exchange of substance Flashcards
(102 cards)
1
Q
what is inspiration
A
breathing in
2
Q
what is expiration
A
breathing out
3
Q
what happens to the external intercostal muscles when u breathe in
A
contract to pull the ribs up and out
4
Q
what happens to the internal intercostal muscles when u breathe in
A
relax
5
Q
what happens to the diaphragm when u breathe in
A
moves down and flattens
6
Q
what happens to air pressure and volume in lungs during inspiration
A
air pressure drops
the volume increases
therefore air moves into lungs as the pressure is higher than the thorax
7
Q
what happens to the external intercostal muscles when u breathe out
A
relax
8
Q
what happens to internal intercostal muscles when u breathe out
A
contract to pull the rib down and in
9
Q
what happens to the diaphragm when breathing out
A
relaxes and moves upwards and domes
10
Q
what is the pressure and volume like in the lungs during expiration
A
the air pressure is greater
the lung volume decreases
therefore air will move out from lungs to the outside as pressure moves from a high to low concentration
11
Q
equation for pulmonary ventilation
A
pulmonary ventilation (dm3min-1) = tidal volume x breathing rate
12
Q
how does an insect perform gas exchange whilst in flight
A
the muscle cells start to respire anaerobically to produce lactate which lowers the water potential of the cells so water moves from the tracheoles to the cells by osmosis. this decreases the volume in the tracheoles so air from the atmosphere is drawn in
13
Q
how do insects adapt to prevent water loss
A
small surface area to volume ratio where water can evaporate from.
insects have a waterproof exoskeleton.
the spiracles (where gases enter and water evaporates from) can open and close to reduce water loss
14
Q
how can you calculate rate of diffusion
A
surface area x difference in conc / length of diffusion pathway
15
Q
what is a gill filament
A
they make up the stacks of gills and are covered in gill lamellae to create a large surface area
16
Q
how are fish adapted to gas exchange
A
large surface area to volume ratio bc of the gill filaments.
short diffusion distance (capillary network in every lamellae and very thin gill lamellae)
maintaining conc gradient by having countercurrent flow mechanism
17
Q
describe the role of the enzymes of the digestive system in the complete breakdown of starch
A
the enzyme “amylase” hydrolyses the starch molecules into maltose.
then the maltose is hydrolysed into glucose by the enzyme “maltase”
18
Q
describe the processes involved in the absorption of the products of starch digestion
A
the glucose moves into the epithelial cells with sodium via the carrier proteins.
sodium is removed from the epithelial cells by active transport into the blood which help to maintain the low concentration of sodium in the epithelial cells which is important for a concentration gradient between the lumen and the epithelial cells.
Glucose moves into the blood via facilitated diffusion
19
Q
why don’t the epithelial cells of people with coeliac disease not absorb the products of digestion very well
A
the villi is damaged which reduces the surface area resulting in a decreased rate of facilitated diffusion
20
Q
name the monosaccharides that make sucrose
A
glucose and fructose
21
Q
name the monosaccharides that make lactose
A
glucose and galactose
22
Q
where is amylase produced and what does it make
A
pancreas
makes maltose
23
Q
where is maltase produced and what does it make
A
in the epithelial cells of the small intestine, makes glucose
24
Q
the oxygen dissociation curve of the fetus is to the left of that for its mother. explain the advantage of this for the fetus
A
theres a higher affinity for oxygen at the same partial pressure.
the oxygen moves from the mother to the fetus
25
explain how oxygen is loaded, transported and unloaded in the blood
the haemoglobin has a high affinity for oxygen in the red blood cells.
theres a loading of oxygen in the lungs at a high pO2
then the oxygen unloads from the haemoglobin in respiring cells at a low pO2
26
heat from respiration helps mammals maintain a constant body temperature .
explain the relationship between sa:v of mammals and the oxygen dissociation curves of their haemoglobins
mammals with a large surface area:volume will lose more heat but due to a large surface area:volume, this means they will also have a faster rate of respiration.
