8. inorganic ions epqs Flashcards
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)
greater rate of oxygen consumption / leads to greater rate of respiration and
greater rate of uptake;
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;
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?
(ii) The initial length of the potato cylinder in the solution of concentration
0.1 mol dm–3 was 90 mm. Calculate its final length. Show your working. (2)
(iii) Explain the change in length which occurs in a sucrose solution of
concentration 0.5 mol dm–3.(2)
(i) 0.25 (mol dm–3);
(ii) 1 mark Incorrect answer but derived from ratio of 1.2 and initial length of 90 mm
2 marks Correct answer of 108 mm;
(iii) water potential inside potato higher / less negative than in solution; water moves out by osmosis;
Describe the roles of iron ions, sodium ions, and phosphate ions in cells. (5)
Must have MP1 for 5 max
3 max for sodium and 3 max for phosphate
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;
Accept 5. OR 6. – not both
7. Joins nucleotides/in phosphodiester bond/in backbone of
DNA/RNA/in nucleotides;
8. Used in/to produce ATP;
Reject ‘energy produced’
9. Phosphorylates other compounds (usually) making them more
reactive;
10. Hydrophilic/water soluble part of phospholipid bilayer/membrane;
Doctors investigated the link between high sodium concentrations in medicines
and hypertension (high blood pressure).
They analysed medical records of patients. 1 292 337 of these patients had taken
medicines containing high sodium concentrations. Each of these patients was
paired with a patient from a control group.
Give two factors that should have been the same for each pair of patients
and one factor that should have been different. (2)
Same
Accept any two of the following for one mark
1. BMI, age, sex/gender, other/previous medications, ethnicity, diet,
exercise, health (issues)
Different
2. No sodium in the (same) medicine;
Accept concentration of sodium in medicine
- (No for aspirin) 1.8 g;
- (Yes for paracetamol) 3.44 g;
A high concentration of sodium in the blood can affect blood volume and cause hypertension.
Use your knowledge of water potential to suggest how high sodium concentrations in the medicines taken could affect blood volume. (3)
- (Sodium ions) lower the water potential (of blood);
Accept make the blood water potential more negative
Accept decrease the blood water potential - Water would move into the blood by osmosis (from cells/tissue fluid);
- Increasing the blood volume;
Correct answer of 8513/8514 for 2 marks;;
Allow 1 mark for 61 127(.5401) in answer
Incorrect answer but shows sequence of 8513(6) with decimal point in any
position = 1 mark
