Cells N5 Homework book

1 Cells N5 Homework book

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5 Homework2 Cell Ultrastructure and Membrane 1. Name and give the function of the numbered organelles in the cell below: A E B D C 2. Name 3 structures you might find in a plant cell but not in an animal cell. 3. Identify one similarity and one difference between a plant cell and a fungal cell. 4. A newly discovered species was being classified. The organism is unicellular, has no organelles and several plasmids. Should it be classified as an animal, a plant, a bacterium or a fungus? Why? 5. When examining the cells of a carrot under the microscope, which plant organelle would you not expect to see? Why? 6. Use your own words to describe the structure of the cell membrane. In your description make sure you include the terms: bilayer, protein, phospholipid and fluid mosaic.

6 Homework 3 1. The diagram below shows a cross-section of a plasma membrane. a. Describe the function of the plasma membrane. b. A plasma membrane is sometimes described as consisting of a phospholipid bilayer. What does this mean? c. Draw labels onto the diagram to show the position of a: phospholipid molecule; protein molecule. d. Suggest one possible job of a protein embedded in the membrane. e. Plasma membranes are said to be selectively permeable. Explain what this means, giving examples.

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12 Homework 6 Protein Task to demonstrate secure learning. Use all you know to make a poster to show how DNA codes for proteins by following these instructions: 1. Choose one of these DNA sequences (or make up your own) TACTCGAATCGATTTATC TACAGCCGTGTCCCAATT TACTTAGGCCATGGGACT 2. Arrange the DNA sequence into triplets 3. Use the protein decoder (see below or in class) to identify the amino acids coded for by your triplets 4. Arrange the amino acids in the correct order to form a protein Your poster must be colourful, informative and in easy to follow steps to show you understand how DNA codes for a protein.

13 Homework 7 1. The diagram below shows a yeast cell. a. Name the structure shown in the diagram that contains genetic information. b. In a unicellular organism like yeast, a type of cell division called mitosis occurs. What is the importance of mitosis to yeast cells? c. During mitosis the genetic information inside the cell is copied. This is called DNA replication. Why does this happen? d. Describe what could happen if a mistake is made during DNA replication and the DNA is incorretly copied? 2. Mitosis also occurs in multicellular organisms. The graph below shows the results of an experiment to measure the increase in shoot length of germinating pea plants over a forty day period.

14 a. Which five day period shows the greatest average increase in shoot length? b. What is the total increase in shoot length between day 15 and day 30? c. In this investigation a total of one hundred plants were used. Explain why using so many plants makes the results more reliable. d. Suggest another way that the student who did this investigation could have measured the overall growth of the shoots.

15 Homework 8 Mitosis Homework Use the information found at web address shown below to complete the tasks about mitosis. http://www.abpischools.org.uk/page/modules/ce lldiv_cancer/cancer4.cfm 1. Identify three important function of mitosis. 2. Why are the cells in an organism said to be genetically identical? 3. Explain what is meant by a cancer cell. 4. What is a tumour? 5. Describe how medicines used to treat tumours work.

16 Homework 9 DNA Code Cracking 1. DNA is a code for making proteins. a. How does the sequence of bases in a DNA molecule control which protein is made? b. Explain how a mistake during DNA replication could result in the wrong protein being made. 2. The DNA code is copied then translated before a new protein is made. During the copying process the base Thymine is relaced with a base called Uracil, represented by the letter U. This means that the codes for amino acids all contain the letter U instead of letter T. Use the genetic code to identify the amino acids being coded for in each of the sequences below. See if you can complete this example first: a. AAAAGUUACUUGGGACCG Now crack the next two codes! b. GCCACCAACAGCGUUCAC c. CUGGGGACUUCCCAGGUG d. Identify the amino acid that would be inserted into the sequence above if the first base was changed from a C to an A. (use the table on the last page to help you) 3. The diagram below shows how long chains of amino acids form to make proteins. This model is actually insulin, which your body needs to control its blood sugar levels. As you can see it is two separate chains of amino acids joined together by chemical bonds.

17 Name of amino acid Abrreviation Name of amino acid Abrreviation Phenyalanine Phe Tyrosine Tyr Leucine Leu Histidine His Isoleucine Ile Glutamine Gln Methionine Met Asparagine Asn Valine Val Lysine Lys Serine Ser Aspartine Asp Proline Pro Glutamic acid Glu Threonine Thr Cysteine Cys Alanine Ala Tryptophan Trp Arginine Arg Glycine Gly a. In what part of the cell are amino acids joined together? b. What is the name of the molecule that carries the copy of the DNA code for making proteins? c. What name is given to a long chain of amino acids? d. What kind of chemical bonds join amino acids together? The genetic code

