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Biology A-Level > Topic 1 - Biological Molecules > Flashcards

Topic 1 - Biological Molecules Flashcards

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1
Q

what is a monomer

A

smaller repeating molecules from which larger molecules/polymers are made

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2
Q

what is a polymer

A

molecule made up of many identical/similar molecules/monomers

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3
Q

what happens in a condensation reaction

A

2 molecules join together, forming a chemical bond, releasing a water molecule

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4
Q

wwhat happens in hydrolysis reactions

A

2 molecules separated, breaking a chemical bond using a water molecule

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5
Q

give 3 examples of polymers and the monomers from which they’re made

A

nucleotide - polynucleotide (DNA or RNA)
monosaccharide e.g. glucose - polysaccharide e.g starch
amino acid - polypeptide (protein)

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6
Q

what are monosaccharides

A

monomers from which larger carbohydrates are made

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7
Q

give 3 examples of monosaccharides

A

glucose, fructose, galactose

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8
Q

what is the difference btwn the structure of alpha and beta glucose

A

OH is below carbon-1 in alpha glucose but above carbon- 1 in beta glucose

they are isomers

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9
Q

what are disaccharides

A

2 monosaccharies joined together with a glycosidic bond

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10
Q

list 3 common disaccharides and monosaccharides from which they are made

A

maltose - glucose, glucose
lactose - glucose, galactose
sucrose - glucose, fructose

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11
Q

what are polysaccharides

A

many monosaccharides joined together with glycosidic bonds

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12
Q

describe the basic function of starch

A

energy store in plants

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13
Q

describe the structure of starch

A
  • polysaccharide of alpha glucose
  • amylose has 1-4 glyocisidic bonds, unbranched
  • amylopectin has 1-4 + 1-6 glycosidic bonds, branched
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14
Q

explain how the structures of starch relates to its function

A

helical - compact for storage in cell
large, insoluble plysaccharide molecule - can’t leave cell, cross cell membrane
insoluble in water, water potential of cell isn’t affected

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15
Q

describe the basic function of glycogen

A

energy store in animals

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16
Q

describe the structure of glycogen

A

polysaccharide made of alpha glucose
1-4 + 1-6 glycosidic bonds, branched

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17
Q

explain how the strucutre of glycogen relates to its function

A

branched - compact so can fit more moelcules in a small area, more ends faster for hydrolysis (release glucose for respiration to make ATP for energy relase)
large, insoluble plysaccharide molecule - can’t leave cell, cross cell membrane
insoluble in water, water potential of cell isn’t affected

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18
Q

describe the basic function of cellulose

A

provides strength and structural support to plant/algal cell walls

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19
Q

describe the structure of cellulose

A

polysaccharide of beta glucose
1-4 glycosidic bonds, straight unbranched chains
chains linked in parallel by hydrogen bonds to form microfibrils

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19
Q
A
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20
Q

explain how the structure of cellulose relates to its function

A

every other beta glucose molecule is inverted in a long, striaght, unbrnached chain
many hydyrogen bonds linked in parallel by hydrogen bonds to form microfibrils
hydrogen bonds are strong in high numbers so provides strength to plant cell walls

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21
Q

name 3 reducing sugars

A

monosaccharides, maltose, lactose

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22
Q

describe the test for reducing sugars

A
  • add Benedict’s solution (blue) to sample
  • heat in a boiling water bath
  • positive result = green,yellow,orange, red precipitate
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23
Q

name a non-reducing sugar

A

sucrose

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24
Q

describe the test for non-reducing sugars

A
  • Benedict’s test and stays blue
  • heat in a boiling water bath with acid (hydrolyses into reducing sugars
  • neutralise with alkali e.g. sodium bicarbonate
  • heat in a boiling water bath with Benedict’s solution
  • positive result = green,yellow,orange,red precipitate
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25
Q

suggest a method to measure the quantity of sugar in a solution

A
  • carry out Benedict’s test for non reducing sugars, filter and dry precipitate. weigh to find mass
  • make sugar solutions of known concenttrations, heat set volume of each sample with a set volume of Benedict’s for the same time, use colorimeter to measure absorbance of each known conc, plot calibration curve conc x, absorb y, repeat with unkown sample and measure absorbance, read conc off graph
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26
Q

describe the biochemical test for starch

A

addd iodine dissolved in potassium iodide, shake and stir. positive = blue/black

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27
Q

name 2 groups of lipids

A

triglycerides and phospholipids

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28
Q

describe the structure of a fatty acid (RCOOH)

