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AS Biology > 3.3 > Flashcards

3.3 Flashcards

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1
Q

What does mass transport maintain?

A

The diffusion gradient that brings materials to and from the CSM.

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2
Q

What are examples of things that need to be interchanged between an organism and its environment?

A

Respiratory gases: O2 and CO2

Nutrients: Glucose, fatty acids and amino acids, vitamins, minerals.

Excretory products: urea and CO2

Heat

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3
Q

Except for heat how do the examples of things that need to be interchanged between an organism and its environment take place?

A

Passively (no metabolic energy is required)
i.e. by diffusion & osmosis.

Actively (metabolic energy is required)
i.e. by active transport.

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4
Q

SURFACE AREA TO VOLUME RATIO:
How does an organism size relate to their surface area to volume ratio?

A

The larger the organism, the lower the surface area to volume ratio.

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5
Q

SURFACE AREA TO VOLUME RATIO:
How does an organism’s surface area to volume ratio relate to their metabolic rate?

A

The smaller the SA:V, the higher the metabolic rate.

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6
Q

SURFACE AREA TO VOLUME RATIO:
What features have organisms evolved to supply enough of a substance if diffusion alone was the only method of transport?

A

A flattened shape } no cell is ever far from the surface (e.g: flatworm or a leaf)

Specialised exchange surfaces with large areas to increase SA:V (e.g: lungs in mammals, gills in fish)

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7
Q

SURFACE AREA TO VOLUME RATIO:
Why do multicellular organisms require specialised gas exchange surfaces?

A

Their smaller SA:V means that the distance that needs to be crossed is larger ∴ substances cannot easily enter the cells as in single-celled organisms.

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8
Q

SURFACE AREA TO VOLUME RATIO:
What is the purpose of specialised exchange surfaces?

A

To allow effective transfer of materials across specialised exchange surfaces by diffusion or active transport.

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9
Q

SURFACE AREA TO VOLUME RATIO:
What are 5 specialised exchange surfaces?

A
  1. A large SA:V } increases the rate of exchange.
  2. Exchange surfaces must be very thin } diffusion distance is short and ∴ materials cross exchange surfaces faster.
  3. Selectively permeable } to allow selected materials to cross
  4. movement of environmental medium i.e. air
    } maintain diffusion gradient.
  5. A transport system to ensure movement of internal medium i.e. blood, in order to maintain diffusion gradient.
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10
Q

GAS EXCHANGE IN SINGLE-CELLED ORGANISMS:
How does a single-celled organism relate to their SA:V?

A

They are small ∴ have a large SA:V.

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11
Q

GAS EXCHANGE IN INSECTS:
Why can’t insects use their bodies as an exchange surface?

A

They have a waterproof chitin exoskeleton and a small SA:V in order to conserve water.

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12
Q

GAS EXCHANGE IN INSECTS:
For gas exchange what have insects evolved?

A

Internal network of tubes } tracheae.

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13
Q

GAS EXCHANGE IN INSECTS:
How is the gas exchange system in insects ‘laid out’?

A
  1. Trachea } supported by strengthened rings to prevent collapsing.
  2. Trachea divide into smaller dead end tubes
    } tracheoles.
  3. Tracheoles extend throughout body tissues of the insect.
  4. this way atmospheric air, with O2 it contains, is brought directly to respiring tissues } short diffusion pathway from tracheole to any body cell.
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14
Q

GAS EXCHANGE IN INSECTS:
How do gases enter and leave the tracheae?

A

Through tiny pores, called spiracles on the body surface.

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15
Q

GAS EXCHANGE IN INSECTS:
Are the spiracles opened or closed?

A

May be opened and closed by a valve.

Opened: water vapour can evaporate from the insect.

Closed (most of the time): to prevent water loss.

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16
Q

GAS EXCHANGE IN INSECTS:
What happens when the spiracles are opened?

A

H2O vapour can evaporate from insects.

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17
Q

GAS EXCHANGE IN INSECTS:
What happens when the spiracles are closed?

A

Most of the time spiracles are closed } prevent H2O loss.

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18
Q

GAS EXCHANGE IN INSECTS:
How do respiratory gases move in and out of the tracheal system?

A
  1. Along a diffusion gradient.
  2. Mass transport.
  3. The ends of the tracheoles are filled with water.
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19
Q

GAS EXCHANGE IN INSECTS:
How do respiratory gases move in and out of the tracheal system along a diffusion gradient?

