q

How many water molecules are released in the formation of a triglyceride?

A

Three

96
Q

What is the variable region of a molecule called?

A

R

97
Q

What allows fatty acids to be different lengths?

A

Hydrocarbon skeleton length

98
Q

Define saturated fat

A

A fat that has the maximum number of hydrogen atoms in them

i.e. They contain no double or triple bonds between the carbon atoms

99
Q

Define unsaturated fat

A

A fat where not all potential hydrogen atoms are within its structure
i.e. It contains double or triple binds between its carbon atoms

100
Q

What is the difference between monounsaturated and polyunsaturated fats?

A

Monounsaturated fats contain one double bond

Polyunsaturated fats contain more than one double bond

101
Q

What is fat used for in biological organisms?

A 
Insulation
Vital organ protection
Energy storage
Releases water when hydrolysed
Energy storage
Oils waterproof skin
102
Q

What is the food test for lipids?

A

Add ethanol
Mix/shake
Add water
White emulsion indicates presence of lipids

103
Q

How do phosphates form?

A

When a phosphoric acid combines with a glycerol

104
Q

Describe the structure of a phospholipid

A

Phosphate and glycerol in the head

Two fatty acid ‘tails’

105
Q

Why is a phospholipid polar?

A

The phosphate group makes the head hydrophilic

The tails are hydrophobic

106
Q

Name an important use of phospholipids

A

Forming (phospho)lipid bilayers

Which act as a barrier around cells

107
Q

Name two differences between the properties of phospholipids and triglycerides

A

Triglycerides store more fats (for energy) than phospholipids

Phospholipids are polar so they are good emulsifiers

108
Q

Why are phospholipids good emulsifiers?

A

Head is 𝛿+ (hydrophilic)

Tail is 𝛿- (hydrophobic)

109
Q

Why are triglycerides good insulators?

A

They are poor conductors of heat and form in thick layers of fatty tissue when accumulated

110
Q

Why are triglycerides good storage molecules?

A

Contain 3 fatty acids each

111
Q

Name 5 properties of water

A

Polar ∴ adhesion & cohesion/surface tension
Universal solvent - for other polar molecules
High specific heat capacity
Expands when solid
High latent heat of vaporisation

112
Q

What are adhesion and cohesion?

A

Adhesion - Water sticking to the sides of the tube it is in, forming a meniscus

Cohesion - Water ‘sticking’ to itself

113
Q

Why is water adhesive and cohesive?

A

Adhesive - because some materials (such as glass) can be more polar than the water itself so water is attracted to the glass

Cohesive - because it is polar and the 𝛿+ H’s bond with the 𝛿- O’s

114
Q

Give a practical example of adhesion and cohesion

A

Adhesion - capillary tubes or glass beakers

Cohesion - drinking straws or xylem

115
Q

Why is water a good solvent for other polar molecules?

A

Water can become so heavily attracted to other molecules that it can disrupt the attractive forces within the solute

116
Q

Why does water have a high specific heat capacity/latent heat of vaporisation?

A

The hydrogen bonds within water require a lot of heat to break

117
Q

Why is water’s latent heat of vaporisation important?

A

Water, such as ponds, maintains an almost constant temperature providing a stable environment for fish all year round

118
Q

Why is water’s high specific heat capacity important?

A

Animals sweat which involves transferring lots of heat into a small amount of water for it to evaporate.

119
Q

What is latent heat of vaporisation?

A

Water takes a long time to heat meaning there is a long lag time between temperature change from air to water.

120
Q

What is high specific heat capacity?

A

The amount of heat water can absorb or release during a state change

121
Q

Why does water expand when it freezes?

A

The water molecules link in such a way (due to hydrogen bonding) that there are large gaps between the water molecules.

122
Q

Why is water’s expansion when freezing important to marine life?

A

The ice floats and acts as a heat barrier, sustaining the marine life underneath

123
Q

What is surface tension?

A

The skin that water forms in contact with air

124
Q

How does surface tension occur?

A

The water molecules near the surface of the water bond stronger and form more closely together due to fewer water molecules to bond with

125
Q

What is the constant stream of water from the roots through the stem and then out through the leaf called?

A

Transpiration

126
Q

What tube-like transport cells of plants carry columns of water up plants from the roots to the leaves?

A

Xylem

127
Q

Define organic chemistry

A

Chemistry that is carbon-based (except carbonates, oxides and dioxides)

128
Q

Name two places that inorganic ions occur within organisms

A

Cytoplasm

Body fluids

129
Q

What is another name for a hydrogen ion?

A

Proton

130
Q

What does pH stand for?

A

Potenz Hydrogen

131
Q

What does a low pH tell you about the number of hydrogen ions present?

A

There are more

132
Q

What ions exist in quarternary structure of haemoglobin?

A

Fe2+

133
Q

Describe the structure of a haemoglobin

A

4 Polypeptides

4 Fe2+ ions

134
Q

What is the role of iron bonds in haemoglobin?

A

Iron bonds to oxygen to form oxyhaemoglobin

135
Q

Define co transport

A

Two molecules passing through protein channels at the same time

136
Q

How do sodium ions help the absorption of glucose and amino acids in the digestive tract?

A

Sodium ions are removed from the blood

This means that sodium ions from the lining of the gut are absorbed

But this time they carry glucose and amino acids with them

137
Q

What is primary protein structure?

A

A chain of amino acids

138
Q

What is secondary protein structure?

A

A chain of amino acids where hydrogen bonds cause the chains to become bent

139
Q

What is tertiary protein structure?

A

Amino acids wrapped tightly together due to hydrogen, ionic and covalent bonds

140
Q

What is quaternary protein structure?

A

When two proteins in tertiary form are bonded together

AQA A-Level Biology A (5 decks)

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