Exchange of Substance Flashcards
1
Q
State the relationship between size and surface area to volume ratio of an organism and how it affects the rate of diffusion.
A
Smaller organisms have a larger surface to volume ratio, therefore has a shorter diffusion pathway.
2
Q
State why smaller organisms have a higher metabolic rate.
A
Smaller organisms have a larger surface area to volume ratio, so there is more heat loss and faster rate of respiration/metabolism, which releases heat.
3
Q
Why can’t insects exchange substances through their body surface?
A
They have a waterproof exoskeleton and a small surface area to volume ratio, in order to conserve water.
4
Q
Name the 3 main parts of the insect exchange system.
A
- Spiracles
- Tracheae
- Tracheoles
5
Q
Explain the process of gas exchange in insects.
A
Gases move in (oxygen) and out (carbon dioxide) of the tracheae via spiracles.
Oxygen diffuses down a concentration gradient through tracheae to tracheoles which lead to respiring tissue, whilst waste carbon dioxide diffuses out .
Contraction of muscles in the tracheae allow gases to move in and out.
6
Q
Name 3 adaptations of the insect gas exchange system and how they provide sufficient gas exchange.
A
- Tracheoles have thin permeable walls –> short diffusion pathway.
- Many branches –> increase surface area for carrying gases.
- Tracheae tubes are lined with chitin –> strengthens tubes so can withstand pressure.
7
Q
Name 3 ways insects can control water loss.
A
- Insects can close spiracles to conserve water.
- They have a waterproof waxy cuticle exoskeleton to reduce evaporation.
- They have hairs in spiracles to prevent water leaving.
8
Q
Explain abdominal pumping in insects.
A
- Abdominal pumping/pressure in tubes linked to carbon dioxide release.
- (Abdominal) pumping raises pressure in body.
- Air/carbon dioxide pushed out of body /air/carbon dioxide moves down pressure gradient (to atmosphere).
9
Q
Name 2 parts of the fish gas exchange system.
A
- Gill filaments
- Lamellae
10
Q
Explain two ways in which the structure of fish gills are adapted for efficient gas exchange.
A
- Many lamellae –> large surface area for oxygen uptake.
- Thin surface –> short diffusion pathway.
11
Q
Explain counter-current flow in gas exchange across a fish gill.
A
- Water and blood flow in opposite directions.
- Blood always passing water with a higher oxygen concentration.
- Diffusion/concentration gradient (maintained) along (length of) lamella/filament.
12
Q
Name the 8 parts of a leaf.
A
- Waxy cuticle
- Palisade mesophyll
- Spongy mesophyll
- Guard cells
- Stomata
- Lower epidermis
- Upper epidermis mesophyll
- Upper epidermis
13
Q
Why do stomata open during the day?
A
To allows gas exchange to occur.
14
Q
Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf.
A
Carbon dioxide enters via stomata, stomata opened by guard cells and diffuses through air spaces down diffusion gradient.
15
Q
Describe & explain an advantage of having a higher stomatal density.
A
More carbon dioxide uptake so there is more photosynthesis so faster/more growth.
16
Q
Describe & explain an disadvantage of having a higher stomatal density.
A
More water loss/transpiration, less photosynthesis so slower/less growth.
17
Q
Name 6 adaptations of desert plants.
A
- Hairs so ‘trap’ water vapour and water potential gradient decreased.
- Stomata in pits/grooves so ‘trap’ water vapour and water potential gradient decreased.
- Thick (cuticle/waxy) layer so increases diffusion distance.
- Waxy layer/cuticle so reduces evaporation/transpiration.
- Rolled/folded/curled leaves so ‘trap’ water vapour and water potential gradient decreased.
- Spines/needles so reduces surface area to volume ratio.
18
Q
Describe the pathway that air takes into the lungs for human gas exchange.
A
Air enters the trachea, which splits into two bronchi, then many bronchioles then alveoli, where gas exchange occurs.
19
Q
State 4 adaptations of alveoli.
A
- There are many alveoli => so there is a large surface area.
- Alveolar epithelium and capillary endothelium are just one cell thick => short diffusion pathway.
- Many capillaries close to alveoli => maintain good bloody supply and steep concentration gradient.
- Well ventilated => bring (fresh air) O2 to the surface and take CO2 (stale air) away and maintain a steep concentration gradient for O2 and CO2.
20
Q
Define ventilation.