A

Cells respiring } O2 used up ∴ its conc. towards the ends of tracheoles falls.
} creates a diffusion gradient that causes gaseous O2 to diffuse from the atmosphere along tracheae and tracheoles into cells.

CO2 produced by cells during respiration } diffusion gradient in opposite direction.
} causes gaseous CO2 to diffuse along the tracheoles and tracheae from cells to atmosphere.

respiratory gases exchange more faster this way.

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20
Q

GAS EXCHANGE IN INSECTS:
How do respiratory gases move in and out of the tracheal system by mass transport?

A

Contraction of muscles in insects can squeeze enabling mass movements of air in and out, speeding up the exchange of respiratory gases.

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21
Q

GAS EXCHANGE IN INSECTS:
How do respiratory gases move in and out of the tracheal system by the ends of the tracheoles being filled with water?

A

periods of major activity
} muscle cells around tracheoles respire
} carry out anaerobic respiration
} produces lactate -> soluble and lowers Ψ
of muscle cells.
} H2O moves into cells from tracheoles by osmosis.
} water in ends of tracheoles decrease in vol.
} final diffusion pathway, gas.
} diffusion more rapid

22
Q

GAS EXCHANGE IN INSECTS:
What are the 3 adaptations that insects have evolved to reduce water loss?

A
  1. Small SA:V } minimise the area over which water is lost.
  2. Waterproof coverings over body surfaces } rigid
    outer skeleton of chitin that is covered with a waterproof cuticle.
  3. Spiracles: can be closed to reduce water loss.
    conflicts with the need for O2 & occurs when the
    insect is at rest.
23
Q

GAS EXCHANGE IN FISH:
Why can’t fish use their bodies as an exchange surface?

A

They have a waterproof, impermeable outer membrane.

They have a small SA:V.

24
Q

GAS EXCHANGE IN FISH:
Name and describe the two main features of a fish’s gas transport system.

A
  1. Gills: located within the body, behind the head supported by arches. They are made up of gill filaments } stacked up in a pile.
  2. Lamellae: at right angles to the filaments, increase SA of gills. Blood and H2O flow in opposite directions } counter current flow.
25
Q

GAS EXCHANGE IN FISH:
Explain the process of gas exchange in a fish.

A
  1. Fish opens its mouth to take in H2O, and close it to increase pressure.
  2. H2O passes over the lamellae, and O2 diffuses into the bloodstream.
  3. Waste CO2 diffuses into water and flows back out of the gills.
26
Q

GAS EXCHANGE IN FISH:
How does the counter current exchange system maximise oxygen absorbed by the fish?

A

Maintain a steep conc. gradient } H2O is always next to blood of a lower O2 conc.

Keep the rate of diffusion constant.

Enables 80% of O2 to be absorbed.

27
Q

GAS EXCHANGE IN FISH:
What would happen if a parallel flow occurred in the gills of a fish instead of a counter current flow?

A

A diffusion gradient is maintained only 1/2 of the distance across the lamellae.

Only 50% of O2 from water diffuses into the blood.

28
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
Which gas diffuses into the stomata when photosynthesis is taking place ?

A

CO2 } comes from respiration of cells but most is obtained from external air.

29
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
Which gas diffuses out of the stomata when photosynthesis is taking place?

A

O2 } some O2 in photosynthesis is used in respiration but most diffuses out of plant.

30
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
What happens when photosynthesis is not occurring i.e. in the dark?

A

O2 diffuses into the leaf because it’s constantly being used by cells during respiration.

CO2 produced diffuses out during respiration.

31
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
Name and describe some adaptations of a leaf that allow efficient gas exchange.

A
  1. Thin and flat } short diffusion pathway.
  2. large SA:V } rapid diffusion
  3. many minute pores in the underside of leaf (stomata) } allow gases to enter easily.
  4. Air spaces in mesophyll } allow gases to move around the leaf, facilitating photosynthesis.
32
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
What is a single stomata called?

A

A stoma.

33
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
What surrounds each stoma?

A

A guard cell.
} can open and close the stomatal pore } control rate of gaseous exchange.

34
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
How do plants limit their water loss while still allowing gases to be exchanged?

A

Stomata is regulated by guard cells

Guard cells may close the stomata at times when water loss would be excessive.

35
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
If plants have waterproof coverings why can they not have a small SA:V?

A

The plants photosynthesise

Photosynthesis requires a large SA:V for the capture of light and exchange of gases.

36
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
What are Xerophytic plants?

A

Are plants that are adapted to living in areas where H2O is in short supply.
i.e. sand dunes

37
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
How does a thick cuticle reduce the rate at which water is lost through evaporation?

