topic 3 (exchange of substances) Flashcards
(95 cards)
1
Q
how is gas exhanged in single celled organisms
A
they have a large surface area to volume ratio.this means they are able to diffuse oxygen/carbon dioxide in and out through the cell membrane.
2
Q
describe an insects internal network?
A
trachea are small pipes that the insect has around its body. these lead into smaller pipes which actually transfer gas to the tissue called tracheoles. the trachea is supported by rings.
3
Q
describe the three way gas is transferred via the trachea network?
A
diffusion gradient
mass transport-muscles contract forcing air out and in trachea
muscle cells around tracheoles, respire anaerobically which produces lactate lowering its water potential. water moves from the tracheoles to these cells (osmosis).Tracheoles have less water so now they have space for more air. this makes the last step of diffusion quicker as it is a gas not a liquid. however this leads to more evaporation
4
Q
how is diffusion gradient established in an insect
A
after respiration their is a low conc for o2 in the end of the tracheoles and high o2 in the air. this causes a diffusion pathway
5
Q
how is mass transport used to increase diffusion
A
the insect muscle squeezes the trachea enabling mass movement of air in&out speeding up exchange of respiratory
6
Q
how does gas enter the insect
A
it comes in through spiracles that can be controlled by spiracle valves .these are mostly shut to avoid water loss via evaporation
7
Q
what are the limitations of an insects gas exchange system?
A
It relies only on diffusion.
because of the small diffusion pathways insects cant grow big
8
Q
how do fish diffuse in oxygen?
A
water is forced in through the mouth taken over the gills and out via the side opening
9
Q
what is countercurrent flow?
A
when blood and water flow over the lamellae in opposite directions.
blood that is high in o2 meets water which has maximum concentration of o2.diffusion takes place of o2 from water to blood.
blood with little o2 meets water with low conc of o2. diffusion of o2 from water to blood.
this allows the diffusion gradient to be maintained across lamellae. this allows for 80% of o2 available in the water is absorbed by the blood instead of 50%
10
Q
explain the structure of the gills
A
gills are made of gill fillaments .at right angles to the fillaments are the lamellae . these increase surface area
11
Q
for plants where does most gaseous exchange occur and how is it adapted?
A
most gaseous exchange happens in the leaf the adaptations include:
many stomata which means no cell is far away from it.therefore their is short diffusion pathway
lots of air spaces that allow the gas to come in contact with mesophyll cell
large surface area of mesophyll cells for quicker diffusion
12
Q
explain the structure of the stomata?
A
plants have stomata mainly on the underside of the leaf.the stomata cannot always due to water loss. so the stomatal pore is controlled by the guard cells.
13
Q
explain the structure of the stomata?
A
plants have stomata mainly on the underside of the leaf.the stomata cannot always due to water loss. so the stomatal pore is controlled by the guard cells.
14
Q
describe the structure of the leaf?
A
waxy cuticle upper epperdermis palisade mesophyll mesophyll spongy mesophyll lower epperdermis stomata/guard cells waxy cuticle
15
Q
how do insects control water loss?
A
spiracles that can be closed
the insects outer skeleton of chitin is covered with waterproof cuticle
small surface area to volume ratio
16
Q
what are plants called that are adapted to lack of water and how do they do this?
A
these plants are called xerophytes
thicker cuticles means less water can escape
curled leafs -
hairy leafs - traps air saturated in watervapour .which has a high water potential reducing the gradient
low sa to vol ratio - plants have smaller circular leaves
stomata in pits grooves this traps moist still air reducing the diffusion gradient
17
Q
how does curling the leaf release water loss?
A
the leaf curls protecting the lower eppermerdis.it also traps some air the air is saturated in water vapour therefore it is high in water potential their is no diffusion gradient and therefore water is not loss.
this is common in marram grass
18
Q
how do plants control water loss?
A
plants require o2 for photosynthesis so they cannot have a small sa to vol ratio. instead they control it by a waxy layer aswell as controlling when to open anf close stomata
19
Q
why do humans require a lot of oxygen?
