transport in plants
Plants have a transport system made up of xylem and phloem vessels.
1) State the functions of Xylem and Phloem
- Xylem vessels transport water and minerals from the roots to the leaves via transpiration.
- The xylem is made up of dead cells.
- Phloem tubes transport sugar and other organic nutrients made by plant from the leaves to the rest of the plant via translocation.
- The phloem is made up of living cells.
2) Identify the position of Xylem in sections of Roots, Stems and Leaves
3) Explain how Root Hair Cells are adapted for their function.
- The root hairs are long and thin so they can penetrate between soil particles.
- Water passes from the soil water to the root hair cell’s cytoplasm by osmosis. This happens because the soil water has a higher water potential than the root hair cell cytoplasm:
- The elongated section of the root hair, basically provides a large surface area for the absorption of water and inorganic ions by active transport.
- They also have thin wall so the diffusion distance is shortened.
- The membrane of the root hair cell is semi-permeable. What that means is basically only minerals and water can go through the membrane, but not necessarily go back out.
4) State the Pathway taken by Water through Root
- Water enters root hair cell from moist soil via osmosis.
- Water passes through the cortex cells by osmosis as they have higher water potential than the cortex cells.
- Water and minerals are forced to cross the endodermis. Water enters xylem vessels where it is drawn up the stem to the leaves.
- At the leaf, it diffuses into mesophyll cells where it is used for metabolic reactions such as photosynthesis.
* 5) Investigate, using a stain, the pathway of water
- Cut the base, non-leafy end, of a fresh stalk of celery underwater.
- Place the cut end into a beaker of water stained with red food dye.
- Leave the celery stalk in bright light at room temperature.
- Note the red lines moving up the stalk and then along the veins of the leafy parts.
- Cut across the stalk and note the curve of red dots close to the outer edge.
- If a thin section is examined under the microscope it is the xylem which has been stained red in colour.
6) Explain the mechanism by which Water moves upwards in the Xylem
- Transpiration is the loss of water vapour from the mesophyll cells surface due to evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata.
- The water vapour exits the plant via the stomata.
- Water molecules are drawn up the xylem by transpiration pull.
- Water molecules are cohesive. This means that as the water evaporates at the leaf and diffuses out of the stomata, more water is drawn up the plant from the roots.
7) Explain the effects of Variation of Temperature and Humidity on transpiration rate
- Temperature: On warm days the temperature is higher, so water evaporates more easily, therefore there is more diffusion of water vapour out of the plant, so the rate of transpiration is high.
- Humidity: A high humidity decreases the rate of transpiration as the concentration gradient of water vapour between the inside and outside of the plant is comparatively low, so diffusion out of the plant is slower.
8) Explain how and why Wilting occurs
- Occurs when the transpiration rate is faster than the rate of water absorption.
- The amount of water in the plant keeps on decreasing.
- The water content of cells decreases and cells turn from turgid to flaccid.
- The leaves shrink and the plant will eventually die.
9) Describe Translocation
- Movement of sucrose and amino acids in the phloem; from regions of production (sources) to regions of storage or regions where they are used in respiration or growth (called sink).
- Materials are always transported from source to sink.
- Some parts of a plant can act as a source and a sink at different times during the life of a plant, eg. while a bud containing new leaves is forming it would require nutrients and therefore act as a sink. However, once the bud has burst and the leaves are photosynthesising, the region would act as a source, sending newly synthesised sugars and amino acids to other parts of the plant.
transport in mammals
10) Describe the Circulatory System in mammals
- Made up of blood vessels (veins, capillaries, arteries) with a pump (heart) and valves (in heart and veins) to ensure one-way flow of blood.
* 11) Describe the single circulation of a fish
- Fish have a single circulatory system. The blood goes through the heart once only for each complete circulation of the body.
- The heart only has two chambers, one atrium (collecting chamber) and one ventricle (ejection chamber).
- It sends blood to the gills. Oxygen is absorbed as it passes the gills. The blood then flows to all the parts of the body before returning to the heart.
- This system is inefficient because blood pressure is lost when the blood passes through capillaries in the gills.
