3.3 Organisms Exchange with their Environment Flashcards
surface area of a cube, cuboid and cylinder
cube (ll) * 6 sides
cuboid 2(lwlh*hw)
cylinder 2PiR + 2PiR~H
3 adaptations of the tracheal system of an insect
1- tracheoles branched to increase surface area
2 - tracheoles have thin walls to reduce diffusion pathway
3 - in stages of movement, fluid is forced out the ends to allow for rapid diffusion
3 adaptations of a xerophyte to prevent water loss
1 - sunken stomata to trap water vapour to reduce water potential gradient
2 - small/needle shaped to reduce surface area for water to be lost across
3 - waxy cuticle/waterproof which is impermeable to gases
why is the metabolic rate higher in smaller organisms
the larger the surface area to volume ratio, the more heat loss, the more respiration needed to produce the heat lost
how is the alveolar endothelium adapted
one cell thick epithelial layer to ensure short diffusion pathway
branched to increase surface area
very close to capillaries to ensure short diffusion distance and steep concentration gradient
moist lining so gases can easily dissolve across
how is the atria different to ventricles
ventricles have thicker muscular walls to contract with enough force to provide the necessary pressure
explain how air movement affects transpiration rate
a good airflow removes water vapour from the air so the concentration gradient between the leaf and air is maintained which increases water loss
explain how humidity affects transpiration rate
causes less transpiration because if air is saturated with water vapour, the concentration gradient is weaker so less water is lost
explain how light intensity affects transpiration rate
higher intensity causes more transpiration because the guard cells become turgid so the stomata open allowing water to be lost
explain how temperature affects the rate of transpiration
the higher the temperature, the more transpiration occurs as particles have more kinetic energy so diffusion occurs faster
define the hydrostatic pressure
the residual pressure from the heart beating which is created when blood is forced through the capillaries
define oncotic pressure
the movement of fluid out of the capillaries which causes the water potential of the capillaries to decrease
describe the process of tissue fluid formation
there is a high hydrostatic pressure at the arterial end of the capillary and the HSP inside is higher than that in the tissue fluid
this difference in pressure forces water and other small molecules out of the capillary to form tissue fluid
this causes the HSP in the capillary to decrease as water leaves it
the WP at the venue end is lower than the tissue fluid due to a loss of fluid and proteins remaining
some tissue fluid returns to the capillary from the venule end via osmosis
excess TF is drained into the lymphatic system
explain a closed, double circulatory system
blood is confined to the vessels and passes twice through the heart for each complete circuit of the body
simply, describe the journey of blood through the circulatory system
deoxygenated blood to the vena cava to the right atrium
out the right ventricle via the pulmonary artery to the lungs
oxygenated blood via the pulmonary vein from the lungs into the left atrium
out the left ventricle via the aorta to the body
define myocardial infarction
when the coronary arteries are blocked so an area of the heart gets no blood so no oxygen can be used for respiration and the cells begin to die
explain how the structure of an arteriole is related to its function
a tough fibrous outer layer resists pressure changes
a muscle layer which contracts to control and reduce blood flow
an elastic layer which recoils to maintain blood pressure
a thin endothelium which is smooth to reduce friction and thin for a short diffusion pathway
explain how the structure of an artery is related to its function
a relatively thick muscle layer which constricts and dilates to control blood flow and thus the blood pressure
a comparatively thick elastic layer which stretches and recoils to help maintain high pressure
a large thickness which resists the vessel from bursting from pressure
no valves because the high pressure prevents blood from flowing backwards
explain how the structure of a vein is related to its function
thin muscle layer because blood doesn’t flow to tissues so contraction/dilation isn’t necessary
thin elastic layer because they have a low blood pressure
small thickness because they have a low pressure
valves because the low pressure means blood might flow backwards
explain the process of the movement of water across the cells of a leaf
mesophyll cells lose water to the air spaces by evaporation
the cells now have a lower WP so water enters them by osmosis from neighbouring cells
this lowers their water potential which, in turn, draws in more water from neighbouring cells by osmosis
explain the process of transpiration
water evaporates from the mesophyll cells
due to cohesion, water molecules form hydrogen bonds between one another
due to adhesion, the water molecules form a continuous, unbroken stream down the xylem
more water is drawn up behind the stream as it evaporates
due to tension, the column of water is pulled up the xylem
explain how a xylem vessel is adapted to its function
made of dead cells so water can move through unaffected
lignification which supports and strengthens the structure
no end walls so water can move in an unbroken and continuous tube
what are bordered pits
cavities in the lignified walls for water to flow between vessels
define a source and a sink
a source is a site of production of sugars
a sink is where the sugars will be used or stored for future use
explain the mechanism of translocation
sucrose is made from the products of photosynthesis and diffuses down the CG by facilitated diffusion into the companion cells
H+ ions are actively transported from companion cells into spaces within cell walls
the ions then diffuse down the gradient into sieve tube elements
the sieve tubes have a lower WP so water moves from the xylem into sieve tubes by osmosis, creating a higher hydrostatic pressure
at the sink, sucrose is used so more is drawn in via active transport causing the hydrostatic pressure to decrease and increase at the source
as a result, a mass flow of sucrose occurs down the hydrostatic pressure gradient at STEs.
