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AQA A-LEVEL BIOLOGY > 1. Biological Molecules > Flashcards

1. Biological Molecules Flashcards

1
Q

Monomer

A

small units from which larger molecules are made

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2
Q

Polymer

A

molecules made from a large number of monomers joined together

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3
Q

Condensation reaction

A

joins two molecules together, with formation of chemical bond, releasing a molecule of water

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4
Q

Hydrolysis reaction

A

breaks chemical bond between two molecules, using a molecule of water

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5
Q

Monosaccharide

A

monomers from which larger carbohydrates are made (eg. glucose, fructose, galactose)

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6
Q

Disaccharide

A

formed by condensation of two monosaccharides, joined by glycosidic bond (eg. maltose, sucrose, lactose)

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7
Q

Polysaccharide

A

formed by condensation of many monosaccharides, joined by glycosidic bonds (eg. starch, glycogen, cellulose)

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8
Q

Glycosidic bond

A

C-O-C link (covalent bond) between two monosaccharides, formed by condensation reaction

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9
Q

Cellulose

A

polysaccharide in plant cell walls formed by condensation of B-glucose, long straight chains linked by many hydrogen bonds forming string microfibrils, insoluble in water so doesn’t affect water potential by osmosis

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10
Q

Glycogen

A

polysaccharide in animals formed by condensation of a-glucose, branched (1,4 and 1,6 glycosidic bonds) so glycosidic bonds easily hydrolysed, coiled so compact, insoluble in water so doesn’t affect water potential by osmosis

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11
Q

Starch

A

polysaccharide in plants formed by condensation of a-glucose, branched (1,4 and 1,6 glycosidic bonds) so glycosidic bonds easily hydrolysed, coiled so compact, insoluble in water so doesn’t affect water potential by osmosis

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12
Q

Test for reducing sugars

A

add Benedict’s reagent and heat, brick red precipitate forms if positive

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13
Q

Test for non-reducing sugars

A

following negative Benedict’s test for reducing sugars, boil with acid then neutralise with alkaline, reheat with Benedict’s reagent, brick red precipitate forms if positive

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14
Q

Test for starch

A

add iodine, turns blue/black if positive

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15
Q

Triglyceride

A

formed by condensation of one molecule of glycerol and 3 fatty acids, forming 3 ester bonds, large ratio of C-H bonds to total number of C atoms so lots of energy stored, high ratio of H to O so act as metabolic water source, insoluble in water so doesn’t affect water potential by osmosis

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16
Q

Phospholipid

A

formed by condensation of one molecule of glycerol, 2 fatty acids and one phosphate group, held by 2 ester bonds, polar molecule so heads attracted to water and tails repelled, forming phospholipid bilayer, insoluble in water so doesn’t affect water potential by osmosis

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17
Q

Ester bond

A

-COO- chemical bond between glycerol and fatty acids

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18
Q

Hydrophilic

A

ability to mix, interact or attract water

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19
Q

Hydrophobic

A

tendency to repel water

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20
Q

Saturated fatty acid

A

long hydrocarbon chain with a carboxyl group at one end, only single bonds between carbon atoms

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21
Q

Unsaturated fatty acid

A

long hydrocarbon chain with a carboxyl group at one end, at least one double bond between carbon atoms

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22
Q

Test for lipids

A

add ethanol and shake to dissolve, pour into water, white emulsion forms if positive

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23
Q

Amino acid

A

monomer of protein, contains COOH (carboxyl group), NH2 (amine group) and R group (variable group)

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24
Q

Dipeptide

A

two amino acids, joined by a peptide bond, formed by condensation reaction

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25
Q

Polypeptide

A

polymer chain of protein, made up of many amino acid monomers, held together by peptide bonds

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26
Q

Peptide bond

A

covalent bond joining amino acids, C-N link formed by condensation reaction

27
Q

Primary structure

A

sequence of amino acids in the polypeptide chain

28
Q

Secondary structure

A

folding or coiling of polypeptide chain into B pleated sheet or a helix, held in place by hydrogen bonds

29
Q

Tertiary structure

A

further folding of polypeptide chain to create specific 3D shape, held in place by hydrogen bonds, ionic bonds and disulfide bridges

30
Q

Quaternary structure

A

more than one polypeptide chain

31
Q

Hydrogen bond

A

weak bond, forms between H and O

32
Q

Ionic bond

A

bond that forms between the R groups of different amino acids

33
Q

Disulfide bridge

A

strong covalent bond between two sulfur atoms in the R groups of different amino acids

