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OCR A Level Biology A > 2.1.2 Biological Molecules > Flashcards

2.1.2 Biological Molecules Flashcards

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1
Q

why are polysaccharides less soluble in water

A
  • because of compact size
  • because regions that could hydrogen-bond with water are hidden away inside the molecule due to the coiled structure
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2
Q

nutrients ingested are broken down by …

A

digestion

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3
Q

what are catabolic reactions

A
  • breaking down monomers so you can absorb them
    (energy is released)
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4
Q

what are anabolic reactions

A
  • building up molecules
    > products of digestion are absorbed into the blood stream and used to build larger molecules
    (energy is used)
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5
Q

what are metabolic reactions

A

balance between your catabolic and anabolic reactions

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6
Q

define metabolism

A

the sum total of all the chemical reactions that take place in the organism (releases heat)

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7
Q

define excretion

A

the removal of metabolic waste materials (sweat, urea, CO2)

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8
Q

name all the required ‘nutrients’ + their roles in the human body

A
  • Carbohydrates
  • Proteins
  • Lipids
  • Vitamins and Minerals
  • Nucleic Acids
  • Water
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9
Q

what is the role of carbohydrates in the body

A
  • insulin
  • keeps you full / primary source of energy
  • glucose = quick release
  • glycogen = long term storage
  • structure in some organisms
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10
Q

what is the role of proteins in the body

A
  • cell growth
  • enzymes
  • muscles (movement)
  • membranes
  • antibodies
  • most hormones made
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11
Q

what is the role of lipids in the body

A
  • protect your cells
  • insulation (thermal + electrical - myelin sheath)
  • energy
  • some hormones
  • protective layer
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12
Q

what is the role of vitamins and minerals in the body

A
  • iron - haemoglobin
  • take part in metabolic reactions
  • form parts of larger molecules
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13
Q

what is the function of water in the body

A
  • keeps cells hydrated
  • important for cooling + excretion
  • blood + body + brain is mostly water
  • solvent for most metabolic reactions
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14
Q

how many bonds do each of the following make:
C
N
O
H

A

C = 4
N = 3
O = 2
H = 1

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15
Q

what molecules are carbohydrates made up of

A

C, H, O

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16
Q

what molecules are lipids made up of

A

C, H, O (P)

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17
Q

what molecules are proteins made up of

A

C, H, O, N (S)

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18
Q

what molecules are nucleic acids made up of

A

C, H, O, N, P

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19
Q

what are monosaccharides

A
  • Cn (H2O)n
  • monosaccharides are the simple sugar monomer units of carbohydrates
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20
Q

what are the variations in monosaccharides

A
  • triose (3)
  • pentose (5)
  • hexose (6)
    > the different monosaccharides have different number of carbon atoms each (corresponding to their name/number)
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21
Q

name the properties of all monosaccharides

A
  • they are sugars so taste sweet
  • soluble in water
  • insoluble in non-polar solvents
  • form crystals
  • they are all reducing sugars which means they will test positive for Benedicts solution and turn from blue to brick red
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22
Q

what type of monosaccharide is glucose

A

a hexose monosaccharide (6 carbon atoms)

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23
Q

what do glucose molecules contain plenty of

A
  • many bonds that can be broken down during respiration to release energy
  • energy used to make ATP
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24
Q

what are isomers

A
  • molecules with the same formula, but whose atoms are arranged differently in space
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25
Q

what are the 2 types of glucose

A
  • alpha or Beta
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26
Q

what determines if a molecule is an alpha or beta glucose

A
  • the orientation of the OH (hydroxyl group) on Carbon 1
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27
Q

how can you tell if a glucose molecule is alpha

A
  • hydroxyl (OH) found below C1
  • Alpha Below
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28
Q

how can you tell if a glucose molecule is beta

A
  • hydroxyl (OH) found above C1
  • Beta Above
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29
Q

what is the acronym for differentiating between alpha and beta glucose

A
  • ABBA
  • Alpha Below
  • Beta Above
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30
Q

what is the significance of a and B glucose

A
  • slight structural difference can lead to very different molecular properties
  • animals + plants have enzymes that break down a glucose only because of the shape
  • B glucose can therefore not be respires + used for energy
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31
Q

why are glucose molecules polar + soluble in water

A
  • because of the hydrogen bonds that form between hydroxyl groups and water molecules
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32
Q

why is the solubility of glucose important

A
  • so it can be dissolved in the cytosol of the cell
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33
Q

what is cytosol

A
  • fluid contained in cytoplasm
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34
Q

