BIOLOGY
INSTRUCTIONS.
- Answer all the questions in the spaces provided.
Questions
- State the function of the following organelles. (2mks)
- Lysosomes
- Ribosomes
- A student observed a row of 16 epidermal cells in a microscopic field that was 8mm in diameter. Calculate the average length of one cell in micrometres. Show your working. (3mks)
- A student drew a 6cm diagram of a plant flower if the actual length of the flower was 12cm. calculate the magnification of the drawing made by the student. Show your working. (3mks)
- State three factors that affect the rate of diffusion. (3mks)
- An experiment was set-up in a laboratory as shown below.
- What will happen to visking tubing in M and N after two hours. (2mks)
- Explain the observations made in M. (2mks)
- What does visking tubing represent in a living organism? (1mk)
- Distinguish between autotrophism and heterotrophism modes of nutrition. (2mks)
- State three properties of monosaccharides. (3mks)
- The equation below shows formation of a disaccharide.
process p
Glucose + Glucose → Q + water- Name process P. (1mk)
- Product Q. (1mk)
- Other than product Q named above name other two examples of disaccharides. (2mks)
- List four factors which affect enzyme controlled reaction. (4mks)
- Name two nutrients that are absorbed without being digested by the enzymes in humans. (2mks)
- List three types of salivary glands. (3mks)
- Give two roles of saliva in the process of digestion. (2mks)
- Differentiate between homodonts and heterodonts. (2mks)
- The diagram below represents the lower jaw of a mammal.
- Name the mode of nutrition of the animal whose jaw is shown above. (1mk)
- Mode of feeding. (1mk)
- Give a reason for your answer in (b) above. (1mk)
- Diet of the animal. (1mk)
- Name the toothless gap labeled K. (1mk)
- Name the substance that is responsible for hardening of teeth. (1mk)
- State the roles of the structures found within a tooth:
- Blood vessels. (1mk)
- Nerves. (1mk)
- List two major types of dental diseases. (2mks)
- Give two roles played by bile salts in the process of digestion. (2mks)
- Explain five ways in which the illume is adapted to its functions. (5mks)
- The following is a dental formula of a certain mammal.
I0/3 C0/1 Pm3/3 m3/3- Calculate the total number of teeth of the mammal. (2mks)
- Give the likely mode of feeding. (1mk)
- Give a reason for your answer in (ii) above. (1mk)
-
- Name the disease in humans caused by deficiency the following: (5mks)
- Vitamin A
- Vitamin D
- Vitamin C
- Iodine
- Iron
- State one function of water in the diet. (1mk)
- State five factors that determine energy requirements in human beings. (5mks)
- Name the disease in humans caused by deficiency the following: (5mks)
Marking Scheme
- State the function of the following organelles. (2mks)
- Lysosomes
- Contain lytic enzymes that destroy worn out cells.
- Ribosomes
- They are sites for protein synthesis
- They are sites for protein synthesis
- Lysosomes
- A student observed a row of 16 epidermal cells in a microscopic field that was 8mm in diameter. Calculate the average length of one cell in micrometres. Show your working. (3mks)
- Size of one cell = diameter of field of view
Number of cells in field of view.
8mm x 1000μm
1mm
= 8000um
16cells
=500μm
- Size of one cell = diameter of field of view
- A student drew a 6cm diagram of a plant flower if the actual length of the flower was 12cm. calculate the magnification of the drawing made by the student. Show your working. (3mks)
- Magnification of a handlens = Drawing length
Actual length of the object
6cm = x0.5
12cm
- Magnification of a handlens = Drawing length
- State three factors that affect the rate of diffusion. (3mks)
- Diffusion gradient
- Thickness of tissues
- Size of molecules
- Temperature
- Type of medium
- Surface area to volume ratio
- An experiment was set-up in a laboratory as shown below.
- What will happen to visking tubing in M and N after two hours. (2mks)
- M – will swell / increase in size
- N – Will shrink / decrease
- Explain the observations made in M. (2mks)
- Sodium chloride solution is a hypertonic solution while distilled water is a hypotonic solution therefore distilled water molecules will move from the beaker to the visking tubing by osmosis making it to swell.
- Sodium chloride solution is a hypertonic solution while distilled water is a hypotonic solution therefore distilled water molecules will move from the beaker to the visking tubing by osmosis making it to swell.
- What does visking tubing represent in a living organism? (1mk)
- Cell membrane/ plasma membrane/plasmalema.
- Cell membrane/ plasma membrane/plasmalema.
- What will happen to visking tubing in M and N after two hours. (2mks)
- Distinguish between autotrophism and heterotrophism modes of nutrition. (2mks)
- Autotrophism is a mode of nutrition in which some plants manufacture their own complex food substances from simpler substances such as carbon (IV) oxide and water while heterotrophism is a mode of nutrition that involves taking complex ready made food materials from plants and other animals.
