Topic 3A & 3B - Exchange and Transport Systems Flashcards
(150 cards)
1
Q
What are advantages of large organisms being multicellular?
A
Many cells allow them to be less vulnerable to death as cells can be readily replaced if they have died or been damaged
2
Q
Why can’t certain cells get to the size of small fish?
A
They’re prokaryotes (as a side note so dont have specialised cells, but main point…): their surface area to volume ratio would be too small and so waste products would build up.
*
3
Q
Read over.
Before you do, think about what mass transport is and why its needed.
A
Mass transport iswhen the bulk movement of gases or liquids in one direction occurs, usually via a system of vessels in animals.
(FOR CONTEXT: small organisms have a large surface area to volume ratio. This allows sufficient gas exchanges across their membranes to supply their relatively small number of cells (or volume)).
- larger organisms have a smaller surface area to volume ratio
Gas exchange across that body alone would only allow the first few layers of cells to receive oxygen. SO, large organisms rely on mass transport systems which are adapted to provide large SA:V needed.
- Such as circulatory system with networks of capillaries or respiratory system with loads of alveoli.
4
Q
Features a gas exchange surface must gave in order to be efficient, to increase rate if diffusion.
A
- steep concentration gradient (maintaining it, so that diffusion occurs constantly at a high rate).
- thin exchange surface (one epithelium/ endothelium cell layer thick) for a short diffusion pathway.
- large surface area for more diffusion to occur at once (many possible areas for diffusion to occur across)
NB that a large SA:V ratio is for organisms as a whole, not their systems.
5
Q
Explain how air moves in to terrestrial insects and how they exchange gases.
A
- Air enters the tracheae through the spiracles (pores on the outside)
- Tracheae branch into smaller tracheoles WHICH have thin permeable walls
- This allows oxygen to diffuse down a concentration gradient directly into repairing cells and waste CO² diffuses out.
- These insects also “pump” their abdomens rhythmically to move air in and out (maintaining steep concentration gradient).
6
Q
How are terrestrial insects adapted to exchange gases efficiently?
A
- large SA: there are very many tracheoles, increasing the area over which diffusion can take place.
- short diffusion pathway: tracheal lines with single layer of cells to minimise distance travelled by gases.
- Maintenance of a steep conc. gradient: rhythmic abdominal movements (pumping), removing air low in O² out and allowing air high in O² in through spiracles.
- Also fluid in the end of tracheoles are removed/ moves outwards during abdominal pumping and exercise.
7
Q
How do insects prevent water loss through water evaporating out and escaping?
A
- They close their spiracles as a preventative method; H²O vapour can’t diffuse out down concentration gradient for a (short?) period of time
- Waxy cuticle on surface; its impermeable to water so it can’t escape (no diffusion out of epithelial cells, same in plants)
- Hairs around spiracles; traps H²O vapour, decreasing the steepness of the conc. gradient, hence slowing the rate of diffusion.
8
Q
How is the gill structure in a fish adapted for efficient gas exchange?
A
- large surface area: very many hill filaments that then have further lamellae structures.
- short diffusion pathway: lamellae have a thin exchange surface, short distance (see diagrams).
- steep oxygen concentration gradient: counter current AND flow of O² rich water outside and many blood capillaries.
9
Q
what is the counter current principle?
A
This is where blood flows over the gill lamellae (that stick up) in the opposite direction to the flow of the fish’s blood.
10
Q
Why is the counter current principle useful?
A
The counter current system helps maintain an oxygen diffusion gradient between the water and the blood ACROSS THE WHOLE LENGTH OF THE GILL LAMELLAE; so a maximum volume of oxygen can reach the cells, for respiration.
11
Q
Read over
A
Food compounds such as starch, proteins and lipids are large and insoluble molecules, unable to be absorbed directly into blood. Must first be digested intibsmall soluble molecules.
- Digestion is catalysed by enzymes secrete6into the lumen of the digestive system.
12
Q
Which enzymes are responsible for the complete hydrolysis of starch
A
amylase and then maltase
13
Q
What are disaccharidases?
