B6 Exchange Flashcards
(123 cards)
1
Q
What’s the SA :V
A
The relationship between the size of an organism or structure and its surface area to volume ratio plays a significant role in the types of adaptations an organism will have.
2
Q
Small organisms & SA:V
A
Small organisms e.g amoeba, very large surface area in comparison to volume.
big surface for exchange of substances, but also there is a smaller distance from the outside of the organisms to the middle of it.
As a result, very small organism can simply exchange substances across their surface.
3
Q
Larger organisms and SA:V
A
larger an organism, smaller its SA compared to vol and larger the distance from middle to outside.
typically have higher metabolic rate, which demands efficient transport of waste out of cells and reactants into cells.
have adaptations help make exchange across surfaces more efficient.
4
Q
Adaptations of larger organisms to increase SA:V
A
Villi and microvilli - Absorption of digested food
Alveoli and bronchioles - Gas exchange
Spiracles and tracheoles - Gas exchange
Gill filaments and lamellae - Gas exchange
Thin wide leaves - Gas exchange
Many capillaries -capillary network
5
Q
What happens during digestion
A
large biological molecules hydrolysed to smaller molecules that can be absorbed across cell membranes.
6
Q
What enzymes do carbohydrates require to hydrolyse them into monosaccharides
A
Amylases
Membrane-bound disaccharidases
7
Q
Where is amylase produced
A
Pancreas and salivary glands
8
Q
What does amylase do
A
It hydrolyses polysaccharides into disaccharide maltose by hydrolysing glycosidic bonds.
9
Q
What are examples of membrane-bound enzymes
A
Sucrose and lactase
10
Q
What do membrane-bound enzymes(sucrase and lactase) do
A
hydrolyse sucrose and lactose into monosaccharides.
11
Q
How many enzymes can protein be hydrolysed by
A
3
12
Q
What are the 3 enzymes proteins can be broken down by
A
Endopeptidases
Exopeptidases
Membrane-bound dipeptidases
13
Q
What d Endopeptidases do
A
hydrolyse peptide bonds between amino acids in middle of polymer chain
14
Q
What do Exopeptidases do
A
hydrolyse peptide bonds between amino acids at end of polymer chain
15
Q
What do Membrane-bound dipeptidases
A
hydrolyse peptide bonds between 2 amino acids
16
Q
Where are proteins digested
A
Protein digestion starts in stomach, continues in the duodenum and is fully digested in ileum.
17
Q
Where are lipids digested
A
Lipids are digested by lipase and the action of bile salts.
18
Q
Where is lipase produced and what does it do
A
Lipase is produced in the pancreas and it can hydrolyse the ester bond in triglycerides to form the monoglycerides and fatty acids.
19
Q
Where are bile salts produced and what do they do
A
Bile salts are produced in the liver and can emulsify lipids to form tiny droplets, micelles. This increases the surface area for lipase to act on.
20
Q
What are the 2 stages in lipid digestion
A
Physical (emulsification & micelle formation)
Chemical (Lipase)
21
Q
What happens in the 1st stage of lipid digestion
A
Physical (emulsification & micelle formation)
Lipids are coated in bile salts to create an emulsion.
Many small droplets of lipids provides a larger surface area to enable the faster hydrolysis action by lipase.
22
Q
What happens in the 2nd stage of lipid digestion
A
Chemical (Lipase)
Lipase hydrolyses lipids into glycerol and fatty acids (some monoglycerides) .
23
Q
What are micelles
A
Micelles are water soluble vesicles formed of the fatty acids, glycerol, monoglycerides and bile salts.
24
Q
What do micelles do
A
Micelles deliver the fatty acids, glycerol and monoglycerides to the epithelial cells of the ileum for absorption.
25
How does micro villi maximise absorption
by increasing SA, decreasing diffusion distance and maintaining concentration gradient.
26
What is the ileum covered in
The ileum wall is covered in villi, which have thin walls surrounded by a network of capillaries and epithelial cells have even smaller microvilli
27
In mammals the products of digestion are absorbed where
Across the cells lining the ileum
28
What are lipids digested into and by what
monoglycerides and fatty acids by the action of lipase and bile salts.