A
they are a large organsims and have a lot of cells
they need to maintain a high body temperature which is related to high metabolic and respiratory rates
20
Q
why are lungs stored inside the body?
A
they would dry out due to water loss
the air is not dense enough to support their structure
21
Q
describe the trachea?
A
it is made of cartilage rings to withstand the pressure. it has cilliated epithilium which trap any bacteria or dirt particles and force it back up the throat.
it also has goblet cells which produce mucus.
22
Q
explain how air passes into the alveoli?
A
it travels down a pressure gradient from trachea to bronchi to bonchioles to alveoli
it then travels out the alveoli across the alveolar epitheliam across capillary epitheliam via diffusion
23
Q
describe the bronchi?
A
they also have cillia which trap any dirt particles and force them back up trachea
the cartilage depends on how big the bronchi is. the bigger the more cartilage
24
Q
describe the bronchioles?
A
the wall are made of muscles with epithilal cells .the muscles can constrict to control the amount of air allowed in and out of the alveoli
25
describe the structure of the alveoli?
in between the alveoli is collagen and elastic fibres. the alveoli are lined with epithilial cells. the elastic fibres allows it fill with o2 and spring back to release the co2. the gas exchange surface is the alveolus membrane.
around each albeolus is a network of pulimonary capillaries(one cell thick)
26
what is ventilation?
air constantly moving in and out of the lungs to maintain a diffusion gradient
27
what is inspiration and expiration?
inspiration (inhalation)when the air pressure inside the lungs is less than the air pressure outside
expiration (exhalation) when the air pressure is greater inside the lungs than outside
28
where the muscles inolved the lungs based of?
the diaphragm between thorax (chest) and abdomen
the internal intercostal muscles responsible for exhalation
the external intercostal muscles responsible for inhalation
the intercostal muscles are located between the ribcage and lungs
29
how does inspiration occur?
the external intercostal muscles contract while the internal intercostal muscles relax.
the ribs moves up and outside increasing the volume of the thorax
the diaphragm contracts flattening it also increasing the volume of the thorax
the increase of volume means the pulomonary pressure is lower than atmospheric pressure
this causes the air to move into the lungs
30
how does expiration occur?
the internal intercostal muscles contract while the external intercostal muscles relax
the ribs relax moving it inwards and downwards decreasing the volume of the thorax
the diaphragm relaxes pushing it against the abdomen further decreasing the volume of the thorax
the decrease in volume causes the pressure to increase
the pulmonary pressure is now greater than atmospheric pressure forcing air out
31
hoe does a asthma attack occur?
muscles of bronchi/bronchiole contract
more mucus is produced
this narrows the air pathway
allowing less air through and increase breathing rate
32
what is the different in passive /regular breathing?
in passive breathing not all the muscles are used instead it is based on the recoil of the elastic fibres in the lungs /alveolis
33
what is pulmonary ventilationrate and what is the equation for it?
pulmonary ventilation is the volume of air released from the air in 1 min.(dm3/min-1)
tidal volume is the volume of air taken in each breath
pulmonary ventilation= tidal volume x breathing rate
dm3/min-1 dm3 min-1
34
explain chemical digestion
the food is hydrolysed from insolouble large pieces to solouble large pieces.this occurs via enzymes and water
35
why is diffusion between capillaries and alveoli so rapid
red blood cells are slowed to allow more time
large surface area of alveoli and capillaries
the capilarries are one cell thick (short diffusion pathway)
ventilation ensures a steep concentration gradient
blood pumping through capillaries around the body maintains concentration gradient
36
what are the 2 stages of digestion?
physical digestion
| chemical digestion
37
explain physical digestion and its benefits?
food is broken down into smaller pieces by the teeth and the stomach making it possible to ingest food and increases the surface area for chemical digestion.
38
in depth describe how carbohydrates are digested?
saliva in the mouth releases salivary amylase while chewing it breaks down some of the starch to
maltose.the pH is maintained by mineral salts
This enzyme works at neutral ph. The acidic stomach denatures it.at the small intestine the pancreas releases pancreatic amylase which hydrolyses all the starch to maltose.alkaline salts from pancreas and intestine wall keep ph neurtral
next at the illeum epithilal cells release membrane bound maltase further hydrolyses it to glucose a.
