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IB Biology HL D3.3 Homeostasis Questions

Practise IB Biology HL D3.3 by explaining feedback control, blood glucose, thermoregulation, ultrafiltration and ADH responses.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • identify the regulated variable, receptor, control centre and effector in a negative-feedback loop
  • explain insulin and glucagon control of blood glucose and distinguish type 1 from type 2 diabetes
  • predict sweating, vasodilation, vasoconstriction or heat production from a temperature change
  • trace ultrafiltration and selective reabsorption through the glomerulus, Bowman's capsule and PCT
  • explain how the loop of Henle and ADH-controlled aquaporins produce concentrated or dilute urine

Covered syllabus points

D3.3.1—Homeostasis definitionD3.3.2—Negative feedback loopsD3.3.3—Blood glucose regulationD3.3.4—DiabetesD3.3.5—ThermoregulationD3.3.6—Thermoregulation mechanismsD3.3.7 (HL)—Kidney roleD3.3.8 (HL)—Glomerulus, Bowman's capsule, PCTD3.3.9 (HL)—Loop of HenleD3.3.10 (HL)—Osmoregulation by collecting ductsD3.3.11 (HL)—Blood supply changes

Question 1

[Maximum number: 1]

The dimensions of four structures were measured in the hearts of eleven patients with anorexia and in the same number of control subjects.
(a) Discuss the support provided by the data for the claim that anorexia leads to the breakdown of heart tissue.
(b) In control subjects, blood potassium levels are maintained, through homeostasis, between 3.5 and 4.5 mmol litre −1{ }^{-1}. In patients with anorexia, blood potassium can fall below this level. This is known as hypokalemia. In patients with kidney failure, levels can rise above this range, causing hyperkalemia. The traces show the electrocardiograms (ECGs) of a patient with hypokalemia, a normal subject and a patient with hyperkalemia.

Figure for Question 1 — IB Biology HL

Sometimes hyperkalemia occurs as a body tries to respond to low blood pH . State the normal range of blood pH in the human body.

Question 2

[Maximum number: 7]

Living organisms have mechanisms for preventing or reducing change.

Describe the mechanisms used to keep blood glucose levels within narrow limits in humans.

Question 3

[Maximum number: 5]

Type I diabetes is a leading cause of death in advanced countries and is associated with various severe or fatal complications, including blindness, kidney failure, heart disease, stroke, neuropathy, and amputations. Embryonic stem cells are considered to be a powerful tool in the treatment of diabetes.

In a study, embryonic stem cells were grown in culture and tested for insulin mRNA. A drug was injected into two groups of healthy mice in order to simulate type I diabetes 15 days prior to the transplant of embryonic stem cells. The mice in the transplant group received embryonic stem cells that produce insulin mRNA. The control group did not receive the transplant. The graph shows the blood glucose concentration in both groups.

Figure for Question 3 — IB Biology HL

Question (a)

(a)

Outline the cause of type I diabetes in humans.

[ 1 ]

Question (b)

(b)

Compare and contrast the concentration of blood glucose resulting from the embryonic stem cell transplant with the control.

[ 2 ]

Question (c)

(c)

Evaluate the effectiveness of the embryonic stem cell treatment in controlling blood glucose.

In a second study, a group of patients recently diagnosed with type I diabetes received a transplant of stem cells. Based on their need for insulin after the transplant, participants were divided into two groups. Their C-peptide production levels were measured for 24 months as the levels indicate the degree of pancreatic beta-cell function. Group 1 did not require insulin and group 2 required insulin occasionally during the study. The graphs show the levels of C-peptides in each individual of both groups 1 and 2.

Graphs removed for copyright reasons

[ 2 ]
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