12) Describe the Double Circulation System in mammal
- The blood passes through heart twice.
- Oxygenated blood flows from heart to lungs, flows back to heart, from heart to rest of body, and back to heart.
13) Explain the Advantages
- More efficient at supplying oxygen for use eg. respiration.
- Can maintain a high blood pressure.
- Oxygenated and deoxygenated blood are kept separate.
14) Identify the Structures of the Mammalian Heart
- Right atrium: collect deoxygenated blood & pump it to right ventricle
- Right ventricle: pumps deoxygenated blood to lungs
- Pulmonary artery: carries deoxygenated blood from right ventricle to lungs
- Septum: separates left and right sides of the heart, separates oxygenated and deoxygenated blood.
- Pulmonary vein: carry oxygenated blood from lungs to left atrium.
- Left atrium: collect oxygenated blood and pump it to left ventricle
- Left ventricle: have thicker walls than right ventricle because need to pump oxygenated blood to rest of body via the aorta.
- Aorta: carries oxygenated blood from left ventricle to rest of body
- Tricuspid and bicuspid valves: prevent backflow of blood into the atria when ventricles contract (Atria Ventricular valves)
- Pulmonary and aortic valves: prevent backflow of blood from the arteries into the ventricles (semi-lunar valves)
15) Describe the Functioning of the Heart
16) Name the main Blood Vessels
- To and from the heart: vena cava, aorta, pulmonary artery and pulmonary vein.
- To and from the lungs: pulmonary artery and pulmonary vein.
- To and from the kidney: renal artery and renal vein.
* 17) To monitor the activity of the heart
- ECG (electrocardiogram)
- Pulse rate
- Heart sound using a stethoscope, ‘lub-dub’ sound caused by the closure of the valves
* 18) Investigate effect of physical activity on the pulse rate
- At rest, the heart beats about 70 times a minute, but varies according to age, gender and fitness.
- An increase in physical activity increases the pulse rate, up to 200 beats per minute.
- After exercise has stopped, the pulse rate gradually drops to its resting state, the rate depends on the fitness of the person.
- During exercise, the muscle cells need more energy than usual, and need to respire more. So it need more oxygen and glucose, and produce more waste, carbon dioxide.
- If the muscle does not get enough oxygen, it will start to respire anaerobically, producing lactic acid, which cause muscle fatigue, leading to cramp.
19) Describe Coronary Heart Disease
- Coronary heart disease is caused by a buildup of cholesterol in the coronary artery which narrows the artery thus limiting blood flow to the heart.
- The heart muscle cells are deprived of oxygen & glucose, and poisonous wastes such as lactic acid build up.
- Part of the heart muscle stops contracting, causing a heart attack.
- Stress, smoking, too much saturated fat in diet, poor lifestyle & genetics.
- Not smoking, avoiding fatty food and exercising regularly.
- Aspirin thins the blood and make platelets less likely to clump together to block the artery. Surgery (stents, angioplasty and by-pass).
- Angioplasty and stent. Angioplasty involves the insertion of a long, thin tube called a catheter into the blocked blood vessel. A wire attached to a deflated balloon is then fed through the catheter to the damaged artery. The balloon is then inflated to widen the artery wall, freeing the blockage. Stent can be used. This is a wire-mesh tube that can be expanded and left in place.
- By-pass surgery. The surgeon removes a section of blood vessel from a different part of the body, such as the leg. The blood vessel is then attached around the blocked region of artery to by-pass it, allowing blood to pass freely.
blood and lymphatic vessels
20) Describe the structure and functions of Arteries, Veins and Capillaries
Adaptations for Function
Transport high pressure blood away from heart
Transport low pressure blood to the heart
Allow exchange of substances (eg. oxygen, carbon dioxide and nutrients) with tissues.
* 21) State the function of Arterioles, Venules and Shunt Vessels
- At the tissues, arteries branch into arterioles, which enter the tissues and become capillaries.
- The narrow vessels that connect capillaries to veins are called venules.
- When the muscle fibres of the arterioles contract, they make the vessels narrower and restrict the blood flow (process called vasoconstriction). In this way, the distribution of blood to different parts of the body can be regulated.
