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Paper 3 - Bio > Gas exchange > Flashcards

Gas exchange Flashcards

1
Q

How does an organism’s size relate to its surface area to volume ratio?

A

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

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2
Q

How does surface area to volume (SA/V) ratio affect transport of molecules?

A

The lower the SA/V ratio, the further the distance molecules must travel to reach all part of the organism. Diffusion alone is not sufficient in organisms with small SA/V ratios.

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3
Q

Why do larger organisms require mass transport and specialised gas exchange surfaces?

A
  • Small SA/V ratio.
  • Diffusion insufficient to provide all cells with the required oxygen and to remove all carbon dioxide.
  • Large organisms more active than smaller organisms.
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4
Q

Name four features of an efficient gas exchange surface.

A
  • Large surface area
  • Short diffusion distance
  • Steep diffusion gradient
  • Ventilation mechanism
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5
Q

Describe the gas exchange mechanism in Amoeba.

A
  • Unicellular organism with a large SA/V ratio.
  • Thin cell membrane provides short diffusion distance.
  • Simple diffusion across the cell surface membrane is sufficient to meet the demands of respiratory processes.
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6
Q

Describe the gas exchange mechanism in flatworms.

A
  • Multicellular organisms with a relatively small SA/V ratio (in comparison to Amoeba).
  • However, flat structure provides a large surface area and reduces the diffusion distance.
  • Simple diffusion is sufficient to meet the demands of respiratory processes.
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7
Q

Describe the gas exchange mechanism in earthworms.

A
  • Cylindrical, multicellular organisms with a relatively small SA/V ratio (in comparison to the flatworm).
  • Slow moving and low metabolic rate so require little oxygen.
  • Rely on external surface for gas exchange.
  • Circulatory system transports oxygen to the tissues and removes carbon dioxide, maintaining a steep diffusion gradient.
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8
Q

Define ventilation.

A

The movement of fresh air into a space and stale air out of a space to maintain a steep concentration gradient of oxygen and carbon dioxide.

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9
Q

Name the organ of gaseous exchange in fish.

A

Gills.

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10
Q

What are gill filaments?

A
  • Main site of gaseous exchange in fish, over which water flows.
  • They overlap to increase resistance to flowing water (slowing it down and maximizing gaseous exchange).
  • Found in large sacks, know as gill plates, and have a gill lamellae which provide a large surface area and good blood supply for exchange.
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11
Q

Explain the process of ventilation in bony fish.

A
  • Buccal cavity volume increases and pressure decreases to enable water to flow in.
  • Contraction of the buccal cavity forces water across the gills.
  • Pressure in the gill cavity rises, opening the operculum.
    Water leaves.
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12
Q

How is a steep diffusion gradient maintained across the entire gas exchange surface in bony fish?

A

Due to counter current flow.

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13
Q

Define counter current flow.

A

Blood and water flow in opposite directions across the gill plate.

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14
Q

How does countercurrent flow maintain a steep diffusion gradient? What is the advantage of this?

A
  • Water is always next to blood of a lower oxygen concentration.
  • Keeps rate of diffusion constant and enables 80% of available oxygen to be absorbed.
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15
Q

What type of flow is exhibited in cartilaginous fish?

A

Parallel flow.

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16
Q

Define parallel flow.

A

Water and blood flow in the same direction across the gill plate.

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17
Q

Name and describe the main features of an insect’s gas transport system.

A
  • Spiracles: small, external openings along the thorax and abdomen through which air enters, and air and water leave the gas exchange system.
  • Tracheae: large tubes extending through all body tissues, supported by rings of chitin to prevent collapse.
  • Tracheoles: smaller branches dividing off the tracheae.
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18
Q

What is the main site of gas exchange in insects?

A

Tracheoles.

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19
Q

Describe the adaptations of the insect tracheal system to a terrestrial environment.

A
  • Spiracles can be opened or closed to regulate diffusion.
  • Bodily contractions speed up the movement of air through the spiracles.
  • Highly branches tracheoles provide a large surface area.
  • Impermeable cuticle reduces water loss by evaporation.
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20
Q

Describe the ventilation of the tracheal system in insects.

A
  • Expansion of the abdomen opens the thorax spiracles (through which air enters) and closes the abdominal spiracles.
  • Compression of the abdomen closes the thorax spricales and opens the abdominal spiracles (through which air is expelled).
21
Q

Compare the gas exchange surface of an active and inactive amphibian.

A
  • Active amphibian has simple lungs.

- Inactive amphibian relies on its moist external surface for gas exchange.

22
Q

How are mammals adapted for gas exchange?

A

Alveoli provide a large surface area and thin diffusion pathways, maximising the volume of oxygen absorbed from one breath. They also have a plentiful supply of deoxygenated blood, maintaining a steep concentration gradient.

23
Q

Describe the structure and function of the larynx.

A

A hollow, tubular structure located at the top of the trachea involved in breathing and phonation.