A

The thicker the cuticle, the less water can escape.
i.e holly

38
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
How does rolling up the leaves reduce the rate at which water is lost through evaporation?

A

The rolling of leaves is a way that protects the lower epidermis from the outside helps to trap a region of air within the rolled leaf.

region -> saturated with water vapour ∴ has a very high Ψ.

There is no Ψ gradient between the in and outside of leaf ∴ no water loss.

i.e. Marram grass rolls its leaves.

39
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
How does hairy leaves reduce the rate at which water is lost through evaporation?

A

A thick layer of hairs on leaves, especially on lower epidermis, traps moist air next to the leaf surface.

Ψ gradient of in and outside of leaves is reduced ∴
less water is lost.
i.e. one type of heather plant has this modifi.

40
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
How does stomata in pits or grooves reduce the rate at which water is lost through evaporation?

A

Trap still, ,moist air next to the leaf and reduce Ψ
gradient.
i.e. pine trees.

41
Q

GAS EXCHANGE IN THE LEAF OF A PLANT:
How does a reduced SA:V of the leaves reduce the rate at which water is lost through evaporation?

A

The smaller the SA:V the slower the rate of diffusion.

By having leaves that are small and roughly circular in cross-section i.e. pine needles than leaves that are broad and flat, the rate of H2O loss can be reduced.

42
Q

LIMITING WATER LOSS:
Insects and plants face the same problems when it comes to living on land. What is the main problem they share?

A

Efficient gas exchange requires a thin, permeable surface with a large area.

On land these features can lead to a considerable loss of water by evaporation.

43
Q

STRUCTURE OF HUMAN GAS-EXCHANGE SYSTEM:
State two reasons why humans need to absorb large volumes of oxygen from the lungs.

A
  1. Humans are large with a large vol. of living cells.
  2. They maintain high body temp. which is related to them having high metabolic and respiratory rates.
44
Q

STRUCTURE OF HUMAN GAS-EXCHANGE SYSTEM:
What is a site of gas exchange in mammals?

A

Lungs.

45
Q

STRUCTURE OF HUMAN GAS-EXCHANGE SYSTEM:
State two reasons why the lungs are located inside the body.

A
  1. air is not dense enough to support and protect these delicate structures.
  2. The body would lose a great deal of H2O and dry out.
46
Q

STRUCTURE OF HUMAN GAS-EXCHANGE SYSTEM:
List in the correct sequence all the structures that air passes through on its journey from gas-exchange surface of the lungs to the nose.

A

Alveoli, bronchioles, bronchus, trachea, nose.

47
Q

STRUCTURE OF HUMAN GAS-EXCHANGE SYSTEM:
State the structure and function of lungs.

A

Lungs are a pair of lobed structures made up of a series of bronchioles (highly branched), which end in tiny air sacs called alveolis.

48
Q

STRUCTURE OF HUMAN GAS-EXCHANGE SYSTEM:
State the structure and function of the trachea.

A

Trachea is a flexible airway supported by rings of cartilage.

Cartilage prevents trachea from collapsing as the air pressure inside falls when breathing in.

Trachea walls } muscle, lined with ciliated epithelial and goblet cells.

49
Q

STRUCTURE OF HUMAN GAS-EXCHANGE SYSTEM:
State the structure and function of the bronchi.

A

Two divisions of trachea, each leading to one lung.

Similar structure to trachea.

Produce mucus to trap dirt particles and have cilia that move dirt-laden mucus towards the throat.

Larger bronchi supported by cartilage.

50
Q

STRUCTURE OF HUMAN GAS-EXCHANGE SYSTEM:
State the structure and function of the bronchioles.

A

Series of branching subdivisions of the bronchi.

Walls made of muscles lined with epithelial cells.

Muscles allow them to constrict so that they can control flow of air in and out of alveoli.

51
Q

STRUCTURE OF HUMAN GAS-EXCHANGE SYSTEM:
State the structure and function of the alveoli.

A

are minute air-sacs (diameter between 100μm and 300μm.)

Between alveoli there are some collagen and elastic fibres.

Lined with epithelium.

Elastic fibres allow alveoli to stretch as they fill with air when breathing in.

Spring back during breathing out in order to remove CO2-rich air.

52
Q

STRUCTURE OF HUMAN GAS-EXCHANGE SYSTEM:
What is the gas-exchange surface in the lungs?

A

The alveolar membrane.

AS Biology (5 decks)

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