1.8- Inorganic ions

Question 1

1(a) Discs of carrot were placed in a solution containing potassium ions (K+
). The
concentration of oxygen in air bubbled through the solution was changed and the
rates of respiration and uptake of potassium ions were measured. The results are
shown in the table.
Describe and explain the link between oxygen concentration, rate of respiration and
rate of uptake of potassium ions. (4)

Answer 1

greater rate of oxygen consumption / leads to greater rate of respiration and
greater rate of uptake;
(allow this mark even if spread through account but
cause and effect must be within the correct context)
oxygen required for respiration;
respiration produces ATP / releases energy;
(ignore ref to producing or making energy)
potassium ions taken up by active transport / against concentration gradient;

Question 2

1b- Cylinders of potato were cut using a cork borer. Their initial lengths were
measured. Each cylinder was then put in a different concentration of sucrose
solution for 12 hours. The graph shows the changes in length of the potato cylinders
in the different sugar solutions
(i) In what concentration of sucrose did the length of the potato cylinder remain
the same? (1)

Answer 2

(b) (i) 0.25 (mol dm–3

Question 3

Explain the change in length which occurs in a sucrose solution of
concentration 0.5 mol dm–3 (2)
.

Answer 3

water potential inside potato higher / less negative than in solution;
water moves out by osmosis;

Question 4

Q2.Essay
You should write your essay in continuous prose.
Your essay will be marked for its scientific accuracy.
It will also be marked for your selection of relevant material from different parts of the
specification and for the quality of your written communication.
The maximum number of marks that can be awarded is

Scientific
Breadth of knowledge
Relevance
Quality of written
communication
16
3
3
3
Write an essay on the following topic:
Inorganic ions include those of sodium, phosphorus and hydrogen. Describe how these
and other inorganic ions are used in living organisms.  (25)

Answer 4

Topics

3. 1.3 Lipids
4. 1.5 Nucleic acids are important information-carrying molecules
5. 1.6 ATP
6. 2.3 Transport across cell membranes
7. 5.1 Photosynthesis
8. 5.2 Respiration
9. 5.4 Nutrient cycles
10. 6.2 Nervous coordination

Question 5

2018 p1 8.3.-
Scientists investigated the effect of a heat treatment on mass transport in barley box
plants.
• They applied steam to one short section of a leaf of the heat-treated plants. This
area is shown by the arrows in Figure 9.
• They did not apply steam to the leaves of control plants.
• They then supplied carbon dioxide containing radioactively-labelled carbon to each
plant in the area shown by the rectangular boxes in Figure 9.
• After 4 hours, they:
• found the position of the radioactively-labelled carbon in each plant. These
results are shown in Figure 9.
• recorded the water content of the parts of the leaf that were supplied with
radioactively-labelled carbon dioxide. These results are shown in Table 4.
The scientists then investigated the movement of iron ions (Fe3+) from the soil to old
and young leaves of heat-treated barley plants and to leaves of plants that were not
heat treated. Heat treatment was applied half way up the leaves. The scientists
determined the concentration of Fe3+ in the top and lower halves of the leaves of each
plant.
Their results are shown in Figure 10.

What can you conclude about the movement of Fe3+ box in barley plants?
Use all the information provided.
[4 marks]

Answer 5

1. Heat treatment has a greater effect on young
   leaves than old;
2. Heat treatment damages the phloem;
3. Fe3+ moves up the leaf/plant;
4. (Suggests) Fe3+ is transported in the xylem in
   older leaf;
5. In young leaf, some in xylem, as some still
   reaches top part of leaf;
6. (Suggests) Fe3+ is (mostly) transported in phloem
   in young leaf
   OR
   Xylem is damaged in young leaf
   OR
   Xylem is alive in young leaf;
7. Higher ratio of Fe3+ in (all/untreated) old leaves
   than (all/untreated) young;
8. All ratios show there is less Fe3+ in the top than
   the lower part of leaves;
9. (But) no statistical test to show if the difference(s)
   is significant;

Question 6

Give two similarities between the processes by which inorganic ions and water molecules enter cells (1)

Answer 6

Both move down conc gradient

both move through protein channels in the cell membrances to enter cells

Question 7

0 9 box . 1 Describe the roles of iron ions, sodium ions, and phosphate ions in cells.
[5 marks]

Answer 7

Iron ions
1. Haemoglobin binds/associates with
oxygen
OR
Haemoglobin transports/loads
oxygen;
Sodium ions
2. Co-transport of glucose/amino
acids (into cells);
3. (Because) sodium moved out by
active transport/Na – K pump;
4. Creates a sodium
concentration/diffusion gradient;
5. Affects osmosis/water potential;
Phosphate ions
6. Affects osmosis/water potential;
7. Joins nucleotides/in
phosphodiester bond/in backbone
of DNA/RNA/in nucleotides;
8. Used in/to produce ATP;
9. Phosphorylates other compounds
(usually) making them more
reactive;
10. Hydrophilic/water soluble part of
phospholipid bilayer/membrane;