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CCEA AS Biology Unit 1 > U1T1 - Biological Molecules > Flashcards

U1T1 - Biological Molecules Flashcards

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1
Q

What are living organisms mainly made up of?

A

Carbon, hydrogen, oxygen, nitrogen, phosphorous + sulphur.

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2
Q

How are the elements in a water molecule bonded? What is its polarity? What does this allow?

A

Each hydrogen atoms shares a pair of electrons with the oxygen atom, this is a covalent bond. Ion slightly +, oxygen slightly -. Uneven charge distribution makes it polar. Hydrogen bonds with next water molecule.

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3
Q

Water is a good solvent, how does this work?

A

Charged molecules + ions dissolve in it + the polar water molecules form clusters called hydration shells around them due to strong forces of attraction.

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4
Q

What is the positive thing about a substance being liquid rather than solid?

A

Its molecules/ions can move about more freely so it is more chemically reactive.

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5
Q

Where do the majority of cell’s reactions take place?

A

Aqueous solutions.

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6
Q

Do non-polar substances mix with water, what does this mean? Are they hydrophobic or hydrophilic?

A

No, they can separate aqueous solutions into compartments. Hydrophobic.

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7
Q

Why are hydrophobic reactions important?

A

They help maintain stability of membranes, protein molecules, nucleic acids + other sub cellular structures.

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8
Q

What are the main properties of water? (4)

A

Solvent, polar, transport medium + transparent.

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9
Q

Where might water be used as a transport medium?

How is Its transparency useful?

A

Blood, lymphatic + excretory systems.

Allows plants to photosynthesise in deep water.

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10
Q

What are the 2 groups of inorganic ions?

A

Macronutrients + micronutrients.

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11
Q

Give examples of inorganic ions. (4)

A

Potassium, calcium, magnesium + iron.

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12
Q

Where are these biologically important compounds found, give their formula?:
Calcium pectate, chlorophyll, haemoglobin, ATP, nucleic acids + phospholipids.

A

Middle lamella in cell walls (Ca2+), chloroplasts for photosynthesis (Mg2+), Red blood cells (Fe2+), Energy from photosynthesis (PO4^3-), nucleotides in DNA (NO3^-) + cell surface membrane (PO4^3-)

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13
Q

What is the role of phosphate in inorganic ions?

A

Phospholipids determine structure + function of cell surface membrane, ATP used for energy, major part of bone + teeth (deficiency = stunted growth + bone malformation), DNA made of nucleotides which have phosphate.

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14
Q

What is the role of calcium in inorganic ions?

A

Cell walls of adjacent cells glued together by middle lamella (calcium + mg pectate), main part of bones, teeth + shells, blood clotting + muscle contraction, deficiency = stunted growth, rickets + delayed blood clotting.

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15
Q

What is the role of iron in inorganic ions?

A

Haemoglobin has 4 polypeptide chains which contain haem which contains iron. Each molecule has 4 haems so can pick up 4 oxygens. Synthesis of chlorophyll.

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16
Q

What is the role of magnesium in inorganic ions?

A

Chlorophyll contains mg which absorbs light energy. Deficiency = chlorosis.

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17
Q

What is the role of nitrate in inorganic ions?

A

Nitrogen is In amino acids, proteins, vits, nucleotides, coenzymes, chlorophyll + some hormones. (auxin + insulin) Deficiency = chlorosis + stunted growth.

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18
Q

What is the role of hydrogen carbonate in inorganic ions?

A

Ions important as natural buffer.

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19
Q

What is the role of potassium in inorganic ions?

A

Transmission of electrical impulses, assists active transport, protein synthesis, present In sap vacuoles so maintains turgidity. Deficiency = yellow edged leaves.

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20
Q

Give examples of organic molecules. (3)

A

Carbohydrates, lipids + proteins.

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21
Q

What are organic molecules made up of? How are they joined?

A

Monomers, polymerisation to polymers.

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22
Q

What would a change in tertiary structure cause in a protein?

A

Affects its function.

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23
Q

What do buffers do? Examples of buffers?

A

Ensures enzymes operate at their optimum pH. Hydrogen carbonate ions + blood proteins (albumin)

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24
Q

What does albumin do? What pH should blood be?

