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Exchange and Mass Transport Flashcards

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1
Q

Alveoli Adaptations

A
  • many alveoli (increase surface area)
  • squamous epithelium walls (short diffusion path)
  • folded walls (increase surface area)
  • ventilation/blood circulation (maintains concentration gradient)
  • narrow capillaries compress red blood cells (short diffusion path)
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2
Q

Explain why multicellular organisms require gas exchange systems

A
  • large volume of living cells
  • high metabolic requirements
  • small surface area to volume ratio
  • large diffusion path
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3
Q

Reasons mammalian lungs are within the body

A
  • air alone is not dense enough to protect delicate structures
  • reduces water loss to maintain moist gas exchange surface
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4
Q

Give adaptations of airways

A
  • ciliated epithelium (goblet cells produce mucus) traps dust and antigens which cilia move upwards for removal
  • smooth muscles constrict to protect alveoli from dust and particulates
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5
Q

Ventilation

A

Movement of air into and out of lungs

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6
Q

Describe the process of inspiration in terms of pressure changes in the thoracic cavity

A
  • external intercostal muscles contract and internal relax
  • diaphragm contracts and flattens
  • pressure decreases
  • volume increases as lungs fill
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7
Q

Describe the process of expiration in terms of pressure changes in thoracic cavity

A
  • internal intercostal muscles contract and external relax
  • diaphragm relaxes and moves up
  • pressure increases
  • volume decreases as lungs empty
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8
Q

Pulmonary Ventilation Rate

A

PVR = tidal volume x breathing rate
tidal volume - volume of air entering lungs with each breath at rest
ventilation rate - number of breaths per minute

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9
Q

Reason insects require specialised gas exchange systems

A
  • small surface area to volume ratio

- very active so high metabolic requirements

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10
Q

Describe adaptations for gas exchange in insects

A
  • tracheoles have thin walls (short diffusion path)
  • tracheoles HIGHLY branched (short diffusion path/large surface area)
  • tracheae tubes are full of air (fast diffusion)
  • fluid in the end of tracheoles that moves into tissues during exercise (so faster diffusion to gas exchange surface)
  • can move body by muscles to move air (maintain steep concentration gradient for oxygen)
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11
Q

Describe ventilation in larger insects

A
  • contract abdominal muscles
  • compresses internal tracheal system
  • pressure changes cause movement of air in and out
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12
Q

Explain how insects are adapted for high activity

A
  • end of tracheoles are filled with water
  • major activity leads to build up of lactate in cells from anaerobic respiration
  • water is drawn into cells by osmosis
  • forces air into end of tracheoles via spiracles
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13
Q

Adaptations of insects to reduce water loss

A
  • small surface area to volume ratio
  • waterproof cuticle
  • spiracle is sunken to trap moisture and prevent evaporation
  • spiracles closed most of the time/open periodically
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14
Q

Suggest why gas exchange surfaces are kept moist

A
  • to allow gases to dissolve

- gases only cross cell-surface membranes if dissolved in aqueous solution

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15
Q

Describe a double circulatory system

A
  • blood circulates in two loops passing through the heart twice in each full circuit
  • one loop consists of the heart and lungs and the other of the heart and rest of the body
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16
Q

Explain why mammals have a double circulatory system

A
  • blood pressure is reduced at the lungs
  • so blood returns to the heart to boost the pressure before travelling to rest of the body
  • high pressure allows oxygen and nutrients to be delivered to muscles quickly
  • necessary due to the high metabolic requirements of mammals
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17
Q

Describe and explain the importance of ventilation in fish

A
  • open mouth to let water in and close to force water through gills in one direction
  • allows for more efficient gas exchange
  • important due to low oxygen concentration in water
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18
Q

Describe adaptations of fish for gas exchange

A
  • MANY gill filaments (increase surface area)
  • lamellae at right angles to filaments (further increasing surface area)
  • walls of lamellae are thin (short diffusion path)
  • counter current flow (maintains steep concentration gradient)
  • ventilation and blood circulation (maintain steep concentration gradient)
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19
Q