A

variable R-group - hydrocarbon chain (saturated or unsaturated)
- COOH is the carboxyl group

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29
Q

describe the difference btwn saturated and unstaturated fatty acids

A

saturated - non C=C bonds in hydrocarbon chain, all carbons are fully saturated with hydrocarbon
unsaturated - one or more C=C bond in hydrocarbon chain creating kinks

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30
Q

describe how triglycerides form

A

1 glycerol molecule and 3 fatty acids, condensation reaction, removing 3 water molecule, forming 3 ester bonds

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31
Q

what is the function of a triglyceride

A

energy storage

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32
Q

explain how the properties of triglycerides relate to their structure

A
  • high ratio of C-H bonds to C atoms in hydrocarbon chain, so used in respiratio tto release more energy than same mass of carbohydrates
  • hydrophobic/non polar fatty acids soinsoluble in water (clump together in droplets) , no effect on water potential of cell
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33
Q

describe the difference btwn the structure of triglycerides and phospholipids

A

triglyceride - glycerol, 3 fatty acids
phospholipid - glycerol, 2 fatty acids, phosphate group

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34
Q

what is the function of phospholipids

A

forms a bilayer in cell membrane, allowing diffusion of lipid-soluble (non polar) or very small substances and restricting movement of water soluble (polar) or larger substances

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35
Q

describe how the properties of phospholipids relates to its structure

A
  • phospholipid heads are hydrophillic, attracted to water so point to water either side of membrane
  • fatty acid tails are hydrophobic, repelled by water so point awat from water
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36
Q

describe the test for lipids

A

add ethanol, shake to dissolve lipids then add water. positive = milky white emulsion

37
Q

describe the general structure of an amino acid

A

COOH carboxyl group
R variable side chain/group
H2N amine group
R
,
H2N - C -COOH
,
H

38
Q

how many amino acids are common in all organisms and how do they vary

A

20 common amino acids, differ with their R group

39
Q

describe how amino acids join together

A

condensation reaction which removes a water molecule btwn carboxyl group and amine group of another to form a peptide bond

40
Q

what are dipeptides

A

2 amino acids joined together

41
Q

what are polypeptides

A

many amino acids joined together

42
Q

what type of protein contains one or more polypeptide

A

functional protein

43
Q

describe the primary structure of a protein

A

sequence of amino acids in a polypeptide chain, joined together by peptide bonds

44
Q

describe the secondary structure of a protein

A

folding of polypeptide chain e.g. alpha helix, beta pleated sheets due to hydrogen bonding btwn amino acidss btwn NH and C=O

45
Q

describe the tertiary structure of a protein

A

3D folding of a polypeptide chain due to interactions btwn amino acid R groups forming hydrogen, ionic bonds and disulfide bridges

46
Q

describe the quaternary structure of a protein

A

more than one polypeptide chain formed by interactions btwn polypeptides

47
Q

describe the test for proteins

A

add biuret reagent (sodium hydroxide and copper II sulphate). positive result - purple, lilac colour

48
Q

how do enzymes act as biological catalysts

A

each enzyme lowers activation energy of a reaction it catalyses to speed up rate of reaction

49
Q

Learn

A

enzymes catalyses a wide range of intracellular and extracellular reactions that determine structures and functions from cellular to whole organism level

50
Q

describe the induced fit model of enzyme action

A

substrate binds to active site of enxyme
causing active site to change shape so it is complementary to substrate
enzyme-substrate complex forms
causing bonds in substrate to bend/distoart, lowering activation energy

51
Q

describe how the models of enzyme action have changed over time

A

initially lock and key model, active site is a fixed shape and complementary to one substrate, now induced fit model

52
Q

explain the specificity of enzymes

A

specific tertiary structure determines the shape of active site which is dependent on sequence of amino acids
active site is complementary to specific substrate, only this substrate can bind to active site, inducing fit and forming an enzyme-substrate complex

53
Q

describe and explain the effect of enzyme conc. on the rate of enzyme-controlled reactions

A

as enzyme conc increases, rate of reaction increases
enzyme conc. = limiting factor, more enzymes = more available active sites so more enzyme-substrate complexes form
at a certain point, rate of reaction stops icnreasing/levels off due to substrate conc. limiting factor

