IB Biology HL A2.2 Cell structure Questions

Practise IB Biology HL A2.2 with micrograph and data questions on cell theory, microscopy, organelles, endosymbiosis, differentiation and structure–function evidence.

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

Exam analysis

HL · 2010–2025

Papers with this topic58 / 117in the analysed sample

Latest appearanceNovember 2025

Tagged question parts86

Paper types5

Most tested objectives

A2.2.2—Microscopy skills19 papers
A2.2.5—Prokaryote cell structure13 papers
A2.2.12 (HL)—Endosymbiosis origin of eukaryotes12 papers
A2.2.9—Atypical cell structure6 papers
A2.2.7—Processes of life in unicellular organisms5 papers

Common question formats

Definition or recall
Graph interpretation
Process explanation
Calculation
Evaluation
Structured response

Recent exam appearances

November 2025Paper 1B HL · TZ3Q1(a), 1(b)(i), 1(b)(ii), 1(c)[ 5 ]

November 2025Paper 1A HL · TZ3Q12[ 1 ]

May 2025Paper 2 HL · TZ2Q8(a)[ 3 ]

117 papers analysed · Tagging incomplete

Exam points

State that organisms are composed of cells and that cells are the basic units of life, using pre-existing-cell evidence where assessed.
Calculate magnification or actual cell size, calibrate eyepiece graticules and outline safe focusing for light microscopy.
Compare light and electron microscopy and identify cryogenic or fluorescent techniques from resolution, preparation and imaging purpose.
Compare prokaryotic and eukaryotic cells, then label prokaryotic structures and link plasmids, pili, flagella or ribosomes to function.
Relate eukaryotic organelle compartmentalization and plant, animal or fungal structures to respiration, photosynthesis, transport, protein processing or cell support.
Explain how unicellular organisms carry out nutrition, response, homeostasis, growth and reproduction in one cell.
Explain how atypical multinucleate or anucleate cells challenge simple cell-theory expectations and identify cells or organelles in micrographs using structural evidence.
Evaluate endosymbiosis using engulfment and organelle–prokaryote similarities such as circular DNA, 70S ribosomes and double membranes.
Link selective gene expression in same-genome cells to different proteomes and specialised cell function.

Covered syllabus points

A2.2.1—Cells as basic structural unit A2.2.2—Microscopy skills A2.2.3—Developments in microscopy A2.2.4—Structures common to all cells A2.2.5—Prokaryote cell structure A2.2.6—Eukaryote cell structure A2.2.7—Processes of life in unicellular organisms A2.2.8—Differences in eukaryotic cells A2.2.9—Atypical cell structure A2.2.10—Cell identification in micrographs A2.2.11—Drawing and annotation A2.2.12 (HL)—Endosymbiosis origin of eukaryotes A2.2.13 (HL)—Cell differentiation A2.2.14 (HL)—Evolution of multicellularity

Exam points

Describe cells as the basic structural and functional units of living organisms.
State that cells carry out essential life processes and are usually microscopic.

[Maximum number: 3]

Pictured below are Louis Pasteur's original drawings of swan-necked flasks.

Describe how Pasteur's experiments provided convincing evidence to falsify the concept of spontaneous generation.

Exam points

Describe how to prepare and stain cell mounts for observation with a light microscope.
Measure cells using an eyepiece graticule and a stage micrometer.
Calculate magnification and actual size, and use or construct scale bars.

[Maximum number: 2]

The micrograph shows a buttercup (Ranunculus bulbosus) stem in transverse section. Region T has been highlighted to show more detail.

(a)

Calculate the actual thickness of the stem, measured by the line AB that has been magnified $100 \times$ .

[ 1 ]

$0.45 \mathrm{~mm} / 0.045 \mathrm{~cm} / 450 \mu \mathrm{~m}$ ;

Units required for the mark.

Marking guidance:

Accept answers in the ranges of $0.42-0.47 \mathrm{~mm} /$ $0.042-0.047 \mathrm{~cm} / 420-470 \mu \mathrm{~m}$ .

(b)

Outline how the actual thickness of the stem could be calculated using a microscope with an eyepiece graticule.

[ 1 ]

Exam points

Explain why resolution, not magnification alone, determines the detail visible in a microscope image.
Distinguish TEM imaging of internal ultrastructure from SEM imaging of surface detail.
Describe how cryogenic electron microscopy, fluorescence and immunofluorescence reveal molecules or specific structures.

[Maximum number: 1]

What is a feature of immunofluorescence in light microscopy?

Can only be used on dead cells

Enables higher resolution

Attaches a fluorescent stain to an antibody

Attaches a fluorescent stain to an antigen

[Maximum number: 1]

The image shows a phagocytic white blood cell as seen with a transmission electron microscope.

Which features can be found both within this cell and in a photosynthetic bacterium?

Chloroplasts

Multiple nuclei

70S ribosomes

Lysosomes

Exam points

Explain that prokaryotes lack a nucleus and membrane-bound organelles.
Identify the cell wall, plasma membrane, cytoplasm, 70S ribosomes, naked circular DNA and plasmids in prokaryotic cells.
Recognise E. coli, Bacillus and Staphylococcus as bacterial examples.