Explain counter current flow in fish

A
  • blood and water flow in opposite directions
  • blood always passing water with HIGHER O2 concentration
  • maintains a high concentration gradient across WHOLE length of lamellae (without it equilibrium is reached halfway across lamellae)
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20
Q

Explain why small organisms do not require gas exchange systems

A
  • large surface area to volume ratio

- can obtain enough oxygen through cell-surface membrane

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21
Q

Explain why water is always lost from gas exchange surfaces of terrestrial organisms

A
  • all gas exchange surfaces have to be moist

- water moves down the water potential gradient and evaporates

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22
Q

Function of atrioventricular valves

A
  • prevent backflow of blood into atria when ventricles contract
  • ensure blood moves out of aorta and pulmonary artery
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23
Q

Function of semilunar valves

A
  • prevent backflow of blood into ventricles

- when pressure in aorta/pulmonary artery exceeds ventricles

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24
Q

Function of pocket valves in veins

A
  • ensures blood flows towards the heart

- when skeletal muscles contract and compress veins

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25
Q

Describe and explain features of blood vessels

A
  • fibrous outer layer resists pressure changes
  • muscle layer contracts to control blood flow
  • elastic layer maintains CONSTANT blood pressure and reduce pressure surges by stretching and recoiling
  • squamous endothelium layer is smooth to reduce friction and thin to allow diffusion
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26
Q

Describe how capillaries are adapted to their function

A
  • thin (short diffusion path)
  • branched (large surface area)
  • narrow lumen so red blood cells are compressed against wall (short diffusion path of oxygen)
  • spaces between lining allow white blood cells to enter tissues to treat infection
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27
Q

Tissue fluid

A

Watery fluid containing mineral salts, glucose, urea, small proteins, amino acids and white blood cells

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28
Q

Explain why hydrostatic pressure is lower and water potential is more negative at venous end of capillary

A
  • lower hydrostatic pressure since venous end has wider lumen so less resistance / loss of fluid
  • water potential is more negative since water leaves but large proteins are too large to leave capillary so protein concentration is high
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29
Q

Explain the formation of tissue fluid

A
  • created by ultrafiltration
  • high hydrostatic pressure from arteriole forces water with dissolved substances out of blood plasma
    REJECT blood plasma/ tissue fluid out
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30
Q

Explain how tissue fluid is returned to the blood

A
  • low hydrostatic pressure at venous end of capillary causes tissue fluid to flow back into the capillary
  • down the water potential gradient by osmosis (due to proteins in vessel)
  • EXCESS tissue fluid returned via lymphatic system
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31
Q

Describe the formation of lymph and suggest how it is moved around the body

A
  • filtration of blood plasma normally exceeds reabsorption resulting in EXCESS tissue fluid
  • increase in hydrostatic pressure in interstitial spaces forced fluid into lymphatic capillaries (to prevent build up)
  • returned to the circulatory system near the vena cava
  • moved by hydrostatic pressure and muscular contractions
32
Q

Atrial Systole

A
  • contraction of atrial walls

- ventricles relax and blood flows into them

33
Q

Ventricular Systole

A
  • contraction of ventricles (AV valves close)

- ventricular pressure exceeds aorta and pulmonary artery (SL valves open)

34
Q

Atrial-Ventricular Diastole

A
  • blood enters atria and ventricles from pulmonary vein and vena cava
  • pressure in atria exceeds ventricles (AV valves open)
  • ventricles are relaxed so pressure in lower than in aorta and pulmonary artery (SL valves close)
35
Q

Cardiac Output

A
  • volume of blood pumped by one ventricle in one minute

= heart rate x stroke volume (volume of blood pumped out by each beat)

36
Q

Suggest what causes the typical lub-tub sound of the heartbeat

A
  • lub refers to AV valve closing

- dub refers to SL valve closing

37
Q

Haemoglobin

A
  • red protein responsible for transporting oxygen
  • quaternary structure
  • consists of four polypeptide chains each with a haem group that contains ferrous (Fe2+) ion which can bind to one oxygen molecule
  • each haemoglobin carries 4 oxygen molecules
38
Q

