3.3 Organisms exchange substances with their environment Flashcards
what are the three exchange processes?
diffusion: the net movement of substances through a partially permeable membrane down the concentration gradient (Passive)
Osmosis: the net movement of water molecules through a partially permeable membrane from a higher water potential to a lower water potential (Passive)
Active Transport: the movement of molecules and ions across a partially permeable membrane against concentration gradient using ATP and carrier proteins (Active)
for exchange surfaces to be effective the exchange surface of the organism needs to be _______ than the volume
(complete the sentence)
for exchange surfaces to be effective the exchange surface of the organism needs to be larger than the volume
what do organisms need to be able to obtain enough substances?
- a flattened shape so that every cell is not far from the surface (leaf)
- specialised exchange surfaces with large areas to increase the surface area to volume ratio (e.g alveoli in mammals, gills in fish, villi and microvilli of the digestive system)
what are the main features of a specialised exchange surface?
- ) A large surface area compared to volume ratio to increase rate of exchange
- ) very thin so diffusion pathway is short
- ) selectively permeable to allow substances to cross
- ) movement of environmental medium e.g air, to maintain a diffusion gradient
- ) a transport system to ensure movement of the internal medium to maintain the diffusion gradient
what are the roles of mass transport in plants and animals?
in animals: mass transport such as the circulatory system is used to carry blood with glucose and oxygen to the cells as well as substances such as waste, urea CO2 and hormones
in plants: mass transport transports water and solutes in xylem and phloem
how can you express the relationship between the features of a specialised exchange surface
diffusion ∝ surface area x difference in concentration / length of diffusion path
if you increase the surface area you ______ diffusion rate
(complete the sentence)
if you increase the surface area you increase the rate of diffusion
if you increase the difference in concentration gradient you _______ the rate of diffusion
if you increase the difference in concentration gradient you increase the rate of diffusion
if you increase the length of diffusion pathway you ________ the rate of diffusion
(complete sentence)
if your increase the length of diffusion pathway you decrease the rate of diffusion
why are exchange surfaces foudn within the organism?
- to reduce dehydration
- reduce the chance of damage
which process produces heat in your body?
respiration
what is the internal body temperature?
37 degrees celcius
why doesn’t the temperature does not exceed safe levels (37 degrees celcius)?
- because if the temperature is too high then the enzymes cant funcion because they may be denatured so less of you metabolic reaction may take place
- this is because when the temperature is high the bonds in the active site are disrupted from the ezymes vibrating too much
- therefore the active site chages shape and the substrate cn not bind to the active site and catalyse reactions
what are the factors that ensure organisms stay at the correct temperature?
- body size: a small surface area makes it difficult to lose heat e.g a hippo, a large surface area leads to increased heat loss. a mouse needs a high metabolic rate to keep warm
- body shape: animals with compact shape has a small surface area to volume area- minimising heat loss. animals with less compact shape have a large surfacr area to volume ratio so lose heat quicker from their surface
what are some exchange adaptations if body shape or size isn’t an option?
- water loss through surface
- adapted kidney structure so less urine is made and less water is lost
- a high metabolic rate in a cold environment
- consuming food with high energy content (seeds and nuts)
- smaller mamals have larger thicker fur or hibernate
- large animals in hot place e.g elephants have larger ears with increased surface area and hippos spend the day in water to help them lose heat
give two reasons why diffusion is too slow in multicellular organisms for them to absorb and excrete substances this way
- a multicellular organism is too thick for substances to go in and out by diffusion to get to all cells
- surface area is too small to absorb enough subtance
in winter some birds fluff their feathers to trap more warm air close to their body. would you expect this physiological adaptation to be more common amonf small or large birds? explain your answer
larger birds.
larger birds are more sucesptible to heat loss because of their smaller volume to surface area ratio
what are the three main factors of a gas exchange surface?
- ) large surface area
- ) thin (usually one epithelial layer) short diffusion pathway
- ) maintenance of a steep concentration gradient across the exchange surface
describe gas exchange in insects
- insects have microscopic air-filled pipes called trachea which they use for gas exchange
- air moves into the tracheae through pores on the surface called spiracles
- oxygen travels down the concentration gradient towards the cells
- the trachea branch off into smaller tracheoles which have thin, permeable walls and go to individual cells. this means that oxygen diffuses directly into the respiring cells (the insect’s circulatory system doesnt transport O2)
- carbon dioxide from the cells moves down it own concentration gradient towards the spiracles to be released into the atomosphere
- insects use rythmic abdominal movements to move air in and out of the spiracles
exchanging gases causes water loss.
how is water loss reduced in insects?
