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A - Biology > Topic 1A - Biological molecules ARN * > Flashcards

Topic 1A - Biological molecules ARN * Flashcards

carbohydrates lipids proteins factors affecting enzyme action enzyme-controlled reactions

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1
Q

what are polymers?

A

large, complex molecules made of long chains of monomers joined together

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2
Q

what are monomers?

A

small, basic molecular units

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3
Q

what are some examples of types of monomers?

A

monosaccharides, amino acids and nucleotides

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4
Q

what elements do all carbohydrates contain?

A

carbon, hydrogen and oxygen

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5
Q

what monomers are carbohydrates made from?

A

glucose, fructose and galactose, they are all monosaccharides

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6
Q

how many carbon atoms are in each molecule of glucose?

A

6, its a hexose sugar

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7
Q

what are the 2 types of glucose?

A

(α) alpha glucose and (β)beta glucose, they are isomers

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8
Q

what are isomers?

A

molecules with the same molecular formula, but their atoms are connected in different ways

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9
Q

what is a condensation reaction?

A

when 2 molecules join together with the formation of a new chemical bond and a water molecule is released

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10
Q

How do monosaccharides join together?

A

they are joined by a condensation reaction to form a glycosidic bond between the 2 and a disaccharide, a water molecule is also released

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11
Q

How is sucrose formed?

A

from a condensation reaction between glucose and fructose

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12
Q

How is lactose formed?

A

from a condensation reaction between glucose and galactose

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13
Q

How is maltose formed?

A

from a condensation reaction between 2 glucose molecules

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14
Q

what are some examples of disaccharides?

A

maltose
sucrose
lactose

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15
Q

what is a hydrolysis reaction?

A

a reaction that breaks the chemical bond between monomers in a polymer using a water molecule

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16
Q

what is the test for sugars?

A

the benedict’s test

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17
Q

what are examples of reducing sugars?

A

all of the monosaccharides, maltose and lactose

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18
Q

what are examples of non-reducing sugars?

A

sucrose

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19
Q

how to carry out test for reducing sugars:

A

add benedict’s reagent to a sample then heat it in a boiling water bath
look for colour change from blue to red (usually)
if positive coloured precipitate will form

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20
Q

How can you tell how much sugar there is from a benedict’s test?

A 
blue- no reducing sugar
green - very low
yellow - low
orange - medium
red - high
or filter and weigh the precipitate produced
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21
Q

how to carry out test for non-reducing sugars?

A

if benedict’s is negative
add dilute HCl to a new sample of the solution and heat in boiling water bath to break down into monosaccharides
neutralise with sodium hydrogencarbonate
do benedict’s again if positive it will form precipitate if not it doesn’t contain any sugar

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22
Q

how are polysaccharides formed?

A

when more than 2 monosaccharides are joined by a condensation reaction

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23
Q

what are examples of polysaccharides?

A

starch
glycogen
cellulose

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24
Q

how do cells get energy?

A

from glucose, plants store excess glucose as starch which is hydrolysed when plants need more glucose

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25
Q

what 2 polysaccharides is starch a mixture of?

A

α-glucose amylose and α-glucose amylopectin

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26
Q

what is the structure of α-glucose amylose?

A

long unbranched chain of α-glucose
the angles of the glycosidic bonds make it coiled so it is compact
insoluble in water
large

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27
Q

what is the structure of α-glucose amylopectin?

A

long, branched chain of α-glucose
insoluble in water
large

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28
Q

what is starch?

A

an energy store found in grains in the cytoplasm, or the chloroplasts

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29
Q

how does starch’s structure aid its function?

A

compact - good for storage (fit more in small space)
branched - easier for enzymes to get at the glycosidic bonds to hydrolyse the molecule for quick release of glucose
insoluble - osmotically inactive
large - can’t diffuse out of the cell

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30
Q

what does osmotically inactive mean?

A

doesn’t affect the water potential of the cell, so water doesn’t enter the cell by osmosis causing it to swell and damaging it

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31
Q

how to test for starch?

A

add iodine dissolved in potassium iodide solution to sample

check for colour change from orange/brown to blue/black

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32
Q

what kind of bonds are formed in making starch?

A

α-1,4 bonds and α-1,6 glycosidic bonds

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33
Q

what is glycogen?

A

energy store in animals in the form of granules in the cytoplasm
polysaccharide made from α-glucose via condensation reaction

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34
Q

what bonds from in glycogen?

A

α 1,4 and many α 1,6 glycosidic bonds

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35
Q

what is the structure of glycogen?