A

Acts as a buffer + regulates water potential of blood. pH 7.35 to 7.45.

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25
Q

What elements are in carbohydrates? What is the ratio of hydrogen to oxygen? What are the 3 main groups?

A

Carbon, hydrogen + oxygen. 2:1. Monosaccharides, disaccharides + polysaccharides.

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26
Q

Give examples of monosaccharides? (3)

A

Glucose, fructose + galactose.

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27
Q

What does glucose do?

A

Plants make it through photosynthesis, transport it in blood for respiration, building block for larger molecules (cellulose, starch + glycogen), major energy source.

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28
Q

What is the formula of glucose?
What type of sugar is it?
What form does it exist in? (not straight)

A

C6H12O6. Hexose sugar.

Ring/cyclic structure.

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29
Q

Give examples of disaccharides. (3) What monosaccharides are each of them made of?

A

Maltose (a-glucose + a-glucose), sucrose (a-glucose + fructose) + lactose. (a-glucose + galactose)

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30
Q

When a condensation reaction occurs, and a glycosidic bond is formed, what do we call it. (x, x glycosidic bond)

A

The carbons it formed between are numbered. It may be a 1,4 or a 1,6.

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31
Q

How might a disaccharide be broken down?

A

A hydrolysis reaction.

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32
Q

Give 4 main properties of disaccharides.

A

Same general formula (C12H22O11)
Taste sweet
Soluble
Sugars

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33
Q

Give examples of reducing sugars. (5)

What disaccharide is not a reducing sugar?

A

Glucose, fructose, galactose, maltose + lactose.

Sucrose.

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34
Q

What are the 3 most important polysaccharides and their uses?

A

Starch (energy store), glycogen (energy store) + cellulose (structure)

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35
Q

What 2 polysaccharides is starch made up of?

A

Amylose + amylopectin. Contains a-glucose.

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36
Q

How is starch stored in seeds + chloroplasts?

A

Starch grains.

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37
Q

Why is starch such a good storage molecule?

A

Compact (coiled), insoluble (osmosis, if glucose, lots of water would move in) + readily converted to sugars. Found in plants.

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38
Q

How is starch readily converted to sugars?

A

Amylopectin means there are lots of terminal glucose, meaning glucose are easily hydrolysed (easily broken off by enzyme action).

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39
Q

What type of molecule is starch due to it being made of amylose and amylopectin?

A

A composite molecule.

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40
Q

How is glycogen stored?
Where?
What are its properties?

A

Granules.
Liver and muscle cells in mammals.
Compact, insoluble, no unbranched chains, shorter chains than amylopectin + more terminal glucoses enabling faster hydrolysis.

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41
Q

What do B1,4 glycosidic bonds make glucose molecules?

A

Alternately heads up + tails up. (Anti parallel?)

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42
Q

In cellulose, what do the links between glucose molecules give in terms of chain shape?
How are the adjacent chains linked?
How are cellulose molecules grouped together?

A

Straight unbranched cellulose chain.
Hydrogen bonds form cross-linkages.
Form a microfibres by being linked through these hydrogen bonds.

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43
Q

What do plant cell walls consist of? What does this give in terms of properties?

A

Cellulose microfibres orientated in different directions in a lattice structure. High tensile strength.

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44
Q

What are cellulose fibres extracted from plants used for?

A

Cotton. Manufactured into paper, rayon fibres (clothes), nitrocellulose (explosives), cellulose acetate (films/cellophane)

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45
Q

What are Nucleic acids made up of? 2 examples, what do these make up?

A 
Pentose sugars (5 carbon sugars).
Ribose (RNA) + Deoxyribose (DNA)
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46
Q

What are nucleotides made up of?

A

Pentose sugar (ribose/deoxyribose), phosphate group + nitrogenous base (Adenine, guanine, thymine, cytosine, uracil)

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47
Q

What is the difference between ribose + deoxyribose?

A

Ribose has an OH group on its carbon 2 whilst deoxyribose only has a hydrogen.

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48
Q

What are the 2 types of nitrogenous bases?

A

Purines + pyrimidines.

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49
Q

Give examples of purine + pyrimidine bases. (2,3)

A

Adenine + guanine; thymine, uracil + cytosine.