29
Describe process of lipid absorption
Lipids digested into monoglycerides and fatty acids by action of lipase and bile salts.
These form tiny structures called micelles
When micelles encounter ileum epithelial cells, due to non-polar nature of fatty acids and monoglycerides, they can simply diffuse across cell surface membrane to enter cells of epithelial cells.
Once in cell, these will be modified back into triglycerides inside of endoplasmic reticulum and Golgi body.
30
Describe how digested lipids are absorbed and then transport to the ileum and lymphatic system. [5]
1. Micelles are made of bile salts, fatty acids and monoglycerides
2. Micelles carry the fatty acids to the epithelial cells of the ileum
3. Fatty acids are absorbed into the cells of the ileum by simple diffusion
4. Triglycerides or chylomicrons are formed
5. Vesicles are removed by exocytosis
31
Describe the importance of micelles in absorbing lipids into the epithelial cells of the ileum. [3]
1. Micelles are made of bile salts, fatty acids and monoglycerides/glycerol
2. Micelles make fatty acids more soluble in water
3. Micelles carry fatty acids to the epithelial cells of the ileum
4. The fatty acids are released from the micelle and are absorbed into the cell by simple diffusion
32
When lipids are digested, they first form smaller droplets and then micelles are formed.
Explain the advantages of these two stages. [3]
1. Lipid droplets the increase surface areas for lipase
2. This speeds up hydrolysis / digestion
3. The micelles bring the fatty acids, monoglycerides and glycerol to the epithelial cell
33
How are Golgi apparatus involved in the absorption of lipids? [3]
1. They modify triglycerides
2. They combine proteins with triglycerides to form chylomicrons
3. These are packaged into vesicles
34
How do micelles help with lipid absorption?
They make the fatty acids more soluble in water
They carry the fatty acids to epithelial cells of the ileum
They help to maintain a higher concentration of fatty acids compared to the epithelial cells of the ileum
The fatty acids are then released from the micelle and enter the epithelial cell by simple diffusion
35
Why do fatty acids enter by simple diffusion?
They are non-polar (lipid soluble)
So they can dissolve and diffuse through the phospholipid bilayer.
36
What happens once fatty acids are in the cell?
The fatty acids.and monoglycerides are modified back into triglycerides inside of the endoplasmic reticulum and Golgi body.
Sometimes a protein is added to the lipid, making it a chylomicron.
37
How do modified lipids leave the epithelial cell?
Vesicles containing the triglyceride/chylomicron are released and move towards the cell membrane.
• They are released by exocytosis
• Then the triglycerides/chylomicrons enter the lacteal.
38
Why is active transport and co-transport required to absorb glucose and amino acids from the lumen to the gut.
To absorb glucose and amino acids from the lumen to the gut there must be a higher concentration in the lumen compared to the epithelial cell (for facilitated diffusion).
BUT
There is usually more in the epithelial cells.
39
What’s Tissue fluid
Fluid containing water, glucose, amino acids, fatty acids, ions and oxygen which bathes the tissues.
40
How is tissue fluid formed
Capillaries have small gaps in the walls so that liquid and small molecules can be forced out.
As blood enters the capillaries from arterioles, the smaller diameter results in a high hydrostatic pressure so water, glucose, amino acids, fatty acids, ions and oxygen are forced out. This is known as ultrafiltration.
Large molecules remain in the capillaries and therefore create a lowered water potential.
Towards the venule end of the capillaries, hydrostatic pressure is lowered due to loss of liquid, but water potential is very low.
Water re-enters capillaries by osmosis.
41
What is forced out when forming tissue fluid
Water molecules
Dissolved minerals and salts
Glucose
Small proteins and amino acids
Fatty acids oxygen
42
What remains in the capillary when forming tissue fluid
Red blood cells
Platelets
Large proteins
43
The lymph
Not all the liquid will be reabsorbed by osmosis, as equilibrium will be absorbed.
The rest of the tissue fluid is absorbed into the lymphatic system and eventually drains back into the bloodstream near the heart.
44
What is breathing
movement of air into and out of the lungs.
45
What is respiration
chemical reaction to release energy the form of ATP.
46
What is ventilation
the scientific word for breathing.
