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Biology - mr ellis > BIOLOGY MODULE 3 (papers 1 & 3) > Flashcards

BIOLOGY MODULE 3 (papers 1 & 3) Flashcards

exchange and tranport, transport in animals, transport in plants

1
Q

what is the ease of exchange of substances dependent on?

A
  • organisms SA:V
  • smaller animals have larger SA:V
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2
Q

why do multicellular organisms need exchange surfaces?

A

cannot rely on diffusion alone:
- some cells are deep within the body - diffusion distance too large
- smaller SA:V so hard to exchange enough substances to supply large volume
- high metabolic rate so use oxygen and glucose faster

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3
Q

what special features do exchange surfaces have to improve efficiency?

A

large SA e.g. root hair cells
thin e.g. alveoli
good blood supply and/or ventilation e.g. fish gills & alveoli

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4
Q

how are root hair cells adapted to improve efficiency of exchange surfaces? (SA)

A
  • large SA
  • increases rate of absorption of water and mineral ions
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5
Q

how is the alveoli adapted to improve efficiency of exchange surfaces? (THIN)

A
  • each alveolus made from single layer of thin, flat cells (alveolar epithelium)
  • O2 diffuses out alveolar space into blood, CO2 diffuses in opposite direction
  • thin alveolar layer decreases diffusion distance when O2 and CO2 diffusion happens which increases rate of diffusion
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6
Q

how is the alveoli adapted to improve efficiency of exchange surfaces? (VENTILATION/BLOOD SUPPLY)

A
  • have large capillary network, giving each alveolus its own blood supply
  • lungs are ventilated so air constantly replaced
  • helps maintain O2 and CO2 concs
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7
Q

how are fish gills adapted to improve efficiency of exchange surfaces? (VENTILATION/BLOOD SUPPLY)

A
  • gas exchange surface in fish
  • O2 and CO2 exchanged between fish’s blood and surrounding water
  • gills = large network of capillaries - well supplied with blood
  • well-ventilated so fresh water constantly passes over gills
  • maintains conc gradient of O2 and increases rate of O2 diffusing into blood
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8
Q

what are the exchange organs in mammals?

A

the lungs

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9
Q

how are the lungs the exchange organ in mammals?

A
  • as you breathe in, air enters trachea
  • trachea split into 2 bronchi (one bronchus to each lung)
  • bronchus branches off to bronchioles
  • bronchioles end in alveoli where gases are exchanged
  • ribcage, intercostal muscles & diaphragm move air in and out
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10
Q

what are the structures in the gaseous exchange system?

A
  • goblet cells
  • cilia
  • elastic fibres
  • smooth muscle
  • rings or cartilage
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11
Q

what are goblet cells?

A
  • secrete mucus
  • mucus traps microorganisms and dust
  • stops them reaching alveoli
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12
Q

what are cilia?

A
  • beat the mucus
  • moves mucus upward away from alveoli and towards throat
  • prevents lung infections
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13
Q

what are elastic fibres?

A
  • in walls of trachea, bronchi, bronchioles and alveoli
  • help process of breathing out
  • on breathing in, lungs inflate and elastic fibres are stretched, fibres recoil and push air out
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14
Q

what is smooth muscle?

A
  • in walls of trachea, bronchi and bronchioles
  • allows diameter to be controlled
  • exercises makes smooth muscle relax & tubes widen so less resistance to air flow in and out lungs
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15
Q

what are rings of cartilage?

A
  • in walls of trachea and bronchi
  • provide support
  • strong but flexible so stops trachea and bronchi collapsing when breathing in
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16
Q

which epitheliums are ciliated in the lungs?

A

trachea
bronchi
larger bronchiole
smaller bronchiole

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17
Q

which epitheliums are not ciliated in the lungs?

A

smallest bronchiole
alveoli

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18
Q

what is ventilation in mammals?

A

breathing in and out

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19
Q

what happens during inspiration?

A
  • external intercostal & diaphragm muscles contract
  • causes ribcage to move up & out and diaphragm flatten, increasing volume of thorax
  • when thorax volume increases, lung pressure decreases
  • causes air flow into lungs
  • active process - requires energy
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20
Q

what happens during expiration?

