Transcript Slide 1
• What features does a good exchange surface have? 4 • • • • Large sa Thin barrier Fresh supply of molecules Removal of molecules • How are the lungs adapted for gas exchange? 5 • Large sa • Permeable plasma membrane of cells in alveoli • Thin barrier- alveoli wall one cell thick • Thin capillary wall • Diffusion gradient maintained by breathing and blood movement to and from lungs • How is a diffusion gradient maintained in the lungs? 2 • Breathing replenishes oxygen concentration in alveoli • Heart pumps blood away from lungs lowering oxygen content in capillaries Describe the role of cartilage, smooth muscle, elastic fibres, goblet cells and ciliated epithelium 5 • Cartilage: structural, prevents collapse with pressure changes • Smooth muscle: contracts to make lumen narrower • Elastic fibres: elastic recoil after smooth muscle has contracted • Goblet cells: secrete mucus • Ciliated epithelium: move in synchronised pattern to waft mucus up airway Explain how size, surface area to volume ratio and level of activity affect the need for a transport system 3 • Size: bigger = more need for exchange surface • Sa: smaller = more need for exchange surface • Level of activity: more = more need for exchange surface • Explain the differences between single and double circulatory systems 3 • Single = blood goes through heart once with each circuit of the body • Double = systemic and pulmonary circulation. • Blood visits heart twice with each circuit through the body • Describe the advantages of a double circulatory system 2 • Increased pressure, so blood flows faster • Systemic circulation can carry blood at higher pressure than pulmonary circulation • Explain the role of the valves and the septum 2 • Valves prevent backflow • Septum prevents oxygenated and nonoxygenated blood from mixing Outline the stages in the cardiac cycle 3 • Filling phase: diastole, all parts are relaxed, atrioventricular valves are open • Atrial systole: atria contract pushing blood into ventricles, semi lunar valves are closed • Ventricular systole: ventricles contract, atrioventricular valves close, semi-lunar valves open • Describe how valves work 3 • Pressure in ventricles drops below atria • Atrioventricular valves open • Ventricle fills with blood and increase in blood pressure fills the valve pockets and closes atrioventricular valves • Explain how heart action is co-ordinated 5 • SAN generates electrical activity • Spreads over atrial walls causing contraction • AVN delays the signal • Passes it down purkyne tissue • Up from the base of the heart causing ventricles to contract 1. Explain the differences between open and closed circulatory systems 2 • Open: blood is not contained in vessels, in insects it enters heart through ostia and blood is pumped by peristalsis • Closed: blood is contained in vessels • Describe the structure of arteries, veins and capillaries 3 • Arteries: small lumen, thick wall, elastic fibres, smooth muscle, contains collagen • Veins: large lumen, inner layers of collagen, smooth muscle, elastic tissue, no stretch or recoil, valves • Capillaries: thin walls, single layer of cells, narrow lumen • Outline the role of blood, tissue fluid and lymph 3 • Blood: transport oxygen, hormones and carbon dioxide • Tissue fluid: plasma with dissolved nutrients and oxygen, speeds up diffusion • Lymph: contains lymphocytes and filter bacteria and foreign materials for destruction • Explain how tissue fluid and lymph are formed 2 • Tissue fluid: high hydrostatic pressure pushes blood fluid out of the capillaries through tiny gaps • Lymph: some tissue fluid is drained into lymphatic vessels • Describe the role of haemoglobin in carrying oxygen 4 • • • • 4 subunits Haem contains one iron atom Haem has affinity for oxygen Oxyhaemoglobin releases oxygen= dissociation 1. Explain the oxygen dissociation curve and explain why the curve for fetal haemoglobin is different 2 • Oxygen dissociation: S shaped curve, as oxygen tension rises, more haemoglobin is saturated, then curve levels off • Fetal haemoglobin has a higher affinity so that it can absorb oxygen from mothers blood • How are hydrogencarbonate ions formed? 3 • CO2 combines with water to make carbonic acid • Carbonic acid dissociates to release hydrogen ions and hydrogencarbonate ions • They diffuse out of the red blood cells into the plasma • What is the chloride shift? 1 • Chloride ions (negative) move from plasma into the red blood cells, to maintain the charge as negative hydrogencarbonate ions have left • Outline the Bohr effect 3 • Hydrogen ions released from dissociation of carbonic acid • Hydrogen ions displace the oxygen in haemoglobin • Oxyhaemoglobin releases more oxygen to tissues 1. Describe the distribution of xylem and phloem in the root, stem and leaf 3 • Root: x shaped xylem • Stem: xylem and phloem in circles near outside of stem • Leaf: xylem above phloem • Outline the structure of xylem and phloem • Xylem: continuous column, dead cells, lignified, pits • Phloem: sieve tube elements, companion cells, perforated sieve tubes 1. Describe the meaning of water potential and how it affects a plant cell • Water potential is the movement of water down a concentration gradient: affected by pressure and solutes • Plasmolysed, turgid, flaccid • Outline how water can move between cells • Apoplast: between cell walls • Symplast: through plasma membrane • Vacuolar: through cytoplasm and vacuole • Explain how water moves up the stem • Cohesion-tension theory • Transpiration pull and capillary action • Outline the factors that affect the rate of transpiration (8) • • • • • • • • Number of leaves Number of stomata Cuticle, Light Temp Humidity Air movement Water availability • How do plants cope in arid conditions (how are they adapted?) • • • • • Rolled leaf Thick cuticle Trapped air inside rolled leaf Hairs on lower surface Stomata in pits • Explain how sugars are transported along the phloem tissue 2 • Translocation • from source to sink • Explain the meaning of sources and sinks with examples of each • Source: loads sucrose • Sink: uses/stores sucrose • Leaf/root