54
Q

describe and explain the effect of substrate conc. on rate of enzyme-controlled reactions

A

as substrate conc. increases, rate of reaction increases. substrate conc. = limiting factor, more enzyme substrate complexes form
at certain point, rate of reaction stops increasing/levels off. enzyme conc. = limiting factor, all active sites saturate/occupied

55
Q

describe and explain effect of temp. on rate of enzyme controlled reactions

A

as temp increases up to optimum, rate of reaction increases more kinetic energy so more energy substrate complexes form
as temp. increases above optimum, rate of reaction decreases, enzymes denature, tertiary structure and active site change shape, as hydrogen, ionic bonds break, active site no longer complementary so fewer enzyme substrate complexes form

56
Q

describe and explain effect off pH on rate of enzyme controlled reactions

A

as pH increases/decrases below/above an optimum, rate of reaction decreases, ennzymes denature - tertiary and active site changes shape, hydrogen/ionic bonds break so active site no longer complementary so fewer enzyme-substrate complexes form

57
Q

Describe and explain the effect of conc. of competitive inhibitors on the rate of enzyme controlled reactions

A

as the conc. of competitive inhibitor increases, rate of reaction decreases
- similar shape to substrate
- compete for/binds to/blocks active site
- substrates can’t bind and fewer E-S complexes form

increasing substrate conc. reduces effect of inhibitors

58
Q

Describe and explain the effect of conc. of non-competitive inhibitors on rate of enzyme-controlled reactions

A

as conc. of non-competitive inhibitors increases, rate of reaction decreases
- binds to site other than the active site
-changes enzyme tertiary structure/active site shape
- active site is no longer complementary to substrate so substrate cannot bind so fewer E-S complexes form
increasing substrate conc. has no effect on rate of reaction as change to active site is permanent

59
Q

what is the basic function of DNA in all living cells

A

holds genetic informations which codes for polypeptides

60
Q

what is the basic function of RNA in all living cells

A

transfers genetic information from DNA to ribosomes

61
Q

what 2 molecules are ribosomes made from

A

RNA and proteins

62
Q

Draw and label a DNA nucleotide

A

phosphate group?
deoxyribose sugar?
nitrogen containing organic base? (ATCG)

63
Q

Draw and label an RNA nucleotide

A

phosphate group?
ribose sugar?
nitrogen containing organic base? (AUCG)

64
Q

describe 2 differences btwn DNA and RNA nucleotide

A
  • deoxyribose sugar vs ribose subgar
  • thymine base for DNA, uracil base for RNA
65
Q

describe how nucleotides join together to form polynucleotides

A

condensation reactions remove water molecules btwn phosphate group of one nucleotide and deoxyribose/ribose of another forming phosphodiester bonds

66
Q

why did many scientists initially doubt that DNA carried the genetic code

A

relative simplicity of DNA, chemically simple molecule with few components

67
Q

Describe the structure of DNA

A
  • polymer of nucleotides
  • each nucleotide formed from deoxyribose, phosphate group, nitrogen containing organic base
  • phosphodiester bonds join adjacent nucleotides
  • 2 polynucleotide chains held together by hydrogen bonds btwn sepcific complementary base pairs: adenine, thymine + cytosine,guanine
  • double helix
68
Q

describe the structure of mRNA

A
  • polymer of nucleotides
  • each nucleotide formed from ribose, phosphate group, nitrogen containing organic base: uracil, adenine, cytosine, guanine
  • phosphodiester bonds join adjacent nucleotides
  • single helix
69
Q

compare DNA and RNA structure

A
  • deoxyribose vs ribose
  • thymine vs uracil
  • double stranded vs single stranded
  • long vs short
  • hydrogen parining n base parining vs none
70
Q

suggest how structure of DNA relates to its functions

A
  • 2 strands, both can act as a template for semi-conservative replication
  • hydrogen bonds btwn bases are weak, strands can be separated for replication
  • complementary base pairing, accurate replication
  • many hydrogen bonds btwn bases, stable and strong molecule
  • double helix with sugar phosphate backbone = protects bases and hydrogen bonds
  • long molecule = lots of genetic infromation stored
  • double helix = compact
71
Q

