Organisms Exchange Substances With Their Environment Flashcards
(164 cards)
1
Q
What is “1” referring to?
A
The superior vena cava
2
Q
What is 2 referring to?
A
The right atrium
3
Q
what is 3 referring to?
A
The right atrioventricular valve
4
Q
What is 5 referring to?
A
The pulmonary valve
5
Q
What is 6 referring to?
A
The left ventricle
6
Q
What is 7 referring to?
A
The aorta
7
Q
What is 8 referring to?
A
The pumonary artery
8
Q
What is 10 referring to?
A
The pulmonary vein
9
Q
What is 11 referring to?
A
The left bicuspid valve
10
Q
What is 12 referring to?
A
The left ventricle
11
Q
What is 13 referring to?
A
The aortic valve
12
Q
What are two features all exchange surfaces that relate to surface area and thickness?
A
All exchange surfaces are adapted to have a large surface area relative to the volume of the organism and are very thin so that diffusion can occur across a short distance
13
Q
What are the elements of Gas Exchange in Insects?
A
Spiracles, Tracheae and Trachioles
14
Q
What are spiracles?
A
They are stomata-like structures in the skin/exoskeleton of the insect. They are little holes in the walls of the insect that take up gas.
15
Q
What are the Tracheae?
A
They are tubular structures attached to the spiracles. Like the Trachea in the lungs. It transports the gas within the insect.
16
Q
What are trachioles?
A
They are like the bronchioles as they branch out from the Tracheae and deliver blood to the tissues of the insect, to exchange the gas.
17
Q
How are diffusion gradients used in gas exchange in insects?
A
Different diffusion gradients exist along the length of the tracheal system, with the ends of the trachioles having the lowest concentration of oxygen and the highest concentration of CO2, as a result of nearby respiration, and causing the trachioles to draw oxygen further along the system.
18
Q
How do insects use muscles to aid gas exchange?
A
Insects flex their bodies by contracting their muscles. This expands and compresses the system. Air sacs between the tracheae and the trachioles expand and compress. This fluctuating pressure moves air in and out of the body, ventilating the system.
19
Q
How is water used in gas exchange in insects?
A
The trachiole ends are filled with water. During periods of intense activity, lactose (from lactic acid) builds up. As lactose is a solute, water is drawn into the cells to rebalance the cells. Therefore the trachioles move the water in the system, and this diffuses by osmosis into the cells, allowing more room for gas in the trachioles, increasing gas exchange.
20
Q
What are the two substructures in gills and how do they connect?
A
The gill filaments and the gill lamellae. The Gill filaments look like filaments, or the tentacle-like parts of an anemone. The gill lamellae are located on these filaments, sticking up at a right angle to the filament.
21
Q
What is the countercurrent flow principle?
A
In order for sufficient gas exchange to occur in fish, the flow of deoxygenated blood and oxygenated water must be in opposite directions.
22
Q
Why is the countercurrent flow principle a good adaptation for gas exchange (or superior to concurrent flow)?
A
In fish, oxygen is gained by diffusion from surrounding water into the bloodstream. If the two streams are going in seperate directions, there will be less steep diffusion gradient, and the reaction will reach equilibrium at a higher oxygen saturation level because of this, as the oxygen saturation levels will increase similarly, meaning more oxygen can be exchanged. In concurrent flow there is a larger concentration gradient, meaning oxygen is exchanged too quickly, and the reaction will reach equilibrium sooner, at a lower oxygen saturation. This means less oxygen is absorbed.
23
Q
What are the two substructures in gills and how do they connect?
A
The gill filaments and the gill lamellae. The Gill filaments look like filaments, or the tentacle-like parts of an anemone. The gill lamellae are located on these filaments, sticking up at a right angle to the filament.
24
Q
What is the countercurrent flow principle?
A
In order for sufficient gas exchange to occur in fish, the flow of deoxygenated blood and oxygenated water must be in opposite directions.
25
Why is the countercurrent flow principle a good adaptation for gas exchange (or superior to concurrent flow)?
In fish, oxygen is gained by diffusion from surrounding water into the bloodstream. If the two streams are going in seperate directions, there will be less steep diffusion gradient, and the reaction will reach equilibrium at a higher oxygen saturation level because of this, as the oxygen saturation levels will increase similarly, meaning more oxygen can be exchanged. In concurrent flow there is a larger concentration gradient, meaning oxygen is exchanged too quickly, and the reaction will reach equilibrium sooner, at a lower oxygen saturation. This means less oxygen is absorbed.