39
what are the envolved in breaking down carbohydrates?
amylase is the original enzeyme in the saliva
the membrane bound enzymes that turn dissacharides to monosaccharides are :
maltase (breaks down maltose to glucose a)
lactase (breaks down lactose to glucose and galactose)
sucrase (breaks down sucrose to glucose and fructose)
40
how are lipids digested?
physically they are coated in bile salts to create an emuslion this breaks it down into lots of very small droplets called micelles this increases the surface area for the lipase to act quicker
chemically they are hydrolysed by lipase produced in the pancreas this breaks down the ester bond in tryglycerides to form monoglycerides and fatty acids.
41
how are proteins chemically digested?
endopeptidases hydrolyse the peptide bonds between amino acids in the central reigon of the protein molecule leaving a series of peptide molecules
exopeptidases hydrolyse peptide bonds on the terminal acids of the peptide molecule formed by the endopeptidases. leaving dipeptides and single amino acids
dipeptidases hydrolyse dipeptides into amino acids found in the epithilial cell lining the illeum as a membrane bound enzyme
42
why are their no microvilli/villi in the stomach?
the food has not been properly hydrolysed yet. microvilli is for the absorption of solouble substances.
43
where a villi located?
they are located between the lumen and blood capillaries . they are lined by epithelial cells
44
how do villi increase the efficiency of the products of digestion?
they increase the sa to vol ratio
the cells are thin so reduce diffusion pathway
they contain muscle cells so they can move once the products have diffused in. maintaining diffusion gradient
they are surrounded by blood capillaries which maintain diffusion gradient
they epithelial cells lining contain microvilli which further increase the sa
45
how are the products from the digestion of lipids absorbed?
micelles move towards the illeum epithilial cells. the monoglycerides and fatty acids seperate from the micelles as they are non polar and can diffuse across. through movement they make contact with epithelium cells. At the endoplasmic reticulum they are combined againto form tryglecrides. at the golgi body they are further processed adding cholesterol and lipoproteins forming chlyomicrons
46
what are chylomicrons and how do they move out the lumen?
chylomicrons are produced at the golgi body adding cholesterol and lipoproteins to tryglycerides. this moves out the epithelial cells via exocytosis to the lymphatic capillary called the lacteal. this is found at the centre of the villus. from here it can travel via more lymphatic vessels to the blood stream.the tryglecerides in the chlyomicrons further hydrolysing it by an enzyme in the endothelial cell in the blood capillary.
47
how would you test for starch?
Iodine is added to the sample if it turns black/blue starch is present.
48
what is haemoglobin and what is its role of ?
haemoglobin is protein molecule with quarternary structure that is efficient in loading oxygen under a set of conditions and also unloading it at another
49
describe the structure of haemoglobin ?
secondary - 2 beta pleated sheet 2 alpha helix
quarternary- 2 pairs of polypeptide chains each polypeptide is joinded to a haem group - ferrous (fe2+) that can bind to oxygen. this means one molecule of haemoglobin can hold 4 oxygen molecules
forms a spherical molecule
50
where does haemoglobin load and unload and how does affinity effect this?
haemoglobin is loads /associates oxygen at the lungs
haemoglobin unloads/disassociates oxygen at the tissue
haemoglobin with high affinity (attraction) to oxygen find it easier to load but harder to unload
haemoglobin with low affinity find it harder to load but easier to unload.
it can changes it affinity by chemical interactions with the quarternary /tertiary structure
51
why do different animal/ species have different haemoglobin?
different species produce different amino acids sequences hence the quarternary and tertiary structure are different. this therefore affects how oxygen binds to the haemoglobin
52
are all oxygen molecules released when the human is not active?
when the human is not active the oxygen is reserved until the human becomes more active
53
what is the oxygen dissacoiation curve ?
the relationship between saturation of haemoglobin with oxygen and partial pressures of oxygen
54
describe and explain the oxygen dissacotiation graph
the quarternay structure of the haemoglobin makes it difficult for oxygen to bind at low partial pressureog oxygen.