[Maximum number: 1]

Molecular visualization software was used to produce the representation of a human nucleosome.

Suggest a reason that nucleosomes are absent in bacterial DNA.

Exam points

Describe the nucleus, 80S ribosomes, cytoskeleton and compartmentalised cytoplasm as features of eukaryotic cells.
Identify mitochondria, endoplasmic reticulum, Golgi apparatus, vesicles, lysosomes and vacuoles as eukaryotic organelles.
Identify chloroplasts, large vacuoles and cellulose cell walls as possible features of plant cells.

[Maximum number: 1]

What is a difference between eukaryotic and prokaryotic cells?

Cell walls are found only in prokaryotes.

Naked DNA with histones is found only in prokaryotes.

Compartmentalization is found only in eukaryotes.

Cilia and flagella are found only in prokaryotes.

Exam points

State that unicellular organisms carry out all life processes within one cell.
Identify Amoeba, Chlamydomonas and Escherichia coli as examples of unicellular organisms.
Identify nutrition, metabolism, response, excretion, homeostasis, growth and reproduction as life processes carried out by unicellular organisms.

[Maximum number: 1]

Which function is accomplished by structures X and Y in the Paramecium?

Exam points

Compare plant, animal and fungal cells by their cell walls, vacuoles and storage structures.
Identify cellulose cell walls, chloroplasts and large permanent vacuoles as features of plant cells.
Identify centrioles, cilia, flagella, lysosomes and temporary vacuoles as structures that may occur in animal cells.

[Maximum number: 1]

Chlorella and Paramecium are both unicellular eukaryotic organisms living in freshwater. Chlorella is photosynthetic and has a cell wall. Which organelle will be found in Paramecium but not in Chlorella?

Chloroplast

Contractile vacuole

Rough endoplasmic reticulum

Mitochondrion

Exam points

Describe multinucleate fungal hyphae and striated muscle fibres as atypical cells with multiple nuclei.
State that mature red blood cells and phloem sieve tubes lack nuclei.
Explain how these examples show limits to simple cell theory.

[Maximum number: 1]

What is a reason that both phloem sieve tube elements and human red blood cells are considered atypical?

They have no cytoplasm

Their DNA is free in the cytoplasm

They do not have a nucleus

All membrane-bound organelles are missing

Exam points

Identify prokaryotic, plant and animal cells in light and electron micrographs using visible structures and tissue context.
Recognise the nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus, vacuoles and ribosomes in micrographs.
Use visible structures and scale as evidence when identifying a cell or organelle in a micrograph.

[Maximum number: 1]

In the electron micrograph of a rat liver cell below, what are the structures labelled X and Y ?

rough endoplasmic reticulum

mitochondrion

smooth endoplasmic reticulum

nucleus

Golgi apparatus

vesicle

chromosome

vacuole

Exam points

Draw and label plant-cell organelles with correctly represented membrane details
Draw and label mitochondrial membranes, internal spaces and cristae accurately

[Maximum number: 4]

Draw a labelled diagram of a eukaryotic plant cell as seen in an electron micrograph.

Exam points

Explain how larger prokaryotic cells could engulf smaller prokaryotes that became mitochondria or chloroplasts.
Use binary fission, circular naked DNA, 70S ribosomes, double membranes and similar size as evidence for endosymbiosis.
Relate chloroplast DNA to cyanobacteria and mitochondrial DNA to alphaproteobacteria, including Rickettsiales.

[Maximum number: 1]

Leaf cells in spinach (Spinacia oleracea) have ribosomes in their cytoplasm with a relative molecular mass of 3847000 and smaller ribosomes inside their chloroplasts with a relative molecular mass of 2448000 . What is an explanation for spinach leaf cells having ribosomes of two different sizes?

The chloroplasts of plant cells evolved from a photosynthetic prokaryote.

Proteins inside chloroplasts are all smaller than proteins in the cytoplasm.

Ribosomes in the cytoplasm are attached to endoplasmic reticulum, whereas ribosomes in chloroplasts are free.

Ribosomes in the cytoplasm synthesize proteins, whereas ribosomes in chloroplasts absorb light.

Exam points

Explain that cells in a multicellular organism share the same genome but express different genes.
Relate different gene expression to proteome differences, cell specialization and the formation of specialized cells, tissues and organs.

[Maximum number: 1]

Which method provides biochemical evidence that cells have begun to differentiate?

Observation with a light microscope

Observation with an electron microscope

Examination of the DNA sequence

Analysis of the proteins

No public sample questions are available for this syllabus point yet.

Exam analysis

Most tested objectives

Common question formats

Recent exam appearances

Covered syllabus points

Question 1

Question 1

Question (a)

Question (b)

Question 1

Question 1

Question 1

Question 1

Question 1

Question 1

Question 1

Question 1

Question 1

Question 1

Question 1