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A-Level Biology - OCR A > 3.1.1 Exchange Surfaces > Flashcards

3.1.1 Exchange Surfaces Flashcards

1
Q

What is the need for exchange surfaces?

A

Organisms need to exchange things with their internal and external environments

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2
Q

What substances do organisms need?

A

Oxygen - for aerobic respiration.
Glucose - for energy (respiration).
Protein - for growth and repair.
Fats - for the production of membranes and an energy store.
Water.
Minerals.

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3
Q

What do organisms need to get rid of?

A

Waste products (e.g. ammonia, urea and carbon dioxide).

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4
Q

What factors affect the need for an exchange surface?

A

Size.
Surface area to volume ratio.
Amount of activity.

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5
Q

Do unicellular organisms need exchange surfaces?

A

No

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6
Q

Why don’t unicellular organisms need exchange surfaces?

A

They have a small size and a large surface area to volume ratio. They aren’t very active organisms so diffusion alone is enough to meet the needs

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7
Q

Do multicellular organisms need exchange surfaces?

A

Yes

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8
Q

Why do multicellular organisms need exchange surfaces?

A

They have a small surface area to volume ratio due to their large size. They have high metabolic activity so have a high demand for reasorces. Diffusion alone is not sufficiant.

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9
Q

What is the formula for volume?

A

Volume = base x height x depth

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10
Q

What is the formula for surface area?

A

Sum of the area of all the sides.

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11
Q

How do you calculate SA:V ratio?

A

Do the surface area divided by the volume so that the volume is equal to 1.

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12
Q

How does SA:V ratio change with the size of the organism?

A

The larger the organism typically the smaller the SA:V ratio.

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13
Q

What effect does a small SA:V ratio have?

A

Makes it harder for organisms to supply substances as there’s a larger distance to cover (volume) but less surface to enter (surface area)

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14
Q

How can some organisms change their SA:V ratio?

A

`By changing their shape

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15
Q

What are the features of a good exchange surface?

A

Large Surface Area.
Thin Barrier.
Good Blood Supply.

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16
Q

How does a large surface area make a good exchange surface?

A

Provides a large space for molecules to pass through.

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17
Q

How are some cells adapted to increase surface area?

A

Grow long ‘hairs’ or folds in the cell walls/membranes.
e.g. Root hair cells or alveoli

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18
Q

How does a thin barrier make a good exchange surface?

A

Reduces the distance the substance has to diffuse. As long as the membrane is permeable.

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19
Q

How does a good blood supply make a good exchange surface?

A

Brings a large supply of substances to one side, this keeps the concentration high. Also removes molecules on the demand side, keeping the concentration low. This maintains a steep concentration that helps to aid diffusion.

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20
Q

How does air enter the human gas exchange system?

A

Air enters through the nostrils or the mouth.

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21
Q

How is the nose adapted for gaseous exchange?

A

A border of hairs that trap and filter particles out of the system. Good blood supply.
Warms and moistens the air.

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22
Q

How is the mouth adapted for human gas exchange?

A

There is a pharynx at the back of the neck where the air mixes with the air from the nasal passage.

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23
Q

Where does air pass from the mouth and nose?

A

The trachea then the bronchi

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24
Q

What is the structure of the trachea and bronchi?

A

There is an outer layer of C shaped cartilage which provides support and prevents collapsing with low air pressure.
There is a glandular layer that is responsible for mucus production.
A layer of smooth muscle allows the lumen to contract - typically in response to harmful chemicals (asthma). Elastic fibers allow the lumen to dilate after contraction and relaxed.
The inner lining is made of ciliated endothelium containing goblet cells for mucus production.

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25
Q

Why does the trachea have C shaped cartilage?

A

To prevent it crushing the esophagus

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26
Q

Where does air pass from the bronchi?

A

The bronchi sub divides into bronchioles that continue to divide into progressively smaller branches.

27
Q

How does the structure of bronchioles change?

A

They eventually loose their cartilages as they become smaller. They are mainly made of smooth muscle and elastic fibers. There is still a lining of ciliated epithelium.

28
Q

Where does air pass from the bronchioles?

A

Continues to divide into alveolar ducts that lead to the alveoli where gas exchange takes place.

29
Q

What are the alveoli?

A

Small sacs within the lungs that are surrounded by capillaries where gas exchange takes place.

30
Q

What substances are exchanged through the alveoli?

A

Oxygenn is moved from the alveoli into the blood.
Carbon Dioxide is moved from the blood to the alveoli.

31
Q

How are alveoli adapted to their function?