A

large
highly branched
α-helix shape so compact
insoluble

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36
Q

how does glycogen’s structure aid its function?

A

large- doesn’t diffuse out of the cell
branched- rapid glucose release by enzymes
compact - good for storage
insoluble - osmotically inactive

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37
Q

what is cellulose?

A

structural polysaccharide, made from β-glucose joined via condensation reactions

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38
Q

what bonds does cellulose contain?

A

β-1,4 glycosidic bonds
every other β-glucose is inverted
hydrogen bonds form between parallel cellulose chains

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39
Q

what is the structure of cellulose?

A

long, straight, unbranched chains of β-glucose

chains line up and are linked by hydrogen bond cross-links

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40
Q

how does cellulose’s structure aid its function?

A

hydrogen bonds link cellulose chains to form microfibrils which can then form fibres which are very strong so they provide structural support for cell walls

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41
Q

what does a reducing sugar do?

A

it is able to lose electrons to give to other molecules (and reduce them)

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42
Q

how does benedict’s reagent help test for reducing sugars?

A

it contains Cu2+ ions as copper (II) sulfate which is blue and reducing sugars reduce them to form Cu+ as copper(I) oxide which is red

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43
Q

what are some examples of lipids?

A

triglycerides

phospholipids

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44
Q

what are triglycerides composed of?

A

1 molecule of glycerol and 3 fatty acids

connected via ester bonds

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45
Q

what are fatty acids?

A

molecules with long ‘tails’ made of hydrocarbons.
these tails are hydrophobic,
this makes lipids insoluble in water

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46
Q

what kind of reaction forms a triglyceride?

A

a condensation reaction between glycerol and 3 fatty acids that connect via ester bonds and 3 water molecules are produced

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47
Q

what are the 2 kinds of fatty acids?

A

saturated

unsaturated

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48
Q

what is a saturated fatty acid like?

A

it has no double bonds between carbons

its saturated with hydrogen

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49
Q

what is an unsaturated fatty acid like?

A

it has at least one carbon-carbon double bond

this causes the chain to kink

50
Q

what lipids are used in cell membranes?

A

phospholipids

51
Q

what are phospholipids composed of?

A

1 glycerol molecule
2 fatty acids
a phosphate group

52
Q

what is the purpose of the phosphate group in a phospholipid?

A

it is hydrophilic

53
Q

what are triglycerides mainly used for?

A

as energy storage molecules
can be fats (solid at room temp)
or oils (liquid at room temp)

54
Q

what is the structure of triglycerides?

A

hydrocarbon tails contain lots of chemical energy (high energy to mass ratio)
they’re insoluble - form droplets which clump together with hydrophobic tails facing inward

55
Q

how does the structure of a triglyceride aid its function?

A

high energy : mass - lots of energy is released when its broken down, don’t have to carry heavy mass around
insoluble - don’t affect water potential of cell and cause water to enter via osmosis and cause it to swell, water proof

56
Q

how much energy do lipids possess in relative to carbohydrates?

A

lipids contain twice as much energy per gram than carbohydrates

57
Q

what are phospholipids used for?

A

they make up the bilayer of cell membranes

58
Q

what is the structure of phospholipids?

A

hydrophilic heads and hydrophobic tails so they are polar, they form a double layer with the heads facing outwards towards water on either side

59
Q

how does the phospholipid bilayer help the cell?

A

the centre is hydrophobic so water soluble substances can’t pass through easily and the bilayer acts as a barrier

60
Q

How to carry out the test for lipids?

A

add ethanol to substance and shake until it dissolves
pour solution into water
lipid will appear as a white emulsion floating on the water

61
Q

what can lipids be used for?

A 
cell membranes
energy store
water proofing
insulation
protection
62
Q

what are the monomers of proteins called?

A

amino acids

63
Q

what are the dimers and polymers of proteins called?

A

dipeptides
polypeptides
proteins are made up of 1 or more polypeptides

64
Q

what functional groups are amino acids made up of?

A

a carboxyl group (COOH)
an amine or amino group(NH2)
an R group

65
Q

how are amino acids bonded together?

A

they are linked by condensation reactions to form polypeptides and a water molecule is released.
the bonds formed are called peptide bonds

66
Q

how many ‘levels’ make up a proteins structure?

A

4

primary, secondary, tertiary and quaternary

67
Q

what is the primary structure of a protein?

A

the sequence of amino acids in the polypeptide chain

68
Q

what is the secondary structure of a protein?

