unit 1 - biological molecules Flashcards
1
Q
what is hydrolysis?
A
- breaks a chemical bonds between two molecules;
- using water
2
Q
what is a condensation reaction?
A
- creates a chemical bond
- removing a molecule of water
3
Q
glycogen - glycogen structure (3)
A
- polysaccharide of a-glucose
- joined by glycosidic bond
- branched structure
4
Q
glycogen - glycogen compared with cellulose (4)
A
- cellulose is made up of b-glucose (monomers) and glycogen is made up of a-glucose (monomers)
- cellulose molecule has straight chain and glycogen is branched
- cellulose molecule has straight chain and glycogen is coiled
- glycogen has 1,4 and 1,6 glycosidic bonds and cellulose has only 1,4 glycosidic bonds
5
Q
glycogen - glycogen structure related to function (5)
A
- insoluble (in water), so doesn’t affect water potential
- branched/coiled/a-helix, so makes molecule compact
- polymer of a-glucose so provides glucose for respiration
- branched/more ends for fast breakdown/enzyme action
- large molecule so cant cross the cell membrane
6
Q
starch - relate 3 properties to its function (6)
A
- insoluble
- don’t affect water potential
- helical
- compact
- large molecule
- cannot leave cell
7
Q
test for reducing sugar
A
- heat with benedicts reagent
- colour change from blue to brick- red
8
Q
test for non reducing sugar
A
- heat with benedicts reagent and no colour change
- boil with acid (HCL) and then neutralise with (NaHCO3)
- re-heat with benedicts reagent and colour change from blue to brick-red
9
Q
test for starch
A
- add iodine in potassium iodide solution
- colour change from brown to blue-black
10
Q
how are triglycerides formed
A
- one glycerol and three fatty acids
- condensation reaction and removal of three molecules of water
- ester bonds formed
11
Q
phospholipids compared with triglycerides (8)
A
- both contain ester bonds (between glycerol and fatty acids
- both contain glycerol
- fatty acids on both may be saturated or unsaturated
- both are insoluble in water
- both contain C,H and O but phospholipids also contain P
- triglyceride has three fatty acids and phospholipid has two fatty acids and phosphate group
- triglyceride are hydrophobic/non-polar and phospholipids have hydrophillic/polar and hydrophobic region
- phospholipid form bilayer but triglycerides dont
12
Q
describe how an ester bond is formed in a phospholipid molecule
A
- condensation reaction
- between glycerol and fatty acid
13
Q
test for a lipid
A
- mix sample with ethanol then water
- white milky emulsion
14
Q
protein - protein structure (70
A
- polymer of amino acids
- joined by peptide bonds
- formed by condensation
- primary structure is order of amino acids
- secondary structure is folding of polypeptide chain due to hydrogen bonding into alpha helix or beta pleated sheet
- tertiary structure is 3D folding due to hydrogen and bonding and ionic/disulphide bonds between r-groups
- quarternary structure is more than one polypeptide chains
15
Q
test for a protein
A
- add biuret reagent to the sample
- colour change to lilac
16
Q
enzymes - induced fit model (3)
A
- before reaction active site is not complementary
- shape of active site changes as substrate binds/ as e-s complex forms
- stressing in the bonds in substrate lead to reaction
17
Q
enzymes - increased temperature and reaction rate (4)
A
- particles have more kinetic energy
- therefore they move more
- so there are more collisions between substrates and active sites
- so more ES complexes form
18
Q
enzymes - denaturation (5)
A
- heat above optimum temperature breaks hydrogen bonds
- this causes the tertiary structure to unfold
- so the active site changes shape
- substrate can no longer bind to the active site, as its no longer complementary
- fewer ES complexes form
19
Q
enzymes - effect of changes in ph
A
- ionic bonds holding tertiary structure break
- active site distorts and substrate no longer binds to active site
- charges on amino acids in active site affected
- fewer ES complexes form
20
Q
enzymes - concentration of substrate (2)
A
- increase in concentration of product slows as substrate is used up
- until no substrate left
21
Q
enzymes - competitive vs non competitive inhibition (2)
A
- competitive inhibitor binds to active site of enzyme but non-competitive inhibitor binds at allosteric site
- competitive inhibitor does not change shape of active site but non-competitive does
22
Q
describe DNA replication (6)
A
- DNA helicase breaks hydrogen bonds and unwinds double helix
- both strands act as templates
- free DNA nucleotides line up in complementary pairs
- DNA polymerase joins nucleotides of new strands
- forming phosphodiester bonds
- each new DNA molecule consists of one old and one new strand of DNA
23
Q
describe the structure of DNA (5)
A
- polymer of nucleotides
- each nucleotide formed from deoxyribose, phosphate group and nitrogenous base
- phosphodiester bonds between nucleotides
- double helix held by hydrogen bonds
- hydrogen bonds between complementary base pairs
24
Q
describe and explain how the structure of DNA allows accurate replication (4)
A
- two strands therefore semi-conservative replication possible
2.hydrogen bonds hold strands together - hydrogen bonds are weak allow strands to separate
- bases exposed act as template can be copied
- DNA one parent strand and one new strand
- A+T, C+G
25
Q
describe how a phosphodiester bond is formed between two nucleotides in a DNA molecule (3)
A
- condensation reaction
- between phosphate and deoxyribose
- catalysed by DNA polymerase
26
Q
ATP - uses and properties as an energy source (5)
A
- releases relative small amount of energy/little energy lost as heat
- releases energy instantaneously
- phosphorylates other compounds, making them more reactive
- can be rapidly re-synthesised
- does not leave cells
27
Q
ATP - structure compared with DNA nucleotide (3)
A
- ATP has ribose and DNA has deoxyribose
- ATP has 3 phosphates and DNA nucleotide has one phosphate
- base is always adenine in ATP and bases vary in DNA nucleotide (A,C,G or T)
28
Q
water - properties that make water important for organisms (6)
A
- metabolite in condensation/ hydrolysis/photosynthesis/respiration
- A solvent so metabolic reactions can occur
- high heat capacity so buffers changes in temperature
- large latent heat of vaporisation so provides a cooling effect (through evaporation)
- cohesion between water molecules so supports columns of water in plants
- cohesion between water so produces surface tension supporting organisms
