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53 Cards in this Set
- Front
- Back
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what is tissue fluid?
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the environment around the cells of multicellular organisms
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what substances do organisms need to exchange with their environments?
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respiratory gases (oxygen and carbon dioxide) nutrients (glucose, fatty acids amino acids, vitamins, minerals) excretory products (urea) heat |
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how can substances be exchanged in organisms?
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passively - diffusion actively - active transport |
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how have organisms evolved for efficient exchange?
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- flattened shape so that no cell is ever far from the surface (flatworm) - specialised exchange surfaces with large areas to increase the surface area to volume ratio |
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what are the features of specialised exchange surfaces?
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a large surface area relative to the volume of the organism which increases the rate of exchange very thin so that the diffusion distance is short and therefore materials cross the exchange surface rapidly selectively permeable to allow selected materials to cross movement of the environmental medium to maintain diffusion gradient a transport system to ensure the movement of the internal medium, in order to maintain diffusion gradient |
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what is the equation for diffusion?
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diffusion = surface area x difference in concentration / length of diffusion path
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describe gas exchange in insects
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internal network of tubes - tracheae which are supported by strengthened rings to prevent them from collapsing. the tracheae divide into tracheoles which extend throughout all the body tissues of insect (have thin permeable walls) in this way, atmospheric air is brought directly to the respiring tissues, as there is a short diffusion pathway from a tracheoles to any body cell |
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how do respiratory gases move in and out of tracheal system?
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along a diffusion gradient - oxygen travels down a diffusion gradient towards the cell, carbon dioxide from the cell moves down its concentration towards the spiracles to be released rhythmic abdominal movements - the contraction of muscles in insects can squeeze the trachea enabling mass movements of air in and out ends of tracheoles are filled with water - during periods of major activity, the muscle cells around the tracheoles respire and carry out some anaerobic respiration. this produces lactate, which is soluble and lowers the water potential of the muscle cells. water therefore moves into the cells from the tracheoles by osmosis. volume of water in tracheoles decreases meaning more air can be absorbed |
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what are spiracles?
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pores on the surface of insects they may be opened or closed by a valve, when spiracles are open water vapour can evaporate from them. |
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describe the structure of gills
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made up of gill filaments, which have gill lamellae, which increase surface area of the gills lots of blood capillaries and thin surface layer of cells to speed up diffusion the artery carries deoxygenated blood to the gill the vessels carry oxygenated blood from the gill |
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describe counter current exchange in fish
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water enters the fish through its mouth blood and water flow through the lamellae in opposite directions this maintains a large concentration gradient between water and blood across full length of gill lamellae concentration of oxygen in water is always higher than in the blood, so as much oxygen as possible diffuses from the water into the blood |
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describe gas exchange in dicotyledonous plants
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main gas exchange surface is the surface of mesophyll cells in the leaf. they have a large surface area the mesophyll cells are inside the leaf - gases move in and out through special pores in the epidermis called stomata the stomata can open to allow exchange of gases and close if the plant is losing to much water guard cells control the opening and closing of stomata |
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how do insects control water loss?
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insects can close their spiracles using muscles waterproof waxy cuticle tiny hairs around their spiracles (reduce evaporation) |
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how do plants control water loss?
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stomata kept open during day to allow gaseous exchange, water enters the guard cells making them turgid, which opens the stomatal pore. if plant starts to get dehydrated, the guards cells lose water and become flaccid, closing the pore xerophytes - warm dry environments - stomata sunk in pits that trap moist air, reducing concentration gradient of water between the leaf and the air - reduces evaporation layer of hairs on epidermis - trap moist air around stomata curled leaves with stomata inside - protect from wind reduced number of stomata - fewer places for water to escape waxy, waterproof cuticle - reduce evaporation reduced number of stomata to reduce water loss |
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describe inspiration
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external intercostal and diaphragm muscles contracts ribcage moves upwards and outwards and diaphragm flattens, increasing volume of thoracic cavity and decreasing lung pressure air flows down pressure gradient down trachea and into lungs - it is an active process |
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describe expiration
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external intercostal and diaphragm muscles relax ribcage moves downwards and inwards and diaphragm becomes curved again volume of thoracic cavity decreases, causing the air pressure to increase to above atmospheric pressure air is forced down the pressure gradient and out of the lungs - passive process |
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describe forced expiration
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external intercostal muscles relax and internal intercostal muscles contract, pulling the ribcage further down and in. movement of two sets of muscles is antagonistic |
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how does oxygen diffuse into the blood
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oxygen from the air moves down the trachea, bronchi and bronchioles into the alveoli this movement happens down a pressure gradient - once in the alveoli, the oxygen diffuses across the alveolar epithelium, then the capillary endothelium, ending in the capillary itself. this happens down a diffusion gradient |
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how are alveoli adapted for gas exchange?