A
These are membrane bound enzymes that are attached to the cell membranes of epithelial cells lining the ileum and they hydrolyse disaccharides into monosaccharides.
14
Q
2 locations where maltase is produced
A
salivary glands and pancreas
15
Q
Give the name of the membrane bound enzymes located in epithelial cells lining the ileum
A
sucrase importantly
maltase
lactase
16
Q
word equation for hydrolysis of maltase
A
Maltose»_space; (H²O + maltase)»_space; glucose + glucose
17
Q
In the digestive system, what type of Bond is hydrolysed during the digestion of disaccharides into monosaccharides? what type of reaction?
A
glycosidic, hydrolysis; using water to break bonds
18
Q
Suggest how the two monosaccharides of glucose and fructose individually might be transported across the cell membrane of the cells lining the ileum
A
Glucose is transported via co transport and fructose by facilitated diffusion
19
Q
Which enzyme is responsible for hydrolyzing down triglycerides aka lipids
A
lipase
20
Q
Where is lipase produced and where does it work?
A
Produced in the pancreas and works in the small intestine
21
Q
word equation for hydrolysis of lipids
A
triglyceride»_space;(H²O + lipase)» monoglyceride and (2) fatty acids
22
Q
What is a monoglyceride
A
A type of fatty acid consisting of one glycerol and one fatty acid chain attached to it
23
Q
What bond is broken in the digestion of a triglyceride
A
ester
24
Q
What effect would you expect the products of lipid digestion to have on the pH of the small intestine, explain.
A
To lower pH as fatty acids are acidic
25
Give two ways in which bile salts aid lipid digestion: technically the one way.
(The neutralize the pH - this is a side note, as it helps general digestion) and emulsify large lipids to increase the surface area for lipase to act on AND increase the rate of hydrolysis (before digestion).
26
Where is bile made and where is it secreted from
made in the liver and stored in the gallbladder secreted via the bile duct
27
What is a micelle and how is it formed
Micelles are formed after emulsification has taken place to create smaller lipid droplets. Then lipase hydrolyses the small lipid droplets to create micelles, which, are simply a structure of monoglycerides and fatty acids stuck to bile salts.
Hydrophobic inside, hydrophilic outside which allows it to dissolve (it's water soluble)
28
how does a micelle aid lipid absorption and how the contents pass through the cell membrane?
Micelles allow for many monoglycerides and fatty acids to be transported at once with ease to where they need to be absorbed.
Hydrophobic inside, hydrophilic outside which allows it to dissolve (it's water soluble)
-At the site of absorption, micelle breaks down and components are absorbed into the small intestine by simple diffusion BECAUSE phospholipid bilayer allows lipid soluble molecules (which are then taken away by chylomicrons)
29
General name for enzymes that break down on proteins, and then the 2 specific types
peptidases: endopeptidases and exopeptidases
30
Bond between amino acids of proteins that is hydrolysed (using water)
peptide bond
31
Main difference between endo and exopeptidases?
Exo: removes one amino acid off of the ends of polypeptide chain.
Endo: Produces polypeptide fragments from within the original polypeptide chain (in the middle)
32
Name of final product of protein digestion
amino acids
33
How does the action of endopeptidases affect the overall rate of protein digestion?
Rate increases and the surface area increases: which also allows for both endo/exopeptidases to work more efficiently
34
Which endopeptidase enzyme might have an optimum pH of around 2-3 and why?
Pepsi: works in the stomach where the HCl is present, so an acidic pH.
--- Enzyme is produced in stomach and released into stomach by cells in the stomach lining.
35
State the 2 types (examples) of endopeptidases you have to know, and where they are produced
Trypsin and chymotrypsin
- fairly easy to remember due to trypsin common origin.
Produced in pancreas
36
What are dipeptides and dipeptidases? Where are these found?
2 amino acids
Enzyme that hydrolyses dipeptides and their peptide bond
Dipeptidases are membrane bound enzymes found in the ileum of the small intestine (on the epithelial cells?)
