BIO(8) Past Paper PDF

8. TRANSPORT IN ANIMALS AND PLANTS 8.1 Transport system in mammals Learning outcome: (a) Describe the structure of a mammalian heart (b) Define systole and diastole, and explain the sequence of events in a cardiac cycle including changes in pressure and volume in aorta ,lef...

8. TRANSPORT IN ANIMALS AND PLANTS 8.1 Transport system in mammals Learning outcome: (a) Describe the structure of a mammalian heart (b) Define systole and diastole, and explain the sequence of events in a cardiac cycle including changes in pressure and volume in aorta ,left atrium and left ventricle (c) Describe the initiation and regulation of heart beat (d) Explain hypertension, atherosclerosis, arteriosclerosis and myocardial infarction, and state their causes and preventions (e) Describe the lymphatic system in relation to the blood circulatory system (f) Determine the direction of fluid movement at the arterial and venous ends of the capillaries by calculating the differences between osmotic pressure/solute potential and hydrostatic pressure. (a) The Structure of a mammalian heart ▪ Situated between lungs and behind sternum, within thorax ▪ Surrounded by fibrous sac, pericardium containing pericardial fluid. ▪ Pericardium is a thin, transparent, non elastic double layered sac. ▪ Pericardium prevents the heart from getting overstretch. ▪ Pericardial fluid reduces friction between the heart and the surrounding tissues when the heart is beating. ▪ There are 4 chambers in the heart: two upper thin-walled atria and two lower thick-walled ventricle. ▪ The atria function to collect and retain blood temporarily until it can pass to the right ventricle. ▪ The right atrium receives deoxygenated blood from the general circulation of the body ▪ The left atrium receives oxygenated blood from the lungs ▪ The right ventricle pumps blood to the lung via pulmonary artery. ▪ The left ventricle pumps blood to the systemic circulation via the aorta. ▪ A septum separates the right chambers from the left chambers to permit the separation of oxygenated blood and deoxygenated blood ▪ The walls of the left ventricle are much muscular compared to the walls of the right ventricle because the left ventricle have to pump blood out of the heart ▪ The left atrium is separated from the left ventricle by a bicuspid valve, whilst a tricuspid valve separates the right atrium from the right ventricle, to prevent blood from flowing back into the atrium. ▪ Pulmonary and aortic pocket valves/semilunar valves which are situated at the point of entry into the pulmonary artery and aorta respectively , prevent the flow of blood back into the ventricle. 1  Structure of the human heart ▪ Coronary artery supply oxygenated blood to the walls of the heart ▪ the walls of the heart are composed of cardiac muscle fibres; whose fibres branch and cross-connect with each other to form a complex net-like arrangement. This permits contraction waves to spread quickly and enhance the contraction of the chambers as a whole. (b) Cardiac cycle ▪ Refers to the sequence of events which takes place during completion of one heart beat ▪ It consists of alternating periods of systole (contraction and emptying) and diastole (relaxation and filling) Sequence of events during cardiac cycle. i. Atrial and ventricular diastole 2  ▪ Atrial and ventricle muscles relaxed ▪ Volume increases and pressure decreases ▪ Deoxygenated blood, enters the right atrium and oxygenated blood enters the left atrium(blood enters atria from veins with higher pressure) ii. Atrial systole ▪ The two atria contract simultaneously ▪ Volume decrease , so pressure rises ▪ Ventricles muscles relax, so lower pressure ▪ Blood pushed from atria into the ventricle where the pressure is lower ▪ Atrio-ventricular valves open ▪ Semilunar valves shut iii. Ventricular systole ▪ Ventricles muscles contract, volume decrease, so pressure high ▪ Atrial muscle relax,pressure low ▪ The AV valves shut ▪ The ventricular pressure exceeds the blood pressure in the aorta and pulmonary artery ▪ forcing the semilunar valves to open ▪ blood is propelled into the aorta and pulmonary artery ▪ one complete heartbeat consists of one systole and one diastole and lasts for about 0.8s Graph to show the pressure and volume changes in the left side of the heart in the cardiac cycle of a human 3 The events shown above can be summarised as follows: ▪ A : atrium contracting (atrial systole), blood flows into ventricles ▪ B : ventricle starts to contract (ventricular systole), ventricular pressure exceeds atrial pressure so AV valve closes ▪ C: ventricular pressure exceeds aortic pressure forcing open semilunar valve, blood therefore flows from ventricle into aorta and ventricular volume decreases ▪ D: ventricular pressure falls below aortic pressure, resulting in closure of semilunar valve, ventricular volume starts to rise ▪ E: ventricular pressure falls below atrial pressure so blood flows from atrium to ventricle, ventricle volume rises rapidly ▪ F: atrium filling with blood from pulmonary vein, atrial pressure exceeds ventricular pressure so blood flows from atrium to ventricle ( AV valve open ) Heart sounds(phonocardiogram) ▪ Two heart sounds : ‘lub – dup’ ▪ The ‘lub’ sound occurs when the bicuspid and tricuspid valves close. ▪ The tone is low, not very loud and lasts for a fairly long time ▪ This happen when the pressure in the ventricles is higher than the atria.