National 5 Biology. Unit 1 Homework. Cell Biology

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1 National 5 Biology Unit 1 Homework Cell Biology


3 Sub-topic 1.1 Cell Structure 1. Identify the organelles labelled A - E in the following diagrams of an animal and a plant cell The following diagram shows sections through a cheek epithelial cell, a leaf mesophyll cell and a yeast cell. a) Identify 3 structures present in the yeast cell which are also present in the cheek cell. 3 b) Identify 2 structures present in both the yeast cell and leaf cell which are absent from the cheek cell. 2 c) Identify 1 structure present in the leaf cell which is absent from the other two cells. 1

4 3. State the function of each of the following structures: a) b) c) d) cell membrane ribosome mitochondrion nucleus 4 4. The diagram below shows some human cheek cells as they appear when viewed through a microscope. a) If the diameter of the field of view is 240 micrometres what would the average width of a human cheek cell be? 1 b) If the diameter of the field of view is 450 micrometres what would the average width of a human cheek cell be? 1 6. Euglena is a single celled organism. The diagram below shows some of the structures within the Euglena a) Name the substance which makes up plant cell walls. 1 b) Name another type of cell which has a cell wall. 1 Total = 20 marks

5 Sub-topic 1.2 Transport Across Cell Membranes (This homework requires graph paper for Q7) 1. The following sentences give information about the cell membrane of beetroot cells. Copy the sentences using only one alternative in each of the brackets to make the sentences correct. The cell membrane contains cellulose and phospholipids and has a protein carbohydrate fibrous nature. As a result, the membrane is fully permeable. porous selectively 1 2. Give a definition of the term diffusion a) Which of the following molecules can both diffuse through a cell membrane? A B C D Amino acids and starch Amino acids and water Starch and protein Protein and water 1 b) Give a reason for your answer Name the substance that enters or leaves cells by osmosis Give a definition of the term osmosis What term describes the condition of plant cells after being placed in distilled water? 1

6 7. An investigation was carried out to find the effect of different concentrations of salt solutions on the mass of potato tissue. Five test tubes were set up similar to the one shown below, but each containing a different concentration of salt solution. Each potato cylinder was weighed, placed in the solution and left for an hour. Each cylinder was then reweighed and the percentage change in mass was calculated. The table below shows the results of the investigation. Salt concentration Change in mass (%) (g/100cm 3 )

7 Copy and complete the line graph below on the piece of graph paper provided (the first point has been plotted for you). 2 b) The time that the cylinders were in the solutions was kept constant in this investigation. Name two other variables which must be kept constant. 2 c) Would the results be valid if the cylinders were not dried before weighing? Explain your answer Explain what is meant by the term active transport? 1 9. Name three factors which will affect the rate of active transport? 3

8 10. The graphs show the effect of various factors on the rate of uptake of chloride ions by pieces of carrot tissue from their surrounding solution. Which graph supports the hypothesis that chloride ion uptake by carrot tissue involved active transport? A B C D 1 and 2 only 1 and 3 only 2 and 3 only 1, 2 and 3 1 Total = 17 marks

9 Sub-topic 1.3 DNA and the Production of Proteins 1. Decide whether each of the following statements about chromosomes and proteins is true or false and ( ) the appropriate box. If the statement is false write the correct word in the correction box to replace the word underlined in the statement. Statements True False Correction Chromosomes are made from DNA. The DNA molecule contains three different types of bases. Messenger RNA (mrna) is a double stranded molecule State the name given to the coiled arrangement typical of a DNA molecule Using the complementary base pair rule, write down the complementary strand to the DNA molecule shown below. AGA TTC GAC CTA ATC 1 4. If a DNA molecule contains 1000 subunits of which 20% contain the bases adenine, what percentage of the subunits contain guanine? 1 5. Rearrange the statements below to show the correct sequence of events that occurs during protein synthesis. The first stage has been entered for you. 1. The mrna carries the code from the nucleus to the cytoplasm. 2. The DNA molecule opens up at a section the length of a gene. 3. Amino acids are joined together to make proteins. 4. A molecule of messenger RNA (mrna) is made by copying the gene code 5. The mrna code is translated into an amino acid sequence at the ribosome. 2 1

10 6. Complete the missing labels on the diagram below. 3 Total = 10 marks

11 Sub-topic 1.4 Proteins 1. Name two different types of protein and state their function A student set up an investigation to measure the activity of catalase in a variety of tissues at three different temperatures. The bar graph below shows the results. a) Describe the changes in catalase activity in banana when the temperature increased from 20 C to 50 C. 1 b) Calculate the percentage decrease in catalase activity in potato when the temperature increased from 40 C to 50 C. 1 c) State the temperature that gave the highest catalase activity. 1 d) Predict the catalase activity in any tissue at 60 C. Give a reason for your answer. 2