37
What is the role of water in protein digestion?
Hydrolyse peptide bonds in between amino acids
38
How are the following monosaccharides absorbed across the cell membrane:
1. glucose
2. galactose
3. fructose
1. glucose absorbed by active transport/ co-transport with sodium ions via a co-transporter protein.
2. galactose absorbed in same way via a co-transporter protein.
3. fructose: facilitated diffusion through a different transporter protein
39
Intracellular enzyme
one working inside cells
40
how are monoglycerides and fatty acids absorbed across the cell membrane
Micelles help to move monoglycerides and fatty acids across the epithelium. This is because micelles constantly break up and reform so they can release the monoglycerides and fatty acids allowing them to then be absorbed, whole micelles are NOT taken up across the epithelium.
The contents are lipid soluble so can diffuse directly across.
41
how are amino acids absorbed across the cell membrane?
Amino acids are absorbed via co-transport in a similar way to glucose and galactose. Sodium ions are actively transported out of the ileum epithelial cells into the blood. Then this can create a Sodium Ion concentration gradients as the sodium ions can then diffuse from the lumen of the ileum into the epithelial cells through sodium dependent transporter proteins, carrying the amino acids with them
42
Would a mouse or an elephant lose heat quicker?
Mice = large SA: V and lose heat quickly due to this.
The mouse is very active so has a high metabolic (respiration) rate, releasing lots of heat energy, keeping the mouse warm.
- They also eat high energy foods like grains (and fur to reduce hear loss).
- Also as a note, it's warmer underground, good for small animals
43
How do guard cells open and close stomata?
- photo synth. produces glucose, lowering the water potential within the guard cells
- hence, water molecules move from nearby epidermal cells into guard cells by osmosis down the water potential gradient.
- this makes them turgid; causing the stomata to open
44
What kind of environment do zerophytes live in?
- when writing exam Qs, you must try to link this to any adaptation you mention
These are plants adapted to their warm, windy, and dry habitats - where water loss by transpiration is often a problem.
NOTE THAT an increase in humidity can decrease the rate of diffusion.
45
Adaptations of zerophytic plants
1. Sunken stomata trap water vapour, reducing evaporation rate by reducing concentration
2. 'Hairs' on (lower) epidermis to trap water vapour near stomata
3. Curled leaves w/ stomata inside - protects from wind that increase diffusion / evaporation by conc. gradient
4. Less stomata to stop water escaping
5. Thick waxy, Waterproof cuticles on leaves and stem epidermises, reduce evaporation.
46
Extra explanation on why curved leaves benefit xerophytic
prevents air high in water concentration from being swept away and replaced w/ low water concentration air.
Reducing evaporation from diffusion by having a shallow gradient.
47
remember
comparative language
48
relationship between internal and external intercostal muscles
antagonistic, move opposite
49
Events that happen when you exhailing - including pressure, volume, and muscles.
- the opposite for inhailing
- internal intercostal contract, external relax - antagonistic action.
- volume decreases (of thorax), gas pressure ^
- pressure gradient causes gas to move out (think due to build-up of pressure).
- diaphragm muscle relaxes & rises to cone shape, ribs move down and in
- THINK WHEN YOU EXHALE, YOU RELAX ON THE INSIDE, relax internal intercostal muscles.
50
Briefly describe inhalation
diaphragm contracts & flattens, external intercostal muscles contract (internal relax) AND ribs move up/out, which increases volume, and this change decreases the pressure.
Then, as a result, the pressure in the lungs is lower than the atmospheric pressure, so air can enter down the pressure gradient.
51
How does the oxygen diffuse in the final stages of breathing.
The alveoli are covered in a network of capillaries.
Oxygen enters by diffusing across alveolar epithelium and then, through capillary endothelium.
52
Adaptations for alveoli (explanations to do in your head)
1. MANY networks of capillaries (maintain conc. gradient, blood brought to lungs is low in O2.
2. Alveolar epithelium and capillary endothelium, diffuses across one cell layer of thickness AND flattened (or just thin), short d. pathway.