oxygen is needed for respiration which means the haemoglobin will have a higher affinity for oxygen to help maintain body temperature
27
haemoglobin has a quaternary structure. explain what is meant by a quaternary structure
more than one polypeptide chain
28
the total number of bases in DNA of the a-polypeptide gene is more than 423. give 2 reasons why
theres non-coding DNA present in the gene
stop/start sequences
29
the haemoglobin in 1 organism might have a different chemical structure from the haemoglobin in another organism. describe how
there might be a different number of polypeptide chains
30
explain why llamas are better adapted to live in high mountains than horses
llamas have a lower partial pressure so haemoglobin will load more oxygen.
haemoglobin has a higher affinity for oxygen in llamas
31
in large cells of U marinum, most mitochondria are found close to the cell-surface membrane. in smaller cells, the mitochondria are distributed evenly throughout the cytoplasm. mitochondria use oxygen during aerobic respiration. use this information and your knowledge of sa:v to suggest an explanation for the position of mitochondria in large U marinum cells
larger cells have a smaller surface area:volume therefore, it would take longer for the oxygen to diffuse to the mitochondria if they were spread evenly in the cytoplasm.
this means there would be less oxygen in the mitochondria because there would be a larger diffusion area
32
describe and explain the mechanism that causes the lungs to fill with air
the diaphragm contracts, causing the external intercostal muscles to contract which makes the volume inside the lungs increase but makes the pressure inside the lungs decrease. air moves from a high to low concentration of pressure so air will move into the lungs from the outside because of the high atmospheric pressure
33
explain how the countercurrent principle allows efficient oxygen uptake in the fish gas exchange system
the blood and water flow in opposite directions so that the concentration gradient is maintained along the lamella so that oxygen can move out of the water from a high to low concentration
34
how does an organisms size relate to their surface area to volume ratio
the larger the organism, the lower the surface area to volume ratio
35
how does an organisms surface area to volume ratio relate to their metabolic rate
the smaller the surface area to volume ratio, the higher the metabolic rate
35
how might a large organism adapt to compensate for its small surface area to volume ratio
changes that increase surface area (e.g folding)
body parts become larger (e.g elephants ears)
elongating shape
developing a specialised gas exchange surface
35
why do multicellular organisms require specialised gas exchange surfaces
their smaller surface area to volume ratio means the distance that needs to be crossed is larger and substances can not easily enter the cells as in a single- celled organism
35
name 3 features of an efficient gas exchange surface
1. large surface area (folded membranes in mitochondria)
2. thin/short distance (wall of capillaries)
3. steep concentration gradient, maintained by blood supply or ventilation (alveoli)
36
why cant insects use their bodies as an exchange surface?
they have a waterproof chitin exoskeleton and a small surface area to volume ratio in order to conserve water
37
name and describe 3 main features of an insects gas transport system
spiracles (holes on the bodies surface which may be opened or closed by a valve for gas or water exchange)
tracheae (large tubes extending through all body tissues, supported by rings to prevent collapse)
tracheoles (smaller branches dividing off the tracheae)
38
explain the process of gas exchange in insects
gases move in and out of the trachea through the spiracles
a diffusion gradient allows oxygen to diffuse into the body tissue while waste CO2 diffuses out
contraction of muscles in the tracheae allows mass movement of air in and out
39
why cant fish use their bodies as an exchange surface
they have a waterproof, impermeable outer membrane and a small surface area to volume ratio
40
name and describe the 2 main features of a fishes gas transport system
gills (located within the body, supported by arches, along which are multiple projections of gill filaments, which are stacked up in piles)
lamellae (at right angles to the gill filaments, give an increased surface area. blood and water flow across them in opposite directions)
41
Explain the process of gas exchange in fish
The fish opens its mouth to enable water flow in then closes its mouth to increase pressure.
The water passes over the lamellae and the oxygen diffuses into the bloodstream.
