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Biology AS > 1. Biological Molecules > Flashcards

1. Biological Molecules Flashcards

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1
Q

Describe how calibration curve is carried out:

A

-reducing tests of known glucose concentrations carried out (6 different concentration)
-colorimeter used on all of them to quantify amount of glucose
-reducing test done on unknown concentration solution
-colorimeter used to quantify by comparing results of unknown to known solutions to predict concentration of unknown

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2
Q

Two molecules of glucose can react during a ……. ……. to form a ……. …… and lose a water molecule, forming a disaccharide. This forms a …. …..

A

Two molecules of glucose can react during a condensation reaction to form a glycosidic bond and lose a water molecule, forming a disaccharide.
This forms a 1-4 bond.

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3
Q

A primary structure is ……. ….. (3)

A
  1. specific sequence of amino acids
  2. joined by peptide bonds
  3. by cond. reaction
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4
Q

A secondary structure is

A

-folding of the polypeptide chain due to h-bonds betw/ NH and C=O ➜ folds into alpha helix / beta pleated sheet

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5
Q

Tertiary structure:

A
  • further folding into 3D shape betw/ multiple amino acids joined by pep bonds
  • due to bonds forming betw/ diff R groups in amino chain (h-bonds, ionic, disulfide)
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6
Q

quaternary structure:

A
  • folding & bonding betw/ >=2 polypep chains
  • forms fibrous/ globular structures
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7
Q

cellulose is a polymer of

A

beta glucose

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8
Q

Define reducing sugars:

A

Reducing sugars can donate an electron to another molecule, eg:
-all monosaccharides
-maltose, lactose

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9
Q

describe how a triglyceride is formed

A
  • one molecule of glycerol and 3 fatty acids
  • condensation reaction, 3 molecules of water removed
    forms ester bonds
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10
Q

glycogen is made w

A

alpha glucose

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11
Q

describe test for lipid

A
  • add ethanol
  • add water
  • shake
  • white emulsion
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12
Q

Describe the structure of starch and explain how it’s adapted for its function in cells: (6 marks)

A
  • coiled in a tight helix
    ➔makes it compact and allows for maximum glucose storage to be used as energy during respiration
  • Insoluble in water
    ➔doesn’t affect water potential so doesn’t cause water to move into the cells through osmosis
  • Large polymers
    ➔can’t diffuse out of the cell membrane
  • has a lot of ends from a lot of branches
    ➔many ends for enzymes to act on during hydrolysis, starch is broken down rapidly
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13
Q

Explain one other effect on the plant caused by the evaporation of water from its leaves

A
  1. Cools leaves
  2. Evaporation uses heat from leaves
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14
Q

Explain why a change in primary structure can affect the structure of a protein: (4)

A
  • means diff amino acids in the sequence
  • different R groups in different places
  • changes in bonding in tertiary structure between R groups (ionic, h-bonds, disulfide)
  • protein will fold into a different shape and function will change
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15
Q

Explain why this column of water doesn’t break (3 marks)

A

Water molecules polar
Form hydrogen bonds betw water molecules
Cohesion prevents breakage of columns

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16
Q

Give properties of water that are important in Biology (5)

A
  • Polar molecules: Acts as an universal solvent
  • Metabolite: Involved in metabolic reactions such as condensation and hydrolysis
  • Water molecules stick together, cohesive bonds between water molecules: Provides surface tension/ prevents columns of water breaking
  • High specific heat capacity: Reduces fluctuations in temperature (of water bodies)
  • High latent heat of evaporation: Evaporation of small amount of water cools an organism
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17
Q

how is cellulose adapted for function in plant cells

A
  • straight and long chains
  • many hydrogen bonds between chains form fibrils
  • makes cell wall very strong, resistant to osmotic pressure
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18
Q

how is starch adapted for function in plant cells

A
  1. Insoluble;
  2. Don’t affect water potential;
  3. Helical;
  4. Compact;
  5. Large molecule;
  6. Cannot leave cell.
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19
Q

If there is a reducing sugar present then:

