5.2 Water for Transport Questions and Answers

5.2 Water for transport – Questions and answers

Q1.

Bk Ch5 S5.2 Q1

Complete the table below, summarising the composition of the blood.

A1.

Bk Ch5 S5.2 A1

Q2.

Bk Ch5 S5.2 Q2

For each of the following substances carried in the bloodstream, identify the

aform in which it is carried, and

bthe blood component that transports it.

oxygen carbon dioxide water salts nitrogenous wastes products of digestion

A2.

Bk Ch5 S5.2 A2

a and bOxygen is carried as oxyhaemoglobin in red blood cells. Carbon dioxide is mainly carried as hydrogen carbonate ions in the red blood cell; some also combines with the haemoglobin in red blood cells to form carbaminohaemoglobin; the remainder is dissolved directly in the blood plasma. Water is the main component of the plasma and carries a range of dissolved materials including mineral ions and bicarbonate ions. Salts are carried dissolved in the plasma as ions. Nitrogenous wastes are carried dissolved in the plasma in the form of urea. The products of digestion, such as simple sugars and amino acids, are carried in dissolved form in the plasma.

Q3.

Bk Ch5 S5.2 Q3

aWhy do cells require oxygen?

bExplain why carbon dioxide must be removed from cells.

A3.

Bk Ch5 S5.2 A3

aCells need oxygen for cellular respiration, the process in which energy is made available to cells.

bCarbon dioxide is a waste material produced by cells. In high concentrations it causes damage to cells and the body so must be removed.

Q4.

Bk Ch5 S5.2 Q4

Red blood cells contain the pigment haemoglobin. Explain how haemoglobin assists red blood cells in their specialised function.

A4.

Bk Ch5 S5.2 A4

Red blood cells contain the pigment haemoglobin. Each haemoglobin molecule has four active sites to which oxygen molecules become attached. Haemoglobin increases the oxygen-carrying capacity of the blood by about 100 times compared to the amount of oxygen that can be carried as dissolved ions in the plasma.

Q5.

Bk Ch5 S5.2 Q5

Complete the following table, comparing the structure and function of blood vessels.

A5.

Bk Ch5 S5.2 A5

Q6.

Bk Ch5 S5.2 Q6

An oximeter is a device used to measure the oxygen saturation of the blood. Explain why is it important to monitor blood oxygen saturation during surgery.

A6.

Bk Ch5 S5.2 A6

It is important to monitor blood oxygen saturation during surgery to ensure that sufficient oxygen is available to all body cells for cellular respiration. If a lack of oxygen occurs damage to cells can occur. Monitoring blood oxygen levels alerts surgeons to any drop below a safe level so that corrective steps can be taken.

Q7.

Bk Ch5 S5.2 Q7

Summarise the pathways and processes involved in the upward movement of water in plants.

A7.

Bk Ch5 S5.2 A7

Water is transported in plants through the xylem. Xylem is composed of xylem vessels, tracheids, fibres and parenchyma. Xylem vessels are long and open-ended, forming a continuous tube. Tracheids have pits in their walls so that where one tracheid overlaps with another water can pass through. Tracheids also have lignin deposits that give strength and impermeability to the vessels. Water enters the plant at the roots by osmosis and moves into the xylem vessels to travel in an upward direction through the stems and leaves.

The upward movement of water depends on several factors. The xylem tubes are very narrow, accounting for some upward movement by capillarity caused by the strong cohesive forces between water molecules. There is also an adhesive force between the water molecules and the cellulose walls of the xylem that pulls water upwards. Finally the evaporation of water at the leaves and the transpiration stream are responsible for water movement. As water vapour is evaporated from the leaves via the stomates the water column is drawn up through the xylem to replace the water loss.

Q8.

Bk Ch5 S5.2 Q8

Outline how the theories of symplastic loading and apoplastic loading are thought to account for the movement of materials into the phloem at the leaves.

A8.

Bk Ch5 S5.2 A8

Symplastic loading and apoplastic loading are two theories that are believed to be responsible for the movement of photosynthetic materials from their source into the phloem. In symplastic loading sugars travel from the mesophyll cells where they are formed through plasmodesmata present between the leaf cells until they reach the sieve elements of the phloem. In apoplastic loading sugars travel along a pathway through the cell walls between the mesophyll cells and the sieve elements. These materials then cross the cell membrane of the sieve elements by active transport.

Q9.

Bk Ch5 S5.2 Q9

Draw up a table comparing the xylem and phloem in the transport system of plants. Your table should include:

• the kinds of materials transported
• the direction of flow
• whether the conducting tissue is living or non-living
• a brief description of the structure of the tissues
• whether the process of transporting materials requires energy or not.

A10.

Bk Ch5 S5.2 A10

5.2 Water for transport QApage 1 of 4

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