3. MANY alveoli, large SA, ^ diffusion
4. Ventilation ensures air high in O2 comes in, exchanges low O2 air, maintaining gradient
53
What lungs structures cause the pressure gradient?
What maintains the diffusion gradient?
the diaphragm and intercostal muscles (may want to watch a video on pressures)
ventilation by lungs and circulation of blood
54
A mountain climber is climbing at altitude, where there's less O². Suggest how this will affect gas exchange in alveoli.
(note that less oxygen means that's there's higher pressure higher up)
Less air means less O² inhaled in each breath, so the concentration gradient between the alveoli and capillaries is less steep, so there's a decreasing RATE of diffusion.
55
A mountain climber is climbing at altitude, where there's less O². Suggest how this will affect gas exchange in alveoli.
(note that less oxygen means that's there's higher pressure higher up)
Less air means less O² inhaled in each breath, so the concentration gradient between the alveoli and capillaries is less steep, so there's a decreasing RATE of diffusion.
56
Tidal volume
vol of air in each breath at rest
57
Ventilation rate
Number of breaths per min
58
Forced expiratory volume ¹ (FEV¹)
Max volume of air breathed out in one second
59
Forced viral capacity (FVC)
Max volume of air that's forcefully breathed out after really deep breath in
60
What's a spirometer?
A machine to measure lung function through the volume of air breathed in and out. You can figure out many measures through a graph produced from machine.
61
Why is there residual air that can't be expelled fully out?
Because you always diffusion going on gases
62
Tuberculosis:
1. the cause
2. impact on lung function
3. symptoms
1. Bacteria: a person's immune system cells build a wall around bacteria in lungs forming hard tubercules.
2. Infected tissue in tubercules die and the exchange surface is then damaged (can lead to fibrosis): ↓ tidal volume and increased ventilation rate as less inhaled.
3. Faster breathing, coughing (blood), fatigue, chest pain.
63
Fibrosis:
1. the cause
2. impact on lung function
3. symptoms
1. Scar tissue building layers on alveoli: due to infection, asbestos, dust.
2. Scar tissue less elastic and thicker than normal (alveoli can't expand as much, can't hold as much air): reduced tidal vol and FVC - smaller amounts can be breathed out.
- rate of diffusion is slower across scar tissue and causes faster ventilation rate (to oxygenate blood).
3. faster breathing, chest pain, fatigue, dry cough, short of breath.
64
pulmonary ventilation
on Samsung notes for calculation.
Basically the same as ventilation rate, total volume of air moved in and out in one min
BUT NOT THE SAME
65
Asthma:
1. the cause
2. impact on lung function
3. symptoms
1. Usually allergies like dust: where smooth muscles in bronchioles inflamed and contracts & mucus produced. Constrcition of airways: hard to breathe.
2. Reduced air flow into blood (tidal volume) and so increased ventilation rate to try combat AND the FEV¹ is reduced.
3. wheezing, shortness of breath, tight chest (can use drugs to relax smooth muscles).
66
relationship between volume and pressure
antagonistic as one increases the other decreases
67
Emphysema:
1. the cause
2. impact on lung function
3. symptoms
1. Particles from smoking or long exposure to pollution become trapped in alveoli. Inflammation = phagocytes produced enzyme which accidentally break down elastin protein in the walls.
2. (Elastin helps return normal shape of sacs after breathing) Loss of elastic means alveoli can't recoil to expel air as well - stays in lungs.
- also SA is reduced as walls broken, ↓ gaseous exchange and rate of diffusion.
3. increased ventilation rate (as try to increase O² reaching the blood); also shortness of breath and wheezing
68
Why does a person with asthma have a lower FEV¹ and FVC?
Smooth muscles constricting in bronchioles means smaller lumen and takes longer for some volume of air to be breathed out lungs.