what is is the test for reducing sugars + how does it work

A
  • Benedicts reagent
  • the reducing sugar reduces the Cu2+ ions in the blue copper sulphate to Cu+ forming a brick red precipitate
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35
Q

why is the test for reducing sugars semi quantitative

A
  • because the colour of the solution can tell you the quantities of reducing sugar
  • green, yellow, orange, brick red
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36
Q

in polymerisation (condensation reactions) what happens to monomer / polymers

A
  • monomers are joined together to form a polymer
  • water molecule is eliminated
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37
Q

is polymerisation anabolic or catabolic

A

anabolic

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38
Q

what happens during condensation reactions

A
  • a water molecule is released
  • a covalent bond is formed
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39
Q

in hydrolysis what happens to monomers / polymers

A
  • polymers are split into monomers
  • water molecule is formed
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40
Q

is hydrolysis anabolic or catabolic

A

catabolic

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41
Q

what happens during hydrolysis

A
  • a water molecule is formed
  • a covalent bond is broken
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42
Q

what happens when monosaccharides join together + what is produced

A
  • a new covalent bond is formed called a glycosidic bond + water is produced
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43
Q

what are disaccharides

A
  • a sugar formed when two monosaccharides are joined by glycosidic linkage
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44
Q

what does the water provide in a hydrolysis reaction

A
  • the water provides the hydroxyl group (OH-) and hydrogen (H+) which help the glycosidic bond to break
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45
Q

a glucose + a fructose =

A

sucrose

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46
Q

a glucose + a glucose =

A

maltose

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47
Q

b galactose + a glucose =

A

lactose

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48
Q

which main disaccharide is not a reducing sugar

A

sucrose

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49
Q

state the molecular formula + type of sugar + role in body of: a Glucose

A
  • C6H12O6
  • hexose
  • energy source, component of starch + glycogen which acts as energy stores
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50
Q

state the molecular formula + type of sugar + role in body of: b Glucose

A
  • C6H12O6
  • hexose
  • energy source, component of cellulose which provides structural support in plant cell walls
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51
Q

state the molecular formula + type of sugar + role in body of: Deoxyribose

A
  • C5H10O5
  • pentose
  • component of deoxyribonucleic acid (DNA)
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52
Q

state the molecular formula + type of sugar + role in body of: Ribose

A
  • C5H10O5
  • pentose
  • component of ribonucleic acid (RNA), ATP and NAD
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53
Q

how can non reducing sugars test positive for benedicts

A
  • first must be hydrolysed with acid into its consistent monosaccharides which are reducing sugars so then will test positive
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54
Q

describe the structure of water

A
  • water is made up of 2 hydrogen bonds which are covalently bonded to one oxygen atom
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55
Q

why is water described as a polar molecule

A
  • there’s an unequal sharing of electrons causing oxygen to become slightly negative and hydrogen atoms become slightly positive
  • water is polar molecule due to the unevenly distributed charge
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56
Q

how do polar molecules interact with each other and what do they form

A
  • they interact as the positive and negative regions of the molecules attract each other and form bonds called hydrogen bonds
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57
Q

describe qualities of hydrogen bonds

A
  • hydrogen bonds are relatively weak so they break and reform easily giving water its characteristic
    > but collectively hydrogen bonds provide strength and structure
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58
Q

name some properties of water

A
  • being liquid
  • density
  • acts as a solvent
  • acts as a transport medium
  • coolant
  • provides habitat
  • high specific heat capacity + high latent heat of vaporisation
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59
Q

what helps water to flow

A
  • water molecules constantly move around and as they do the hydrogen bonds are continuously being broken and built up allowing water to flow
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60
Q

water has a … viscosity meaning it can …

A
  • low viscosity, meaning it can flow easily
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61
Q

due to water being liquid at room temp what can it do

A
  • provide habitats for living things (rivers, seas, lakes)
  • form large part of tissues in living organisms
  • provide reaction medium for chemical reactions
  • provide a transport medium
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62
Q

what’s an advantage of water being dense

A
  • aquatic organisms can float easily
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63
Q

what’s advantages of ice being denser than water + floating on it

A
  • creates an insulating layer so aquatic organisms can survive in body of water
    > layer also reduces rate of heat loss from body of water
    > aquatic organisms have stable environment in which to live in the water
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64
Q

why is water a great solvent

A
  • water is great solvent as polar (hydrophilic) molecules dissolve easily in water since they are polar
  • the positive and negative parts of water molecules are attracted to oppositely charged parts of the solute
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65
Q

because water is a great solvent what can happen

A
  • molecules and ions can be transported around living things when dissolved in water
  • many reactions happen in cytoplasm of cell which is over 70% water
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66
Q

