Hyndland Secondary School Biology Department

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1 Hyndland Secondary School Biology Department Investigating Cells Homework and Question Booklet 1 Investigating Cells (a) Investigating Living Cells... 2 Investigating Cells (b) Investigating Diffusion... 5 Diffusion... 5 Osmosis... 5 Investigating Cells (d) Investigating Enzymes Enzyme Mechanisms & Investigation Optimum Conditions Problem Solving This booklet is available online from the Hyndland Secondary School website. Any grids for graphs are also available on the site should you wish them for practice. There is also a handy hints booklet which will help you should you get stuck, where appropriate this booklet also includes links to websites giving a more general help with the section. Answers booklet will also be made available when the section has been completed in class. Hyndland Secondary School 1 Biology Department

2 Investigating Cells (a) Investigating Living Cells 1. What are the basic units of life? Marks 2. Why do we need to use stains when looking at plant and animal cells under the microscope? 3. Draw and label a diagram of an animal cell. 4. Draw and label a diagram of a plant cell. 5. State the function of the following parts of a cell: a. Cell Membrane b. Cell Wall c. Cytoplasm d. Nucleus e. Vacuole f. Chloroplast (3) 6. The diagram below represents a plant cell as seen under a microscope. (i) (ii) What are the parts (i) and (ii)? From the diagram, select one piece of evidence that this a plant cell. (2) 7. The diagrams below show some human cheek cells as they appeared under the microscope, at two different magnifications. Describe the effect that increasing the magnification had on: a) the apparent size of the cells. b) the area of the slide seen. Hyndland Secondary School 2 Biology Department

3 2. The diagram below shows some of the structures of a typical plant cell e diagram below shows some of the structures of a typical plant cell Investigating Cells Homework Booklet 20/07/ he The diagram diagram below below shows some of the structures of a typical plant cell. One important structure is missing from the diagram. Copy the diagram into your jotter and add and label the missing structure. 9. The diagram below shows some human cheek cells as they appear when viewed through a microscope. The diameter of the field of view of the microscope is 120 micrometres. a) Calculate the average width of a human cheek cell. 10. The diagram below shows a single-celled organism that lives in ponds.. Provide the information to complete the table. Letter Structure Function A (i) Controls the work of the cell B Cell Membrane (ii) 11. a) Name two features only found in plant cells. b) Describe how cells can be treated so that the cell contents become more visible. c) Cells increase in number by cell division. Name the part of the cell which controls cell division. (2) Hyndland Secondary School 3 Biology Department

4 12. Use the information in the table below to answer the following questions about simple aquatic organisms. Each organism consists of a single cell. Appearance (not drawn to scale) Average Cell length (mm) 1 Features Move by making the cytoplasm flow in any direction. Feed by flowing around smaller organisms. Move by a whipping action of the long flagellum. 0.1 Make food by photosynthesis Move by rhythmical beating of rows of cilia. 0.2 Feed by taking food particles into the gullet and then into the cytoplasm a) Which organism has the smallest cells? b) Which organism does not contain food vacuoles? c) Which organism moves using cilia? d) Euglena carries out photosynthesis. Describe one way in which Euglena differs from typical green plant cells Hyndland Secondary School 4 Biology Department

5 Investigating Cells (b) Investigating Diffusion Diffusion 15. State what is meant by diffusion. 16. Name 3 substances that can move by diffusion. 17. Which part of the cell controls the entry and exit of substances by diffusion. 18. Why is diffusion important to living organisms? 19. The list below names three substances which diffuse into or out of an animal cell. Oxygen Carbon Dioxide Dissolved Food State which of these would diffuse in and which would diffuse out of the animal cell. Osmosis What is the difference between osmosis and diffusion? State what is meant by osmosis. Describe what happens to a plant cell placed in distilled water. Describe what happens to a plant cell placed in a strong sugar solution. Describe what happens to an animal cell placed in distilled water. Describe what happens to an animal cell placed in a strong sugar solution. Hyndland Secondary School 5 Biology Department

