Module 3

  1. Features of an effective exchange surface
    • Large Surface Area
    • Thin Layers
    • Good Blood Supply/Ventilation
  2. The Structure of the Lungs:
    List the different parts of the airways leading into the lungs
    • Trachea
    • Bronchi
    • Bronchioles
    • Alveoli
  3. How is the Trachea structured and why?
    • Incomplete rings of cartilage offer support, are flexible and allow food to pass in the oesophagus
    • Lined with ciliated epithelium goblet cells that secrete mucus
  4. How are the Bronchi structured? (Bronchus singular)
    • Divisions of the trachea
    • Same structure as trachea
  5. How are the Bronchioles structured and why?
    • Smaller bronchioles have no cartilage 
    • Walls contain smooth muscle to contract & constrict or relax and dilate
    • Lined with thin layer of flattened epithelium - some gaseous exchange occurs
  6. How are the Alveoli structured and why?
    • Tiny air sacs (200-300μm)
    • Thin layer of squamous epithelial cells - gaseous exchange
    • Collagen
    • Elastic fibres - expand/return to normal size - elastic recoil
    • Lung Surfactant - keeps alveoli from sticking shut
    • Moist - solution of water, salts and surfactant allow oxygen to dissolve before diffusing to blood
  7. What happens when we Inhale?
    • 1. Intercostal muscles contract
    • 2. Diaphragm contracts
    • 3. Chest cavity expands - low pressure, high lung volume
    • 4. Air forced into lungs
  8. What happens when we Exhale?
    • 1. Intercostal muscles relax, ribs move down & inwards under gravity
    • 2. Diaphragm relaxes, moving upward to domed shape
    • 3. Elastic Fibres return to normal length
    • 4. Volume of thorax decreases, pressure increases above atmospheric pressure
    • 5. Air is pushed out
  9. What do each of the arrows show from this Spirometer Trace?
    Image Upload 1
    • 1. Inspiratory Reserve Volume
    • 2. Tidal Volume
    • 3. Expiratory Reserve Volume
    • 4. Residual Volume
    • 5. Total Lung Capacity
    • 6. Vital Capacity
    • (7. Functional Residual Capacity)
  10. What is Inspiration Capacity and how do you show it on a spirometer trace?
    • From the bottom of tidal volume to the top of total lung capacity
    • The total amount of air you can breath in after breathing out normally
  11. What is Vital Capacity?
    The volume that is inhaled with the strongest possible exhalation followed by the strongest possible inhalation
  12. Equation linking ventialation rate, tidal volume and breathing rate?
    Ventilation Rate = Tidal Volume × Breathing Rate
  13. Gas Exchange in bony fish: 
    What adaptations do they have?
    • Thin gills
    • High SA
    • Tips of gills overlap, slowing flow of water to maximise Ointake
    • Countercurrent system ~ blood and water flow in opposite directions to maintain conc gradient
    • Lamellae have rich blood supply
  14. Gas Exchange in bony fish: 
    How do fish go about gaseous exchange - what is the process?
    • 1. Mouth and buccal cavity open
    • 2. Volume of BC increases, pressure decreases ⇨ water is drawn in
    • 3. Same time, opercular valve shuts & opercular cavity (containing gills) expands
    • 4. Pressure in OC drops
    • 5. BC floor moves up steadily ⇨ increases pressure ⇨ water moves towards the gills
    • 6. Mouth closes, OV opens, OC sides move inwards
    • 7. Increase in pressure ⇨ water moves over gills & out the operculum 
  15. Gas Exchange in Insects: How do insects take in air?
    • Spiracles found along thorax and abdomen
    • Opened or closed as required by sphincters
    • Air moves in through diffusion 
  16. Gas Exchange in Insects: What comes after the spiracles?
    • Tracheae Lined with spirals of chitin to keep them open (up to 1mm wide)
    • Tracheoles divisions of tracheae, single elongated cell, freely permeable to gases
    • Trachael fluid limits penetration of air for diffusion
    • Muscle
  17. Gas Exchange in Insects: What happens when oxygen demands are high?
    • More spiracles opened
    • Lactic acid build up in tissues causes water to move out by osmosis, exposing more SA for gas exchange

    • Large insects/high energy demand:
    • Mechanical Ventilation - air pumped in my muscular movements
    • Collapsible enlarged tracheae or air sacs
  18. How do insects limit water loss?
    • Only open spiracles when needed
    • Hairs around spiracles trap humid air keeping a shallow concentration gradient
  19. What type of circulatory systems do mammals, fish and insects have? What pressure are they? What is the transport medium?
    • Mammals: Double closed, high pressure, blood
    • Fish: Closed, medium pressure, blood
    • Insects: Open, low pressure, haemolymph
  20. What are the pros of a closed circulatory system vs an open circulatory system?
    • Closed:
    • -can carry varying amounts of blood to different parts of body
    • -faster blood flow with double closed having the fastest