(to prevent backflow of blood from the ventricle to atrium) ▪ The ‘dup’ sound occurs when the semilunar valves close. ▪ The tone is high, louder and lasts shorter than the first ‘lub’ sound 4  ▪ This happen when the the pressure in aorta and pulmonary artery is higher than in ventricles (to prevent backflow of blood from aorta and pulmonary to ventricle) Electrocardiogram (ECG) ▪ Record of the electrical activity of the heart obtained. ▪ P waves correspond to wave of excitation spreading over atrium (atrium systole) ▪ QRS waves correspond to wave of excitation spreading over ventricles(ventricular systole) ▪ T waves is caused by ventricular diastole (c) Initiation and regulation of heartbeat (i) Initiation of heartbeat ▪ when a heart is removed from a mammal and placed in well-oxygenated Ringer solution at 370C , it will continue to beat rhythmically for a considerable time, without stimuli from the nervous or endocrine system ▪ cardiac muscle is therefore miogenic , its rhythmical contractions arising from within the muscle tissue itself ▪ the stimulus for contraction of the heart originates in a specific region of the right atrium called sino-atrial node (SAN), close to the point of entry of the venae cavae ▪ the SAN initiates the heart beat. ▪ The SAN is known as the pacemaker because each wave of excitation begins here and acts as the stimulus for the next wave of excitation. ▪ Waves of excitation from SAN spreads out smoothly across the atria. ▪ Both atria contract more or less simultaneously(atrial systole) ▪ Waves of excitation are then passed to atrioventricular node(AVN), a second group of specialised cells , located near the base of the atria ▪ The impulse is delayed for 0.1s after reaching the AVN ▪ From the AVN, waves of excitation are then passed to the bundle of His, then transmitted to a network of Purkinje fibres within the ventricle walls ▪ Both ventricles are stimulated to contract simultaneously, and the wave of ventricular contraction begins at the apex of the heart and spreads upwards squeezing blood out of the ventricles towards the arteries 5 (ii) Regulation of heart rate ▪ Demands which body makes on circulatory system are constantly changing i.e heart rate must be continuously adjusted accordingly ▪ Adjustment is by dynamic and integrated activity of 2 types of control system i.e nervous and non-nervous (chemical) ▪ The amount of blood flowing out of heart is known as the cardiac output. ▪ This is the volume of blood pumped (stroke volume) multiplied by the number of beats in a given time (heart rate) and is expressed in litres of blood per minute. Cardiac output = stroke volume x heart rate ▪ One way of controlling cardiac output is by varying the heart rate. Question: Calculate the cardiac output: (a) at rest when the stroke volume is 80cm 3 and the heart rate is 75 (b) during vigorous exercise when the stroke volume is 100cm 3 and heart rate is 150. 6  Nervous control of heart rate ▪ Nervous control is by reflex action ▪ Sensory nerves carry impulses to the cardiovascular control centre (containing an accelerator and an inhibitory centre) in the medulla oblongata in the brain. ▪ The heart is served by two nerves of the autonomic nervous system, the sympathetic and parasympathetic nervous systems, the actions of which are antagonistic. ▪ The vagus nerve, part of the parasympathetic nervous system , originates in the inhibitory centre Neurones connecting the heart to the cardiovascular system ▪ Stimulation of the vagus nerve cause a release of acetycholine in the sinoatrial node(SAN) and the atrio-ventricular node (AVN) and the heart musle. ▪ This slows down the rate of heartbeat but does not affect the force of ventricular contraction ▪ The sympathetic nerve, part of the sympathetic nervous system originates at the accelerator centre. ▪ Impulse from cardiac acceleratory transmitted to SAN through sympathetic nerve ▪ Stimulation of the sympathetic nerve causes a release of noradrenaline which stimulates both the rate of heartbeat and also the force of ventricular contraction. Non-nervous control of heart rate Hormonal control ▪ the hormone adrenaline is secreted by the adrenal medulla glands during times of stress. ▪ adrenaline diffuses into the blood and is carried in the blood to the heart ▪ the effect of adrenaline on the heart is to speed up the heart rate, by stimulating the SAN to increase the frequency of waves of excitation. other non-nervous stimuli which act directly on cardiac muscle or on the S-A node are: ▪ high pH : decelerates ▪ low pH (e.g high CO2 levels, as is the case during active exercise) : accelerates ▪ low temperature : decelerates ▪ high temperature : accelerates 7 7/2010 With the aid of a labelled diagram, describe the mechanism and control of heart beat. For diagram: (i) SA node and AV node (ii) Purkinje fibres and bundle of His (iii) Left ventricle, right ventricle, left atrium and right atrium (iv) Sympathetic and vagus/parasympathetic nerve Mechanism: Cardiac muscle is ……………………. the heart beat starts at ……………………… the impulse from the pace maker spreads across both ……………………. both atria contract/…………………………………………. the impulse reach the ………………………. the impulse is delayed for ……………… after reaching AVN impulse travel through ………………………. to ……………………………………. then spread to all parts of both …………………………….. both ventricles contract/……………………………………. Control cardiovascular control centre located in the ……………………. ……………………. the heart is supplied by two nerves; …………….. and …………………………….. impulse from cardiac inhibitory centre transmitted to SAN through ……………….. nerve vagus nerves ……………………… …………………….. the rate of heart beat impulse from cardiac acceleratory transmitted to SAN through ………………… nerve sympathetic nerves ………………… …………… the rate of heart beat adrenaline, thyroxine, epinephrine, low pH, high CO 2 concentration and high temperature ………………… ……………. the rate of heart beat 8  (d) Cardiovascular diseases ▪ Are disorders of the heart and blood circulation. They are the leading causes of death in the country ▪ The most common disorders are hypertension and arterioschlerosis.They affect blood circulation which can lead to myocardial infarction (heart