Affect on oxygen affinity in high concentration of :

a) oxygen
b) carbon dioxide
c) carbon monoxide

A

a) increases
b) decreases
c) increases - binds too strongly so oxygen cannot dissociate to supply cells

39
Q

Explain sigmoidal curve

A
  • binding of first oxygen has allosteric effect causing a change in shape of haemoglobin
  • increases affinity of haemoglobin for next oxygen
  • smaller increase in partial pressure required for attachment of next oxygen so curve gets steeper
  • effect is known as positive cooperativity
  • curve flattens out because fewer binding sites are available for attachment of final oxygen
40
Q

Explain a shift of the right on oxygen affinity curve

A
  • lower oxygen affinity AT LOW PP
  • unloading of oxygen MORE READILY at tissues
  • more oxygen in tissues
  • greater rate of respiration for high metabolic activity etc
41
Q

Explain a shift of the left on oxygen affinity curve

A
  • greater affinity to oxygen AT LOW PP
  • useful in low oxygen environments as haemoglobin is fully SATURATED
  • tissues are fully supplied with oxygen
42
Q

Bohr effect

A

Greater concentration of carbon dioxide means haemoglobin has lower oxygen affinity

43
Q

Explain how carbon dioxide changes oxygen affinity

A
  • carbon dioxide dissolved in plasma as carbonic acid
  • blood have a lower pH
  • causes haemoglobin to denature so its tertiary structure changes shape
  • oxygen binds less strongly
44
Q

Adaptations of leaves for gas exchange

A
  • leaves are thin so short distance for gas exchange
  • air spaces in spongy mesophyll so gases can readily diffuse
  • palisade cells give a large surface area for faster diffusion
  • many stomata and spread out to allow diffusion of gases in and out of cell
45
Q

Describe adaptations of xerophytes for limiting water loss

A
  • thick cuticle to increase diffusion distance
  • waxy cuticle to reduce evaporation
  • rolling leaves/ hairs / stomata in sunken pits to trap moist air to decrease water potential gradient
  • spines to reduce surface area to volume ratio
46
Q

Xerophytes

A

Plants that are adapted to living in areas where water is in short supply

47
Q

Explain how transpiration occurs

A
  • water evaporate from surface of mesophyll cells to form water vapour
  • water vapour diffuses through leaf tissue and collects at air spaces surrounding stoma
  • water potential of air spaces next to stomata is higher than surrounding atmosphere
  • water molecules diffuse out into the surrounding air
  • down water potential gradient
48
Q

Explain how water moves up xylem vessels

A
  • transpiration occurs where water evaporates from mesophyll cells
  • lower water potential of leaf tissue
  • H bonds form between water molecules known as cohesion
  • water forms continuous column down xylem
  • when water evaporates more molecules of water are drawn up by transpiration pull
  • adhesion of water to sides of xylem vessel so it is under tension due to negative pressure (cohesion-tension theory)
49
Q

Evidence of cohesion-tension theory in xylem vessels

A
  • diameter of trees are reduces during the day when transpiration rate is highest (tension)
  • broken xylem vessels allows air to enter and water does not leak out (tension) and cannot draw up water as continuous column of water is broken (cohesion)
50
Q

Suggest why transpiration is a passive process

A
  • does not require metabolic energy to take place so water is not actively transported
  • energy is supplied by the sun
51
Q

Explain how a potometer is prepared

A
  • leafy shoot is cut under water to prevent air entering xylem
  • potometer is filled with water and leafy shoot is fitted under water
  • air bubble is introduced in capillary tube
52
Q

Suggest why potometer have a reservoir attached

A

Tap of reservoir can be opened to push air bubble back to start of scale to reset potometer

53
Q

Describe how increasing light intensity affects transpiration rate of plant

A

Increases as more stomata open due to photosynthesis

54
Q

Describe how increasing temperature affects transpiration rate of plant

A

Increases as water molecules have more kinetic energy so more evaporation takes place

