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A-level Biology > 6 - Exchange > Flashcards

6 - Exchange Flashcards

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1
Q

In what form should a surface area : volume ratio be given?

A

n:1

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2
Q

How does the SA:V ratio of an organism change as the size of an organism increases?

A

Decreases

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3
Q

Give two reasons why a specialised system is needed for gas exchange?

A

Supply of oxygen
Removal of carbon dioxide

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4
Q

Why is diffusion not a viable mode of gas transport for large multicellular organisms?

A

Time taken for oxygen to diffuse from cell-surface membrane to tissues would be too long as greater diffusion distance

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5
Q

How does gas exchange occur in insects?

A
  1. Gas enters via spiracles
  2. Gas travels through trachea and tracheoles
  3. Directly to every tissue
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6
Q

Describe counter-current flow in fish gas exchange.

A
  • Blood and water flow in opposite directions
  • Diffusion gradient maintained along length of lamellae
  • Water always has higher oxygen concentration than blood
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7
Q

Where does gas exchange occur in dicotlyedonous plants?

A

In the leaves

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8
Q

Give 5 adaptations of xerophile plants to limit the loss of water through gas exchange.

A
  • Hairs
  • Waxy cuticle
  • Small leaves
  • Sunken stomata
  • Rolled leaves
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9
Q

How can insects control/limit water loss?

A
  • Opening and closing of stomata
  • Hair around spiracles
  • Waterproof waxy cuticle
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10
Q

Give four adaptations of alveoli for gas exchange.

A
  • Large surface area : Volume
  • Rich capillary network/good blood supply
  • Thin (1 cell) walls
  • Elastic fibres to aid recoil
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11
Q

Describe inspiration.

A
  • External intercostal muscles contract
  • Rib cage moves up and out
  • Diaphragm contracts
  • Volume of thorax increases
  • Atmospheric pressure greater than pulmonary pressure
  • Air enters lungs due to pressure gradient
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12
Q

Describe expiration.

A
  • Internal intercostal muscles contract
  • Ribs move down and inwards
  • Diaphragm relaxes
  • Volume of thorax decreases
  • Pulmonary pressure greater than atmospheric pressure
  • Air exits lungs due to pressure gradient
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13
Q

What is tidal volume ?

A

The volume of air moved in and out of the lungs in a normal breath

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14
Q

What is pulmonary ventilation rate?

A

Total volume of air moved into the lungs during a minute

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15
Q

How is pulmonary ventilation rate calculated?

A

Tidal volume x Breathing rate

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16
Q

What are proteins hydrolysed to?

A

Amino acids

17
Q

What is the function of endopeptidases?

A

Hydrolyse peptide bonds between specific amino acids in the middle of a polypeptide

18
Q

What is the function of exopeptidases?

A

Hydrolyse peptide bones between specific amino acids at the ends of a polypeptide

19
Q

What is the function of a dipeptidase?

A

Hydrolyse peptide bond in a dipeptide

20
Q

What is produced when an exopeptidase acts?

A

One amino acid/dipeptide, and a polypeptide

21
Q

What is produced when an endopeptidase acts?

A

Two shorter polypeptides

22
Q

What are lipids digested to?

A

Monoglyceride and fatty acids

23
Q

Where does absorption of the products of digestion occur?

A

Ileum of the small intestine

24
Q

What is the function of bile salts?

A

Emulsify lipids to increase SA of lipids to increase action of lipases. Produce micelles.

25
Q

What are micelles?

A

The products of lipid digestion that remain in association with bile salts to form structures.
They travel to the ileum where they are broken down in contact with the surface of ileum epithelium cells.

26
Q

How are amino acids and carbohydrates absorbed in the ileum?

A

Co-transport with sodium

27
Q

Explain how are monoglycerides and fatty acids are absorbed into epithelial cells.

A

They are non-polar
So diffuse across the the phospholipid bilayer

28
Q

Describe and explain one feature of the alveolar epithelium which makes the epthelium well adapted for gas exchange. Do not refer to SA or moisture. (2)

A

Single layer of cells
Reduces diffusion distance

29
Q

Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and alveoli. (3)

A
  • Less carbon dioxide moves out of lungs
  • Reduced concentration gradient between blood and alveoli
  • Less movement of carbon dioxide out of blood
30
Q

A high concentration of particulate matter results in the death of some
alveolar epithelium cells. If alveolar epithelium cells die inside the human
body they are replaced by non-specialised, thickened tissue.
Explain why death of alveolar epithelium cells reduces gas exchange in
human lungs. (3)

A
  • Reduced SA
  • Increased diffusion distance
  • Reduced rate of gas exchange
31
Q

Use your knowledge of gas exchange in leaves to explain why plants
grown in soil with very little water grow only slowly. (2)

A
  • Stomata close
  • Less carbon dioxide intake for photosynthesis
32
Q

Describe the pathway taken by an oxygen molecule from an alveolus to the
blood. (2)

A
  1. Alveolar epithelium
  2. Capillary epithelium
33
Q

Explain how one feature of an alveolus allows efficient gas exchange to
occur.

A
  • One cell thick
  • Reduced diffusion distance
34
Q

Explain three ways in which an insect’s tracheal system is adapted for
efficient gas exchange. (3)

A
  • Higher branched so large surface area
  • Thin walls so short diffusion distance
  • Trachae provide tubes full of air so fast diffusion
35
Q

The damselfly larva is a carnivore that actively hunts prey. It has gills to
obtain oxygen from water.
Some other species of insect have larvae that are a similar size and shape
to damselfly larvae and also live in water. These larvae do not actively
hunt prey and do not have gills.
Explain how the presence of gills adapts the damselfly to its way of life. (2)

A
  • Higher metabolic rate
  • Uses more oxygen
36
Q

Explain two ways in which the structure of fish gills is adapted for efficient
gas exchange. (2)

A
  • Many lamellae so large SA
  • Thin so short diffusion pathway

A-level Biology (21 decks)

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