A
To maintain the diffusion of gases across the alveolar epithelium, air must be constantly moved in and out of the lungs.
21
Q
Describe the process of ventilation.
A
The diaphragm and internal/external intercostal muscles contract to change the volume of the thorax, so changing the air pressure.
Air always moves from higher to lower air pressure.
22
Q
Describe the mechanism of inspiration (breathing in).
A
- External muscles contracts and diaphragm contracts and flattens.
- Ribs move upwards and outwards.
- Volume of the thorax increases .
- Air activity in thoracic cavity decreases below atmospheric pressure.
- Airs moves into lungs down pressure gradient.
23
Q
Describe the mechanism of expiration (breathing out).
A
- Internal intercoastal muscles contract and diaphragm relaxes into a dome shape.
- Ribs move downwards and inwards.
- Volume of the thorax decreases.
- Air pressure in thoracic cavity increases above atmospheric pressure.
- Air moves out of lungs down pressure gradient.
24
Q
What occurs during forced expiration?
A
- Internal intercostal muscles contract, pulling the rib cage further down and in.
- External intercostal muscles relax.
25
Define tidal volume.
Volume of air in each breath.
26
Define ventilation rate.
Breaths per minute.
27
Define forced expiratory volume.
Maximum volume of air that can be breathed out in 1 second.
28
Define forced vital capacity.
Maximum volume of air breathed out forcefully after a deep breath.
29
Give a description of pulmonary tuberculosis.
Bacterial infection.
The immune system builds hard tubercles around bacteria in the lungs which damages gas exchange around the surface.
30
Give a description of cystic fibrosis.
After exposure to asbestos or dust.
Thick non-elastic scar tissue forms.
31
Give a description of asthma.
Airways are irritated and inflamed.
Smooth muscles lining the bronchioles contracts and more mucus is produced.
32
Give a description of emphysema.
Caused by smoking or air pollution as particles are trapped in the alveoli.
Inflammation attracts phagocytes, and enzymes break down the elastin in the alveolar wall.
Alveoli can not now recoil.
33
In pulmonary tuberculosis, give an example of the effect on lung function.
Tidal volume is reduced.
34
In asthma, give an example of the effect of lung function.
Air flow is severely reduced so forced expiratory volume is reduced.
35
In cystic fibrosis, give 2 examples of effect on lung function.
1. Tidal volume and forced expiratory volumes is reduced.
2. Gas exchange is reduced as diffusion distance across scar tissue is longer.
36
In emphysema, give 2 examples of the effect on lung function.
1. Destruction of alveolar walls reducing the surface area for gas exchange.
2. Increase ventilation rate to compensate.
37
What occurs during digestion.
Large molecules are hydrolysed into smaller molecules that can be absorbed across a cell membrane.
38
Describe carbohydrate digestion thoroughly.
1. In the mouth, salivary amylase hydrolyses glycosidic bonds in starch to form maltose.
2. Amylase is produced in the salivary glands, which is released into the mouth.
3. Amylase is also produced by the pancreas and released into the small intestine.
4. In the small intestine, membrane-bound disaccharidases are attached to the membranes of epithelial cells in the ileum. They break down disaccharides into glucose.
39
Describe lipid digestion thoroughly.
1. Lipids are hydrolysed to monoglycerides, and fatty acids catalysed by lipase.
2. Lipases are made in the pancreas and work in the small intestine.
3. Bile salts produced by the liver emulsify large droplets of lipids into smaller droplets with a larger surface area for lipases to work on.
4. The monoglycerides and fatty acids form micelles with bile salts.
40
What are the function of micelles? And a property of them.
Micelles are vesicles which deliver fatty acids, glycerol and monoglycerides to epithelial cells of the ileum for absorption.
They are water soluble.
41
Describe protein digestion thoroughly.
1. Proteins are hydrolysed by 3 protease enzymes : endopeptidase, exopeptidase and dipeptidases into amino acids.
2. Endopeptidases hydrolyse bonds within a protein and are either produced by the stomach or pancreas and released into the small intestine.
3. Exopeptidases, produced by the pancreas and secreted into the small intestine, hydrolyse the bonds at the end of proteins to remove single amino acids.
4. Dipeptidases are located on the cell surface membrane of the epithelial cells in the small intestine and separate dipeptides into two amino acids.
42
How can lipid digestion be measured?
Lipid digestion can be measured by the change in pH. As lipids are hydrolysed the fatty acids make the solution more acidic. The faster the change in pH, the faster the hydrolysis of lipids.