A

hydrogen bonds form between the amino acids in the chain. This makes it automatically coil into an alpha helix or fold into a beta pleated sheet

69
Q

what is the tertiary structure of a protein?

A

coiled or folded chain is coiled or folded further. more bonds form between different parts of the polypeptide chain, including hydrogen and ionic bonds. disulfide bridges also form whenever 2 molecules of cysteine come closer together. for proteins made from a single polypeptide chain, this forms their final 3D structure

70
Q

how do disulfide bridges form between cysteine molecules?

A

when the sulfur atom in one cysteine bonds to the sulfur atom in the other

71
Q

what is the quaternary structure of a protein?

A

proteins made of several different polypeptide chains held together by bonds are assembled here. this is the final 3D structure for these proteins

72
Q

what are some examples of proteins found in living organisms?

A

enzymes
antibodies
transport proteins
structural proteins

73
Q

what are enzymes?

A

roughly spherical in shape due to tight folding of the polypeptide chains. they’re soluble and often have roles in metabolism

74
Q

what are some examples of what enzymes do?

A

some break down large food molecules (digestive enzymes) and other enzymes help to synthesise large molecules

75
Q

what are antibodies?

A

involved in the immune response. they’re made up of 2 light (short) polypeptide chains and 2 heavy (long) polypeptide chains bonded together. antibodies have variable regions - the amino acid sequences in these regions vary greatly

76
Q

what’s an example of a transport protein?

A

e. g. channel proteins are present in cell membranes

e. g. haemoglobin

77
Q

what do channel proteins do?

A

contain hydrophobic and hydrophilic amino acids which cause the protein to fold up and form a channel. these proteins transport molecules and ions across membranes

78
Q

what are structural proteins?

A

physically strong, they consist of long polypeptide chains lying parallel to each other with cross-links between them.

79
Q

what are examples of structural proteins?

A

keratin - found in hair and nails

collagen - found in connective tissue

80
Q

What’s the test for proteins?

A

biuret test

81
Q

how to carry out the biuret test?

A

solution must be alkaline so a few drops of NaOH solution is added
copper(II) sulfate solution added
positive - purple
negative - blue

82
Q

how much of the body is made up of proteins?

A

they make up 20% of the body

83
Q

how many different amino acids are there?

A

20, they all have the same general structure, only the R group changes

84
Q

what is the prosthetic group of a protein?

A

a non-amino acid part of a protein

85
Q

what is a catalyst?

A

a substance that speeds up a chemical reaction without being used up in the reaction itself

86
Q

what do enzymes do?

A

catalyse metabolic reactions - both at a cellular level and for the organism as a whole

87
Q

what things can enzymes affect in an organism?

A

structures- e.g. enzymes involved in the production of collagen
functions - e.g. respiration

88
Q

enzyme action can be:

A

intercellular - within cells

extracellular - outside cells

89
Q

what features does an enzyme have?

A

they have an active site, which has a specific shape. enzymes are highly specific due to their tertiary structure

90
Q

what is an enzymes active site?

A

the part of the enzyme where the substrate molecules bind to

91
Q

what is the activation energy?

A

a certain amount of energy that needs to be supplied to the chemicals before the reaction will start. it’s often provided as heat

92
Q

what do enzymes do to the activation energy?

A

they lower the amount of activation energy needed, so the reactions can happen at a lower temperature, this speeds up the rate of reaction

93
Q

what is an enzyme-substrate complex?

A

when a substrate fits into the enzyme’s active site this is formed. it lowers the activation energy

94
Q

why do enzyme-substrate complexes lower the activation energy?

A
  1. being attached to the enzyme holds the 2 substrate molecules close together, reducing any repulsion between the molecules so they can bond more easily
  2. if the enzyme is catalysing a breakdown reaction, fitting into the active site puts a strain on bonds in the substrate, so the substrate molecule breaks up more easily
95
Q

what is the ‘lock and key’ model?

A

enzymes only work with substrates that it their active site, in this model the substrate fits into the enzyme in the same way a key fits into a lock

96
Q

what is the ‘induced fit’ model?

A

active site changes shape slightly to complete the fit and form an enzyme substrate complex. this locks the substrate even more tightly to the enzyme

97
Q

why is the induced fit model so good?

A

it helps explain why enzymes are so specific and only bond to 1 particular substrate. the substrate has to be the right shape to fit and make the active site change shape in the right way.

98
Q

why do enzymes only usually catalyse 1 reaction?

A

only 1 complementary substrate will fit into the active site

99
Q

what is the shape of the active site determined by?