34
Q

Test for protein

A

add biuret, turns purple if positive

35
Q

Enzyme-substrate complex

A

specific enzyme collides and binds to complementary substrate, lowering activation energy

36
Q

Activation energy

A

minimum amount of energy required for a reaction to occur

37
Q

Induced-fit model

A

substrate binds to enzymes active site, the active site changes shape slightly so it is complementary to the substrate, putting tension on bonds, lowering activation energy

38
Q

Effect of temperature

A

increasing temperature increases kinetic energy so more frequent successful collisions, if temperature too high active site changes shape so no ESC can form (enzyme denatures)

39
Q

Effect of pH

A

too high or too low pH interferes with charges in the amino acids in active site, breaking hydrogen and ionic bonds so active site changes shape so no ESC can form (enzyme denatures)

40
Q

Effect of substrate concentration

A

increasing substrate concentration means more collisions, but rate begins to plateau as all enzyme active sites are occupied (saturation point)

41
Q

Effect of enzyme concentration

A

increasing enzyme concentration means more collisions, but rate begins to plateau as substrate becomes limiting factor

42
Q

Competitive inhibitor

A

similar shape to substrate so binds to active site of enzyme, blocking active site so no ESC can form

43
Q

Non-competitive inhibitor

A

binds to allosteric site of enzyme (away from active site), causing active site to change shape so no ESC can form

44
Q

DNA nucleotide

A

monomer of DNA, contains a deoxyribose sugar, a phosphate group and and nitrogenous base

45
Q

RNA nucleotide

A

monomer of RNA, contains a ribose sugar, a phosphate group and nitrogenous base

46
Q

Polynucleotide

A

polymer chain of many nucleotides joined by condensation reactions, joined by phosphodiester bonds

47
Q

DNA

A

polynucleotide with double helix, long, coiled structure, sugar-phosphate backbone for strength and stability, weak hydrogen bonds between complementary base pairs (adenine and thymine, guanine and cytosine)

48
Q

mRNA

A

single-stranded polymer of RNA

49
Q

tRNA

A

found in cytoplasm, single-stranded but folded into clover shape, hydrogen bonds between complementary base pairs, amino acid binding site at one end and anticodon at other end

50
Q

DNA replication

A

DNA helicase breaks hydrogen bonds between complementary base pairs, unwinding helix into two single strands, both strands act as templates, free DNA nucleotides bind to exposed based on template by complementary base pairing, DNA polymerase joins adjacent nucleotides forming phosphodiester bonds, hydrogen bonds reform

51
Q

Semi-conservative

A

in new DNA one strand from parental DNA and one strand newly synthesised, allows for genetic continuity

52
Q

ATP

A

nucleotide derivative made of an adenine base, a ribose sugar and 3 phosphate groups

53
Q

ATP properties

A

rapidly resynthsised, releases small manageable amounts of energy at a time so little energy lost as heat, easily broken down in one step so releases energy instantaneously, phosphorylates other compounds making them more reactive, polar so can’t leave cell, small and soluble so easily transported round cell

54
Q

ATP synthesis

A

ADP+Pi join by condensation reaction to form ATP, cataysled by ATP synthase

55
Q

ATP hydrolysis

A

ATP is hydrolysed into ADP+Pi, catalysed by ATP hydrolase

56
Q

Water

A

one O atom covalently bonded to 2 H atoms, di-polar molecule (uneven distribution of charge), O atom is slightly negative, H atom is slightly positive

57
Q

Water properties

A

large latent heat of vapourisation so evaporation acts as an effective cooling mechanism, high specific heat capacity so buffers changes in temperature, metabolite in hydrolysis reactions, solvent for transport of substances, cohesive so supports columns of water

58
Q

Large latent heat of vapourisation

A

lots of energy is required to covert water from liquid to gaseous state as lots of energy is needed to break hydrogen bonds between water molecules

59
Q

High specific heat capacity

A

lots of energy is required to raise temperature of water as some heat energy is used to break break hydrogen bonds between water molecules

60
Q

Inorganic ions

A

charged atoms which don’t contain carbon, occur in solution in cytoplasm of cells or in body fluids of organisms

61
Q

Iron ions

A

Fe2+, found in haemoglobin, bind to oxygen forming Fe3+

62
Q

Hydrogen ions

A

H+, the more H+ the more acidic (lower the pH) the solution

63
Q

Sodium ions

A

Na+, involved in co-transport of glucose and amino acids in the ileum

64
Q

Phosphate ions

A

PO43-, component of ATP, DNA, RNA

AQA A-LEVEL BIOLOGY (8 decks)

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