A

The Cu2+ from the Benedicts solution will gain an electron and form C+ ions.
- These form a red precipitate.
- If concentration of reducing sugars is low then: less precipitate, more Cu2+ ions left in the solution (less transmission, more absorption)
- Solution will be bluer

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20
Q

lactose formed by cond. of

A

glucose and galactose

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21
Q

2 major stores of glycogen in humans

A

liver and muscle cells

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22
Q

Test for non-reducing sugars: (sucrose)

A
  • take boiling tube, add dilute HCl (to hydrolise)
  • add Sodium hydrogen carbonate (to neutralise it)
    (pH should be 7)
  • add Ben’s solution
  • heat by putting boiling tube in beaker w/ boiling water
    observe color change
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23
Q

hydrolysis reaction to reverse a peptide bond is carried out by

A

protease enzymes in digestive system

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24
Q

what is a monomer

A

small repeating unit from which a larger molecule is made

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25
Q

Why is starch a good storage molecule (4)

A
  1. Insoluble, doesn’t affect water potential;
  2. Branched / coiled so makes molecule compact;
  3. Polymer of (α-)glucose so provides glucose for respiration;
  4. Branched / more ends for fast breakdown / enzyme action;
26
Q

benefits of immobilised enzymes: (5)

A
  • allows for continuous process
  • avoids end product inhibition
  • doesn’t need to seperate enzyme form product
  • makes enzymes more stable
  • enzymes can be reused
27
Q

Describe process of non-competitive inhibitor:

A
  • doesn’t bind to active site
  • binds to an allosteric site
  • changes the tertiary structure of enzyme
  • shape of active site changes, no longer complimentary to substrate
  • sub can’t bind to form E-S complex, reduces rate of reaction
28
Q

Processes in the cell that require energy from hydrolisis of ATP to ADP:

A

muscle contraction
active transport
formation of large molecules eg. proteins

29
Q

What is an enzyme?

A
  • biological catalysts
  • globular proteins
  • have specific tertiary structures that shape their active site
30
Q

compare and contrast structure of starch and cellulose

A

SIMILARITIES:
- both are polysacs
- both contain glycosidic bonds

DIFFERENCES:
- starch, alpha but cellulose, beta
- starch has mainly 1-4 and some 1-6 glyco bonds but cellulose only has 1-4
- starch forms coiled structure but cellulose forms linear fibre

31
Q

explain 5 properties in water that make it useful in organisms (5)

A
  • cohesion - supports water columns & provides surface ten
  • high spec heat - buffers temp changes
  • large latent - provides cooling effect through evap
  • metabolite in cond. reactions
  • solvent allows transport of substances
32
Q

ATP useful properties: (4)

A
  • releases energy in small amounts
  • broken down in one step
    makes energy rapidly available
  • phosphorylates
    makes substances more reactive / lowers act. en.
  • reformed / made again
33
Q

explain what causes arrangement of phosphate bilayer (2)

A
  • phosphate head hydrophilic
  • fatty acid tail hydrophobic
34
Q

what is saturated

A

a molecule with only single bonds betw/ carbon atoms

35
Q

desc. how monomer join to form primary structure of protein (3)

A
  • condensation reaction betw/ amino acids
  • forming peptide bond
  • creating specific sequence of amino acids
36
Q

curve levels off because

A

all substrate used up

37
Q

Why does rate of reaction increase when sugar lyxose is added? (4)

A
  • lyxose cause tertiary structure of active site to change
  • active site changes shape to become comp. to substrate
  • more successful collisions betw/ sub & active site, more ES complexes fomed
  • activation energy reduced
38
Q

Change from optimum pH effect on ROR (3)

A
  • change in charges of R groups
  • change in tertiary structure of enzyme so shape of active site
  • less ES complexes formed
39
Q

change in pH changes…

A
  • charges of R groups
  • ionic and hydrogen bonds disrupted
  • tertiary structure of active site changes
  • less successful collisions betw/ sub & a.s
  • less ESc formed
40
Q

describe test for lipids

A
  • dissolve in ethanol
  • add water, shake
  • white emulsion
41
Q

Contast saturated and unsaturated fatty acids (4)

