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Biology A-level > Chapter 2: biological molecules > Flashcards

Chapter 2: biological molecules Flashcards

1
Q

reagent used for reducing sugars

A

Benedict’s reagent

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2
Q

reducing sugars test

A
  • Benedict’s reagent contains copper ions
  • when heated with reducing sugars, the copper ions are reduced to copper compounds
  • the colour changes from blue to brown
  • this test can be used for a range of concentrations of sugars
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3
Q

reagent used for non-reducing sugars

A

Benedict’s reagent, following acid hydrolysis

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4
Q

non-reducing sugars test

A
  • sucrose is a commonly occurring non-reducing sugar
  • when heated with dilute acid, sucrose is hydrolysed into its constituent monosaccarides, glucose and fructose, which are both reducing sugars
  • excess acid is then neutralised by the addition of sodium hydrogen carbonate and the mixture is then tested with Benedict’s reagent. This will show the production of reducing sugars
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5
Q

reagent used for starch

A

iodine in potassium iodide solution

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6
Q

starch test

A

iodine solution turns from brown to blue black in the presence of starch

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7
Q

proteins reagent

A

biuret reagent

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8
Q

‘macromolecule’ definition

A

a large biological molecule

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9
Q

‘monomer’ definition

A

a simple molecule which is used as a basic building block for the synthesis of a polymer

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10
Q

‘polymer’ definition

A

a giant molecule made from many similar repeating subunits joined together in a chain

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11
Q

monosaccharides function

A
  • source of energy in respiration

- building blocks for larger molecules

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12
Q

monosaccharide definition

A

a molecule consisting of a single sugar unit with the general formula (CH20)n

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13
Q

‘disaccharide’ definition

A

a sugar molecule consisting of two monosaccharides joined together vy a glycosidic bond

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14
Q

‘polysaccharide’ definition

A

a polymer whose subunits are monosaccharides joined together by glycosidic bonds

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15
Q

what is starch made up of?

A

a mixture of amylose and amylopectin

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16
Q

what is the storage carbohydrate in animal cells?

A

glycogen

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17
Q

why are hydrogen bonds strong?

A

they are individually weak but collectively they provide enormous strength

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18
Q

describe the characteristics of cellulose fibres:

A
  • very high tensile strength so that they can withstand the high pressures caused by osmosis
  • freely permeable, allowing water and solutes to reach or leave the cell surface membrane
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19
Q

what chemical group do fatty acids contain?

A

-COOH

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20
Q

acid + alcohol produces what chemical?

A

an ester

21
Q

what is the bond between an acid and an alcohol called?

A

an ester bond

22
Q

what are the most common lipids?

A

triglycerides

23
Q

describe the solubility of triglycerides

A

insoluble in water but soluble in certain organic solvents

24
Q

describe the roles of triglycerides

A
  • energy reserves
  • insulator against loss of heat
  • metabolic source of water
25
Q

describe the unusual property of phospholipids

A
  • one end is soluble in water

- one of the three fatty acid molecules is replaced by a phosphate group, which is polar

26
Q

describe the phosphate group in a phospholipid in one word

A

hydrophilic (water-loving)

27
Q

describe three functions of proteins

A
  • enzymes
  • some hormones (eg insulin)
  • antibodies
28
Q

describe the general structure of all amino acids

A
  • central carbon atom
  • bonded to an amine group NH2
  • and a carboxylic acid group, COOH
29
Q

how do amino acids differ from each other?

A

by the R group

30
Q

when two amino acids join together, they form a…

A

peptide bond

31
Q

what is a polypeptide?

A

a molecule made up of many amino acids linked together by peptide bonds

32
Q

where are polypeptides formed?

A

in the ribosomes

33
Q

‘primary structure’ definition

A

the sequence of amino acids in a polypeptide or protein

34
Q

‘secondary structure’ definition

A

the structure of a protein molecule resulting from the regular coiling or folding of the chain of amino acids

35
Q

‘tertiary structure’ definition

A

the compact structure of a protein molecule resulting from the dimensional coiling of the already-folded chain of amino acids

36
Q

hydrogen bonds form between…

A

strongly polar groups eg -NH-, -CO- and -OH groups

37
Q

disulfide bonds form between…

A

cysteine molecules

38
Q

disulfide bonds are…

A

strong covalent bonds

39
Q

ionic bonds form between…

A
  • ionised amine (NH3+) groups

- ionised carboxylic acis (COO-) groups

40
Q

how are disulfide bonds broken?

A

by reducing agents

41
Q

how are ionic bonds broken?

A

by pH changes

42
Q

weak hydrophobic interactions occur between…

A

non-polar R groups

43
Q

what structure does haemoglobin have?

A

a quaternary structure

44
Q

describe the structure of haemoglobin

A
  • four polypeptide chains
  • each chain is a protein called a globin
  • two chains are alpha-globin, two are beta-globin
  • each chain contains a haem group (a prosthetic group)
  • each haem group contains an iron atoms
  • one 02 molecule can bind with each iron atom
45
Q

describe the structure of collagen

A
  • three polypeptide chains wound round each other
  • every third amino acid in each polypeptide is glycine
  • covalent bonds form between the R groups of amino acids lying next to each other
  • these cross links form fibrils
  • they form fibres
46
Q

water as a solvent

A
  • water molecules are attracted to the ions and polar molecules
  • they collect around and separate them
47
Q

the high specific heat capacity of water

A
  • the amount of heat required to raise its temperature by a given amount
  • hydrogen bonds need to be broken to allow free movement
48
Q

high latent heat of vaporisation of water

A
  • a measure of the heat energy needed to vaporise a liquid, changing it from a liquid to a gas
  • it means that living organisms can use evaporation as a cooling system
49
Q

high surface tension and cohesion of water

A
  • the molecules tend to stick together
  • water can move through long, unbroken columns through the vascular tissue in plants
  • the surface of water is a habitat for small organisms

Biology A-level (18 decks)

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