43
The action of endopeptidases and exopeptidases can increase the rate of protein digestion. Describe how.
1. Exopeptidases hydrolyse peptide bonds at the ends of a polypeptide and endopeptidases hydrolyse internal peptide bonds within a polypeptide.
2. More surface area.
44
State 3 adaptations of the ileum for rapid absorption.
1. The ileum is very long and is folded into structures called villi => this increases surface area for absorption.
2. Each villus has a good capillary network, and a network of tubes called a lacteal which is part of the lymph system. Both rapidly remove absorbed molecules, maintain a steep concentration gradient.
3. The lining of the ileum is made up of one layer of epithelial cells and the capillaries are one layer of endothelial cells => this ensures a short pathway for absorption.
45
State 4 adaptions of the epithelial cells.
1. The cells have folds in the membrane called microvilli, further increasing the surface area.
2. The membrane has more protein channels and carriers for the active transport, facilitated diffusion and co-transport.
3. The cell contains more mitochondria for more ATP production, allowing more active transport and co-transport.
4. The cell has more ribosomes, rough endoplasmic reticulum and golgi body's for protein synthesis and modification, to produce more membrane proteins.
46
How are monosaccharides and amino acids absorbed in digestion?
They are taken up by co-transport.
47
How are monosaccharides and amino acids taken up by co-transport.
1. Na+ is actively transported out of the ileum cell into the blood. This lowers the concentration inside the cell and produces a concentration gradient.
2. Na+ diffuses down the concentration gradient through a protein and it brings glucose with it by co-transport.
3. Glucose moves out of the cell by facilitated diffusion due to its concentration gradient. It then diffuses into the capillary.
48
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels.
1. Micelles contain bile salts and monoglycerides.
2. Makes monoglycerides soluble in water.
3. Monoglycerides are absorbed by diffusion.
4. Triglycerides are reformed in the SER in cells.
4. The golgi produces chylomicrons from triglycerides and proteins.
5. The chylomicrons are exported via vesicles by exocytosis.
6. Chylomicrons are absorbed into the lacteals in the villi.
49
Define haemoglobin.
A quaternary protein that carries oxygen around the body.
50
Define oxyhaemoglobin.
When oxygen has bound to haemoglobin.
51
Define associate in terms of haemoglobin.
When oxygen binds to haemoglobin (loading).
52
Define dissociate in terms of haemoglobin.
When oxygen leaves oxyhaemoglobin (unloading).
53
Define affinity in terms of haemoglobin.
How readily oxygen associates to haemoglobin. Changes under different circumstances.
54
Define partial pressure in terms of haemoglobin.
The pressure created by a gas in a specific space.
55
How many chains does haemoglobin have?
4
56
In terms of haemoglobin, describe the co-operative nature of oxygen binding.
First molecule of oxygen to bind to haemoglobin causes a change in the quaternary structure (shape), this uncovers other binding sites making the binding of further oxygens easier.
57
When is oxygen loaded and unloaded from haemoglobin.
At high O2 partial pressures, oxygen is loaded/associated.
At low O2 partial pressures, oxygen is unloaded/disassociated.
58
What is the shape of the oxygen dissociation curve?
Sigmoidal.
59
Why do different animals have different shapes of haemoglobin.
The different shapes are due to different genes (different order of bases) coding for different amino acid sequences. This results in different primary sequences and therefore, different tertiary shapes.
60
What does it mean when the oxygen dissociation curve is to the left?
Haemoglobin has a higher affinity for oxygen.
Haemoglobin loads more readily and can be saturated at lower O2 partial pressures.
Oxygen can be supplied to respiring tissues.
61
Define the Bohr Shift?
The effect of carbon dioxide on the affinity of haemoglobin ; the more carbon dioxide the lower the affinity of haemoglobin for oxygen.
62
Describe the dissociation curve of oxygen when carbon dioxide is present.
1. Carbon dioxide causes the curve to shift the curve to shift to the right.
2. The haemoglobin's affinity for oxygen reduces.
3. Oxygen dissociates from haemoglobin more readily.
4. More oxygen is unloaded to tissues for aerobic respiration.
63
What are arteries?
Is blood carried under high or low pressure?
Arteries take blood away from the heart to the rest of the body.
Blood is carried under high pressure.
64
What are veins?
Is the blood carried under high or low pressure?
