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Practice questions > Exampro high demand Cell biology > Flashcards

Exampro high demand Cell biology Flashcards

1
Q

Malaria is transmitted by mosquitos.

Male mosquitos can be sterilised so they are infertile.

The spread of malaria is reduced by releasing sterile mosquitos into the environment.

Explain how releasing sterile mosquitos reduces the spread of malaria.

A

reduces breeding / reproduction (in mosquitos)

(so) fewer mosquitos to bite people

or

(so) fewer mosquitos to pass on pathogen / protist

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2
Q

Malaria is transmitted by mosquitos.

Male mosquitos can be sterilised so they are infertile.

The spread of malaria is reduced by releasing sterile mosquitos into the environment.

Explain how releasing sterile mosquitos reduces the spread of malaria.

A

reduces breeding / reproduction (in mosquitos)

(so) fewer mosquitos to bite people

or

(so) fewer mosquitos to pass on pathogen / protist

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3
Q

How many micrometres in a metre

A

1,000,000

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4
Q

Name the piece of equipment used to view the virus.

A

(c)  electron microscope

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5
Q

(e)  Explain why plants infected with tobacco mosaic virus grow slowly.

A

discolouration in leaves

less chlorophyll in leaves

(so) reduced photosynthesis

(so) less glucose produced so less amino acids / proteins / cellulose made

allow (so) less glucose for respiration (so) less energy transferred for growth

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6
Q

What are the adavantages and disadvantages of statins

A

Advantages of statins

*   easy to take or not invasive (procedure)

*   decrease blood cholesterol

*   slow down build-up of fatty materials in arteries

*   maintain blood flow to heart muscle cells

*   low cost (compared to stent operation)

Disadvantages of statins

*   might be side effects of drug eg muscle pain

*   effects take time to happen

*   drug will need to be taken long term

*   might forget to take drug

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7
Q

What are the advantages and disadvantages of stents

A

Advantages of stent

*   blocked artery is held open

*   blood flow to heart muscle cells is increased

*   stent will remain in place for a long time

*   effect of stent is immediate

*   rapid recovery from operation

Disadvantages of stent

*   risk of infection from operation

*   risk of surgery eg heart attack or bleeding

*   risk of thrombosis or blood clot

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8
Q

Many people who survive a heart attack get out of breath easily when they exercise gently.

Explain why heart attack survivors get out of breath easily.

A

heart (muscle) cannot contract / pump as effectively / powerfully

(so) less blood pumped out of heart or to body (on each beat / contraction)

(so) less oxygen (reaches cells / body) for (aerobic) respiration

(so) more anaerobic respiration
so) breathing rate increases to supply more oxygen
(so) breathing rate increases to repay oxygen debt

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9
Q

Scientists have developed patches of beating heart cells to repair damaged heart tissue.

The patches are placed onto areas of the heart where cells have died. New cells grow to replace the dead cells.

The patches are made using a person’s own cells that are converted into stem cells.

(f)  Explain why stem cells are used to make the patches.

A

(f)  stem cells are undifferentiated cells

(therefore) can form heart (muscle) cells

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10
Q

The scientists could have used human embryonic stem cells to make the patches.

Give two advantages of using stem cells made from the person’s own cells, rather than using embryonic stem cells.

A

cells will not be rejected

*   no risk of damage to embryo and potential life is not destroyed

*   adult can give consent

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11
Q

(a)  Describe how water is transported from the soil to the atmosphere through a plant.

-4

A

(absorbed from soil) by osmosis through root hair (cells)

travels through xylem (vessels) to the leaves

lost through stomata (to atmosphere)

1

idea of driven by evaporation / transpiration

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12
Q

(c)  Explain one way sieve tube cells are specialised for their function.

A

have pores in the end walls

(so) dissolved sugars / food / contents can move from cell to cell
sap for dissolved sugars

no nucleus and few no sub-cellular structures (1)

to maximise space for movement of dissolved sugars / food / contents (1)

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13
Q

(d)  What does the structure of the companion cells suggest about the process that moves dissolved sugars through the phloem tissue?

A

active transport
requires energy because its an active process
(reason) cells have many mitochondria

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14
Q

(e)  Describe why it is important that dissolved sugars are moved both upwards and downwards in a plant.

A

sugars are made in the leaves by photosynthesis

all cells / tissues need sugar for respiration and as an energy source

(sugars) transported to meristems for growth / cell division / mitosis

(sugars) transported for storage as starch / fat / oil

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15
Q

Cells are the basic units of all forms of life.

(a) Describe four differences between a bacterial cell and a plant cell.

A

any four from:

*   bacterial cell is smaller (than a plant cell)

*   bacterial cell does not have chloroplasts (plant cell does)

*   bacterial cell does not have its DNA / genetic material inside a nucleus (plant cell does)

*   bacterial cell (may) have plasmids (plant cell does not)

*   bacterial cell does not have mitochondria (plant cell does)

*   cell wall in bacterial cells is not made of cellulose (cell wall in plant cells is)

*   bacterial cell does not have a large / permanent vacuole (plant cell does)

*   bacterial cell has smaller ribosomes (than plant cells)

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16
Q

Gonorrhoea is a bacterial disease.

