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 non-oxygenated 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

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

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

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

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