(FEV and FVC are very similarly related)
69
Why do people with fibrosis, asthma and emphysema often feel weak, tired, and struggle with exercise? (6)
1. less O² volume able to enter lungs
2. Less steep conc. gradient
3. Less O² diffuses into blood and exchange gases (for CO² to be let out)
4. less oxygen to muscles
5. less aerobic respiration
6. less energy / ATP produced for muscle contracting
70
How to remember emphysema
Emphysema, Elastic, Elastin, Enlarged alveoli
71
What are standard deviation or error bars used for?
If they overlap, then there's no significant difference in data and difference may be due to chance!
- they show the range of data around the mesn
72
define risk factor
a factor that increases the chance of a person getting a disease
73
What is the risk factor for emphysema
smoking, air pollution exposure and type of employment (like construction)
74
risk factor for asthma
allergies and family history
75
risk factor of fibrosis
working conditions, dust/asbestos exposure
76
risk factor of tuberculosis
weak immune system, age, living conditions (cold?)
77
When comparing lung diseases between different groups of people, what else should be considered?
age, gender, family history, current health state, employment
- although theres a correlation between a risk factor and an incident of a lung disease, another factor may be the cause too
78
extra note
gov works with scientists to put restrictions on risk factors
79
describe the relationship between the size of an organism and it's SA to V
the smaller the organism, the larger the SA:V
80
2 structures that increase the SA of a fish
gill filament and lamella
81
3 substances that make up a micelle?
Bile salts, monoglycerides and fatty acids
82
Name the theory that tries to explain the movement of water up a plant
Cohesion-tension theory
83
haemoglobin found in....
and it's main function is...
red blood cells, it hinds to oxygen and releases it at the tissues.
84
haemoglobin + oxygen
oxyhaemoglobin
85
What does affinity mean?
- is it likely to be high or low in respiring tissues
Affinity refers to the likelihood that haemoglobin will load (pick up) O². Haemoglobins affinity changes depending on the concentration* of O² (partial pressure of O²)
- so in respiring tissues the pO² is low and so is haemoglobin's affinity for O². Haemoglobin unloads O².
- the opposite for lungs
86
alveoli in lungs...
1. HIGH oxygen concentration
2. HIGH pO²
3. HIGH affinity
4. Oxygen UNLOADS
87
Haemoglobin loads oxygen in the lungs but unloads it in the respiring tissues. Why is this an advantage to respiring cells? (3)
- Less likely to take away O² from where it's mist needed
- O² unloaded at aerobically respiring tissues so can be used in aerobic respiration
- to release energy or produce ATP for muscle contraction.
88
What is the relationship of pO² and % saturation of haemoglobin?
on Samsung notes
89
How does haemoglobin respond in low partial pressures?
Haemoglobin has a low affinity for oxygen so there's usually a lower pressure in respiring tissues, so haemoglobin more likely to unload oxygen.
Looking at graph, gradient not very steep as haemoglobin reluctant to take on first oxygen, so at low partial pressures haemoglobin likely to unload oxygen (in respiring tissue) and not so likely to load. So it's advantageous.
90
What does haemoglobin do at higher pressures?
Steeper gradient on graph suggests that haemoglobin reluctant to load more oxygen. It wouldn't want to do this as this leaves no more scope to carry more oxygen when neededin high demand, like when exercising, so will only load at highest pressures.
91
What happens after haemoglobin has loaded the first oxygen?
Hb changes shape (may be why is reluctant to take on the first), so following oxygen is easier to load.
92
Watch ms eustruch video on affinity and dissociation curves
.
93
Bohr effect
- when might CO² level be high?
How different conditions affect haemoglobin affinity:
Bohr effect is a haemoglobin behaviour: when a HIGH CO² concentration so curve shifts RIGHT for the dissociation curve. Haemoglobin's affinity for oxygen decreases because acidic CO² lowers pH and can change the tertiary structure of the protein.
This means oxygen is unloaded easily but not loaded as easily.
- Rapidly respiring cells during exercise.
94
Haemoglobin dissociation curve for animals living in different conditions or one that are more active
See samsung notes for graphs and explanation
95
Put the blood vessels in order
Artery
Veins
Arterioles
Venules
Capillaries
96
Artery width narrows to arterioles, impact?