A

They have a large surface area to increase the rate of gaseous exchange (70cm2 in humans). They are also very small to give them a small volume.
The walls are only once cell thick for a short diffusion distance. The walls are made from squamous cells.
Has a good blood supply from close capillaries to reduce the distance for diffusion and provide a steep diffusion gradient.
They are moist to aid the movement of gases across the membrane.

32
Q

What are the intercostal muscles?

A

A group of muscles that run between ribs and help form and move the chest wall. There are both internal and external intercostal muscles.

33
Q

What is the role of external intercostal muscles?

A

During inspiration they contract, pushing the ribs up and out.

34
Q

What is the role of the internal intercostal muscles?

A

During forced expiration they contract allowing the ribs to fall and move in to force more air out.

35
Q

What are the lungs?

A

A pair of inflatable structures supported by the ribs that allows inspiration and expiration.

36
Q

What are the ribs?

A

Large curved bones that form part of the ribcage. They enclose the thorax cavity, which contains the lungs, and protects them.

37
Q

How many ribs are there in humans?

A

There are 24 ribs (12 pairs)

38
Q

What is the diaphragm?

A

A dome shaped sheet of muscle and tendon that serves as the main muscle in respiration.

39
Q

What happens to the diaphragm during insperation?

A

The diaphragm contracts and flattens, increasing the volume of the thorax cavity and decreasig the pressure. Theis causes the lungs to expand and fill with air.

40
Q

What happens to the diaphragm during expiration?

A

The diaphragm relaxes and returns to the dome shape. This reduces the volume of the thorax so pressure increases. This causes the lungs to shrink and air to be forced out of the lungs.

41
Q

What is inhilation and exhuilation?

A

Breathing movements that ventilate the lungs and replace used air with fresh air.

42
Q

What does ventilation ensure?

A

The concentration of oxygen in the air of the alveoli remains higher than that in the blood.
The concentration of carbon dioxide in the alveoli remains lower than in the blood.

43
Q

What happens during Inspiration?

A

The diaphragm contracts along with the external intercostal muscles.
This increases the size of the thorax and decreases the pressure in the thoracic cavity.
This causes the lungs to expand.
So the lungs are filled with air.

44
Q

What happens during exhilation?

A

The diaphragm relaxes along with the external intercostal muscles.
This decreases the size of the thorax and increases the pressure in the thoracic cavity.
This causes the lungs to shrink.
So the air in the lungs is expelled.

45
Q

When are the internal intercostal muscles used?

A

during forced expiration

46
Q

What is spirometry?

A

The measure of respiratory volumes and capacities.

47
Q

What is a spirometer?

A

instrument for measuring respiratory volumes and capacities

48
Q

What does spirometry show?

A

How well you breath in and out.

49
Q

What can spirometry detect?

A

Chronic obstructions.
Pulmonary disease.
Pulmonary fibrosis.
Cystic fibrosis.
Asthma.

50
Q

How do you observe the results from a spirometer?

A

A trace

51
Q

How does a spirometer work?

A

Patient breaths into a tube.
During inspiration air is drawn in from the chamber moving the lid down.
During exhalation air moves back into the chamber so it floats.
A pen on the lid draws a line (trace) on the paper. Or its recorded by a datalogger.

52
Q

What is needed in order for the spirometer to work?

A

The persons nose to be clamped so they only breath through the mouthpiece.
A chamber of soda lime to absorb carbon dioxide from exhalation.

53
Q

What does the soda lime do?

A

absorbs CO2 so makes it safer for the user.
Also allows the measurement of oxygen consumption.

54
Q

What precautions need to be made?

A

Soda lime should be fresh and functional.
No air leaks.
Sterile mouthpiece.
Water chamber not overfilled.

55
Q

What is total lung capacity?

A

The volume of air in the lungs at maximum inflation.
Sum of the vital capacity and residual volume.

56
Q

What is vital capacity?

A

The maximum volume of air that can be moved by the lungs in one breath.
Forced inhalation and exhalation.

57
Q

What is residual volume?

A

amount of air remaining in the lungs after a forced expiration

58
Q

What is tidal volume?

A

amount of air inhaled and exhaled during a normal breathing cycle.

59
Q

What is inspiratory reserve volume?

A

The maximum volume of air forcibly inspired after tidal volume.

60
Q

What is inspiratory capacity?

A

the maximum volume of air that can be inhaled after a normal exhalation

61
Q

What is expiratory reserve volume?

A

Maximum volume of air forcibly expired after tidal volume

62
Q

What is functional residual capacity?

A

volume of air remaining in the lungs after a normal expiration

63
Q

Why does the trace reduce over time?

A

There is less air in the system as some is lost as CO2 that is absorbed by soda lime.
Some is lost in the body to be used in respiration.

A-Level Biology - OCR A (16 decks)

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