A new vaccine is being developed against gonorrhoea.

Describe how a vaccine would work to prevent gonorrhoea.

A

Dead or inactive form of the pathogen is injected

Stimulated white blood cells to produce antibodies

MEmory cells are made

On re exposure specific, correct antibodies are made very quickly

Pathogens are killed and cannot produce a large enough population to cause the disease

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17
Q

(c) Explain how vaccinating chickens reduces the number of cases of salmonella food poisoning.

A

Fewer bacteria pathogens in chicken
So fewer bacteria pathogens ingested by humans
So fewer toxins produced

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18
Q

Give one way that the spread of salmonella food poisoning from one human to another is controlled.

Do not refer to vaccination in your answer.

A

Wash hand before preparing food
Wash hands after using teh toilet

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19
Q

Give two methods used to prevent people catching malaria.

Give a reason why each method works.

A

Method: insecticides

Reason: to kill mosquitos / vector

*   Method: (mosquito) nets

Reason: to avoid being bitten

*   Method: insect repellents

Reason: less likely to be bitten

*   Method: vaccination

Reason: so people are immune (to malaria)

*   Method: anti-malaria tablets

*   Reason: kills the pathogen / protis

20
Q

Describe the gradual change of the population of bacteria when supplied with nutrients

A

No change change in poulation size because no or limied cell division and reproduction

B)(B)

(rapid increase in population size) as cells dividing rapidly as (plentiful) supply of nutrients / food

allow rapid binary fission as (plentiful) supply of nutrients / food

1

(C)

(population size stays the same) as rate of cell death equals rate of cell division

1

(D)

(population size decreasing) as cells dying due to nutrients running out

or

(population size decreasing) as cells dying due to toxins / carbon dioxide / cell

21
Q

Explain why a multicellular organism cannot absorb all the nutrients it needs by diffusion through its outer surface.

A

(so) diffusion distance is longer in multicellular organism

(so) volume supplied by each unit of surface area is greater in multicellular organism

(so) diffusion rate per unit volume is slower in a multicellular organism

22
Q

(d)  Explain what the results in the table above show about how nitrate ions are absorbed.

A

more nitrate ions are absorbed in the presence of oxygen and faster

(which suggests) they are absorbed by active transport / uptake

which requires energy from respiration

23
Q

How are nitrates used in plants

A

nitrate ions are used with glucose

1

to form amino acids

1

(which are) used to synthesise proteins

24
Q

describe cell cycle -5 marks

A

cell growth

increase in number of organelles e.g. ribosomes / mitochondria
DNA replicates and two copies of each chromosome form*

stage 2 / mitosis

one set of chromosomes moves to each end of cell

chromosomes separate or are pulled apart by cell fibres

nucleus divides ito 2

stage 3- cytokineses

cytoplasm / cell membrane divides to form two (genetically) identical daughter cells

25
Q

Give the advanates and disadvantages of therapeutic cloning

A

Advantage
*   may be used to cure / treat (current / future) diseases

*   cells / tissues of any type could be produced

many cells produced

*   cells produced could be used for research

*   would reduce waiting time for organ transplants

Disadvantage
*   potential life is killed / destroyed

shortage of donors / eggs

*   egg donation / collection has risks

*   do not yet know risks /side effects of the procedure on the patient

may transfer (viral) infection

*   poor success rate to produce viable eggs / embryo

26
Q

Eukaryotic cells respire continuously to transfer energy.

(a) Give two uses of energy transferred by respiration in eukaryotes.

1

A
  • synthesis of new molecules

for active transport

  • to keep warm (in mammals / birds)
    muscle contraction/ movement
27
Q

Muscle cells and plant cells can respire anaerobically.

Compare the processes of anaerobic respiration in muscle and plant cells.

A

both occur without oxygen

1

both release (a small amount of) energy

1

muscle cells produce lactic acid but plant cells produce ethanol

1

muscle cells do not produce carbon dioxide but plant cells do

28
Q

What is oxygen debt

A

(d) the amount of oxygen needed to react with the lactic acid formed

29
Q

Whats the role of the xylem

Whats the role of te phloem

A

A- To trasnprt water and disolved mineral in the trasnpiration stream

TB) To tarsnport dissolved sugars using translocation

30
Q

Most plants have more stomata on the lower surface of a leaf than on the upper surface.

Explain why there are more stomata on the lower surface of a leaf.

A

cooler around lower surface

1

more humid around lower surface

allow converse argument for upper surface of leaf if qualified

1

(so) less water evaporated

31
Q

Plants need nitrate ions in order to make proteins.

A plant is growing in soil flooded with water.

Explain why the plant cannot absorb enough nitrate ions.