Increases pressure which helps force useful substances into tissues, AND helps form tissue fluid, as a result
97
Coronary arteries
Glucose rich and oxygenated blood to heart muscles so cells can resp. to release energy to it muscle contraction (to create high pressure in the ventricles)
- left coronary artery provides blood to left ventricle, and right to right...
98
Do all arteries carry oxygenated blood?
No, pulmonary artery carries deoxygenated blood to lungs
99
Structure of arteries and function of them.
Walls made of thick muscle tissue layer and elastic tissue on the outer wall, inner endothelium lining folded TO allow arteries to stretch (and helps maintain high pressure).
Oxygenated blood (expect from pulmonary artery)
100
Structure of arterioles and their function.
These branch from a larger artery and mainly have circular muscles in their walls.
Blood is directed to different areas of demand in body.
- Arterioles can contract to restrict blood flow or relax to allow full blood flow.
101
Structure of veins and their function.
Any special advantages of or to the veins?
Blood back to the heart in low pressure: wider lumen than artery (good for when more blood flowas there's little resistance), little elastic, and muscle tissue.
- valves, no backflow AND blood flow in veins is helped by contraction of nearby body muscles.
Deoxygenated blood.
102
Name of vessels attached to kidneys
Renal artery and vein
103
Do all veins carry deoxygenated blood?
No, pulmonary vein returns oxygenated blood from the lungs to the heart
104
Structure of capillaries and their function.
Branching from arterioles, the one cell layer thick (capillary endothelium) adapted for efficient exchange of useful substances...
Large SA:V > lots of them in capillary bed, short diffusion pathway.
105
Why might arteries fluctuate in pressure, and so why might fairly high pressure in capillaries be beneficial?
Heartbeat causes contracting and relaxing of left ventricle, changing pressure in arteries.
Note that this fluctuating effect will decrease the further away arteries are from the heart.
- to help force out useful substances into the tissues via tissue fluid
106
What is tissue fluid, and what does it contain / cannot contain?
It's fluid that surrounds cells and tissues, and it's made from molecules that leave the blood plasma, such as oxygen water and nutrients that the cells take in. ALSO Metabolic waste like carbon dioxide diffuses into the tissue fluid.
Doesn't contain proteins or RBCs as too big to get past cell surface plasma membrane
107
Through which vessels does tissue fluid leave?
Lymph capillary or lymphatic vessels.
108
Pressure filtration
Capillary bed: substances move out of capillaries into tissue fluid (fluid that baths tissue cells)
- to do with hydrostatic pressure
109
Why does pressure filtration occur?
The contraction of the left ventricle and narrowing fromarteries into arterioles causes a hydrostatic (to do with water potential) pressure gradient....and also small soluble molecules are forced out into tissue fluid.
110
How is tissue fluid forced out?
Through pores in endothelium or simply diffusing through cells down hydrostatic pressure / diffusion gradient
111
When can you use the term tissue fluid (reminder card)
Only when the fluid (being water and dissolved substances) are within the tissue
112
Describe the formation of tissue fluid
See summary bullet points on notes
113
What happens to excess tissue fluid?
The fluid and substances in it is drained into the lymphatic system (lymph capillary), and returned to the circulatory system
114
What causes pressure filtration that forces oxygen, water and nutrients out of the capillaries?
Hydrostatic pressure being higher in the arteriole end of the capillary end compared to the tissue fluid
115
Main purpose of tissue fluid?
Allows exchange of substances (O² and glucose) between cells and get rid of metabolic waste.
116
Adaptation of the left ventricle?
Thicker more muscular walls than the right so can contract more powerfully blood all around body, while right side just pumps blood to the lungs
117
Adaptation of the ventricles?
Ventricles have thicker walls than atria to push blood out of the heart to further distances, while atria only pus blood to the next ventricles
118
Adaptations / structure of the valves (AV and SLV)?
