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A level biology > 1. biological molecules P1 > Flashcards

1. biological molecules P1 Flashcards

1
Q

define monomer. give some examples

A

smaller units that join together to form larger molecules

monosaccharides (glucose, fructose, lactose)
amino acids
nucleotides

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2
Q

define polymer. give some examples.

A

molecules formed when many monomers join together.

polysaccharides
proteins
DNA/RNA

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3
Q

what happens in a condensation reaction?

A

a chemical bond forms between 2 molecules and a molecule of water is produced

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4
Q

what happens in a hydrolysis reaction?

A

a water molecule is used to break a chemical bond between 2 molecules.

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5
Q

name 3 hexose monosaccharides

A

glucose
fructose
galactose

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6
Q

name the type of bond when monosaccharides react

A

glycosidic

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7
Q

name 3 disaccharides. describe how they form.

A

maltose: glucose and glucose
sucrose: glucose and fructose
lactose: glucose and galactose

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8
Q

describe and explain 2 features of starch that make it a good storage molecule

A

insoluble in water, so doesn’t affect water potential

branched, so makes molecule compact

large molecule so cannot leave cell

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9
Q

describe how the structure of glycogen is related to its function [4]

A
  • coiled, so compact
  • branched, so more ends for faster hydrolysis
  • insoluble, so doesn’t effect water potential
  • polymer of glucose so is easily hydrolysed
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10
Q

suggest how glycogen acts as a source of energy

A

hydrolysed to glucose and glucose is used in respiration

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11
Q

explain how cellulose molecules are adapted for their function in plant cells

A

long and straight chains
become linked together by many hydrogen bonds to form microfibrils
provides strength to cell wall

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12
Q

describe how a triglyceride molecule is formed

A

one glycerol and 3 fatty acids
condensation reactions and the removal of 3 molecules of water
ester bonds are formed

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13
Q

describe how ester bonds are formed in a phospholipid molecule

A

condensation reaction between glycerol and fatty acid

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14
Q

describe a biochemical test to show that a solution contains a non-reducing sugar

A

heat with HCl and neutralise
heat with benedict’s solution.
positive result - red precipitate

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15
Q

describe how you would test for the presence of a lipid in a liquid sample of food

A

add ethanol and shake, then pour into water
milky emulsion

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16
Q

describe the benedict’s test for reducing sugars

A

add benedict’s reagent to sample, heat
positive result: blue —> brick red

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17
Q

contrast saturated and unsaturated fatty acids

A

saturated contain only single bonds, unsaturated contain C=C double bonds

saturated - straight chain, unsaturated- kinked molecules

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18
Q

how can you compare the amount of reducing sugar in different solutions?

A

the higher the concentration of reducing sugar the further the colour change goes.

or

filter solution and weigh the precipitate

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19
Q

what are isomers?

A

molecules with the same molecular formula, but the atoms are connected in a different way

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20
Q

what a polysaccharide?

A

more than 2 monosaccharides joined together by condensation reactions

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21
Q

describe the structure of amylose

A

long unbranded chain of a-glucose

coiled structure which makes it compact so good for storage

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22
Q

describe the structure of amylopectin

A

long branched chain of a-glucose

side branches allow enzymes that break down the molecule to get to the glycosidic bonds easily so glucose is released quickly