why is semi-conservative replication imporatnt

A

ensures genetic continuity btwn generations of cells

72
Q

describe the process of semi-conservative DNA replication

A
  • DNA helicase breaks hydrogen bonds btwn complementary bases, unwinding the double helix
  • both strands act as templates
  • free DNA nucleotides attracted to exposed bases and join by specific complementary base pairing
  • hydrogen bonds form btwn adenine-thymine and guanine-cytosine
  • DNA polymerase joins adjacent nucleotides on new strand by condensation reactions, forming phosphodiester bonds
73
Q

what is semi-conservative replication

A

each new DNA molecule consists of on orginal,template strand and one new strand

74
Q

why does DNA ploymerase move in opposite dirrections along DNA strands

A
  • DNA has antiparallel strands
  • shapes/arrangments of nucleotides on two ends are different
  • DNA polymerase is an enzyme with a specific shaped active site so it can only bind to substrate with complementary shape
75
Q

which 2 scientists proposed modecls of DNA and DNA replication

A

Watson and Crick

76
Q

how did Meselson and Stahl validate Watson-Crick model of semi conservative DNA replication

A
  • bacteria grown in medium containing heavy nitrogen (15N) and nitrogen is incorporated into DNA bases
  • DNA extracted and centrifuged, settles near the bottom as all DNA moleccules contain 2 heavy strands
  • bacteria transferred to mediumm containning light nitrogen (14N) and allowed to divide once
  • DNA extracted and centrifuged, settles in the middle as all DNA contains one heavy and one light strand
  • bacteria in light nitrogen (14N) allowed to divid again, when centrifuged hald settles in middle and half near top: heavy+light, light+light
77
Q

what does ATP stand for

A

adenosine triphosphate

78
Q

describe the structure of ATP

A

ribose bound to a molecule of adenine base and 3 phosphate groups

nucleotide derivative

79
Q

how is ATP broken down

A

ATP +water -> ADP + Pi

adenosine diphosphate, inorganic phosphate

hydrolysis reaction w water molecule, catalysed by ATP hydrolase

80
Q

give 2 ways in which hydrolysis of ATP is used in cells

A
  • releases energy for energy requiring reactions w/n cells e.g active transport, protein synthesis
  • inorganic phosphate released can be used to phosphorylate other compounds making them more reactive (add phosphate to)
81
Q

how is ATP resynthesised in cells

A

ADP + Pi -> ATP +water
condesation reaction, removing water molecule, catalysed by ATP synthase. occurs during respiration and photosynthesis

82
Q

suggest how the properties of ATP makes it a suitable immediate source of energy for cells

A

relases energy in relatively small amounts - little energy lost as heat. single reaction to release energy = immediate release. cannot pass out of cell, always available

83
Q

explain how hydrogen bonds occur btwn water molecules

A

water is a polar molecule
slightly negatively charged oxygen atoms attract slightly positively charged hydrogen atoms of other water molecules

84
Q

explain 5 properties of water that are important in biology

A

metabolite - used in condensation,hydrolysis, photosynthesis and respiration

solvent - allows metabolic reactions to occue and for the transport of substances e.g. in xylem

high specific heat capacity - buffers changes in temperature, gain and lose a lot of heat energy w/o changing temp, good habitat for aquatic organisms as temp is more stable than on land, helps maintain constant internal body temp

high latent heat of vapourisation - allows effective cooling via evapouration of a small volume e.g. sweat, helps organisms maintain a constand internal body temp

strong coheion btwn water molecules - supports columns of water e.g. tranpiration stream through xylem in plants, produces surface tension to allow small organisms to walk on water

85
Q
A
86
Q

describe the structure and shape of globular proteins

A
  • spherical shape from tightly folded polypeptide chains
  • folded so that hydrophobic groups are on the inside and hydrophillic groups on the outside
  • many are soluble
87
Q

give 3 examples of globular proteins

A

transport - haemoglobin
enzymes - lipase, DNA
hormones - oestrogen, insulin

88
Q

describe the structure of fibrous proteins

A

formed from parallel polypeptide chains held together by cross links to form long, rope-like fibres
generally insoluble

89
Q

give 3 examples of fibrous proteins

A

collagen - ligaments, tendons, cartilage
keratin - nails, claws, hair, hooves
silk - silk worm cocoons

90
Q

how to calculate pH conc.

A

pH = -log₁₀ [H⁺]

[H+] = 10^-pH

Biology A-Level (11 decks)

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