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Mass transport Flashcards

1
Q

What are examples of substances exchanged at exchange surfaces?

A

Examples include respiratory gases (oxygen and carbon dioxide), nutrients (glucose, amino acids, vitamins, minerals), excretory products (urea and carbon dioxide), water, and heat.

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2
Q

What are the two types of processes by which exchange takes place?

A

Exchange occurs passively (diffusion or osmosis) and actively (active transport).

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3
Q

What is the surface area to volume ratio?

A

It describes how close every internal part of an object is to its surface, calculated as surface area divided by volume.

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4
Q

How does a low surface area to volume ratio affect exchange?

A

In a low ratio, substances take longer to enter or leave, and heat is gained or lost slowly.

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5
Q

Why do fish require special adaptations for gas exchange?

A

Water has a lower oxygen concentration than air, so fish need adaptations to extract oxygen efficiently.

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6
Q

What structures in fish maximize gas exchange surface area?

A

Gills are made up of gill filaments and lamellae, which provide a large surface area.

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7
Q

How does the counter-current system work in fish?

A

Blood flows in the opposite direction to water, maintaining a concentration gradient so oxygen concentration in water is always higher than in blood.

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8
Q

Why is the counter-current system efficient?

A

It allows more than 50% of oxygen to be diffused into the blood.

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9
Q

What are the main structures involved in insect gas exchange?

A

Insects use tracheae, microscopic air-filled pipes, and spiracles, which are pores for air entry.

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10
Q

How does oxygen travel to insect cells?

A

Oxygen travels down the concentration gradient through tracheoles, with thin permeable walls for direct diffusion to cells.

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11
Q

How is carbon dioxide removed from insects?

A

Carbon dioxide diffuses out along its concentration gradient to the spiracles.

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12
Q

What helps insects move air in and out of the tracheal system?

A

Rhythmic abdominal movements help move air in and out of the spiracles.

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13
Q

What gases do plants require for photosynthesis and respiration?

A

Plants need carbon dioxide for photosynthesis and oxygen for respiration.

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14
Q

Where does gas exchange occur in plants?

A

Gas exchange occurs on the surface of mesophyll cells and through pores in the epidermis called stomata.

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15
Q

How do stomata regulate gas exchange?

A

Stomata open and close to allow exchange and to prevent water loss.

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16
Q

How do plants adapt for efficient gas exchange?

A

Adaptations include very short diffusion pathways, large surface areas of mesophyll cells, and stomata that maintain a concentration gradient.

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17
Q

What happens during inspiration?

A
  • External intercostal and diaphragm muscles contract.
  • Ribcage moves upwards and outwards; diaphragm flattens.
  • Volume increases, pressure decreases, and air flows into the lungs.
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18
Q

What happens during expiration?

A
  • External intercostal and diaphragm muscles relax.
  • Ribcage moves downwards and inwards; diaphragm curves.
  • Volume decreases, pressure increases, and air flows out of the lungs.
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19
Q

What is the difference between normal and forced expiration?

A

Normal expiration is passive, while forced expiration involves internal intercostal muscles contracting to push the ribcage further down.

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20
Q

What are the characteristics of alveoli for efficient gas exchange?

A

Alveoli have a large surface area, thin cell lining for short diffusion pathways, and moist surfaces for gas dissolution.

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21
Q

What is the equation for pulmonary ventilation?

A

Pulmonary ventilation = tidal volume × ventilation rate.

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22
Q

What is tidal volume?

A

Tidal volume is the volume of air in each breath.

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23
Q

What is forced expiratory volume?

A

It is the maximum volume of air that can be breathed out in one second.

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24
Q

What is forced vital capacity?

A

It is the maximum volume of air that can be forcibly breathed out of the lungs.