47
What is gaseous exchange
diffusion of oxygen from the air in the alveoli into the blood and of carbon dioxide from the blood into the air in the alveoli.
48
Why is Breathing an active process
It uses energy
49
Describe the process of inspiration
external intercostal muscles contract, internal intercostal muscles relax.
ribs pulled upwards and outwards, increasing volume of thorax.
diaphragm muscles contract, causing it to flatten, which also increases volume of thorax.
• increased volume of thorax results in reduction of pressure in lungs.
• Atmospheric pressure now greater than pulmonary pressure, and so air is forced into lungs.
50
Describe the process of expiration
internal intercostal muscles contract, external intercostal muscles relax.
ribs move downwards and inwards, decreasing volume of thorax.
diaphragm muscles relax and so it’s pushed up again by contents of abdomen that were compressed during inspiration.
volume of thorax is therefore further decreased.
decreased volume of thorax increases pressure in lungs.
pulmonary pressure is now greater than that of atmosphere, and so air forced out of lungs.
51
What is tidal volume
Volume of air that enters and leaves the lungs at normal resting breath (0.5dm3)
52
What is Vital capacity
Max volume of air we can inhale and exhale
53
What is Residual volume
Volume of air left in lungs after the strongest exhalation
54
What’s total lung capacity
Vital capacity + residual capacity (normally 5-6dm3)
55
What’s pulmonary ventilation
the total volume of air that is moved into the lungs during one minute (dm min-').
56
Pulmonary ventilation equation
Pulmonary ventilation = tidal volume x ventilation rate
(dm min-1). (dm3). (min-1)
57
What are examples of lung diseases
Pulmonary fibrosis
Asthma
Emphysema
Bronchitis
58
Example exam question style
A student concluded the data shows more cigarettes smoked per day will increase deaths.
Do you agree?
There is a positive correlation between lung cancer deaths and cigarettes smoked
However:
The data overlaps
Correlation does not prove causation - other factors, such as genetics or pollution could cause the deaths
There is no correlation coefficient statistic to know if the correlation is significant.
59
Why do fish require a gas exchange surface
Fish are waterproof and the have a small surface area to volume ratio.
60
What’s the gas exchange surface in fish
Gills
61
Why do fish have a special adaptation to maintain conc gradient to enable diffusion to occur.
As Fish obtain oxygen from water, but there’s 30 time less oxygen in water than air,
62
Features of gas exchange surfaces
Large surface area to volume ratio
Short diffusion distance
Maintained a concentration gradient
63
What law can be used to calculate the rate of diffusion
Diffusion (alpha sign)
(surface area x difference in concentration) /length of diffusion path
64
How many layers of gills are on both sides of the head
4
65
What are the gills made up of
Stacks of gill filaments
66
What is each gill filament covered in
Each gill filament is covered in gill lamellae, position at right angles to the filament.
67
What do gill lamellae do
Create a large SA
68
What happens when fish open their mouth
When fish open their mouth
water rushes in and over the gills
and then out through a hole in the sides of their head.
69
Terrestrial insects features
• Insects have an exoskeleton made of hard fibrous material for protection and a lipid layer to prevent water loss.
• Insects do not have lungs, and instead have a tracheal system.
70
What gas exchange system do insects have
Tracheal system (trachea, tracheoles and spiracles
71
What are spiracles and what do they do
Spiracles are round, valve like openings, running along the length of the abdomen. Oxygen and carbon dioxide enter and leave via the spiracles. The trachea attach to these openings.
72
What are trachea
The trachea is a network of internal tubes.
The trachea tubes have rings within them to strengthen the tubes and to keep them open.
73
What do the trachea do
The trachea branch into smaller tubes, deeper into the abdomen of the insect called tracheoles.
These extend throughout all the tissues in the insect to deliver oxygen to all respiring cells.
74
How many methods of moving gases in the tracheal system are there
3
75
What’s the 1st method of moving gases in the tracheal system
Gas can exchange by diffusion, as when cells respire, they use up oxygen and produce carbon dioxide, creating a concertation gradient from the tracheoles to the atmosphere.
76
What’s the 2nd method of moving gases in the tracheal system
The second method of gas exchange is mass transport, in which an insect contracts and relaxes their abdominal muscles to move gases on mass.