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23
Q

describe the test for starch

A

add iodine dissolved in potassium iodide solution

orange —>blue/black

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24
Q

describe the structure of a fatty acid

A

long hydrocarbon tails which are hydrophobic and so insoluble in water

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25
relate the structure of triglycerides to their function
high energy: mass ratio (lots of energy can be stored without restricting the movement of animals) insoluble hydrocarbon chain - can store lots of energy with no effect on water potential.
26
describe how a phospholipid is formed
one glycerol, 2 fatty acids and a phosphate group combine creating ester bonds in a condensation reaction
27
relate the structure of phospholipids to their function
forms a bilayer (hydrophilic head, hydrophobic tail) membrane acts as a barrier to water soluble substances
28
describe how amino acids form so there’s always NH2 at one end and COOH at the other
one NH2 group joins to a COOH group to form a peptide bond, this means that there’s a free NH2 group at one end and a free COOH at the other on the polypeptide chain
29
describe 2 ways in which all dipeptides are similar and one way they might differ
all consist of 2 amino acids joined by a peptide bond all have an amine/ NH2 group at one end all have carboxyl/COOH group at one end all contain C,H,N and O
30
describe how a peptide bond is formed between 2 amino acids to form a dipeptide
condensation reaction between amine group and carboxyl group
31
what’s the primary structure of a protein?
sequence of amino acids in polypeptide chain
32
describe the secondary structure of a protein
hydrogen bonds form between the amino acids in the chain, making it coil into an alpha helix or fold into a beta pleated sheet.
33
describe the tertiary structure of a protein
the secondary structure is coiled and folded more to form the final 3D structure. more bonds, including hydrogen bonds, ionic and disulphide bridges form between different parts of the polypeptide chain.
34
describe the quaternary structure of a protein
more than one polypeptide chain, e.g. haemoglobin, collagen, insulin.
35
explain the importance of the primary structure in proteins
if even one amino acid in the sequence was different, then it will cause the hydrogen/ ionic/ disulphide bonds to form in a different location, resulting in a different tertiary structure.
36
two proteins have the same number and type of amino acids but different tertiary structures. explain why
different sequence of amino acids, so forms ionic/ hydrogen/ disulphide bonds in different places
37
explain how to test for proteins
add biuret solution to sample blue —> purple
38
explain how enzyme properties relate to their tertiary structure
enzymes are very specific and usually catalyse only one reaction. this is as only one complementary substrate will fit into the active site, which is determined by the enzymes tertiary structure. so if there’s a different shaped active site, no enzyme substrate complex and so the reaction won’t be catalysed
39
how do enzymes help reactions proceed quickly at lower temperatures?
lowers the activation energy
40
the secondary structure of a polypeptide is produced by bonds between amino acids. describe how
hydrogen bonds forming beta pleated sheets or alpha helix
41
formation of an enzyme-substrate complex increases the rate of reaction. explain how
reduces activation energy, without enzyme very few substrates have sufficient energy for reaction
42
describe the induced fit model of enzyme action. and how an enzyme acts as a catalyst
substrate binds to active site, active site changes shape so its complementary to substrate reduces activation energy
43
explain how the active site of an enzyme causes a high rate of reaction
lowers activation energy induced fit causes active site of enzyme to change shape - so enzyme substrate complex causes bonds to form/break
44
explain 5 properties that make water important for organisms
a metabolite in condensation/hydrolysis a solvent, so metabolic reactions can occur high specific heat capacity, so buffers changes in temperature large latent heat of vaporisation, so provides a cooling effect through evaporation cohesion between water molecules so supports columns of water in plants OR so produces surface tension supporting small organisms.
45
state and explain the property of water that helps to prevent temperature increase in a cell
high specific heat capacity, buffers changes in temperature
46
give 2 properties of water that are important in the cytoplasm of cells, and explain it’s importance in the cytoplasm
reactive, takes place in hydrolysis/condensation reactions polar molecule, acts as a universal solvent
47
describe the structure of DNA
a polymer of nucleotides each nucleotide is formed from deoxyribose, a phosphate group and an organic nitrogenous base phosphodiester bonds between nucleotides double helix hydrogen bonds between adenine, thymine and guanine, cytosine
48
describe how a phosphodiester bond is formed between 2 nucleotides within a DNA molecule
condensation reaction between phosphate group and deoxyribose
49
which bases are purine and which are pyrimidine
A+G - purine C+T+U - pyrimidine
50
describe the role of DNA polymerase in the semi-conservative replication of DNA
joins adjacent DNA nucleotides as it catalyses the formation of phosphodiester bonds between adjacent DNA nucleotides
51
describe the process of semi conservative DNA replication [5]