26
From top to bottom, describe the structure of a plant tissue.
Waxy Cuticle, Upper Epidermis, Spongy Mesophyll, Vascular Bundle, Lower Epidermis (with guard cells and stomata), Waxy Cuticle.
27
What is the analogy you use to remember leaf tissue structure?
A cheese and burger-sausage ception sandwich (obvi plant based version).
Top waxy cuticle= top bun
Upper Epidermis= smooth american cheese (just there for protection, adds no taste (or special function))
Palisade Mesophyll- A lettuce leaf
Spongy Mesophyll- A spongy tofu "burger", full of air pockets.
Vascular Bundle- Veggie Sausage (in the tofu burger)- contains different dead and alive beans (Xylem and Phloem)
Lower Epidermis- Special, emmental style soya cheese, with holes (stomata) and herb bits (guard cells)
Bottom Waxy Cuticle- Lower Bun
28
What does the top and bottom waxy Cuticle do?
It waterproofs the leaf and reduces water loss. The lower waxy cuticle contains the stomata.
29
What does the upper epidermis do?
literally just protects the cell.
30
What is the role of Palisade Mesophyll?
It is the site of photosynthesis, contains a lot of chloroplasts.
31
What is the role of Spongy Mesophyll?
Increases the surface area of the cell, as it contains many air pockets, and circulates the gas.
32
What is the role of the Vascular Bundle?
Contains Xylem and Phloem tissue, to transport water and minerals. It is running through the spongy mesophyll.
33
What is the role of the lower epidermis?
Contains the guard cells and stomata, so is essential for gas exchange. It also protects the cell.
34
What is the role of the stomata?
Where uptake of gases from the air occurs. It does this due to the two guard cells beside it opening and closing.
35
How does the guard cell open and close the stomata?
If the two guard cells on either side of the stomata are turgid, the stomata will be open.
36
What is the role of the stomata?
Where uptake of gases from the air occurs. It does this due to the two guard cells beside it opening and closing.
37
How does the guard cell open and close the stomata?
If the two guard cells on either side of the stomata are turgid, the stomata will be open.
38
what are three reasons that Humans need such a large volume of Oxygen to be taken up by the lungs?
Because we are large organisms, we have many living cells that require the oxygen
Because we maintain a relatively high body temperature, so we have high metabolic/respiratory rates.
39
How thick is the wall of each alveolus? Why is this helpful?
The wall of each alveolus is never more than 0.3μm. This allows the diffusion pathway between the air in the lungs and the blood in the capillaries to be very short.
40
How many alveoli are there in each lung? How is this useful?
There are 3 million alveoli in each lung. This creates a very large surface area, so a smaller surface area to volume ratio, which increases the rate of diffusion. The mount of area for gases to diffuse across is useful.
41
What is the total surface area of alveoli in the lungs?
70㎡
42
How are the capillaries useful for diffusion from the alveoli (aside from the obvious reasons)?
Each alveolus is covered by a dense network of pulmonary blood capillaries. As deoxygenated blood flows through these capillaries, and the air in the alveoli is oxygenated, this helps create a concentration gradient. They also help create a large surface area.
43
Where do the pulmonary capillaries surrounding the alveoli run to/from?
they either lead to the pulmonary artery or the pulmonary vein. The capillaries carrying deoxygenated blood lead to the pulmonary artery (go away from the heart), while the capillaries carrying the newly fortified blood lead to the pulmonary veins (go towards the heart).
44
How do red blood cells function in a way that encourages gas exchange in the alveoli?
As the red blood cells from the pulmonary artery/vein pass through the capillaries on the alveoli, they slow down, allowing them to spend more time in the capillaries, resulting in more diffusion.
45
What is inspiration?
breathing in
46
What is expiration?
breathing out
47
What role does the diaphragm play in inspiration?
The diaphragm contracts and moves downwards.
48
What role do the external intercostal muscles play in inspiration?
The intercostal muscles (muscles between the ribs) contract, causing the ribcage to move up and out.
49
How is air sucked into the lungs during inspiration?