77
What’s the 3rd method of moving gases in the tracheal system
When the insect is in flight the muscle cells start to respire anaerobically to produce lactate. This lowers the water potential of the cells, and therefore water moves from the tracheoles into the cells by osmosis. This decreases the volume in the tracheoles and as a result more air from the atmosphere is draw in.
78
What happens once the gases are in the alveoli
gas exchanges between the epithelium and the blood.
79
Features of alveolar epithelium for efficient gas exchange
Alveoli are tiny air sacks, and there are 300 million in each human lung - creates very large SA for gas exchange.
alveoli epithelium cells very thin, to minimise diffusion distance.
Each alveolus is surrounded by network of capillaries to remove exchanged gases, and therefore maintains conc gradient.
80
5 features of the human gas exchange system
alveoli
bronchioles
bronchi
trachea
lungs
81
Which enzyme are proteins broken down to aminonacids
Proteases
82
Insect adaptations to limit water loss
Insects have a small surface area to volume ratio where water can evaporate from
Insects have a waterproof exoskeleton
Spiracles, where gases enter and water can evaporate from, can open and close to reduce water loss.
83
Adaptations for efficient diffusion in insects
Large number of fine tracheoles - large surface area
Walls of tracheoles are thin and short distance between spiracles and tracheoles - short diffusion pathway
Use of oxygen and production of carbon dioxide sets up steep diffusion gradients
84
Adaptations for efficient gas exchange in fish
Large surface to volume ratio created by many gill filaments covered in many gilli lamellae
Short diffusion distance due to a capillary network in every lamellae and very thin gill lamellae
Maintaining concentration gradient
countercurrent flow mechanism.
85
What is the countercurrent exchange principle
This is when water flows over the gills in the opposite direction to the flow of blood in the capillaries.
86
What does countercurrent flow ensure
Countercurrent flow ensures that equilibrium is not reached
This ensures that a diffusion gradient is maintained across the entire length of the gill lamellae.
87
Define digestion
The hydrolysis of large, insoluble molecules into smaller molecules that can be absorbed across cell membranes.
88
Which enzymes are involved in carbohydrate digestion? Where are they found?
Amylase in mouth
Maltese, sucrase, lactase in membrane if small intestine
89
What are the substrates + products of carbohydrate digestion enzymes?
Amylase —> starch into smaller polysaccharides
Maltase —> maltose into 2 X glucose
Sucrase —> sucrose into glucose + fructose
Lactase —> lactose into glucose + galactose
90
Where are lipids digested
Small intestine
91
What needs to happen before lipids can be digested
They must be emulsified by bile salts produced by liver.
This breaks down large fat molecules into smaller, soluble molecules called micelles, increasing SA
92
How are lipids digested
Lipase hydrolyses ester bond between monoglycerides and fatty acids
93
Which enzymes are involved in protein digestion? What are their roles?
Endopeptidases = breaks between specific amino acids in middle of a polypeptide
Exopeptidases = breaks between between specific amino acids at end of a polypeptide
Dipeptidases = breaks between dipeptides into amino acids
94
How are certain molecules absorbed into ileum despite a neg conc gradient
Through co-transport
95
Which molecules require co-transport
Amino acids and monosaccharides
96
Explain how Na+ are involved in co-transport
Na+ are actively transported out of cell into Lumen, creating a diffusion gradient.
