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biology year 12 > biological molecules > Flashcards

biological molecules Flashcards

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1
Q

what do all carbohydrates contain?

A

carbon, hydrogen and oxygen

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2
Q

what is a monosaccharide?

A

monomer from which a larger carbohydrate is made

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3
Q

what is an isomer?

A

same molecular formulaa but atoms connected differently

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4
Q

what is glucose?

A

a hexose sugar, which exists as two isomers (alpha and beta)

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5
Q

what is a disaccharide?

A

2 monosaccharides joined together by condensation reactions which form glycosidic bonds

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6
Q

what are the disaccharides formed by glucose?

A

2x glucose: maltose
glucose + fructose: sucrose
glucose + galactose: lactose

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7
Q

what is a reducing sugar?

A

a sugar that can donate an electron to reduce another chemical. all mono- and some disaccharides

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8
Q

how do you carry out the benedict’s test?

A

add benedict’s reagent to a sample and heat it in a boiling water bath. a positive test will form a coloured precipitate: green-yellow-orange-brick red. the higher the concentration of reducing sugar, the further along the colour change

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9
Q

how do you test for a non reducing sugar?

A

following a negative benedict’s test, get a new sample of solution and add dilute hydrochloric acid and heat in a boiling tube (hydrolyses glycosidic bonds). add sodium hydrogencarbonate (to neutralise). then repeat benedicts test. positive result shows a non reducing sugar is present.

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10
Q

what is a polysaccharide?

A

more than two monosaccharides joined by condensation reactions. can be broken down by hydrolysis.

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11
Q

what is the purpose of starch?

A

plants store of excess glucose

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12
Q

describe the structure of starch:

A

a mixture of two polysaccharides of alpha glucose.
amylose: long, unbranched chain of alpha glucose. angles of the glycosidic bonds give it a coiled helical shape. hydrogen bonds help to hold amylose in helical structure
amylopectin: long, branched chain of alpha glucose. side branches allow enzymes to get at the glycosidic bonds easily so that glucose can be released quickly

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13
Q

what properties of starch make it a good storage molecule?

A

insoluble so doesn’t affect water potential
helical structure makes it compact

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14
Q

what is glycogen?

A

animal store of glucose

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15
Q

describe the structure of glycogen:

A

another polysaccharide of alpha glucose. similar on structure to amylopectin, but more highly branched for fast glucose release. very compact so good for storage

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16
Q

what is cellulose?

A

polysaccharide which provides structural support for cells and allows them to resist turgor pressure

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17
Q

describe the structure of cellulose:

A

long, unbranched chains of beta glucose. when beta glucose molecules bond they form straight cellulose chains. the chains are linked by many hydrogen bonds to form strong fibres called microfibrils.

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18
Q

how do you test for starch?

A

iodine test. add iodine dissolved in potassium iodide to sample. if starch is present, the sample goes from orange to blue-black

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19
Q

what are lipids?

A

not polymers. formed from a variety of hydrocarbon components.

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20
Q

describe the structure of a triglyceride:

A

one molecule of glycerol and 3 fatty acids attached to it. fatty acid molecules have long tails made of hydrocarbons. tails are hydrophobic therefore lipids are insoluble in water.

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21
Q

what is the difference between a saturated and non-saturated fatty acid?

A

saturated don’t contain any double bonds between carbons, whereas unsaturated do

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22
Q

how are triglycerides formed?

A

triglycerides are formed by condensation reactions which results in an ester bond between the glycerol and a fatty acid, releasing a molecule of water

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23
Q

describe the structure of phospholipids:

A

similar to triglycerides but one of the fatty acids is replaced by a phosphate group. the phosphate is hydrophilic, whilst the fatty acids are hydrophobic

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24
Q

what are the properties of triglycerides?

A

mainly used as an energy storage molecule. long hydrocarbon tails contain lots of energy which is released when they’re broken down. insoluble in water so don’t affect water potential. triglycerides bundle together as droplets, because the tails are hydrophobic so face inward, shielding themselves with glycerol head.

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25
Q

what are the properties of phospholipids?

A

make up bilayer of cell membranes which controls what enters and leaves cells. phospholipids form double layer with hydrophilic heads facing out towards water, and centre is hydrophobic so water soluble substances can’t easily pass through

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26
Q

how do you carry out the emulsion test?

A

shake test substance with ethanol for about a minute and then pour solution into water. any lipid will show up as a milky white emulsion. the more emulsion the more lipid.

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27
Q

what is a protein?