what is cohesion

A
  • water molecules ‘sticking’ together as hydrogen bonds between molecules pull them together
    > this means when water is transported, molecules stick together
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67
Q

what is adhesion

A
  • adhesion occurs between water molecules and other polar molecules and surfaces
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68
Q

what is capillary action

A
  • the effects of adhesion and cohesion result is water carrying out capillary action
  • capillary action is the process of when water rises up narrow tube against force of gravity
    > cohesion allows water molecules to stick together and adhesion allows the water molecules to adhere to the surface
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69
Q

why does water have a high specific heat capacity and why is it a good feature

A
  • high specific heat capacity due to energy needed to break the hydrogen bonds
    > means water doesn’t heat up or cool easily
  • good property as water acts as a buffer against rapid temperature changes
    > maintaining constant temperatures is important as living organisms need stable temperatures for enzyme controlled reactions + to live
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70
Q

why does water have a high latent heat of vaporisation and why is it a good feature

A
  • high latent heat of vaporisation as large amounts of energy needed for water molecules to evaporate
  • good as living things an cool down and keep their temperature stable
    > e.g. when mammals sweat they become cool as heat is lost through water vapour
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71
Q

what features of water makes it a good habitat

A
  • water buffering temperature provides stable environment for aquatic organisms
  • ice being less dense than water provides surface habitat for animals + keeps water body temp stable
  • has surface tension allowing smaller invertebrates + animals to live on surface
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72
Q

how is surface tension formed on surface of water

A
  • water molecules on surface are hydrogen bonded to molecules beneath and so more attracted
    > this causes surface of water to contract and gives surface of water ability to resist force applied to it
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73
Q

how are polysaccharides formed

A
  • joining 2 molecules of glucose forms disaccharide maltose
  • addition of further glucose molecules produces polysaccharide amylase
  • each new bond is between C1 of one glucose and C4 of the next glucose
    > called a 1-4 glycosidic bond
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74
Q

how are polysaccharides fromed

A
  • by the condensation of many monosaccharides
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75
Q

what is the difference between homopolysaccharides + heteropolysaccharides

A
  • homopolysaccharides = polysaccharides made solely of one kind of monosaccharide
  • heteropolysaccharide = polysaccharides made of more than one monomer
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76
Q

where do plants store energy + as what

A
  • store energy as starch in chloroplasts + membrane bound starch grains
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77
Q

where do humans store energy + as what

A
  • store energy as glycogen in cells of muscles + liver
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78
Q

what are the main polysaccharides

A
  • starch
  • glycogen
  • cellulose
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79
Q

describe starch

A
  • energy storage in plants
  • a glucose forming mixture of straight amylose chains and branched amylopectin
  • starch is a homopolysaccharide as its made of 2 polysaccharides of amylose + amylopectin
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80
Q

describe amylose + how it’s formed + its structure

A
  • main component of starch found in plants
  • formed by a glucose molecules joined by 1-4 glycosidic bonds
  • as chain increases, structure begins to coil up
  • there are hydrogen bonds within the coil holding it together (stabalises)
    > now amylose is slightly soluble
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81
Q

why is amylose slightly soluble

A
  • because the OH groups on outside of cell form H bonds with water
82
Q

describe amylopectin + its structure

A
  • found in starch + made from glucose molecules
  • it’s branched as it contains 1-4 and 1-6 glycosidic bonds
    > the more there are glycosidic bonds the more branched it is
83
Q

what is the enzyme responsible for hydrolysing 1-6 glycosidic linkages

A

glucosidase

84
Q

describe how the iodine test works

A
  • in potassium iodine solution the iodine molecules become trapped in ‘coils’ of amylose and form amylose-iodine complex
    > the formation of this complex changes the colour of iodine from brown to blue/black
85
Q

describe glycogen + its structure

A
  • found in animals
  • made from glucose monomers but has many more branches than starch (has 1- 4 and 1-6 bonds)
  • compact
  • large molecule so doesn’t leave the cell
  • doesn’t change the osmotic potential of cell as it’s largely insoluble
86
Q

why does glycogen have so many branches + usefulness

A
  • this is so there are more ends so it’s easier to hydrolyse glucose units off for energy
    > the enzymes hydrolyse to release glucose
87
Q

key properties of amylopectin + glycogen

A
  • insoluble
  • branched
  • compact
88
Q

list key features of why polysaccharides are good energy stores

A
  • compact
  • hold glucose molecules in chains
  • branched chains
  • less soluble
89
Q

explain why polysaccharides being compact is good

A
  • they don’t occupy large amount of space + occur in dense granules within cell
90
Q