- Shunt vessels, linking the arterioles with venules, dilate to allow the blood to bypass the capillaries, and constricts in cold conditions to limit blood flow to reduce heat loss.
* 22) Name the Main Blood Vessels
- Pulmonary Veins: This transports oxygenated blood from the lungs to the left atrium
- Aorta: This transports oxygenated blood from the heart to the rest of the body and the brain.
- Vena Cava: This transports deoxygenated blood from the rest of the body to the heart.
- Pulmonary Artery: Transports deoxygenated blood from body to the heart to the lungs.
- Hepatic Artery: This supplies oxygenated blood to the liver (also pylorus (part of stomach), duodenum and pancreas).
- Hepatic Portal Vein: This transports blood from the gastrointestinal tract and spleen to the liver, rich in nutrients to be processed by the liver.
- Renal Artery: This supplies kidney with oxygenated blood.
- Renal Vein: This transports blood away from the kidney, into the inferior Vena Cava.
* 23) Describe the function of the Lymphatic System
- The lymphatic system is made up of lymph vessels and lymph nodes.
- Capillaries exchange substances with cells by producing tissue fluid. This forms at the arteriole end of the capillary when nutrients are forced out of capillaries due to the high pressure in the narrower blood vessel. Tissue fluid bathes the cells and allows nutrients to diffuse into cells, and waste substances to diffuse out into the tissue fluid. Most of the tissue fluid is reabsorbed into the capillary at the venous end.
- Some larger molecules, such as lipids and large proteins, cannot re-enter the capillary, thus must be carried away by the lymph system. These molecules enter the lymph vessels and travel as a fluid called lymph. Lymph passes through lymph vessels and drains into the blood system in the chest cavity.
- Lymph nodes are present along the lymph vessels, predominantly located in the neck, armpits and groin. Lymphocytes are stored in the lymph nodes and released into the lymph to eventually reach the blood system.
- There are also phagocytes in the lymph nodes. If bacteria enter a wound and are not ingested by the white cells of the blood or lymph, they will be carried in the lymph to a lymph node and white cells there will ingest them.
- The lymph nodes thus form part of the body’s defence system against infection.
24) State the Functions of the Components of Blood
- Red blood cells: contains haemoglobin, for oxygen transport.
- White blood cells: play a major role in fighting off infection. A lymphocyte is a type of white blood cell which produces antibodies that binds with a specific antigen (proteins found on the cell membrane of pathogens), causing the foreign cells to clump together, making them harmless as they can no longer enter cells to cause damage. Phagocyte is another type of white blood cell which carry out phagocytosis.
- Platelets: involved in blood clotting.
- Plasma: the liquid in blood that transport of blood cells, ions, soluble nutrients, hormones, carbon dioxide, urea and plasma proteins.
- Phagocyte recognizes and attaches to foreign pathogen.
- The membrane of the phagocyte envelops the pathogen and folds inwards, trapping it inside the phagocyte.
- The phagocyte releases enzymes which break down the pathogen, killing it.
- Blood clotting occurs when a blood vessel breaks due to an injury.
- Platelets stick to the broken vessel wall and clump together, blocking the cut.
- Fibrinogen is then converted to a protein called fibrin, which forms a mesh of fibrin fibers across the wound. More platelets stick to this mesh. This forms a scab and prevents bleeding by blocking the cut.
- This prevents blood loss and allows the vessel to heal, as well as preventing pathogens from entering the blood vessel.
* 25) Describe the transfer of materials between capillaries and tissue fluid
- The fluid that escapes from capillaries is not blood, nor plasma, but tissue fluid.
- Tissue fluid is similar to plasma but contains less protein, because protein molecules are too large to pass through the walls of the capillaries.
- This fluid bathes all the living cells of the body and, since it contains dissolved food and oxygen from the blood, it supplies the cells with their needs.
- Some of the tissue fluid eventually seeps back into the capillaries, having given up its oxygen and dissolved food to the cells, but it has not received the waste products of the cells, such as carbon dioxide, which are carried away by the bloodstream.
- The tissue fluid that doesn’t return to the capillaries joins the lymphatic system.