A
  • external intercostal & disphragm muscles relax
  • rubcage moves down & in
    thorax volume decreases, air pressure increases
  • air forced out lungs
  • passive process - doesnt require energy
  • expiration can be forced (internal intercostal muscles contract)
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21
Q

what is tidal volume?

A

volume of air in each breath

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22
Q

what is vital capacity?

A

maximum volume of air that’s breathed in and out

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23
Q

what is breathing rate?

A

how many breaths are taken (usually per min)

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24
Q

what is oxygen consumption/oxygen uptake?

A

rate that an organism uses up oxygen

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25
Q

what can be used to investigate breathing?

A

spirometer

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26
Q

how does a spirometer work?

A
  • has oxygen-filled chamber with movable lid
  • person breathes through tube connected to oxygen chamber
  • when breathing, chamber moves up and down
  • movements recoded with pen attached to lid of chamber (spirometer trace)
  • soda lime in tube breathes into absorbs CO2
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27
Q

what happens to the total volume of gas in the chamber?

A
  • decreases over time as air thats breathed out is a mixture of CO2 and O2 but CO2 is absorbed by soda lime
  • oxygen gets used up in respiration
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28
Q

explain how fish use a counter-current flow system for gas-exchange

A
  • water enters fish’s mouth and passes out through gills
  • gill plates have thin surface layer of cells to speed up diffusion
  • blood flows through gill plates in one direction and water flow in opposite direction (counter current)
  • conc of oxygen in water is always higher than in blood
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29
Q

what is the structure of a gill?

A
  • made of thin branches (gill filaments) so have a large SA for gas exchange
  • gill filaments are covered by many gill plated
  • each gill supported by a gill arch
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30
Q

how are fish gills ventilated?

A
  • fish opens mouth, lowering floor of buccal cavity
  • volume of buccal cavity increases, decreasing pressure in cavity so water is sucked in
  • when fish closes mouth, floor of buccal cavity raises so volume inside cavity decreases, pressure increases so water is forced out across gill filaments
  • each gill’s covered by a bony flap (operculum) to protect gill
  • increased pressure forces operculum on each side of head to open so water leaves gill
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31
Q

how do you dissect a gill?

A
  • place fish on dissection tray
  • push back operculum and use scissors to remove gills
  • cut each gill arch through bone at top and bottom
  • draw gill and label it
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32
Q

what do insects use to exchange gases?

A

tracheae

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33
Q

how do insects use tracheae to exchange gases?

A
  • air moves into tracheae through pores on insect surface (spiracles)
  • oxygen goes down conc gradient to cells, CO2 from cells moves down its own conc gradient to be released into atmosphere
  • tracheae branch off into smaller tracheoles & have thin, permeable walls
  • tracheoles also contain fluid that O2 dissolves in
  • O2 diffuses into body cells, CO2 diffuses in opposite direction
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34
Q

how do you dissect the gaseous exchange system in insects?

A
  • fix insect to dissecting board
  • examine tracheae, then cut & remove exoskeleton from abdomen
  • use syringe to fill abdomen with saline solution to see tracheae (looks sliver)
  • can examine tracheae under light microscope with wet mount, should see rings of chitin in walls of tracheae
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35
Q

what is the circulatory system like in a fish?

A
  • single
  • closed
  • heart pumps deoxygenated blood to gills and then blood goes oxygenated from gills to rest of the body, then turns deoxygenated and goes back to heart
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36
Q

what is the circulatory system like in a mammal?

A
  • double
  • closed
  • right side pumps doxygenated blood to lungs
  • from lungs blood goes oxygenated and travels back to the heart, then to the left side to rest of the body
  • from rest of the body it goes to the heart, when blood enter heart, it enters right side again
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37
Q

which system sends blood to the lungs?

A

pulmonary system

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38
Q

which system sends blood to the rest of the body (not lungs)?

A

systemic system

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39
Q

what is the advantage of the mammalian double circulatory system?

A

can give blood an extra push between the lungs and rest of the body - oxygen is delivered to tissues more quickly

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40
Q

what is a closed circulatory system?