attack). (i) Hypertension Definition: ▪ A condition when arterial blood pressure is chronically/persistently elevated above normal level(140/90) Causes: ▪ Heredity/genetic ▪ High salt intake ▪ Stress ▪ Smoking Prevention: ▪ Change diet/reduce salt intake ▪ Regular exercise ▪ Stress free lifestyle ▪ Avoid smoking (ii) Arterioschlerosis Definition: ▪ A condition where arteries thicken and lose their elasticity or a condition where arteries harden Causes: ▪ Cholesterol and other lipids build up in the artery walls/plaque ▪ Narrowing the lumen ▪ Deposition of calcium ions Prevention: ▪ Reduce fat/cholesterol-rich diet ▪ Increase high fibre diet ▪ Regular exercise (iii) Myocardial infarction ▪ Occurs when there is death of some of the muscle cells of the heart as a result of a lack of supply of oxygen and other nutrients. ▪ It is caused by the closure of the artery that supplies a particular part of the heart muscle with blood 6/2005 (a) Give the definition, causes and methods of prevention of each of the following cardiovascular diseases. (i) Hypertension (ii) Arteriosclerois K2/18/2013 (a) Describe the development of atherosclerosis , and how it may lead to myocardial infarction. [9 marks] Thickening of the inner arterial wall// Narrowing of arterial lumen Due to deposits of fatty materials/cholesterol Forming plaque (atheromatous) When the plaque becomes calcified 9  The arterial wall becomes hardened Condition known as arteriosclerosis This leads to the formation of blood clot/thrombus The thrombus may dislodge and carried around in the circulatory system The embolus formed will obstruct the coronary artery A region of the heart muscle is deprived of its oxygen supply Causing death of the heart muscle 10 11 12 (e) Lymphatic system ▪ Is a network of fine vessels, connected to many small organs called lymph nodes ▪ supplements the work of the circulatory system ▪ Lymphatic system absorbs and returns tissue fluids into blood circulation system ▪ also helps to defend the body Organisation of lymphatic system ▪ the lymphatic system consists of lymphatic capillary, lymphatic vessel , thoracic ducts and right lympathic duct which return tissue fluids to the blood ▪ the lymphatic system is also made up of lymphoid organs such as lymph nodes , tonsil , spleen and bone marrow, which have specific functions in assisting immunity ▪ lymphatic capillaries: - are the smallest of the vessels of the lymphatic system - are blind-ended capillaries which are permeable to water and solutes - are equipped with endothelial valve at the tip of the capillaries to allow interstitial fluid enter the capillaries and prevent the escape of lymph from the capillaries - Join to form the lymphatic vessels which later merge to form either the thoracic duct or the right lymphatic duct. ▪ Lymphatic vessels - have one way direction which direct the flow of lymph towards the larger veins ▪ Thoracic duct - is much larger than the right lymphatic duct and drains fluid from the lower extremities, the abdomen, the left arm and the left side of the head and neck to the subclavian vein in the thoracic region. Right lymphatic duct ▪ serves the right arm, the right thoracic area, the right side of both the head and neck ▪ the lymphatic ducts join the blood system at the subclavian vein Function of lymphatic vessel/capillaries: returns tissue fluid to the blood 13 Lymphoid organs of the lymphatic system Organs/structures features function Lymph nodes - are small round structures - to trap /filter pathogens as found at specific points along well as foreign materials the lymphatic vessels and found in the lymph contain numerous - lymphocytes produces lymphocytes and antibodies macrophages - Macrophages remove /destroy pathogens /foreign bodies Tonsils - are patches of lymphatic - defence against bacteria tissue located at the pharynx and other foreign bodies which enter the body by the way of nose and mouth Spleen - is located near the stomach - to remove worn out red blood cells and bacteria from the blood - produce antibodies Thymus - is located behind the - site of development of T sternum in the upper lymphocytes thoracic cavity near the heart Red bone marrow - persists in the skull bones, - site of origin of all types of clavicle,vertebrae, sternum blood cells e.g lymphocytes and pelvic bones Lacteal - a narrow tubular sac in the - absorbs fatty acid and centre of villus joined at its glycerol and transports them lower end to one of the many to the circulatory system lymphatic vessels found in the walls of small intestine 6/2004 (a)Name the organs and structures of the lymphatic system and describe their functions. Formation of lymphatic fluid ▪ At the capillary bed throughout the body, fluid from the blood is filtered out of the capillaries by a process called ultrafiltration which is controlled by the hydrostatic and osmotic pressure of the blood. ▪ At the arteriole end of the capillary, the hydrostatic pressure of the blood is higher (due to pressure from the pumping of the heart) than the osmotic pressure. ▪ The high hydrostatic pressure tends to push the fluid out of the blood. ▪ The fluid which is filtered out of the capillaries is known as tissue fluid or interstitial fluid which bathes the cells. ▪ Tissue fluid contains water, glucose, amino acids, oxygen and other soluble products of digestion, hormones but no protein. ▪ exchange of gases and solutes takes place between the tissue fluid and the cells ▪ nutrients and oxygen pass to the cells, waste like carbon dioxide and urea pass to the tissue fluid. ▪ at the venule end most of the tissue fluid is absorbed into the blood 14  ▪ due to the high osmotic pressure caused by the presence of proteins and low hydrostatic pressure. ▪ Not all tissue fluid is absorbed into the bloodstream at the venule end of the