| Date | November 2018 | Marks available | 6 | Reference code | 18N.3.HL.TZ0.21 |
| Level | Higher level | Paper | Paper 3 | Time zone | TZ0 / no time zone |
| Command term | Explain | Question number | 21 | Adapted from | N/A |
Question
Explain how the pH of blood is kept constant during exercise.
Markscheme
a. pH of blood is regulated to stay within a narrow range/7.35 to 7.45 ✔
If values provided, both required
b. increase in CO2 produced during aerobic respiration «during exercise» ✔
c. CO2 reacts with water to form carbonic acid ✔
d. chemoreceptors detect drop in blood pH «when CO2 concentration rises»
OR
«increase in» CO2 lowers blood pH ✔
e. carbonic acid dissociates to form hydrogen carbonate ions and hydrogen ions ✔
Allow formula
f. hydrogencarbonate is alkaline/increases pH/neutralizes H+ ions ✔
OWTTE
g. hydrogen ions bind to plasma proteins/hemoglobin ✔
h. stimulation of breathing centre/medulla oblongata
OR
ventilation rate increased ✔
i. faster diffusion/removal of CO2 «in alveoli/lungs» ✔
Examiners report
Syllabus sections
- 22M.1.HL.TZ1.40: What is the role of HCG in early pregnancy? A. It prevents the degeneration of the corpus...
-
17M.3.HL.TZ1.20a:
A good marker of dietary intake of iodine is the urinary iodine level (UI). A study was carried out in the UK to establish urinary iodine levels and milk intake in schoolgirls aged 14–15 years.
Urinary iodine values from 50 to 99 μg dm–3 are considered to be mild iodine deficiency. Deduce the effect of milk intake on the iodine status of schoolgirls in the UK.
- 19M.3.HL.TZ1.20a: Deduce from the results of the study whether HGH improves strength.
- 17M.1.SL.TZ1.10: The graph shows the effect of increasing the substrate concentration on the rate of an...
- 16N.3.HL.TZ0.20c: Compare and contrast the mechanisms of action of peptide and steroid hormones.
- 18N.3.HL.TZ0.20a.i: Using the diagram, identify an organ containing an exocrine gland.
- 18N.3.HL.TZ0.20a.ii: Using the diagram, identify a hormone involved in the development of a follicle.
- 18N.3.HL.TZ0.20c: List two hormones produced by the posterior pituitary gland.
- 18N.3.HL.TZ0.20b: State two effects of prolactin.
-
18M.3.HL.TZ1.19c:
Describe the mode of action of steroid hormones.
- 18N.3.HL.TZ0.20a.iii: Using the diagram, identify a steroid hormone.
- 19M.3.HL.TZ1.20b: Suggest one reason that it is difficult to detect illegal use of HGH to enhance athletic...
-
19N.3.HL.TZ0.22b:
Distinguish between the mode of action of steroid hormones and peptide hormones.
- 19M.3.HL.TZ1.20c: HGH is a peptide hormone. Describe the mode of action of peptide hormones on target cells.
-
20N.3.HL.TZ0.24:
Explain how steroid and peptide hormones exert their effect.
-
17N.3.HL.TZ0.20a.i:
Thyroxin is a hormone produced in the thyroid gland. State one function of thyroxin.
-
16N.3.HL.TZ0.20a:
On the diagram, label a
(i) second messenger.
(ii) gene regulatory protein.
- 16N.3.HL.TZ0.20b: Outline one characteristic of steroid hormones that allows them to readily diffuse through...
- 19N.3.HL.TZ0.22c: Identify with reasons whether the pituitary gland is an exocrine or endocrine gland.
-
18M.3.HL.TZ2.23:
Compare and contrast steroid and peptide hormone action.
- 17M.3.HL.TZ1.21b.ii: Explain how the increase in CO2 concentration affects the release of oxygen to respiring cells.
-
17N.3.HL.TZ0.20a.ii:
The action of thyroxin is similar to steroid hormones. Describe the action of steroid hormones.
-
17N.3.HL.TZ0.20b:
The World Health Organization recommends that the iodine intake should be supplemented in pregnant women due to their increased requirements. Outline the need for iodine supplementation.
- 17M.3.HL.TZ1.20b: Outline the need for iodine in the endocrine system.
- 17M.3.HL.TZ1.20c: Growth hormones are examples of peptide hormones. Explain the mechanism of action of peptide...
- 19N.2.HL.TZ0.1h: Using all the data, discuss whether inoculating mice with the antigen to B. burgdorferi could...
-
17M.3.HL.TZ2.22:
Explain the role of receptors in mediating the action of both steroid and protein hormones.
- 19N.3.HL.TZ0.22a: Athletes taking growth hormones show an increase in their sprinting capacity. This is not...
