Biology Exam - Organisms exchange substances with their environment

  Biology Exam with Answers   Organisms Exchange Substances With Their Environment 

Question 2 - Miner's Lung

Miner's lung is a disease caused by breathing in dust in coal mines. The dust causes the alveolar epithelium to become thicker. People with miner's lung have a lower concentration of oxygen in their blood than healthy people.

Question 2 - Miner's Lung

(a) (i) Describe the path by which oxygen goes from an alveolus to the blood. (2 marks)

Question 2 - Miner's Lung

(a) (i) Oxygen diffuses across the epithelial cells lining the alveoli and then diffuses across the endothelium lining of the capillaries.

Question 2 - Miner's Lung

(a) (ii) Explain why people with miner's lung have a lower concentration of oxygen in their blood. (1 mark)

Question 2 - Miner's Lung

(a) (ii)  The walls of the alveoli are thicker increasing the diffusion pathway.

Question 2 - Miner's Lung

(b) In healthy lungs, a gradient is maintained between the concentration of oxygen in the alveoli and the concentration of oxygen in the lung capillaries. (i) Describe how ventilation helps to maintain this difference in oxygen concentration. (2 marks)

Question 2 - Miner's Lung

(b) (i)  Ventilation ensures that fresh air with a high concentration of oxygen is brought into the lungs to replace the air already in the lungs which has a much lower concentration of oxygen, maintaining the concentration gradient.

(b) (ii) Give one other way that helps to maintain the difference in oxygen concentration. (1 mark)

Question 2 - Miner's Lung

Question 2 - Miner's Lung

(b) (ii) The circulation of the blood.

Miner's Lung (binary/octet-stream)

Question 2 - Miner's Lung

(c) Scientists investigated the number of cases of miner's lung reported in Britain between 1992and 2006. Coal mining in Britain had been dramatically reduced by 1990. Some scientists concluded that the rise in reported cases of miner's lung after 1992 shows that the disease takes a long time to develop. Evaluate this conclusion. (2 marks)

Question 2 - Miner's Lung

(c)  Even after coal mining in Britain had been dramatically reduced in 1990, the cases of miner's lung continued to rapidly increase especially between 2001 and 2004. This supports the conclusion. However, there may be other causes involved such as new diagnostic methods as correlation doesn't always equal causation.

Phloem Diagram (binary/octet-stream)

Question 3 - Mass Transport in Plants

The diagram shows some cells from phloem tissue. (a) Using label lines, label the following structures on the diagram. (i) Sieve plate (ii) Companion cell (2 marks)

Question 3 - Mass Transport in Plants

(i) A straight line coming from the sieve plate in the middle of the phloem tube. (ii) A straight line coming from the cell adjacent to the phloem tube.

Question 3 - Mass Transport in Plants

(b) (i) Name the main carbohydrate transported by phloem tissue. (1 mark)

Question 3 - Mass Transport in Plants

(b) (i) Sucrose

Question 3 - Mass Transport in Plants

(b) (ii) Carbohydrate enters the sieve cells in the leaves. This leads to the mass flow of substances in the phloem. Explain how. (3 marks)

Question 3 - Mass Transport in Plants

(b) (ii) When sucrose is actively transported into the sieve tube elements it decreases the water potential. So via osmosis water diffuses in from the xylem which has a higher water potential. This creates high hydrostatic pressure.

Question 3 - Mass Transport in Plants

(c) Mineral ions are continuously transported into the leaves by the xylem. Phloem transports some mineral ions from the leave to the other parts of the plant. (i) Only the phloem can transport mineral ions out of the leaves to other parts of the plant. Explain why. (1 mark)

Question 3 - Mass Transport in Plants

(c) (i) The xylem only flows in one direction whereas the phloem flows in two directions.

Question 3 - Mass Transport in Plants

(c) (ii) Calcium ions are not transported by the phloem. Explain why the leaves of the plant are a good source of calcium for grazing animals. (1 mark)

Question 3 - Mass Transport in Plants

(c) (ii) Calcium would accumulate in the leaves as nothing is there to transport it away.

Question 6 - Tissue Fluid

The diagram shows the hydrostatic pressures and the water potentials of the blood at the arterial end of the capillary and of the tissue fluid surrounding the capillary. Blood in Capillary: Water Potential = -3.3kPa and Hydrostatic Pressure = 4.6kPa Tissue Fluid: Water Potential = -1.3kPa and Hydrostatic Pressure = 1.1kPa

Question 6 - Tissue Fluid

(a) Use the information in the diagram to explain how tissue fluid is formed. (4 marks)

Question 6 - Tissue Fluid

(a) A high hydrostatic pressure is created at the arterial end of the capillary due to the contractions of the heart. This is opposed however by the hydrostatic pressure of the tissue fluid outside the capillary. Also by the lower water potential inside capillary which causes water to diffuses into the capillary via osmosis. The overall net filtration pressure is 1.5kPa which is greater than the net osmotic pressure. This causes the tissue fluid to be forced out of the arterial end of the capillary.

Question 6 - Tissue Fluid

(b) In a healthy person, not all of the fluid leaving the arterial end of the capillary is returned to the blood at the venous end of the capillary. Describe how the remainder of this fluid is returned to the blood. (1 mark)

Question 6 - Tissue Fluid

(b) It returns via the lymphatic system.

