Transport Biology Practical Questions And Answers
BIOLOGY PRACTICAL O’LEVEL Transport | Transport Biology Practical | Transport Biology Practical | Transport Questions With Answers | Transport
Until 2008, NECTA biology practicals contained three questions. Question 1 was required, and was a food test. Students then chose to answer either question 2 or question 3.
One of these questions was usually classification. The format changed in 2008. Now, the practical contains two questions, and both are required.
Food test and classification remain the most common questions, but sometimes only one of these two topics is on a given exam.
The second question may cover one of a variety of topics, including respiration, transport, coordination, photosynthesis, and movement.
Each question is worth 25 marks.
<> Food test: students must test a solution for starch, sugars, fats, and protein
<> Classification: students must name and classify specimens, then answer questions about their characteristics
<> Respiration: students use lime water to test air from the lungs for carbon dioxide
<> Transport: students investigate osmosis by placing leaf petioles or pieces of raw potato in solutions of different solute concentrations
<> Photosynthesis: students test a variegated leaf for starch to prove that chlorophyll is necessary for photosynthesis
<>Coordination: students look at themselves in the mirror and answer questions about the sense organs they see
Note: These are the most common practicals, but they are not necessarily the only practicals that can occur on the national exam. Biology practicals frequently change, and it is possible that a given exam will contain a new kind of question. Look through past NECTA practicals yourself to get an idea of the kind of questions that can occur
The purpose of this practical is to investigate osmosis by observing the changes in a leaf petiole placed in a hypotonic solution (water) and a hypertonic solution (water containing salt or sugar).
This section contains the following:
- Sample practical with solutions
The petiole is the stalk which attaches a leaf to a branch. The papaya leaf petioles in this practical should be soft petioles from young leaves, not stiff petioles from older leaves.
Cut the petioles into pieces, and give each student two pieces of about 6 cm in length. Cylinders cut from a raw potato may be used instead of petioles.
The hypertonic solution may be made with by mixing either salt or sugar with water. The hypotonic solution is tap water.
2. Sample practical with solutions
A form four student was interested to investigate osmosis phenomenon and decided to set the experiment as shown in figure 7 below
Study this figure and answer the questions that follow.
- Which solution has a higher concentration of free water molecules?
- Which solution has high solute concentration
- In which direction will osmosis occur?
- What does the semi – permeable membrane corresponds to within an animal cell?
- What is osmosis?
- Name five (5) processed in living things that depend on osmosis
Solution which as a higher concentration of free water molecules is solution B.
Solution which has high solute concentration is solution A
Osmosis will occur in this way; water molecules will move from solution B through semi permeable membrane towards solution A
The semi-permeable membrane correspond to plasma membrane within an animal cell
Osmosis refers to the movement of solvent (water) from the region of its low concentration to the region of its high concentration through semi – permeable membrane.
Osmosis is the movement of a solvent across semi- permeable membrane toward a higher concentration of solute.
Five (5) process in living things that depends on osmosis are:-
- Active transport
- Passive transport
- Osmotic pressure
- Osmotic gradient
1. You are provided with a beaker, tea bag and hot water. Carry out the following experiment. Pour about 100cm3 off hot water into the beaker.
2. Put the tea bag into the beaker containing hot water. Observe carefully the experiment for a few minutes.
a.(i) What happened to the tea bag when it was put in hot water?
(ii) Explain why the changes you observed occurred?
b.(i) What do you think was the aim of the experiment?
(ii) Draw a conclusion from the experiment
c. (i) Name the physiological process investigated in this experiment
Define the process named in (c) (i) above
(i) When tea bag was put in hot water, water rushed (entered) the tea bag through Osmosis process, after attaining equilibrium water soluble ingredients (chemicals) from the tea bad started to go out (diffuses) slowly into the beaker containing hot water and changes the color of hot water slowly from clear (colorless) to brown color through diffusion process.