A
  • blood is enclosed within blood vessels
  • heart pumps blood to arteries which branch out into capillaries
  • substances diffuse from blood in capillaries into body cells but blood stays
  • veins take blood back to heart
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41
Q

what is an open circulatory system?

A
  • blood isnt enclosed in blood vessels all the time
  • heart is segmented so contracts in a wave starting from the back, pumping blood into single main artery
  • artery opens up into body cavity
  • blood flows around insects organs, makes its way back to heart through valves
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42
Q

how does an open circulatory help an insect?

A

supplies insects cells with nutrients

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43
Q

how do the insects cells get supplied with oxygen?

A

done by a system of tubes called tracheal system

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44
Q

what are the 5 types of blood vessels?

A
  • arteries
  • arterioles
  • capillaries
  • venules
  • veins
45
Q

what are arteries?

A
  • arteries carry blood from the heart to the rest of the body
  • thick and muscular walls and have elastic tissue to stretch and recoil with heart beat to maintain high pressure
  • folded endothelium allows artery to expand
  • carried oxygenated blood to lungs (except pulmonary arteries)
46
Q

what are arterioles?

A
  • arteries branch into arterioles (smaller)
  • layer of smooth muscle but less elastic tissue
  • smooth muscle allows them to expand/contract to control blood flow to muscles
47
Q

what are capillaries?

A
  • branch from arterioles
  • smallest blood vessels
  • substances like glucose are exchanged between cells in capillaries so are adapted for efficient diffusion (walls are one cell thick)
48
Q

what are venules?

A
  • connected to capillaries
  • very thin walls that contain some muscle cells
  • join together to form veins
49
Q

what are veins?

A
  • take deoxygenated blood back to the heart at low pressure (except pulmonary veins - oxygenated)
  • wider lumen than arteries, little elastic or muscle tissue
  • have valves to stop backflow of blood against gravity
  • blood flow through veins is helped by body muscles
50
Q

what is tissue fluid?

A
  • fluid that surrounds cells in tissues
  • made from substances that leave blood plasma
  • no RBCs as they’re too large to be pushed through capillary walls
  • cells take oxygen and nutrients from tissue fluid - substances move out capillaries to tissue fluid through pressure filtration
51
Q

what is pressure filtration?

A
  • artery end of capillary bed, hydrostatic pressure inside capillaries is larger than pressure in tissue fluid
  • pressure forces fluid out capillaries into spaces around cells to form tissue fluid
  • as fluid leaves, hydrostatic pressure in capillaries lowers so hydrostatic pressure at vein end is much lower
  • oncotic pressure is generated by plasma proteins
  • at venule end, WP is lower in capillaries than in tissue fluid due to fluid loss and high oncotic pressure
  • means some water re-enters capillaries from tissue fluid at venule end by osmosis
52
Q

what happens to the tissue fluid that doesnt re-enter capillaries at venule end of capillary bed?

A

gets returned to blood through lymphatic system made of lymph vessels:
- excess tissue fluid passes into lymph vessels, when inside its lymph
- valves in lymph vessels stop lymph going backwards
- lymph moves towards main lymph vessels in throax and returned to blood near the heart

53
Q

what is in blood?

A
  • RBCs
  • WBCs
  • platelets
  • proteins
  • water
  • dissolved solutes
54
Q

what is in tissue fluid?

A
  • no RBCs
  • very few WBCs
  • no platelets
  • very few proteins
  • water
  • dissolved solutes
55
Q

what is in lymph?

A
  • no RBCs
  • WBCs
  • no platelets
  • proteins (only antibodies)
  • water
  • dissolved solutes
56
Q

what is cardiac output and how do you calculate cardiac output?

A
  • volume of blood pumped by the heart per minute (cm3 min-1)
    cardiac output = heart rate x stroke volume
57
Q

what does it mean when the heart is myogenic?

A

it can contract and relax without receieving signals from nerves - controls the regular heart beat

58
Q

what is the cardiac cycle?

