BIOLOGY: EDEXCEL IAL UNIT 2 - PAST PAPER QUESTIONS

similarities between mitochondria and chloroplasts.

1) surrounded by a double membrane.

2) circular DNA

Give one difference between an organ and a tissue.

ø an organ has many functions, tissue has one.

ø an organ has many cell types, tissue only has one.

Suggest one way in which tissues and organs are similar.

both have cells that work together to carry out a specific function.

Description of nucleus

1) double membran/ nuclear membrane.

2) nuclear pores.

3) nucleolus.

4) chromatin.

Name the adaptation that allows sheep to learn to ignore sounds that have no importance to them.

behavioural

Name the adaptation that allows the formation of a sun tan when human skin is exposed to sunlight.

physiological

Describe and explain 2 adaptations of the human egg cell.

1) haploid/ 23 chromosomes.

2) so that diploid number can be restored at fertilisation.

3) lipid droplets/ food store.

4) supplies energy/ nutrients for division.

5) large cell surface area.

6) increased change of fertilisation.

7) cortical granules/ lysosomes/ zona pellucida.

8) to prevent polyspermy.

Suggest why the tip of the root is used when observing mitosis.

site of cell division/ mitosis/ actively dividing cells/ meristem.

Suggest why cut root tips are placed in acid when preparing a root tip squash.

to soften the material/ macerate/ break middle lamella/ eq.

The tip of the growing pollen time releases digestive enzymes into the style.

Suggest the role of these digestive enzymes in the growth of the pollen tube.

1) idea of breakdown/ digestion of style.

2) breaks down protein/ pectin/ middle lamella.

3) ref. to hydrolysis.

4) easier for pollen tube to grow/ reduced resistance.

5) supplies nutrients/ energy for pollen tube growth.

Give the roles of water in a plant.

1) photosynthesis.

2) component of cytoplasm/ sap.

3) water as a solvent.

4) water as a transport medium.

5) involved in thermoregulation.

6) ref. to role in structural support.

7) ref. to involvement in hydrolysis.

8) ref. to turgor changes.

Define double blind trial

a clinical drug trial where neither the doctor nor the patient knows whether the patient is receiving the new medicine, a control medicine or a placebo.

Explain what is meant by a double blind trial and suggest why its important.

1) some people with drug and some without drug / eq.

2) use placebo/ description (e.g.sugar-coated dummy pill).

3) doctors and subjects do not know who is on drug or who is not /eq.

4) to see if new drug works better than placebo/ old drug/ eq.

5) reduces bias.

Suggest why bioplastic is described as a more sustainable form of packaging than oil-based plastics.

1) bioplastic/ starch comes from plants.

2) plants/ starch are renewable.

3) oil-based plastic is from non-renewable resource/ eq.

Suggest one environmental advantage of using biodegradable packaging.

will not accumulate/ not contribute to landfill/ can be decomposed.

Explain how newly made proteins from the RER end up as glycoproteins on the cell surface membrane.

1) protein released from ribosome/ eq.

2) enters the rER.

3) becomes packaged into (rER) vesicles.

4) vesicles/ proteins move to Golgi apparatus/ vesicles fuse with/ protein enters Golgi.

5) protein modified/ carbohydrate added eq.

6) then become packaged into (secretory) vesicles/ eq.

7) vesicles move towards/ fuse with the cell surface membrane.

totipotent stem cells

1) undifferentiated/ unspecialised stem cell.

2) that can differentiate/ give rise to all/ any cell types.

3) can keep dividing.

Suggest one risk to the person receiving stem cells?

possible route to infection/ rejection by recipient/ increased risk of becoming cancerous.

Genetic material in animal and plant cells.

separate strands.

Which cells are centrioles found in?

animal cells only.

Which cells have cell surface membranes?

animal, plant and prokaryotic cells.

In which cells are pits found?

plant cells only.

In which cells is the tonoplast present?

plant cells only.

In which cells are cell walls found in?

plant and prokaryotic cells.

What are the 80s ribosomes attached to in the rER?

cisterna.

Suggest why a drug can be tested on rats before testing on humans.

1) rats have a similar metabolism.

2) no harm to humans.

3) idea of looking for potential toxicity/ adverse effect/ eq.

4) ref. to legal/ ethical issues.

Phase Testing of Drugs:

Pre-clinical trials

TESTING ON ANIMALS SUCH AS RATS:

. to monitor success of the drug uptake of target cells, if it is changed chemically and if its excreted safely.

. unethical to perform on humans.

. rats carry genes that are similar to those of humans - both suffer from similar diseases.

Phase Testing of Drugs:

Phase 1

TESTING ON SMALL NO. OF HUMANS:

. drug is trialled on a small number of healthy volunteers.

