Grade 11 Biology Animation

Biology lab safety rules

 Biology lab safety rules are guidelines designed to help keep you safe while doing experiment. Some equipment and chemicals in a biology laboratory can cause serious harm.

It is always wise to follow all lab safety rules.

 The following biology lab safety rules are a sample of the most basic rules that should be followed when in a biology lab.

1.Enter into the lab and locate safety materials 

2.Be Prepared (animate clean lab desk, with the protocol hanged above the desk) 3.Wear Proper Clothing 

4.Organize

5.Start your experiment Biology Lab Don'ts There are several things in a biology lab that you must always avoid—here are a few major laboratory don't

Do Not

• eat or drink in the lab

• taste any chemicals or substances you are working with

• use your mouth for pipetting substances

• handle broken glass with bare hands

• perform your own experiments unless given permission

• leave any heated materials unattended• place flammable substances near heat

Steps in scientific method

 This is a process by which biologists and all other scientists approach their work.

 The process follows a series of steps which starts from observation leading to a question

 The question rises from an environmentally observed problem. Such as a gas coming out of industrial area…. WHY?

 Then a person will do a background study by reviewing previous researches and unpublished evidences.

 From the observed phenomena and background study a hypothesis is formulated.

 Hypothesis is an educated guess about what a scientist thinks the explanation of an observation will be.

 But it has to be stated in such a way that it can be tested by experiment

 Thus, the proposed hypothesis will be tested by an experiment.

 From the experiment result will be obtained which will be analyzed to give a meaningful information that will lead to a conclusion

 The conclusion may or may not match with the hypothesis

 Finally, the whole process will be reported and published in a journal. 

Laboratory instruments

There are some commonly used lab tools that are used in a scientific study Among the most commonly used instruments the followings are the most basic ones.

 Microscope

Microscope is an instrument used to see objects that are to small to be seen by naked eye

 Dissecting instrument

DI includes scalpels, scissors, forceps, knives, saws and more, which are basic tools to open animal body for experimental purpose

 Petri dishes

Is a cylindrical glass or plastic lidded dish that biologists use to culture cells

 Pipettes

Is a laboratory tool commonly used in chemistry and biology lab to transfer measured volume of liquid

 Syringes

Is a tube with nuzzle and piston for sucking in and ejecting liquid into a thin stream

 Cylinders graduated cylinder is used to measure volume of liquid

 Balances Is a device to measure weighs mass 

Life cycle of HIV

• AIDS is a short designation for ‘acquired immunodeficiency syndrome’.
• It is a disease caused by HIV (Human immunodeficiency virus)HIV is categorized under a group of virus called retrovirus that shares similar life cycle 

•  The first stage is called the entry phase. In this phase the virus attaches to the cell membrane of the host call and inter into the cell(1)
• After the entry, the virus releases its genetic material(RNA) in the host cell and RNA will be converted into DNA by an enzyme called reverse transcriptase(2)
• Following, the newly formed DNA will enter into the host cell nucleus and integrate itself with the host cell DNA that instructs the cell to make more virus(3)
• Finally, the newly formed virus will be released from the cell and affect other cells(4) 

Hydrogen bonding in water

 Water is one of the most important inorganic molecule on earth and living system.

 Most of the important property of water comes from the unique structure it has as a result of hydrogen bonding.

 Hydrogen bonding is a special kind of non-covalent bond formed between a partially positive and negative charged atom

 As you know, water is made from two hydrogen atom and one oxygen atom joined by a covalent bond.

 When we consider the electronegative value of hydrogen and oxygen, oxygen has a higher electronegativity value as compared to hydrogen.

• As a result the shared electron between the two atoms will be attracted towards oxygen, resulting in a partial negative charge on oxygen and a partial positive charge on the hydrogen
• Due to the formation of the two partial charges a weak inter-molecular attraction will be formed which we call a hydrogen bonding.

Food Tests

There are different kinds of chemical tests used to identify the kind of nutrient present in a certain types of food. We will see the most common food tests as follow.

(I)Test for glucose (Benedict’s test)

 This is a chemical test used to identify the presence of glucose in a food.

 To do this test we need to have the following materials,

Procedure:

• Using a dropper, take a small quantity of Benedict’s reagent.

• Add the reagent to the test tube containing banana extract.