- insects use muscles to close spiracles if they are losing too much water
- they have a waterproof waxy cuticle all over their body and tiny hairs around their spiracles, both of which reduce evaporation
discuss the strucure of the gill and how this helps with the counter-current system
oxygen hasa lower concentration in water than in air
- oxygen containing water enters through the mouth and exits through the gills
- each gill contains ‘thin plates’ or ‘gill filaments’
- gill filaments are covered in lots of tiny structures called lamaellae, which increase the surface area even more
- the lamellae have lots of blood capillaries and a thin surface layer of cells to speed up diffusion
counter current system:
- this is where water flows over the gill lamellae in the opposite direction to the fish blood flow
- this helps to maintaine a favourable concentration gradient across the whole length of the gill lamellae (entire exchange surface)
- the concentration of oxygen of water is always higher than that in the blood, so as much oxygen as possible diffuses from the water into the blood
describe the counter current system
counter current system:
- this is where water flows over the fill lamella in the opposite direction to the fish blood flow
- this helps to maintaina diffusion gradient across the whole length of the gill lamellae
- the concentration of oxygen of water is always higher than that in the blood, so as much oxygen as possible diffuses from the water into the blood
describe ventilation and circulation in a fish
- the constant movement of water through the mouth and over the gills (ventilation) helps to replace water low in O2 with water higher in O2
- at the cells; circulation of blood helps to replace blood that is low in O2 with blood saturated with O2
the volume of water assing over the gilss increases if the temperature of the water increases. suggest why.
at higher temperatures the ezymes work faster
- so there is a higher rate of metabolic reactions such as respiration
- these reactions require more oxygen from the water so more water is needed to be transferred replace water low in oxygen
a fish uses gills to absorb oxygen from water, explain how the gills of a fish are adapted for efficient gas exchange
- gill filaments and lamallae speed up diffusion by providing large surface area
- the lamallae have lots of capillaries and thin surface area of cells which provide a short diffusion pathway
- a concentration gradient is maintained across the whole length of the gill as water flows over the gill lamellae in the direction opposite to the flow of the fish blood. this is the counter current system.
label the parts of this leaf
A= palisade mesophyll cell
B= xylem and phloem
C= spongy mesophyll cells
D= waxy cuticle
E= lower epidermis cells
F= guard cell
G= stoma
H= upper epidermis cell
I= waxy cuticle
in what ways is gas exchange in plants is similar to thay of insects?
- no living cell is far from the external air, and therefore a source of oxgen and carbon dioxide
- diffusion takes place in the gas phase (air), which makes it more rapid then if it were in water
what are the adaptations plants have for rapid diffusion?
- many small pores, called stomata and so no cell is far from a stoma and therefore the diffusion pathway is short
- many interconnecting air-spaces that occur throughout the mesophyll so that gases can readily come in contact with mesophyll cells
- large surface are of mesophyll cells for rapid diffusion
why do plants not have a large surface area to volume ratio?
because they photosynthesise, and photosynthesis requires a large leaf surface area for the capture of light and for the exchange of gases
what are xerophytes plants?
plants that are adapted to living in areas where water is in short supply
what are adaptations xerophyte plants have to reduce water loss?
- a thick waxy cuticle: waxy cuticle forms a waterproof barrier, it reduces evaporation, the thicker the cuticle the less water can escape.
- curles/rolling up of leaves: the rolling of leaves protects the lower epidermis from the outside and helps to trap a region of still air within the rolled leaf. This region becomes saturated with water vapour and so has a very high water potential, there is no water potential gradient betweent he inside and outside of the leaf and therefore no water loss. also protects from wind
- sunken stomata surrounded by hairs: traps still mosit air next to the leaf and reduce the water potential gradient
- reduced stomata: few pores for water to escape
Insects and plants face the same problems when it comes to living on land. what is the main problem they share?
efficient gas change requires a thin, permeable surface with large area.
On land these features can lead to consdierable loss of water by evaporation
plants such as marram grass roll up their leaves, with the lower epidermis on the inside, to reduce water loss
why would rolling the lead the other way (with the upper epidermis on the inside) not be effective in reducing water loss?