AV valves link atria to ventricles stopping backflow as ventricles contract. SL valves link ventricles to either pulmonary artery or aorta and stop blood flowing back into heart after ventricles contract
119
Adaptations of the cords in the heart?
They attach to the AV valves to the ventricles to stop them from being forced back (the valves) into the atria when ventricles contract.
120
Describe how valves work in relation to pressure.
Unidirectional flow.
Position of valves depends on relative pressure of heart chambers. Higher pressure behind forces valves open, higher pressure in front of it forces it shut.
- could mention the behaviour of these when describing the direction of blood flow through the heart. CONTRACTION INCREASES PRESSURE
121
Cardiac output formula
= stroke volume × heart rate
cm³ and bpm
122
Stroke volume is the blood pumped during each heartbeat. Why do athletes generally have bigger ones?
Heart (muscles) had been trained to be thicker to pump more blood per heart beat cycle.
123
Cardiovascular disease and how they start, and so formations they can lead to?
A term used to describe diseases of the heart and blood vessels, - they start with the formation of an atheroma
- and then lead to aneurysm
- then thrombosis
- then myocardial infraction (thrombosis in coronary arteries)
- then CHD as a result of many atheromas in coronary arteries.
124
describe the formation of an atheroma
in the lining of artery endothelium after it's been damaged by high blood pressure (e.g.), deposits (of fatty material, WBCs, dead cells, and connective tissue, cholesterol) build up.
This causes the endothelium to be pushed out and decrease lumen size and create an atheroma (and increase blood pressure).
125
How do atheromas increase the risk of aneurysm occuirng
They damaged and weaken the artery due to the presence of the plaque, and the narrowing of the arteries increases the PRESSURE.
- So when blood travels through a weakened artery at high pressure, it may push the endothelium layer out through the elastic layer!
- balloon like swelling occurs which is the aneurysm.
busting causes a hemorrhage
126
describe how an atheroma can cause thrombosis
Atheroma breaks through endothelium into lumen means that the smooth surface is now a rough surface as the artery wall is damaged.
- platelets and fibrin (protein for helping clot) accumulate at damage and form a blood clot. This is a THROMBUS.
Can cause a complete blockage if artery or dislodge and block a blood vessel elsewhere.
127
Name of blood clot for burst atheroma
Thrombus
128
Why does thrombosis in the coronary arteries lead to myocardial infarction?
1. blockage due to thrombosis and so thrombus (blood clot) meaning less blood can get to ventricular muscles.
2. less o² and glucose supplied
3. less aerobic respiration from heart muscle cells
4. less energy released for muscle contraction (in ventricles to pump blood around the body)
5. Heart cells start to die (no energy for metabolic reactions), leading to myocardial infarction and often a fatal heart attack
129
Function of xylem
Transports water an mineral ions in solution, from roots to leaves (stroma as for evaporation) and is to move these up the plant rapidly over large distances.
130
How is the xylem able to transport substances rapidly?
The xylem has little cytoplasm to get in the way (and also no end walls between the cells in the column), this is beneficial as obstruction prevents the rate of transpiration
131
what can break up the transpiration stream and disrupt the rate
air bubbles
132
explain cohesion-tension theory, with describing each feature separately
cohesion: hydrogen bonds attract other water molecules (the hydrogen and oxygen) and so stick to each other
- allowing for a continuous column of water moving up the xylem.
tension: this is the suction created in the xylem when water evaporates at the stomata HELPS pull water up against gravity.
--- tension causes upwards and attractions pulls next molecules up and the one after and so on if one evaporates, hence continuous column
133
ventricle systole
when ventricles contract and atria relax
134
Structure and function of phloem
Transports sucrose in plants from source cell to sink cells.
Sieve tube elements (structurally separate, tissues for organising movement of compounds) and thin layer of cytoplasm.
- lack nucleus and few organelles to give more room to allow solutes like sucrose to not be disrupted in flow and max assimilation (translocation)
135
Companion cell
Accompanies each phloem cell and provide energy; this is for the active transport of sucrose (can affect water potential and so mass flow theory).