capillary ▪ Some of the tissue fluid enters the lymphatic capillaries and is transported in the lymphatic system ▪ This fluid is known as lymph ▪ Lymph is a colourless or pale yellow fluid which has a composition similar to blood plasma but with more proteins and fatty acids ▪ The lymph moves into the lymphatic vessels through the lymph nodes and delivers its contents into the bloodstream at the junction of the left and right subclavian veins. ▪ The lymph is moved through the vessels by the contraction of muscle during walking and breathing and the backflow is prevented by valves present in the vessels. Relationship between the blood and the lymphatic system Functions of lymphatic system 15  ▪ Takes up water and plasma proteins that seep out of blood capillaries, then returns them to circulating blood ▪ Lacteal (part of lymphatic system) transports absorbed fats ▪ Defence mechanism: - lymph nodes filter pathogens, which are then seized by macrophages inside the nodes - lymph nodes also produces lymphocytes (f) Determination of the direction of fluid movement at the arterial and venous ends of the capillaries by calculating the differences between osmotic pressure/solute potential and hydrostatic pressure. Refer to page 42 and 43(Ace Ahead –Oxford) K2/2013/18(b) Describe the movement of fluid between blood and interstitial fluid. [6 marks] Hydrostatic pressure and osmotic pressure are responsible for fluid movement. Net pressure is calculated using the formula (HPblood + OPblood) - (HPinterstitial fluid + OPinterstitial fluid) (Blood ) hydrostatic pressure is higher than the osmotic pressure at the arterial end of a capillary (Net pressure is positive) This forces plasma out of the capillary into the interstitial space Forming interstitial/tissue fluid (Blood ) hydrostatic pressure is lower than the osmotic pressure at the venous end of a capillary (Net pressure is negative) This draw fluids from the interstitial space into the blood More fluid leaves the blood than returns 90% of the interstitial fluid is returned to the blood Remaining fluid will enter the lymphatic system 10% enter the lymphatic system 16 17 18  8.2 Transport system in vascular plants Learning outcome (a) explain the uptake of water and mineral ions from the soil by the root hairs involving water potential (b) describe the apoplast, symplast and vacuolar pathway of water movement through the root tissues (c) describe the root pressure, cohesion-tension theory and transpiration pull in relation to water movement from the root to leaves (d) explain translocation using the mass flow, electroosmosis, cytoplasmic streaming and peristaltic waves hypothesis (e) explain the concept of source and sink, and phloem loading and unloading in translocation according to pressure flow hypothesis ▪ The main transport system in plants are the vascular system which consists of highly specialised tissues called xylem and phloem. ▪ Xylem (vessels) transport/translocate mainly water, mineral salts, some organic nitrogen and hormones from the roots to the aerial parts of the plant/leaves. ▪ Phloem translocates photosynthetic products from the leaves to other parts of the plants. ▪ The movement of substances through the conducting or vascular tissues of plants is termed translocation. (a)The uptake of water and mineral ions from the soil by the root hairs. (i) Uptake of water by roots ▪ Water is absorbed mainly by the root hair. ▪ Root hairs are tubular extensions of epidermal cells with thin walls and greatly increased the surface area for uptake of water and mineral salts. ▪ The soil solution has a higher water potential than cells of the root hairs. ▪ Water therefore enters the root from the soil by osmosis. ▪ Once in the root hair cells, water passes across the parenchyma cells making up the cortex, to the xylem vessel. ▪ Water can then be transported to all parts of a plant in the xylem vessel. 19  (ii) Uptake of mineral salts/ions ▪ Plants require certain mineral elements in addition to the carbohydrates made in photosynthesis ▪ In green plants minerals are taken up from the soil in terrestrial plants and from the surrounding water in aquatic plants by active transport in the form of ATP. ▪ Mineral ions mainly enter root hair cells by active transport. ▪ In active transport an input of energy in the form of ATP is required , as ions are moving against the concentration gradient. ▪ Mineral ions can also enter roots by diffusion. ▪ This occurs when the concentration of a mineral ion in the soil is higher than its concentration in the root hair cell. ▪ No input of energy is required ▪ When the ions have been absorbed by the root hairs, the ions move towards the vascular tissues.(xylem) (b) From root hair to xylem ▪ Water and ions move across the root in three pathways. (i) the apoplast pathway: through the cell wall (ii) the symplast pathway: through the cytoplasm (iii) the vacuolar pathway: through the vacuole (i) the apoplast pathway ▪ water moves through the spaces (between intercellular fibres) of the cell wall ▪ Cohesion forces between the water molecules enable the stream of water to be pulled along the cell wall in a continuous stream ▪ however the movement of water is stopped by the Casparian strip of the endodermal cells ▪ hence water passes through the plasma membrane ▪ and enter the cytoplasm of the endodermis cell (through the symplast pathway) (ii) the vacuolar pathway ▪ water moves from one vacuole to another vacuole in the neighbouring cells ▪ from a higher water potential to a lower water potential (iii) the symplast pathway ▪ water moves through the cytoplasm of one cell to another ▪ through plasmodesmata. 