- almost all stomata are on the lower epidermis
- this would be exposed to air currents that would reduce the water potential outside the leaf
- the water potential gradient would be increased and a lot of water vapout would be lost
*label this diagram showing the gas exchange system and describe the function of these organs in the system*
*diagram in cgp books*
- ) as you breathe in, air enters the trachea (windpipe)
- ) the trachea splits into two bronchi- one brochus lead to each lung
- ) Each bronchus then branches off into smaller tubes called bronchioles
- ) the bronchioles ened in small ‘air sacs’ called alveoli (this is where gas is exchanged)
- ) the ribcage, intercostal muscles and diaphragm all work together to move air in and out
what are the lungs?
they are a pair of lobed structures made up of a series of highly branched tubes, called bronchioles, which end in tiny air sacs called alveoli
what is the trachea and what does it do?
a flexible airway that is supported by rings of cartilage
the cartialge prevents the trachea from collapsing as the air pressure inside falls when breathing in.
the trachea walls are made up of muscles, lined with cilliated epithelium and goblet cells
what are the bronchioles and what do they do?
they are a series of branching subdivisions of the bronchi
their walls are made of muscle lined with epithelial cells
this muscle allows them to constrict so that they can control the flow of air in and out of the alveoli
what are the bronchi and what do they do?
the bronchi are two divisions of the trache each leading to the lung
like the trachea they produce mucus to trap dirt and have cillia that move dirt-laden mucus towards the throat
the larger bronchi are supported by cartilage
what are alveoli and what do they do?
they are minute air-sacs, with a diamete of between 100-300 nanometers at the end of the bronchioles
- between the alveoli there are some collagen and elastic fibres which allow the alveoli to stretch as they fill with air when breakthing air and then spring back to expel CO2 rich air
- the alveoli are lined with epithelium (thin tissue)
- the alveolar membrane is the gas-exchange surface
state two reasons why humans need to absorb large volumes of oxygen from the lungs
humans are large so have a large volume of cells
humans aloso have a high metabolic rate
explain how the cells lining the trachea and bronchus protect the alveoli from damage
the dirt/bacteria could damage and cause infection in the alveoli
so the cells produce mucus that traps particles of dirt and bacteria in the air breathed in
the cillia on these cells move this debris up the trachea and into the stomach
what is ventilation?
where air is constantly moved in and out of the lungs to maintain diffusion of gases across the alveolar epithelium
what is inspiration (inhalation)?
the air pressure of the atomosphere is greater than the air pressure inside the lungs so air is forced into the lungs
what is expiration?
when the air pressure in the lungs is greater than that of the atomosphere so air is forced out of the lungs
what are three set of muscles that move to change pressure within the lungs?
the diaphragm: sheet of muscle that seperates the thorax from the abdomen
the intercostal muscles: which lie between the ribs
- internal intercostal muscles whose contaction leads to expiration
- external intercostal muscles whose contractions lead to inspiration
what does the diaphragm during inspiration?
the diaphragm contracts, pulls down which causes it to flatten
this enlarges the thoraic cavity increasin the volume of the thorax
what does the diaphragm do in expiration?
the diaphragm relaxes and so it is pushed up again by the contents of the adbomen, returning to its dome shape
the volume of the thorax is further decreased
what do the external intercostal muscles do during inspiration?
during inspiration the external intercostal muscles contract and lift the ribs up and outwards
what do the internal intercostal muscles do during expiration?
during expiration the internal intercostal muscles contract and pull the ribs downwards and inwards
what are antagonistic muscles
these are muscle pairs that work opposite to each other
why is gas exchange vital?
- provide oxygen for repiration
- it allows waste CO2 to be expelled
- CO2 lowers the pH of cells and blood plasma (normally pH 7-4) which could cause problems such as denaturing
what happens during inhalation?
breathing in is an active process (it uses energy) and occurs as follows:
- the external intercostal and diaphragm muscles contract whilst the internal intercostal muscles relax
- this causes the ribcage to move upwards and outwards and the diaphragm to flatten, increasing the volume of the thoracic cavity (the space where the lungs are)
- as the volume of the thoracic cavity increases, the lung pressure decreases (to below atomosphere pressure)
- amospheric pressure is now greater than pulmonary pressure so air moves down the concentration gradient. It flows down the trachea and into the lungs
what happends during expiration?
breathing in is an passive process (it doesnt require much energy) and occurs as follows:
- the internal intercostal and contract whilst the external intercostal muscles and diaphragm relax
- this causes the ribcage to move downwards and inwards and the diaphragm to become curved, reducing the volume of the thoracic cavity (the space where the lungs are)
- as the volume of the thoracic cavity decreases, the lung pressure increases (to above atomosphere pressure)
- amospheric pressure is now less than pulmonary pressure so air moves down the concentration gradient and is forced out of the lungs
what happesn during forced expiration?
the external intercostal muscles relax and internal intercostal muscles contract, pulling the ribcage down and in
-during this time, the movemnt of the two sets of the intercostal muscles is said to be antagonisitic (opposing)
where is the site of gas exchange in mammals?
in the epithelium of the alveoli (surface membrane of the alveoli)
whar are the 3 things that the alveoli epithelium needs to have for efficient diffusion?
