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2025 • Biology • CYTOLOGY & HISTOLOGY

22. (a) State five disadvantages of preparing and viewing cells under the electron microscope.

(b) Draw a fully labelled diagram of a generalized animal cell as seen under the electron microscope

(c) Give five differences between this cell and a chlorenchyma cell.

(d) Why are electron microscopes not found in labouratories in Cameroon schools?

(5, 8,5,2 mks)

2025 • Biology • CYTOLOGY & HISTOLOGY

(a) On the basis of structure only, differentiate between a bacterial cell and a chlorenchyma cell as revealed by the electron microscope.

(b) How is the light microscope different from an electron microscope?

(c) Describe the structure of a compact bone in relation to its function as revealed by the light microscope. (5, 5,10 marks)

(a) Differences between a bacterial cell and achlorenchyma cell

Bacterial cell	Chlorenchyma cell
Cell wall made of murein	Cell wall made of cellulose
Has few nonmembrane bound organelles	Has many membrane bound organelles
Chlorophyll found in the photosynthetic membranes	Chlorophyll found in the chloroplast
Has flagella for movement	Absent
Has 70S ribosomes	Has 80S ribosomes
Energy produced in mesosomes	Energy produced in mitochondrion
Lacks pyrenoids	Has granules and pyrenoids for starch storage
Plasmids present	No plasmid
Small vacuoles lacking cell sap	Has large central vacuoles containing cell sap. *

(b) Differences between light and electron microscopes

Light microscope	Electron microscope
Uses light beams	Uses electron beams
Used to observe life and dead specimens	Specimen observed when dead
Can use sunlight	Uses electricity
Have low resolution and magnification powers.	High resolution and magnification powers.
Cheap and easily handled.	Expensive and bulky
Uses convex lènses	Uses electromagnets
Produces coloured images seen in 3 planes	Produce black and white images seen in one plane
Specimen viewed normally without special conditions.	Specimen viewed through a vacuum.
Easily manipulated with no expert training	Difficult to manipulate and requires expert training
Specimen supported on glass slides	Specimen supported on copper grid.

-The compact bone is made up of a hard rigid tissue composed of calcium salts and hydroxyapatite forming the lamellae. This gives hardness to bone.

-Living cells called osteoblasts are present in the lacunae which secret the substances to form the lamellae.

-Organic fibres, mainly collagen are present, making compact bone to resist tension and stress.

-Canaliculli connects bone lacunae, providing osteoblasts with nutrients and draining away wastes.

-The lamellae have hollow canals called Haversian canal which carries blood vessels and nerves.

-Bone is surrounded by fibrous membranes called periosteum which provide attachment sites for ligaments.

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Animal cell	Chlorenchyma
No cell wall	Cell wall made of cellulose
No chloroplasts and chlorophyll	Has chlorophyll found in the chloroplast
There is microvilli and centrioles present	Absent
Tacks pyrenoids	Has granules and pyrenoids for starch Storage
Small peripheral vacuoles	Large central vacuoles

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