20 6/2008 (a) The transportation of water molecules and mineral ions from the soil to the roots could occur via several pathways such as vacuole, apoplast and symplast.Describe these three pathways. Vacuole pathway the movement of water and mineral ions from higher water potential to lower water potential from a vacuole to vacuole of another. Apoplast pathway water and mineral ions move through the spaces of the extracellular and cell wall. cohesion forces between water molecules enable the stream of water and mineral ions to be pulled along the cell wall the movement is hindered by the Casparian strip in the endodermis hence water and mineral ions pass through the plasma membrane. water and mineral ions enter the cytoplasm of the endodermis cell Symplast pathway water and mineral ions moves through the cytoplasm of one cell to another through plasmodesmata. (c) Ascent of water in the xylem ▪ water moves up the stem and into the leaves through root cells and xylem. ▪ the theory of the mechanism by which water moves up the xylem is known as the cohesion tension theory. ▪ The transpiration of water from the leaves draws water across the leaves ▪ This water is replaced by the entering the mesophyll cells from the xylem by osmosis. ▪ As water molecules leave xylem cells in the leaf, they pull up other water molecules. ▪ This pulling effect is known as the transpiration pull. ▪ The transpiration pull creates a negative pressure in the columns of water in the xylem cells. 21  ▪ This is transmitted back down the stem all the way to the root by cohesion of water molecules. ▪ The cohesive forces of the water molecules allows water to stay in a continuous stream. ▪ Cohesive forces are forces of attraction between water molecules caused by the formation of hydrogen bonding. ▪ Adhesive. forces between the water molecules and the walls of xylem vessels help water to rise in the xylem ▪ A phenomenom known as capillary action ( the narrower the tube, the more water can stick to the wall) ▪ Another force involved in water movement up the xylem is root pressure. ▪ Root pressure refers to the force generated in the root to push water up the stem. ▪ Root pressure is the result of osmotic flow across the endodermis. ▪ Active secretion of salts or other solutes from the endodermis into the xylem sap lower its water potential ▪ Water then moves into the xylem from adjacent root cells. ▪ The process is inhibited by respiratory inhibitors such as The ways of demonstrationg root pressure in a potted plant cyanide, lack of oxygen and low temperatures. Water passes up the xylem vessel by: o Transpirational pull – water is ‘pulled’ up o Cohesion force – water sticks to water o Adhesive force – water sticks to xylem vessel o Root-pressure – water is ‘pushed’ up (d) Phloem and Translocation. Translocation ▪ Is the transport of organic solutes/photosynthetic products from the leaves or source to other parts of the plants or sink through the phloem tissue Structure of phloem ▪ Phloem is a living tissue consisting of sieve tube and companion cells. 22  ▪ Sieve tubes consist of narrow , elongated cells or sieve elements which are joined end to end to form a system of tubes that runs throughout the plants. ▪ The end walls form the sieve plates that are perforated by pores. ▪ The pores allow the cytoplasmic filaments/strands which are present in the sieve tubes to flow from one sieve element to the next ▪ Cytoplasmic strands contain no endoplasmic reticulum, mitochondria, chloroplast and nucleus. ▪ Certain organelles if present are found lining the inside of the thin cellulose cell wall ▪ This presents less barrier to the flow of sap through the sieve elements ▪ Companion cells are arranged close to the sieve cells. ▪ Companion cells contain nucleus and the cytoplasm is rich in mitochondria and other organelles and are metabolically active ▪ Companion cells are connected to the sieve tube elements by plasmodesmata. Diagram of sieve tube and companion cells Evidence to show phloem as the site of translocation (i) the experiment with aphids ▪ The aphid that is feeding on the cell sap is anaesthetised by passing a stream of carbon dioxide gas ▪ the proboscis is cut off, leaving the mouthparts in situ ▪ the sap that exudes are collected and are analysed chemically ▪ the chemical analysis shows that the sap contains sugar. 23  (ii) bark ringing ▪ the removal of a ring of bark around the trunk of a woody plant ▪ takes away all tissues external to the xylem ▪ after several weeks the region above the ring becomes swollen due to accumulation of organic solutes (iii) the use of radioactive carbon as a tracer ▪ carbon dioxide labelled with radioactive carbon (14CO2) ▪ is fed to green leaves in the light ▪ radioactive carbon (14CO2) is then turned into radioactive sugars, which are transported about the plant ▪ the movements of the labelled sugars can be followed by sectioning tissues and locating the radioactivity by autoradiography ▪ in autoradiography, the dried tissues are placed onto photographic films in the dark for few days Location of 14C-labelled sugars in stem ▪ the films are developed to produce section by autoradiography radioautographs ▪ the presence of radioactivity in parts of tissues shows up as ‘fogging’ of the negatives 24 Hypothesis to explain translocation in plants (i) Pressure flow/mass flow hypothesis ▪ explains the movement of sugars(organic solutes) from a high-pressure region to a low- pressure region through the phloem sieve tube. ▪ Movement of sugar involves source and sink ▪ Also involves phloem loading and unloading ▪ the organic solutes e.g sucrose synthesised in the mesophyll cells(source) are actively transported /loaded by transfer cells and companion cells into the sieve tube ▪ the high concentration of sucrose will lower the water potential of the solution inside the sieve tube ▪ water flows by osmosis into the phloem from the xylem and a high hydrostatic pressure is created. ▪ In the roots(sink) sugars are actively removed from the sieve tubes thus increase the water potential in the sieve tubes. ▪ Water flows out of the sieve tubes into the xylem by osmosis. ▪ With less water present, the hydrostatic pressure falls. ▪ The gradient in hydrostatic pressure between source and sink causes the passive flow /result in continuous flow of water and dissolved solutes from the source to the sink. ▪ This hypotheses can be explained by the Munch model. 