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A Level Biology Module 1 > Mark Schemes > Flashcards

Mark Schemes Flashcards

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1
Q

Differences between DNA and mRNA

IDENTIFY WHAT TOPIC THEY ARE TESTING YOUR KNOWLEDGE OF

RECORD RATES IN STANDARD FORM

A 
1. DNA double stranded/double helix and
mRNA single-stranded;
2. DNA (very) long and RNA short;
3. Thymine/T in DNA and uracil/U in RNA;
4. Deoxyribose in DNA and ribose in RNA;
5. DNA has base pairing and mRNA doesn’t/
DNA has hydrogen bonding and mRNA
doesn’t;
6. DNA has introns/non-coding sequences
and mRNA doesn’t;

Contrast requires both
parts of the statement

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2
Q

Induced fit model

A 
1. (before reaction) active site not
complementary to/does not fit
substrate;
2. Shape of active site changes as
substrate binds/as enzyme-
substrate complex forms;
3. Stressing/distorting/bending bonds
(in substrate leading to reaction);
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3
Q

Describing an enzyme controlled reaction graph

Why it levels off?

Always talk about substrate finishing, no more subtsrate, empty actice sites etc

A 
1. (Rate of) increase in concentration
of maltose slows as
substrate/starch is used up
OR
High initial rate as plenty of
starch/substrate/more E-S
complexes;
2. No increase after 25 minutes/at
end/levels off because no
substrate/starch left;
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4
Q

Describe how the structure of starch and cellulose molecules are related to their function

A 
Starch (max 3)
1. Helical/ spiral shape so compact;
2. Large (molecule)/insoluble so
osmotically inactive;
3. Branched so glucose is (easily)
released for respiration;
4. Large (molecule) so cannot leave
cell/cross cell-surface membrane;
Cellulose (max 3)
5. Long, straight/unbranched chains of
β glucose;
6. Joined by hydrogen bonding;
7. To form (micro/macro)fibrils;
8. Provides rigidity/strength;
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5
Q

Function of

  1. DNA helicase
  2. DNA polymerase
A
  1. DNA helicase – (unwinding DNA and) breaking
    hydrogen bonds / bonds between chains / bases /
    strands;
  2. DNA polymerase – joins (adjacent) nucleotides
    OR forms phosphodiester bond / sugar-
    phosphate backbone;
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6
Q

Differences between ATP and DNA nucleotide

A 
1. ATP has ribose and DNA nucleotide has
deoxyribose;
2. ATP has 3 phosphate (groups) and DNA
nucleotide has 1 phosphate (group);
3. ATP- base always adenine and in DNA
nucleotide base can be different / varies;
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7
Q

Properties of water

A 
Accept any three suitable properties e.g.:
 Is a metabolite
 Is a solvent
 Has a (relatively) high heat capacity
 Has a (relatively) large latent heat of
vaporisation / evaporation
 Has cohesion / hydrogen bonds between
molecules;;;
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8
Q

Properties of starch that make it good for storage

A

Any two from:
1. Insoluble (in water), so doesn’t affect water
potential;
2. Branched / coiled / (α-)helix, so makes
molecule compact;
OR
Branched / coiled / (α-)helix so can fit many
(molecules) in small area;
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

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9
Q

Features of DNA and their importance in semi-conservative DNA replication

A

Weak / easily broken hydrogen bonds between
bases allow two strands to separate / unzip;
2. Two strands, so both can act as templates;
3. Complementary base pairing allows accurate
replication;

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10
Q

Emulsion Test

A
  1. (Mix / shake sample) with ethanol, then water;

2. White / milky (emulsion);

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11
Q

Combined action of endopeptidases and exopeptidases more efficient. Why?

A

Endopeptidases hydrolyse internal (peptide
bonds)
OR
Exopeptidases remove amino
acids/hydrolyse (bonds) at end(s);
2. More ends or increase in surface area (for
exopeptidases);

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12
Q

Respiratory Inhibitor

A

Something that inhibits respiration.

No respiration = no ATP produced

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13
Q

Thin pieces of leaf tissue examined using an optical microscope. Why is it important that leaves are thin.

A
  1. Single/few layer(s) of cells;

2. So light can pass through;

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14
Q

Why is it important that the student counted stomata in sevral parts of leaf tissue?

A
  1. Distribution may not be uniform
    OR
    So it is a representative sample;
  2. To obtain a (reliable) mean;
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15
Q

Read questions carefully

A

SUGGEST AND EXPLAIN

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16
Q

Xerophytic Adaptations

A 
1. Hairs so ‘trap’ water vapour
and water potential gradient
decreased;
2. Stomata in pits/grooves so
‘trap’ water vapour and water
potential gradient decreased;
3. Thick (cuticle/waxy) layer so
increases diffusion distance;
4. Waxy layer/cuticle so reduces
evaporation/transpiration.
5. Rolled/folded/curled leaves so
‘trap’ water vapour and water
potential gradient decreased;
6. Spines/needles so reduces
surface area to volume ratio;
17
Q

Rate of water uptake of plant not always same as transpiration rate

A 
1. Water used for
support/turgidity;
2. Water used in photosynthesis;
3. Water used in hydrolysis;
4. Water produced during
respiration;
18
Q

Organisms with no gas exhange system. How are they adapted?

A 
1. Thin/small so short diffusion
pathway;
2. Flat/long/small/thin so large surface
area to volume ratio/surface area :
volume;
19
Q

Organism living in area with less oxygen. Look at the graph and explain how its haemoglobin allows it to survive in low pO2 conditions?

AS 2016 PAPER 2 3.3

A
  1. High/50% saturation (with oxygen)
    below (pO2 of) 0.2 kPa;
  2. (Oxygen) for respiration;
20
Q

AS 2016 PAPER 2 3.4

A 
1. Water potential higher in worm
OR
Lower water potential in seawater;
2. Water leaves by osmosis (and
worm dies)
21
Q

When investigating conditions in people

AS 2016 PAPER 2 6.1

A
  1. Large sample size;
  2. Individuals chosen at random;
  3. Are healthy;
  4. Equal number of males and
    females;
  5. Repeat readings;
22
Q

Low FEV1

A
  1. Less carbon dioxide removed;
  2. Less oxygen (uptake/in blood);
  3. Less (aerobic) respiration/ATP
    OR
    (More) anaerobic respiration
23
Q

Translocation

A
  1. (At source) sucrose is actively
    (transported) into the phloem/sieve
    element/tube;
  2. By companion/transfer cells;
  3. Lowers water potential in
    phloem/sieve element/tube and
    water enters by osmosis;
  4. (Produces) high (hydrostatic)
    pressure;
  5. Mass flow/transport towards
    sink/roots/storage tissue;
  6. At sink/roots sugars are
    removed/unloaded;

A Level Biology Module 1 (22 decks)

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