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1 Section (a) Cells and organelles th is is re vi sio n. com 1. Make a diagram to show the structure of a liver cell as seen using an electron microscope. On your diagram, label the following: nucleus nuclear envelope rough endoplasmic reticulum smooth endoplasmic reticulum Golgi apparatus mitochondrion ribosomes centrioles lysosomes Make sure that you know the functions of each of these organelles a liver cell as seen using an electron microscope 2. Sketch a diagram to show the structure of the cell surface membrane. Label the phospholipids, proteins and glycoproteins. the fluid-mosaic model of membrane structure

2 3. Make a diagram to show the structure of a leaf palisade cell as seen using an electron microscope. On your diagram, label the following: nucleus nuclear envelope rough endoplasmic reticulum smooth endoplasmic reticulum Golgi apparatus mitochondrion ribosomes chloroplast vacuole cell wall a leaf palisade cell as seen using an electron microscope 4. Liver cells and palisade cells are examples of eukaryotic cells. Complete the table below to show FIVE differences between eukaryotic cells and prokaryotic cells. Feature Eukaryotic cell Prokaryotic cell

3 5. The cell surface membrane is described as being partially (or selectively) permeable. Write a brief explanation of each of the following methods of membrane transport. Diffusion... Osmosis... Active transport... Endocytosis and exocytosis... DEFINITION A tissue is defined as a group of cells of common origin, with a similar structure and function (e.g. palisade mesophyll tissue). Different tissues then group to form an organ (e.g. a leaf).

4 6. Explain briefly why viruses are considered are considered to be exceptions to the cell theory Note: in this Module you are not expected to know the detailed structure of a virus - that comes into Module B/HB4A Section (b) Molecules In this section, you are expected to know the chemical nature, general formulae and biological significance of DEFINITION water carbohydrates A water molecule is described as being polar, because it has slight positive and lipids proteins negative charges on the molecule. Water is an important solvent, because other nucleic acids. polar substances, such as glucose, will dissolve in water. Non-polar substances, such as oils, will not mix with water. 7. Write the general formula for a hexose (e.g. glucose) and a pentose (e.g. ribose). hexose... pentose Name the type of bond formed when two monosaccharides join to form a disaccharide.... What type of reaction is involved in the formation of this bond?...

5 9. Complete the table below, by writing in the names of the two monosaccharides which join together to form the disaccharides. Disaccharides Constituent monosaccharides sucrose maltose lactose 10. Polysaccharides consist of large numbers of monosaccharides joined together to form long chains. Polysaccharides are insoluble. For each of the polysaccharides below, name their constituent monosaccharides and write a brief account of their biological significance. Starch... Glycogen... Cellulose...

6 11. Sketch diagrams to show the general structures of: (a) (b) a triglyceride a phospholipid. On your diagram of the phospholipid, label the polar (hydrophilic) head and the non-polar (hydrophobic) tail.. a triglyceride a phospholipid Refer back to your drawing of the cell surface membrane to remind yourself how phospholipids are arranged in the bilayer. 12. The diagram below shows the general structure of an amino acid. Copy the diagram, to draw another amino acid alongside, then show how a peptide bond is formed. H R N C C O H H OH

7 13. A protein consists of one or more polypeptide chains, each polypeptide chain in turn consists of chains of amino acids joined together as shown in Qu.12. Proteins are often described in terms of their primary, secondary and tertiary structural features. Briefly explain what is meant by each of these terms. Primary structure... Secondary structure... Tertiary structure Explain why the tertiary structure is import in terms of the functioning of enzymes. 15. The diagram below shows a simplified version of part of a DNA double helix. Draw a ring around one nucleotide, then name the parts labelled A, B, C and D. C A... B... B A C... D... D

8 16. Describe one simple biochemical test for each of the following: starch... reducing sugars... non-reducing sugars... protein... Section (c) Enzymes DEFINITION An enzyme is a biological catalyst, which greatly increases the rate of a chemical reaction, by reducing the activation energy. Almost all enzymes are proteins. The substance with which an enzyme reacts is referred to as the substrate, which attaches to part of the enzyme known as the active site. Enzymes are specific, because of the complementary shape of the active site and the substrate (the lock and key hypothesis).

9 17. Complete the following graphs to show the effects of changes in temperature, ph, enzyme concentration and substrate concentration on the rate of an enzyme-catalysed reaction. Don t forget to label the axes! effect of temperature on enzyme activity effect of ph on enzyme activity effect of substrate concentration on enzyme activity effect of enzyme concentration on activity 18. Now explain why each of these factors affects enzyme activity. In your answers, you should refer to the enzyme s active site. Temperature... ph...

10 Substrate concentration... Enzyme concentration...

11 DEFINITION An inhibitor is a substance which reduces the rate of an enzyme-catalysed reaction. Some inhibitors have a shape which is similar to the substrate and can fit into the active site, so blocking access for the substrate. The inhibitor may then leave the active site, so that the substrate is able to attach.. This is referred to as competitive inhibition. Other inhibitors attach tightly to the enzyme, either at the active site or elsewhere. This can alter the shape of the active site so that the enzyme is permanently inactivated. This is known as irreversible inhibition. 19. Find out one example of a competitive inhibitor and one example of an irreversible inhibitor. Competitive inhibitor... Irreversible inhibitor Describe the type of reaction catalysed by each of the following: oxidoreductases... hydrolases... ligases...