A
  • depolarisation spreads from SAN over atria
  • left & right atria contract and pump blood into ventricles
  • wave reaches AVN transmitted to bundle of His
  • wave transmittted along Purkyne fibres into ventricle
  • ventricles depolarise, pumping blood into arteries
  • atria and ventricles relax
  • when its relaxing, atria fill with blood from vena cava and pulmonary vein
59
Q

what is the function of purkyne tissue?

A

carries wave of electrical activity into muscular walls of right and left ventricles, making them contract simultaneously

60
Q

what is the function of the SAN?

A
  • pacemaker
  • sets rhythm of heartbeat by sending out regular waves of depolarisation to atrial walls
61
Q

what does an electrocardiograph do?

A
  • records electrical activity of the heart
  • uses electrodes placed on the chest
62
Q

what is trachycardia?

A

heart beats too fast so isnt pumping blood efficiently

63
Q

what is bradycardia?

A

heart beats too slow

64
Q

what is fibrillation?

A
  • irregular heartbeat
  • atria or ventricles lose their rhythm and stop contracting properly
65
Q

what is an ectopic heartbeat?

A
  • ‘extra’ heart beat
  • caused by early contraction of the atria than previous heartbeats
  • can be caused by early contraction of ventricles
66
Q

how is oxygen carried round the body?

A
  • RBCs contain Hb
  • Hb has high affinity for oxygen (each molecule carries 4 oxygen)
  • in lungs, oxygen joins to iron to form oxyhaemoglobin
  • Hb + 4O2 ⇌ HbO8
67
Q

what does haemoglobin saturation depend on?

A

partial pressure of oxygen (pO2)
- oxygen loads onto Hb to for HbO8 = ↑ pO2
-HbO8 unlads its oxygen = ↓pO2

68
Q

explain the partial pressure of oxygen in terms of haemoglobin saturation

A
  • is a measure of O2 conc.
  • ↑ conc of dissolved oxygen in cells = ↑ partial pressure
  • oxygen enters blood capillaries at alveoli (high pO2) in lungs
  • when cells respire they use up oxygen, lowering pO2
  • RBCs deliver HbO8 to respiring tissues to unload oxygen
  • Hb goes back to lungs for more O2
69
Q

what do dissociation curves show?

A
  • show how affinity for oxygen varies
  • it is a sigmoid curve and plateau’s when all haemoglobin is oxyghaemoglobin
70
Q

how do you know if something has a higher or lower affinity for oxygen/ what is the shift?

A

further left = higher affinity

71
Q

why is the dissociation curve an S shape?

A
  • Hb binds with first O2 molecule, its shape alters & makes it easier for other molecules to join
  • more saturated Hb makes it harder for O2 to join
72
Q

why does fetal haemoglobin have a higher affinity for oxygen than adult haemogobin?

A

fetus is better at absorbing oxygen from mothers blood
- fetus gets oxygen from mothers blood across placenta
- when mothers blood reaches placenta, oxygen saturation ↓
- fetus must have high affinity for O2 to get enough O2 to survive
- is Hb had same affinity as adult Hb, its blood would be too unsaturated

73
Q

how does carbon dioxide concentration affect oxygen unloading?

A
  • Hb gives up O2 more readily at partial pressures of CO2
  • most CO2 from respiring tissues diffuses into RBCs & reacts with water and carbonic acid (catalysed by carbonic anhydrase)
  • carbonic acid dissociates to give H+ ions and hydrogencarbonate ions
  • increase in H+ ions makes HbO8 unload its O2 and forms haemoglobinic acid
  • hydrogencarbonate ions diffuse out RBCs and transported in blood plasma
  • chloride ions diffuse into RBCs (chloride shift)
  • when blood reaches lungs, low pCO2 causes some hydrogencarbonate and H+ ions to recombine with CO2
  • CO2 then diffuses into alveoli
74
Q

what is the chloride shift?

A
  • chloride ions diffuse into RBCs to compensate for loss of hydrocarbonate ions
  • maintains balance of charge between RBCs and plasma
75
Q

how is xylem tissue involved in transport in plants?