explain why polysaccharides having glucose molecules in chains is good

A
  • so the glucose molecules can be easily snipped off from end of chain by hydrolysis when needed for respiration
    > hydrolysis reactions are always catalysed by enzymes
91
Q

explain why polysaccharides having branched chains is good

A
  • tend to be more compact
  • allows lots of glucose to be snipped off at same time by hydrolysis when lots of energy is required quickly
92
Q

what is the enzyme responsible for hydrolysing 1-4 glycosidic linkages

A

amylase

93
Q

describe cellulose + its structure

A
  • found in plant cell walls
  • made from b glucose monomers, with 1-4 glycosidic bonds
  • H bonds between chains hold structure together
    + give plants structural rigidity
  • every alternate b glucose rotates 180 so it can create a long straight chain
  • strong linear chains form microfibrils
  • structural support + rigidity for plant
94
Q

why are alternate beta glucose molecules turned upside down

A
  • because b glucose molecules can’t join in the same way as a glucose molecules due to the hydroxyl groups being too far from each other to react
  • they rotate so the hydroxyl groups are close to from chains
    > now it’s unable to coil or form branches
95
Q

why is cellulose insoluble

A
  • no free OH groups available to from H bonds with
    > because all the OH are used within to make hydrogen bonds
96
Q

how are microfibrils formed

A
  • cellulose molecules make hydrogen bonds with each other to form microfibrils
97
Q

how are fibres produced + what do they make

A
  • microfibrils join together forming macrofibrils which then combine to produce fibres
  • these strong, insoluble fibres then make cell wall
98
Q

why do microfibrils + macrofibrils have very high tensile strength + why it’s useful

A
  • because of the strength of the glycosidic bonds
  • because of hydrogen bonds between chains
  • useful as it prevents plants cells from bursting when turgid + helps support the plant + protects delicate cell membrane
99
Q

how does macrofibrils contribute to extra strength in cellulose

A
  • macrofibrils run in all direction + criss-cross the wall to create extra support
100
Q

why is it difficult to digest cellulose

A
  • because the glycosidic bonds between glucose molecules are difficult to break
  • most animals don’t even have an enzyme to catalyse the reaction
101
Q

what makes cell wall fully permeable

A
  • there is space between macrofibrils for water + mineral ion uptake
102
Q

what’s the difference between cellulose + chitin

A
  • chitin has acetylamino group (NH.OCCH3) rather than hydroxyl group on C2
  • forms cross-links between long parallel chains of acetylglucosamine
103
Q

what are the basic monomer unit of proteins

A
  • amino acids
104
Q

how is a dipeptide formed

A
  • condensation reactions link amino acids together into a dipeptide by forming a covalent peptide bond and releasing water
  • hydroxyl in carboxylic acid group of one amino acid reacts with a hydrogen in the amine group of another acid
105
Q

how is polypeptide formed

A
  • addition of further amino acids in dipeptide creates polypeptide
106
Q

what are amino acids sometimes known as

A
  • amphoteric because they have both acidic and basic properties
107
Q

describe the structure of amino acid

A
  • carboxyl group (-COOH)
  • variable group - R
  • Hydrogen
  • amine group (-NH2)
  • all amino acids have same basic structure only R group differs
108
Q

what is used to test for proteins + how does it work

A
  • The Biuret test
  • biuret reagent contains copper sulphate + alkaline potassium hydroxide
    > blue ring will first appear if protein is present which when gently shaken will gradually turn the solution a mauve / purple colour
  • test detects presence of peptide bonds
  • relies on reduction of Cu2+ ions to Cu+
    > Cu+ forms a complex with nitrogen component of peptide bond in alkaline solution
109
Q

what does the biuret reagent contain

A
  • copper sulphate + alkaline potassium hydroxide
110
Q

how can plants manufacture all of their amino acids

A
  • using nitrate from the soil + organic molecules made by photosynthesis
111
Q

can animals make all of their amino acids

A
  • they can make some amino acids (non-essential amino acids)
  • the rest they acquire from their diet (essential amino acids)
112
Q

why can’t animals store excess amino acids

A
  • because the amino group makes them toxic
113
Q

what happens to excess amino acids in animals

A
  • they get transported to the liver where the amino group is removed (deamination) and converted to urea and excreted in urine via the kidney
114
Q

what is deamination

A

process in which excess amino groups are removed

115
Q

what is left of the amino acid after deamination

A
  • a keto acid (contains carboxyl group + variable group)
    > you can respire the keto acid
116
Q