After the first o2 binds the quarternary structure is changed. It takes little increase in partial pressure of o2 to therefore bind. and the 2nd molecule binds easier .this is called positive cooperativity. the 3rd molecule also binds with little increase in partial pressure.
In theory it should easy for the 4th molecule to bind however it is harder in practice. this is because it is difficult to find a single molecule to bind to the last active site of haemoglobin. this causes the graph to glatten off.
55
haemoglobin is different in different animals explain how the graph can differentiate and what it means?
A graph more to the left side means that the haemoglobin has higher affinity and oxygen associates easier but it harder to disassociate
A graph more to the right means that the haemoglobin has lower affinity and oxygen associate harder disassociates easier
56
explain the effect of carbon dioxide on haemoglobin?
carbon dioxide reduces affinity of haemoglobin for oxygen. This means in areas of high concentration of CO2 oxygen unloads easier
this is because dissolved CO2 is acidic and low pH and changes the quarternary structure of haemoglobin
57
explain how oxygen is loaded at the lungs and unloaded at the tissue?
In the lungs their is low concentration of CO2 in blood this means the pH of haemoglobin is higher changing its quarternary structure so it has a higher affinity for oxygen allowing it to load easier.
the increases affinity allows haemoglobin to travel to the tissues wihtout losing it
In respiring tissues CO2 which is acidic makes the blood have a low pH.This changes the quarternary strucutre of haemoglobin causing it to have a lower affinity . Therefore oxygen unloads easier.
58
explain how their is always sufficient oxygen for respiring tissues?
the higher the rate of respiration the more CO2 produced.This in turns causes the blood to have a lower pH.A lower pH changes the quarternary structure of the haemoglobin allowing more oxygen to unload.So more is available for respiration.
59
what is the bohr shift?
the addition of the carbon dioxide forces the oxygen disassociation graph to shift to the right. This means slighlty less oxygen is loaded at the lungs but a lot more is unloaded at the respiring cell
60
describe how different animals partial pressure of oxygen will affect the affinity of haemoglobin
An animal that lives in an environment of low partial pressure of oxygen has haemoglobin that has a greater affinity for oxygen than animals that live in an environment of high partial pressure of oxygen.
61
what is a transport system?
Due to smaller sa to vol ratios and more active animals .bigger and active animals require strucutres to absorb nutrients ,gases and remove waste products.A transport systems move materials in cells to a exchange surfaces and back
62
what features to transport systems require?
a medium to carry materials (e,g blood)
a form of mass transport that can move the medium in bulk through quicker than diffusion
a closed systems of tubular vessels which the medium can travell across
a mechanism for moving the transport medium within the vessels (e.g heart)
63
why is blood passed back over the heart before being distributed to the tissue?
the pressure of the blood is too low at the lungs as it has to pass through small capillaries. at the heart its increased which allows it to travel quicker around . this is vital as humans have a high high body tmeperature and lots of metabolic reactions
64
difference in atria and ventricle
atria collect deoxygenated blood from body and oxygenated blood from lungs.the walls are thin and elastic to collect blood
ventricles pump blood to the lungs and around the body. the walls are much thicker,muscular as it has to contract and pump blood strongly around the whole body. the left is more muscular as it has to pump blood for the whole body
65
what seperates the right & left atrium and ventricle
right atrium and ventricle is seperated via tricuspid valve
left atrium and ventricle is seperated via bicuspid valve
these prevent backflow of blood which is extremely dangerous
66
how does the heart have the energy to pump?
heart has coronary arteries which surround the heart.it takes oxygenated blood from the atrium .blockage of these vessels cause myocardial infarction or heart attack as the heart muscles cannot respire.
