CONTEXT POINT 2: Plants and animals transport dissolved nutrients and gases in a fluid medium.

CONTEXT POINT 2: Plants and animals transport dissolved nutrients and gases in a fluid medium. Identify the form(s) in which each of the following is carried in mammalian blood: Carbon dioxide 70% as hydrogen ions (HCO 3- ). 7% as CO 2 dissolved in plasma. 23% carried by haemoglobin as (carboxyhaemoglobin). Oxygen 98% as oxy-haemoglobin (HbO 2 ) in red blood cells. 2% as oxygen dissolved in plasma. Water Salts Solvent of plasma and comprises about 60% of the volume of blood. Dissolved in plasma. Lipids As lipoproteins, triglycerides and cholesterol. Nitrogenous waste As urea, uric acid and creatinine dissolved in plasma. Other products of digestion Also dissolved in the plasma are amino acids, sugars, glycerol, nitrogenous bases, hormones and vitamins. QUESTION 17 Which of the following correctly responds to the main mode of transport of the named substances in the blood? Water CO 2 Salts A Plasma Leucocytes Red Blood Cells B Plasma Red Blood Cells And Plasma Plasma C Haemoglobin Haemoglobin Plasma D Leucocytes Plasma Kidneys The School For Excellence 2016 Trial Exam Revision Lectures Biology Book 1 Page 19

Explain the adaptive advantage of haemoglobin. HAEMOGLOBIN STRUCTURE Haemoglobin is a complex molecule made up of t main parts; the protein part (the globin), made of four polypeptide chains, and the haem group (which contains ) that is inside each folded polypeptide. oxygen molecules can be carried by each haemoglobin molecule. Once 4 oxygen molecules have combined, each with an iron ion, the molecule is known as oxyhaemoglobin. Hb + 4O 2 Hb(O 2 ) 4. HAEMOGLOBIN FUNCTION Haemoglobin transports oxygen from areas of high oxygen concentration (the ) to areas of low oxygen concentration (the surface of cells). The ease with which the oxygen bonds with the haemoglobin molecule depends on the surrounding concentration of oxygen. In high oxygen concentration levels, it easily picks up oxygen. In low oxygen concentration areas (such as near cells), the oxygen is easily released from the haemoglobin, and so enters areas where it is needed. Haemoglobin can also transport some carbon dioxide although most travels in the plasma as a carbonate ion. HAEMOGLOBIN ADAPTIVE ADVANTAGES Haemoglobin increases the amount of oxygen that can be carried in the blood, therefore it is an adaptive advantage for organisms that need a large supply of oxygen. The structure of haemoglobin is also an adaptive advantage because it l binds to oxygen at the respiratory surfaces and easily releases oxygen from the capillaries near the cells of the body that require it. If oxygen were to be transported in the plasma rather than attached to haemoglobin inside the red blood cell, it would change the osmotic balance of the blood. Haemoglobin acts as a buffer in the blood by absorbing hydrogen ions that are left in the plasma when carbon dioxide reacts with water to form hydrogen carbonate ions. This prevents dramatic changes in blood ph that would affect normal metabolism. QUESTION 18 Identify the protein responsible for transporting oxygen in mammalian blood and explain two advantages it offers. (3 marks) The School For Excellence 2016 Trial Exam Revision Lectures Biology Book 1 Page 20

Compare the structure of arteries, capillaries and veins in relation to their function. Arteries carry blood from the heart. They have thick walls made of elastic fibres and muscle. When the heart beats, waves of blood are sent along the artery, and it is able to stretch (this is the bulging of the artery that you feel when you take your pulse). The blood in arteries is under very high. It is this pressure that forces the blood through the many branches of the circulatory system so that is can reach all the tissues of the body. The lumen has a smooth lining to allow the blood to pass more freely. Capillaries are the blood vessels, and can be seen only with a microscope. They have very thin walls, only one cell thick. As blood flows through a capillary, liquid ( tissue fluid ) leaks through the walls to bathe the surrounding cells. Cells remove the nutrients they need from the tissue fluid and add any waste products to it. Some of this fluid drains back into the capillary, in order to maintain blood volume. It is returned to the heart via the various organs that remove the excretory products (urea, carbon dioxide etc). Blood leaving a capillary has much less energy than blood entering one. White blood cells can also squeeze out of capillaries, to find and kill pathogens. Veins carry blood back to the heart. The pressure of this blood is, about one tenth of what it was when in the artery. To make it easier for the blood to get through, veins are bigger in diameter than arteries, have thinner walls and a wider lumen (hole). They have valves to prevent the backflow of blood. Return of blood to the heart is also helped by the movement of body muscles, which squeeze the blood along the veins. Figure 5: Cross-section of three types of blood vessels (Image taken from: http://www.coolschool.ca/lor/bi12/unit9/u09l01.htm) QUESTION 19 Using the diagram above, label one structural feature of the artery shown and then relate this structure to the function of the artery. (3 marks) The School For Excellence 2016 Trial Exam Revision Lectures Biology Book 1 Page 21

