1. What are cells?
The basic units of life.
2. What is stated in the cell theory?
(1) all organisms are made up of one or more cells
(2) the cell is the basic unit of life
(3) all cells come from pre-existing cells
3. What are the two types of electron microscope?
(1) transmission electron microscope
(2) scanning electron microscope
4. What is being used to focus to bring about effects for light microscope and electron microscope respectively?
Light microscope: light
Electron microscope: electron beams
5. Compare the images of light microscope and electron microscope with reference to (1)magnification, (2)colour and (3)3D image.
(1) Electron microscope has a much greater magnification (300,000x at most) than light microscope (1600x at most)
(2) black and white image for electron microscope. Light microscope can give coloured images.
(3) For transmission electron microscope(TEM), only 2D images can be produced showing internal structures of the specimen. For scanning electron microscope(SEM), 3D images can be produced showing external structures of the specimen.
6. Give three advantages of using light microscopes over electron microscope.
(1) Living specimen can be observed while the specimen under observation by the electron microscope must be dead.
(2) Preparation of the specimen for examination under a light microscope is easier / quicker.
(3) Light microscope is cheaper than an electron microscope.
7. Why must the specimen under observation be dead and not moving?
Because at very high magnification (e.g. TEM: x1500000), the slightest movement of the specimen will lead to the image being out-focused.
8. What are the main parts of a compound light microscope (at least 7)? (1 mark)
Main parts: eyepiece, objective, coarse adjustment knob, fine adjustment knob, diaphragm, condenser, light source (mirror or light bulb)
Note: other parts: arm, nosepiece, body tube, stage, base
9. How can the magnification of a light microscope be calculated?
Magnification of the eye piece x magnification of the objective
10. What is the position of the image as observed by the light microscope?
Inverted. For example, if you observe the letter ‘p’ under the microscope, the image becomes ‘d’.
11. What is the procedure of using a light microscope to observe a low power image?
(1) Put the slide with the species mounted on it on the stage.
(2) Look at the stage from the side, adjust the coarse adjustment knob to cause the body tube to lower (or the stage to raise), until the objective almost touches the slide (or is closest to the slide).
(3) Through the objective, turn the coarse adjustment knob to rise the body tube(or lower the stage) until a clear image is obtained.
(4) turn the fine adjustment know to obtain a clear focus on the image.
(5) If necessary, adjust the diaphragm, change the light intensity to obtain a clear image (note: it is wrong to assume that the brighter the better).
12. What is the procedure of using a light microscope to observe a high power image?
(1) First, obtain a clear image at low power.
(2) Move the part for the specimen to be observe to the centre of the field of view.
(3) Rotate the nosepiece to select a high-power objective.
(Watch the stage from the side while rotating to prevent the objective from touching the slide)
(4) Adjust only the fine adjustment knob to obtain a clear image.
(5) If necessary, adjust the diaphragm to obtain an adequate amount of light. (note: at high power, the light will very likely not be enough)
13. What parts of the light microscope affect whether the image is focused or not?
Coarse adjustment knob and fine adjustment knob.
(Note: Other parts have nothing to do with focusing, but affect the clarity of the image.)
14. Apart from focusing parts, what other parts of the microscope affect the clarity of the image?
Eyepiece and objective (affect the magnification, thus affect clarity)
Diaphragm and the condenser( affect the light intensity of the image)
15. What are the features of low power observation when compare with high power? (1 mark)
(1) larger field of view
(2) higher light intensity
(3) easier to focus onto the specimen
16. Within the DSE syllabus, what structures of the animal cells must be studied?
Cell membrane, cytoplasm, nucleus, rough ER, smooth ER, mitochondria, vacuole, ribosome.
17. What are the features of the cell membrane? What are the functions that these features leads to?
(1) have thin membrane, can enclose the cell.
(2) differentially permeable, can control the movement of substances into and out of the cell.
18. What are the properties of the cytoplasm?
It is jelly like, the main component is water and protein.
It holds many organelles (e.g. mitochondria)
19. What are the main functions of the cytoplasm?
(1) It is the site of many chemical reactions inside the cell.
(2) It allows movement and transport of materials inside the cell.
20. What are the properties of the nucleus?
It has a double membrane. There are pores on the nuclear membrane.
It contains DNA.
21. What are the functions of the nucleus?
Controls the metabolic activities (e.g. chemical reactions) of the cells, for example: respiration.
22. What are the characteristics of the mitochondria?
(1) double membrane, with the inner layer highly folded
(2) rod shape
(3) contains enzymes needed for respiration.
23. What is the function of the mitochondria?
The main site where respiration takes place.
24. What are the features of the Endoplasmic reticulum (ER)?
(1) It is a network of interconnected membrane-bounded sacs.
(2) It is continuous with the outer nuclear membrane and extends throughout the cytoplasm.
(3) There are two types of ER, rough ER and smooth ER.
25. What are the functions of the rough ER and the smooth ER?
Rough ER: involved in the synthesis of protein (since there is ribosomes)
Smooth ER: involved in the synthesis of lipid
26. What are the features of the vacuoles in animal cells?
(1) small
(2) bounded by a single membrane
(3) may contains water, food and enzymes
27. What are the structural differences between the plant and animal cell?
Plant cell
(1) contains cell wall (all plants cells have cell walls)
(2) has chloroplasts (only for plants cells that can carry out photosynthesis)
(3) has large vacuole (usually only one)
28. Upon looked on superficially, what is the major differences between the plant cell and the animal cell?
Plant cells usually
(1) are larger than animal cells (usually shows up clearly at 40x lower power)
(2) have regular shapes (due to the presence of the cell wall)
29. What are the features of the cell wall of plant?
(1) Made up of cellulose, therefore it is hard and thick.
