GCSE Biology Grade 9 Revision Questions & Answers
Topic 1: Cell Biology
Question 1
Explain the differences between prokaryotic and eukaryotic cells, giving two examples of each
type of organism.
Answer:
Prokaryotic cells: No membrane-bound nucleus, genetic material freely distributed in
cytoplasm, no membrane-bound organelles. Examples: bacteria (E. coli), blue-green
algae (cyanobacteria)
Eukaryotic cells: Membrane-bound nucleus containing genetic material, membrane-
bound organelles present (mitochondria, chloroplasts, etc.). Examples: plant cells,
animal cells, fungi, protists
Question 2
Describe the process of mitosis and explain its importance in multicellular organisms.
Answer: Mitosis is cell division, producing two genetically identical diploid cells. Process:
prophase (chromosomes condense), metaphase (chromosomes align at the cell equator),
anaphase (sister chromatids separate), telophase (nuclear membranes reform), cytokinesis
(cytoplasm divides). Importance: growth, repair of damaged tissues, asexual reproduction, and
maintaining chromosome number.
Question 3
Calculate the magnification of a cell that appears 50mm long under a microscope when its
actual length is 0.05mm.
Answer: Magnification = Image size ÷ Actual size Magnification = 50mm ÷ 0.05mm = 1000×
Topic 2: Organisation
Question 4
Describe the structure and function of the heart, explaining how it pumps blood around the
body.
Answer: The heart has four chambers: two atria (receive blood) and two ventricles (pump
blood). Right side pumps deoxygenated blood to the lungs, the left side pumps oxygenated
, blood to the body. Cardiac cycle: atria contract (atrial systole), forcing blood into ventricles, then
ventricles contract (ventricular systole), pumping blood out. Valves prevent backflow. The heart
muscle is myogenic (self-contracting).
Question 5
Explain how the structure of the small intestine is adapted for absorption.
Answer:
Villi: Finger-like projections increase surface area
Microvilli: Further increase surface area on epithelial cells
Thin walls: Single cell thickness for short diffusion distance
Rich blood supply: Maintains concentration gradient
Lacteals: Lymphatic vessels for fat absorption
Longer length: More time for absorption
Question 6
Describe the process of transpiration and explain three factors that affect its rate.
Answer: Transpiration is water loss from plant leaves through stomata as water vapor. Process:
water evaporates from mesophyll cells, creates water vapor in air spaces, and diffuses out
through stomata. Factors affecting the rate:
1. Temperature: Higher temperature increases the evaporation rate
2. Humidity: Lower humidity increases the concentration gradient
3. Wind speed: Removes water vapor, maintaining the concentration gradient
Topic 3: Infection and Response
Question 7
Compare and contrast bacterial and viral diseases, giving examples of each.
Answer: Bacterial diseases: Caused by bacteria, can be treated with antibiotics, bacteria
reproduce by binary fission. Examples: tuberculosis, food poisoning (Salmonella) Viral diseases:
Caused by viruses, cannot be treated with antibiotics (treated with antivirals), viruses reproduce
Topic 1: Cell Biology
Question 1
Explain the differences between prokaryotic and eukaryotic cells, giving two examples of each
type of organism.
Answer:
Prokaryotic cells: No membrane-bound nucleus, genetic material freely distributed in
cytoplasm, no membrane-bound organelles. Examples: bacteria (E. coli), blue-green
algae (cyanobacteria)
Eukaryotic cells: Membrane-bound nucleus containing genetic material, membrane-
bound organelles present (mitochondria, chloroplasts, etc.). Examples: plant cells,
animal cells, fungi, protists
Question 2
Describe the process of mitosis and explain its importance in multicellular organisms.
Answer: Mitosis is cell division, producing two genetically identical diploid cells. Process:
prophase (chromosomes condense), metaphase (chromosomes align at the cell equator),
anaphase (sister chromatids separate), telophase (nuclear membranes reform), cytokinesis
(cytoplasm divides). Importance: growth, repair of damaged tissues, asexual reproduction, and
maintaining chromosome number.
Question 3
Calculate the magnification of a cell that appears 50mm long under a microscope when its
actual length is 0.05mm.
Answer: Magnification = Image size ÷ Actual size Magnification = 50mm ÷ 0.05mm = 1000×
Topic 2: Organisation
Question 4
Describe the structure and function of the heart, explaining how it pumps blood around the
body.
Answer: The heart has four chambers: two atria (receive blood) and two ventricles (pump
blood). Right side pumps deoxygenated blood to the lungs, the left side pumps oxygenated
, blood to the body. Cardiac cycle: atria contract (atrial systole), forcing blood into ventricles, then
ventricles contract (ventricular systole), pumping blood out. Valves prevent backflow. The heart
muscle is myogenic (self-contracting).
Question 5
Explain how the structure of the small intestine is adapted for absorption.
Answer:
Villi: Finger-like projections increase surface area
Microvilli: Further increase surface area on epithelial cells
Thin walls: Single cell thickness for short diffusion distance
Rich blood supply: Maintains concentration gradient
Lacteals: Lymphatic vessels for fat absorption
Longer length: More time for absorption
Question 6
Describe the process of transpiration and explain three factors that affect its rate.
Answer: Transpiration is water loss from plant leaves through stomata as water vapor. Process:
water evaporates from mesophyll cells, creates water vapor in air spaces, and diffuses out
through stomata. Factors affecting the rate:
1. Temperature: Higher temperature increases the evaporation rate
2. Humidity: Lower humidity increases the concentration gradient
3. Wind speed: Removes water vapor, maintaining the concentration gradient
Topic 3: Infection and Response
Question 7
Compare and contrast bacterial and viral diseases, giving examples of each.
Answer: Bacterial diseases: Caused by bacteria, can be treated with antibiotics, bacteria
reproduce by binary fission. Examples: tuberculosis, food poisoning (Salmonella) Viral diseases:
Caused by viruses, cannot be treated with antibiotics (treated with antivirals), viruses reproduce