A
  • transports water and mineral ions in solution
  • these substances move up the plant from roots to leaves
  • makes up vascular system
76
Q

how is phloem tissue involved in transport in plants?

A
  • transports sugars in solution both up and down the plant
  • makes up vascular system
77
Q

what is the structure of a root?

A

xylem in centre surrounded by phloem to provide support for root as it pushes through the soil

78
Q

what is the structure of a stem?

A

xylem and phloem both near the outside to reduce bending

79
Q

what is the structure of a leaf?

A

xylem and phloem make up a network of veins which support thin leaves

80
Q

how are xylem vessels adapted fro transporting water and mineral ions?

A
  • long, thin tube-like structures formed on vessel elements
  • no end walls to make uninterrupted tube to allow water to pass though easily
  • cells are dead - no cytoplasm
  • walls are thickened by lignin for support (spirals or rings)
  • lignin increases with age
  • water and ions move in and out vessels through small pits where there is no lignin
81
Q

how is phloem tissue adapted for transporting solutes?

A
  • cells arranged in tubes
  • tissues contain phloem fibres, phloem parenchyma, sieve tube elements and companion cells
82
Q

what are sieve tube elements?

A
  • living cells that form the tube for transporting solutes
  • joined end to end to form sieve tubes
  • sieve parts are at the end walls which have lots of holes to allow solutes to pass through
  • no nucleus, thin layer of cytoplasm and few organelles
  • cytoplasm of adjacent cells is connected through holes in sieve plates
83
Q

what are companion cells?

A
  • lack of nucleus and other organelles means sieve tube elements cant survive alone
  • companion cell for every sieve tube element
  • carry out living functions of themselves and sieve tube element
84
Q

how do you dissect a plant?

A
  • use blade to cut cross-section of stem as thin as possible
  • use tweezers to place sections in water until use to stop them drying out
  • transfer sections to a dish containing stain
  • rinse off sections in water and mount onto slide
85
Q

how does water enter the plant?

A
  • through root hair cells and then root cortex (incl. endodermis)
  • water drawn into roots via osmosis (down WP gradient)
86
Q

how does water move down a WP gradient?

A
  • water always moves from HIGH WP to LOW WP
  • soil in roots has high WP and leaves have lower WP (due to evaporation)
  • creates WP gradient that keeps moving through the plant, from roots to leaves
87
Q

what is the symplast pathway?

A
  • water moves through the cytoplasm
  • cytoplasms of neighboring cells connect through plasmodesmata
  • water moves by osmosis
88
Q

what is the apoplast pathway?

A
  • water moves through cell walls
  • walls are very absorbent so water can diffuse through them
  • water also carries solutes and move from high hydrostatic pressure to low hydrostatic pressure (MASS FLOW)
89
Q

what is the Casparian strip and how does this affect the apoplast pathway?

A
  • when water in apoplast pathway gets to endodermis cells in the root, its path is blocked by a waxy strip of cell walls (casparian strip)
  • means water has to go through symplast pathway and cell membrane
  • once past this barrier water moves into the xylem
90
Q

how does water move up the xylem and out the leaves?

A
  • at the leaves water leaves xylem into cells through apoplast pathway
  • water evaporates from cell walls into spaces between cells in leaf
  • when stroma open, water diffuses out the leaf into surrounding air
  • loss of water from plants surface is TRANSPIRATION
91
Q

how does water move up the plant against the force of gravity?

A
  • water evaporates from leaves and creates TENSION which pulls water into leaf
  • water is COHESIVE so when some are pulled more follow
  • water enters stem through root cortex
  • ADHESION is responsible for movement of water (water is attracted to walls of xylem so water rises up xylem)
92
Q

what is transpiration?

A
  • evaporation of water from a plants surface
  • happens as a result of gas exchange:
    1. plant opens its stomata to let in CO2 to produce glucose (photosynthesis)
    2. also lets water out - higher conc. of water inside than outside
93
Q

how does light affect transpiration rate?

A
  • lighter = faster transpiration
  • stomata open when it gets light so CO2 can diffuse into leaf for photosynthesis
94
Q

how does temperature affect transpiration rate?