67
what are the 2 phases of the beating of the heart?con
contraction = systole
| relaxation =diastole
68
describe the relaxation (diastole ) part off the cardiac cycle?
diastole- the atria is relaxed. blood flows into the atria from the pulmonary vein and vena cava.the ventricle is relaxed and recoils reuding the pressure. The pressure is lower in the ventricle than the aorta and pulmonary artery finally shutting the semilunar valve and making the 'dub' sound
69
describe atrial parts of the systole in the cardiac cycle?
atrial systole-As the blood fills the atria its pressure increases.When it is full it contracts further increasing the pressure. As the pressure is higher than the recoiled ventricles (relaxed) it forces blood through the atriaventricular
70
explain how valves open and close?
they area deep bowl shape.made of fibrous tissue and are flexible.when the pressure increases on the convex they move aside and let blood pass through. if the pressure is greater on the concave side.the blood builds up on the dip not allowing the valves to open
71
describe ventricular systole?
the ventricle fills up and contracts.this increases the pressure and forces the atraiventriuclar to shut down and prevent backflow. this is the 'lub' sound.the pressure further increases and is now higher than the aorta/pulmonary artery.the left ventricle is extra thick as it must pump blood around the whole blood.
72
what is cardiac output?
cardiac output=total volume of blood pumpued out of the ventricle in one minute dm3/min-1
heart rate= amount of time heart beats in a minute min-1
stroke volume= the amount of blood pumped out of the ventricle in one beat dm3
cardiac output =heart rate x stroke volume
73
After a extensive periods of training why is heart rate reduced?
the heart muscle grow. this means the strength of the contractions increase allowing for an increase in strole volume. if the cardiac output is the same the heart rate will therefore reduce
74
state the key components of all blood vessels?
tough outer fibrous layer - resist pressure from inside and outside
muscle layer- contract and control blood flow
elastic layer-maintain pressure by stretching and recoiling
thin endothelium layer- smooth reducing friction and thin to allow diffusion
lumen- blood passes through
75
describe the structure of the artery?
| arteries carry blood from heart to tissues
the overall thickness of the artery is great as it resists pressure
the muscle layer is thick compared to veins allowing smaller arteries to constrict and dilate
the elastic layer is thick compared to veins as high pressure is needed to be maintained. During the systole the elastic layer constrict and during diastole the elastic layer recoils
there are no valves as blood does not flow backwood due to high pressure
76
describe the structure of arterioles?
| Carry blood from arteries to capillaries
The pressure of blood in arterioles is lower than arteries.
the muscle layer is relatively thicker than arteries as it can contract and contstrict the lumen and control blood flow into capillaries
the elastic layer is relatively thin compared to arteries as a lot lower presssure is required to be maintained
77
describe the structure of veins?
| capillaries to heart
relatively thinner muscle walls compared to arteries as the veins constriction or dilation does not affect the flow
relatively thinner elastic walls compared to arteries as the pressure is much lower
valves as their is risk of backflow of due to such low pressure
78
what are the stucture of capillary?
its mainly made of thin lining layer. this offers a small diffusion pathway
narrow lumen flattening red blood cells
numerous and highly branched providing a large SA
their spaces between the endothilial cells around white blood cells too escape
79
what is tissue fluid?
tissue fluid supplies glucose, amino acids, fatty acids and ions in solution and oxygen to tissue. in return it absorbs the waste products such as co2. it is the way in which materials and cells exchange materials. cells live in tissue fluid. tissue fluid is made from plasma cellsBlood plasma composition is mainly controlled by homeostasis
80
how is tissue fluid formed?
blood flowing from the arteriole to the capillary has high hydrostatic pressure due to the thin diameter of the capillary.this causes ultrafiltration and forces smaller molecules out (glucose,amino acids,fatty acids,)water molecules oxygen) through holes only leaving bigger proteins, red blood cells and platelets
81
how is tissue fluid reabsorbed?
towards the venule end (capillary close to vein)the hydrostatic pressure is much lower due to loss of tissue fluid. Their is also lower potential due to the larger molecules staying in the capillary. This allows for the tissue fluid(which is now filled with waste products) to reabsorb back into the capillary via osmosis
82
what does the tissue fluid do when it is forced out?
the nutrients it contains is exhanged with the cells surrounding the capillary. it takes in the waste produces e.g co2
83
what happens to the tissue fluid that cannot get absorbed back via osmosis?
the rest of the fluid is absorbed by the lymph. this has its own system of capillary like structures around the body. the lymph takes the tissue fluid and release it into the bloodstream.this occurs close to the heart in 2 ducts where the lymphatic system connects to the veins.
the lymphatic system is moved by hydrostatic pressure and contraction of muscles that squeeze lymph vessels
84
what is transpiration?
the movement of water up the xylem cell (stem) powered by the sun. the process is passive.
