Bio- Unit F211: Cells, Exchange and Transport

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Why is the alveolus wall an efficient gaseous exchange surface?
The alveolus wall is an efficient exchange surface as it is only one cell thick. It is moist and is highly folded for a large surface area.
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What is the advantage of having a network of capillaries surrounding the alveoli?
The alveoli are supplied with a rich network of capillaries which carry blood close to the alveolus wall (the exchange surface). Therefore making the diffusion distance shorter.
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What are the role of the intercostal and outercostal muscles, concerning breathing?
Muscles (e.g. the diaphragm) move air in and out of the lungs (ventilation). Along with the constant blood supply, this keeps up a concentration gradient of O2 & CO2. Refreshing of air.
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What effect do the features of the lungs exchange surface have on the rate of diffusion?
These features increase the rate of diffusion of O2 into the blood from the alveolus and CO2 out of the blood into the alveolus.
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What do the trachea and bronchi have that the bronchioles and alveoli don't?
The trachea and bronchi have rings of cartilage which keep them open for airflow during ventilation.
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What is the role of smooth muscle and elastic tissue in the bronchi and bronchioles?
Smooth muscle contracts and narrows the bronchi and bronchioles and elastic tissue opens these airways. This controls airflow.
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What is the role of goblet cells?
Goblet cells in the lining of the trachea, bronchi and bronchioles secrete mucus which traps particles (e.g. pollen and bacteria).
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How do ciliated epithelial cells work together with goblet cells?
Ciliated epithelial cells in the lining beat upwards. This removes any swallowed mucus or particles, keeping the lungs clean.
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Do larger organisms have a small or large surface area:volume and why?
Large multicellular animals have a small surface area for their volume, resulting in a large distance for diffusion of gases.
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Why do larger organisms require a specialised transport system?
They need a special transport (blood) system to supply O2 and remove CO2, especially if very active (e.g. birds, mammals and fish).
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Describe how the single and double circulatory system works.
Single system (fish): heart – gills – body – heart. Double system (mammals): left heart – body – right heart – lungs – left heart.
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What is meant by an open and closed circulatory system?
Closed circulatory system (fish, birds and mammals): blood stays in blood vessels. Open system (insects): blood leaves vessels.
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Where do the left and right ventricles pump blood to?
The left ventricle wall (thick) pumps blood around the body. The right ventricle wall (thinner) only has to pump blood to the lungs.
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Why are the atrial walls thin?
Atrial walls are very thin since they only have to pump blood a short distance into the ventricles.
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What does the cardiac cycle consist of?
Cardiac cycle: chambers fill; ventricles contract (cuspid AV valves close, “lub” sound); atria contract (semi-lunar valves close, “dub” sound).
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What route does the SA node take and begin at?
The Sino-Atrial Node (in right atrium) maintains beat rhythm. The AtrioVentricular Node and Purkyne fibres pass the beat on to ventricles. Pause at Av node- allowing ventricles to fully fill. (Bundle of his)
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What does blood contain?
Blood contains cells, plasma proteins and dissolved substances such as glucose and platelets.
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What is tissue fluid?
Tissue fluid is blood minus cells and plasma proteins. Has a higher water potential than blood plasma. Surrounds lymphatic system (filtration)
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Where does Haemoglobin pick up O2 the easiest?
Haemoglobin (Hb) in red blood cells picks up O2 easily at the lungs where O2 pressure is high (Hb dissociation curve is to the left and S-shaped) and releases it at tissues where O2 pressure is low.
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What happens to CO2 when combined with Hb?
CO2 from tissues combines with Hb, making it release O2 (CO2 makes the dissociation curve move to the right). This Bohr effect means more O2 for active tissues. The CO2 diffuses into plasma.
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How is water and minerals taken up by roots?
Water and dissolved minerals taken up by roots via osmosis and are carried by an open tube of dead cells (xylem vessels) up the stem to leaves.
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Name the 3 pathways that can be taken by water to reach the xylem.
Water gets to the xylem across the root cortex by the apoplast (cell wall), symplast (cytoplasm) and vacuolar pathways.
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What is the role of the Casparian strip in endodermis cells?
The waterproof Casparian strip in endodermis cells forces water into the symplast. This creates root pressure in the xylem.
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What is the transpiration stream and how does it work?
The transpiration stream pulls water up the xylem. Cohesion holds water molecules together; adhesion holds them to the xylem walls.
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Other cards in this set

Card 2

Front

What is the advantage of having a network of capillaries surrounding the alveoli?

Back

The alveoli are supplied with a rich network of capillaries which carry blood close to the alveolus wall (the exchange surface). Therefore making the diffusion distance shorter.

Card 3

Front

What are the role of the intercostal and outercostal muscles, concerning breathing?

Back

Preview of the front of card 3

Card 4

Front

What effect do the features of the lungs exchange surface have on the rate of diffusion?

Back

Preview of the front of card 4

Card 5

Front

What do the trachea and bronchi have that the bronchioles and alveoli don't?

Back

Preview of the front of card 5
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