GCE Biology CIE 5090
1.1 Cell structure and function
CONTENTS
1 Examine under the microscope, animal cells and plant cells from any
suitable locally available material, using an appropriate temporary staining
technique, such as methylene blue or iodine solution
2 Draw diagrams to represent observations of the animal and plant cells
examined above
3 Identify on diagrams, photomicrographs or electron micrographs, the
ribosomes, mitochondria, nucleus, cytoplasm and cell membrane in an animal
cell
4 Identify on diagrams, photomicrographs or electron micrographs, the
ribosomes, mitochondria, chloroplasts, nucleus, sap vacuole, cytoplasm, cell
membrane and cellulose cell wall in a plant cell
5 Describe the structure of a bacterial cell, limited to: ribosomes, circular
deoxyribonucleic acid (DNA) and plasmids, cytoplasm, cell membrane and cell
wall
6 Describe the functions of the above structures in animal, plant and bacterial
cells
1.1 Cell structure and function
1.1 Cell Structure and Function
Cells are the fundamental units of life. Their internal structures, or organelles,
are each responsible for specific functions.
Key Eukaryotic Cell Structures & Functions:
Structure Found Function
In
Cell Animal A partially permeable barrier that controls which
Membrane & Plant substances enter and leave the cell.
Cytoplasm Animal A jelly-like substance filling the cell where most
& Plant metabolic reactions (chemical reactions of life) take
place.
Nucleus Animal Contains the chromosomes (made of DNA) which
& Plant carry genetic information. It controls all the activities
of the cell.
Mitochondri Animal The site of aerobic respiration, a series of chemical
a & Plant reactions that release energy for the cell to use.
Ribosomes Animal Small structures that are the site of protein
& Plant synthesis.
Cell Wall Plant A rigid, fully permeable outer layer made
only of cellulose. It provides structural support, maintains
the cell's shape, and prevents it from bursting.
Sap Plant A large, central, membrane-bound sac
Vacuole only containing cell sap. It helps maintain turgor pressure
against the cell wall, keeping the cell firm.
Chloroplast Plant Contains the green pigment chlorophyll, which
s only absorbs light energy. It is the site of photosynthesis.
Bacterial Cell Structure:
Bacteria are prokaryotes (lacking a true nucleus).
o Cell Wall: Provides support but is made of
peptidoglycan, not cellulose.
o Cell Membrane & Cytoplasm: Basic functions are the same as in
eukaryotes.
o Circular DNA: A large loop of DNA containing the main genetic
information, found free in the cytoplasm.
o Plasmids: Small, circular rings of DNA carrying extra genes.
o Ribosomes: Present for protein synthesis.
Paper 2 Tip: For a 3-mark question asking for differences between plant and animal
cells, the three most reliable points are:
1. Plant cells have a cellulose cell wall; animal cells do not.
2. Plant cells have a large central sap vacuole; animal cells have small,
temporary vacuoles, if any.
3. Plant cells (in photosynthetic parts) contain chloroplasts; animal cells do not.
Past Paper Practice (Topic 1.1)
Question 1 (MCQ): [June 2021, Paper 12, Q1]
Which features are present in a root hair cell?
cell chloroplas
wall ts
A ✓ ✓
B ✓ ✗
C ✗ ✓
D ✗ ✗
Solution: B
o Explanation: A root hair cell is a plant cell, so it has a cell wall.
However, it is located underground and does not receive light, so it
does not perform photosynthesis and therefore does not have
chloroplasts.
Question 2 (MCQ): [Based on 5090 Syllabus]
Which structure is found in a plant cell but is absent from a bacterial cell?
A. Cell wall
B. Cytoplasm
C. Nucleus
D. Ribosomes
Solution: C
o Explanation: Plant cells are eukaryotic and have a true nucleus
that contains their chromosomes. Bacterial cells are prokaryotic and
have their genetic material (a circular DNA loop) free in the
cytoplasm, with no nucleus. Both have a cell wall (though made of
different materials), cytoplasm, and ribosomes.
