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Biology A level > (1) Biological molecules > Flashcards

(1) Biological molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is a molecule

A

made up of 2 or more different non metal atoms in covalent bonds

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2
Q

what is a monomer

A

a single repeating molecular unit that join together to make a polymer by covalently bonding

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3
Q

why are energy stores such as starch and glucose insoluble

A

so they won’t dissolve in the cells and affect osmosis

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4
Q

what are sugar molecules made up of

A

carbon
hydrogen
oxygen

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5
Q

what polymers does alpha glucose make

A

starch and glycogen

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6
Q

what polymer does beta glucose make

A

cellulose

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7
Q

what polymer does amino acids make

A

protein/ polypeptide

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8
Q

what polymer does a nucleotide make

A

dna

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9
Q

how is sucrose made

A

when alpha glucose reacts with fructose in a condensation reaction (WTHOE)

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10
Q

how is lactose produced

A

when alpha glucose reacts with galactose in a condensation reaction (WTHOE)

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11
Q

what is a polysaccharide

A

a sugar polymer made of thousands of monomer molecules in glycosidic bonds which have been made in condensation reactions

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12
Q

what is hydrogen bonding

A

when the elections in a molecule are not evenly distributed so one region is more negatively charged than the rest of the molecule (polar molecule) the negative region of one molecule and the positive of another attract and a weak electrostatic bond is formed

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13
Q

what is hydrolysis

A

the breaking down of large molecules into smaller ones by the addition of water molecules which breaks the glycosidic bond
(opposite of condensation reaction)

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14
Q

how is maltose formed

A

2 glucose molecules and a condensation reaction

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15
Q

what is a glycosidic bond

A

the bond formed in a condensation reaction

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16
Q

what is a condensation reaction

A

a chemical process in which 2 molecules combine to form a more complex one with the elimination of a simple substance (usually water)

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17
Q

why does benedicts reagent turn red when heated with a reducing sugar

A

benedicts reagent is an alkaline solution of copper (II) sulfate and when it is heated with a reducing sugar it produces an insoluble red precipitate of copper (I) oxide

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18
Q

what is hydrolysis

A

adding water to a disaccharide under suitable conditions which breaks the glycosidic bond and releases the constituent monosaccharides

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19
Q

how do you detect a reducing sugar

A

add it to benedicts reagent and the colour will change

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20
Q

how do you detect a non-reducing sugar

A

add to benedicts reagent and heat in a water bath for 5 mins if a colour change doesn’t occur there is no reducing sugar.

so, add the food sample to dilute HCL and heat in boiling water bath for 5 mins. Any disaccharide present should hydrolyse into its constituent molecules

add sodium hydrogencarbonate to neutralise the HCL and test with pH paper to check its alkaline
heat resulting solution with benedicts reagent in boiling water bath for 5 mins
if a non reducing sugar is present, benedicts reagent will now turn orange brown due to reducing sugars that were produced from the hydrolysis of the non reducing sugar.

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21
Q

what is starch made up of

A

a-glucose monosaccharides joined by 1,4-glycosidic bonds (helical structure) and branches linked by 1,6-glycosidic bonds

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22
Q

how is the structure of glucose adapted for its function of energy storage (5 ways)

A

1) insoluble so doesn’t affect water potential or osmosis
2) large and insoluble means it doesn’t diffuse out of cells
3) compact, can be stored in a small space
4) when hydrolysed it forms a-glucose which is easily transported and used in respiration
5) branched form has many ends so enzymes can act on it simultaneously so glucose monomers can be released quickly

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23
Q

where is starch found

A

in plants in the form of small grains

especially large amounts are found in seeds and storage organs eg potato tubers

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24
Q

how does the structure of glycogen suit it for its function (4 ways)

A

1) insoluble so doesn’t affect osmosis
2) doesn’t diffuse out of cells so good for storage
3) compact- a lot can be stored in a small space
4) more highly branched than starch so enzymes can act on it faster and eventually release energy faster which is necessary as animals are more mobile than plants (have a higher metabolic and respiration rate) and more likely to need emergency energy