When the diaphragm contracts and move downwards and the intercostal muscles cause the ribcage to move up and out, the volume of the lungs increases, causing there to be an excess of empty volume, so the air pressure decreases, so in order to reinstate the air pressure, air is drawn in.
50
How is water used in the alveoli structure?
The inner surface of the alveoli has a thin layer of water on it. This makes sure that the surface the gases diffuse across is always moist, so any gases can be dissolved before entering the bloodstream.
51
What role does collagen play in the alveolus structure?
Alveoli are surrounded by a collagen cable. This allows the alveoli to stretch and shrink back to shape, which assists in pulling in and pushing out air.
52
what do the salivary glands do?
They secrete saliva to help lubricate the food for mastecation and digestion. They also produce salivary amylase.
53
what does the stomach do?
It stores and digests food. It especially breaks down proteins, as the stomach's contents has a low pH, so the acid easily breaks up the protein. It has sphinctor muscles at each end to allow it to open for food and keep the stomach acid inside when closed.
54
what does the pancreas do?
The pancreas is a large gland that secretes pancreatic juice which helps digest food after it leaves the stomach. The pancreas contains proteases, lipases and pancreatic amylase.
55
what is peristalsis?
The process by which food moves through the digestive system by the contraction of muscles.
56
What is bolus of food?
food after it is passed through the digestive system.
57
What does bile do?
Bile neutralises the hydrochloric acid in the stomach and contain bile salts that emulsify lipids. It is secreted from the gall bladder.
58
what does the ileum do?
secretes digestive enzymes and has a massive surface area due to the epithelial tissue lining being covered in villi (that are covered in micro-villi).
59
what does the large intestine do?
It absorbs water, in order to re-absorb the water released by digestive enzymes.
60
How is the saliva important for breaking down carbohydrates?
The saliva contains salivary amylase. In the breakdown of carbohydrates through the digestive system, this amylase breaks down starch into maltose ( a disaccharide).
61
How is the pancreas important for breaking down carbohydrates?
Pancreatic amylase is secreted by the pancreas into the ileum. When maltose molecules pass through the ileum, this pancreatic amylase breaks down the maltose into alpha glucose.
62
How are alkaline salts used in the digestion of carbohydrates?
Alkaline salts are secreted into the pancreatic juice in order to make sure that the pancreatic amylase that digests carbohydrates in the digestive system is in an environment with the correct pH.
63
How do lipases digest lipids?
By breaking the ester bonds.
64
What products are made when lipases break down lipids?
The lipid (usually a triglyceride) releases fatty acids and monoglycerides (in the case of triglycerides, two fatty acids and a monoglyceride)
65
What are monoglycerides?
Monoglycerides are a glycerol molecule bonded to a single fatty acid.
66
How are bile salts used in lipid digestion?
Bile salts emulsify the lipids, meaning they break the lipids into micelles. This allows the lipases to work more effectively on the fat.
67
What enzyme breaks down proteins?
Peptidases
68
Name two carbohydrases
Salivary amylase and pancreatic amylase
69
What are the three different types of peptidases?
Endopeptidases, exopeptidases and dipeptideases
70
What do endopeptidases do?
They break down peptide bonds in the control region of the protein, creating smaller polypeptide chains.
71
What do exopeptidases do?
They hydrolyse the peptide bonds between the peptide molecules in the peptide chain.
72
What do dipeptideases do?
They hydrolyse the peptide bonds in the dipeptide molecules separated from the polypeptide chains by exopeptidases to release amino acids.
73
Why are dipeptidases different from endopeptidases and exopeptidases?
Dipeptidases are membrane bound. They are attached to the epithelial cells on the wall of the ileum.
74
What is the basic structure of a villus?
The outer epithelial cells cover the villus, creating a barrier. This encases a lacteal surrounded by capillaries that absorb glucose and amino acid.
75
What does the lacteal do?
The lacteal absorbs fatty acids and glycerol from digestion. They are lymphatic vessels.
76
How are micelles from triglycerides transported in the epithelial cells in the ileum?
The micelles diffuse across the cell surface of the epithelial cells in the ileum. They are then taken to the endoplasmic reticulum of the epithelial cells and are reassembled into new triglycerides. These are then transported into the golgi apparatus, where they associate with cholesterol and lipoproteins to for chylomicrons. These are then ejected out of the cell and into the lacteal via exocytosis in order to later be absorbed into the bloodstream.