25 ▪ The hydrostatic pressure developed in bulb A forces the sugar solution into B; mass flow continues until the concentration of sugar in A and B are equal 26 27 28 ii. cytoplasmic streaming ▪ Involves a circular movement of cytoplasm (cyclosis) from one end of the sieve tube element to the other end ▪ Responsible for bidirectional movements along individual sieve tubes ▪ The solute or sucrose are transported along cytoplasmic strands across sieve plates ▪ by active transport (using energy from the companion cells) iii. electro-osmosis ▪ ATP generated by the companion cells are used to withdraw ions, such as potassium ions from one of the sieve tube into the companion cell then secreting them on the other side of the sieve plate ▪ Accumulation of potassium ions/K+ creates gradient of electrical potential across the sieve plate ▪ This causes an electro-osmotic flow of polar water molecules and dissolved solutes(sugars) through the sieve pores of the sieve plates iv. peristaltic waves ▪ transcelluar strands present in phloem sieve tubes contain contractile proteins ▪ transcelluar strands are connected from one sieve tube to the other through pores ▪ dissolved solutes move through the transcellular strands by peristaltic waves of contraction ▪ movement is in a one way direction ▪ requires energy (ATP) from the companion cells 29 TOPIC : TRANSPORT 5/1988 (a) Jelaskan apa yang dimaksudkan dengan istilah sistol, diastol dan kitar kardiak dalam tindakan jantung. (b) Huraikan struktur otot jantung dan jelaskan bagaimana denyutan jantung bermula. 5/1990 (a) Jelaskan kepentingan peredaran pada haiwan dan translokasi pada tumbuhan. (b) Jelaskan dengan ringkas bagaimana struktur hemoglobin sesuai dengan peranannya sebagai pengangkut oksigen. (c) Jelaskan dengan ringkas bagaimana pergerakan bahan larutan berlaku di dalam floem. 3/1991 (a) Jelaskan bagaimana tekanan akar, jeleketan dan lekatan dapat menyebabkan pergerakan air dan pergerakan garam galian dalam tumbuhan. (b) Huraikan tiga faktor persekitaran yang dapat mempengaruhi kadar kehilangan air daripada tumbuhan. (c) Perihalkan tiga ciri tumbuhan xerofit yang dapat menghalang kehilangan air daripada tumbuhan. 5/1992 (a) Huraikan dengan ringkas dua ujikaji yang dapat membuktikan peranan floem dalam translokasi gula pada tumbuhan. (b) Jelaskan dua hipotesis yang dapat menerangkan mekanisme pengangkutan gula di dalam floem tumbuhan. 6/1993 (a) Selain air dan karbon dioksida, tumbuhan memerlukan unsur-unsur mineral juga untuk pertumbuhan. Perihalkan bagaimana tumbuhan mendapat unsur 2 mineral ini. (b) Apakah translokasi? Perihalkan struktur tisu vaskular yang terlibat dalam translokasi. 5/1994 (a) Bincangkan mekanisme aliran jisim dan mekanisme aliran sitoplasma untuk menerangkan pengangkutan bahan-bahan organik pada tumbuhan. (b) Huraikan struktur tisu tumbuhan yang terlibat dalam mekanisme-mekanisme pada (a). 5/1997 (a) Huraikan bagaimana denyutan jantung dikawal atur untuk mengepam darah keseluruh badan. 30 (b) Huraikan cara lintasan air dari satu sel ke satu sel dalam akar. 3/1999 (a) Jelaskan dengan ringkas kepentingan transpirasi pada tumbuhan. 5/2002 (a) Huraikan struktur jantung mamalia yang disesuaikan dengan fungsinya sebagai organ pengepam darah. (b) Jelaskan bagaimana denyutan jantung bermula dan bagaimana kadar denyutan dikawalatur. 6/2005 (a) Give the definition, causes and methods of prevention of each of the following cardiovascular diseases. (iii) Hypertension (iv) Arteriosclerois (b) With the aid of Munch model, describe the mechanism of mass translocation in phloem. 6/2008 (a) The transportation of water molecules and mineral ions from the soil to the roots could occur via several pathways such as vacuole, apoplast and symplast.Describe these three pathways. (b) Among the mechanisms of the translocation of sugar through sieve tubes are the mass-flow hypothesis, the electro-osmosis and the cytoplasmic streaming.Describe these three mechanisms. 7/2010 With the aid of a labelled diagram, describe the mechanism and control of heart beat. 5/2002 (a) Huraikan struktur jantung mamalia yang disesuaikan dengan fungsinya sebagai organ pengepam darah. (a) Struktur jantung Fungsi - terdiri daripada otot kardium - miogenik/mengecut berterusan/beritma - dibahagi kepada 4 ruang - menerima/mengepam darah - atrium kanan dan ventrikel kanan dan atrium - supaya darah beroksigen dan ternyahoksigen kiri dan ventrikel kiri dipisahkan oleh septum tidak bercampur - dinding ventrikel kiri lebih tebal daripada - menghasil tekanan tinggi/ mengepam darah ventrikel kanan keluar daripada jantung ke seluroh badan 31  - mempunyai saraf autonomi/saraf - mengawal kadar denyutan parasimpatatik dan simpatatik - injap semilunar/ AV - pengaliran darah sehala - dibekali oleh salur darah vena kava - membawa darah masuk ke jantung - salur darah keluar/aorta - membawa darah keluar daripada jantung - arteri koronari - membekal darah/nutrien dan oksigen kepada otot jantung - ada SAN - memulakan/mencetuskan denyutan jantung - ada AVN - menyebar impuls ke berkas His/tisu Purkinje - tisu Purkinje/berkas His - menyebar impuls ke seluroh ventrikel (b) Bagaimana denyutan jantung bermula: - otot jantung bersifat miogenik - denyutan jantung bermula di SAN - gelombang ujaan /impuls tersebar dari SAN ke dinding atrium - ujaan /impuls