what is the role of enzymes in protein breakdown

A
  • formation + breakage of peptide bonds in organisms is controlled by enzymes
  • covalent peptide bonds are strong and must be broken down by protease enzymes
117
Q

describe the primary structure in proteins

A
  • primary structure is the sequence of amino acids in a polypeptide
  • it determines the structure and function of the protein
  • the sequence is coded for in the DNA in the nucleus
  • peptide bonds (which are covalent bonds) present
    > structure held by peptide bonds not easily broken down
118
Q

describe the secondary structure in proteins

A
  • chain of amino acids then takes on either of 2 secondary structures:
    > a helix
    > b pleated sheet
  • held by hydrogen bonds easily broken as hydrogen bonds are weak individually
119
Q

describe the tertiary structure in proteins

A
  • secondary structure further coils / folds to form tertiary structure
  • this is held in place by different types of bonds and interactions
  • it determines the 3D shape of the protein and hence its function
120
Q

name the bonds responsible for maintaining tertiary structure

A
  • disulfide bonds
  • ionic bonds
  • hydrogen bonds
  • hydrophobic + hydrophilic interactions
121
Q

describe the disulfide bonds used in tertiary structure of proteins

A
  • aka disulfide bridges
  • covalent bonds
  • strongest of the bonds
  • only form between R-groups containing sulfur atoms
122
Q

describe the ionic bonds used in tertiary structure of proteins

A
  • form between oppositely charged R-groups
  • form between carboxyl and amino groups that are part of R groups
    > ionise into NH3+ and COO- groups
  • positive and negative groups like this are strongly attracted to each other forming ionic bond
  • stronger than hydrogen bonds
123
Q

describe the hydrogen bonds used in tertiary structure of proteins

A
  • form between hydrogen atoms with slight positive charge + other atoms with slight negative charge
  • in amino acids they form in hydroxyl, carboxyl and amino groups
  • weakest of bonds formed
124
Q

describe the hydrophilic + hydrophobic interactions used in tertiary structure of proteins

A
  • weak interactions between polar and non-polar R groups
  • causes twisting of amino acid chain, which changes shape of protein
125
Q

describe the quaternary structure in proteins

A
  • how many polypeptide chains are arranged to make the complete protein molecule
  • results from association of several protein chains / subunits
  • interactions can be between different protein molecules
  • protein subunits can be identical or different
126
Q

describe why haemoglobin protein contains quaternary structure

A
  • made up of 4 subunits
  • 2 alpha chain
  • 2 beta chain
127
Q

how are peptides broken down

A
  • protease enzymes catalyse the reaction of turning peptides into their constituent amino acids
  • hydrolysis reaction takes place which requires using water molecule to break peptide bond
    > reforms the amine and carboxylic acid groups
128
Q

what are the 2 main categories of the tertiary + quaternary structure of proteins

A
  • fibrous
  • globular
129
Q

describe the structure + features of globular proteins

A
  • compact, water soluble + roughly spherical in shape
  • formed when hydrophobic R groups on amino acid are turned inward when folded + hydrophilic groups on outside
  • soluble
130
Q

why are globular proteins soluble + why is it important

A
  • hydrophilic groups on outside protein make it soluble in water as water molecules can easily cluster around + bind to them
  • water solubility important for regulating many processes necessary to life e.g. chemical reactions, immunity, muscle contraction
131
Q

describe the structure + features of fibrous proteins

A
  • formed from long, insoluble molecules
  • have regular, repetitive sequences of amino acids with hydrophobic R groups
    > features enable them to form fibres, which have structural function
  • they are strong + long
  • NOT folded into complex 3D shapes like globular
132
Q

give examples of some globular proteins

A
  • conjugated proteins - haemoglobin
  • insulin
  • enzyme - pepsin
133
Q

describe the structure/properties/functions of conjugated proteins

A
  • globular proteins containing a non-protein component called a prosthetic group
    > proteins without prosthetic = simple protein
  • haem groups are example of prosthetic group + contain iron II
134
Q

describe the structure/properties/functions of haemoglobin

A
  • red, oxygen carrying pigment founds in red blood cells
  • quaternary protein made from 4 polypeptides (2 alpha + 2 beta pleated sheets)
  • each polypeptide contains haem group
135
Q

what polypeptide chains are haemoglobin made of + bonds

A
  • 4 polypeptide chain
  • 2 alpha + 2 beta pleated sheet
136
Q

how can haemoglobin transport oxygen around body

A
  • each of the 4 polypeptide contains haem group which can combine reversibly with oxygen molecule, allowing haemoglobin to transport oxygen
  • oxygen molecule binds to iron in each haem group turning haemoglobin from purple red to bright red colour
137
Q

