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Mass transport Flashcards

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AP® Biology flashcards Biology 101 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
Q

What causes pulmonary tuberculosis and its symptoms?

A

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
Q

What is pulmonary fibrosis, and how does it affect the lungs?

A

Pulmonary fibrosis forms scar tissue that thickens and reduces lung elasticity, slowing gas exchange and reducing lung volume.

27
Q

What happens during an asthma attack?

A

Airways become inflamed and irritated. Smooth muscle contracts, narrowing the airways, and mucus is produced, making breathing difficult.

28
Q

What causes emphysema, and how does it reduce gas exchange?

A

Emphysema is caused by smoking or air pollution. Alveoli walls are destroyed, reducing surface area and the ability to recoil, leading to breathlessness.

29
Q

What are the two stages of digestion?

A

The stages are physical breakdown (large food pieces broken mechanically) and chemical breakdown (enzymes hydrolyse molecules).

30
Q

How are carbohydrates digested?

A

Amylase breaks down carbohydrates into maltose, then membrane-bound disaccharidases hydrolyse them into monosaccharides, which are absorbed across membranes.

31
Q

What enzymes are involved in lipid digestion?

A

Lipase hydrolyses lipids into monoglycerides and fatty acids, which stick to bile salts to form micelles.

32
Q

How are proteins digested?

A

Proteins are hydrolysed by endopeptidases (within chains), exopeptidases (at ends), and dipeptidases (dipeptides into amino acids).

33
Q

What is haemoglobin, and what is its function?

A

Haemoglobin is a quaternary protein that carries oxygen. Each molecule can carry four oxygen molecules, forming oxyhaemoglobin.

34
Q

How does partial pressure of oxygen affect haemoglobin saturation?

A

High partial pressure increases oxygen affinity, leading to high saturation, while low partial pressure causes oxygen to unload.

35
Q

What is the Bohr effect?

A

Increased carbon dioxide lowers haemoglobin’s oxygen affinity, shifting the dissociation curve to the right and aiding oxygen unloading.

36
Q

Why does foetal haemoglobin have a higher oxygen affinity?

A

Foetal haemoglobin must extract oxygen from maternal haemoglobin, so it has a higher oxygen affinity.

37
Q

Why do organisms need a circulatory system?

A

Organisms with a low surface area to volume ratio require a specialized transport system to deliver substances efficiently.

38
Q

What type of circulatory system do mammals have?

A

A closed system with two circuits: heart to lungs and heart to body.

39
Q

What are the main blood vessels of the heart?

A

Pulmonary artery, pulmonary vein, aorta, superior vena cava, inferior vena cava.

40
Q

What are the main features of arteries?

A

1) Carry oxygenated blood away from the heart (except pulmonary artery). 2) Thick muscle and elastic tissue. 3) High pressure. 4) Narrow lumen.

41
Q

What are the main features of veins?

A

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
Q

What are arterioles and venules?

A

Smaller blood vessels than arteries and veins; arterioles direct blood to areas of demand.

43
Q

What are capillaries, and what is their function?

A

Smallest blood vessels where substance exchange occurs. Their walls are one cell thick to provide a short diffusion path.

44
Q

How does tissue fluid form?

A

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
Q

What happens to excess tissue fluid?

A

Excess tissue fluid is drained into the lymphatic system, which transports it back into the circulatory system.

46
Q

What happens during atrial systole?

A

Atria contract, ventricles relax, blood is pushed into ventricles, and AV valves are open.

47
Q

What happens during ventricular systole?

A

Ventricles contract, atria relax, pressure in ventricles increases, AV valves close, and SL valves open.

48
Q

What happens during diastole?

A

Ventricles and atria relax, blood flows into atria due to low pressure, and SL valves are closed to prevent backflow.

49
Q

What is cardiac output and how is it calculated?

A

Cardiac output is the volume of blood pumped by one ventricle in one minute. Cardiac output = heart rate x stroke volume.

50
Q

What is the cohesion-tension theory in plants?

A

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
Q

What adaptations help the xylem transport water efficiently?

A

1) Hollow tubes with no end walls. 2) Thick walls lined with lignin for support. 3) Continuous column of water flow.

52
Q

What factors affect the rate of transpiration?

A

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
Q

What is the function of a potometer?

A

A potometer measures the rate of water uptake by a plant as a bubble moves along the capillary tube.

54
Q

What adaptations do xerophytes have to reduce water loss?

A

1) Small surface area. 2) Sunken stomata. 3) Stomatal hairs. 4) Rolled leaves. 5) Thick waxy cuticle. 6) Extensive root systems.

55
Q

What is the mass flow theory in translocation?

A

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
Q

What is the structure of the phloem?

A

1) Sieve tube elements with no nucleus. 2) Companion cells with organelles. 3) Sieve plates allow flow between cells.

57
Q

What evidence supports the mass flow theory?

A

1) Ringing experiments (removing phloem). 2) Radioactive tracers (track sugar). 3) Aphid stylet experiments. 4) Use of metabolic inhibitors.

58
Q

What are objections to the mass flow theory?

A

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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