    • Open:
    • -unable to maintain steep concentration gradients
    • -can't alter flow to meet different demands
    • -haemolymph doesn't carry O2 or CO
    • -(does carry food & nitrogenous waste)
  21. What is the structure of arteries?
    • Smaller lumen to maintain high pressure of the blood
    • Smooth endothelium to reduce friction
    • Thick layer of Elastic fibres - withstand force of the blood allowing the vessel to stretch & recoil evening out the surges to gain a continuous flow
    • Thin muscle layer - doesnt need to change lumen size much
    • Thick collagen layer maintains volume of vessel & gives structural support
  22. What is the structure of smaller arteries and arterioles? (as they get further fro the heart)
    • The further from the heart, the less elastic fibres
    • The amount of smooth muscle increases to control the size of the lumen & blood flow
    • Collagen decreases since there is less pressure and need for support
  23. What is the structure of capillaries?
    • 10μm - red blood cells travel in single file
    • Gaps between endothelial cells are relatively large to allow substances out of the capillary into the tissue fluid
    • One cell thick - efficient diffusion
    • Total cross-sectional area of capillaries > than supplying arteriole so rate of blood flow drops - more time for exchange
  24. How are veins structured?
    • Larger Lumen - same flow rate as blood has slowed & reduces resistance 
    • Smooth endothelium
    • Thin elastic layer
    • Some Smooth Muscle
    • Lots of Collagen 
    • Valves to prevent back-flow of blood
    • Run between muscles, which squeeze the blood when they contract
    • Breathing movement of chest acts as a pump
  25. What is the blood composed of?
    • 55% Plasma
    • Red & white blood cells & platelets ~ erythrocytes and leucocytes
    • dissolved glucose
    • amino acids
    • mineral ions
    • hormones
    • large plasma proteins e.g fibrinogen
  26. What is hydrostatic pressure and oncotic pressure?
    • Hydrostatic: pressure from surges of blood every time the heart pumps
    • ~ +4.6kPa (arteriole end) ⇨ +2.3kPa (venule end)
    • Oncotic: the tendancy of water to move into the blood in capillaries by osmosis 
    • ~ around -3.3kPa
  27. What is tissue fluid?
    • When hydrostatic pressure is greater than oncotic pressure:
    • -water & other dissolved substances move out of capillaries through fenestrations

    • When hydrostatic pressure is less than oncotic pressure:
    • -about 90% tissure fluid moves back into blood

    • Albumin has osmotic effect
    • -causes low water potential in blood
    • -meaning the osmotic pressure is higher
  28. What is lymph?
    • Last 10% of tissue fluid drains into lymph capillaries
    • -less O2 & nutrients
    • Moved by body movements
    • Valves prevent backflow
    • Returns to blood (subclavian veins)

    • Lymph nodes
    • -lymphocytes build up here & produce antibodies when necessary
    • -intercept bacteria ⇨ injested by phagocytes
  29. How is oxygen transported in the blood?
    • Reversibly binds to haemoglobin 
    • When the first O2 binds, haemoglobin changes shape making it easier for the next to bind
    • Up to 4 oxygen molecules can bind
  30. What is the Bohr Effect?
    At higher partial pressures of CO2 haemoglobin gives up O2 more easily
  31. How is Carbon Dioxide transported in the blood?
    • 5% dissolved in plasma
    • 10-20% combined with amino groups in haemoglobin to form carbaminohaemoglobin
    • 75-85% converted to hydrogen carbonate ions (HCO3-) in cytoplasm of RBCs
    • ~ CO2 + H2O ⇌ H2CO3 (carbonic acid) ⇌ H+ + HCO3-(hydrogen carbonate ion)
    • ~ catalysed by carbonic anhydrase
  32. What is Chloride shift?
    • HCO3- ions diffuse out of RBC
    • Cl- ions diffuse in ~ maintaining electrical gradient
    • ~converting & removing CO2 from RBCs means there is a steep concentration gradient so that more CO2 is collected from respiring tissues

    • In lungs with low partial pressure of CO2:
    • -opposite diffusion directions
    • -carbonic anhydrase converts carbonic acid back to carbon dioxide and water
    • -CO2 free to leave & exit lungs
  33. How does haemoglobin act as a buffer in the blood?
    • Accepts H+ ions from dissociated carbonic acid
    • Forms haemoglobinic acid
  34. What are the two main stages in the cardiac cycle? What is the pressure like in the heart and arteries during these stages?
    • Diastole: ~ filling
    • -volume & pressure build in heart
    • -pressure in arteries at minimum