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25
Q

how is cellulose different to starch and glycogen

A

made of monomers of b-glucose rather than a-glucose so doesn’t form a coiled chain but a linear chain

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26
Q

describe the structure of cellulose

A

cellulose molecules are grouped together to form microfibrils which are arranged in parallel groups called fibres

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27
Q

what are 4 roles of lipids

A

1) source of energy- when oxidised lipids provide more than double the energy as carbs and release water
2) waterproofing- insoluble in water (both plants and insects have waxy lipid cuticles that conserve water
3) insulation- fats are slow conductors or heat and help retain body heat. also act as electrical insulators in the myelin sheath around nerve cells
4) protection- fat is often stored around delicate organs

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28
Q

how are triglycerides formed

A

each one of the 3 fatty acids forms an ester bond with glycerol in a condensation reaction

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29
Q

why do triglycerides release water when oxidised

A

they have a high ratio of hydrogen to oxygen atoms

30
Q

why are triglycerides a good source of energy

A

they have a high ratio of energy storing carbon-hydrogen bonds

31
Q

why are triglycerides good storage molecules

A

they have a low mass to energy ratio so can store a lot of energy in a small mass/ volume

32
Q

how is a phospholipid different to a lipid

A

one of the fatty acid molecules is replaced by a phosphate molecule.
fatty acid molecules are hydrophobic but phosphate molecules are hydrophilic so a phospholipid has a ‘head’ and ‘tail’

33
Q

how many amino acids occur naturally in proteins

A

20

34
Q

what are the 4 chemical groups which the central carbon atom in an amino acid is attached to

A

1) amino group (-NH2) the amino part
2) carboxyl group (-COOH) an acidic group making it an acid
3) hydrogen atom (-H)
4) R (side) group) each amino acid has a different R group

35
Q

what are the bonds between amino acids in proteins called

A

peptide bonds

36
Q

how are hydrogen bonds formed in proteins

A

the hydrogen of the -NH group has a positive charge but the O of the -C=O group has an overall negative charge so they attract and form a weak bond called hydrogen bond

37
Q

what bonds do secondary structures of proteins have

A

hydrogen bonds

38
Q

what are the 3 types of bonds in a tertiary protein structure

A

disulfide bridges
ionic bonds
hydrogen bonds

39
Q

what is a disulfide bond

A

a covalent bond between neighbouring cysteine amino acids which is fairly strong and stabilises the structure

40
Q

what is an ionic bond in a tertiary protein

A

formed between any carboxyl and amino groups that are not involved in forming peptide bonds

41
Q

what is the quarternary structure of a protein

A

made of several polypeptide chains held together by disulfide bonds, hydrogen bonds and ionic bonds
sometimes a non metal is included and is called prosthetic group

42
Q

what does the biuret test test for and how is it done

A

detects peptide bonds

1) place a sample of solution to be tested in a test tube and add equal volume of sodium hydroxide at room temp
2) add a few drops of dilute copper sulfate solution and mix gently
3) purple colouration indicates presence of pepide bonds (a protein). if no protein it’ll remain blue

43
Q

what are enzymes

A

globular proteins that act as catalysts
alter the rate of chemical reaction without undergoing permanent changes themselves. effective in small amounts and can be reused repeatedly

44
Q

what is the active site

A

the shape of the enzyme made up of the sequence of amino acids (a smaller depression within the much larger enzyme molecule)

45
Q

for an enzyme to work it must…

A

come into physical contact with its substrate

have an active site that fits the substrate

46
Q

at what temperature do human enzymes start to change shape

A

45 degrees

47
Q

what temperature are human enzymes said to be denatured

A

60 degrees

48
Q

human enzymes have an optimum of 40 degrees so why have our body temperatures evolved to be 37 degrees

