BIOLOGY
FORM:ONE
MARKING SCHEME
TERM 3 2024
1. a) i) Define the term cell 1mark
The basic unit of organization of an organism i.e. the basic functional and structural unit of an
organism.
ii) What is cell biology? 1mark
study of structure and functioning of a cell
b) i) What is a microscope? 1mark
An instrument used to magnify objects and make them appear bigger.
ii) Name the types of microscope 2marks
light microscope
Electron microscope
iii) State the purpose of using a light microscope 2marks
magnifies and reveals the structure details of tiny objects such as the cell, that cannot be seen by the
human eye directly (magnification and resolution)
iv) Give the formula used to calculate magnification in a light microscope
1 mark
Eyepiece lens magnification x objective lens magnification
2. Give the reasons for each of the following steps when preparing a cross-section of a stem
or leaf for examination under the microscope
4marks
cutting very thin sections
Thin sections allow light to pass through making it easy to observe the tissue
Using a sharp razor blade during the cutting
Sharp blade does not damage, deform, destroy or distort the surface of cell or tissue
makes thin sections
Placing sections in water
maintains turgidity hence maintain shape of cell
prevents drying of the section
Staining the sections with iodine before observing
1
To make cell structures (chloroplasts, starch containing structures, granules or plastids) distinct.
3. List three parts of a cell that can be seen under a light microscope
3 marks
cell membrane
cytoplasm
cell wall
vacuole nucleus
4. Name two structures which are present in plant cells but absent in
animal cells 2marks
Chloroplast
Cell wall
5. A form one student observing Onion epidermal cells under the low power objective Counted 5
cells on a field of view measuring 5mm.
a) Estimate the size of one cell. 3 marks
formula 1mrk
equating values 1mrk
correct answer 1mrk
5x1000/5
=1000micrometers
b) If the eye piece magnification used was × 10 and that of the objective lens was × 10. What was the
magnification of the microscope? Show your working.
2 marks
10 x10 = X100
6. Name the tissue that carries out the following function in mammals.
a) Transports oxygen throughout the body. (1 mark)
blood
b) Supports the animal's body off the ground. (l mark)
skeletal
c) Transmits impulses from one part of the body to another. (1 mark)
nervous
7. State three differences between an electron microscope and a light microscope. (3 marks)
ELECTRON MICROSCOPE LIGHT MICROSCOPE
High resolving power Low resolving power
Uses beam of electrons to illuminate the specimen Use light to illuminate the specimen
Higher magnification Lower magnification
Uses electromagnetic power Uses glass lens
8. Give the function(s) of the following organelles: - 2marks
i) Vacuole
Stores various substances including wastes products;
Contributes to the osmotic properties of the cell;
ii) Cell membrane
Controls the exchange of materials between a cell and its environment;
Forms outer boundary in an animal cell;
2
9. Identify the organelle shown below giving its function: - 2marks
Organelle Mitochondrion;
Function site for respiration
10. The figure below represents a certain cell organelle: -
a) Identify the cell organelle: Nucleus. 1mark
b) What is the function of the part labelled A 1mark
- Formation of RNA / ribonucleic acid;
- Formation of ribosomes;
11. Distinguish between the following terms: -
a) Magnification and resolution of a microscope 2 marks
Magnification – Ability of a microscope to enlarge tiny objects
Resolution – Ability of a microscope to separate between two tiny structures under magnification to appear
distinct
b) Mounting and staining of a specimen 2 marks mounting.
Putting the specimen on to the slide
staining. Adding stains onto the specimen to make different parts of cell more distinct
12. The diagram below represents two different types of cells. Identify each cell and state its functions.
6 marks
CELL IDENTITY FUNCTION
A guard cell site for photosynthesis
3
B sperm cell fuses with ovum for reproduction
C white blood cell fight against pathogens
13. The diagram below shows some components of a light microscope.
a) Name each parts labelled A and B 2 marks
A. Eye piece lens
Coarse adjustment knob
b) state the functions of each of the parts labelled E and F 2 marks
E. concentrates and directs light onto the field of view
F. Magnifies the specimen.
c) Give a reason for each of the following precautions when using a light microscope.
i) The microscope must be carried with both hands 1 mark
To prevent it from falling off.
ii) The lenses and mirrors must never be touched with bare fingers 1 mark
To prevent dirtying the lenses which will lead to blurred images during viewing.