A
  • higher temp = faster transpiration
  • warmer water molecules have more energy so evaporate from leaf faster
  • this increases WP gradient making water diffuse out leaf faster
95
Q

how does humidity affect transpiration rate?

A
  • lower humidity = faster transpiration
  • if air is dry, WP gradient between air and leaf increases, increasing transpiration
96
Q

how does air movement/wind affect transpiration rate?

A
  • windier = faster transpiration
  • air movement blows water molecules from stomata
  • this increases WP gradient
97
Q

how do you use a potometer to estimate transpiration rate?

A
  1. cut shoot underwater at slant
  2. assemble potometer in water & insert shoot underwater so no air enters
  3. remove apparatus from water but keep capillary tube submerged in water beaker
  4. check apparatus is water and air tight
  5. dry leaves
  6. remove end of capillary tube from beaker until one air bubble forms
  7. record starting position of air bubble
  8. use stopwatch to record distance of bubble moves per unit time (rate of movement = transpiration estimate)
98
Q

what are xerophytes?

A
  • adapted to reduce water loss
  • live in dry habitats
99
Q

how has marram grass/cacti adapted to reduce water loss?

A
  • (marram grass) stomata in sunken pits to shelter from wind
  • (marram grass) hair on epidermis to trap moist air to reduce WP gradient between leaf and air
  • (marram grass) roll their leaves up in hot/windy conditions to trap moist air and reduced exposed SA
  • both have thick, waxy later on epidermis to reduce water loss by evaporation
  • (cacti) spines instead of leaves to reduce SA
  • (cacti) close stomata at hottest time of day
100
Q

what are hydrophytes?

A
  • live in aquatic habitats
  • dont need adaptations to reduce water loss
  • need adaptations to help cope with low oxygen levels
101
Q

how are hydrophytes adapted to cope with low oxygen levels?

A
  • air spaces in tissues help plants float and can act as a store for oxygen e.g. water lillies float on surface and absorb more light for photosynthesis
  • stomata only present on upper surface of floating leaves helps maximise gas exchange
  • have flexible leaves and stems, prevents damage by water currents, plants are supported by water
102
Q

what is translocation?

A
  • movement of dissolves substances (assimilates) where theyre needed in a plant
  • is an energy requiring process that happens in phloem
  • moves substances from sources to sinks
103
Q

what are sources?

A

where substance is made (high concentration there)
- e.g. sucrose

104
Q

what are sinks?

A

where substance is used up (low concentration there)
- e.g. other parts of the plant like food storage organs and meristems

105
Q

how do enzymes maintain a concentration gradient from source to sink?

A

by changing the dissolved substances at the sink (e.g. by breaking them down or making them into something else)
- this makes sure there’s always a lower conc at sink than source

106
Q

how does mass flow hypothesis explain phloem transport?

A

1a. active transport is used to actively load solutes into sieve tubes of phloem at source
1b. this lowers WP inside sieve tubes so water enters tubes by osmosis from xylem and companion cells
1c. creates high pressure at source end of phloem
2a. at sink end, solutes are removed from phloem to be used
2b. this increases WP inside sieve tube to water leaves by osmosis
2c. lowers pressure in sieve tubes
3a. result = pressure gradient from source to sink
3b. gradient pushes solutes along sieve tubes to where they’re needed

107
Q

how do substances enter the phloem?

A

active loading

108
Q

what is active loading?

A
  • used to move substances into companion cells from surrounding tissues and sieve tubes
  • concentration of sucrose is higher in companion cells than surrounding tissue cells
  • so sucrose is moved using ACTIVE TRANSPORT and CO-TRANSPORTER PROTEINS
109
Q

how is sucrose moved using active transport and co-transporter proteins?

A
  • in companion cells ATP is used to actively transport H+ ions out the cell to surrounding tissue
  • sets up con. gradient (more H+ in tissue than companion cell)
  • H+ ion binds to co-transporter protein in companion cell membrane and re-enters cell
  • sucrose binds to co-transporter molecule at the same time so H+ moves sucrose into cell
  • sucrose molecules are transported out companion cells into sieve tubes

Biology - mr ellis (76 decks)

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