55
Q

Describe how increasing humidity affects transpiration rate of plant

A

Decreases due to reduced water potential gradient

56
Q

Describe how wind affects transpiration rate of plant

A

Increases as wind displaces air containing water vapour so maintains a steep water potential gradient

57
Q

Structure of Xylem

A
  • long, continuous tubes with no end wall
  • dead cells
  • cellulose walls contain lignin (forms rings around vessel) so impermeable to water + prevents collapse under tension
58
Q

Structure of Phloem

A
  • made up of sieve tube elements (actively transports solutes) associated with companion cells (provide every for active transport)
  • living cells
  • non continuous
59
Q

Translocation

A

Process by which organic molecules and some mineral ions are transported from one part of a plant to another

60
Q

Suggest why phloem vessels are closer to the outside of the stem rather than xylem vessels

A
  • phloem cells are living so can grow back if damaged
  • xylem vessels are dead so cannot be repaired and
    water cannot travel up plant if damaged
61
Q

Suggest ways organic substances are used at sinks

A
  • respiration
  • growth
  • storage as starch
62
Q

Suggest why it is an advantage to transport sucrose over glucose in phloem

A

Sucrose is a non-reducing sugar so less reactive which means it is less likely to be used during transport

63
Q

Explain why phloem tissue is in close association with xylem vessels

A
  • water flows into phloem by osmosis
  • down water potential gradient from xylem
  • hydrostatic pressure moves organic substances along phloem
64
Q

Translocation

A

Movement of organic molecules and some mineral ions in the phloem from one part of a plant to another

65
Q

Compare structure of sieve tube elements to companion cells

A
  • less cytoplasm
  • fewer organelles
  • larger vacuole
  • no nucleus or ribosomes
  • contains sieve plate
66
Q

Evidence for transport in phloem

A
  • ringing experiment where phloem bark is removed to show organic molecules cannot pass below region of removal so death of tissues and swelling
  • radioactively labelled 14C organic molecules show up in phloem when section of stem is autoradiographed
  • sap removed by aphid contains organic molecules and microscopy shows piercing mouthparts in phloem cells
67
Q

Describe and explain how organic substances are transported in plants

A
  • sucrose diffuses by facilitated diffusion into companion cells from photosynthesising cells
  • H+ actively transported from companion cells into spaces in cells wall using ATP
  • then facilitated diffusion through carrier proteins into sieve tube elements taking sucrose with them (co-transport)
  • lower water potential in sieve tube so water flows in from xylem by osmosis
  • hydrostatic pressure moves organic molecules along
  • hydrostatic gradient maintained as sucrose is actively transported into respiring cells (sink)
68
Q

Suggest why ventilation rate of lab rats increases when carbon dioxide is pumped their chamber

A
  • increase volume of air entering their lungs per minute

- to provide the same amount of oxygen in the same amount of time

69
Q

Role of tendons in heart

A

Prevent valves from inverting

70
Q

Suggest advantage of change in oxygen affinity of haemoglobin for oxygen

A

Ensures rapid uptake of oxygen at lungs and release at tissues

71
Q

Suggest why it is an advantage that sieve cells have fewer organelles than companion cells

A
  • larger cytoplasm

- easier flow of sugars (less resistance)

72
Q

Adaptations of xylem vessel

A
  • hollow tubes with no end cell wall to allow easy passage of water
  • lignified wall gives strength to support plant and prevent collapse under transpiration pull
73
Q

Partial Pressure

A

Contribution of one gas in a mixture to the total pressure exerted by a gas mixture

74
Q

Explain why smaller organisms have higher metabolic requirements compared to larger organisms

A
  • greater surface area to volume ratio
  • heat lost at a faster rate
  • more oxygen required for respiration
75
Q

Explain why cold-blooded organisms are able to exist at much smaller sizes than warm-blooded organisms

A
  • do not have to produce heat to maintain body temperature
  • less energy lost as heat
  • can have greater surface area to volume ratio without significantly greater metabolic requirement
76
Q

Suggest what creates hydrostatic pressure

A

increase in VOLUME

Biology (14 decks)

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