- DNA helicase breaks hydrogen bonds between base pairs (DNA unwinds) - each strand acts as a template - free DNA nucleotides attach to exposed bases via complementary base pairing. - DNA polymerase joins adjacent nucleotides on new strand - forming phosphodiester bonds - each new DNA molecule consist of one template strands and one new strand
52
give 2 features of DNA and explain how each one is important in the semi-conservative replication of DNA.
two strands, so both can act as templates easily broken hydrogen bonds between bases allow 2 strands to separate or complementary base pairing allows accurate replication.
53
describe how an ATP molecule is formed
adenine, ribose and three phosphates join via condensation reaction using ATP synthase
54
contrast the structures of ATP and a nucleotide found in DNA to give 2 differences
ATP has ribose and DNA has deoxyribose ATP has 3 phosphate groups and DNA has one phosphate group ATP - base always adenine. DNA - nucleotide base varies
55
give 2 ways in which ATP is a suitable energy source for cells to use
- releases relatively small and manageable amounts of energy (so little energy lost as heat) - phosphorylates other compounds, making them more reactive - can be rapidly re-synthesised
56
explain why new nucleotides can only be added in a 5’ to 3’ direction
DNA polymerase is specific so is only complementary with the 5’ end of strand. shapes of 5’ end and 3’ and are different.
57
describe how ATP is resynthesised in cells
from ADP and phosphate by ATP synthase during respiration/photosynthesis
58
give 2 ways in which the hydrolysis of ATP is used in cells
to phosphorylate other substances to make them more reative to provide energy for other reactions
59
give 2 ways in which the hydrolysis of ATP is used in cells
to phosphorylate other substances to make them more reative to provide energy for other reactions
60
use your knowledge of water potential to suggest how high sodium concentrations in the medicines taken could affect blood volume
sodium ions lower the water potential of blood water would move into the blood by osmosis from cells/ tissue fluid increasing the blood volume
61
explain the role of hydrogen ions in the body
high concentration of H+ = low PH interact with H-bonds and ionic bonds in tertiary structure of proteins which can cause them to denature
62
explain the role of iron ions in the body
forms haem group in haemoglobin haem group has binding site to oxygen (transports it around body)
63
explain the role of sodium ions in the body
co-transport of glucose and amino acids in lumen of gut - sodium moved out my active transport, which creates a sodium concentration gradient.
64
explain the role of phosphate ions in the body
used to produce ATP and DNA phosphorylates other compounds making them more reactive the hydrophilic part of membrane/ phospholipid bilayer
65
explain the role of phosphate ions in the body
used to produce ATP and DNA phosphorylates other compounds making them more reactive the hydrophilic part of membrane/ phospholipid bilayer
66
describe the role of iron ions, sodium ions and phosphate ions in cells
iron ions: forms haem group, which binds to oxygen (haemoglobin binds to oxygen) sodium ions: co-transport of glucose/ amino acids because sodium moved out by active transport, which creates a sodium concentration gradient phosphate ions: used to produce ATP and DNA phosphorylates other compounds making them more reactive phospholipid bilayer
67
why does the rate of an enzyme controlled reaction increase when the temperature is increased
- more heat means more kinetic energy, so molecules move/ vibrate faster. this makes the enzymes more likely to collide with the substrate molecules. - the energy of these collisions also increases, meaning each collision is more likely to result in a reaction.
68
what happens when the temperature gets too high in enzyme controlled reactions?
the reaction stops: - the rise in temperature makes the enzyme molecules vibrate more, if the temperature goes above a certain level, this vibration breaks some of the bonds that holds the enzyme in shape. - the active site then changes shape and the enzyme and substrate no longer fit together (denatured)
69
why does an enzyme get denatured above and below its optimum PH?
above and below the optimum ph, the H+ and OH- ions can mess up the ionic and hydrogen bonds that hold the enzymes tertiary structure in place. this make the active site change shape, so the enzyme is denatured
70
how does substrate concentration effect the rate of reaction?
the higher the substrate concentration, the faster the reaction. a higher concentration means a collision between substrate and enzyme is more likely do more active sites will be used. - this is only true up to a ‘saturation’ point. after that, there are so many substrate molecules, the enzymes struggle to cope, so adding more makes no difference.
71
what’s a competitive inhibitor?
similar shape to substrate (binds to enzyme instead) no ES complexes
72
what’s a non competitive inhibitor?
binds to enzyme away from active site (changes shape) no ES complexes
73
in competitive inhibition, how much the enzyme is inhibited depends on what?
the relative concentrations of the inhibitor and the substrate. if there’s a high concentration of the inhibitor, it’ll take up nearly all the active site, so hardly any of the substate will get to the enzyme.
74
how many hydrogen bonds are between A and T?
2
75
how many hydrogen bonds are between G and C
3
76
what is the role of the disulphide bridge in forming the quaternary structure of an antibody?
joins 2 different polypeptides

A level biology (9 decks)

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