Waste carbon dioxide diffuses into the water and flows back out of the gills
42
How does the countercurrent exchange system maximise oxygen absorbed by the fish
Maintains a steep concentration gradient, as water is always next to blood of a lower oxygen concentration. Keeps diffusion constant and enables 80% of available oxygen to be absorbed
43
Name and describe three adaptations of a leaf that allow efficient gas exchange
1. Thin and flat to provide short diffusion pathway and large surface area to volume ratio
2. Many minute pores in the underside of the leaf (stomata) allow gases to easily enter
3. Air spaces in the mesophyll allow gases to move around the leaf, facilitating photosynthesis
44
How do plants limit their water loss while still allowing gases to be exchanged
Stomata regulated by guard cells which allows them to open and close as needed. Most stay closed to prevent water loss while some open to let oxygen in
45
Describe the pathway taken by air as it enters the mammalian gaseous exchange system
Nasal cavity > trachea > bronchi > bronchioles > alveoli
46
Describe the function of the nasal cavity in the mammalian gaseous exchange system
A good blood supply warms and moistens the air entering the lungs, Goblet cells in the membrane secrete mucus which traps dust and bacteria
47
Describe the trachea and its function in the mammalian gaseous exchange system
Wide tube supported by C-shaped cartilage to keep the air passage open during pressure changes.
Lined by ciliated epithelium cells which move mucus towards the throat to be swallowed, preventing lung infections.
Carries air to the bronchi
48
Describe the bronchi and their function in the mammalian gaseous exchange system
Like the trachea they are supported by rings of cartilage and are lined by ciliated epithelium cells. But unlike the trachea, they are narrower and there are 2 of them, one for each lung. They allow the passage of air into the bronchioles
49
Describe the bronchioles and their function in the mammalian gaseous exchange system
They are narrower than the bronchi and do not need to be kept open by cartilage, therefore they mostly only have muscles and elastic fibres so they can contract and relax easily during ventilation. Their role is to allow passage of air into the alveoli
50
Describe the alveoli and their function in the mammalian gaseous exchange system
Mini air sacs, lined with the epithelium cells, they are the site of gas exchange
Walls are 1 cell thick, covered in a network of capillaries, 300 million in each lung, all facilitate gas diffusion
51
Explain the process of inspiration and the changes that occur throughout the thorax
External intercostal muscles contract (while internal relax), pulling the ribs up and out
Diaphragm contracts and flattens
Volume of the thorax increases
Air pressure outside the lungs is therefore higher than the air pressure inside, so air moves to rebalance
52
Explain the process of expiration and the changes that occur throughout the thorax
External intercostal muscles relax (while internal contract), bringing the ribs down and in.
Diaphragm relaxes and domes upwards
Volume of thorax decreases
Air pressure inside the lungs is therefore higher than the air pressure outside, so air moves out to rebalance
53
What is tidal volume
The volume of air we breathe in and out during each breath at rest
54
What is breathing rate
The number of breaths we take per minute
55
How do you calculate pulmonary ventilation rate
Tidal volume x breathing rate. These can be measured using a spirometer, a device which records volume changes onto a graph as a person breathes
56
Define digestion
The hydrolysis of large, insoluble molecules into smaller molecules that can be absorbed across cell membranes
57
Which enzymes are involved in carbohydrate digestion? Where are they found?
Amylase in mouth
Maltase, sucrase, lactase in membrane of small intestine
58
what are the substrates and products of carbohydrate digestive enzymes
Amylase - starch into smaller polysaccharides
Maltase - maltose into 2 x glucose
Sucrase - sucrose into glucose and fructose
Lactase - lactose into glucose and galactose
59
Where are lipids digested
The small intestine
60
What needs to happen before lipids can be digested?
They must be emulsified by bile salts produced by the liver. This breaks down large fat molecules into smaller, soluble molecules called micelles, increase the surface area
61
How are lipids hydrolysed/broken down?
Lipase hydrolyses the ester bond between the monoglycerides and fatty acids
62
which enzymes are involved in protein digestion and what is their role?