• Boil the sample over a burner for 2 minutes holding the test tube firmly with a test tube holder.

• Keep shaking the test tube as it is being heated.

• A brick red precipitate appears, indicating the presence of glucose in the banana extract.

Result:

• On boiling banana extract with the Benedict’s reagent, the cupric ion present in the Benedict’s reagent is reduced by the reducing agent, sugar, to form a brick red coloured precipitate of cuprous oxide. 

Test for Sucrose

 This is a chemical test used to identify the presence of glucose in a food.

 To do this test we need to have the following materials, 

• Using a dropper, take a small quantity of concentrated HCl.

• Add 2 to 3 drops of concentrated HCl to the test tube containing sugarcane extract.

• Boil the sample over a burner for 2 minutes, holding the test tube firmly with a test tube holder.

• This hydrolyses sucrose into glucose and fructose.

• Using a dropper, take a small quantity of NaOH solution.

• Add few drops of NaOH solution to the test tube to make the solution alkaline.

• Now we can perform Benedict’s test to this solution to test for the presence of glucose

• Using a dropper, take a small quantity of Benedict’s reagent.

• Add the reagent to the test tube containing the sample.

• Boil the sample over a burner for 2 minutes, holding the test tube firmly with a test tube holder.

Result:

• The color changes from blue to green and finally to orange or brick red, indicating the presence of glucose.

Iodine test for starch

 Iodine test is used to check whether starch is present in a certain food or not.

 To do this test we need to have the following materials, 

Procedures:

• Place a potato on a tile.

• Grind or chop the potato into small pieces, using a knife.

• Using a spatula transfer these pieces of potato into a beaker.

• Pour some distilled water into the beaker.

• Place the beaker containing the mixture over a hot plate.

• Heat the mixture for 5 minutes while continuously stirring it with a glass rod

.• Take another beaker and cover its mouth with a muslin cloth.

• Secure the muslin cloth around the mouth of the beaker by tying it with a thread.

• Filter the solution through this beaker.

• Now take a clean test tube and pour some of the filtrate into it.

• Take a few drops of iodine solution using a dropper.

• Add a couple of these drops into the test solution.

Result:

The test solution will turn into blue black.

This indicated Iodine reacts with starch and form Iodine-starch complex which has a blue-black color.

This confirms potato contains starch. 

Biuret test for proteins

 This is a chemical test used to check the presence of protein in a food.

 To do this test we need to have the following materials, 

• Using a dropper, take a small quantity of 40% NaOH solution.

• Add a few drops of NaOH solution to the test tube containing egg albumin.

• Using a dropper, take a small quantity of 1% CuSO4 solution.

• Add 2-3 drops of CuSO4 solution to the test tube containing egg albumin.

• Shake the solution to mix it well.

Result:

• A violet color appears in the test tube, which indicates the presence of proteins. 

Emulsion test for lipids

 This is a chemical test used to check the presence of protein in a food.

 To do this test we need to have the following materials, 

Procedure:

• Using a dropper, take a small quantity of ethanol.

• Add few drops of ethanol to the test tube containing oil.

• Shake the solution to mix it well.

Result:

• A milky suspension will be formed. 

Mechanism of action of enzymes

 There are two models of enzyme actions; lock-and -key model first proposed in1894 by German biochemist named Fischer and induced-fit-model proposed in 1958 by Koshland.

 Both models suggest that the enzyme catalyzes the reaction by lowering the activation energy.

 However they differ in the way that they explain how this happens.

• Especially in the way the substrate binds to the active sit.
• Lock-and-key mode
• proposes that the shapes of the substrate molecules are complementary to that of the active sites.

• Induced-fit-model Proposes the active site and the substrate do not complement each other but the binding of the substrate molecules produces a change in the shape in the active site, allowing substrate to fit the active site. 

The action of salivary amylase on a starch 

 The saliva contains an enzyme called salivary amylase which hydrolyses starch into maltose.

Materials Required

Three series of test tubes having iodine solution in each, test tubes, ice cubes, water, 15 ml 1% starch solution + 3 ml 1% NaCl, saliva solution, droppers, thermometer, Bunsen burner and wire gauze. (each materials to be animated) Procedure:

• Take beaker containing 15 ml of 1% starch solution + 3 ml of 1% NaCl solution.

• Divide and pour this solution into three test tubes and mark them as A, B and C.