Nutrients are then taken up into the cells along with Na+
97
Why do fatty acids & monoglycerides not require co-transport
The molecules are non-polar, meaning they can easily diffuse across the membrane of the epithelial cells
98
How does an organism’s size relate to their SA to Vol ratio
The larger an organism, the lower the SA:V
99
How does an organsim’s SA:V relate to their metabolic rate
The lower the SA:V, the lower the metabolic rate
100
How might a large organisms adapt to compensate for its small SA:V
Changes that increase SA e.g. folding; body parts become larger e.g. elephants ears; elongating shape; developing a specialised gas exchange surface
101
Why do multicellular organisms require specialised gas exchange surfaces
Their smaller SA:V means the distance that needs to be crossed is larger & substances cannot easily enter the cells as in a single-celled organsim
102
Name 3 features of an efficient gas exchange surface
1. Large SA,. E.g. folded membranes in mitochondria
2. Thin/short distance, e.g. wall of capillaries
3. Steep conc gradient, maintained by blood supply or ventilation, e.g. alveoli
103
Why can’t insects use their bodies as an exchange surface
They have a waterproof chitin exoskeleton & a small SA:V in order to conserve water
104
Name and describe the 3 main features of an insect’s gas transport system
Spiracles = holes on body’s surface which may be opened/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 trachea
105
Explain the process of gas exchange in insects
Gases move in + out of trachea through the spiracles
Diffusion gradient allows oxygen to diffuse into body tissue while waste CO2 diffuses out
Contraction of muscles in the trachea allows mass movement of air in and out
106
Why can’t fish use their bodies as an exchange surface
They have a waterproof, impermeable outer membrane and a small SA:V
107
Why can’t fish use their bodies as an exchange surface
They have a waterproof, impermeable outer membrane and small SA:V
108
Name and describe the 2 main features of a fish’s gas transport system
Gills = located within 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 SA. blood and water flow across them in opp directions (countercurrent exchange system)
109
Explain process of gas exchange in fish
Fish opens its moth to enable water to flow in, then closes its mouth to increase pressure
The water passes over the lamellae and the oxygen diffuses into the blood stream
Waste CO2 diffuses into the water and flows back out of the gills
110
How does the countercurrent exchange system maximise oxygen absorbed by the fish
Maintains a steep conc gradient, as water is always next to blood of a lower o2 conc. keeps rate of diffusion constant along whole length of gill enabling 80% of available oxygen to be absorbed
111
Name and describe 3 adaptations of a leaf that allow efficient gas exchange
1. Thin + flat to provide short diffusion pathway & large SA:V
2. Many minute pores pores in underside of leaf (stomata) allow gases to easily enter
3. Air spaces in mesophyll allow gases to move around leaf, facilitating photosynthesis
112
How do plants link it their water loss while still allowing gases to be exchanged
Stomata regulated by guard cells which allow them to open and close as needed.
Most stay closed to prevent water loss while some open to let oxygen in
113
Describe pathway taken by air as it enters mammalian gaseous exchange system
Nasal cavity
Trachea
Bronchi
Bronchioles
Alveoli
114
Describe function of nasal cavity in mammalian gaseous exchange system
A good blood supply warms and moistens air entering the lungs.
Goblet cells in membrane secrete mucus which traps dust and bacteria
115
Describe trachea and its functions in mammalian gaseous exchange system
Wide tube supported by c-shaped cartilage to keep air passage open during pressure changes
Lined by ciliated epithelium cells which move mucus towards throat to be swallowed, preventing lung infections
Carries air to bronchi
116
Describe bronchi and their functions in mammalian gaseous exchange system
Like trachea they’re supported by rings of cartilage + are lined by ciliated epithelium cells
However they’re narrower and there are 2 of them, 1 for each lung
Allow passage of air into bronchioles
117
Describe bronchioles and their function in mammalian gaseous exchange system
Narrower than bronchi
Do not need to be kept open by cartilage, therefore mostly have only muscle and elastic fibres so that they can contract and relax easily during ventilation
Allow passage of air into alveoli
118
Describe alveoli and their function in mammalian gaseous exchange system
Mini air sacs, lined with epithelium cells, site of gas exchange
Walls only 1 cell thick, covered with a network of capillaries, 300 million in each lung, all of which facilitates gas diffusion
119
Explain process of inspiration and changes that occur throughout thorax
External ICM pull ribs up and out
Diaphragm contracts and flattens
Vol of thorax increases
Air pressure outside lungs is therefore higher than air pressure inside, so air moves in to rebalance
120
Explain process of expiration and changes that occur throughout thorax
External ICM relax bringing ribs down and in
Diaphragm relaxes and domes upwards
Vol of thorax decreases
Air pressure inside lungs is therefore higher than air pressure outside, so air moves out to rebalance
121
What’s tidal volume
The vol of air we breathe in and out during each breath at rest
122
What’s breathing rate
Number of breaths we take per minute
123
How do you calculate pulmonary ventilation rate
Tidal vol X breathing rate
These can be measured using a spirometer, a device which records vol changes onto a graph as a person breathes