Veins return blood back to the heart.
Blood is carried under low pressure.
65
What are capillaries?
Connect arteries and veins, site of exchange.
66
What are coronary arteries?
Coronary arteries supply the heart muscle with blood, they are found on the heart.
67
1. What is the wall like in an artery, why?
2. Is there endothelium present, if so what is it like and why?
3. What is the lumen like and why is it like that?
4. What is the elastic content in arteries and what does that enable arteries to do?
5. Are there valves in arteries?
6. What is the pressure like in arteries?
1. The wall of an artery is thick and muscular in order to withstand pressure.
2. Endothelium is present but it's folded in able to stretch.
3. The lumen is narrow so a high pressure is maintained.
4. The elastic content in arteries is high in order to stretch and recoil.
5. Arteries do not have valves except for aorta and pulmonary artery.
6. The pressure in arteries is high due to elastic recoils of walls. The pressure decreases the further from the heart.
68
1. What are the walls like in veins?
2. Is the endothelium present in veins, if so what is it like?
3. What is the lumen like?
4. What is the elastic content like in veins?
5. Are there valves in veins?
6. What is the pressure of blood in the veins like?
1. Walls are thin.
2. The endothelium is present and not folded.
3. The lumen is wide.
4. The elastic content of the veins is low.
5. There are valves in the veins.
6. The pressure of blood is low in the veins.
69
State features of capillaries' structure that contribute to rapid diffusion.
1. Small diameter -> takes blood as close as possible to cells for rapid transfer, so there is a short diffusion pathway.
2. The endothelium layer is one cell thick, short diffusion pathway.
3. Narrow lumen -> reduces diffusion distance.
4. Capillary pores -> allow some substances to leak through walls, reducing pressure.
70
Explain the formation of tissue fluids in the arteriole end.
1. The hydrostatic pressure of blood is high at arterial end due to contraction of the left ventricle.
2. Water and soluble molecules are forced out of the capillary, such as amino acids, salt ions and glucose.
3. This reduces the volume of blood and therefore the pressure in the capillary.
4. Plasma proteins and large molecules remain.
71
Explain how water from tissue fluids is returned to the circulatory system.
1. Plasma proteins and large molecules remain.
2. This lowers the water potential of the blood.
3. Water moves back into veinous end of capillary by osmosis.
4. Lymph system collects any excess tissue fluid which returns to the blood.
72
What is the function of the aorta?
Carries oxygenated blood from the left ventricle to general body.
73
What is the function of the vena cava?
Carries deoxygenated blood back to the right atrium from the body.
74
What is the function of the pulmonary artery?
Carries deoxygenated from right ventricle to lungs.
75
What is the function of the pulmonary vein?
Carries oxygenated blood back to the left atrium from lungs.
76
What is the function of the atrium?
Contracts to force blood into the ventricle.
77
What is the function of the ventricle.
Contracts to force blood into aorta / pulmonary artery.
78
What is the function of the bicuspid valve?
Prevents backflow of blood from the left ventricle to the left atrium.
79
What is the function of the tricuspid valve?
Prevents backflow of blood from right ventricle to right atrium.
80
What is the function of semilunar valves?
Prevents the backflow of blood from arteries to ventricles.
81
What is the function of valve tendons?
Prevents valves from inverting.
82
Define systole.
Contracts.
83
Define diastole.
Relaxes.
84
Describe the process of ventricular diastole (whole heart diastole).
1. Bothe atria and ventricles in heart relax. Pressure drops.
2. Blood fills atria from veins (vena cava / pulmonary veins), this is also referred to as passive refilling.
85
Describe the process of atrial systole.
1. Cardiac muscle in the atria contract.
2. Pressure in the atria increases.
3. Higher pressure in atria than ventricles opening the atrio-ventricular valve.
4. Blood forced into ventricles.
5. Valves in veins stop blood going back into veins.
86
Describe the process of ventricular systole.
1. Ventricles contract from the base upwards, causes increase in blood pressure.
2. Ventricular pressure is higher than atrial pressure shutting the AV valves , preventing backflow into atria.
3. Ventricular pressure higher than aortic pressure, opening the semi-lunar valve.
4. Blood forced through semi-lunar valves into arteries (aorta / pulmonary artery).
87
State 4 risk factors of cardiovascular disease and why?