6 26. Diagram 1 below shows an onion cell in 10% sugar solution. Diagram 2 below shows the same cell. What treatment could have caused the change shown? 27. The diagram below shows a model of a cell using Visking tubing. Copy and complete the sentence below, choosing the correct word to make the statement correct. There is an overall movement of sugar INTO/ OUT OF the bag by DIFFUSION/ OSMOSIS. 28. The concentration of some substances inside and outside three cells is shown in the diagrams below. Use the numbers to identify the cells in which the following would occur. a) Diffusion of the substance into the cell b) Osmosis Hyndland Secondary School 6 Biology Department

7 29. Red blood cells and onion epidermal cells were placed in pure water and left for one hour. What happens to each of the types cells after one hour in pure water? 30. A single celled organism is found in the water of an estuary where the salt concentration of the water is constantly changing. The changes in salt concentration are observed to cause volume changes in the organism. The volume changes are due to the movement of water in and out of the organisms by osmosis. What change to the salt concentration of the water causes a decrease in the volume of the organism? 31. Tissue from an onion root was placed in water. The diagram below represents a cell from the tissue. The tissue was then transferred into a very concentrated salt solution for one hour. a) Copy and complete the diagram below to show the appearance of the onion cell contents after this time. b) Choose the correct option in the following sentence to make it correct: In concentrated salt solution, water passes INTO/OUT OF an onion cell from a region of HIGH/LOW water concentration, to a region of HIGH/LOW water concentration with the cell membrane acting as a SELECTIVELY/FULLY permeable membrane. Hyndland Secondary School 7 Biology Department

8 32. Five cylinders of potato tissue were weighed and each was placed into a salt solution of a different concentration. The cylinders were reweighed after one hour and the results are shown in the following table. Salt Solution A B C D E Intial Mass of potato cylinder (g) Final mass of potato cylinder (g) a) The potato cylinders were blotted dry before each weighing. Suggest a reason for this. b) Which salt solution had the highest water concentration? c) Calculate the percentage decrease in the mass of the potato cylinder in salt solution D. Hyndland Secondary School 8 Biology Department

9 33. A group of pupils was asked to investigate the effect of osmosis on the diameter of discs of potato tissue. The procedure is outlined below: 1. A large diameter cork borer was used to cut a cylinder of tissue from a peeled potato. 2. Five discs, each 2 mm thick were cut from the cylinder 3. Four discs were transferred to separate petri dishes. 4. The diameter of each disc was measured from graph paper placed underneath the petri dish cm 3 of glucose solution of different concentration was poured into each of the three dishes. 20cm 3 of water was placed into a fourth petri dish. 6. The apparatus was left for 30 minutes and the diameter of each disc was measured. Diagram 1 below shows the apparatus and Diagram 2 shows how the diameter of a disc was measured. The results are shown in the table below. Solution Concentration of glucose solution Diameter of Disc (mm) At start After 30 minutes A 0.0% B 0.5% C 1.0% D 1.5% a) Identify the variable which was altered and two variables which were kept constant in this investigation. b) Water can enter or leave the disc by osmosis. Describe the overall movement of water for the discs immersed in the 1.0% glucose solution. c) Identify a solution which has a water concentration higher than that present in potato tissue. d) The fifth disc was placed in a solution of unknown glucose concentration. Its final diameter was 13.0mm. Which range of glucose concentrations is it most likely to have been in? 0% -0.5% 0.5% - 1.0% 1.0% 0 1.5% 1.5% - 2.0% (2) Hyndland Secondary School 9 Biology Department

10 Investigating Cells (d) Investigating Enzymes Enzyme Mechanisms & Investigation What is a catalyst? What is an enzyme? Why are enzymes important to living organisms? Enzymes are said to be substrate specific, what does this mean? What are enzymes made of? 39. An investigation was carried out to find the effect of a chemical on the activity of the enzyme amylase. Amylase acts on starch to produce the sugar maltose. The test tube were placed in a water bath at 37C. After 20 minutes, iodine solution was added to each tube to test for the presence of starch. The results are shown in the table below. Tube Starch concentration A High B Zero C Low a) Suggest one factor about the starch suspension, not shown in the diagram, which should be the same in each of the tubes at the start. b) Tube A is a control, explain the purpose of a control. c) Describe the effect of the chemical on the activity of the enzyme amylase Hyndland Secondary School 10 Biology Department