77
Name four features of red blood cells
They are flexible in order to allow them to fit through capillaries
They are missing a nucleus to allow more room for oxygen
It is bi-concave, to create a larger surface area and increase absorption
They are stored in the bone marrow
78
What is the structure of haemoglobin? (ions, chains and shape)
The globular protein has a quaternary structure, with four polypeptide chains and containing four iron ions.
79
How is haemoglobin used in red blood cells?
It is the molecule in red blood cells that allows for the cell to carry respiratory gases (like oxygen).
80
How is haemoglobin specialised for oxygen storage?
Haemoglobin has an affinity for oxygen, it can carry four oxygen molecules, as they can easily bind to the four iron ions haemoglobin carries.
81
How are concentration gradients used in the passage of oxygen into the haemoglobin of red blood cells?
Oxygen can move from the lungs to the blood plasma to the red blood cells because of a concentration gradient (lower concentration in the red blood cells). In order to maintain this oxygen is stored in the red blood cells as oxyhaemoglobin, as the oxygen binds to the haem group of the haemoglobin. Therefore, their is oxygen in the blood plasma and oxyhaemoglobin in the red blood cell, so the concentration gradient is still maintained.
82
How does oxygen bind to haemoglobin?
The oxygen binds to the iron ions in the "haem" group of the haemoglobin.
83
What is pO2?
The amount of oxygen in the lungs is referred to as it's partial pressure for oxygen (pO2) or it's oxygen tension.
84
How does pO2 relate to oxygen absorption?
When the pO2 is high, more oxygen and haemoglobin come in contact. Therefore, the higher the pO2, the more oxyhaemoglobin is created.
85
What is the pO2 like in respiratory tissue?
The pO2 is low
86
what happens to haemoglobin at a low pO2?
At a low pO2, oxygen dissasociates from the haem group of oxyhaemoglobin and releases oxygen (e.g. in respiring tissue). At low pO2, lots of oxyhaemoglobin is formed at high pO2, oxyhaemoglobin is broken down.
87
What occurs during diastole of the heart?
Blood fills the atria from the pulmonary vein and the vena cava. Therefore, the pressure in the atria increases. The atrioventricular valves open when the pressure in the atria reaches a certain threshold, causing the blood to naturally drop into the ventricles due to gravity. At this point, the semi-lunar valves are closed.
88
What occurs during Atrial systole?
(after diastole causing the atria to fill up with blood, and the atrioventricular valves have closed) The atrial walls contract, the atrioventricular valves open and blood flows into the ventricles (whose walls are relaxed at this point) T this point, the semi-lunar valves are closed, in order to prevent backflow.
89
What occurs during Ventricular Systole?
The ventricle walls contract, after blood has been pumped into them during atrial systole (so the atrioventricular valves are now closed to prevent backflow into the atria). This causes pressure to build up in the ventricles. Once the amount of pressure in the ventricles exceeds the amount of pressure in the aorta and pulmonary artery, the blood is pushed into these arterial vessels via the muscular ventricle wall.
90
What is the role of the Vena Cava?
The vena cava brings blood to the heart. Specifically it brings deoxygenated blood to the heart from all respiratory tissues (except the lungs). It supplies blood to the right atrium. The vena cava can also contain pocket valves.
91
What is the role of the Aorta?
The aorta is one of the main arteries in the body. It carries blood from the left ventricle to arterioles travelling to respiring tissue. They contain semi-lunar valves to prevent backflow.
92
What is the role of the Pulmonary Vein?
The pulmonary veins are connected to the left atrium. They bring oxygenated blood from the lungs to the heart. The actual structure of the vein is similar to that of the vena cava (same layers of tissue as the artery, but with thinner elastic and muscular layers and a wider lumen). They are supplied with oxygenated blood from the capillaries in the alveoli, and can contain pocket valves.
93
What is the role of the Pulmonary Artery?
The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs. It has similar structure to the Aorta (tough and fibrous outer layer, thick muscular walls, thick elastic walls and endomorphic layer with small lumen).
94
Where can we find the right atrioventricular valve?
Between the right atrium and the right ventricle.
95
Where can we find the left atrioventricular valve?
Between the left atrium and the left ventricle.