1. Saturated fats -> increase blood cholesterol.
2. Smoking -> increases blood pressure and heart rate, increases blood clots and causes damage to blood vessels.
3. Alcohol abuse -> increases blood pressure and heart rate. Can also damage heart muscle.
4. Genetics.
88
Define cardiac output.
The total number of blood pumped out by the heart in one minute.
89
Define stroke volume.
The total volume of blood pumped out by the heart in one full cardiac cycle.
90
Define heart rate.
The number of full cardiac cycles in a minute.
91
Name 3 features of a xylem and how they contribute to transport of water and ions.
1. Consists of dead cells -> cells contain lignin which water can adhere to in order to provide strength to the xylem to prevent inward collapse.
2. No end walls -> form a continuous system of tubes of tubes for water transport, allows water to move in a continuous column with no impeded flow.
3. Pits -> allow horizontal movement of water.
92
Define adhesion.
Forces between the water molecules and hydrophilic lining of the xylem walls.
93
Define cohesion.
Force between water molecules forming an unbroken column in the xylem.
94
Define tension.
Pull generated by water evaporation. This creates a negative pressure inside the xylem (pressure is lower inside the xylem than outside it).
95
Define transpiration.
Evaporation of water, as water vapour, from the leaves and shoots of plants. Usually through the stomata.
96
Describe the cohesion-tension theory of water transport in the xylem.
1. Water lost from leaf because of transpiration.
2. This lowers the water potential in leaf cells, establishing a water potential gradient.
3. Water is pulled up xylem, creating tension.
4. Water molecules cohere by hydrogen bonds.
5. This forms a continuous water column.
6. There is also adhesion of water molecules to walls of xylem.
97
When is the rate of transpiration at its highest and what does this create?
Midday.
This creates tension and a water potential gradient. Increases tension means pressure in xylem is lower.
98
State 4 factors affecting the rate of transpiration and how they affect it?
1. Temperature -> more kinetic, so more diffusion of water vapour, lowers water potential, so gradient is steeper.
2. Humidity -> increases in external gradient would lower the gradient.
3. Air movement -> removes the layer of saturated air outside stomata which reduces water potential, so the water potential gradient is steeper.
4. Light intensity -> higher light intensity opens stomata more to allow more carbon dioxide for photosynthesis, therefore transpiration increases.
98
Define translocation.
Mass transport of organic molecules.
99
What is the phloem made up of and what does that mean?
The phloem is made up of living cells, this allows them to produce ATP for sucrose transport.
100
What are sieve tube elements?
They are living cells with no nucleus and just a few organelles so less resistance to flow. Their end walls have perforations in them called sieve plates.
101
What are companion cells?
They are very active cells next to the sieve tubes. Connected to the sieve tubes by plasmodesmata. Lots of mitochondria - provide the energy (ATP) to the sieve tubes for the active movement of sucrose.
102
Describe the processes involved in the transport of sugars in plant cells.
1. At the source, sucrose is actively transported into the phloem.
2. By companion cells.
3. This lowers the water potential in the phloem and water enters by osmosis.
4. This produces a high hydrostatic pressure.
5. Mass flow towards sink cell.
6. At the sink cell sugars are unloaded for respiration or to be stored.
103
In terms of the phloem, what is a ringing experiment and explain why this occurs?
1. Bark is removed from stem to prevent movement of organic substances.
2. A bulge forms above the ring. Fluid above the ring has a higher concentration of sugars, dictating a gradient.
104
Describe how aphids are used to determine mass flow in phloem and explain what this does.
1. Aphids pierce the phloem and are removed just leaving the mouthpart, so sap flows out quicker at the top, indicting a pressure gradient.
2. There is a hydrostatic pressure in phloem causing sap to ooze out. There is no hydrostatic pressure in transport in xylem.
105
Describe autoradiography in terms of mass flow in phloem and explain how it locates the transport of sucrose.
1. A radioactive tracer can be used to track organic substances. Detected using photographic film.
2. The radioactive carbon in carbon dioxide is incorporated in to sucrose by photosynthesis. This occurs at the source and from here sucrose is transported to the sink.
106
Describe metabolic inhibitors and their role in determining mass flow in the phloem.
Metabolic inhibitors stop ATP production by respiration being reduced. ATP is needed in order to unload sucrose from source and to load sucrose into the sink cell.
107
State 3 pieces of evidence contradicting the mass flow hypothesis.
1. Different organic substances flow at different rates.
2. Different substances move in opposite directions.
3. Sieve plates would create a barrier to mass flow.