sampai di AVN - AVN mengalirkan impuls ke berkas His - seterusnya disebarkan ke tisu Purkinje - seterusnya ke seluroh dinding ventrikel - menyebabkan hantung mengecut - SAN menghantar gelombang impuls berterusan Bagaimana dikawal: - kadar denyutan dikawal oleh medula oblongata - melalui saraf dan hormon - saraf vagus/parasimpati – melambatkan denyutan jantung - saraf simpati – mempercepatkan denyutan jantung - hormon adrenalin – mempercepatkn denyutan jantung 6/2005 Transport (Animals & Plants) 1. In a study of the movement of substances in plants, aphids were used.The study showed that A translocation occurred in two ways B translocation occurred electro-osmotically C the phloem was responsible for the transportation of organic substances D the xylem was responsible for the transportation of water and minerals 32 2. The graph below shows the changes in pressure in the atrium, ventricle and aorta during a complete cardiac cycle. Based on the graph, which statement about the regulation of blood pressure is not true? A Blood pressure is highest in the artery when the heart muscles contract during ventricular systole B X represents ventricular pressure, Y represents atrial pressure and Z represents aortic pressure C Changes in cardiac output and diameters of blood vessels are among important factors which control blood pressure D An increase in blood pressure causes the vasomotor centre to transmit information through the parasympathetic system to the arteriol, causing the arteriol to undergo dilation and the blood pressure to decrease 3. Which of the following statements are true about the Casparian strip? I it covers the whole endodermis cell II it consists of suberin which is impermeable to water III it is a thickening strip of endodermis cell IV it ensures that water crosses the root through the apoplast only A I and II B I and IV C II and III D II and IV 4. The table below shows the heart sound activities and their causes. Heart sound activity Cause 33  (a) First heart sound I closing of semilunar valves (b) Second heart sound II closing of bicuspid and tricuspid valves III occurs during ventricular systole IV occurs during ventricular diastole Which of the following is correct for the heart sound activities and their causes? I II III IV A (a) (a) (b) (b) B (a) (b) (a) (b) C (b) (a) (a) (b) D (b) (a) (b) (a) 5. Which of the following explain how water molecules are transported in the root? I through vacuole II through apoplast pathway III through symplast pathway IV mass flow mechanism V protoplasm flow mechanism A I,II and III B I,III and V C I,IV and V D II,III and IV 6. If a cell with an initial water potential of ψ = -0.8mPa is placed in a solution with a water potential of ψ = -0.6mPa , the cell will A absorb the water B plasmolyse C lose its water D become flaccid 7. Which of the following statements about the control of heart beat is true? A the secretion of adrenaline increases the rate of heart beat B the decrease in blood pH inhibits neurons in the chemoreceptors at the aorta and carotid artery. C the propagation of impulse through the sympathetic nerve towards the sinoatrial and atrioventricle nodes decreases the rate of heart beat D the propagation of impulse through the parasympathetic nerve towards the sinoatrial and atrioventricle nodes increases the rate of heart beat 8. Which of the following is true of atrioventricle node? A it acts as a pacemaker B it initiates atrial systole C it initiates ventricular systole D it is controlled by the cardiovascular centre 9. Which of the following is the role of the Casparian strip in the endodermis cell of the root? A to carry out active transport 34  B to strengthen the root structure C to ensure that the water loss through transpiration can be replaced D to ensure that water and minerals enter the vascular tissues via the symplastic route 10. Which of the following events occur during ventricular systole? Tricuspid valves bicuspid valves semilunar valves A open open close B close close open C open close close D close open open 11. the opening of the semilunar valves at the aorta occurs during A atrial systole B atrial diastole C ventricular systole D ventricular diastole 12. Which are true of the sinoatrial node? I it is situated at the posterior wall of the right atrium II it acts as the pacemaker III it can start the contraction of the atrium and ventricle almost simultaneously IV it causes the contraction of the left and right ventricles almost simultaneously A I and II B I and IV C II and III D III and IV 13. What happens when the ventricles of the heart contract? I the semi-lunar valves open II the semi-lunar valves close III the atrioventricular valves open IV the atrioventricular valves close A I and III B I and IV C II and III D II and IV 14. The movement of water through the cell wall is called A alternative B apoplast pathway C symplast pathway D vacuolar pathway pathway 15. Which blood vessel supplies oxygen and nutrients directly to the myocardium? A Aorta B coronary artery C pulmonary vein D pulmonary artery 16. What is able to trigger the contraction of cardiac muscle? A Purkinje fibre B Sinoatrial node 35  C Autonomous nerve D Atrioventricular node 17. The factor that does not influence water absorption in plants is A soil aeration B air humidity C air temperature D soil water potential 18. Which statement is true of transpirational pull? A it is an active process B it causes the girth of the tree trunk to expand C it is not affected by the morphology of the leaf D its mechanism depends on the negative pressure generated in the leaf 19. The pressure changes in the left side of the heart during the cardiac cycle are shown in the graph below. How are the states of the atrioventricular and semilunar valves at W, X, Y and Z? Atrioventricular valves Semilunar valves Closed Opened Closed Opened A W X Y Z B W Z Y X C X W Z Y D Z W X Y 20. Which blood vessel is dependent on skeletal muscle contraction to assist blood flow through it? A Vein B Artery C Arteriole D Capillary 21 Which is the correct sequence of a cardiac cycle? 