A

higher body temp would increase metabolic rate but but more energy (food) would be required to maintain the higher temp

other proteins could be denatured at a higher temp

at a higher temp, a further rise in temp due to illness might denature enzymes

49
Q

what is the pH of a solution

A

the concentration of hydrogen ions

50
Q

if a solution had a hydrogen ion concentration of 1x10^-9 what would its pH be

A

9

51
Q

how does a change in pH affect an enzyme

A

alters the charges on the amino acids that make up the active site so shape changes or bonds can no longer be formed and enzyme substrate complex can no longer form

52
Q

what determines the arrangement of the active site

A

the hydrogen and ionic bonds between NH2 and COOH groups of the polypeptides that make up the enzyme also a change in H+ ions affects this bonding causing the active site to change shape

53
Q

what is a competitive inhibitor

A

have a molecular shape similar to the substrate so can occupy the active site and then competes with substrates for active sites. if there is a higher concentration of substrates however the effect of the inhibitor is reduced

54
Q

what is a non competitive inhibitor

A

attach themselves to the enzyme but not at the active site but can alter the active site from doing this so that substrate molecules can no longer occupy it. increase in substrate conc doesn’t affect effect of inhibitor as they are competing for different sites

55
Q

what is a nucleotide

A

monomer that makes up dna

contains a phosphate, base (ATGC) and deoxyribose (sugar)

56
Q

what are the names of the 4 nitrogen containing organic bases

A

adenine
thymine
cytosine
guanine

57
Q

what is the type of bond between bases and why is it used

A

hydrogen bond

because it’s weak so can separate when dna needs to replicate

58
Q

what is the outside of a dna molecule made up of

A

sugar and phosphate

59
Q

which sets of bases are present in equal amounts

A

adenine and thymine

guanine and cytosine

60
Q

what type of bonds are nucleotides held together by

A

phosphodiester bond

61
Q

what is a phosphodiester bond

A

the bond that joins 2 nucleotides together by enzymes in a condensation reaction

62
Q

how is the dna structure stabilised

A

the phosphodiester bond protects the more chemically reactive organic bases inside the double helix
and
hydrogen bonds link the organic base pairs forming bridges
and
the higher proportion of C-G pairings the more stable the dna as there are 3 hydrogen bonds between cystine and guanine
and
base stacking creates interactive forces between the base pairs that hold the molecule together

63
Q

what are the 5 ways a dna molecule is adapted to carry out its functions

A

1) stable structure that passes from generation to generation without change and rarely mutates
2) 2 separate strands are joined only by hydrogen bonds which allow them to separate during dna replication and protein synthesis
3) large molecule so can store an immense amount of genetic info
4) genetic info is protected from being corrupted by outside chemicals and physical forces by having base pairs within the helical cylinder or the deoxyribose phosphate backbone
5) base pairing leads to dna being able to replicate and to transfer info a mRNA

64
Q

why does benedict’s reagent turn red when heated with a reducing sugar

A

because the sugar donates electrons which reduce blue copper (ii) oxide into orange/ red copper (i) oxide

65
Q

how to tell if an enzyme is being inhibited by a competitive or non competitive inhibitor

A

add substrate and if the rate of inhibition decreases then it’s a competitive inhibitor and if it stays the same it’s a non competitive inhibitor

66
Q

4 roles or ATP in plant cells

A

1) building up macromolecules
2) active transport
3) secretions (formation of lysosomes)
4) activation of molecules

67
Q

why is ATP described as a nucleotide derivative

A

because it is a modified form of a nucleotide

68
Q

which 2 groups are involved in the phosphodiester linkage

A

5’ phosphate and 3’ hydroxyl

69
Q

in what ways is ATP a suitable energy source for cells to use

A
  1. it is readily available as it releases energy instantaneously
  2. it releases relatively small amounts of energy so little is lost as heat
  3. can be rapidly re synthesised
  4. is not lost from cells
  5. phosphorylates other compounds making them more reactive
70
Q

why do humans need to synthesise more than their body mass of ATP each day

A

because ATP can’t be stored (is an immediate source) and it is only released in small amounts

Biology A level (20 decks)

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