18 Enzymes 1 Homework 10 1. As you (should) know by now enzymes are made of protein and speed up chemical reactions. Explain exactly why it is important for enzymes to be the correct shape. 2. Draw a labelled diagram to demonstrate the lock and key hypothesis. 3. Enzymes are described as being substrate specific. Explain what this means. 4. The table below shows five enzymes that you may have heard of, along with their substrates and products. They are all mixed up! Re-draw the table and match the substrate and products up with the correct enzyme. Substrate Enzyme Product Fat Pepsin Maltose Glucose-1-phosphate Lipase Water and oxygen Starch Catalase Amino acids Hydrogen peroxide Phosphorylase Fatty acids and glycerol Protein Amylase Starch 5. Four out the five enzyme controlled reactions shown above are degradation reactions. Only one is a synthesis reaction. a. Define the terms degradation and synthesis in relation to enzymes. b. Identify the synthesis reaction from the table above. c. Describe an example of a synthesis reaction that happens inside your body every day, naming the substrate, the enzyme and the products.

19 Homework 11 Enzymes Homework 1. As you (should) know by now enzymes are made of protein and speed up chemical reactions. Explain exactly why shape is important for enzymes. 2. Define the term optimum conditions in relation to enzyme activity. 3. Name three factors that could affect the activity of an enzyme. 4. The graph below shows the results of an investigation carried out by some students into the action of the enzyme catalase on hydrogen peroxide. The students wanted to know how changing the temperature affected the activity of the enzyme. a. What is the optimum temperature for the activity of catalase? b. Describe what happens to the activity of the enzyme as the temperature of the experiment is increased from 10 o C to 55 o C. c. Predict the height of the foam that would be produced if this experiment was carried out at 70 o C. Explain your answer. 5) This question refers to the graph below. Enzymes of the digestive system work best at different ph conditions. In the mouth, ph tends to be neutral so amylase works best at around ph 7. The stomach is very acidic, with conditions of around ph 2. The enzyme trypsin, found in the small intestine, works best at about ph 9. a. Use the letters on the graph to identify amylase, pepsin and trypsin. c. Which enzymes would both still work at ph 8? d. Enzyme A does not work at ph 6. Why?

20 6. The diagram below shows an investigation into the enzyme amylase. Amylase is an enzyme found in saliva that breaks down starch in food into a sugar called maltose. a. Suggest one improvement to the way this experiment has been set up that would make the results more valid. b. What is the purpose of test tube B? c. After one hour the water outside of the visking tubing in both test tubes was tested with for the presence of starch and maltose. What results would you expect? Explain your answer for both Tube A and Tube B. d. Suggest two ways that the rate of the reaction in Tube A could be increased. e. The experiment was repeated using the enzyme catalase in test tube A instead of amylase. After one hour the water outside the visking tubing water tested for the presence of starch and maltose. What result would you expect in Tube A? Explain your answer.

21 Homework 12 Genetic Engineering 1. The diagram below shows some of the stages of genetic engineering which are used to produce new medicines such as human insulin. a. Complete the table to identify the labelled parts of the diagram. Name of Structure Bacterial cell Plasmid Insulin gene Label b. Describe the next stage of the process needed to create insulin as a medicine, after the gene has been successfully inserted into the plasmid and the plasmid reinserted into the bacterium. c. Name another useful product produced by genetic engineering. d. State two advantages and two disadvantages of genetic engineering. 2. Part of the process of genetic engineering is shown in the picture opposite. a. Describe what is happening at this stage. b. Name an enzyme needed at this stage.

22 Proteins Homework 13 1. Describe the basic structure of a protein molecule. You may draw it but you need to write a description as well. 2. Name the chemical elements needed to make proteins. 3. Where are proteins made? See if you can find a diagram of one being synthesised and make a labelled drawing of it. 4. Why do different proteins have different properties? 5. Find out, using the internet, the library or by asking someone (or all three!) about the proteins keratin and haemoglobin. You should compare them, e.g. what they do, and where they are found and any other interesting information (a table might be a good way to do this). You should also explain why they have different properties.

23 Homework 14 When peas germinate they carry out aerobic respiration. An investigation to find out if heat is produced by germinating peas was carried out using the apparatus below. The change in temperature inside the flask was measured over a period of 72hrs. The results are shown below. Time (hrs) Temperature ( 0 C) 0 18 12 26 1. Calculate the total rise in temperature. (1) 2. Calculate the average rise in temperature per hour. (1) 24 40 36 48 48 50 60 52 72 54 3. Using your graph paper draw a line graph of the results from the table. (3)

24 4. What conclusion can be drawn from these results? (1) 5. Why would it be necessary to set up a control for this experiment and what would make a suitable control? (In other words, how can you tell that the peas are responsible for the heat that is produced?) (1) 6. State one factor which must be kept the same in order for the control experiment to be a valid comparison. (1) 7. Respiration can be described as a two stage process. a. What molecule is glucose broken down into during the first stage?(1) b. How many ATP are produced in the first stage? (1) c. How many ATP are produced in the second stage? (1) d. Name the waste products of respiration. (1) 8. Name four uses of ATP by cells. (2) 9. How could the rate of respiration in animals be measured? (1)