    • Systole: ~ contracting
    • -atrial systole followed by ventricular systole
    • -high pressure inside heart during contraction
    • -volume & pressure low at end
    • -pressure in arteries at highest
  35. Where does the term 'lub-dub' come from?
    • As the blood hits AV valves during ventricular systole 
    • And hits semi-lunar valves after ventricular systole
  36. What word can be used to describe the rhythm of the heart?
    • Myogenic 
    • - has its own intrinsic rhythm (around 60bbp)
  37. How is the beating of the heart controlled?
    • Wave of excitation begins at Sino-atrial node (SAN)
    • Causes atria to contract
    • Layer of non-conducting tissue prevents impulse passing directly to ventricles
    • Impulse picked up by Atrio-venticular (AV) node 
    • Slight delay (to ensure atria finish contracting) before stimulating Bundle of His ~ made up of conductive Purkyne fibres in septum
    • Bundle of His splits in two
    • Carries impulse down to apex of heart
    • Purkyne fibres spread up sides of ventricles
    • Impulse causes upward contraction of ventricles
  38. Describe what a normal ECG (electrocardiogram) should look like and how they are taken.
    • Measures tiny electrical differences in the skin which result from the heart's activity
    • Image Upload 2
    • Each lasts about 1 second
    • Image Upload 3
  39. List 4 heart conditions and how they effect hear beat
    • Bradycardia 
    • - reduced rate
    • - fit people have more efficient hearts
    • - may require pacemaker 

    • Tachycardia 
    • - very rapid
    • - normal after exercise/fear etc.
    • - can be caused by electrical control problems

    • Ectopic Heartbeat 
    • -out of normal rhythm 
    • - normal around once a day
    • - could be serious if frequent

    • Atrial Fibrillation 
    • - rapid impulses generated at atria which contract quickly
    • - don't contract properly
    • - only some impulses passed on to ventricles
    • - heart does not pump blood very effectively
  40. Describe the structure & function of the Xylem.
    • Carries water and mineral ions
    • Gives plant support
    • Largely non-living
    • Columns of cells fuse end to end
    • Xylem parenchyma packs around vessels to store food and tannin deposits
    • Lignin ~ rings/spirals for support
    • Bordered pits ~ unlignified areas so water can leave
  41. Describe the structure and function of the Phloem
    • Transports food - solutes - sugars, amino acids
    • Living tissue
    • Sieve Tube Elements: 
    • -cells joined end to end
    • -sieve plates between
    • -vacuole membrane (tonoplast), nucleus, some organelles break down
    • Companion Cells:
    • -Linked to sieve tube elements by plasmodesmata
    • -'life support'
  42. What are the two pathways that water can move through a plant's roots and how do they work?
    • Symplast:
    • -cytoplasm connected by plasmodesmata
    • -water moves by osmosis from root hair cell to next cell along as the root hair has a higher water potential
    • -water exits into xylem causing drop in water potential & maintaining gradient

    • Apoplast:
    • -cell walls and intercellular spaces
    • -pulled through by cohesion
  43. How does water and mineral ions move into the xylem?
    • Water reaches endodermis & Casparian strip forces water into symplast pathway ~ passing through selectively permeable membrane blocking out potentially toxic solutes
    • Mineral Ions actively pumped into xylem ~ lowering its water potential
    • Water moves through symplast into xylem cells
  44. What is root pressure?
    • Results from active pumping of mineral ions into xylem
    • ⇨ So water follows due to decreased water potential in xylem
    • Gives water a small push up the xylem
  45. What evidence is there for active transport in root pressure?
    • Cyanide affects mitochondria & stops ATP production
    • ⇨ no root pressure when cyanide is applied

    • Increases with temperature
    • ⇨suggesting chemical reactions are involved

    • Decreases with falling oxygen and respiratory substrate levels
    • ⇨ not a passive process

    • Xylem sap forced out of pores in leaves
    • ⇨ when transpiration levels are low (e.g. at night) there must be something else pushing water up
  46. What is transpiration and how/why does the transpiration stream occur? How does this give rise to the cohesion-tension theory?
    "The loss of water vapour from the leaves and stems as a result of evaporation from cell surfaces in the plant and diffusion down a concentration gradient out through the stomata"

    • Water evaporates from meosphyll cells in leaves into air spaces ⇨ diffuses out via stomata
    • This water loss lowers the water potential ⇨ water moves in from adjacent cells
    • Water replaces this from the xylem
    • Adhesion & cohesion result in capillary action ⇨ water is drawn up xylem by transpiration pull
    • Resulting in tension in the xylem which helps pull water from the soil
    • ~ Cohesion-tension theory
  47. What evidence is there for the cohesion-tension theory?
    • Changes in diameter of trees
    • ⇨ tension during the day reduces their diameter