12 21. Explain what is meant by the term enzyme immobilisation What are the advantages of using immobilised enzymes in industrial processes? Complete the table below, giving one commercial use of each of the enzymes. Enzymes Commercial uses Amylases Pectinases Proteases Lactases Section (d) Metabolic pathways DEFINITION A metabolic pathway is a sequence of reactions occurring in living organisms, each step is controlled by a specific enzyme. We could represent a metabolic pathway by the following sequence: A + B C D E F + G In this case, A and B are referred to as the reactants, C, D and E are the intermediates, and F and G are the products.

13 23. Respiration is an example of a metabolic pathway. Aerobic respiration, that is, respiration in the presence of oxygen, consists of three main stages: glycolysis the Krebs cycle oxidative phosphorylation. Write a brief outline of each of these stages, indicating where, in a eukaryotic cell, they occur. glycolysis IMPORTANT NOTE Check with your copy of the syllabus to see which individual reactions you are expected to know. the Krebs cycle... oxidative phosphorylation...

14 24. In the box below, make a labelled, outline drawing of a mitochondrion. On your drawing, show clearly where the Krebs cycle and oxidative phosphorylation occur. a typical mitochondrion A typical mitochondrion is about 7 µm long. Measure the length of your drawing of a mitochondrion, then work out the magnification. Show your working. Answer Name the products of anaerobic respiration in each of the following: muscle... a yeast cell Give THREE uses of ATP in living organisms

15 27. Compare the yields of ATP in aerobic respiration and anaerobic respiration NOTE Figures for the total yield of ATP in aerobic respiration differ between about 31 and 38 according to the exact conditions. Section (e) Chromosomes and the genetic code Chromosomes in eukaryotic cells consist of DNA proteins, including histones small amounts of RNA. 28. Complete the diagram below to show how a length of DNA wraps around the histones to form a nucleosome. a nucleosome fibre

16 29. Further coiling and folding of the nucleosome eventually forms a chromosome. Make a diagram to show a chromosome, as it would appear at metaphase. Label the chromatids and the centromere. a metaphase chromosome 30. Draw an label a diagram to show the process of semi-conservative replication of DNA. semi-conservative replication

17 31. Describe the functions of the following enzymes in DNA replication. DNA polymerase... DNA ligase Describe how genetic information is contained in the base sequence of DNA 33. Write an account of protein synthesis. Use the terms transcription, translation, mrna, trna, ribosome, codon and anticodon in your answer.

18 34. Distinguish between haploidy and diploidy. 35. Outline the cell cycle. When does DNA replication occur? 36. Draw a series of labelled diagrams to show the stages of mitosis in a plant cell where 2n = 4. prophase metaphase anaphase telophase

19 37. Mitosis is important in growth, replacement and asexual reproduction, the daughter cells are genetically identical to the parent cell. Meiosis involves division of a diploid cell (2n) to form four haploid (n) cells, giving rise to genetic variation. Complete the table below, giving SIX differences between mitosis and meiosis. MITOSIS MEIOSIS Section (f) Patterns of inheritance 38. Explain what is meant by each of the following terms, giving examples where appropriate. Continuous variation... Discontinuous variation...

20 Gene... Allele... Genotype... Phenotype... Homozygote... Heterozygote... Dominance... Codominance...

21 39. Complete the following genetic diagram to show the F 1 and F 2 produced in the following crosses. Assume that random interbreeding occurs amongst the F 1 to produce the F 2. AA aa F 1 F 2 HINT In a genetic diagram, always indicate the gametes clearly, e.g. by labelling them gametes, or by enclosing each in a circle A or a AABB aabb F 1 F 2 HINT In a genetics question, if you are asked to state the ratio, always write it in the form of 3 : 1 or 1 : 1, rather than, for example, 50 : 50

22 40. Inheritance of ABO blood groups is an example of a multiple allele system. Using the symbols I A, I B and I o to indicate the alleles, complete the boxes by giving all possible genotypes of the following blood groups. Blood groups Genotypes A B AB O 41. Explain what is meant by each of the following terms, giving examples where appropriate. Autosomal linkage... Recombinants... Sex linkage...

23 Section (g) th is is re vi sio n. com Sources of new inherited variation 42. Revise the process of meiosis and consider why meiosis and random fertilisation lead to genetic variation in populations. Inherited changes in DNA, known as mutations, also increase variations in populations. The rate at which mutation occurs can be greatly increased by exposure to mutagens, including certain chemicals, such as..., or ionising radiation, for example, gamma rays. There are two main types of mutation: chromosome mutations, such as translocation, polysomy and polyploidy, which involve changes in the structure or number of chromosomes present in cells and point mutations, which involve changes in a single base in the DNA molecule. Point mutations include base deletions, insertions and substitutions. 43. Identify the types of point mutation which have occurred in the following examples. Normal base sequence A A T C G G C C T T A G C Mutant 1 A A T C G C C T T A G C... Mutant 2 A A T C G G C C A T A G C... Mutant 3 A A T C G G C C C T T A G C Explain why point mutations may affect the protein produced. 45. Explain the use of each of the following in gene technology.

24 Reverse transcriptase... Endonuclease... Plasmid... Ligase Name TWO proteins which are produced using genetically modified organisms Describe TWO other applications of gene technology.

25 HINT The polymerase chain reaction is described in Tools, Techniques and Assessment in Biology - A course Guide for Students and Teachers 49. Outline the use of genetic fingerprinting as a diagnostic tool.

26 50. Recently, there has been considerable controversy about the uses and applications of genetically modified organisms (GMOs). Discuss the potential benefits and possible risks associated with genetically modified crop plants.

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