50
Q

How is a nucleotide formed? What are the bonds between phosphate + sugar, sugar and base, and bases.

A

Condensation reactions. Phosphodiester bond, glycosidic bond + hydrogen bond.

51
Q

What do joined nucleotides become?

A

Nucleic acids/polynucleotides.

52
Q

What forms the backbone of the polynucleotide. How long could it be?

A

Alternating sugar + phosphate groups. 5 million nucleotides long.

53
Q

What direction do the strands of DNA go in?

A

Anti-parallel so opposite directions.

54
Q

What base pairs are complementary to easy other? What type of bond does each form?
Why are these bonds the way they are?

A

A-T, Double hydrogen bond.
G-C, Triple hydrogen bond.
Keep it the same width. (3 rings width)

55
Q

What shape is the DNA molecule arranged in?

How many base pairs in each turn of this?

A

Double helix.

10.

56
Q

What does histone do?

What is it called when DNA is wound round histone?

A

DNA winds round it to prevent it becoming entangled within the nucleus by coiling it in an organised way.
Nucleosome.

57
Q

What determines the amino acid sequence of a protein/polypeptide?

A

The sequence of DNA.

58
Q

What are the 3 types of RNA?

A

Messenger (mRNA), Transfer (tRNA) + Ribosomal (rRNA)

59
Q

What does RNA do?

A

Uses information from the nucleus in construction of proteins by ribosomes in cytoplasm.

60
Q

What does mRNA do?

A

Carries genetic code from DNA in nucleus into cytoplasm for protein synthesis.

61
Q

What does tRNA do?

A

Carries amino acids to ribosome for protein synthesis. Folded into clover leaf shape. Each tRNA carries a specific amino acid.

62
Q

What does rRNA do?

A

Made in nucleolus + forms over half mass of ribosome.

63
Q

What are the differences between RNA + DNA?

A

DNA is longer, contains deoxyribose rather than ribose, contains T rather than U, double stranded rather than single stranded.

64
Q

What does ATP contain?

A

Adenine with ribose sugar + 3 phosphate groups.

65
Q

When adenine + ribose combine, what do they form?

A

Adenosine.

66
Q

How often is ATP made, why? How is it formed? How much is stored? Where is energy stored in it? How is this energy released.

A

Continuously as it is required + used immediately. Respiration + photosynthesis. Very little. In bonds between phosphate groups. Hydrolysing it.

67
Q

What type of reaction is the hydrolysis of the terminal phosphate group of ATP? How much energy is released? What must be present for this reaction to occur?

A

A highly exergonic reaction. 30 - 33 kJ mol^-1

ATPase.

68
Q

What can adenosine diphosphate be hydrolysed into? How much energy is released? What must be present for this reaction to occur?

A 
Adenosine Monophosphate (AMP). 30 - 33 kJ mol^-1
ATPase.
69
Q

What elements do lipids contain? Which element is in highest proportion?
What type of molecule is a lipid?

A

Carbon, hydrogen + oxygen. More hydrogen than oxygen than in carbohydrates. Large macromolecules, not polymers.

70
Q

Are lipids soluble or insoluble? Are they hydrophobic or hydrophilic? What can they dissolve in?

A

Insoluble. Hydrophobic. Organic solvents (ethanol, propanone + ether)

71
Q

What are the 4 main types of lipids?

A

Triglycerides (fats + oils), phospholipids (cell membranes), waxes + steroids.

72
Q

Where are fats found?
Where are oils found?
What are waxes found?
Where are steroids found?

A

Animals, plants, plant/animal, hormones (sex/growth + cholesterol)

73
Q

What are the main functions of lipids? How much energy do they provide per gram?

A

Storage (chem energy, 38kJ), thermal insulation, protection (organs), waterproofing (external surfaces, reduces water loss), buoyancy (animals adipose tissue under skin) + desert animals oxidise them to water (metabolic water)

74
Q

Where are triglycerides made of? How are they formed? What do they clump into?

A

3 fatty acid molecules combined to glycerol (alcohol) molecule, condensation reaction between fatty acid + glycerol, hydrophobic properties (aggregate) into globules so they seem like macromolecules.

