OCR Biology A Module 3 Flashcards

surface area : volume ratio
entails how easy the exhange of substances is
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exchange in single celled organisms
substances can diffuse directly across the cell surface membrane. this is quick because of the short distance substances have to traveland because of the high sa:v.
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exchange in multicellular organisms
diffusion across outer membranes is inefficient as some cells are deep within the body, there is a low sa:v, larger organisms have a higher metabolic rate than smaller ones.
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features of specialised exchange surfaces
large surface area, thin walls to decrease diffusion distance, a good blood supply, good ventilation
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gas exchange in mammals
lungs get oxygen into the blood for respiration, and remove carbon dioxide ffrom respiring cells.
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features of the mammalian gaseous exchange system
trachea, two bronchi, bronchioles, alveoli, the ribcage, intercostal muscles, diaphragm
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goblet cells
line the airways, secrete mucus which traps microorganisms and dust particles, preventing them from reaching the alveoli
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ciliated epithelium
waft the mucus secreted by goblet cells upwards to be swallowed
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elastic fibres
throughout lungs, help process of breathing through stretching and recoiling
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smooth muscle
walls of tubing of lungs, allows diameter to be controlled. manages resistance to airflow.
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c-shaped cartilage
trachea and bronchi, provide support as it is strong yet flexible, prevents collapse when pressure drops during expiration.
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inspiration and expiration, controlled by diaphragm, intercostal muscles and ribcage
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active process. external intercostal muscles and diaphragm contract, causing ribcage to move up and out and diaphragm to flatten, increasing thorax volume while decreasing lung pressure, causing air to flow in.
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passive process. external intercostal muscles and diaphragm relax, ribcage moves down and in while diaphragm regains shape, throax volume decreases while air pressure increases, air is forced out. expiration can be forced.
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machine used to investigate breathing. must be airtight and subject must clip their nose.
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tidal volume
volume of air in each breath. height of peaks on a graph.
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vital capacity
maximum volume of air that can be inhaled or exhaled. highest peak.
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breathing rate
how many breaths taken per unit time. identified by peaks on a graph.
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oxygen uptake
rate at which a person uses up oxygen. decrease of the volume of gas in the spirometer chamber, read by taking the avergae slope of the trace. volume / time.
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process of a spirometer
oxygen filled chamber with movable lid. breathe through tube connected to chamber>lid moves with breath>recorded by pen attached to lid on rotating drum creating a spirometer trace>carbon dioxide absorbed by soda lime. can use a data logger.
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structure of gills
water enters through the mouth and leaves through the gills, each made of gill filaments/primary lamellae which increase s.a. for exchange. covered in gill plates/secondary lamellae. supported by a gill arch. good blood supply, thin walls.
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counter-current system in fish
blood flows through the gill plates in one direction and water flows through the other. a steep concentration gradient of oxygen is maintained.
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ventilation in fish
fish opens mouth, lowering buccal cavity, increasing its volume and decreasing the pressure, sucking water in. coses its mouth, raising buccal cavity, forcing water over the gill filaments, while pressure opens the operculum, letting water out.
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gas exchange in insects
air moves through the trachae through spiracle pores, allowing oxygen to move down a concentration gradient. trachaea>tracheoles; thin, permeable, go into individual cells, contain fluid which o2 dissolves in, diffuses into body cells. co2 opposite.
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ventilation in insects
rhythmic abdominal movements changes volume of their bodies, moving air in and out of spiracles. wing movements pump thoraxes while they fly.
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single circulatory system
fish. blood passes through the heart once in each complete circuit of the body
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double circulatory system
mammals. blood passes through the beart twice for each complete circuit of the body. pulmonary and systemic systems. faster system.
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closed circulatory system
vertebrates. blood is enclosed in vessels
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open circulatory system
invertebrates. blood flows freely through the body cavity
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carry blood from the heart to the body. thich muscular walls, elastic tissue to stretch as the heart beats (high pressure), folded inner endothelium (expansion and high pressure)
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arteries branch into arterioles. smooth muscle, less elastic, can expand or contract, controlling the amount of blood flowing to tissures
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arterioles branch into capillaries, endothelium is one cell thick to make it efficient for exchange
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capillaries connect to venules, which have thin walls and some muscle cells. connect to veins.
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take blood back to the heart under low pressure. wide lumen with little elastic or muscle tissue. valves prevent backflow. blood flow aided by contractionof muscles around them.
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tissue fluid
fluid that surrounds cells in tissues made from substances that leave plasma. cells take in oxygen and nutrients from the tissue fluid and release metabolic waste into it
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pressure filtration
process by which substances move out of the capillaries into the tissue fluid.
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process of pressure filtration (hydrostatic)
