IB Biology HL D3.3 Homeostasis Questions

Practise IB Biology HL D3.3 by tracing glucose and temperature feedback, comparing diabetes evidence and explaining nephron filtration and ADH control.

129 questions in this syllabus scope, with question parts counted together.

Exam analysis

HL · 2010–2025

Papers with this topic65 / 117in the analysed sample

Latest appearanceNovember 2025

Tagged question parts96

Paper types5

Most tested objectives

D3.3.10 (HL)—Osmoregulation by collecting ducts19 papers
D3.3.7 (HL)—Kidney role14 papers
D3.3.8 (HL)—Glomerulus, Bowman's capsule, PCT12 papers
D3.3.4—Diabetes11 papers
D3.3.3—Blood glucose regulation9 papers

Common question formats

Definition or recall
Process explanation
Data analysis
Diagram interpretation
Calculation
Structured response

Recent exam appearances

November 2025Paper 2 HL · TZ1Q9(b)[ 7 ]

November 2025Paper 1A HL · TZ3Q31[ 1 ]

May 2025Paper 2 HL · TZ3Q2(a)(i)[ 1 ]

117 papers analysed · Tagging incomplete

Exam points

Define homeostasis from regulated variables such as blood pH, water balance and glucose.
Trace insulin/glucagon responses to blood-glucose changes and interpret glucose or turnover data.
Compare type I beta-cell destruction with type II insulin resistance, risk and treatment evidence.
Trace temperature feedback and predict vasomotor, sweating, shivering or heat responses.
Explain glomerular ultrafiltration, PCT reabsorption and urine formation from blood filtrate.
Relate loop-of-Henle salt transport and water permeability to the medullary gradient.
Trace osmoreceptor–ADH feedback, aquaporins and water reabsorption in collecting ducts.
Interpret exercise-related blood-flow changes as vasoconstriction or vasodilation to tissues.

Covered syllabus points

D3.3.1—Homeostasis definition D3.3.2—Negative feedback loops D3.3.3—Blood glucose regulation D3.3.4—Diabetes D3.3.5—Thermoregulation D3.3.6—Thermoregulation mechanisms D3.3.7 (HL)—Kidney role D3.3.8 (HL)—Glomerulus, Bowman's capsule, PCT D3.3.9 (HL)—Loop of Henle D3.3.10 (HL)—Osmoregulation by collecting ducts D3.3.11 (HL)—Blood supply changes

Exam points

Identify variables regulated by homeostasis, including blood pH, water balance and glucose, and recognize the normal range of blood pH.

[Maximum number: 6]

Explain how the pH of blood is kept constant during exercise.

a. pH of blood is regulated to stay within a narrow range/7.35 to 7.45

b. increase in $\mathrm{CO}_{2}$ produced during aerobic respiration «during exercise»

c. $\mathrm{CO}_{2}$ reacts with water to form carbonic acid

d. chemoreceptors detect drop in blood pH «when CO2 concentration rises» OR «increase in» $\mathrm{CO}_{2}$ lowers blood pH

e. carbonic acid dissociates to form hydrogen carbonate ions and hydrogen ions

f. hydrogencarbonate is alkaline/increases pH / neutralizes $\mathrm{H}^{+}$ ions $\boldsymbol{}$

g. hydrogen ions bind to plasma proteins/hemoglobin

h. stimulation of breathing centre/medulla oblongata

OR ventilation rate increased

i. faster diffusion/removal of $\mathrm{CO}_{2}$ «in alveoli/lungs»

Marking guidance:

Allow formula OWTTE

6 max

Exam points

Explain when pancreatic beta cells secrete insulin and when alpha cells secrete glucagon as blood glucose rises or falls.
Explain how insulin promotes glucose uptake or storage, while glucagon stimulates glycogen breakdown to change blood glucose levels.

[Maximum number: 1]

How is blood glucose regulated?

Deviation of blood
glucose level from normal

Hormone secreted
by pancreas

Effect

higher

glucagon

muscles break down
glycogen into glucose

higher

insulin

small intestine slows
glucose absorption

lower

glucagon

liver converts glycogen
to glucose

lower

insulin

kidney reabsorbs more
glucose

Exam points

Explain how autoimmune destruction of pancreatic beta cells reduces insulin production in Type 1 diabetes, and identify insulin replacement as a treatment.
Explain that Type 2 diabetes involves reduced insulin sensitivity or response, and link lifestyle risk factors such as obesity or inactivity to increased risk.

[Maximum number: 3]

DNA forms chromosomes, but much of eukaryote DNA is non-coding.

(a)

People can be analysed genetically for risks of specific diseases before they actually develop. One of these is type I diabetes.

[ 3 ]

(i)

Explain what happens in a person when they develop type I diabetes.

