9700_s06_qp_2 - revisedeck

1

is a drawing made from an electron micrograph of a longitudinal section of a capillary in muscle tissue. A B C D E F × 8000 Complete the table below using the information in to help you. cell A cell B cell C name of cell red blood cell function of cell ingest bacteria permit exchange of gases diameter / µm Name the organelles D, E and F. D E F Examiner’s Use Explain how oxygen and glucose move from the blood inside the capillary to the tissue fluid in the muscle. oxygen glucose Describe how the structure of the wall of a vein differs from that of a capillary.

8. Transport in mammals → 8.1. The circulatory system

Open

2

Use shows part of a summer squash, Cucurbita pepo. is a high power drawing of an area of phloem from a transverse section of the stem of C. pepo. fruit G H Examiner’s Use Name G and H. G H Describe three ways in which the structure of a xylem vessel differs from the structure of cell G. 1. 2. 3. The liquid extracted from the phloem of C. pepo contains sucrose. Explain how sucrose is transported in the phloem along the stem from the leaf to the fruit. Most of the sucrose transported in the phloem enters the fruit. Suggest why summer squash fruits are not sweet.

7. Transport in plants → 7.1. Structure of transport tissues

2. Biological molecules → 2.2. Carbohydrates and lipids

7. Transport in plants → 7.2. Transport mechanisms

Open

3

Use Complete the table by indicating with a tick ( ) or a cross ( ) whether the statements apply to proteins, DNA, messenger RNA and cellulose. You should put a tick or a cross in each box of the table. statement protein DNA messenger RNA cellulose hydrogen bonds stabilise the molecule glucose is the subunit molecule subunits are joined by peptide bonds may be hydrolysed to amino acids contains uracil Examiner’s Use During an immune response, B-lymphocytes become plasma cells and begin to make polypeptides that are assembled into antibodies. is a diagram showing the formation of a polypeptide at a ribosome in a plasma cell. G A A G G G U U C A G tRNA ser gly lys ser val amino acid mRNA C C C U U U A G C movement of ribosome C J State the sequence of bases at J. Examiner’s Use Use the information in to describe the role of transfer RNA molecules in translation. The bacterium that causes cholera, Vibrio cholerae, releases a toxin known as choleragen. During an immune response to cholera some B-lymphocytes produce antibodies that combine with choleragen so inactivating it. Antibodies that inactivate toxins are called antitoxins. Explain how the structure of an antibody, such as the antitoxin for choleragen, makes it specific to one substance. Explain why cholera remains a significant infectious disease in some parts of the world.

6. Nucleic acids and protein synthesis → 6.2. Protein synthesis

11. Immunity → 11.2. Antibodies and vaccination

6. Nucleic acids and protein synthesis → 6.1. Structure of nucleic acids and replication of DNA

Open

4

Use is an electron micrograph of a chloroplast from a mesophyll cell in a leaf. Calculate the magnification of the electron micrograph in . Answer = 0.5 µm Examiner’s Use State two features visible in that identify the organelle shown as a chloroplast. 1. 2. Chloroplasts absorb phosphate ions from the surrounding cytoplasm. Suggest one way in which chloroplasts use phosphate ions. Starch grains in plant cells contain both amylose and amylopectin. Explain how both of these substances are formed from glucose in plant cells. State three functions of the water stored in the vacuoles of plant cells. 1. 2. 3.

1. Cell structure → 1.2. Cells as the basic units of living organisms

13. Photosynthesis → 13.1. Photosynthesis as an energy transfer process

Open

5

Use Some bacteria that are found in soils contain the enzyme urease. Urease catalyses the hydrolysis of urea to form ammonia and carbon dioxide: urea + water carbon dioxide + ammonia Some fertilisers added to soils to help crop growth contain urea. Although some crop plants can absorb ammonium ions, most obtain their source of nitrogen as nitrate ions. Describe how urea from fertilisers becomes available to plants as nitrate ions. The activity of urease can be measured by following the increase in pH as ammonia is produced in the reaction. A student was provided with urease extracted from bacteria and solutions of urea and two chemical inhibitors, thiourea and lead nitrate. The student prepared six reaction mixtures (1 to 6) as shown in Table 5.1 in order to investigate the effect of the two chemical inhibitors on the activity of urease. Table 5.1 reaction mixture urea water thiourea lead nitrate urease boiled urease Key = present in reaction mixture = absent from reaction mixture The student recorded an increase in pH in reaction mixtures 1 and 2. The reaction was faster in 1 than in 2. The pH in the other reaction mixtures did not change. Examiner’s Use The student made some conclusions about the results from the test-tubes. Match the statements to the reaction mixtures, 1 to 6. You may use the numbers once, more than once or not at all. ‘No reaction took place because urease was denatured.’ ‘There was no reaction because there was no substrate for urease.’ ‘The reaction did not occur because there was an inhibitor present.’ Thiourea has a molecular structure that is very similar to that of urea. The student designed an experiment to find out whether thiourea is a competitive inhibitor. The student set up several reaction mixtures like 1 using increasing concentrations of urea. The student determined the initial rate of the reaction for urease at each concentration of urea. The results are shown in . initial rate of reaction concentration of urea The student then repeated the experiment using the same concentrations of urea. However, the student added the same volume and concentration of a thiourea solution to each test-tube in place of the water. Sketch a curve on to show the results that the student would expect if thiourea acts as a competitive inhibitor of urease. Explain why it is important to determine the initial rate of reaction when investigating the effect of a competitive inhibitor on an enzyme.

3. Enzymes → 3.2. Factors that affect enzyme action

3. Enzymes → 3.1. Mode of action of enzymes

Open