6 - Exchange Flashcards
In what form should a surface area : volume ratio be given?
n:1
How does the SA:V ratio of an organism change as the size of an organism increases?
Decreases
Give two reasons why a specialised system is needed for gas exchange?
Supply of oxygen
Removal of carbon dioxide
Why is diffusion not a viable mode of gas transport for large multicellular organisms?
Time taken for oxygen to diffuse from cell-surface membrane to tissues would be too long as greater diffusion distance
How does gas exchange occur in insects?
- Gas enters via spiracles
- Gas travels through trachea and tracheoles
- Directly to every tissue
Describe counter-current flow in fish gas exchange.
- Blood and water flow in opposite directions
- Diffusion gradient maintained along length of lamellae
- Water always has higher oxygen concentration than blood
Where does gas exchange occur in dicotlyedonous plants?
In the leaves
Give 5 adaptations of xerophile plants to limit the loss of water through gas exchange.
- Hairs
- Waxy cuticle
- Small leaves
- Sunken stomata
- Rolled leaves
How can insects control/limit water loss?
- Opening and closing of stomata
- Hair around spiracles
- Waterproof waxy cuticle
Give four adaptations of alveoli for gas exchange.
- Large surface area : Volume
- Rich capillary network/good blood supply
- Thin (1 cell) walls
- Elastic fibres to aid recoil
Describe inspiration.
- 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
Describe expiration.
- 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
What is tidal volume ?
The volume of air moved in and out of the lungs in a normal breath
What is pulmonary ventilation rate?
Total volume of air moved into the lungs during a minute
How is pulmonary ventilation rate calculated?
Tidal volume x Breathing rate
What are proteins hydrolysed to?
Amino acids
What is the function of endopeptidases?
Hydrolyse peptide bonds between specific amino acids in the middle of a polypeptide
What is the function of exopeptidases?
Hydrolyse peptide bones between specific amino acids at the ends of a polypeptide
What is the function of a dipeptidase?
Hydrolyse peptide bond in a dipeptide
What is produced when an exopeptidase acts?
One amino acid/dipeptide, and a polypeptide
What is produced when an endopeptidase acts?
Two shorter polypeptides
What are lipids digested to?
Monoglyceride and fatty acids
Where does absorption of the products of digestion occur?
Ileum of the small intestine
What is the function of bile salts?
Emulsify lipids to increase SA of lipids to increase action of lipases. Produce micelles.
What are micelles?
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.
How are amino acids and carbohydrates absorbed in the ileum?
Co-transport with sodium
Explain how are monoglycerides and fatty acids are absorbed into epithelial cells.
They are non-polar
So diffuse across the the phospholipid bilayer
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)
Single layer of cells
Reduces diffusion distance
Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and alveoli. (3)
- Less carbon dioxide moves out of lungs
- Reduced concentration gradient between blood and alveoli
- Less movement of carbon dioxide out of blood
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)
- Reduced SA
- Increased diffusion distance
- Reduced rate of gas exchange
Use your knowledge of gas exchange in leaves to explain why plants
grown in soil with very little water grow only slowly. (2)
- Stomata close
- Less carbon dioxide intake for photosynthesis
Describe the pathway taken by an oxygen molecule from an alveolus to the
blood. (2)
- Alveolar epithelium
- Capillary epithelium
Explain how one feature of an alveolus allows efficient gas exchange to
occur.
- One cell thick
- Reduced diffusion distance
Explain three ways in which an insect’s tracheal system is adapted for
efficient gas exchange. (3)
- Higher branched so large surface area
- Thin walls so short diffusion distance
- Trachae provide tubes full of air so fast diffusion
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)
- Higher metabolic rate
- Uses more oxygen
Explain two ways in which the structure of fish gills is adapted for efficient
gas exchange. (2)
- Many lamellae so large SA
- Thin so short diffusion pathway
