topic three Flashcards
what does an organisms surface area affect
how quickly it exchanges substances
do smaller organisms have a higher or lower SA:V ratio
higher
what do organisms need to supply each cell with
glucose and oxygen
what do organisms need to remove from every cell
waste products
diffusion in single celled organisms
- substances diffuse in/out across membranes
- diffusion rate is quick
diffusion in multi cellular organisms
- diffusion across the membrane would be too slow, due to the distance or the fact that larger animals have a larger surface are to volume ratio
- as a result, they need specialised systems
features of an efficient gas exchange surface
- large sa
- thin, to ensure a short diffusion distance
- good blood supply/ventilation to maintain a steep gradient.
why do fish have an impermeable membrane
so gases cant diffuse through their skin
bony fish gas exchange
- 4 pairs of gills
- each gill supported by an arch
- arches have gill filaments
filaments have lamellae - blood and water flow across lamellae in counter current direction
what is counter current
blood and water flow in opposite directions to each other
why is ventilation required
to maintain a continuous unidirectional flow
how does ventilation work in fish
- fish opens its mouth
- lowering the floor of the buccal cavity
- this enables water to flow in
- fish closes its mouth
- buccal cavity raises
- this increases the pressure
- water forced over gill filaments, by difference in mouth cavity and opercular cavity.
- operculum acts as a valve and pump
why do insects need oxygen to be transported directly to tissues
insects do not possess a transport system
tracheal system of a insect
- spiracles (small openings of tubes)
- trachea
- tracheoles
what is mass transport a result of
muscle contraction
what occurs in the tracheoles
volume changes
what is the function of stomata
allow gases to enter and exit the leaves
why is there a large number of stomata
reduces diffusion distances as there is stoma near all cells
gas exchange pathway in humans
- mouth/nasal cavity
- trachea
- bronchi
-bronchioles - alveoli
inspiration
- diaphragm contracts and flattens
- external intercostal muscles contract
- internal intercostal muscles relax
- ribcage moves up and out
- increase in cavity vol
- decrease in pulmonary pressure
= atmospheric p > pulmonary p
= air forced into the lungs
expiration
- diaphragm relaxes
- external intercostal muscles relax
- internal intercostal muscles contract
- ribcage moves down and in
- decrease in cavity vol
- increase in pulmonary pressure
= atmospheric p < pulmonary p
= air forced out the lungs
what are the airways held open with
rings of cartilage
structure of trachea and bronchioles
- composed of several layers which make up a thick wall
- the wall is composed of cartilage rings
- inside surface of cartilage is a layer of ‘loose tissue’
- the inner lining is an epithelial layer composed of ciliiated epithelium and goblet cells.
alveoli structure and function
- one cell thick = short diffusion distance
- constant supply by capillaries = maintains a steep concentration gradient
- a large number of alveoli = large SA
what is a spirometer used for
to measure lung volume
how does someone use a spirometer
- breathe in and out of the airtight chamber
- this causes it to move up and down, which leaves a trace on a graph
what is vital capacity
the max. volume of air that can be inhaled or exhaled in a single breath
what is tidal volume
the volume of air breathed in and out at each breath at rest
what is breathing rate
number of breaths per min.
what is residual volume
the volume of air that is always present in the lungs.
what is digestion
the hydrolysis of large biological molecules which can be absorbed across membranes
what enzymes digest carbohydrates
- amylase in mouth digests larger polymers
- maltases in ileum digest monosaccharides
- sucrases and lactases break down disaccharides, sucrose and lactose.
what enzyme break down lipids
lipase hydrolyses ester bonds between the monoglyceride and fatty acids
how are lipids broken down
emulsified into micelles by bile salts released in the liver.
what does emulsification increase
surface area, also speeds up reaction
what enzyme digests proteins
peptidases
what do endopeptidases hydrolyse
hydrolyse peptide bonds between specific amino acids in the middle of a polypeptide
what do exopeptidases do
hydrolyses bonds at the ends of polypeptides
what do dipeptidases do
break dipeptides into amino acids
where are products of digestion absorbed
cells lining the ileum
what process is used to absorb products
facilitated diffusion and co transport
what makes monoglycerides and fatty acids able to easily diffuse aross membranes
they are polar
what is haemoglobin
a water soluble globular protein
what does haemoglobin consist of
two beta polypeptide chains and two alpha helices
what does each molecule of haemoglobin form
a complex containing a haem group
what is the function of haemoglobin
- attaches to red blood cells
- oxygen binds to the haem group and it carries oxygen around in the blood
how many oxygen molecules can haemoglobin carry
4
what does the affinity of oxygen depend on
the partial pressure (which is a measure of oxygen concentration)
a type of pressure
what decreases during respiration
partial pressure, since oxygen is used up. this decreases oxygen’s affinity to haemoglobin.