A

saturated
* only single bonds betw/ carbon atoms
* straight chain molecules
* higher melting point
* found in animal fats

unsaturated:
* contain C=C
* kinked molecule
* lower melting point
* found in plant cells

42
Q

relate structure of 3glyceride w/ function

A
  • high energy:mass ratio = high calorific value from oxidation (energy store)
  • insoluble hydrocarb chain = no effect on water potential and used for waterproofing
  • slow conductor of heat;thermal insulation
  • less dense than water; buoyancy of aquatic animals
43
Q

desc. fatty acid

A

hydrocarbon+COOH

44
Q

desc glycerol

A

hydrocarb+OH instead of H on one side

45
Q

process of ester bond

A

esterification

46
Q

triglycerides are

A
  • hydrophobic
  • non polar
  • don’t affect water potential
47
Q

Describe the induced fit hypothesis.

A
  • Initially, the active site isn’t quite the right shape for the substrate to fit in.
  • The substrate induces a change in the shape of the active site of the enzyme.
  • The substrate is able to fit better into the active site of the enzyme.
  • An enzyme-substrate complex is formed.
  • Reaction occurs.
  • Enzyme-product complex is formed.
  • Product released from enzyme, and enzyme remains unchanged.
48
Q

2 scientists who proposed DNA replication

A

watson & crick

49
Q

explain difference in structure of starch and cellulose molecules

A
  • cellulose formed from beta glucose but starch formed from alpha glucose
  • position of H and OH group on carbon atom 1 inverted
50
Q

explain how a starch molecule is adapted for its function (2)

A
  1. helical
  2. compact
    OR
  3. large molecule
  4. cannot diffuse out of cell
    OR
  5. insoluble in water
  6. doesnt affect water potential
51
Q

Water is a major component of cells. It has several properties that are important in biology. In particular, water:

A
  • is a metabolite in many metabolic reactions, including condensation and hydrolysis reactions
  • is an important solvent in which metabolic reactions occur
  • has a relatively high heat capacity, buffering changes in temperature
  • has a relatively large latent heat of vaporisation, providing a cooling effect with little loss of water through evaporation
  • has strong cohesion between water molecules; this supports columns of water in the tube-like transport cells of plants and produces surface tension where water meets air.
52
Q

Describe how a gene is a code for the production of a polypeptide (3)

A
  • base sequence
  • in triplets
  • determines sequence of amino acids
53
Q

Define the term exon (1)

A

base sequence coding for sequence of amino acids

54
Q

Define non-coding base sequences and describe where they are found in the genome (2)

A
  • DNA that doesn’t code for amino acids
  • found betw/ genes
55
Q

Describe how a peptide bond forms between 2 amino acids to form a dipeptide: (2)

A
  • condensation
  • betw/ amine and carboxyl
56
Q

Features of starch that make it a good storage molecule (5)

A
  1. Insoluble, so doesn’t affect water potential;
  2. Branched / coiled, so makes molecule compact;
  3. Polymer of (α-)glucose so provides glucose for respiration;
  4. Branched / more ends for fast breakdown / enzyme action;
  5. Large (molecule), so can’t cross the cell membrane
57
Q

in enzyme questions ALWAYS mention

A

enzyme-substrate complexes

58
Q

Describe how the structure of the protein depends on the amino acids it contains. (5)

A
  1. Structure is determined by (relative) position of amino acids
  2. Primary structure is sequence/order of amino acids;
  3. Secondary structure formed by hydrogen bonding
  4. Tertiary structure formed by interactions (between R groups);
  5. Creates active site in enzymes
  6. Quaternary structure contains >1 polypeptide chain
59
Q

Why is rate of reaction lower at pH8 than pH6? (4)

A

pH6 is closer to the optimum

  • at PH8 there are more OH- groups, this changes the charges on R groups
  • tertiary structure of the enzyme changes
  • so shape of active site changes
  • fewer ES complexes formed at pH 8
60
Q

What is the advantage of giving the results of the initial v final mass as ratios? (2)

A
  • allows comparison
  • as initial masses were different
61
Q
A

Biology AS (15 decks)

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