85
how does water move out the stomata(transpiration)?
the air spaces in the mesophyll are saturated with water vapour (high water potential). the air outside is less saturated in water vapor(low water potential). When the stomata is opened by guard cells the omsosis occurs and water vapour leaves via water potential gradient. Water lost is replaced by the cell walls of the mesophyll cells.
transpiration can be controlled by size of stomatal pores
86
how does water move across the leaf?
when water vapour leaves the air spaces in the mesophyll. the water potential is lowered. this means water can travel via osmosis via neighbouring cells.this carries on with the neighbouring. eventually creating a water potential gradient that moves water from the xylem through the leaf and out via the stomata.
87
how does water travel up the xylem using the cohesion & tension theory?
water has hydrogen bonding which makes it cohesive.xylem vessels creates a continuous column upwards and across the leaf due to its dead cells with no cell walls .when water leaves the stomata it creates a transpiration pull. pulling water up.Transpiration pull puts a tension on the xylem causing negative pressure
88
proofs of cohesion tension theory?
A trees diamter changes with transpiration rate- during the day when water is being pulled and release the trunk is thinner due to tension. then at night when their is less transpiration and the trunk is thicker
If the xylem is broken and air enters water cannot travel up.this is because the continuous xylem is broken
89
how do xylem cells die?
As xylem cells mature they release a substance called lignin this kills the cell. this lignin creates rings around the structure
90
what is a the vascular bundle?
the 2 transport systens (xlyem,phloem)
xylem transports water upwards from the roots
phloem transports sucrose and asimilates made in the (source) upwards and downwards to the (sink)
91
describe the tissue of the phloen?
the phloem is made from sieve tube elements. in sieve tube element the cell is alive but with no nucleus, little cytoplasm and little organelles.the end is perforated (holes) This allows cell sap to travel through.Sieve tube elements are connected with sieve plates. In between seive tube element is companion cells. these are filled with mitochondira to provide ATP.
92
describe the movement of sucrose from the source to the sieve tube element?
sucrose is produced in the leaf via photosynthesis.Their is high concentration of sucrose at the leaf so it can move to the companion cell via facilitated dissusion
H+ ions are actively transported out the companion cell into cell wall.this creates a diffusion gradient.The H+ travels down a concentration gradient into the sieve element via facilitated diffusion.However the co transporter protein also brings sucrose
93
describe mass flow of sucrose?
sucrose is actively transported from the source to the seive tube element. the increase in sucrose lowers the water potential forcing water from the xylem into the sieve tube elmement via osmosis.this increase in volume creates a high hydrostatic pressure.At the sink sucrose is used up via respiration.further sucrose is actively transported to the sink. Due to the low water potential water moves from the sieve tube to the sink cell via osmosis. the hydrostatic pressure of the sieve tube is reduced. this creates high hydrostatic pressure and low hydrostatic pressure at the sink creating a gradient for mass flow of sucrose
94
explain the ringing experiment?
the phloem is around the circumference of the xylem
From a section of the tree.Its bark and phloem is removed.Over time it can be seen that above the section it starts to swell. Samples can taken from the swelling section.it should be high in sugar (sucroce) and other organic ions.Non-photosynthetic below the section begin to wither and die. this proves phloem is the tissue reponsible for moving sugars.
95
explain the tracer experiment?
plant is exposed to radioactive carbon dioxide isotope C14. When this enters the plant it produces sugars that are also radioactive. Sections stems can be cut and anaylsed with an xray film . the film shows the radioactive sugars as blackened. the blackened areas are all shown in the phloem which proves phloem is the only tissue used in transporting sugars.