in terms of oxygen and haemoglobin
what happens as a result of respiration
- oxygen is released into respiring cells
- haemoglobin returns to the lungs after unloading, and binds to oxygen again
what do dissociation curves show
the change in haemoglobin saturation, as partial pressure changes.
what is haemoglobin saturation affected by
its affinity for oxygen,
- high partial pressure = high affinity = high saturation
why is fetal affinity different to adult affinity
it needs to be better at absorbing oxygen because by the time oxygen has reached the placenta, the saturation of the blood has decreased.
therefore it has to have a high affinity to survive at a low partial pressure.
what else (other than o2) is the affinity affected by
the partial pressure of co2.
what happens to the affinity of oxygen in the presence of carbon dioxideand what is this called
- carbon dioxide is released by respiring cells
- therefore, affinity of haemoglobin for oxygen decreases.
THIS IS CALLED THE BOHR SHIFT
why do mammals need a circulatory system
the SA:V isnt large enough for diffusion alone to supply substances like oxygen, glucose and other substances.
common features of a circulatory system
- suitable medium, water based so its easier for substances to dissolve
- means of moving the medium, heart maintains pressure of the medium
- mechanism to control the flow of blood, valves are used to prevent the back flow of blood
- close system of vessels, closed and branched to deliver substances to rest of the body
what does it mean by a closed double circulatory system
- the heart at the centre, with two pumps
- one pumps blood to lungs, to be oxygenated
- the other pumps oxygenated blood around the body
atrium structure
- thin, elastic walls, needs to stretch to be filled with blood
ventricle structure
- thick muscular walls to pump blood around the body/to lungs
why are two separate pumps needed
to maintain pressure around the WHOLE body
aorta function
- connected to the left ventricle
- carries oxygenated blood to everywhere except the lungs
pulmonary artery function
- connected to the right ventricle
- carries de-oxygenated blood to the lungs where it is oxygenated and co2 is removed
pulmonary vein function
- connected to the left atrium
- brings oxygenated blood back to the heart, from the lungs
vena cava function
- connected to the right atrium
- brings de-oxygenated blood back from tissues (except lungs)
what are the three stages of the cardiac cycle
- cardiac diastole
- atrial systole
- ventricular systole
what happens at cardiac diastole
- atria and ventricles relax
- elastic recoil of the heart lowers the pressure inside chambers
- blood fills atria
- pressure in atria increases until AV valves open
- blood flows into ventricles
- SL valves close
what happens at atrial systole
- atria contract
- this forces remaining blood into the ventricles
what happens at ventricular systole
- ventricles contract
- AV valves close
- SL valves open, which allows blood to leave the left and right ventricles.
structure and function of arteries
- carry blood away from the heart to the rest of the body
- thick walled to withstand high pressures
- contain elastic tissue to allow them to stretch and recoil which makes blood flow smoother
- lined with smooth endothelium to reduce friction and ease flow of blood
structure and function of arterioles
- branched off of arteries
- have thinner and less muscular walls
- role is to feed blood into capillaries
structure and function of capillaries
- smallest vessels
- site of metabolic exchange
- one cell thick for fast exchange
structure and function of venules
- larger than capillaries but smaller than veins
- receive blood from capillaries
structure and function of veins
- carry blood from body to the heart
- wide lumen to maximise volume of blood carried to the heart
- thin walled due to low pressure
- contain valves to prevent the back-flow of blood
no elastic tissue as there is no need for stretching/recoiling
what does tissue fluid contain/what is it made from
dissolved oxygen and nutrients
what does tissue fluid do
- supplies the tissues with essential solutes in exchange for waste products such as co2
how is hydrostatic pressure created
- when blood is pumped along the arteries, into arterioles and then capillaries
what substances are components of the tissue fluid ( and examples)
- only substances small enough to pass through the capillary gap
- amino acids, ions in solutions, glucose and oxygen
what does high hydrostatic pressure do
- forces blood out of the capillaries
- some also pushed back into the capillaries
why do the tissue fluid and blood have negative water potential
they both contain solutes
which, between blood and tissue fluid, contains more solutes and what does this cause
- blood contains more solutes
= tissue fluid more positive - causes water to move down the water potential gradient from tissue fluid to blood by osmosis
where is remaining tissue fluid pushed (which isnt pushed back )
- carried back via lymphatic system
what fluid does the lymphatic system contain
- lymph fluid
- lymph nodes
contents of lymph fluid
- less oxygen and nutrients than tissue fluid
purpose of lymph fluid
- carries waste products
purpose of lymph nodes
- filters out bacteria and foreign material with the help of lymphocytes (which destroy pathogens)
why do plants require a transport system
to ensure that all cells of a plant receive a sufficient amount of nutrients
what does the xylem tissue do
enables water and dissolved minerals to travel up the plant through transpiration
what does the phloem tissue do
enables sugars to reach all parts of the plants through translocation
xylem and phloem are apart of the vascular bundle which does what?