hydrostatic pressure inside the capillaries near the arteries is higher than that of the tissue fluid, so the fluid is passed out of the capillary. this makes the hydrostatic pressure at its lowest near the venules.
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process of pressure filtration (oncotic)
as water leaves the capillaries, the water potential decreases and the concentration of plasma proteins increases, creating oncotic pressure, meaning oncotic pressure is highest near the venule. the low water potential here causes osmosis.
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lymph vessels
not all tissue fluid re-enters the capillaries, some returns to the blood via the lymphatic system. structured like veins, > main lymph vessels in thorax > heart.
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deoxygenated blood
right side (left on page)
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oxygenated blood
left side (right on page)
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direction of blood flow through the heart
vena cava > right atrium > right ventricle > pulmonary artery > pulmonary veins > left atrium > left ventricle > aorta
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atrioventricular valves
link atria to ventricles
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semi-lunar valves
link ventricles to the pulmonary artery / aorta
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opening of valves
only open one way, opening depends on the relative pressure of the chambers. higher pressure behind a valve means it opens, higher pressure in front of a valve means it closes. flow of blood is unidirectional.
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cardiac cycle
ongoing sequence of contraction and relaxation of the atria and ventricles to keep the blood constantly circulating.
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atrial systole
ventricles relax, atria contract, decreasing volume of chambers and increasing pressure, pushing blood to the ventricles through the av valve. as ventricles receive blood, volume and pressure slighly increase.
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ventrical systole
atria relax. ventricles contract, increasing their pressure, forcing av valves shut and opens sl valves, forcing blood out of arteries.
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cardiac diastole
ventricles and atria both relax, closing both sl valves. atria begin to fill again, pushing av valves open passively.
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contract and relax without receiving signals from nerves
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sino-atrial node
wall of the right atrium. biological pacemaker, sends regular waves of electrical activity over atrial walls, causing contractions at the same time. collagen tissue prevents it reaching ventricles, waves pass to avn.
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atrio-ventricular node
passes waves of electricity to the bundle of his. delay before contraction to ensure atria have emptied
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bundle of his
group of muscle fibres responsible for conducting waves of electrical activity to the purkyne tissue
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purkyne tissue
finer muscle fibers in right and left ventricle walls which carry the electrical activity into muscular ventricular walls, causing them to contract from the apex upwards.
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machine which records the electrical activity of the heart, records changes in polarisation as the heard depolarises when it contracts and repolarises when it relaxes. recorded through electrodes placed on the chest.
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p wave (electrocardiogram)
atrial depolarisation
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qrs complex (electrocardiogram)
main peak of the heartbeat caused by depolarisation of the ventricles.
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t wave (electrocardiogram)
repolarisation of the ventricles
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height of wave
how much electrical charge is passing through the heart / contraction strength
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heart rate
bpm = 60 / time taken for one heartbeat
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heartbeat is too fast
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heartbeat is too slow
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ectopic heartbeat
extra heartbeat that interrupts the regular rhythm
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really irregular heartbeat
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large protein with a quarternary structure made of four polypeptides and four haem groups containing iron which obtain an oxygen molecule each
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haemoglobin with oxygen bound to it. reversible reaction.
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association / loading
oxygen binds to haemoglobin
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dissociation / unloading
oxygen leaves oxyhaemoglobin
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affinity for oxygen
tendency for a molecule to bind with oxygen
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partial pressure of oxygen (po2)
measure of oxygen concentration.
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haemoglobin and po2
as po2 increases, so does haemoglobins affinity for oxygen. association at high po2, dissociation at low po2.
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saturation of haemoglobin and affinity for oxygen
when haemoglobin combines with the first o2, the shape alters insofar as its easier for other molecules to bind, bot once it becomes saturated its harder for molecules to join.
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fetal haemoglobin
higher affinity for oxygen than adult as it gets its oxygen through the mothers placenta, which has a loq po2 so that adult haemoglobin dissociates there.
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partial pressure of carbon dioxide (pco2)
measure of carbon dioxide concentration within a cell. haemoglobin dissociates at higher pco2.
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bohr effect (1)
the saturation of blood with oxygen is lower for a given po2, meaning more oxygen is released. this is because co2 affects blood ph; when co2 diffuses into rbcs it reacts with water to form carbonic acid (catalysed by carbonic anhydrase).
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bohr effect (2)
remaining co2 binds to haemoglobinto be carried to the lungs. carbonic acid dissociated into h+ and hco3- ions. increase in h+ causes haemoglobin to dissociate, forming haemoglobinic acid.
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chloride shift (bohr effect (3)
hco3- diffuse into plasma, so to compensate cl- ions diffuce into rbcs, preventing clange in ph.
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bohr effect (4)
when blood reaches the lungs the low pco2 causes some hco3- and h+ ions to recombine into co2 and water > expiration
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xylem tissue
transports water and mineral ions in solution, moving from root to leaf. also for support.