what are companion cells responsible for
supporting sieve elements by carrying out respiration/metabolism
describe the structural differences between companion cells and sieve tube elements
companion cells have a dense cytoplasm with lots of mitochondria and large nuclei but sieve tubes have little cytoplasm, no nucleus and ribosomes
where are the atrioventricular valves and what is there function
between the left atrium and ventricle + between the right set
they prevent back flow by closing when contraction of the ventricles means ventricular pressure exceeds atrial pressure
this ensures that blood moves to the aorta and pulmonary artery instead of the atria
where are the semi lunar valves and what is their role
they are in the aorta and pulmonary artery
they close to prevent back flow into ventricles when the pressure in vessels is higher than that in the ventricles
this occurs when the elastic walls of the vessels recoil and their pressure increases and when the ventricular walls relax to decrease their pressure
define cardiac output
the volume of blood is pumped by one ventricle of the heart in one minute
define stroke volume
the volume of blood pumped out at each beat
how is the structure of the capillary related to its function
the walls consist mostly of the lining layer so there is a short diffusion pathway for a quick rate
they are numerous and highly branched which increases the surface area for exchange
narrow diameter so they can permeate tissues and ensure a short diffusion pathway to all cells
narrow lumen so they are close to cells for a short DP
there are spaces between the endothelial cells to allow white blood cells to escape in order to deal with infections
state the equation for cardiac output
CO = Heart Rate * Stroke Volume
explain the events in diastole
muscles in the heart relax
atrioventricular valves open because the atrial pressure has increased
blood therefore flows into ventricles
the atria are filled with blood
semi lunar valves remain shut as ventricular pressure is lower than the arteries
describe atrial systole
atria walls contract
atrioventricular valves are open still
this forces the remaining blood into the ventricles from the atria
semilunar valves are shut
describe ventricular systole
ventricles contract
av valves shut because the ventricular pressure has increased
semi lunar valves then open and blood is forced into the arteries
describe the relationship between the position of the dissociation curve and oxygen affinity
the further the left the curve, the greater the affinity because oxygen was associated at lower partial pressures. the further the right the curve, the lower the affinity because oxygen was only associated at relatively high partial pressures.
explain the Bohr effect of carbon dioxide on haemoglobin
the higher the rate of respiration the more carbon dioxide is produced by tissues
the large amount of carbon dioxide lowers the pH
the lower the pH the greater the HmG shape change
oxygen is thus more readily unloaded
so there is more oxygen available for respiration
describe the structure of haemoglobin
proteins with a quaternary structure, each polypeptide chain is associated with a haem group that contains an Fe2+ ion which can combine with a single oxygen molecule
state the site of association and dissociation
associating in the lungs where hmg binds with oxygen
dissociating in tissues where hmg releases oxygen
what does a high and low affinity mean
high affinity means easy association and that it’s harder to dissociate
low affinity means easy dissociation and that it’s harder to associate
explain the sigmoid shape of the oxyhemoglobin dissociation curve
1- the gradient is shallow because at low partial pressures oxygen, little oxygen can bind. this is because the hmg shape makes it difficult for the first oxygen molecule to bind to a haem group
2- after the first binding, the quaternary structure/shape changes which makes it easier for other fe2+ ions to bind. this means it takes a smaller increase in partial pressure oxygen for the second oxygen to bind than the first. the gradient steepens.