enable transport of substances as well as providing structural support
features of xylem
- long,dead cylinders with open ends which means they can form a continuous column
- contain pits which enable water to move sideways between vessels
- thickened with lignin which is deposited in spiral patterns to enable the plant to remain flexible
what is transpiration
- process where plants absorb water through the roots
- moves up through the plant and is released as water vapour through stomata.
- co2 enters while water and oxygen exit
what is the transpiration stream and what does it enable
- movement of water up the stem
- enables processes such as photosynthesis, growth and elongation as it supplies plant with water for these processes
- also supplies plant with minerals
what processes does transpiration involve
osmosis AND evaporation
where does water move from and to in the plant
from the xylem, to the mesophyll cells
what happens at the mesophyll cells during evaporation
evaporates from surface into intercellular spaces
diffusion of water vapour down a water vapour potential gradient out of stomata.
what apparatus investgates the rate of transpiration
a potometer
factors that can affect the rate of transpiration
- number of leaves
- number/size of stomata
- presence of a waxy cuticle
- light
- temperature
- humidity
- air movement
- water availability
what are xerophytes
plants adapted to living in dry conditions, such as cacti
adaptations of xerophytes
- smaller leaves to reduce SA for water loss
- thick waxy cuticle to prevent water loss via evaporation
- contain hairs and pits which trap water vapour
- roll leaves to reduce exposure of lower epidermis, trapping air that is moist
where does the water enter through and where does it move and how
root hair cells, moves into xylem, occurs as a result of higher water potential inside the soil than in the root hair cell.
what does the root hair cell do
- provides a larger SA for movement of water to occur
- minerals absorbed through root hair cell by AT
what are the two ways water can be taken up by root hair cells
- symplast pathway
- apoplast pathway
what is the symplast pathway
- water enters cytoplasm through plasma membrane
- passes from one cell to the next through plasmodesmata
- these are channels which connect the cytoplasm of one cell to the next
what is the apoplast pathway
- water moves through water filled spaces between cellulose molecules in cell walls
- water doesn’t pass through any plasma membrane therefore it can carry dissolved mineral ions and salts
what is the cohesion tension theory
- water molecules form hydrogen bonds with each other causing them to stick together (cohesion)
- surface tension of the water creates the sticking effect
- therefore as water is lost through transpiration , more can be drawn up the stem from the roots
what is translocation
transport of assmiliates from the source to the sink which requires ATP
phloem stucture and function
- living cells
- consist of sieve tube elements and companion cells
- cytoplasm of sieve tube and companion cells are linked through plasmodesmata which are gaps between cell walls which allow communication and flow of substances such as minerals between cells
what do sieve tube elements do
form a tube to transport sugars such as sucrose in the dissolved form of sap
what do companion cells do
involved in ATP production for active processes such as loading sucrose into sieve tubes
process of translocation
- sucrose enters phloem in process called active loading.
- facilitated diffusion allows the return of hydrogen ions to bring sucrose molecules into companion cells, which causes conc. of sucrose in companion cells to increase
- sucrose diffuses out of companion cells down the conc. gradient into the sieve tube elemnts through plasmodesmata
- as sucrose enters sieve tube, water potential inside tube to reduced. this causes water to move in by osmosis from xylem, which increases hydrostatic pressure
- water moves dow tube, from a high hydrostatic pressure to a low hydrostatic pressure
- sucrose is removed from sieve tube elements by diffusion or AT into surrounding cells, increasing water potential in sieve tube. this in turn means water leaves by osmosis back into xylem. as a result, this reduces pressure in phloem at sink
what is active loading
- companion cells use ATP to transport hydrogen ions into the surrounding tissue, thus creating a diffusion gradient, which causes the hydrogen ions to diffuse back into the companion cells
evidence for mass transport
- pressure in sieve tube elements, shown by sap being released when stem of plant is cut
- conc. of sucrose is higher in source han in the sink
evidence against mass transport
- function of sieve plates is unclear as they would appear to hinder mass flow
- not all solutes moves at the same speed, should do if its mass flow