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phloem tissue
transports sugars in solution up and down the plant
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plant vascular system
xylem and phloem
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xylem and phloem in the roots
positioned in the centre to provide support for the root as it pushes through the soil
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xylem and phloem in the stem
xylem and phloem are near the exterior to provide a scaffolding that reduces bending
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xylem and phloem in the leaf
make up a network of veins which support the thin leaves
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adaptations of xylem
long tube-like structures formed from vessel elements joined end to end. no end walls so water can pass up easily. dead so no cytoplasm. thickened with lignin (spiral or ring) so its flexible and water can escape in pits.
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adaptations of phloem
transport solutes from cells in tubes. purely a transport tissue. contains phloem parenchyma, sieve tube elements and companion cells.
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sieve tube elements
form the tube for transporing sugars. end to end; the end walls are the sieve as theyre porous to allow solutes to pass through. no nucleus, thin cytoplasm an few organelles. cytoplasms of adjacent cells connected through sieve plates.
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companion cells
one for every sieve tube element to ensure it survives; carry out living functions for both itself and sieve cells, e.g. provide energy for active transport of solutes.
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symplast pathway in roots
water transport through the cytoplasm. osmosis; moves through plasmodesmata to the xylem.
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apoplast pathway in roots
water transport through the cell walls, absorbed in them or between them, from high hydrostatic pressure to low. when water reaches endodermis in the root, its blocked by waxy casparian *****. now it has to go symplast through a ppm.
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water transport through leaves
leaves the xylem and transports via apoplast pathway. when stomata open water diffuses out
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evaporation of water from a plants surface
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transpiration stream
movement of water from roots to leaves
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cohesion and tension
helps water move up plant against gravity. suction of water up due to transpiration in leaves yanking it out because of cohesion
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water attracted to the walls of the xylem vessels
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gas exchange in plants
opens stomata to let in carbon dioxide for photosynthesis, but through this water leaves down a water potential gradient.
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factors affecting transpiration rate
temperature, light intensity, humidity, wind
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estimating transpiration rate experiment
potometer; distance of air bubble movement per unit time
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plants adapted to living in dry climates, with adaptations preventing them from losing too much water by transpiration.
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plants which live in aquatic habitats. adapted to help them cope with a low oxygen level, e.g. air spaces in tissues, stomata on upper surface, flexible as they are supported by water
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active movement of dissolved substances (assimilates) to their target area from sources to sinks
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where the substance is made (at a high concentration)
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where the substance is used up (at a low concentration)
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enzymes in translocation
maintain a concentration gradient by changing the dissolved substances at the sink, ensuring theres always a lower concentration at the sink than at the source
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mass flow hypothesis
theory of how solutes are transported from source to sink by translocation
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source (step one of mass flow)
active transport used to load solutes into sieve tubes at the sourc, lowering water potential inside sieve tubes, ensuring water enters by osmosis creating high hydrostatic pressure.
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sink (step two of mass flow)
at the sink end, solutes are removed from the phloem to be used up; usually diffusion down a concentration gradient. increases water potential so water leaves by osmosis, lowering hydrostatic pressure.
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flow (step three of mass flow)
pressure gradient from source to sink, pushing solutes along. the higher the concentration of sucrose at the source, the faster the rate of transpiration.
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active loading
used at the source to move substances into companion cells from surrounding tissues, and from companion cells into sieve tubes against a concentration gradient. h+ ions are used to do this with sucrose.
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co-transport protein
carrier protein that binds two molecules at a time; concentration gradient of one moves the other
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active loading step 1
in the companion cell, atp is used to actively transport h+ out of the cell into surrounding tissue cells, setting up a concentration gradient
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active loading step 2
h+ binds to a co-transport protein on a companion cellmembrane and enters the cell down its concentration gradient; a sucrose molecule binds to h+ at the same time, moving against its concentration gradient
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active loading step 3
sucrose molecules transported out of the companion cells and into the sieve tubes by the same process
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Other cards in this set

Card 2


substances can diffuse directly across the cell surface membrane. this is quick because of the short distance substances have to traveland because of the high sa:v.


exchange in single celled organisms

Card 3


diffusion across outer membranes is inefficient as some cells are deep within the body, there is a low sa:v, larger organisms have a higher metabolic rate than smaller ones.


Preview of the back of card 3

Card 4


large surface area, thin walls to decrease diffusion distance, a good blood supply, good ventilation


Preview of the back of card 4

Card 5


lungs get oxygen into the blood for respiration, and remove carbon dioxide ffrom respiring cells.


Preview of the back of card 5
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