describe the structure/properties/functions of insulin

A
  • hormone made of 2 polypeptide chains (a helix + b pleated sheet)
  • chains fold into tertiary structure joined by disulfide links
  • soluble as amino acids with hydrophilic R groups on outside of molecule
  • hormone involved in regulation of blood glucose concentration
138
Q

what polypeptide chains is insulin made of + bonds

A
  • 2 polypeptide chains
  • alpha helix + beta pleated sheet
  • disulfide links
139
Q

how does insulin regulate blood glucose concentration

A
  • when glucose levels are too high, insulin binds to glycoprotein receptors on outside of muscle + fat cells to increase their uptake + rate of glucose from blood
140
Q

describe the structure/properties/functions of pepsin

A
  • enzyme that digests protein in stomach
  • made of single polypeptide chain of 327 amino acids
  • but folds into symmetrical tertiary structure held by hydrogen bonds + 2 disulfide bridges
141
Q

why is pepsin so stable in the acidic environment of the stomach

A
  • pepsin has 4 amino acids with basic R groups + 43 amino acids with acidic R groups
  • it’s stable in stomach’s acidic environment as there are fewer basic groups to accept H+ ions, and therefore there’s little effect on enzyme’s structure
142
Q

what polypeptide chains is pepsin made of + bonds

A
  • single polypeptide chain of 327 amino acids
  • hydrogen bonds + 2 disulfide bonds
143
Q

give examples of some fibrous protein

A
  • collagen
  • keratin
  • elastin
144
Q

describe the structure + properties of collagen

A
  • collagen is a connective tissue found in skin, tendons, ligaments, and nervous system
  • many different forms but all made up of 3 polypeptides wound together in a long + strong rope like structure
  • has flexibility
145
Q

describe some functions of collagen to provide mechanical strength

A
  • in artery walls: layer of collagen prevents artery bursting when withstanding high pressure from blood pumped by heart
  • tendons made of collagen + connect muscle to bones, allowing them to pull on bones
  • bones made from collage + reinforced with calcium phosphate, which makes them hard
  • cartilage + connective tissue made from collagen
146
Q

describe the structure + properties of keratin

A
  • keratin has large proportion of the sulfur containing amino acid, cysteine
    > results in many disulfide bridges between its polypeptide chains + alongside hydrogen bonding, the molecule becomes very strong, inflexible and insoluble
  • the degree of disulfide bonds determines the flexibility
    > hair contains fewer bonds making it more flexible than nails which contain more bonds
147
Q

describe some functions of keratin

A
  • found in finger nails, hair, claws etc
  • provides mechanical protection
  • an impermeable barrier to infection + being waterproof
    > prevents entry of water-borne pollutants
148
Q

describe the structure + properties of elastin

A
  • elastin found in elastic fibres
  • elastin is quaternary protein made from many stretchy molecules called tropoelastin
  • cross-linking and coiling make structure of elastin strong + extensible
149
Q

describe some functions of elastin

A
  • found in living things where they need to stretch or adapt to their shape as part of life processes
    > skin can stretch around bones + muscles due to elastin and when pinched/pulled can go back to normal
    > elastin in lungs allows them to inflate + deflate
    > in bladder helps expand to hold urine
    > like collagen, elastin helps blood vessels to stretch + recoil as blood is pumped through them, helping maintain pressure wave of blood as it passes
150
Q

what are lipids

A
  • large complex molecules known as macromolecules, not polymers as they’re made up of different components bonded together
151
Q

what elements do lipids contain

A
  • carbon, hydrogen, and oxygen
152
Q

describe some features of lipids

A
  • non-polar so insoluble
  • make up 5% of organic matter or cell
153
Q

what are the 3 most important lipids in living things

A
  • triglycerides
  • phospholipids
  • steroids
154
Q

describe some functions of lipids

A
  • energy: respiratory substrate
  • thermal insulation: blubber
  • electrical insulation: myelin sheath
  • membranes: phospholipids
  • buoyancy: in large water mammals as fat less dense than water
  • protection: outside + around delicate organs
  • hormones: steroids
  • metabolic water: desert animals
155
Q

how are lipids used as a respiratory substrate

A
  • triglycerides are broken down to release energy
  • you hydrolyse ester bonds and glycerol + fatty acids can be broken down to CO2 + H2O
    > respiration of lipid produces more water than resp of a sugar
156
Q

describe the structure of triglycerides

A
  • made up of combining 1 glycerol + 3 fatty acids
157
Q

what are essential fatty acids

A
  • the fatty acids that can’t be made in our bodies so has to be consumed as we can make many fatty acids in our bodies called non-essential fatty acids
158
Q