- MITO. in large numbers for large amounts of aerobic respiration
136
Function of sieve tubes or pores
Continuous movements of sucrose
137
Function of cell wall in regards to mass flow theory
Cellulose cell wall strengthens to be able to withstand hydrostatic pressures.
138
Why is mass flow theory devised/
translocation is too fast to be explained by diffusion
139
Why does the plant create sucrose instead of glucose?
Sucrose is less reactive
140
source cells
photosynthesising cells in leaves such as palisade cells
141
sink cells
such as roots or useful parts of the plants such as potatoes to stores or use the assimilates of translocation
142
Explain mass flow theory
1. Source cells: active transport to load the solute of sucrose (and some water) into sieve tubes. Water potential then decreases due to sucrose and water in from xylem by osmosis. SO increasing hydrostatic pressure.
2. Then, flowing down, there's a pressure gradient that pushes sucrose (solutes) along sieve tubes to sink cells.
3. At the end, sucrose diffuses by simple diffusion into sink cells or companion cells. Increase water potential IN SIEVE TUBES so that osmosis occurs back into the xylem.
In turn, hydrostatic pressure in sieve tubes decreases!
- steeper conc. grad means faster rate of translocation
- the removal of water at the end decreases the hydrostatic pressure, creating a pressure gradient.
143
note
companion cells cannot be source or sink cells
144
What are the types of evidence to support mass flow?
1. ringing experiment on bark of trees
2. observing aphids for pressure in phloem
3. radioactive tracers
4. metabolic (enzyme) inhibitors
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How does a ringing experiment (in the bark of trees) prove mass flow?
A ring of bark is removed from a section of bark with no xylem, just phloem. (Extract fluid from above and below the ring.)
ITS OBSERVED: a bulge forms above the ring which contains a higher sucrose concentration of solution compared to below.
IT PROVES: the downward flow from source to sink in phloem and that sugars cannot be transported so phloem transports sugars, and that there's a hydrostatic pressure gradient coming from source.
146
How do aphids prove mass flow (specifically the pressure aspect)?
Aphids feed in sucrose in phloem. So you would allow the aphid to pierce the bark with a stylet and remove the aphid to leave the stylet behind.
- Collect fluid from stylet and calculate across stem sections the rate of flow to indicate pressure.
IT PROVES: there's a hydrostatic pressure gradient due to the difference in rate of flow of fluid being produced and so faster at source, so gradient between source to sink.
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How do enzyme (metabolic) inhibitors prove mass flow?
Introducing an inhibitor that catalyses the condensation/hydrolysis of ATP stops translocation.
THIS PROVES: ATP (releasing energy as it's broken down) is used to actively transport sucrose across the companion cell into the phloem. This decreases the water potential. Allowing water to move from xylem by osmosis. Creating a hydrostatic pressure gradient between source and sink... But this wouldn't occur with inhibitor. THIS IS EVIDENCE THAT active transport occurs of sucrose.
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How do radioactive tracers prove mass flow?
Radioactive carbon (¹⁴C) can track movements of organic substances throughout if you isolate a part of the plant and supply it with ¹⁴CO² that diffuses through stomata. Photosynthesis allows the carbon of the radioactive labelled CO² to be incorporated into the sucrose. Visible movement of carbon through stem can be tracked with autoradiography over time intervals!
THIS PROVES sucrose moves through phloem from source to sink due to a downward hydrostatic pressure gradient.
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Objections against the evidence for mass flow?
1. Sucrose and sugars travel to many different SINKS, not just the one with the HIGHEST WATER POTENTIALS, like model says.
2. Sieve tubes create barrier to mass flow. A lot of pressure may be needed for solutes to get through at the rate they do.
150
How does removing a ring off bark mean that branches receive more nutrients?
Sucrose is unable to move to roots. This creates a concentration gradient and hydrostatic pressure gradient, and so sucrose accumulates at the bulge, and so sucrose stays/ moves to the source and increased fruit production.