A

nitrate) ions are absorbed by active transport

1

(active transport) is the movement of ions against the concentration gradient

allow (active transport) is the movement of ions from a dilute to a more concentrated solution

1

(active transport) requires energy from respiration

1

(respiration) requires oxygen
no / little oxygen / air in water-logged soil

32
Q

(a) Antibiotics that disrupt the bacterial cell membrane often cause more side effects in humans compared with antibiotics that disrupt bacterial cell walls.

A

human cells have cell membrane

or

human cells have no cell wall

33
Q

Some antibiotics prevent ribosomes functioning.

Suggest how this damages the bacterium.

A

(b) can no longer synthesise proteins

34
Q

Plants exchange substances with the environment.

(a) Plant roots absorb water mainly by osmosis.
Plant roots absorb ions mainly by active transport.

Explain why roots need to use the two different methods to absorb water and ions.

A

solution in soil is more dilute (than in root cells)

concentration of water higher in the soil (than in root cells)

1

so water moves from the dilute to the more concentrated region

so water moves down (its) concentration gradient or water moves from a high concentration of water to a lower concentration

1

concentration of ions in soil less (than that in root cells)

1

so energy needed to move ions

or

ions are moved against concentration gradient

35
Q

The plant roots could not have absorbed these mineral ions by diffusion.

Explain why.

A

diffusion is down the concentration gradient

for a description of diffusion

ignore along / across gradients

1

to enter must go up / against the concentration gradient

accept by diffusion ions would leave the root

or

concentration higher in the root / plant

or

concentration lower in the soil

36
Q

(a) Describe two ways in which the cell in the strong sugar solution is different from the cell in distilled water.

A

smaller vacuole

  • smaller / less cytoplasm
  • cell membrane / cytoplasm not (fully) against cell wall

plasmolysed / flaccid / less turgid

or
cell membrane / cytoplasm (partly) pulled away from cell wall

i

space / liquid / sugar solution between cell

37
Q

(b) All of the sugars named in the table can be absorbed by diffusion when repiration doesnt occur explainw hy

A

all / the sugars / they can be absorbed when gut poisoned / with
cyanide or when no respiration

1

      (diffusion) does not need an energy supply
38
Q

Is it possible for the barley roots to take up sulfate ions from the soil by diffusion?

A

iffusion is down the concentration gradient

accept by diffusion ions would leave the root

1

      to enter must go up / against the concentration gradient
39
Q

The barley roots were able to take up more sulfate ions with oxygen than without oxygen.

     Explain how.
A

uptake) by active transport

1

     requires energy

     more energy from aerobic respiration
40
Q

Scientists may be allowed to use this technique to produce cells to treat some human diseases, but not to produce babies.

      Using information from the diagram, suggest an explanation for this.
A

cells used to treat diseases do not go on to produce a baby

  • produces identical cells for research
  • cells would not be rejected
  • allow cells can form different types of cells
  • (immature) egg contains only genetic information / DNA /
    genes / chromosomes from mother or there is only one parent
  • asexual / no mixing of genetic material / no sperm involved /
    no fertilisation or chemical causes development
  • baby is a clone
  • reference to ethical / moral / religious issues

allow ethically wrong
NB cloning is illegal gains 2 marks
ignore unnatural

  • risk of damage to the baby
41
Q

(ii) Explain the advantages of red blood cells passing through a capillary one at a time.

A

more oxygen released (to tissues) or
more oxygen taken up (from lungs)

1

     and any two from:
  • slows flow or more time available
  • shorter distance (for exchange) or close to cells / capillary wall
  • more surface area exposed
42
Q

(a) (i) After two hours they reweighed the discs after carefully blotting them first. Why did the students blot the potato before weighing it?

A

change in weight was due to changes in potato
or osmosis or not due to outside liquid

43
Q

A cook prepares a fresh fruit salad by cutting up a variety of fruits and placing them in a bowl with layers of sugar in between. After two hours the fruit is surrounded by syrup (concentrated sugar solution).

Explain, as fully as you can, why syrup (concentrated sugar solution) was produced after two hours.

A

ideas that
sugar has dissolved in moisture (on surface of fruit)
this solution more concentrated than solution inside fruit
osmosis / diffusion movement of water out of fruit
through partially permeable membrane (of fruit cells)

44
Q

(b) Why is sunlight necessary for photosynthesis?

A

provide enrgy

45
Q

Some of the sugars produced by photosynthesis are stored as starch in the roots.
Explain, as fully as you can, why it is an advantage to the plant to store carbohydrate as starch rather than as sugar.

A

starch insoluble therefore water not taken in by osmosis
or
sugar is soluble / has small molecules may diffuse out therefore lost

(ignore ref. to cells bursting)

      or starch has large molecules cannot diffuse therefore retained
46
Q

What is involved in active transport?

A

molecules / ions

do not credit mineral salts

      move(d) through / across the cell

      wall / membrane

      against (a / the) concentration

      gradient

      by a series of chemical

      reactions

      (because) diffusion cannot occur

      energy (required)

      (supplied by) respiration

      oxygen required for respiration (to occur)

[4]

Practice questions (9 decks)

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