A

the enzyme’s tertiary structure, (which is determined by the primary structure)
each different enzyme has a different tertiary structure and so different shaped active site

100
Q

what happens to the active site when the tertiary structure of an enzyme is altered?

A

the shape will change, the substrate won’t fit into the active site, an enzyme-substrate won’t be formed and the enzyme will no longer be able to carry out its function

101
Q

what can alter the tertiary structure of an enzyme?

A

changes in pH or temperature

102
Q

how can the primary structure effect the secondary structure?

A

a gene determines the primary structure of a protein, if a mutation occurs in that gene it could change the tertiary structure of the enzyme produced

103
Q

what factors affect enzyme activity?

A

temperature
pH
enzyme concentration
substrate concentration

104
Q

how does temperature affect enzyme activity?

A

as temperature increases rate increases
more kinetic energy so molecules move faster and are more likely to collide with the substrate molecules
higher energy = more likely successful collision
too high = reaction stops

105
Q

why does a reaction stop when the temperature gets too high?

A

enzyme molecules vibrate more
vibration breaks some bonds
active site changes shape, so substrate doesn’t fit
enzyme = denatured

106
Q

how does pH affect enzyme activity?

A

every enzyme has an optimum pH
above and below optimum pH - H+ and OH ions can mess up ionic bonds and hydrogen bonds that hold tertiary structure in place
active site changes shape
enzyme = denatured

107
Q

how does enzyme concentration affect enzyme activity?

A

more enzymes, more likely to collide and form enzyme-substrate complex
so increase in enzymes = increase in rate
only limited by amount of substrate

108
Q

how does substrate concentration affect enzyme activity?

A

higher concentration = faster reaction

more substrate = more likely to collide with enzymes and form enzyme - substrate complex

109
Q

what stops a rate of reaction increasing when substrate increases?

A

saturation point - too many substrates for enzymes to process
substrate is used up in a reaction so if no more is added the rate will begin to decrease

110
Q

how do enzymes work?

A

it works by forming an enzyme-substrate complex which strains bonds, lowering the activation energy, some lower Ea by bringing substrates closer together

111
Q

how can enzyme activity be prevented?

A

by enzyme inhibitors

112
Q

what are the different enzyme inhibitors?

A

competitive inhibitors

non-competitive inhibitors

113
Q

what do competitive inhibitors do?

A

similar shape to the substrate
they bind to the enzymes active site but no reaction takes place
prevents enzyme-substrate complex forming

114
Q

what affects how much an enzyme is inhibited by competitive inhibitors?

A

the relative concentrations of the inhibitor and the substrate
high conc. of inhibitors means hardly any substrate will get to the enzyme
but increasing substrate increases rate of reaction

115
Q

what do non-competitive inhibitors do?

A

they bind to an enzyme away from the active site
changes tertiary structure of active site permanently
no longer complementary
no more enzyme-substrate active sites

116
Q

how to combat non-competitive inhibitors?

A

increasing substrate won’t make any difference, enzyme activity is still inhibited
more enzymes must be added

117
Q

how can the rate of an enzyme-controlled reaction be measured?

A

measuring how fast the product is made

measuring how fast the substrate is broken down

118
Q

what’s an example of how the rate of an enzyme-controlled reaction be measured by measuring how fast the product is made?

A

catalase catalysing the breakdown of hydrogen peroxide into water and oxygen

119
Q

what happens in the breakdown of hydrogen peroxide experiment?

A

set up boiling tubes with the same volume and concentration of hydrogen peroxide and a suitable buffer
put each boiling tube in a water bath set at different temperatures along with a tube containing catalase and wait
add the same volume and concentration of catalase to each tube then quickly attach bung and delivery tube
record how much oxygen is produced in the 1st minute
repeat 3 times for each temperature

120
Q

how should the experiment for the breakdown of hydrogen peroxide be set up?

A

a boiling tube with a delivery tube pointing into an upside down measuring cylinder filled with water in a trough of water.
as oxygen is produced water is pushed out of the cylinder

121
Q

what’s an example of how the rate of an enzyme-controlled reaction be measured by measuring how fast the substrate is broken down?

A

put a drop of iodine in potassium iodide into each well on a spotting tile
mix a known concentration of amylase and starch in a test tube
a pipette should be used to put a drop of the mixture into each well at regular intervals until the indicator stops changing colour, this means no more starch is present
repeat times for each different concentrations of amylase

122
Q

what is the initial rate of reaction?

A

the rate at the start of the reaction, this is when its fastest

A - Biology (21 decks)

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