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thin exchange surface - alveolar epithelium is only one cell thick - short diffusion pathway large surface area - large number of alveoli steep concentration gradient of oxygen and carbon dioxide between the alveoli and the capillaries, increases rate of diffusion - constantly maintained by blood flow and ventilation |
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what Is tidal volume?
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the volume of air in each breath
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what is ventilation rate?
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the number of breaths per minute |
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what is forced expiratory volume?
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the maximum volume of air that can be breathed out in one second
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what is forced vital capacity?
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the maximum volume of air it is possible to breathe forcefully out of the lungs after a really deep breath in
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what can you use to measure the tidal volume, ventilation rate
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spirometer
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what is the equation for pulmonary ventilaltion
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pulmonary ventilation = tidal volume x ventilation rate
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name 4 diseases that affect the lungs
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pulmonary tuberculosis (TB) fibrosis asthma emphysema |
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what is pulmonary tuberculosis ? |
when someone becomes infected with tuberculosis bacteria, immune system cells build a wall around the bacteria in the lungs. this forms small hard lumps known as tubercles infected tissues within the tubercles dies and the gaseous exchange surface is damaged, so tidal volume is decreased - causes fibrosis - a reduced tidal volume means less air can be inhaled with each breath - ventilation rate is increased |
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what is fibrosis?
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the formation of scar tissue in the lungs - the result of an infection or exposure to substances like asbestos or dust scar tissue is thicker and less elastic than normal lung tissue lungs are less able to expand and so cant hold as much air as normal - tidal volume is reduced and so is FVC - theres a reduction in the rate of gaseous exchange - diffusion is slower across a thicker scarred membrane - symptoms include shortness of breath, a dry cough, chest pain, fatigue and weakness fibrosis sufferers have a fast ventilation rate |
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what Is asthma?
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a respiratory condition where the airways become inflamed and irritated, usually because of an allergic reaction to substances such as pollen and dust during an asthma attack the smooth muscle lining in the bronchioles contracts and a large amount of mucus is produced this causes constriction of the airways, making it difficult for the sufferer to breathe properly. air flow in and out of the lungs is severely reduced, so less oxygen enters the alveoli and moves into the blood FEV is severely reduced symptoms include wheezing, a tight chest and shortness of breath symptoms can be relieved by drugs which cause muscle in bronchioles to relax |
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`what is emphysema?
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a lung disease caused by smoking or long term exposure to air pollution - foreign particles in smoke become trapped in alveoli - this causes inflammation, which attracts phagocytes to the area. the phagocytes produce an enzyme that breaks down elastin elastin is elastics - it helps alveoli return to their normal shape after inhaling and exhaling air. loss of elastin means alveoli cant recoil to expel air as well leads to destruction of alveoli walls, which reduces surface area so rate of gaseous exchange decreases symptoms include shortness of breath and wheezing have increased ventilation rates |
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what are carbohydrates broken down into?
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disaccharides and then monosaccharides they are broken down by amylase and membrane-bound disaccharidases |
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what are fats broken down into?
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monoglycerides and fatty acids
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what are proteins broken down into?
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amino acids
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what does amylase do?
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catalyses the conversion of starch (polysaccharide) into maltose (disaccharide) involves hydrolysis of glycosidic bonds it is produced in the salivary glands (released into mouth) and pancreas (released into small intestine) |
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what are membrane bound disaccharidases?
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enzymes that are attached to the cell membranes of epithelial cells lining the ileum they help to break down disaccharides (maltose sucrose lactose) into monosaccharides |
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give examples of three disaccharidases?
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maltase sucrase lactase |
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how are lipids broken down
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by lipase (made in pancreas work in small intestine) - lipase catalyses the breakdown of lipids into monoglycerides and fatty acids. this involves hydrolysis of ester bonds bile salts are produced in the liver and emulsify lipids - this means they cause the lipids to form small droplets, increases surface area. monoglycerides and fatty acids stick with the bile salts to form tiny structures called micelles |
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how are proteins broken down?