Question 3 (Paper 2): [June 2021, Paper 22, Q1b & c]
(b) A cell in a salivary gland contains a large number of mitochondria. Suggest
and explain the reason for this. [2]
(c) This cell also contains many ribosomes. State the function of ribosomes. [1]
Solution:
(b) The cell needs to produce saliva / enzymes, which requires a large
amount of energy. Mitochondria are the site of aerobic respiration, which
releases this energy.
(c) Ribosomes are the site of protein synthesis.
Examiner's View (P2):
(b) This is a link-and-explain question. The link is "salivary gland produces
enzymes" and the explanation is that this process "requires energy from
respiration in mitochondria".
(c) A direct recall of the function of ribosomes.
1.2 Specialised cells, tissues and organs
CONTENTS
1 Understand that cells can become specialised and that their structures are
related to their specific functions, as illustrated by examples covered in the
syllabus
2 Understand the terms cell, tissue, organ, organ system and organism as
illustrated by examples covered in the syllabus
3 State and use the formula magnification = image size/actual size
1.2 Specialised cells, tissues and organs
1.2 Specialised Cells, Tissues, and Organs
Cell Specialisation: The process by which cells develop specific
structures to carry out a particular function effectively. The
structure is always related to the function (e.g., root hair cells have
a long extension to increase surface area for absorption).
Levels of Organisation:
1. Cell: The basic unit of life (e.g., a muscle cell).
2. Tissue: A group of similar cells working together to perform a
specific function (e.g., muscle tissue, which contracts).
3. Organ: A structure made from different types of
tissues working together to perform complex functions (e.g.,
the heart).
4. Organ System: A group of organs that work together to carry
out a major bodily function (e.g., the digestive system).
5. Organism: A complete living being.
Magnification Calculation:
o Formula: Magnification = Image Size / Actual Size
o Rule: Both Image Size and Actual Size must be in the same
units.
o Conversion: 1 mm = 1000 micrometres (µm).
Paper 4 Tip: Magnification calculations are very common. Always
write the formula, show your unit conversion clearly (e.g., "0.05 mm =
50 µm"), show your substitution, and then give the final answer. Marks
are awarded for the working, not just the answer.
Past Paper Practice (Topic 1.2)
Question 1 (MCQ): [Nov 2020, Paper 12, Q2]
What is the correct order of increasing size in the organisation of a
mammal?
A. cell → organ → organ system → tissue
B. cell → tissue → organ → organ system
C. organ → organ system → tissue → cell
D. tissue → cell → organ system → organ
Solution: B
o Explanation: This tests the hierarchy of organisation. The
correct order is from the smallest unit (cell) to progressively
larger and more complex structures (tissue, organ, organ
system).
Question 2 (Paper 2): [Nov 2021, Paper 22, Q1a]
The actual length of a mitochondrion is 2.5 µm. A student draws a
diagram of the mitochondrion that is 5.0 cm long.
Calculate the magnification of the student's drawing. Show your working.
[3]
Solution:
1. State the formula: Magnification = Image Size / Actual Size.
2. Convert units to be the same (e.g., to µm):
Image Size = 5.0 cm = 50 mm = 50,000 µm.
Actual Size = 2.5 µm.
3. Calculate: Magnification = 50,000 µm / 2.5 µm = 20,000.
The magnification is ×20,000.
Examiner's View (P2/P4): This is a standard magnification calculation
worth 3 marks.
4. Mark 1 is for the correct formula.
5. Mark 2 is for correctly converting the units so they are
consistent.
6. Mark 3 is for the final correct answer. Forgetting to convert
units is the most common error.
Question 3 (Paper 2): [Based on 5090 syllabus]
Explain how the structure of a red blood cell is related to its function of
transporting oxygen. [3]
Solution:
1. It has a biconcave shape which increases the surface area to
volume ratio for faster diffusion of oxygen.
2. It contains haemoglobin, the protein that binds with oxygen.
3. It has no nucleus, which maximises the space available for
haemoglobin.
Examiner's View (P2): This is a classic "structure relates to function"
question. Three distinct points are needed for 3 marks. Simply stating the
features is not enough; you must link each feature to how it helps with
oxygen transport.