A

more than one polypeptide joined together by peptide bonds formed by condensation reactions

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28
Q

what is an amino acid made up of?

A

an amine group, carboxyl group, variable region and a hydrogen all attached to a central carbon

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29
Q

what is the primary structure of a protein?

A

sequence of amino acids in the polypeptide chain

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30
Q

what is the secondary structure of a protein?

A

polypeptide chain doesn’t stay straight. hydrogen bonds form between amino acids in the chain which make it coil in an alpha helix or beta pleated sheet

31
Q

what is the tertiary structure of a protein?

A

further folding/coiling. ionic and hydrogen bonds form, as well as disulfide bridges between two molecules of cysteine. for proteins made from a single polypeptide, this is the final 3D structure.

32
Q

what is the quarternary structure of a protein?

A

some proteins are formed from several different polypeptide chains, held by bonds. the quarternary structure is the way these proteins are assembled and is the final 3D structure for these proteins.

33
Q

how do you carry out the biuret test?

A

add a few drops of sodium hydroxide to the solution
add copper (III) sulfate solution
if protein is present, the solution will turn purple

34
Q

what are enzymes?

A

enzymes biological catalysts which are proteins

35
Q

why are enzymes specific?

A

the active site of an enzyme has a specific shape, which is due to its tertiary structure. if the tertiary structure of enzyme is altered in any way the active site will change shape and enzyme will denature

36
Q

how do enzymes speed up a reaction?

A

enzymes lower the activation energy of a reaction, so reactions can happen at a lower temperature.
if 2 substrates need to be joined then being attached to the active site forces them together, reducing any repulsion.
if catalysing a breakdown, fitting into the active site puts strain on the bonds of the substrate so breaks up more easily

37
Q

describe the lock and key model:

A

substrate fits into active site exactly due to complementary shape

38
Q

describe the induced fit model:

A

substrate fits into enzyme, shape of active site changes slightly, distorting bonds so fit more tightly

39
Q

what is the effect of temperature on rate?

A

initially, rate increases as more kinetic energy so substrate more likely to collide with enzyme and form an enzyme substrate complex. if temperature gets too high, the enzyme molecules vibrate more which breaks some of the bonds that hold the enzyme in shape so enzyme denatures

40
Q

what is the effect of pH on rate?

A

all enzymes have an optimum pH. above and below this, the H+ and OH- ions can disrupt the ionic and hydrogen bonds that hold the enzymes tertiary structure in place, so active site changes shape

41
Q

what is the effect of substrate concentration on rate?

A

higher rate, because increased likelihood of collisions and more active sites occupied. however, after the saturation point, all the active sites are occupied so adding substrate has no effect anymore

42
Q

what is the effect of enzyme concentration on rate?

A

higher rate, because increased likelihood of collisions and more active sites available. however, if substrate is limited then there comes a point where more than enough enzymes to deal with all available substrate so no further effect

43
Q

how to competitive inhibitors affect the rate?

A

similar in shape to the substrate so will compete with substrate and block the active site. however, increasing substrate conc. will outcompete the inhibitors so rate will increase

44
Q

how do non competitive inhibitors affect the rate?

A

bind to enzyme away from the active site, causing the active site to change shape so substrate can no longer bind. increasing substrate conc. has no effect

45
Q

what is a nucleotide?

A

type of biological molecule made from 3 different components: pentose sugar, nitrogenous base and a phosphate group

46
Q

what is the structure of a polynucleotide?

A

many nucleotides joined together via condensation reactions between the phosphate group of one nucleotide and the sugar of another. this forms a phosphodiester bond. this chain is known as the sugar phosphate backbone

47
Q

what is the structure of DNA?

A

deoxyribose sugar. double helix, formed from 2 separate polynucleotide strands which wind around each other to form a spiral. the polynucleotide strands are antiparallel

48
Q

what is the role of complementary base pairing in DNA?

A

two DNA strands join by hydrogen bonds between the bases. each base can only join with one particular partner: adenine with thymine, guanine with cytosine. there is always equal amounts of A and T, and C and G in DNA. 2 H bonds form between A and T, and 3 H bonds form between C and G

49
Q

what is DNA used for?

A

to store your genetic info

50
Q

what is RNA used for?

A

mainly used to transfer genetic info to the ribosomes

51
Q

what is the structure of RNA?

A

ribose sugar. nucleotides form a single polynucleotide strand, which is much shorter than most DNA strands.
bases in RNA are adenine, uracil, guanine and cytosine

52
Q

what is ‘semi conservative replication’?