Endopeptidases - break between specific amino acids in the middle of a polypeptide
Exopeptidases - break between specific amino acids at the end of a polypeptide
Dipeptidases - break dipeptides into amino acids
63
How are certain molecules absorbed into the ileum despite a negative concentration gradient
through co-transport
64
Which molecules require co-transport
Amino acids and monosaccharides
65
Explain how sodium ions are involved in co-transport
Sodium ions (Na+) are actively transported out of the cell into the lumen, creating a diffusion gradient. Nutrients are then taken up into the cells along with Na+ ions
66
Why do fatty acids and monoglycerides not require co-transport
The molecules are nonpolar, meaning they can easily diffuse across the membrane of the epithelial cells
67
Describe the structure of haemoglobin
Globular, water soluble. Consists of 4 polypeptide chains, each carrying a haem group (quaternary structure)
68
Describe the role of haemoglobin
Present in red blood cells. Oxygen molecules bind to the haem groups and are carried around the body to where they are needed in respiring tissues
69
Name 3 factors affecting oxygen-haemoglobin binding
1. Partial pressure/ concentration of oxygen.
2. Partial pressure/ concentration of carbon dioxide
3. Saturation of haemoglobin with oxygen
70
How does partial pressure of oxygen affect oxygen-haemoglobin binding
As partial pressure of oxygen increases, the affinity of haemoglobin for oxygen also increases, so oxygen binds tightly to haemoglobin. When partial pressure is low, oxygen is released from haemoglobin
71
How does the partial pressure of carbon dioxide affect oxygen-haemoglobin binding?
As partial pressure of carbon dioxide increases, the conditions become acidic causing haemoglobin to change shape. The affinity of haemoglobin for oxygen therefore decreases, so oxygen is released from haemoglobin. This is known as the Bohr effect
72
How does saturation of haemoglobin with oxygen affect oxygen-haemoglobin binding?
It is hard for first oxygen molecule to bind. Once it does, it changes the shape to make it easier for the 2nd and 3rd molecules to bind, known as positive cooperativity. It is then slightly harder for the 4th oxygen molecule to bind because there is a low chance of finding a binding site
73
Explain why oxygen binds to haemoglobin in the lungs
Partial pressure of oxygen is high. Low concentration of carbon dioxide in the lungs so affinity is high. Positive cooperativity (after the 1st oxygen molecule binds, binding of subsequent molecules is easier)
74
Explain why oxygen is released from haemoglobin in respiring tissues
Partial pressure of oxygen is low
High concentration of carbon dioxide in respiring tissues, so affinity decreases
75
What do oxyhaemoglobin dissociation curves show?
Saturation of haemoglobin with oxygen (in %), plotted against partial pressure of oxygen (kPa). Curves further to the left show the haemoglobin has a higher affinity of oxygen
76
how does carbon dioxide affect the position of an oxyhaemoglobin dissociation curve?
Curve shifts to the right because haemoglobins affinity for oxygen has decreased
77
Name 3 common features of a mammalian circulatory system
1. Suitable medium for transport, water-based to allow substances to dissolve
2. Means of moving the medium and maintaining pressure throughout the body, such as the heart
3. Means of controlling flow so it remains undirectional, such as valves
78
Relate the structure of the chambers in the heart to their function
Atria: thin-walled and elastic, so they can stretch when filled with blood
Ventricles: thick muscular walls pump blood under high pressure. The left ventricle is thicker than the right because it has to pump blood all the way around the body
79
Relate the structure of the veins and arteries to their functions
Arteries have thick walls to handle high pressure without tearing, and are muscular and elastic to control blood flow.
Veins have thin walls due to lower pressure, therefore requiring valves to ensure blood doesnt flow backwards. Have less muscular and elastic tissue as they don't have to control blood flow
80
Why are 2 pumps (left and right) needed instead of one?
