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deck_5806897 Flashcards

1
Q

What do all living cells need to survive?

A

A supply of oxygen and nutrients, and also need to remove waste products

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2
Q

Why do living cells need to remove waste products?

A

So they don’t build up and become toxic

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3
Q

Do very small organisms need an exchange system?

A

Takes place over the surface of the body and they don’t need a specialised exchange system

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4
Q

Do larger organisms need an exchange system?

A

They have more than two layers of cells so the body surface isn’t sufficient for exchange. They need a specialised surface for exchange of substances with their environment

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5
Q

What are the three main factors that affect the need for an exchange system?

A

Size, surface area to volume ratio and level of activity

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6
Q

How does exchange happen in smaller organisms?

A

All cytoplasm is very close to the environment in which they live. Diffusion will supply enough oxygen and nutrients to keep the cells alive and active

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7
Q

How does exchange happen in larger organisms?

A

Any oxygen or nutrients diffusing in from the outside has a longer diffusion pathway, due to the layers of cells, making diffusion too slow to enable a sufficient supply to the innermost cells

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8
Q

What is the surface area to volume ratio of smaller organisms?

A

Small surface area and small volume, but their surface area is relatively large compared to the volume, making a large surface area to volume ratio

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9
Q

What does it mean if an organism has a large surface area to volume ratio?

A

Their surface area is large enough to supply all their cells with sufficient oxygen

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10
Q

what is the surface area to volume ratio of larger organisms?

A

Larger surface area and a larger volume. As size increases, the volume rises more quickly than surface area, so they have a small surface area to volume ratio because their surface area is relatively small compared with their volume

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11
Q

How can some organisms increase their surface area?

A

By adopting a different shape, eg the flatworm has a very thin, flat body giving it a larger surface area to volume ratio, but there is a limit to the overall size it can reach

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12
Q

What do most lager organisms need to support their body and give them strength?

A

A range of tissue, and as their body gets thicker, their volume increases, but their surface area doesn’t increase as much, so the surface area to volume ratio of a large organism is relatively small

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13
Q

What does metabolic activity use and require?

A

Uses energy from food, and requires oxygen to release the energy in aerobic respiration

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14
Q

What do cells of active organisms need?

A

Good supplies of nutrients and oxygen to supply energy for movement, and the need is increased in animals, such as mammals, that keep themselves warm

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15
Q

What are three features of a good exchange surface?

A

Large surface area, good blood supply, and a thin barrier

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16
Q

Why do exchange surfaces need a large surface area?

A

To provide more space for molecules to pass through. This is often achieved by folding the walls and membranes involved, eg root hairs in plants

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17
Q

Why do exchange surfaces need a good blood supply?

A

Can bring fresh supplies of molecules to one side, maintaining the concentration gradient, by adding/removing molecules, important to maintain steep concentration gradient to speed up diffusion, eg gills in fish

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18
Q

Why do exchange surfaces need a thin barrier?

A

To reduce diffusion distance, it must be permeable to the substances being exchanged, eg alveoli of the lungs

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19
Q

What does the gas exchange system in mammals consist of?

A

Lungs, and associated airways that carry air into and out of the lungs

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20
Q

What are the lungs?

A

A pair of inflatable sacs lying in the chest cavity

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21
Q

How can air pass into the lungs?

A

Through the nose and along the trachea, bronchi and bronchioles, then it can reach tiny air filled sacs (alveoli) which are the surfaces for gas exchange

22
Q

What are the lungs protected by?

A

The ribcage. Ribs are held together by intercostal muscles, which help to produce breathing movements (ventilation), along with the diaphragm

23
Q

Where do gasses diffuse through?

A

Thin walls of the alveoli

24
Q

Where does the oxygen go?

A

Passes from air in alveoli, to blood in capillaries

25
Q

Where does the carbon dioxide go?

A

Passes from blood to air in the alveoli.

26
Q

Why must the lungs maintain a steep concentration gradient in each direction?

A

In order to ensure that diffusion can continue

27
Q

How do the lungs have a large surface area?

A

Alveoli are very small but there are so many that the total surface area of the lungs is larger than out skin (about 70m2)

28
Q

What are the alveoli lined by?

A

Thin layer of moisture, that evaporates and is lost when we breath out. The lungs must produce a surface that coats the internal surface of the alveoli to reduce cohesive forces between water molecules which could make the alveoli collapse

29
Q

How do the lungs have a good barrier for exchange?