A
  1. DNA helicase breaks the H bonds between bases on the 2 polynucleotide strands, helix unwinds to form 2 single strands
  2. each original strand acts as a template for a new strand. complementary base pairing means free floating nucleotides are attracted to their complementary exposed bases on the template strand
  3. condensation reactions join the nucleotides of the new strand together, catalysed by DNA polymerase. H bonds form between the bases on the original and new strands
53
Q

describe the action of DNA polymerase:

A

DNA strands have a 5’ end and a 3’ end. the active site of DNA polymerase is only complementary to the 3’ end, so the new nucleotides can only be added to the 3’ end. therefore the new strand is made in a 5’ to 3’ direction, and moves down the template strand in the 3’ to 5’ direction. because strands are antiparallel, the DNA polymerase working on one of the template strands moves in the opposite direction to the DNA polymerase on the other template strand

54
Q

Explain why the DNA polymerase moves in two different directions:

A

DNA strands are antiparallel
Shape of nucleotides is different i.e 3’ and 5’
Enzyme active site is specific in shape
Only the 3’ end can bind to the active site

55
Q

what is ATP?

A

adenosine triphosphate. nucleotide derivative, which diffuses to the part of the cell that needs energy

56
Q

describe the structure of ATP?

A

ribose sugar, adenine base and 3 phosphate groups

57
Q

how is energy stored and released in ATP?

A

stored in high energy bonds between the phosphate bonds, released via hydrolysis reactions

58
Q

what are the equations for the hydrolysis and synthesis of ATP?

A

Hydrolysis:
ATP + water —-> ADP + Pi
catalysed by ATP hydrolase

Synthesis:
ADP + Pi —-> ATP + water
catalysed by ATP synthase

59
Q

how is the energy from ATP used?

A

ATP hydrolysis can be coupled to other reactions, so the energy can be used directly rather than being lost as heat
Pi can be added to another compound (phosphorylation) which often makes the compound more reactive

60
Q

what is specific heat capacity?

A

energy needed to raise the temperature of 1g of substance by 1 degree celcius

61
Q

what is latent heat of vaporisation?

A

energy needed to change one gram of a substance from liquid to gas

62
Q

why is water polar?

A

the shared negative electrons in the covalent bonds between hydrogen and oxygen are pulled towards the oxygen atom. other side of the hydrogen atom is left with a slight positive charge, and the oxugen has a slightly negative charge

63
Q

why is water an important metabolite?

A

many metabolic reactions involve a condensation or hydrolysis reaction. hydrolysis requires a molecule of water to break a bond. condensation reactions release a molecule of water to form a new bond

64
Q

why is water a good solvent?

A

due to its polarity, the slightly positive end of water will be attracted to the negative ion in an ionic compound whilst the slightly negative end is attracted to the positive ion. ions get totally surrounded by water and dissolve. this property means that living organisms can take up useful substances dissolved in water to be transported around the body

65
Q

how is a high latent heat of vaporisation a benefit of water?

A

lots of energy required to break the H bonds holding water molecules together. this means organisms can cool down (release lots of heat energy) without losing too much water.

66
Q

how does water buffer temperature changes?

A

H bonds give water a high specific heat capacity. this is useful as water doesn’t experience rapid temperature change, and so is a good habitat, as it helps organisms maintain a stable body temperature

67
Q

why is being very cohesive a benefit of water?

A

strong cohesion allows water to flow, making it great for transporting substances. also means water has a high surface tension when it comes into contact with air (how sweat droplets form)

68
Q

what is an inorganic ion?

A

an ion which doesn’t contain carbon

69
Q

where are inorganic ions found?

A

in the cytoplasm of cells and the body fluids of organisms

70
Q

what is the role of iron ions in haemoglobin?

A

Hb is a large protein that carries O2 around the body, made up of 4 polypeptide chains, each with an iron ion in the centre. it is the iron ion which actually binds to the O2

71
Q

what is the role of hydrogen ions?

A

pH calculated based on the conc. of hydrogen ions in the environment. the more H+ the lower the pH

72
Q

what is the role of sodium ions?

A

glucose and amino acids are co-transported into the cell alongside Na+

73
Q

what is the role of phosphate ions?

A

DNA, RNA and ATP all contain phosphate groups. in ATP, the bonds between phosphate groups store energy. in DNA and RNA, the phosphate groups allow nucleotides to join up to form the polynucleotides

biology year 12 (4 decks)

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