96
What are the walls of the right and left atrium like?
The walls of the atria are quite thin and elastic. These allow them to stretch and contract as they collect blood.
97
What is the difference between the walls of the left and right ventricle?
The left ventricle has much thicker, more muscular walls, as it must pump blood at high pressures into the aorta, in order for the blood to reach everywhere in the body, including extremities.
98
What is the general structure of an artery?
The arteries have thick muscular walls, thick elastic walls, a thin and smooth layer (to reduce friction and allow smoother blood flow) and a small lumen. The muscular walls allow the arteries to contract to push blood through the vessels. The small lumen is used to maintain high pressure. The arteries can contain arterial valves (such as the semi-lunar valves in the aorta), but usually just in the heart.
99
What is the general structure of a vein?
They have similar structure to the arteries, but have thinner muscular and elastic walls, as well as a larger lumen. Thy therefore do not contract as much, and have lower pressure within the vessels, so contain valves to prevent backflow (such as pocket valves).
100
What is the general structure of a capillary?
Capillaries are small vessels, with walls that are only one cell thick. They are highly branched and have small pores in their walls, called endothelial cells. This is so plasma can leak out of these pores (which is one way the pressure remains so low in the capillaries).
101
What is tissue fluid?
Tissue fluid is a watery liquid that contains glucose, amino acids, fatty acids, ions and oxygen. Tissue fluid carries these substances TO the tissues and carries away carbon dioxide and other waste material.
102
How can hydrostatic pressure result in tissue fluid?
The pumping of the heart can cause the capillaries to have high, hydrostatic pressure. In order to combat this, blood plasma leaves the capillaries via pores. This blood plasma contains tissue fluid. (However, this outward force created by the hydrostatic pressure is contested by hydrostatic pressure outside the capillaries and the water potential gradients).
103
What do the ends/walls of the tubular phloem tissue made out of?
Sieve plates
104
What are the branch-like structures in the lumen of phloem tissues?
Sieve tube elements
105
What is one weakness of sieve tube elements?
SIeve tube elements can not keep themselves alive as they can not respire for themselves, so have to be aided by companion cells which respire for them.
106
What do phloem tissues transport?
Phloem tissue transports solutes (carbohydrates such as sucrose) made in the sources to the sink cells.
107
What type of transport is phloem tissue involved in?
translocation
108
What two substances (solutes) can be transported in translocation?
```
soluble carbohydrate (such as sucrose)
Hormones
```
109
What are the two things that ensure that translocation occurs FROM the source cells TO the sink cells?
```
Concentration gradient (there is always a high concentration of the solute in the source cells than in the phloem vessel or the sink cells)
Pressure-
```
110
What is a potometer?
An apparatus used to measure the the rate of transpiration
111
Why is it unexpected that xylem cells are so strong? What makes them strong?
They are dead, empty cells, so would be expected to be weak, but they are strengthened with lignin.
112
What occurs in the mesophyll cells during transpiration?
The water vapour accumulates in the spongy mesophyll tissues/air sacs in the leaves. This vapour then leaves he cell via the stomata, once they open. The water in the leaves is then replaced by water drawn up the plant by the xylem cells.
113
What is cohesion?
A force resulting from attraction between molecules of the same substance- e.g. between the negative and positively charged ions in different water molecules, causing them to stick together.
114
What is adhesion?
A force resulting in attraction between molecules of different substances, like when water molecules stick to the cell walls of the wall of the cells that make up xylem tissue.
115
How are cohesion and adhesion important in the theory of transpiration pull/the cohesion-tension theory?
Water is drawn up and out of the xylem vessels, ou of the stomata. The tension therefore creates a water-potential gradient, drawing more water up the vessel. The water is drawn up continuously, due to cohesion between the molecules, and the water does not drop down the vessel (as gravity would suggest) due to adhesion between te water molecules and the vessel walls,
116
What evidence is there to support the idea of cohesion-tension theory?
- Changing rates of transpiration can cause the diameter of the trunks, resulting in expansion due to the pressure of water in the xylem tubes
- If a xylem vessel is broken and air enters it, the tree can no longer take up water.
- When a xylem vessel is broken, it does not leak. If the movement of the water was just due to pressure, the water would be expected to leak, and the lack of leakage shows that water movements is more because of cohesion-tension.