(2) Covers the outer part of the cell membrane.
(3) There are a lot of holes among the cellulose molecules, therefore the cell wall is fully permeable.
30. What are the functions of the cell wall to plant?
(1) protect the cell by making it less easy to break or burst.
(2) support the cell by give it a regular shape that does not change easily.
Note: the fact that cell wall can allow water and dissolved materials to pass (i.e. fully permeable) is not a function of the cell wall to plant, since this feature bears no advantage to the plant cells.
31. What are the features of the large vacuole in the plant?
(1) Contains cell sap, which is a liquid containing water and dissolved substances including food(e.g. glucose), pigments and wastes.
(2) When it is filled with water, the cell will becomes turgid.
32. What are the functions of the large vacuole to the plants?
(1) store dissolved wastes
(2) When it is filled with water, the cell will become turgid which can provide support to the plant. This function is especially important to herbaceous plants and not very important in woody plant.
33. What are the features of the chloroplast?
(1) It is bounded by a double membrane.
(2) It contains chloroplyll.
34. What is the function of the chloroplast?
It can carry out photosynthesis to make food.
35. From small to large, what are the levels of body organizations of multicellular organisms?
Cell > tissue > organ > system > organism
36. What is tissue?
Similar cells group together to form a structure (tissue) that performs one or more particular function.
e.g. (1) muscle
(2) liquid tissue : blood
37. What is organ?
Different tissues group together to form a structure (organ) that performs one or more particular function.
e.g. heart
38. What is system?
Several organs work together to perform a particular task.
e.g. digestive system
39. What is the level of body organization should the skin belongs to?
Organ. This is because the skin is composed of different tissues including blood vessels, small muscles and connective tissues.
40. What are the two types of chemical constituents in an organism?
Organic molecules, inorganic molecules
41. What are the two major types of inorganic constituents in the organism?
Water and inorganic ions
42. What is the function of water to an organism?
(1) as a reactant
(2) as a medium for chemical reaction
(3) as a medium for transport
(4) as a cooling agent
(5) provide support
43. List one of the major use of nitrate to living things.
Used for producing proteins
Note: There is nitrogen in nitrate, nitrogen is an essential element to make protein.
44. List the major use of magnesium for plants.
(1) It is the major component of chlorophyll.
(2) It can activates some enzymes.
45. List the major use of calcium.
For the human body:
(1) It is the principal component of bones and teeth
(2) It assists in muscle contraction
(3) It assist in blood clotting
(4) It assist in nerve transmission
For plants:
(1) It strengthen the cell wall
46. What is the major use of iron?
(1) It forms the major component of haemoglobin. Haemoglobin is responsible for carrying oxygen.
(2) It can activates some enzymes.
47. What are the types of organic chemical constituents?
(1) carbohydrates
(2) lipids
(3) proteins
(4) nucleic acids
48. What atoms are contained in carbohydrates?
Carbon (C), Hydrogen (H), Oxygen (O)
49. What are the three commonly seen carbohydrates?
Glucose, starch, cellulose
50. What are the major function of carbohydrates?
(1) directly provide energy
(2) energy reserve (starch)
(3) structural materials (cellulose is the main component of plant cell wall)
51. What elements are contained in lipids?
Carbon, hydrogen, oxygen
52. What is the difference in hydrogen-oxygen ratio between carbohydrates and lipids?
The hydrogen-oxygen ratio of carbohydrates is about 2:1
The hydrogen-oxygen ratio of lipids is much bigger than 2:1
53. What are the common seen lipids?
Triglycerides, phospholipids
54. What are the major functions of lipids?
(1) act as an energy reserve(Triglycerides)
(2) act as a heat insulating layer to reduce heat loss (Triglycerides)
(3) protect internal organs by cushioning them and acting as a shock absorber
(Triglycerides)
(4) As the major component of cell membrane (phospholipids)
55. What are the elements contained in protein?
Carbon, hydrogen, oxygen, nitrogen and sulphur(for some protein)
56. What are the major functions of proteins?
(1) Make up many body tissues (e.g. hair, muscles and skin)
(2) as enzyme, catalyze chemical reactions
(3) as antibodies, defend the body against diseases
57. What are the elements contained in nucleic acids?
Carbon, hydrogen, oxygen, phosphorus, nitrogen
58. What are the two types of nucleic acids?
Deoxyribonucleic acid(DNA), ribonucleic acid (RNA)
59. What are the functions of nucleic acids?
(1) carry genetic information (DNA)
(2) involve in the synthesis of proteins (RNA)
60. What is the major differences between the prokaryotic cells and eukaryotic cells?
Prokaryotic cells do not have nucleus while eukaryotic cells have.
Important note: Genetic materials are still present. There is no nucleus because of the absence of nuclear membrane.
61. Apart from the nucleus, what differences are there between the prokaryotic cells and eukaryotic cells?
Prokaryotic cells:
(1) Mostly have cell wall, but its composition is very different from that of plant cells, protist and fungi.
(2) No ER, but still, there are ribosome.
(3) No double membrane structures including chloroplast and mitochondria
(4) usually much smaller than eukaryotic cells.
62. What kinds of organisms should prokaryotic cells belong to?
Eubacteria and archaebacteria
63. What kinds of organisms should eukaryotic cells belongs to?
Protists, fungi, plants and animals.
64. What is the level of body organization should the skin belongs to?
Organ. This is because the skin is composed of different tissues including blood vessels, muscles and connective tissues.