- ) large surface area compared to its volume
- ) A short diffusion distance for the gas to diffuse
3,) a large difference in the concentration of gas on the opposite side of the surface
what are the adapations of the alveoli for effficient gas exchange?
- a thin surface: the alveolar epithelium are only one cell thick which means theres a short diffusion pathway
- a large surface are: the large number of alveoli means theres a large surface area for gas exchange
- inner surface of the alveoli is covered in a thin film of water: the water is essential to allow oxygen to dissolce in it and pass into the blood
how does O2 get into the blood from the alveoli?
- the alveoli are surrounded by a network of capillaries
- O2 diffuses out of the alveoli, accross the aveoli epithelium and the capillary endothelium (a type of epithelium that forms the capillary wall) and into haemoglobin in the blood
- CO2 diffuses into the alveoli from the blood is breathed out
summary of gas exchange
oxygen from the air moves down the trachea, bronchi and bronhioles into the allveoli (this movement happends down the pressure gradient)
Once in the alveoli the oxygen diffuses across the alveolar epithelium, the capillary endothelium ending up in thecapillary itself. (this movement happens down a diffusion gradient)
how is a concentration maintained
it maintained by ventilation and bood circulation
- ventilation ensure the alveoli have a high conc of O2
- blood circulation removes red blood cells with a high conc O2 and replaces them with red blood cells with a low O2 conc
how do infections such as pneumonia affect gas exchange?
they cause the layer of water on the alveoli wall to get thicker so diffusion of O2 is slower and decreased, serisouly hindering gas exchange
a mountain climber is climbing at altitude, where theres less oxygen
suggest how this will affect gas exchange in the alveoli
-gradient of oxygen between the capillaries will be less steep slowing the rate of diffusion
what lung disease affect?
ventilation
gas exchange
what is the tidal volume?
what is the healthy range?
volume of air in each breath at rest
healthy range: 0.4dm3 - 0.5dm3
what is meant by the ventilation rate?
what is the healthy range?
number of breaths per minute
15 breaths per minute
what is meant by the forced expiration volume (FEV)?
max volume of air breathed out in 1 second
what is meant by the forced tidal capacity (FTC)
the max volume of air that’s forcefully breathed out after a really deep breath in
what is the pulmonary ventilation and what is the eqaution for working it out?
state the units
this is the total volume of air moved in and out of the lungs in one minute
pulmonary ventilation = tidal volume x ventilation rate
pulmary ventilation= (dm3 min-1)
tidal volume= dm3
Ventilation rate= min-1
what is a spirometer?
a machine that scientist and doctors use to measure the volume of air breatherd in and out
Name the parts of this graph
A= deep breath in
B= tidal volume of normal breath
C=deep breath out
D=residual air can’t be expelled
discuss how emphysema is caused, the symptoms and how it affects lung function
emphysema
causes: smoking, long term exposure to air pollution - where the foreign particles in the smoke (or air) become trapped in alveoli
symptoms: shortness of breath, wheezing, increased ventilation rate to try and increase the amount of air in the lungs
how it affects lung function:
- the trapped particles in the alveoli cause inflammation, which attracts phagocytes,
- the phagocytes produce an enzyme that breaks elastin (protein in the walls of the alveoli)
- elastin is elasti, helps the allveoli to return their normal shape after inhaling and exhaling air
- loss of elastin means the alveoli cant recoil to expel air as well and can lead to the destruction of the alveoli walls which reduce surface area so rate of gaseous exchange decreases
discuss how asthma is caused, the symptoms and how it affects lung function
Cause: asthma is a respiratory condition where the airways become inflame and irritated, caused by allergic reactions to substances such as pollen and dust
symptoms: wheezing, tight chest, shortness of breath
how it affects lung function:
- during an asthma attack, the smooth muscle lining the bronchioles contracts and a large amount of mucus is produced
- this constritcs the airways making it difficult to breathe
- air flow in and out of the lungs is severly reduced, so less oxygen enters the alveoli and moves into the blood. reduced airflow means that FEV1 is severely reduced
discuss how pulmonary tuberculosis (TB) is caused, the symptoms and how it affects lung function
causes: infection from tuberculosis bacteria, exposure to substances like dust, asbestos
symptoms: persistent cough, coughing blood and mucus, chest pains, shortness of breath fatigue
how it affects lung function:
when someone becomes infected with tuberculosis bacteria, the immune system build a wall around the bacteria in the lungs which forms small, hard lumps known as tubercles
- infected tissure with the tubercles dies and the gaseous exchange surface is damaged so tidal volume is decreases
- a reduced tidal volume means less air can be inhaled with each breath, in order to take in enough oxygen patients have to breathe faster i.e ventilation rate is increased
discuss how fibrosis is caused, the symptoms and how it affects lung function
fibrosis is the formation of scar tissue in the lungs
cause: infection, exposure to substances like asbestos or dust
symptoms: dey cough, chest pain, fatigue, weakness, shortness of breath (faster ventilation rate than normal to get enough air into lungs to oxygenate their blood)
how it affects lung function:
- scar tissue (tissue formed when the tissue before was damaged) is thicker and less elastic than normal lung tissue
- this means that the lungs are less able to expan and so cant hold as much air as normal so tidal volume is reduced and so is FVC
- there is a reduction in the rate of gaseous exchange- diffusion is slower across a thicker scarred membrane
answer this question
interpreting lung disease data
interpreting lung disease graphs
answer theses questions on lung disease data
label the parts of the digestive system
A= tongue
B= salivary glands
C= oesophagus
E= lobe of liver
F= transverse limb of large intestine
G= ascending limb of large intesting (colon)
H= stomach
I= pancreas
J= descending limb of the large intestine (colon)
K= small intestine (ileum)
L= rectum
M= anus
what is the reversible eqaution for the loading and unloading of haemoglobin?