25
What causes pulmonary tuberculosis and its symptoms?
It is caused by bacteria. The immune system builds a wall around the bacteria, forming tubercles. Tissue damage reduces gas exchange surface area, leading to symptoms such as persistent cough, chest pain, and shortness of breath.
26
What is pulmonary fibrosis, and how does it affect the lungs?
Pulmonary fibrosis forms scar tissue that thickens and reduces lung elasticity, slowing gas exchange and reducing lung volume.
27
What happens during an asthma attack?
Airways become inflamed and irritated. Smooth muscle contracts, narrowing the airways, and mucus is produced, making breathing difficult.
28
What causes emphysema, and how does it reduce gas exchange?
Emphysema is caused by smoking or air pollution. Alveoli walls are destroyed, reducing surface area and the ability to recoil, leading to breathlessness.
29
What are the two stages of digestion?
The stages are physical breakdown (large food pieces broken mechanically) and chemical breakdown (enzymes hydrolyse molecules).
30
How are carbohydrates digested?
Amylase breaks down carbohydrates into maltose, then membrane-bound disaccharidases hydrolyse them into monosaccharides, which are absorbed across membranes.
31
What enzymes are involved in lipid digestion?
Lipase hydrolyses lipids into monoglycerides and fatty acids, which stick to bile salts to form micelles.
32
How are proteins digested?
Proteins are hydrolysed by endopeptidases (within chains), exopeptidases (at ends), and dipeptidases (dipeptides into amino acids).
33
What is haemoglobin, and what is its function?
Haemoglobin is a quaternary protein that carries oxygen. Each molecule can carry four oxygen molecules, forming oxyhaemoglobin.
34
How does partial pressure of oxygen affect haemoglobin saturation?
High partial pressure increases oxygen affinity, leading to high saturation, while low partial pressure causes oxygen to unload.
35
What is the Bohr effect?
Increased carbon dioxide lowers haemoglobin’s oxygen affinity, shifting the dissociation curve to the right and aiding oxygen unloading.
36
Why does foetal haemoglobin have a higher oxygen affinity?
Foetal haemoglobin must extract oxygen from maternal haemoglobin, so it has a higher oxygen affinity.
37
Why do organisms need a circulatory system?
Organisms with a low surface area to volume ratio require a specialized transport system to deliver substances efficiently.
38
What type of circulatory system do mammals have?
A closed system with two circuits: heart to lungs and heart to body.
39
What are the main blood vessels of the heart?
Pulmonary artery, pulmonary vein, aorta, superior vena cava, inferior vena cava.
40
What are the main features of arteries?
1) Carry oxygenated blood away from the heart (except pulmonary artery). 2) Thick muscle and elastic tissue. 3) High pressure. 4) Narrow lumen.
41
What are the main features of veins?
1) Carry deoxygenated blood to the heart (except pulmonary vein). 2) Little elastic or muscle tissue. 3) Low pressure. 4) Valves to stop backflow. 5) Wide lumen.
42
What are arterioles and venules?
Smaller blood vessels than arteries and veins; arterioles direct blood to areas of demand.
43
What are capillaries, and what is their function?
Smallest blood vessels where substance exchange occurs. Their walls are one cell thick to provide a short diffusion path.
44
How does tissue fluid form?
1) At the start of the capillary bed, hydrostatic pressure forces fluid out of capillaries into surrounding tissue. 2) Water re-enters the capillaries by osmosis at the venule end.
45
What happens to excess tissue fluid?
Excess tissue fluid is drained into the lymphatic system, which transports it back into the circulatory system.
46
What happens during atrial systole?
Atria contract, ventricles relax, blood is pushed into ventricles, and AV valves are open.
47
What happens during ventricular systole?
Ventricles contract, atria relax, pressure in ventricles increases, AV valves close, and SL valves open.
48
What happens during diastole?
Ventricles and atria relax, blood flows into atria due to low pressure, and SL valves are closed to prevent backflow.
49
What is cardiac output and how is it calculated?
Cardiac output is the volume of blood pumped by one ventricle in one minute. Cardiac output = heart rate x stroke volume.
50
What is the cohesion-tension theory in plants?
Water evaporates from leaves (transpiration), creating tension that pulls water up the xylem in a continuous column. Cohesion between water molecules maintains this column.
51
What adaptations help the xylem transport water efficiently?
1) Hollow tubes with no end walls. 2) Thick walls lined with lignin for support. 3) Continuous column of water flow.
52
What factors affect the rate of transpiration?
1) Temperature: Higher temp increases evaporation. 2) Wind speed: Removes water vapor, increasing diffusion. 3) Light intensity: Opens stomata for photosynthesis. 4) Humidity: Reduces diffusion due to more moist air.
53
What is the function of a potometer?
A potometer measures the rate of water uptake by a plant as a bubble moves along the capillary tube.
54
What adaptations do xerophytes have to reduce water loss?
1) Small surface area. 2) Sunken stomata. 3) Stomatal hairs. 4) Rolled leaves. 5) Thick waxy cuticle. 6) Extensive root systems.
55
What is the mass flow theory in translocation?
Sucrose is actively transported into the phloem, lowering water potential, causing water to enter. This creates high pressure, pushing solutes down to sink cells where they are used.
56
What is the structure of the phloem?
1) Sieve tube elements with no nucleus. 2) Companion cells with organelles. 3) Sieve plates allow flow between cells.
57
What evidence supports the mass flow theory?
1) Ringing experiments (removing phloem). 2) Radioactive tracers (track sugar). 3) Aphid stylet experiments. 4) Use of metabolic inhibitors.
58
What are objections to the mass flow theory?
1) Sugars are transported to different sinks at different rates. 2) Sieve plates would act as a barrier to mass flow.

Biology (13 decks)

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