36  A Atrial diastole, atrial systole, ventricular systole, ventricular diastole B Atrial diastole, ventricular systole, atrial systole, ventricular diastole C Atrial diastole, ventricular diastole, atrial systole, ventricular systole D Atrial diastole, ventricular diastole, ventricular systole, atrial systole 22 Which is true of a cardiac cycle? A Atrial systole ventricular systole cardiac systole B Atrial diastole ventricular diastole cardiac systole C Atrial systole ventricular systole cardiac diastole D Atrial diastole ventricular systole cardiac diastole 23 Which is the function of an atrioventricular node? A it acts as a pacemaker B it initiates the atrial systole C it determines the rate of contraction of the cardiac muscle D it delays the impulse from the sino-atrial node to the Purkinje fibre 24 Which are true of the atrioventricular node? I it is located between the two atria II it acts as a primary pacemaker III it speeds up the transmission of impulse IV it transmits impulse to the Purkinje fibres A I and III B I and IV C II and III D II and IV 25 The risk factors which are associated with the development of diseases are given below: I gout II diabetes mellitus III elevated oestrogen level IV elevated cholesterol level Which are the risk factors that are associated with the cardiovascular diseases? A I and III B I and IV C II and III D II and IV 26 Which is not a cardiovascular disease? A Arthritis B Arteriosclerosis C Atherosclerosis D Hypertension 27 Several steps in the impulse transmission of a cardiac cycle are given below. 37  I the impulse travels down the Purkinje fibre II the ventricular contraction begins from the apex upwards III the atrioventricular node receives the impulse transmission IV the impulses from the sinoatrial node are relayed to both atria causing atrial contraction Which sequence of events in impulse transmission of a cardiac cycle is correct? A I,IV,III,II B II,IV,III,I C III,I,II,IV D IV,III,I,II 28 Which are true of myocardial infarction? I arterial wall hardens II known as ‘heart muscle death’ III blood supply to the heart is insufficient IV a condition in which a blood vessel bursts in the brain A I and III B I and IV C II and III D III and IV 29. Which are the physical characteristics and evidence that support the cohesion-tension theory? I Accumulation of ions causes water to move into the xylem from the surrounding root cells, creating a positive pressure that forces the water up the xylem to the shoot. II Xylem vessels in higher plants form a continuous system from the leaves to the roots where evaporation and absorption of water occur respectively. III evaporation of water from leaves increases their water potential and causes water to move by osmosis from xylem to stomata across leave tissues IV gradients in water potential are established along transpiration pathway in the xylem, pulling water columns from the roots to the leaves A I and II B I and III C II and IV D III and IV 30. A cross section of a monocot vascular bundle is shown in the diagram below. Which statement is true of the water potential in the above cells? A it is less negative in G than in E and F B it is less negative in F than in E and G C it is more negative in E than in F and G D it is more negative in F than in G and E 31.The changes in blood pressure during cardiac cycle are shown in the diagram below. 38  In which states are the atrium and semilunar valve at X? Atrium Semilunar valve A Diastole Close B Diastole Open C Systole Close D Systole Open TOPIC : TRANSPORT 5/2002 (a) Huraikan struktur jantung mamalia yang disesuaikan dengan fungsinya sebagai organ pengepam darah. (b) Jelaskan bagaimana denyutan jantung bermula dan bagaimana kadar denyutan dikawalatur. 6/2005 (a) Give the definition, causes and methods of prevention of each of the following cardiovascular diseases. (i) Hypertension (ii) Arteriosclerois (b) With the aid of Munch model, describe the mechanism of mass translocation in phloem. 6/2008 (a) The transportation of water molecules and mineral ions from the soil to the roots could occur via several pathways such as vacuole, apoplast and symplast.Describe these three pathways. (b) Among the mechanisms of the translocation of sugar through sieve tubes are the mass-flow hypothesis, the electro-osmosis and the cytoplasmic streaming.Describe these three mechanisms. 7/2010 With the aid of a labelled diagram, describe the mechanism and control of heart beat. 39 Structured Question 2/2011 The Munch model which explains the mechanism of photosynthetic product translocation in plants is shown in the diagram below. (a) Name the hypothesis which is related to the model. [1 mark] Pressure / Mass flow (b) Match E and F in the model to the organs which exist in a sprouting potato. [2m] E : Potato tuber F : Growing shoot / growing bud / plumule / radicle (c) Describe the process which occurs at the source of a plant undergoing photosynthesis. [4 marks] - Photosynthesis produces sugar / glucose / sucrose / carbohydrate - Which is actively loaded / transported into sieve tube - This makes the water potential in sieve tube lower - Water from xylem enter sieve tube by osmosis - Create high hydrostatic pressure in the sieve tube / phloem - Mass flows occur (d) Why does the translocation of photosynthetic product occur only in phloem but not in xylem? [3 marks] - loading and unloading // translocation is an active transport - phloem is a living tissue // xylem is a dead tissue - energy /ATP can be supplied by companion cell 40