75
Q

What can they be broken into? What do fatty acids in fats/oils have? Why are they hydrophobic?

A

Fatty acids + glycerol, long hydrocarbon chains that contain 16-18 carbon atoms, long hydrocarbon tails.

76
Q

What is the functional group of fatty acids? What does it produce when it ionises? What is the equation for this?

A

-COOH. Hydrogen ions which is the property of an acid. -COOH -> -COO- + H+

77
Q

When the functional group of 3 fatty acids (-COOH) react with 3 functional groups of glycerol (-COH), what do they form? What type of bonds are they?

A

Triglyceride with ester bonds.

78
Q

How are lipids hydrolysed to their components? What enzyme would catalyse this?

A

3 fatty acids + glycerol using 3 molecules of water. Lipid digestion. Lipase.

79
Q

What’s the difference between an unsaturated and a saturated fatty acid in terms of melting temperature?

A

Unsaturated melts at a lower temp because their hydrocarbon tails don’t pack so closely together.

80
Q

In what way is the structure of a triglyceride and a phospholipid different?

A

In a phospholipid, one of the fatty acids is replaced by an ionised phosphate group (PO4^3-)

81
Q

Why are phospholipids important?

A

They determine the structure and function of the cell surface membrane.

82
Q

What happens when phospholipids are mixed with water?

A

Form surface layers + spherical structures called micelles.

83
Q

How is the cell membrane arranged? How does that work?

A

Bilayer. 2 layers of phospholipid molecules which are back to back. Hydrophilic heads point outwards + hydrophobic tails point in. Heads form hydrogen bonds with water molecules.

84
Q

What functions do proteins perform? Give examples.

A

Enzymes (catalyse chem reactions), carrier proteins (transport materials across cell membranes), antibodies (defend against microbes), structural proteins (support cells + tissues), hormones (transmit info), transport proteins (haemoglobin carry o2) + contactile proteins (actin + myosin, muscle contraction)

85
Q

What elements do proteins contain?

A

Carbon, hydrogen, oxygen, nitrogen + (usually) sulfur.

86
Q

What are proteins composed of? What is their basic structure?

A 
Polymers composed of amino acids.
Amino acid (-NH2) at 1 end + carboxyl group (-COOH) at other end. Different R-group (where sulphur might be)
87
Q

How many amino acids are there?

A

20

88
Q

What does protein function depend on?

A

Its shape which is determined by sequence of amino acids in polypeptide chain which is determined by DNA.

89
Q

What do amino acids join to form? Where does the reaction take place? What type of bond is there? What if it is 2 amino acids?

A

Polypeptide chains, amino group + carboxyl group, peptide bond, dipeptide.

90
Q

What are the 2 most common secondary structures of proteins? How are they held together?

A

a-helix (coiled) or B-pleated sheets (parallel/antiparallel)

Hydrogen bonds.

91
Q

How is tertiary structure made permanent?

A

4 types of bond: hydrogen (R groups), ionic (R groups w/charges), disulfide bonds (R groups w/sulphur) + hydrophobic interactions (non-polar/polar)

92
Q

What happens when globular proteins are in solution?

A

Hydrophobic groups point in whilst hydrophilic groups point outwards.

93
Q

What does haemoglobin consist of?

A

4 separate polypeptide chains held together by disulphide bridges. (2 a-polypeptide chains + 2 B-polypeptide chains) with a haem group containing iron in centre.

94
Q

What is haem an example of? What does this make haeomglobin? What does each iron group contain, what does this mean?

A

A non-protein prosthetic group. A conjugated protein. An iron ion, binds with 1 molecule of O2 so it can pick up 4 oxygen molecules.

95
Q

Give examples of fibrous proteins and their uses.

A

Fibrin (blood clotting), collagen (tendons linking muscle to bone) + keratin (hair/horn/nails)

96
Q

What role do globular proteins have? Give 3 examples?

A

Metabolic role. Enzymes, antibodies + hormones. e.g. haemoglobin.

97
Q

Give properties of globular proteins?

A

Compact, helical + roll, into ball, hydrophobic interactions, water-soluble, less stable than fibrous (metabolic role)

98
Q

What type of protein does mucus contain? What does this make it?

A

Globular, has short chain polysaccharides added before secretion, glycoprotein.