. safety is monitored.

Phase Testing of Drugs:

Phase 2

TESTING ON A SMALL NO. OF PATIENTS:

. drug is trialled on a small number of patients (volunteers) with the target disease.

. effectiveness monitored

Phase testing of Drugs:

Phase 3

DOUBLE-BLIND TRIAL TESTING ON HUMANS:

. drug is trialled on a large number of patients (volunteers) with target disease.

. safety + effectiveness is monitored.

. normally carried out as double-blind trials.

Double-blind trial

Neither the doctors or patient know if they are receiving a placebo or the actual drug - to rule out the placebo effect or deny patient from treatment.

Describe and explain how the xylem is adapted for the transport of water.

WATER TRANSPORT:

1) hollow tubes/ no living contents/ end walls broken down/ eq.

2) idea of allowing movement of water/ vertical movement.

3) ref. to waterproof material/ eq.

4) idea that it keeps water in the vessel e.g. less water lost.

5) pores/ pits/ eq.

6) to allow sideways movement of water/ eq.

Describe and explain how the xylem is adapted for the support in a plant.

SUPPORT:

1) ref. to lignin/ extra cellulose.

2) for strength.

3) ref. to rings/ spirals/ eq.

4) for strength/ flexibility.

Explain how differential gene expression could result in the specialisation of cells.

1) ref. to correct stimulus e.g. chemical.

2) some genes switched off/ on/ eq.

3) mRNA from switched on/ eq. genes.

4) mRNA translated/ eq.

5) idea of protein synthesised/ different proteins produced.

6) which permanently modifies cell (to become specialised)/ description of modification/ eq.

Describe how you would use a plant culture technique to show which of 2 tissues is totipotent.

1) ref. to sample/ explants from both tissues.

2) ref. to aseptic conditions/ named example.

3) grow cells into a callus/ eq.

4) ref. to growth regulators/ eq.

5) ref. to cells/ tissue can differentiate/ cells can become whole plants/ eq.

6) ref. to details of procedure e.g. agar/ leave for a suitable amount of time/ suitable controlled variable.

Describe the events that occur in prophase.

1) chromosomes/ chromatids condense/ become visible/ eq.

2) nuclear envelope/ eq. breaks down/ eq.

3) nucleolus/ eq. breaks down/ eq.

4) spindle fibres begin to form/ eq.

5) centrioles migrate to opposite poles/ eq.

Describe 3 structural differences between human sperm cell and egg cell.

1) flagellum/ eq.

2) overall shape e.g. streamlined/ eq.

3) fewer mitochondria/ other organelles/ eq.

4) acrosome/ eq.

5) zona pellucida/ jelly layer/ eq.

6) cortical granules/ eq.

7) differences in food types/ eq.

8) sperm has less cytoplasm/ eq.

Explain why digestive enzymes are released from the sperm when it reaches the egg cell.

1) enzymes digest the zone pellucid/ eq.

2) idea that sperm can get through to egg cell/ nucleus/ eq.

3) contact with receptor on zone pellucida (glycoprotein)/ jelly coat.

4) causes acrosome/ eq. to rupture/ open/ eq.

Describe what happens in the egg cell once the sperm cell nucleus has entered it.

1) meiosis (II) is completed/ eq.

2) male and female chromosomes come together/ both nuclei fuse/ eq.

3) cortical granules/ enzymes/ chemicals released/ eq.

4) bind with zone pellucida/ eq. zone pellucida the thickens/ hardens/ eq.

5) to form fertilisation membran/ to make cell impenetrable to other sperm/ prevents polyspermy/ egg cell membrane becomes positively charged/ eq.

Give the functions of fusion of male and female gametes in plant.

1) to produce a zygote/ eq.

2) to produce original/ full complement of DNA/ chromosomes/ genetic material/ diploid/ 2n/ eq.

3) to allow mixing of genes/ genetic material/ ref. to genetic variation/eq.

Name triploid structure of the male gamete fusing with the 2 polar nuclei.

triploid endosperm nucleus.

Suggest reasons why seeds need to be dried an then stored in cold conditions (for preservation).

1) inhibits germination/ eq.

2) idea of slowing down enzymes/ biochemical reactions.

3) slows down rate of decay/ microbial activity/ eq.

4) therefore prolongs seed survival.

5) idea that drying reduces freezing effect.

Suggest how calcium ions contribute to the increase in mass of a plant.

more/ larger cell / more cell walls/ calcium pectate/ middle lamella/ helps uptake of other ions.

Suggest what is meant by the phrase suitably prepared petri-dish.

1) ref. to agar.

2) idea that bacteria need to be distributed.

3) idea of a single/ named bacterial strain.

4) appropriate microbiological technique employed e.g. aseptic/ sterile plates