- Autotrophism is a mode of nutrition in which some plants manufacture their own complex food substances from simpler substances such as carbon (IV) oxide and water while heterotrophism is a mode of nutrition that involves taking complex ready made food materials from plants and other animals.
- State three properties of monosaccharides. (3mks)
- They are soluble in water
- They form sweet tasting solution
- They are reducing sugars
- They are crystalisable.
- The equation below shows formation of a disaccharide.
Glucose + Glucose process p Q + water- Name process P. (1mk)
- Condensation
- Condensation
- Product Q. (1mk)
- Maltose
- Maltose
- Other than product Q named above name other two examples of disaccharides. (2mks)
- Sucrose
- Lactose
- Name process P. (1mk)
- List four factors which affect enzyme controlled reaction. (4mks)
- Temperature
- pH
- Specificity
- Enzyme co-factors and co-enzyme
- Enzyme inhibitors
- Substrate concentration and enzyme concentration.
- Name two nutrients that are absorbed without being digested by the enzymes in humans. (2mks)
- Water
- Vitamins
- Mineral ions/salts
- List three types of salivary glands. (3mks)
- Sublingual
- Sub-mandibular
- Parotial sub-maxillary
- Give two roles of saliva in the process of digestion. (2mks)
- Lubricates food
- Moistens food
- Softens food
- Dissolves food
- Contains salivary amylase hence digests starch to maltose
- Provides an alkaline medium for action of salivary amylase.
- Differentiate between homodonts and heterodonts. (2mks)
- Homodonts: are animals which have the same types, size and shape of teeth while heterodonts are animals with different types, size and shapes of teeth.
- Homodonts: are animals which have the same types, size and shape of teeth while heterodonts are animals with different types, size and shapes of teeth.
- The diagram below represents the lower jaw of a mammal.
- Name the mode of nutrition of the animal whose jaw is shown above. (1mk)
- Heterotrophism
- Mode of feeding. (1mk)
- Herbivorous
- Herbivorous
- Give a reason for your answer in (b) above. (1mk)
- Presence of a diastema
- Presence of a diastema
- Diet of the animal. (1mk)
- Vegetation/ grass/green leaves.
- Vegetation/ grass/green leaves.
- Name the toothless gap labeled K. (1mk)
- Diastema
- Diastema
- Name the substance that is responsible for hardening of teeth. (1mk)
- Calcium phosphate
- Calcium phosphate
- Name the mode of nutrition of the animal whose jaw is shown above. (1mk)
- State the roles of the structures found within a tooth:
- Blood vessels. (1mk)
- They supply nutrients to living tissues in the dentine.
Remove waste products from the dentine
- They supply nutrients to living tissues in the dentine.
- Nerves. (1mk)
- They detect heat, cold and pain in the tooth
- They detect heat, cold and pain in the tooth
- Blood vessels. (1mk)
- List two major types of dental diseases. (2mks)
- Dental carriers
- Periodontal disease
- Give two roles played by bile salts in the process of digestion. (2mks)
- They aid in the breakdown of fats into tiny fat droplets to increase their surface area for digestion (emulsification)
- They provide an alkaline medium which the enzymes work best.
- They neutralize the acidic chime from the stomach.
- Explain five ways in which the illume is adapted to its functions. (5mks)
- Long and narrow to increase surface area for digestion and bring digested food into close contact with walls of the ileum for easier absorption.
- Highly coiled to slow down movement of food thus allowing more time for digestion and absorption to take place.
- Large number of villi and micro-vill to increase surface area.
- Presence of thinner layer of cells to reduce diffusion distance of digested food.
- Presence of dense network of capillaries in the villi into which amino acids, sugar and vitamins are absorbed.
- Presence of lacteals in the villi for the absorption of fatty acids and glycerol.
- The following is a dental formula of a certain mammal.
- Calculate the total number of teeth of the mammal. (2mks)
0 + 0 + 3 + 3 x 2 = 12
3 + 1 + 3 + 3 x 2 = 20
32 teeth - Give the likely mode of feeding. (1mk)
- Herbivorous
- Herbivorous
- Give a reason for your answer in (ii) above. (1mk)
- It lacks incisors and canines in the upper jaw to create a horny pad.
- It lacks incisors and canines in the upper jaw to create a horny pad.
- Calculate the total number of teeth of the mammal. (2mks)
-
- Name the disease in humans caused by deficiency the following: (5mks)
- Vitamin A
- Night blindness
- Night blindness
- Vitamin D
- Rickets
- Rickets
- Vitamin C
- Scurvy
- Scurvy
- Iodine
- Goiter
- Goiter
- Iron
- Anemia
- Anemia
- Vitamin A
- State one function of water in the diet. (1mk)
- it is a solvent of soluble food substances cooling of the body.
- Provided the medium for transport of dissolved food substances.
- Facilitates hydrolysis of food substances.
- State five factors that determine energy requirements in human beings. (5mks)
- Basal metabolic rate
- Occupation/everyday activity
- Age
- Body size
- Sex
- Name the disease in humans caused by deficiency the following: (5mks)
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