BIOLOGY EDEXCEL IAL UNIT 2 - PAST PAPER QUESTION, Exams of Biology

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BIOLOGY: EDEXCEL IAL UNIT 2 - PAST PAPER

QUESTIONS

Similarities between mitochondria and chloroplasts. - answers- 1) surrounded by a double membrane.

2. circular dna Give one difference between an organ and a tissue. - answers- 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. - answers- both have cells that work together to carry out a specific function. Description of nucleus - answers- 1) double membran/ nuclear membrane.
3. nuclear pores.
4. nucleolus.
5. chromatin. Name the adaptation that allows sheep to learn to ignore sounds that have no importance to them. - answers- behavioural Name the adaptation that allows the formation of a sun tan when human skin is exposed to sunlight. - answers- physiological Describe and explain 2 adaptations of the human egg cell. - answers- 1) haploid/ 23 chromosomes.
6. so that diploid number can be restored at fertilisation.
7. lipid droplets/ food store.
8. supplies energy/ nutrients for division.
9. large cell surface area.
10. increased change of fertilisation.
11. cortical granules/ lysosomes/ zona pellucida.
12. to prevent polyspermy. Suggest why the tip of the root is used when observing mitosis. - answers- site of cell division/ mitosis/ actively dividing cells/ meristem. Suggest why cut root tips are placed in acid when preparing a root tip squash. - answers- 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. - answers- 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. Suggest why bioplastic is described as a more sustainable form of packaging than oil- based plastics. - answers- 1) bioplastic/ starch comes from plants.
6. plants/ starch are renewable.
7. oil-based plastic is from non-renewable resource/ eq. Suggest one environmental advantage of using biodegradable packaging. - answers- 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. - answers- 1) protein released from ribosome/ eq.
8. enters the rer.
9. becomes packaged into (rer) vesicles.
10. vesicles/ proteins move to golgi apparatus/ vesicles fuse with/ protein enters golgi.
11. protein modified/ carbohydrate added eq.
12. then become packaged into (secretory) vesicles/ eq.
13. vesicles move towards/ fuse with the cell surface membrane. Totipotent stem cells - answers- 1) undifferentiated/ unspecialised stem cell.
14. that can differentiate/ give rise to all/ any cell types.
15. can keep dividing. Suggest one risk to the person receiving stem cells? - answers- possible route to infection/ rejection by recipient/ increased risk of becoming cancerous. Genetic material in animal and plant cells. - answers- separate strands. Which cells are centrioles found in? - answers- animal cells only. Which cells have cell surface membranes? - answers- animal, plant and prokaryotic cells. In which cells are pits found? - answers- plant cells only. In which cells is the tonoplast present? - answers- plant cells only. In which cells are cell walls found in? - answers- plant and prokaryotic cells. What are the 80s ribosomes attached to in the rer? - answers- cisterna.

Suggest why a drug can be tested on rats before testing on humans. - answers- 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. Give the roles of water in a plant. - answers- 1) photosynthesis.
5. component of cytoplasm/ sap.
6. water as a solvent.
7. water as a transport medium.
8. involved in thermoregulation.
9. ref. To role in structural support.
10. ref. To involvement in hydrolysis.
11. ref. To turgor changes. Define double blind trial - answers- 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. - answers-
12. some people with drug and some without drug / eq.
13. use placebo/ description (e.g.sugar-coated dummy pill).
14. doctors and subjects do not know who is on drug or who is not /eq.
15. to see if new drug works better than placebo/ old drug/ eq.
16. reduces bias. Phase testing of drugs: Pre-clinical trials - answers- 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 - answers- 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 - answers- 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 - answers- 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 - answers- 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. - answers- 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. - answers- support:
7. ref. To lignin/ extra cellulose.
8. for strength.
9. ref. To rings/ spirals/ eq.
10. for strength/ flexibility. Explain how differential gene expression could result in the specialisation of cells. - answers- 1) ref. To correct stimulus e.g. Chemical.
11. some genes switched off/ on/ eq.
12. mrna from switched on/ eq. Genes.
13. mrna translated/ eq.
14. idea of protein synthesised/ different proteins produced.
15. 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. - answers- 1) ref. To sample/ explants from both tissues.
16. ref. To aseptic conditions/ named example.
17. grow cells into a callus/ eq.
18. ref. To growth regulators/ eq.
19. ref. To cells/ tissue can differentiate/ cells can become whole plants/ eq.
20. 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. - answers- 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. - answers- 1) flagellum/ eq.
6. overall shape e.g. Streamlined/ eq.
7. fewer mitochondria/ other organelles/ eq.
8. acrosome/ eq.
9. zona pellucida/ jelly layer/ eq.
10. cortical granules/ eq.
11. differences in food types/ eq.
12. sperm has less cytoplasm/ eq. Explain why digestive enzymes are released from the sperm when it reaches the egg cell. - answers- 1) enzymes digest the zone pellucid/ eq.
13. idea that sperm can get through to egg cell/ nucleus/ eq.
14. contact with receptor on zone pellucida (glycoprotein)/ jelly coat.
15. causes acrosome/ eq. To rupture/ open/ eq. Describe what happens in the egg cell once the sperm cell nucleus has entered it. - answers- 1) meiosis (ii) is completed/ eq.
16. male and female chromosomes come together/ both nuclei fuse/ eq.
17. cortical granules/ enzymes/ chemicals released/ eq.
18. bind with zone pellucida/ eq. Zone pellucida the thickens/ hardens/ eq.
19. 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. - answers- 1) to produce a zygote/ eq.
20. to produce original/ full complement of dna/ chromosomes/ genetic material/ diploid/ 2n/ eq.
21. 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. - answers- triploid endosperm nucleus. Suggest reasons why seeds need to be dried an then stored in cold conditions (for preservation). - answers- 1) inhibits germination/ eq.
22. idea of slowing down enzymes/ biochemical reactions.
23. slows down rate of decay/ microbial activity/ eq.
24. therefore prolongs seed survival.
25. idea that drying reduces freezing effect.

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