[ 2 ]

a. insulin is necessary to control/regulate blood glucose concentrations OR

insulin is necessary for the cells to take up glucose (for energy);

b. insufficient insulin is made by the pancreas OR autoimmune response/antibodies destroy the ( $\beta$ ) cells of the pancreas that make insulin;

c. reduced uptake of glucose from the blood / glucose accumulates in the blood / elevated blood glucose levels;

"sugar" is NOT accepted in place of glucose however this should only be penalized once;
i.e., utilize ECF;

(ii)

State how type I diabetes should be treated to avoid harmful health consequences of the condition.

[ 1 ]

Exam points

Explain how negative feedback maintains core temperature near 37 °C, with thermoreceptors signalling the hypothalamus to coordinate responses through the skin, muscles and other effectors.
Describe how sweating and changes in skin blood flow regulate heat loss, including cooling by sweat evaporation.

[Maximum number: 2]

The diagram shows water molecules as they might be arranged in liquid water and the interactions between them.

Outline the reasons for secretion of sweat in humans.

a. cooling/removing heat/lowering body temperature;
b. to prevent overheating
OR
to help maintain body temperature/for temperature homeostasis/for thermoregulation
OR
to keep temperature at $37^{\circ} \mathrm{C}$ ;
[2]

Exam points

Explain cooling at high body temperatures through sweating, vasodilation and increased blood flow to the skin.
Explain warming in cold conditions through vasoconstriction, shivering and heat generation by brown fat.

[Maximum number: 1]

The dark areas in the PET/CT scanning images show the activity of brown adipose tissue in an adult human at room temperature ( $20^{\circ} \mathrm{C}$ ) and $2^{\circ} \mathrm{C}$ .

How does brown adipose tissue contribute to regulating body temperature at $2^{\circ} \mathrm{C}$ ?

It provides adenosine triphosphate (ATP) for muscle contraction when shivering.

It further insulates the body so that internal heat is not lost.

It turns into thick layers of white adipose tissue to prevent hypothermia.

It breaks down fat to generate heat but not ATP.

Exam points

Explain how urea is filtered from blood and concentrated in urine as water is reabsorbed along the nephron.
Explain how filtration and selective reabsorption regulate urine water and ion concentrations, including ADH-dependent water reabsorption.

[Maximum number: 1]

The diagram shows blood flowing through a hemodialyser to treat kidney failure. The arrows show the direction of blood flow.

Which statement describes what happens in blood during hemodialysis?

Useful substances are selectively reabsorbed.

More urea will be found in the blood at Y than at X .

Hemodialysis removes all salts from the blood.

Glucose can diffuse into or out of the blood during hemodialysis.

Exam points

Explain ultrafiltration at the glomerulus, including how fenestrated capillaries allow filtrate to enter Bowman’s capsule.
Explain selective reabsorption in the PCT, including glucose transport and the return of water and useful solutes to the blood.

[Maximum number: 1]

The micrograph shows a glomerulus and Bowman's capsule, where ultrafiltration takes place in the kidney.

What facilitates the formation of glomerular filtrate?

Many fenestrations in walls of capillaries in the glomerulus

High pressure in the Bowman's capsule

ADH secreted by the pituitary gland

Osmosis caused by a high concentration of urea in the blood

Exam points

Explain how the Loop of Henle maintains a hypertonic medulla that supports concentrated urine.
Relate a long Loop of Henle to water conservation in mammals living in hot, dry environments.

[Maximum number: 1]

Merriam's kangaroo rat (Dipodomys merriami) is a small mammal found in desert biomes in the southwestern USA and Mexico. What would help these kangaroo rats to conserve water in order to survive high temperatures in desert biomes?

Increased sweating

A long loop of Henle

Decreased secretion of ADH

Decreased reabsorption from the collecting duct

Exam points

Explain how hypothalamic osmoreceptors control posterior-pituitary ADH release when blood osmolarity or water status changes.
Relate ADH to aquaporin insertion in collecting ducts, increased water reabsorption and production of concentrated urine.

[Maximum number: 1]

Antidiuretic hormone (ADH) is a peptide hormone that regulates the levels of water in the body. It is synthesized in the hypothalamus and stored in the posterior pituitary gland. The scattergraph shows the relationship between the osmolarity and ADH concentration in blood plasma.

State the relationship between osmolarity and ADH concentration of blood plasma.

Exam points

Explain how sympathetic vasoconstriction reduces gut blood flow while parasympathetic vasodilation increases it.
Explain why blood flow to the skin increases during exercise: increased skin perfusion helps remove heat.

[Maximum number: 6]

Compare how the sympathetic and parasympathetic nervous systems control processes such as heart rate, movements of the iris and flow of blood to the gut.

Exam analysis

Most tested objectives

Common question formats

Recent exam appearances

Covered syllabus points

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Question (a)

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Question (ii)

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