12 3. An investigation was carried out to find the effect of ph on the activity of an enzyme. Substrate at different ph values was added to the enzyme in different test tubes. a) State two variables that must be kept constant for a valid conclusion to be made from this investigation. 2 b) The results of this investigation are shown in the graph below. (i) State the optimum ph for this enzyme. 1 (ii) Calculate how many times more active the enzyme is at ph 9 than at ph 10. 1

13 4. Enzymes are biological catalysts. The diagram below shows part of an enzyme controlled reaction. a) Describe the feature of an enzyme which allows it to combine with only one substrate. 1 b) Describe what happens to an enzyme when it is boiled. 1 c) Name a factor, other than temperature, which affects enzyme activity. 1 d) Copy and complete the following word equation for the enzyme amylase. Substrate Amylase Product 1 e) Enzymes are referred to as being specific. Explain what this term means with reference to the enzyme phosphorylase. 1

14 5. a) Liver is a tissue that contains the enzyme catalase. A piece of liver was added to hydrogen peroxide and foam was produced as shown below. (i) Name the products formed during this reaction. 1 (ii) Describe a control which would be used to show that active catalase is needed for this experiment. 1 (iii) Describe how could the activity of catalase was measured in this experiment. 1 b) The diagram below shows an investigation to compare the activity of catalase in apple and liver. State two variables, not shown in the diagram, that must be kept constant for a valid comparison. 2 c) Explain why enzyme activity decreases at temperatures above the optimum. 1

15 6. a) The diagram below shows three stages X, Y and Z that occur when an enzyme converts its substrate into a product. (i) This enzyme promotes the breakdown of a complex molecule into simpler molecules. Using the letters X, Y and Z put the stages into the correct order to show this degradation reaction. 1 (ii) State which number in the diagram shows the enzyme active site. 1 b) Copy and complete the following sentence by underlining the correct word from the following choice. Enzymes are made of fat / protein/ carbohydrate 1

16 7. The graph shows the effect of temperature on the enzyme invertase. a) Between which two temperatures was there the greatest overall increase in enzyme activity? 0-10 o C, o C, o C or o C 1 b) State the two temperatures when the enzyme activity was 75% of its maximum? 1 Total = 27 marks

17 Sub-topic 1.5 Genetic Engineering 1. Give a definition of the term genetic engineering Genetic engineering can be used to alter bacterial cells in order to produce human insulin. The stages below are in the wrong order. Rewrite the stages to show the correct sequence in which these occur. I. Insulin gene is extracted from a human cell. II. Bacteria divide and produce large quantities of human insulin. III. Plasmid is removed from bacterial cell and cut open. IV. Insulin gene is inserted into bacterial plasmid Describe two medical applications involving genetic engineering Give two examples of plants that have been genetically engineered and their economic benefit to humans Give two possible disadvantages of genetic engineering. 2 Total = 10 marks

18 Sub-topic 1.6 Respiration 1. Living cells need energy for a variety of reasons. Name 2 energy requiring processes that take place in organisms Give the meaning of the term respiration and state where this process occurs in living organisms A group of pupils used a simple calorimeter to measure the energy content of some food types. They made the following table for their results: Food Initial temperature ( C) Final temperature ( C) Temperature difference ( C) Peanut Cornflake a) Copy and complete the table showing the temperature differences. 2 b) Calculate the percentage (%) increase in temperature for the peanut The diagram below shows energy transfer within a cell Which line in the table below identifies correctly compounds X and Y? X Y A Glucose ATP B Glucose ADP C ADP ATP D ATP Glucose 1

19 5. The diagram below shows some steps in respiration in muscle cells. 1 a) Name a substance A. 1 b) What conditions are necessary for this respiratory pathway to occur? 1 c) How many molecules of ATP would be produced per molecule of glucose in this pathway? 1 6. The experiment below was set up to demonstrate aerobic respiration in peas that are germinating (starting to grow). After two days, the level of liquid had risen in tube Y but had not risen in tube X. a) Explain the purpose of A as a control in this experiment. 1 b) Predict the effect on the level of tube Y if a greater mass of peas had been used. 1

20 7. The following list contains some features of aerobic respiration and the fermentation pathway in germinating peas. List V W X Y Z Does not use oxygen Produces carbon dioxide Yields 38 molecules of ATP per glucose molecule Produces ethanol Completes in the mitochondrion Copy and complete the table below by writing the letters from the list in the correct columns. * Each letter may be used once or more that once. Aerobic respiration Fermentation pathway 2 Total = 15 marks