24
Q

Describe the trachea and its function in the mammalian gaseous exchange system.

A
  • Primary airway, carries air from the nasal cavity down into the chest.
  • Wide tube supported by C-shaped cartilage to keep the air passage open during pressure changes.
  • Lined with ciliated epithelial cells which move mucus, produced by goblet cells, towards the back of the throat to be swallowed, this prevents lung infections.
25
Q

Describe the structure of the bronchi.

A
  • Divisions of the trachea that lead into the lungs.
  • Narrower than the trachea.
  • Supported by rings of cartilage and lined by ciliated epithelial cells and goblet cells.
26
Q

Describe the structure and function of the bronchioles.

A
  • Many small divisions of the bronchi that allow the passage of air into the alveoli.
  • Contain smooth muscle to restrict airflow to the lungs but do not have cartilage.
  • Lined with a thin layer of ciliated epithelial cells.
27
Q

What is the primary gaseous exchange surface in humans.

A

Alveoli.

28
Q

Describe the alveoli in the mammalian gaseous exchange system.

A
  • Mini air sacs, lined with epithelial cells.
  • Walls one cell thick.
  • Good blood supply to maintain a steep diffusion gradient.
  • 300 million in each lung.
29
Q

What are the pleural membranes?

A

Thin, moist layers of tissues surrounding the pleural cavity that reduce friction between the lungs and the inner chest.

30
Q

Define pleural cavity.

A

The space between the pleural membranes of the lungs and the inner chest wall.

31
Q

Describe ventilation in humans.

A
  • The movement of fresh air into the lungs and stale air out of the lungs via inspiration and expiration.
  • Via negative pressure breathing.
32
Q

What are internal intercostal muscles?

A

A set of muscles found between the ribs on the inside that are involved in forced exhalation.

33
Q

What are external intercostal muscles?

A

A set of muscles found between the ribs on the outside that are involved in forced and quiet inhalation.

34
Q

Explain the process of inspiration and the changes that occur throughout the thorax.

A
  • External intercostal muscles contract (while internal relax), raising the rib cage.
  • Diaphragm contracts and flattens.
  • Outer pleural membrane moves out, reducing pleural cavity pressure and pulling the inner membrane out.
  • The alveoli expand. Alveolar pressure falls below air pressure so air moves into the trachea.
35
Q

What is surfactant?

A

A fluid lining the surface of the alveoli that reduces surface tension and prevents collapse of the alveoli during exhalation.

36
Q

Explain the process of expiration.

A
  • External intercostal muscles relax so ribs move downwards and inwards allowing outer pleural membrane to move inwards.
  • Diaphragm relaxes and moves upwards.
  • This increases the pressure in the pleural cavity and the inner pleural membrane moves inwards.
  • This pushes on the surface of the lungs and causes the alveoli to contract.
  • The alveolar pressure increases to above the atmospheric pressure, so air is forced out.
37
Q

Describe the function of the waxy cuticle.

A

Reduces water loss from the leaf surface.

38
Q

Describe how the upper epidermis is adapted for photosynthesis.

A
  • Layer of transparent cells allow light to strike the mesophyll tissue.
  • Epidermal cells also synthesise the waxy cuticle, reducing water loss.
39
Q

Where is the palisade mesophyll layer located?

A

Directly below the upper epidermis.

40
Q

How is the palisade mesophyll layer adapted for photosynthesis?

A

It receives the most light so contains the greatest concentration of chloroplasts.

41
Q

How is the spongy mesophyll layer adapted for photosynthesis?

A
  • Contains air spaces that reduce the diffusion distance for carbon dioxide to reach the chloroplasts in the palisade layer.
  • Contains some chloroplasts.
42
Q

What is a vascular bundle?

A

The vascular system in dicotyledonous plants. It consists of two transport vessels, the xylem and the phloem.

43
Q

Why are vascular bundles important in photosynthesis?

A

They form a large network to deliver water and nutrients to photosynthetic tissues and remove glucose.

44
Q

Describe how the lower epidermis is adapted for photosynthesis?

A

It contains many stomata which enable the evaporation of water and inward diffusion of carbon dioxide.

45
Q

What are stomata?

A

Small holes found on leaves that can be opened or closed by guard cells to control gas exchange and water loss.

46
Q

Summarise the ‘malate’ theory.

A

The ‘malate’ theory states that the accumulation or loss of malate and K+ ions by guard cells results in changes in turgor pressure that opens or close the stomata.

47
Q

By what mechanism do K+ ions enter guard cells?

A

Active transport.

48
Q

How does the accumulation of K+ and malate ions affect guard cells.

A
  • Lowers the water potential of guard cells.
  • Water moves in by osmosis.
  • Guard cells becomes turgid, opening the stomata.
49
Q

Why is starch important for stomatal openings?

A

Starch is converted to malate ions.

Paper 3 - Bio (5 decks)

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