To maintain blood pressure around the whole body. When blood passes through the narrow capillaries of the lungs, the pressure drops sharply and therefore would not be flowing strongly enough to continue around the whole body. Therefore it is returned to the heart to increase the pressure
81
Describe what happens during cardiac diastole
The heart is relaxed. blood enters the atria increasing the pressure and pushing open the atrioventricular valves. This allows blood to flow into the ventricles. Pressure in the heart is lower than in the arteries, so semilunar valves remain closed
82
Describe what happens during atrial systole
The atria contract, pushing any remaining blood into the ventricles
83
Describe what happens during ventricular systole
The ventricles contract. The pressure increases, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves. Blood flows into the arteries
84
Name the nodes involved in heart contraction and where they are situated
Sinoatrial node (SAN) - wall of right atrium.
Atrioventricular node (AVN) - in between the 2 atria
85
What does the myogenic mean
The hearts contraction is initiated from within the muscle itself, rather than by nerve impulses
86
Why does the impulse need to be delayed
If the impulse spread straight from the atria into the ventricles, there would not be enough time for all the blood to pass through and for the valves to close
87
How is the structure of capillaries suited to their function
Walls are only 1 cell thick so there is a short diffusion pathway.
Very narrow, so can permeate tissues and red blood cells can lie flat against the wall, effectively delivering oxygen to tissues.
Numerous and highly branched, providing a large surface area
88
What is a tissue fluid
A watery substance containing glucose, amino acids, oxygen, and other nutrients. It supplies these to the cells while also removing any waste materials
89
How is tissue fluid formed?
As blood is pumped through increasingly small vessels, this creates hydrostatic pressure which forces fluid out of the capillaries. It bathes the cells, and then returns to the capillaries when the hydrostatic pressure is low enough
90
How is water transported in plants?
Through xylem vessels; long, continuous columns that also provide structural support to the stem
91
Explain the cohesion tension theory
Water molecules form hydrogen bonds with eachother, causing them to stick together (cohesion). The surface tension of the water also creates this sticking effect. Therefore as water is lost through transpiration, more can be drawn up the stem
92
What are the 3 components of phloem vessels
Sieve tube elements - form a tube to transport sucrose in the dissolves form of sap.
Companion cells - involved of ATP production for active loading of sucrose into sieve tubes.
Plasmodesmata - gaps between cell walls where the cytoplasm links, allowing substances to flow
93
Name the process whereby organic materials are transported around the plant
translocation
94
How does sucrose in the leaf move into the phloem
Sucrose enter companion cells of the phloem vessels by active loading, which uses ATP and a diffusion gradient of hydrogen ions. Sucrose then diffuses from companion cells into the sieve tube elements through plasmodesmata
95
How do phloem vessels transport sucrose around the plant?
As sucrose moves into the tube elements, water potential inside the phloem is reduced. This causes water to enter via osmosis from the xylem and increases hydrostatic pressure. Water moves along the sieve tube towards areas of lower hydrostatic pressure. Sucrose diffuses into surrounding cells where it is needed
96
Give evidence for the mass flow hypothesis of translocation
Sap is released when a stem is cut, therefore there must be pressure is in the phloem.
There is a higher sucrose concentration in the leaves than the roots.
Increasing sucrose levels in the leaves results in the increased sucroses in the phloem
97
Give evidence against the mass flow hypothesis of translocation
The structure of sieve tubes seems to hinder mass flow. Not all solutes move at the same speed, as they would in mass flow.
Sucrose is delivered at the same rate throughout the plant, rather than to areas with the lowest sucrose concentration first
98
How can ringing experiments be used to investigate transport in plants
The bark and phloem of a tree are removed in a ring, leaving behind the xylem. Eventually the tissues above the missing ring swells due to accumulation of sucrose as the tissues below begins to die. Therefore, sucrose must be transported in the phloem
99
How can tracing experiments be used to investigate transport in plants
Plants are grown in the presence of radioactive CO2, which will be incorporated into the plants sugars. Using audioradiography, we can see that the areas exposed to radiation correspond to where the phloem is