99
Q

How can you be infected by a prion?

A

Eating prion-rich food. (Dead animals, urine, saliva, body fluids)

100
Q

Give examples of prion diseases?

A

Scrapie (sheep + goats), Bovine Spongiform Encephalopathy (BSE in cows) + Creutzfeldt-Jacob Disease (CJD in humans)

101
Q

Properties of prions?

A

Can replicate, infectious, incubation period of 5 - 20 years.

102
Q

How does DNA replicate?

A

Semi-conservative replication. It is unzipped by DNA helicase which breaks the hydrogen bonds of the bases which are complementary to each other. The free nucleotides made of phosphate, deoxyribose sugar and a base link with the template strand of the sugar-phosphate backbone by glycosidic bonds and also create the new strand/backbone by using DNA polymerase which catalyses the polymerisation of nucleotides to form this polynucleotide chain in 5’ to 3’ direction. DNA ligase joins up the lagging strand in a similar way but takes it in sections. The places where replication takes place are known as replication forks. It is done in sections so it is faster.

103
Q

What did Meselsohn + Stahl do to prove DNA replication was semi-conservative?

A

E-coli grown in heavy nitrogen, transferred to light/normal nitrogen for 1 gen replication, then sample taken and spun, another gen replication and spun again. Results were 1st mixed heavy + light (centre), then mixed and light (centre and top)

104
Q

What strange properties does water have?

A

Polar, hydrogen bonds, adhesion, cohesion, high specific heat, high freezing point, chemical buffer + density anomality (ice)

105
Q

What is the general formula of a carbohydrate?

A

(CH2O)n

106
Q

What functions might water have?

A

Transport (cohesion/adhesion), chemical reactions (photosynthesis), temp control (buffer), support (Turgidity), movement (nastic) + reproduction (fertilisation).

107
Q

What bonds form a triglyceride?

A

Ester bonds

108
Q

Who first examined DNA’s structure using paper chromatography?
Who figured out how DNA replicated?
Who described the structure of DNA?

A

Erwin Chargaff
Meselsohn + Stahl
Watson + Crick

109
Q

State one way in which the structure of fructose and glucose are different?

A

Fructose has a 5 membered ring and glucose has a 6 membered ring, however, both are hexose sugars.

110
Q

Describe how the structure of a phospholipid differs from that of a triglyceride.

A

Phospholipid has a phosphate-glycerol head which is hydrophilic, whilst its fatty acid tails are hydrophobic. A triglyceride is made of 3 fatty acid molecules combined to glycerol molecule. They are hydrophobic.

111
Q

What is the general formula of disaccharides?

A

C12H22O11

112
Q

What is the function of nitrate?

A

Nitrogen in amino group of amino acids and in organic bases of nucleotides produced in plants.

113
Q

What is the function of sulfate?

A

Sulfur in R group of amino acid cysteine.

114
Q

What is the function of phosphate?

A

Range of important molecules: ATP, nucleotides + phospholipids.

115
Q

What is the function of calcium?

A

In calcium pectate which contributes to middle lamella of plant cell walls, in calcium phosphate in bones of vertebrae animals.

116
Q

What is the function of magnesium?

A

In chlorophyll molecule, magnesium pectate, middle lamella of plant cell walls.

117
Q

What is the function of iron?

A

Haemoglobin molecule.

118
Q

Why would heat sterilisation of surgical instruments not prevent transmission of CJD if they’d previously been used during an operation on an infected patient?

A

Prions are stable and resistant to temperature and radiation.

119
Q

Give a structural difference between normal and disease causing prions.

A

Secondary structure of disease causing form is composed of beta sheets whilst the normal form is composed of helices.

120
Q

Explain the role of the sulphur containing amino acid, cysteine, in formation of tertiary + quaternary structure of insulin. (Ref chain A & B)

A

Forms disulphide bridges between peptides in tertiary structure. In quaternary structure, forms bonds between chain A + B. Also forms bonds within A chain.

121
Q

Why do animals use glycogen + lipids as energy stores?

A

Lipids for backup store, glycogen gives fast release energy as it is hydrolysed more easily. Animals move so can’t be too heavy.

CCEA AS Biology Unit 1 (14 decks)

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