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proteases or peptidases. - enzymes that catalyse the conversion of proteins into amino acids by hydrolysing the peptide bonds between amino acids - endopeptidases - hydrolyse bonds within protein (trypsin and chymotrypsin) synthesised in pancreas and secreted into small intestine (pepsin - released into stomach by cells in stomach lining) - exopeptidases - hydrolyse peptide bonds at the ends of protein molecules - remove single amino acids dipeptidases - work specifically on dipeptides - located in cell surface membrane of epithelial cells in small intestine |
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how are monosaccharides absorbed?
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glucose is absorbed by active transport with sodium ions via co-transporter protein and so Is galactose fructose is absorbed via facilitated diffusion |
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how are monoglycerides and fatty acids absorbed?
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micceles help to move them towards epithelium the release monoglycerides and fatty acids, allowing them to be absorbed - as they are lipid - soluble |
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how are amino acids absorbed?
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sodium ions are actively transported out of the epithelial cells into the ileum - they then diffuse back into the cells through sodium-dependent transporter proteins in the epithelial cell membranes
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describe the structure of haemoglobin
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a large protein with a quaternary structure - made up of four polypeptide chains each chain has a haem group which contains an iron ion |
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describe haemoglobin
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Has a high affinity for oxygen - each molecule can carry four oxygen molecules in the lungs oxygen joins to haemoglobin in red blood cells to form oxyhaemoglobin this is a reversible reaction |
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what is the partial pressure of oxygen>?
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a measure of oxygen concentration the greater the concentration of dissolved oxygen in cells, the higher the partial pressure |
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how does haemoglobins affinity for oxygen depend on partial pressure of oxygen
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oxygen loads onto haemoglobin to form oxyhaemoglobin where theres a high partial pressure of oxygen oxyhaemoglobin unloads its oxygen when theres a low partial pressure of oxygen |
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what is the bohr effect?
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when cells respire they produce carbon dioxide which raises partial pressure of carbon dioxide this increases the rate of oxygen unloading so dissociation curve shifts to the right the saturation of blood with oxygen is lower for a given partial pressure of oxygen meaning more oxygen is being released |
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describe the circulatory system
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made up of the heart and blood vessels the heart pumps blood through blood vessels to reach different parts of the body blood transports respiratory gases, products of digestion, metabolic wastes and hormones round the body - two circuits one takes blood from the heart to the lungs, then back to the heart, the other takes blood around the rest of the body |
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name three blood vessels
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arteries arterioles veins |
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describe arteries |
carry blood from the heart to the rest of the body have thick and muscular walls and elastic tissue to stretch and recoil as the heart beats, which helps maintain the high pressure all arteries carry oxygenated blood except for the pulmonary arteries, which take deoxygenated blood to the lungs divide into arterioles - form a network throughout body. blood is directed to different areas of demand in the body by muscles inside the arterioles, which contract to restrict the blood flow or relax to allow full blood flow |
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describe veins
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take blood back to the heart at low pressure. have a wider lumen than equivalent arteries, with very little elastic or muscle tissue contain valves to stop the blood flowing backwards - blood flow is helped by contraction of the body muscles surrounding them all veins carry deoxygenated blood except for the pulmonary veins which carry oxygenated blood to the heart from the lungs |
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how are capillaries adapted for efficient diffusion?
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always found very near cells in exchange tissues, so there's a short diffusion pathway walls are only one cell thick large number of capillaries to increase surface area for exchange capillary beds are networks of capillaries in tissues |
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how does high blood pressure lead to the accumulation of tissue fluids?
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high blood pressure = high hydrostatic pressure this increases outward pressure from arterial end of capillary and reduces inward pressure at venule end of capillary so more tissue fluid is formed |
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how is tissue fluid formed from blood?
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at the start of the capillary bed, nearest the arteries, the hydrostatic pressure is greater than that in the tissue fluid there is an overall outward pressure that forces fluid out of capillaries and into open spaces around cells, forming tissue fluid any excess tissue fluid is drained into lymphatic system which transports this excess tissue fluid from the tissues and dumps it back into the circulatory system
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