    • Air drawn into cut stems
    • ⇨ instead of water leaking out
    • ⇨ water no longer drawn up if this happens since the stream is broken
  48. How is transpiration measured?
    Using a potometer
  49. How do stomata open and close in response to the conditions they are in?
    • Favourable conditions:
    • -solutes actively pumped into guard cells
    • -in order to increase turgor pressure
    • -guard cells expand lengthways ~ cellulose hoops prevent expansion widthways
    • -thicker, less flexible inner cell wall causes them to become bean shaped

    • When water is scarce:
    • -hormonal signals from roots trigger turgor loss
    • -stomata close
  50. What factors affect the rate of transpiration?
    • Light intensity: more light ⇨ more stomata open for photosynthesis
    • Relative Humidity: higher humidity ⇨ smaller concentration gradient ⇨ less transpiration 
    • Temperature: Higer temp ⇨ more kinetic energy ⇨ increased evaporation
    • -ALSO higher temp ⇨ increases ability of air to hold water before becoming saturated ⇨ decreasing relative humidity ⇨ less transpiration
    • Air movement: more wind ⇨ greater concentration gradient ⇨ more transpiration 
    • Soil Water Availability: dry conditions ⇨ plant is under water stress ⇨ reduces transpiration
  51. What is translocation?
    • From source to sink
    • Transporting the products of photosynthesis ~ assimilates
    • Mainly sucrose
    • Mainly an active process
  52. How does Phloem Loading work?
    • The apoplast route:
    • Sucrose travels from source via apoplast
    • Companion cells acvtively pump sucrose into cytoplasm
    • -pump H+ ions out using ATP for proton pump
    • -H+ ions return down concentration gradient via cotransport protein
    • -Companion cells have many infoldings for high SA and many mitochondria for ATP
    • Build up of sucrose in companion cells & sieve tube elements means water moves in by osmosis
    • Build up of turgor moves water & assimilates into sieve elements
    • Solute accumulation in source phloem increases turgor pressure ⇨ forcing sap to regions of lower pressure by mass flow
  53. How does phloem unloading work?
    • Sucrose diffuses to any points that need it
    • Converted to another substance ⇨ maintaining concentration gradient
    • -e.g. glucose for respiration or starch for storage
    • Loss of solutes from phloem cause rise in water potential 
    • ⇨ water moves out to surrounding cells
    • ⇨ some water is drawn into transpiration stream
  54. Why is sucrose used in transpiration instead of glucose?
    Not used in metabolism as readily ⇨ less likely to be used during transport process
  55. What evidence is there for translocation?
    • The adaptations of the companion cell for active transport ~ seen via microscope
    • Translocation stops if the mitochondria are poisoned
    • The flow of sugars is 1000X faster than diffusion alone
    • Positive pressure in phloem forces sap out of an aphid's stylet
  56. What are the terms for plants adapted to especially dry conditions and those that live in water?
    • Xerophytes ~ dry
    • Hydrophytes ~ live in water
  57. How do Xerophytes conserve water?
    • Thick Waxy Cuticle
    • Sunken Stomata ⇨ in pits, reducing air movement and forming microclimate of humid air
    • Reduced no. of stomata
    • Reduced leaves ⇨ reducing SA:V ratio
    • Hairy leaves ⇨ microclimate of humid air
    • Curled Leaves ⇨ confines stomata in microclimate of humid air
    • Succulents ⇨ store water in specialised parenchyma tissue
    • Leaf loss ⇨ lose leaves during dry times
    • Root adaptations
    • -long tap roots access water deep in ground
    • -widespread shallow roots collect water during a shower
    • Avoiding the problem
    • -become dormant
    • -die and leave seeds behind
    • -some survive as storage organs
  58. What are the adaptations of Hydrophytes?
    • Thin/No waxy cuticle ⇨ no need to conserve water
    • Many stomata, always open, on upper surfaces ⇨ maximise gaseous exchange
    • Reduced structure ⇨ since water supports the plant
    • Wide, flat leaves ⇨ capture lots of sunlight
    • Small roots ⇨ water is able to diffuse directly into the stem and leaves
    • Air sacs ⇨ keep plant afloat
    • Aerenchyma ⇨ specialised parenchyma 
    • -many large air spaces
    • -helps with buoyancy 
    • -low resistance pathway for substances like oxygen
Author
Hebe
ID
317166
Card Set
Module 3
Description
Outline of Module 3 - exchange and transport AS level Biology
Updated