3- after the third binding, due to probability it is harder for the 4th molecule to bind because it is less likely to find an unoccupied site. the gradient reduces and flattens.
describe the process of absorption of triglycerides
micelles come into contact with the epithelial cells lining the villi
this causes the break down of micelles to release monoglycerides and fatty acids
these are non polar so can easily diffuse across the cell surface membrane into epithelial cells
define emulsification
when large lipid globules are broken down into several small lipid globules
explain how hydrolysis of lipids occurs
lipase breaks down lipids via hydrolysis creating monoglycerides and fatty acids
these attach with bile to form micelles which carry fatty acids and monoglycerides into the intestinal endothelium via endocytosis
cholesterol is added across the molecule
micelles release the acids and MGs so they diffuse across the membrane into the cell due to non-polarity
describe the 4 steps to carbohydrate digestion
1- salivary amylase hydrolyses starch in the mouth into maltose
2- this is swallowed into the stomach where acid denatures amylase and prevents any further hydrolysis of starch
3- once passed into the small intestine, pancreatic amylase continues hydrolysis of starch into maltose
4- when at the ileum, the epithelial lining produces maltase to hydrolyse maltose into alpha glucose
explain the adaptations of villi for their function
they increase surface area for diffusion
very thin endothelial cells to reduce DP
muscular so can mix contents to maintain a CG
good supply of blood to maintain gradient
microvilli further increase SA for diffusion
what does the smooth muscle in bronchi do
dilates when more air is needed and constrict when less air is needed
describe the features of the alveoli
numerous to increase SA
thin walls to reduce diffusion pathway
extensive capillary network to maintain a steep CG
what happens if guard cells become flaccid
stomata close so no more water can be lost through them
describe what happens to diffusion when an insect is anaerobically respiring
there is a quicker rate because the production of lactate lowers the WP in muscle cells so water at the trachiole ends is drawn into respiring muscle by osmosis. this allows for quicker diffusion of gases.
state the structure of a gill
there is a series of gills on each side
each gill arch is attacked to two stacks of filaments
there are rows of lamellae on the surface of each filament
the lamellae surface has a single layer of flattened cells covering the network of capillaries
describe and explain the structure of leaves of dicotyledonous plants
they have a waterproof cuticle to reduce water loss
the upper epidermis is full of tightly packed cells
the palisade mesophyll has elongated cells with chloroplasts
the spongy mesophyll provides air spaces for carbon dioxide to diffuse into cellls quickly
stomata and guard cells control water loss and are thin for a short DP
carbon dioxide is quickly used to maintain the CG
describe what happens when the guard cells are turgid
the stoma remain open to allow air to enter
describe the need for a specialised system of gas exchange
a supply of oxygen is needed for aerobic respiration to produce ATP for biochemical processes
remove of carbon dioxide is necessary because accumulation alters the pH in cells
describe how the tracheal system of insects is specialised for their function
a spiracle which is often closed to prevent water loss
trachea walls have rings of cartilage to prevent collapsing when breathing pressure changes
as oxygen is used quickly by respiring tissues, a CG is maintained so more is drawn into the spiracles
describe how more active insects supply themselves with more oxygen
they close their spiracle and use muscles to create movement for ventilation which creates a mass flow of air into the trachea
describe and explain the method of using a potomètre
1- cut the plant shoot under water (to prevent air entering)
2- place the shoot in the tube and set up apparatus necessary
3- make sure the tube is airtight using vaseline to seal any gaps (if air enters it will affect readings)
4- dry the leaves of the shoot (moisture affects rate)
5- remove the capillary from the water beaker to allow a single air bubble then put it back
6- set up your environmental factor and allow the plant to adapt
7- record the starting location of the air bubble and leave for a time period
8- then record the end location of the bubble
9- change your investigation factor and reset the bubble by opening the tap, repeat
how would you provide the airflow, humidity, light intensity and temperature for the photometer experiment
a fan, spray water in a plastic bag and wrap around the plant, change the distance of the light source from the plant and use the room temperature