QUESTION 20 Blood travels around the body through arteries, veins and capillaries. Which of the following correctly describes the structure or function of each of these blood vessels? A Always carries oxygenated blood Artery Vein Capillary Always carries oxygenated blood Always carries waste products B Thick muscular walls Thin walls with valves Walls one cell thick C Takes blood to the heart Thick muscular walls Takes blood to and from heart D Carries blood under Carries blood under pressure variable pressure Thin muscular walls QUESTION 21 Construct a table to compare the three main types of blood vessels, relating the structure of each to its function and providing a diagram of each. (6 marks) The School For Excellence 2016 Trial Exam Revision Lectures Biology Book 1 Page 22

Describe the main changes in the chemical composition of the blood as it moves around the body and identify tissues in which these changes occur. The composition of blood changes as the blood moves around the body. Blood collects some substances from the tissues and releases others into tissues. Urea is a waste product produced by the liver and removed by the kidneys. The concentration of urea entering the kidneys is higher than the blood urea concentration leaving the kidneys. Glucose levels in blood rise after a meal but as glucose is removed by the liver and muscles (with the aid of hormones), its concentration returns to normal range of about 70 90 mg/100ml of blood. Hormones are produced in endocrine glands and travel to their target organ in the circulatory system. Most hormones usually involve a response that may take a long while to complete, so the concentration of some hormones is relatively stable. One exception is adrenalin, which produces an immediate response to protect the body. Levels of hormones in a person s body depend on their gender, as well as their age, diet, activity and other external stimuli. The gas oxygen is needed by all living cells that respire aerobically. The concentration of oxygen is highest in the pulmonary vein, which is taking newly oxygenated blood from the lungs to the heart. From here, oxygen-rich blood is then transported via the circulatory system to that need it. Oxygen-depleted blood returns to the heart, via the veins and is then pumped to the lungs for more oxygen. The gas carbon dioxide is formed as a waste product from cellular. It is excreted from the lungs, in exchange for oxygen. Carbon dioxide needs to be removed from the blood as it can influence the ph of blood and in turn inhibit essential metabolic processes. The highest concentration of carbon dioxide is found in the pulmonary a, which connects to capillaries around the alveoli in the lung. During exercise, carbon dioxide production increases and this then causes increased breathing and heart rate, so that the excess carbon dioxide can be removed quickly. QUESTION 22 Which main body system is responsible for excreting the metabolic wastes carbon dioxide and water? A B C D The stomatal system. The excretory system. The endocrine system. The respiratory system. The School For Excellence 2016 Trial Exam Revision Lectures Biology Book 1 Page 23

QUESTION 23 Describe two main changes in the chemical composition of the blood as it moves around the body and identify the tissue(s) in which these changes occur. (3 marks) The School For Excellence 2016 Trial Exam Revision Lectures Biology Book 1 Page 24

Outline the need for oxygen in living cells and explain why removal of carbon dioxide from cells is essential. WHY OXYGEN IS NEEDED Oxygen is needed by cells for the energy releasing process of respiration. Without energy, cells cannot function and the organism will die. glucose + oxygen water + carbon dioxide + energy (ATP) WHY CARBON DIOXIDE NEEDS TO BE REMOVED Carbon dioxide needs to be removed as it l the blood ph, that is, makes it more acidic. This is because carbon dioxide reacts with water to produce carbonic. The increased acidity decreases the capacity for haemoglobin to carry oxygen and affects enzyme functioning (as enzymes work best at a specific ph) which in turn affects metabolic processes. QUESTION 24 State why oxygen is essential for all cells and outline why it is necessary for carbon dioxide to be removed from animal cells. (3 marks) The School For Excellence 2016 Trial Exam Revision Lectures Biology Book 1 Page 25

Perform a first-hand investigation to demonstrate the effect of dissolved carbon dioxide on the ph of water. FIRST HAND INVESTIGATION Make sure you are able to write up all or any part of the experiment you conducted and discuss features such as accuracy, reliability and validity. DISSOLVING CARBON DIOXIDE In class you would have carried out an investigation to dissolve carbon dioxide into water. You could have done this by either blowing through a straw into water, or reacting two chemicals such as an acid and a carbonate and bubbling the reactant carbon dioxide through water. MEASURING THE ph This would have been done before and after dissolving the carbon dioxide into the water so that the effect could have been measured. You could have done this qualitatively with universal indicator or quantitatively (and more accurately) with a ph meter. QUESTION 25 Describe an investigation that you have carried out to demonstrate the effect of dissolved carbon dioxide on the ph of water. (3 marks) The School For Excellence 2016 Trial Exam Revision Lectures Biology Book 1 Page 26

Perform a first-hand investigation using the light microscope and prepared slides to gather information to estimate the size of red and white blood cells and draw scaled diagrams of each. FIRST HAND INVESTIGATION In class you will have examined whole blood on a microscope slide, calculated the scale and the size of red and white blood cells and drawn scaled diagrams of them. Make sure you can describe your method and results. RED BLOOD CELLS Red blood cells would have appeared round with a pale centre (due to being thinner in the middle because of the biconcave shape). They are smaller than white blood cells and more n. WHITE BLOOD CELLS There are many different kinds of white blood cells, but they can be identified because they are often larger than red blood cells and contain one or more purple. There are not as many white cells as red cells in a normal human blood count. SCALED DIAGRAMS To estimate the scale you would have used a grid of known size and estimated the diameter of the field of view in millimetres. To convert this to μm, x 1000. Using this grid you can estimate the diameter of a red blood cell and a white blood cell. The School For Excellence 2016 Trial Exam Revision Lectures Biology Book 1 Page 27