11 40. An investigation was carried out to compare the catalase content in a G variety of tissues. Catalase is an enzyme found in living cells; it breaks down hydrogen peroxide into water and oxygen. A cube of potato tissue was added to some hydrogen peroxide. The volume of oxygen released during the next three minutes was collected and measured as shown below The experimental method was repeated using cubes of liver, apple and carrot. The results are shown below. Tissue Volume of oxygen collected in 3 minutes (cm 3 ) Potato 5.0 Liver 39.5 Apple 0.5 Carrot 3.0 a) Which tissue contains the least catalase? b) Which tissue contains the most catalase? c) Name two factors (not connected with the apparatus) which must be kept constant to ensure that a valid comparison of the tissues can be made. d) Briefly describe a suitable control for the experiment. e) Explain why several samples of each tissues should have been used and an average volume of oxygen calculated. f) Another plant tissue containing catalyse was used in the experiment. It contains more catalase than carrot, but less catalyse than potato. Predict the volume of oxygen which would be collected in 3 minutes. (2) Hyndland Secondary School 11 Biology Department

12 Optimum Conditions 41. Describe the effect of increasing the temperature on enzyme activity. 42. What is meant by the term optimum in relation to enzymes? 43. What are enzymes made of? 44. The graph below shows the effect of ph on the activity of the enzyme, pectinase. a) b) c) Between which two values is pectinase most active? What term is used to describe the ph at which an enzyme is most active? Pectinase only breaks down pectin, it has no effect on cellulose. What term is use to describe this property of enzymes? Name an enzyme which causes the chemical breakdown of a substance Name an enzyme which causes the synthesis (chemical build up) of a substance Hyndland Secondary School 12 Biology Department

13 47. The enzyme lipase catalyses the breakdown of fats into fatty acids & glycerol. It can be obtained as a dry powder and made into a solution before use. The effect of storage at different temperatures on the activity of the lipase solution was investigated. The results are shown in the graph below. a) b) c) d) e) f) How long did it take for the lipase activity to decrease to 50% when stored at 20 C? Which of the following lipase solutions would be most active? A Stored at 4 C for 30 hours B Stored at 4 C for 140 hours C Stored at 20 C for 10 hours D Stored at 20 C for 50 hours In this investigation, the substrate for lipase was the fat in milk. Explain why a starch suspension could not be used as the substrate for lipase. The lipase activity was estimated by measuring the change in ph while it was breaking down fats. Explain why the ph changed during this reaction. Hyndland Secondary School 13 Biology Department

14 48. To investigate the effect of temperature on the activity of the enzyme pepsin, five test tubes were set up as shown below. Each tube was placed in a water bath at a different temperature. After 12 hours, the following results were obtained. a) b) c) d) Plot a line graph of the data using the graph paper below lot a line graph of the data using the graph paper below Plot a line graph, using the graph paper you have been given. At which temperature did the greatest digestion of egg white take place? Describe the effect of increasing the temperature on the activity of the pepsin over the temperature range 5 C 25 C and also between 35 C and 60 C. If the experiment had been repeated at ph 7, which of the following would be the most likely result for the legth of the egg white in test tube B? 19mm 17mm 15mm 13mm (3) Hyndland Secondary School 14 Biology Department

15 Problem Solving 48. Milk contains fat, sugar and protein. One product of the breakdown of fat by the enzyme lipase is fatty acid. a) Name the other product of this reaction. An investigation was carried out on the effect of temperature of the enzyme lipase. Three tubes were set up, each containing 20cm3 of milk and 1cm3 lipase. The tubes were then placed in water baths at different temperatures. The ph of the contents was measured when each tube was placed in the water and at 10 minutes intervals thereafter. The results are shown in the table below. ph Tube Temperature Start 10min 20min 30min 40min ( C) A B C b) c) d) e) Explain why the ph decreased in each tube It was concluded that the optimum temperature for this enzyme was 40C. What evidence from the table of results supports this conclusion? Enzymes are denatured at high temperatures, but the results show some enzyme activity in tube C. Suggest a reason for the enzyme activity in tube C. Suggest a change to the procedure which would prevent this. Hyndland Secondary School 15 Biology Department