describe the s (sigma) shape curve on this oxygen dissociation graph
talk about the point:
0%
low pO2
high pO2
- almost max saturation
- 100% saturation
- when the curve is steep
- there is 0% saturation as non of the haemoglobin molecules are carrying oxygen
- where pO2 is low haemoglobin has a low affinity for oxygen which means it releases oxygen rather than combining with it, thats why it has a low saturation of oxygen near the start
- where pO2 is high haemoglobin has a high affinity for O2 (it will readily combine with oxygen so it has a high saturation of oxygen)
this is because as the first O2 molecule binds to the haemoglobin, it alters the shape making it easier for other O2 to bind (the steep part in the middle)
- As haemoglobin becomes more saturated it gets harder for more O2 molecules to bind
- 100% saturation means every haemoglobin molecule is carrying 4 molecules of O2
- when the curve is steep, it shows that a small change in pO2 causes a big change in the amount of O2 carried by haemoglobin
explain the bohr effect
the bohr effects is the reduction in affinity of haemoglobin for O2 as CO2 increases
- ) when cells respire they produce carbon dioxide which raises the pCO2
- ) this increases the rate of oxygen unloading (the rate at which oxyhaemoglobin dissociates to form haemoglobin and oxygen)
so the dissociation cuve shifts to the right (as there is a higher pCO2)
3.) the saturation of blood with O2 is lower for a given pO2 meaning more oxygen is being released
CO2 also lowers the pH which changes the shape of haemoglobin (protein) so it gives up O2 more readily at a higher pCO2
Heat from respiration helps mammals to maintain a constant body temperature. Use this information to explain the relationship between surface area to volume ration of mammals and the oxygen dissociation curves of their heamoglobin
- ) smaller mammals have a larger surface area to volume ratio
- ) so they will lose heat faster
- ) therefore they will require more oxygen to maintain a high rate of respiration for heat
- ) a right-shifted curve means haemoglobin will dissociate more readily at higher partial pressure of oxygen.
label the parts of this heart
A= left pulmonary artery
B= right pulmonary artery
C= pulmonary trunk
D= superior vena cava
E= right atrium
F= right AV valve
G= pulmonay semilunar valve
H= right ventricle
I= inferior vena cava
J= aortic arch
K= aorta
L= left pulmonary veins
M= right pulmonary veins
N= left atrium
O= left AV valve
P= aortic semilunar valve
Q= left ventricle
R= septum
S= descending aorta
graph that represnts the cardiac cycle
EQ: Use your knowledge of transpiration to explain the changes in the rate of flow in the xylem shown in the graph.
3 marks
Explain why the values for the pressure in the xylem are negative.
1 mark
- Stomata open;
- Transpiration highest around midday;
]3. Middle of day warmer / lighter;
- (Increased) tension / water potential gradient;
- Cohesion (between water molecules);
- Pressure in xylem is lower than atmospheric pressure
EQ: Use the information provided to explain the effect that glycaemic load of the diet has on the risk of developing CHD.
2 mark
- For diet group 2 and above, increase in risk of CHD as GL increases;
- (Higher GL diets lead to) more (harmful) lipids (in blood), so greater risk of atheroma;
- Atheroma leads to blockage of coronary artery / increased risk of blood clot in coronary artery;