117
How is tension created in transpiration?
When water is released out the stomata, it creates tension (negative pressure). This creates a lower water potential at the end of the xylem (before the stomata), which creates a water potential gradient that draws the water up the plant.
118
briefly describe how one would use a potometer to test the rate of transpiration
The potometer is filled completely with water, ensuring there are no air bubbles.
A leafy shoot is fitted inside it whilst still submerged in water.
An air bubble is introduced into the capillary tube
As the water is transpired out of the plant, the bubble will be moved along the capillary tube. The distance moved indicates the rate of transpiration.
119
What is the definition of forced expiratory volume?
maximum volume of air that can be breathed out in one second.
120
What is the definition of tidal volume?
It is the volume of air in each breath
121
What happens at the arterial end of a capillary to produce tissue fluid?
Water moves out of the capillary, glucose and oxygen move out of the capillary and hydrostatic pressure inside the capillaries is higher than the hydrostatic pressure in the tissue fluid.
122
Describe what happens at the venous end of a capillary to cause tissue fluid to re-enter the capillary
The water potential inside the capillaries is lower than the water potential in the tissue fluid
carbon dioxide and urea move into the capillary
water moves into the capillary
123
where are bile salts produced?
In the liver
124
If an organism lives at a high altitude, what would the dissociation curve and haemoglobin be like?
The dissociation curve would shift to the left
haemoglobin will have a higher affinity for O2
Oxygen will bind more easily
125
Where are membrane-bound disaccharidases found?
In the epithelial cells lining the ileum
126
What would the dissociation curve and haemoglobin be like in an organism with a high surface area to volume ratio?
The dissociation curve would shift to the right
haemoglobin will have a lower affinity for O2
Oxygen will dissociate more easily
127
What three conditions are usually present in the lungs when oxyhaemoglobin has been formed?
High PO2
High affinity
High oxygen concentration
128
What happens during exhalation?
The internal intercostal muscles contract
The external intecostal muscled relax
the volume of thorax decreases
Ribcage moves down and inwards
Diaphragm relaxes and moves upwards
The pressure of the thorax decreases
129
what is the correct order of structures in fish?
Gill Arch--Gill Filaments---Lamallae-- Capillaries
130
131
what happens during inhalation?
The external intercostal muscles contract
The pressue of the thorax decreases
The volume of the thorax increases
diaphragm contracts and moves down
ribcage moves up and outwards
132
What is the general structure of arteries?
they carry blood away from the heart
They have thick walls with lots of muscle and elastic tissue to allow to stretch and coil
narrow lumen
they have a folded inner lining (endothelium) which allows the vessels to stretch
133
What are 5 adaptations of xeropytes?
Thick waxy cuticle
fewer stomata
rolled leaves
stomata found in pits
layers of hair on the epidermis
134
what are 4 features of the structure of veins?
wide lumen
carry blood to the heart
thin walls with less muscle and elastic tissue
contain valves
135
what is the equation for pulmonary ventilation rate?
tidal volume x breathing rate
136
what happens at the arterial end of the capillary to produce tissue fluid?
Hydrostatic pressure inside capillaries is higher than the hydroatatic pressure in the tissue fluid
glucose and oxygen move out of the capillary
water moves out of the capillary
137
138
Why does water diffuse out of the stomata, even if it is a humid day?
As though the atmosphere is humid, the air outside the stomata is usually dry, creating a water potential gradient
139
How does the xylem interact with mesophyl cells?
water is lost from mesophyl cells by evaporation from their cell walls as of heat supplied by the sun. These mesophyll then accept water from neighbouring cells, via osmosis, that have been supplied with water by xylem vessels.
140
Briefly summarise the method of transpiration
water evaporates from mesophyll cells
water is drawn up the xylem to replace this and due to cohesion this water forms one long column
This is calles the transpiration pull
as there is tension at the end of the vessel, transport continues
141
What is a source in a plant?
the site where sugars are produced due to photosynthsis
142
What are sinks?
Where sugars are stored for suture use
143
What is the process in which sugars are transported into the sieve tube elements?
Co transport
144
What occurs in the co transport from the companion cells into the sieve tube elements?
Hydrogen ions are actively transported into the seive tube elements. This creates a concentration gradient, so hydrogen ions then diffuse down a conentration throuhg carrier proteins into the sieve tube elements. Sucrose is transported with these ions.