A

It is permeable to oxygen and carbon dioxide, and is comprised of the walls of the alveolus and the wall of the blood capillary. Cells and plasma membranes allow diffusion of oxygen and carbon dioxide as they are small and non-polar

30
Q

What are the adaptation to reduce the distance that the gases have to diffuse?

A

Alveolus wall is one cell thick, capillary wall is one cell thick, both walls have squamous cells (flattened/very thin), capillaries are in close contact with alveolus walls, and capillaries are so narrow that red blood cells are squeezed against capillary wall (so closer to air in alveoli, reducing rate of flow)

31
Q

What is the total barrier to diffuse?

A

Only two flattened cells, and is less than 1 um thick

32
Q

How does the blood transport carbon dioxide?

A

Transports it from tissues to the lungs, ensuring that the concentration of carbon dioxide in the blood is higher than that in the air of the alveoli so the carbon dioxide diffuses into the alveoli

33
Q

How does the blood transport oxygen?

A

Transports it away from the lungs, ensuring that the concentration of oxygen in the blood is kept lower than in the alveoli so it diffuses into the blood

34
Q

What do breathing movements do?

A

Ventilate the lungs, which replaces the used air with fresh air, bringing in more oxygen and removing carbon dioxide

35
Q

What does ventilation ensure?

A

That the concentration of oxygen in the air of the alveolus remains higher than in the blood, and the concentration of the carbon dioxide in the alveoli remains lower than in the blood (concentration gradient for diffusion is maintained)

36
Q

What happens during inspiration (inhaling)?

A

Diaphragm contracts to move down and become flatter, external intercostal muscles contract to raise the ribs, volume of chest cavity increases, pressure in chest cavity drops below atmospheric pressure, air is moved into the lungs

37
Q

What happens during expiration (exhaling)?

A

Diaphragm relaxes and pushed up by organs underneath, external intercostal muscles relax and ribs fall, volume of chest cavity decreases, pressure in lungs increases and rises above atmospheric pressure, air is moved out of the lungs

38
Q

What happens when exercising, coughing or sneezing?

A

Intercostal muscles can contract to help push air out more forcefully

39
Q

What are alveoli comprised of?

A

Squamous epithelium, and are surrounded by blood capillaries so that diffusion distance is short

40
Q

What do the alveolus walls contains?

A

Elastic fibres that stretch during inspiration, and then recoil to help push air out during expiration

41
Q

Why is it not possible to distinguish separate alveoli under a light microscope?

A

The alveolus walls are so thin

42
Q

What requirements must the airways meet?

A

Large enough to allow sufficient air to flow without obstruction, supported to prevent collapse when the air pressure is low during inspiration, and be flexible in order to allow movement

43
Q

What are the airways lined by?

A

Ciliated epithelium which contributes to keeping the lungs healthy

44
Q

What do goblet cells do?

A

They are in the epithelium and release mucus, which traps pathogens, cilia then move the mucus up to the top of the airway, where it is swallowed

45
Q

What does glandular tissue do?

A

In the loose tissue it also produces mucus

46
Q

What is the difference in structure between trachea and bronchi?

A

The bronchi are narrower than the trachea, though they have a similar structure

47
Q

What are the airways supported by?

A

Rings of cartilage which prevent collapse during inspiration, they are c-shaped to allow flexibility and space for food to pass down the oesophagus

48
Q

What are the bronchioles like?

A

Much narrower than bronchi. Larger bronchioles may have some cartilage but smaller ones have none. The wall is comprised mostly of smooth muscle and elastic fibres. Smallest bronchioles end in clusters of alveoli

49
Q

What does smooth muscle do?

A

It can contract and the action of it will constrict the airway, which makes the lumen narrower. This can restrict flow of air to and from the alveoli

50
Q

Why is controlling the flow of air to the alveoli important?

A

If there are harmful substances in the air

51
Q

What sort of reaction is the contraction of smooth muscle and control of airflow?

A

Involuntary, and it may occur as result of an allergic reaciton

52
Q

What happens once the smooth muscle has contracted?

A

It can’t reverse this effect on its own, it is elongated again by the elastic fibres which are deformed as the muscle contracts. As it replaces, the fibres recoil to their original size and shape which acts to dilate the airways

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