Science questions, chapter 2
Cell as the Basic Unit of Life
43 marks. Use Practice to check each answer as you go, or Exam to answer everything against the clock first.
Section A: objective questions
12 marksChoose the best answer for each question.
1
In 1665, a scientist looked at a thin piece of cork through a microscope and named the small box-shaped structures he saw "cells". Who was he?
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B
Robert Hooke observed cork cells in 1665. Antonie van Leeuwenhoek observed moving microorganisms in rain water in 1674.
2
Which solution is used to stain cheek cells so that they can be seen clearly under a microscope?
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C
Methylene blue is used for cheek (animal) cells. Iodine solution is used for onion (plant) cells.
3
When preparing a slide, the cover glass is lowered slowly onto the specimen using a mounting needle. Why?
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A
Lowering the cover glass slowly from one side pushes the air out, so no air bubbles are trapped over the cells. Filter paper absorbs excess stain.
4
Diagram 1 shows an animal cell. What is the function of structure Q?
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D
Q is the nucleus, which controls all activities in the cell. P is the cytoplasm and R is a mitochondrion.
5
Which structures are found in both animal cells and plant cells?
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D
Both cells have a nucleus, cell membrane, cytoplasm and mitochondria. The cell wall, chloroplast and large vacuole are found only in plant cells.
6
Diagram 2 shows an organism found in a drop of pond water. Which statement about it is correct?
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B
This is Euglena, a unicellular organism. Its chloroplasts let it make food using sunlight like a plant, and its flagellum lets it move like an animal.
7
Diagram 3 shows three types of cells, P, Q and R. Which cell helps the heart muscle to contract and relax?
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A
Q is a muscle cell; muscle cells contract and relax to enable movement. P is a red blood cell and R is epithelium (a protective layer).
8
Which feature helps a red blood cell to transport oxygen?
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C
Haemoglobin carries oxygen, and the biconcave disc shape increases the surface area. Long fibres belong to nerve cells; changing shape to surround germs is what white blood cells do.
9
Which sequence shows the correct order of cell organisation in a multicellular organism?
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D
Cells with the same function form a tissue; different tissues form an organ; related organs form a system; all systems form an organism.
10
Which word equation represents cell respiration?
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A
Cell respiration uses glucose and oxygen and produces carbon dioxide, water and energy. Option B is photosynthesis.
11
In the test for starch, why is the leaf placed in a boiling tube of ethanol?
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C
Ethanol removes the chlorophyll so the colour change of the iodine can be seen clearly. Boiling water breaks the cell walls; iodine (not ethanol) shows starch.
12
Which statement is correct about a green plant at night, when there is no light?
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B
Photosynthesis occurs only in the presence of light, but cell respiration occurs at all times. So at night the plant only respires.
Section B: structured questions
31 marksAnswer all questions. Write your answers in the spaces provided.
13
Diagram 4 shows a plant cell.
[1 mark]
(a)Name structure P.
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- Cell wall1
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[1 mark]
(b)State the function of structure Q.
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- Absorbs light energy for photosynthesis / contains chlorophyll that absorbs light1
Q is a chloroplast.
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[2 marks]
(c)Name structure R and state its function.
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- Vacuole1
- Provides support to the cell when it is filled with cell sap1
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[1 mark]
(d)Structure S controls all the activities in the cell. What is S?
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Nucleus
The nucleus controls all activities in the cell and contains the chromosomes (DNA).
14
Aina wants to observe onion cells and cheek cells under a microscope.
[1 mark]
(a)Which solution should she use to stain the onion cells?
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Iodine solution
Iodine is used for onion (plant) cells; methylene blue for cheek (animal) cells.
[1 mark]
(b)Why must the cells be stained?
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- Cells are almost colourless, so staining makes the structures (e.g. nucleus) clearly visible1
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[1 mark]
(c)State one difference between the onion cells and the cheek cells that she will see.
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Any 1 points
- Onion cells have a fixed (box-like) shape but cheek cells have no fixed shape1
- Onion cells have a cell wall but cheek cells do not1
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15
Diagram 5 shows three types of human cells, P, Q and R. Choose the name of each cell.
[1 mark]
(a)Cell P
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Ovum
The ovum is a large round cell that carries female genetic material.
[1 mark]
(b)Cell Q
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Red blood cells
Red blood cells are biconcave discs with no nucleus.
[1 mark]
(c)Cell R
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Nerve cell
A nerve cell has long fibres that carry impulses.
16
Diagram 6 shows part of the lower surface of a leaf, seen under a microscope.
[1 mark]
(a)Name cell P.
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Guard cell
[1 mark]
(b)Name the pore R.
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- Stoma1
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[1 mark]
(c)On a very hot day, pore R closes. Explain why this is useful to the plant.
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- It reduces water loss from the plant (so the plant does not wilt)1
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17
A variegated leaf was plucked from a plant that had been in sunlight for a few hours. Diagram 7 shows the leaf before the test. Part P is green and part Q is white. The leaf was then tested for starch with iodine solution.
[1 mark]
(a)State the manipulated variable in this experiment.
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- The presence of chlorophyll1
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[1 mark]
(b)Which part of the leaf turned dark blue?
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P
[2 marks]
(c)Explain your answer in (b).
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Any 2 points
- Part P has chlorophyll (is green), so photosynthesis took place there1
- Starch was made in P, and starch turns iodine dark blue1
- Part Q has no chlorophyll, so no photosynthesis / no starch, and iodine stays brown1
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[1 mark]
(d)Before iodine solution is added, the leaf is placed in ethanol. Why?
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- To remove the chlorophyll so the colour change of iodine can be seen clearly1
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18
Diagram 8 shows an experiment. Two similar plants were kept in the dark for two days and then placed in sealed bell jars A and B under sunlight for four days. Jar A contains a beaker of solution X.
[2 marks]
(a)Name solution X and state its function.
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- Potassium hydroxide solution1
- Absorbs carbon dioxide from the air in the jar1
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[1 mark]
(b)A leaf from each plant is tested with iodine solution. What colour will the leaf from jar A be?
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Brown (iodine does not change colour)
No carbon dioxide in jar A → no photosynthesis → no starch.
[2 marks]
(c)Ali says, "This experiment shows that plants need light for photosynthesis." Do you agree? Justify your answer.
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Any 2 points
- Disagree1
- Both plants received sunlight / light was kept the same (not changed)1
- Only the presence of carbon dioxide was changed, so it shows that plants need carbon dioxide for photosynthesis1
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19
Diagram 9 shows how blood cells are organised in the human body.
[1 mark]
(a)What is the level of organisation of Q (the heart)?
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Organ
[1 mark]
(b)Name system R.
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- Blood circulatory system1
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[1 mark]
(c)State one function of system R.
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- Carries oxygen, nutrients and hormones to all parts of the body1
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[1 mark]
(d)Explain why the skin is an organ and not a tissue.
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- The skin is made of different types of tissues that work together to carry out a specific function1
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20
Your class wants to build a sealed glass jar with water, a small water plant and a snail, so that both can stay alive for many weeks without opening the jar.
[2 marks]
(a)Using your knowledge of photosynthesis and cell respiration, explain how the plant and the snail help each other to survive in the jar.
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- The plant carries out photosynthesis and produces oxygen (and glucose/food) which the snail uses for cell respiration1
- The snail (and plant) carry out cell respiration and produce carbon dioxide (and water) which the plant uses for photosynthesis1
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[1 mark]
(b)Suggest where the jar should be placed. Give a reason.
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- Near a window / in a bright place, because the plant needs light energy for photosynthesis1
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