describe the structure of glycerol

A
  • an alcohol, so contains free -OH groups
  • there are 3 -OH groups which are important to the structure of triglycerides
  • glycerol has 3 Carbon atoms
159
Q

describe the structure of fatty acids

A
  • have an acidic carboxyl group (-COOH) on one end attached to a hydrocarbon tail made of carbon + hydrogen atoms only
  • can contain anywhere from 2-20 carbons
  • the tail determines properties such as insolubility as they’re hydrophobic
160
Q

why are fatty acids acidic

A
  • carboxyl group ionises into H+ and a -COO- group
    > so fatty acids are acidic because it can produce free H+ ions
161
Q

what is the difference between a saturated and unsaturated fatty acid

A
  • saturated contains no C=C bonds
  • unsaturated contains C==C bonds
    > meaning fewer hydrogen atoms can be bonded to a molecule
162
Q

how does unsaturated fatty acid affect structure

A
  • changes shape of hydrocarbon chain giving it a kink (bend), where double bond is
    > kinks push molecules slightly apart making them more fluid
    > more unsaturated fatty acids, the lower melting point as structure is more fluid
163
Q

where does the condensation reaction take place in triglyceride formation + what is produced

A
  • between the -COOH group of fatty acid and -OH group of glycerol
    > because there are 3 -OH groups, three fatty acids will bond
  • water molecule is produced
164
Q

what is the bond known as in a triglyceride formation

A
  • the covalent bond is known as an ester bond
165
Q

describe how you can test for a lipid

A
  • mix sample with ethanol (dissolves the lipid)
  • shake well
  • pour into tube filled with water
  • if lipid present, a white milky emulsion will form as a layer on top
166
Q

describe the structure of a phospholipid

A
  • 1 glycerol + 2 fatty acids + 1 phosphate group
  • most fatty acids found on phospholipids have even number of carbon atoms (16/18)
167
Q

what elements does phospholipids contain

A
  • phosphorus, carbon, hydrogen, oxygen
168
Q

where does the condensation reaction occur to form phospholipid + what bond is formed

A
  • between OH group on phosphoric acid molecule (H3PO4) and one of the three -OH groups on glycerol
  • forms ester bond
169
Q

are phosphate ions in phospholipids soluble or insoluble

A
  • soluble
  • PO4 3-
    > have extra electrons so making the more soluble in water
170
Q

describe a phospholipids behaviour in water

A
  • have charged end (hydrophilic phosphate head) and non-polar end (hydrophilic fatty acids)
  • hydrophobic tails repel water and hydrophilic head attracts water
  • phospholipids can form a layer on surface of water with heads in water + tails sticking out
    > because of this they’re called surface active agents or surfactants
    > can also form micelles - tiny balls with tails tucked inside + heads pointing out
171
Q

describe the structure of a phospholipid bilayer

A
  • phospholipids for bilayers with 2 rows of phospholipids, hydrophobic tails facing inwards and hydrophilic heads pointing outwards
172
Q

why are phospholipids excellent at forming membranes

A
  • because inside + outside of the cell membrane is aqueous solution
173
Q

how does phospholipids give membrane stability

A
  • individual phospholipids are free to move around in the layer but won’t move into any position where there hydrophobic tails are exposed to water
174
Q

give a feature of the phospholipid membrane

A
  • membrane is selectively permeable allowing small + non-polar molecules to move through tails in bilayer
    > lets membrane control what enters/leaves cell + keeps it functioning properly
175
Q

describe structure + function of glycolipids

A
  • made of carbohydrates attached to lipids
    > carbohydrate forms polar head to molecule
  • important in maintaining cell stability in cells by attracting to water molecules (hydrogen)
  • acts as receptor molecule
176
Q

describe what sterols are + function

A
  • sterols aka steroid alcohols are another type of lipid
  • not made from glycerol or fatty acids
  • sterols consist of 4 carbon based rings with hydroxyl (OH) group at one end
    > they’re complex alcohol molecules
177
Q

are sterols hydrophilic or hydrophobic

A
  • hydroxyl group is hydrophilic + polar
  • rest of molecule is hydrophobic
178
Q

describe what cholesterol is + function

A
  • small hydrophobic molecule manufactured primarily in liver + intestines
  • can sist in middle part of bilayer
  • regulates fluidity of membrane, preventing from becoming too fluid at high temps
179
Q

what are plants derivative of cholesterol in cell membranes

A
  • stigmasterol
    > only difference is that it had double bond between Carbon 22 + C23
180
Q

what are some things that made from cholesterol

A
  • steroid hormones:
    > testosterone
    > oestrogen
  • vitamin D
181
Q

steroids being abundant in plants means

A
  • on ingestion and absorption some steroids can be converted into plant hormones
182
Q

where is cholesterol not founded in

A
  • prokaryotic membrane
183
Q

what are inorganic ions

A
  • essential constituents of skeletal structure, involved in maintenance of osmotic pressure and are structural constituents of soft tissue
184
Q

what are inorganic ions important for

A
  • nerve impulse transmission
  • muscle contraction
  • playing vital role in maintaining pH balance of body
  • serve as essential components + activators of enzymes, vitamins and hormones
185
Q

name the cations (incl symbol)