(ii) The above change a (i) occurred due to occurrence of both diffusion and osmosis. Osmosis process is when hot water molecules entered (moved) into a tea bag through selectively permeable membrane (tea bag material), and the diffusion process is when aqueous solutes (soluble chemical ingredients) moved out (diffuses) from the tea bag into the beaker containing hot water and finally becomes brown in color.
(i) Aim of the experiment was demonstrate both Osmosis and diffusion processes.
(ii) In conclusion, tea bag acted like a cell membrane because it controlled what went in and out just like a cell osmosis and diffusion occurred when tea color left the bag and water entered the bag.
It also acted like a cell membrane by keeping some things in likes the tea leaves.
(i) The physiological process investigated in this was either Diffusion or Osmosis.
Diffusion is the movement of substance from area of higher concentration to area of lower concentration.
Osmosis is the movement of water molecules through or across semi permeable membrane from where they are in high concentration to where they are in low concentration in order to reach equilibrium.
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Importance of diffusion in nature
Diffusion is a process in which material spreads throughout a liquid or gas, it is important to living things as it explains how useful materials and waste products can move into and out of cells. Digested food molecules (amino acids, glucose) move down a concentration gradient from the intestine to the blood.
Diffusion allows the exchange of substances; the entry of oxygen, proteins etc. into the cell and the removal of waste substances.
Importance of Osmosis in nature
Osmosis is a natural physical process in which water molecules moves across a selectively permeable membrane from area of high concentration to an area of low concentration so as to maintain equilibrium.
Plants need osmosis because, through osmosis they their water. So plant cells maintain their water content despite the loss of water to the air that is constantly occurring.
Osmosis provides turgidity to the softer tissues and is therefore, essential for their mechanical support. It also controls the absorption of water by root hairs from the soil etc.
In an experiment to find the composition of blood, 5cm3 of fresh blood from a rabbit was centrifuged and the result was as shown below
Most plentiful in B
Least plentiful in B
c) Arrange in increasing order the substances present in B
You are provided with solid sample C and distilled water. Fill the beaker with distilled water using a spatula slowly put a small portion of the solid sample C in a beaker of water and observe the changes in the mixture for 5mn then answer the question that follows.
Is the movement of water molecules from high concentration of water molecules to low concentration of water molecules.
You have been provided with specimen X and two solutions SI and S2. Using razor blade or scalpel, cut 6cm long petiole from Specimen X. Use this same piece of petiole in all 3 stages of the experiment described below.
Using razor blade or scalpel, spirit the piece of petiole from Specimen X longitudinally up to its length so as to produce 4 strips on one end of the specimen, while the other end remains intact as shown in the diagram.
Dip the piece of petiole in solution S2 for about 10 minutes. Remove it from the solution, observe and touch it gently to feel it’s hardness or softness.
Dip the petiole in S3 for about 10 minutes. Remove it from the solution, observe and touch it gently to feel its hardness or softness.
Record your observations and explanations for Stage II and stage III of the experiment as shown in the table.
Stage of Experiment
- What was the aim of the experiment
- Give brief comments on the concentrated of solution S2 and S3
- Why is the biological process demonstrated by the above experiment important to plant?
- Define the process demonstrated by the above experiment
- Explain what happen to the cells of the petioles in Stage II and Stage III. Illustrate your answer.
Stage of Experiment
The piece of petiole becomes
It shrinks due to loss of water
The piece of petiole becomes hard and strong
It absorbs water and become turgid
To demonstrate the process of Osmosis
– The solution of S2 is hypertonic (too concentrated) compound to cell sap of the leaf petiole that is why the petioles lose water and become plasmelysed.
– The solution S3 is hypotonic (less concentrated) compared to the cell sap of the leaf petiole that is why the petiole absorbs water and become turgid.
i. It is important as it enables plant roots to absorb water and dissolved mineral salt from the soil also give strength to the offers support plant
ii. Allows opening of stomata hence facilitate gaseous exchange.
Osmosis is the movement of water Transpiration molecules from lowly concentrated solution to highly concentrated solution through semi- permeable membrane.
In stage IT the petiole loses water, shrinks and become plasmolysed
In stage III the petiole gain water and becomes turgid