145
How is mass flow of sucrose through sieve tube elements created?
The active transport of sucrose into seive tube elements creates a lowerwater potential
The xylem has a high water potetial so water will travel from the xylem to the phloem via osmosis
At the sink cells, sucrose is used up, so sucrose is actively transported into these cells to replace this. This then lowers the water potential, so water travels into these cells from the sieve tube elements.
Therefore the hydrostatic pressure of the sieve elements is lowered
Therefore, there is high hydrostatic pressure at the source and low hydrostatic pressure at the sink
The sucrose therefore travels down this hydrostatic gradient
146
147
What is the question mark indicating?
Whay are these necessary?
Companion cells
As phloem cells do not have mitochondria, so they can not respire for themselves, so they have the companion cells respire for them.
148
What is the question mark indicating?
How does this interact with companion cells?
The source cells
It moves hydrogen ions and sucrose into the companion cells via facilitated diffusion
149
What is the question mark indicating?
What is the sucrose concentration and water potential like here?
The sink cells
The sucrose is being used up in respiration, so the sucrose concentration is lower. Therefore, the water potential is more positive.
150
What are the red dots indicating?
Hydrogen ions and sucrose (both of them travel together)
151
What is the water potential like at at point A and at point B?
Why?
What does this mean about the hydrostatic pressure?
At point A, the water potential is very low, as there is a large concentration of sucrose that has been transported to the phloem from the source and companion cells.
At point B, there is a high water potetnial, as the sucrose has been used up by respiration in the sink cells.
Therfore, water moves to point A by osmosis and water moves away from point B by osmosis, so the hydrostatic pressure at A becomes high and the hydrostatic pressure at B becomes low.
152
How does the sucrose move into the sink cells? How does this affect osmosis and hydrostatic pressure?
Sucrose is actively transported into the sink cells from the sieve tube elements. The sink cells respire, so they have sufficient ATP to do this.
This decreases the water potential of the cell, so causes water to move into it via osmosis. This therefore increases the hydrostatic pressure of the sink cell and the sieve tube elements next to it.
153
How can we use tracers to investigate translocation?
* Radioactively label CO2
* This is absorbed into the plant and used to make sugars via photosynthesis
* Thin slces of stems are then placed on x ray film that turns black when exposed to radioactive material
* The areas containing sugars turn black, showing where and if translocation occurs.
154
How can we use a ringing experiment to give evidence for translocation?
* A ring of bark and phloem is removed from a tree
* The area above this section swells up with liquid
* This area contains sugars, as we can see when we remove and analyse it
* therefore, when the phloem is removed, the sugars can not be transported, so proves the use of phloem in transpiration
155
Why does pressure build up quicker in the ventricles than in the atrium?
The walls of the ventricles are thicker than the walls of the atrium, so the ventricular pressure is always higher than the arterial pressure.
156
What is the pressure like in arteries? Why?
High, due to the thick elastic walls
157
What happens in atrial systole?
The atria contract, causing the pressure in the atria to increase. As the atrioventricular valve is open, blood drops into the ventricles as well. The pressure in the ventricles then increases until it exceeds the pressure in the atria, so the atrioventricular close.
158
What happens in ventricular distole?
As the atrioventricular and semi lunar valves are closed, the pressure in the ventricles builds up. The ventricles then contract, causing the pressure to build up even more. Eventually, the pressure in the ventricles will exceed the pressure in the arteries, causing the semi lunar valves to open and casuing blood to flow into the arteries.
159
What happens (relating to transport) to cause stomata to open?
Potassium ions are pumped into the stomata causing water to then move into the stomata and make it more turgid, so the stomata opens.
160
What does the graph relating to the Bohr Effect look like?
It looks like this dumbass
161
How is foetal haemoglobin different from normal haemoglobin?
It has a higher affinity for oxygen
162
How do increasing CO2 concentration and temperature affect the curve of a haemoglobin saturation graph?
It decreases the haemoglobin's affinity for oxygen and therefore causes the curve to move to the right.
163
How does decreasing the pH of haemoglobin affect curve on a haemoglobin saturation graph?
It decreases the haemoglobin's affinity for oxygen and therefore causes the curve to move to the right.
164