A
  • calcium: Ca2+
  • sodium: Na+
  • potassium: K+
  • hydrogen: H+
  • ammonium: NH4+
186
Q

name the anions (incl symbol)

A
  • nitrate: NO3-
  • hydrogen carbonate: HCO3-
  • chloride: Cl-
  • phosphate: PO4 3-
  • hydroxide: OH-
187
Q

name the function of calcium and what it’s necessary for

A
  • increases rigidity of bone, teeth, cartilage + component of exoskeleton of crustaceans
  • important in clotting blood + muscle contraction
  • activator for several enzymes
  • stimulates muscle contraction + regulates transmission of nerve impulses
  • regulates permeability of cell membranes
  • important for cell wall development in plants + formation of lamella between cell walls
188
Q

name the function of sodium and what it’s necessary for

A
  • involved in regulation of osmotic pressure, control of water levels in body fluid + maintenance of pH
  • affects absorption of carbohydrates in intestines + water in kidney
  • nerve impulse + muscle contraction
  • constituent of vacuole in plants to help maintain turgidity
189
Q

name the function of potassium and what it’s necessary for

A
  • involved in control of water levels in body fluid + maintenance of pH
  • assists active transport of materials across cell membrane
  • involved in synthesis of glycogen + protein and breakdown of glucose
  • generates healthy leaves + flowers in flowering plants
  • contributes to nerve impulse transmission + muscle contraction
  • stomal opening
190
Q

name the function of hydrogen and what it’s necessary for

A
  • involved in photosynthesis + respiration
  • involved in transport of oxygen + CO2 in blood
  • involved in regulation of blood pH
  • catalysis of reactions
191
Q

name the function of ammonium and what it’s necessary for

A
  • component of amino acids, proteins, vitamins, chlorophyll
  • some hormones made of proteins
  • essential component of nucleic acid
  • involved in maintenance of pH in human body
  • component of nitrogen cycle
  • production of nitrate ions by bacteria
192
Q

name the function of nitrate and what it’s necessary for

A
  • component of amino acids, protein, vitamins, chlorophyll
  • essential component of nucleic acids
  • some hormones made of proteins, which contain nitrogen
  • component of nitrogen cycle
  • nitrogen supply to plants for amino acid + protein formation
193
Q

name the function of hydrogen carbonate and what it’s necessary for

A
  • involved in regulation of blood pH
  • involved in transport of CO2 in + out of blood
194
Q

name the function of chloride and what it’s necessary for

A
  • helps in production of urine in kidney + maintaining water balance
  • involved in transport of CO2 in + out of blood
  • regulates affinity of haemoglobin to oxygen through allosteric effects on haemoglobin molecule
  • involved in regulation of blood pH
  • used to produce hydrochloric acid in stomach
  • balance positive charge of sodium + potassium ions in cells
195
Q

name the function of phosphate and what it’s necessary for

A
  • increase rigidity of bone, teeth, cartilage, + component of exoskeleton of crustaceans
  • component of phospholipids, ATP, nucleic acids + several important enzymes
  • involved in regulation of blood pH
  • helps root growth in plants
  • cell membrane formation + bone + nucleic acid + ATP
196
Q

name the function of hydroxide and what it’s necessary for

A
  • regulation of blood pH
  • catalysis of reactions
197
Q

What is used to test for starch + results

A
  • iodine solution (must say solution!)
  • brown —-> blue - black
198
Q

What is used to test for reducing sugars + results

A
  • Benedict’s Reagent (+ heat)
  • blue —-> brick - red precipitate
  • results can be green (low conc) + yellow (med conc)
  • blue because contains Cu (II) ions that reg reduced to Cu
199
Q

What is used to test for non-reducing sugars

A
  • Boil with HCl (acid)
  • Benedict’s reagent
  • blue —-> brick - red precipitate
200
Q

What is used to test for proteins + results

A
  • Biuret’s solution
  • blue —-> purple

OCR A Level Biology A (6 decks)

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