Question 4 - Haemoglobin

(a) An increase in respiration in the tissues of a mammal affects the oxygen dissociation curve of haemoglobin. Describe and explain how. (2 marks)

Question 4 - Haemoglobin

(a) If there is more respiration, more CO2 is produced. Co2 effects haemoglobin's affinity to oxygen by decreasing it. This therefore shifts the oxygen dissociation curve to the right.

Question 4 - Haemoglobin

(b) There is less oxygen at high altitudes than at sea level. (i) People living at high altitudes have more red blood cells than people living at sea level. Explain the advantage of this to people living at high altitude. (2 marks)

Question 4 - Haemoglobin

(b) (i)  People at high altitudes have more haemoglobin so that they can load more oxygen as there is so little at their altitude.

Oxyhaemoglobin Curve (binary/octet-stream)

(b) (ii) The graph shows oxygen dissociation curves for people living at high altitudes and for people living at sea level. Explain the advantage to people living at a high altitude of having the oxygen dissociation curve shown in the graph. (2 marks)

Question 4 - Haemoglobin

Question 4 - Haemoglobin

(b) (ii) The curve is shifted to the right so it means that haemoglobin has a lower affinity for oxygen. This means that more haemoglobin can be released into cells and tissues.

Question 8 - Mass Transport in Plants

(a) Students measure the rate of transpiration of a plant growing in a pot under different environmental conditions. The results are as followed: A - Still air at 15oC Transpiration rate: 1.2   B - Moving air at 15oC Transpiration rate: 1.7   C - Still air at 25oC Transpiration rate: 2.3

Question 8 - Mass Transport in Plants

(a) (i) During transpiration, water diffuses from cells to the air surrounding a leaf. Suggest an explanation for the difference in transpiration rate between conditions A and B. (2 marks)

Question 8 - Mass Transport in Plants

(a) (i) Moving air increases the rate of transpiration as the air is constantly moving to maintain a concentration gradient. This means that the air by the plant will also have a lower water potential compared to the plant itself, so water is always evaporating from the plant.

Question 8 - Mass Transport in Plants

(a) (ii) Suggest an explanation for the difference in transpiration rate between conditions A and C. (2 marks)

Question 8 - Mass Transport in Plants

(a) (ii) The water molecules would have more kinetic energy meaning they move faster which increases the diffusion from the plant.

Question 8 - Mass Transport in Plants

(b) Scientists investigated the rate of water movement through the xylem of a twig from a tree over 24 hours. The graph shows their results. It also shows the light intensity for the same period of time.

Img 2231 (binary/octet-stream)

Question 8 - Mass Transport in Plants

(b) (i) Describe the relationship between the rate of water movement through the xylem and the light intensity. (1 mark)

Question 8 - Mass Transport in Plants

(b) (i)  There is a positive correlation. As light intensity increases so does the rate of water movement.

Question 8 - Mass Transport in Plants

(b) (ii) Explain the change in the rate of water movement through the xylem between 06:00 and 12:00 hours. (2 marks)

Question 8 - Mass Transport in Plants

(b) (ii) There is high light intensity so that means there is a greater rate of transpiration as more stomata are open.

Question 8 - Mass Transport in Plants

(b) (iii) The scientists also measured the diameter of the trunk of the tree on which the twig had been growing. The diameter was less at 12:00 than it was at 03:00 hours. Explain why the diameter was less at 12:00 hours. (2 marks)

Question 8 - Mass Transport in Plants

(b) (iii) At this time, the xylem is under a lot more tension as water is upped the trunk at a fast pace due to a high rate of transpiration.

Question 8 - Mass Transport in Plants

(c) Arteries and arterioles take blood away from the heart. Explain how the structures of the walls of arteries and arterioles are related to their functions. (6 marks)

Question 8 - Mass Transport in Plants

(c) The Elastic Tissue: Stretches under pressure Recoils so evens out pressure Muscle: Muscle contracts Reduces the diameter of the lumen Changes flow Epithelium: Epithelium smooth Reduces friction

Question 1 - Digestion of Proteins

(a) Endopeptidases and exopeptidases are involved in the hydrolysis of proteins. Name the other type of enzyme required for the complete hydrolysis of proteins to amino acids. (1 mark)

Question 1 - Digestion of Proteins

(a) Dipeptidases

Question 1 - Digestion of Proteins

(b) Suggest and explain why the combined actions of endopeptidases and exopeptidases are more efficient than exopeptidases on their own. (2 marks)

Question 1 - Digestion of Proteins

(b) Endopeptidases hydrolyse the peptide bonds between the amino acids in the central region of the polypeptide. This increases the surface area for the other enzymes.

Question 1 - Digestion of Proteins

(c) The diagram shows the co-transport mechanism for the absorption of amino acids into the blood by a cell lining the ileum. The addition of a respiratory inhibitor stops the absorption of amino acids. Use the diagram to explain why. (3 marks)

Img 2232 (binary/octet-stream)

Question 1 - Digestion of Proteins

(c) Respiration produces ATP. ATP is required for the active transport of NA+ out of the cell. If there is no respiration, no ATP can be produced causing a build-up of Na+ in the cell. This means there is no concentration gradient between the cell and outside of it. So no Na+ is brought into the cell so neither are any amino acids because the two molecules are co-transported together.