• Maintain the temperature of the beaker containing ice cubes at 5°C.

• Take beaker containing ice cubes and keep it on the table.

• Take another two beakers containing water and heat over the Bunsen burner.

• Now transfer experimental tube A into a beaker containing ice.

• Transfer the second experimental tube B into water bath set at 37°C and third experimental tube C into the beaker maintained at 50°C

.• Using a dropper, take 1 ml saliva solution and transfer the solution into test tube A.

• Similarly, add 1 ml saliva solution into test tube B and test tube C.

• Immediately, using a dropper, take few drops from experimental tube A and transfer this into first series of test tubes having iodine solution.

• Similarly, using fresh droppers, do the same procedure for test tube B and test tube C and transfer the solution into second and third series of test tubes having iodine solution.

• Note this time as zero minute reading.

• After an interval of 2 minutes, again take a few drops from each tube and add to the iodine tubes and note the change in color of iodine.

• Keep on repeating the experiment at an interval of every 2 minutes till color of iodine does not change.

Results:

It takes less time to reach achromic point at 37°C, as the enzyme is maximum active at this temperature, while at higher and lower temperatures more time is taken to  reach the achromic point. 

Osmosis

• Osmosis is the process in which solvent molecules moves through a semi-permeable membrane from a region of higher concentration to a region of lower concentration until the amount of fluid is equalized on both sides of the semipermeable membrane.

• To see this phenomena experimentally, materials required,
• Procedure

• 1. Place the peeled potato on the tile and using the knife, cut both ends of the potato to make it flat.
• 2. Use the knife to make a cavity at the center of the potato from one of the flat sides almost up to the bottom.
• 3. Pour distilled water into the Petri dish until it is half full.
• 4. Now, place the potato in the Petri dish.
• 5. Fill half the cavity made in the potato with 20% sugar solution.
• 6. Mark the level of sugar solution in the cavity using a pin.
• 7. The potato now functions as an osmometer.
• 8. Leave the osmometer undisturbed for about two hours.
• 9. Mark the rise in the level of the sugar solution in the cavity with another pin.
• Result
• The level of sugar solution in the potato cavity rises after some time due to the entry of water into the sugar solution through the selectively permeable membrane of the cells of the potato. 

Plasmolysis

 Plasmolysis is the process of shrinkage or contraction of the protoplasm of a plant cell as a result of loss of water from the cell.

 Plasmolysis is one of the results of osmosis and occurs very rarely in nature, but it happens in some extreme conditions.

 We can induce plasmolysis in the laboratory by immersing living cell in a strong salt solution or sugar solution to lose water from the cell.

 Materials required for this experiment includes

Procedure

• Take two glass slides and place them on the table.

• Take a rhoeo leaf from the Petri dish.

• Fold the leaf and tear it along the lower side of the leaf.

• Using a forceps, pull out two small segments of thin transparent layer from the lower epidermis of the rhoeo leaf.

• Place the epidermal peels on both glass slides.

• Using a dropper, take some sodium chloride 0.1% solution from the beaker.

• Put 1 to 2 drops of solution on one slide.

• Using another dropper, take sodium chloride 5% solution from the beaker.

• Put 1 to 2 drops of solution on the next slide.

• Place a cover slip over the peel of both slides using a needle.

• Place the slides one by one under the compound microscope.

• Observe them under the microscope.

Result:

After half an hour we can observe that cells in sodium chloride 0.1% solution appear turgid, while cells in the sodium chloride 5 % solution show plasmolysis.

Transpiration

 Transpiration is the process of water movement through a plant and its evaporation into the atmosphere from its aerial parts.

 In leaves and in young shoots the epidermal layer contains minute microscopic pore like structures called stomata.

 Transpiration occurs chiefly through the stomata of the leaves.

Materials needed;

Procedure:

• Take 3 % cobalt chloride solution from beaker and pour into the Petri dish.

• Take some filter paper strips and dip them in the cobalt chloride solution.

• Keep the strips in the solution for 3-5 minutes.

They become pink in color when wet.

• Remove the strips from the solution using forceps.

• Place the strips on the wire gauss to allow them to dry.

• The filter paper becomes blue in color on drying.

• Select one healthy leaf and clean the leaf to remove the water droplets using a filter paper.

• Take the dry pieces of cobalt chloride paper from the wire gauze.

• Place the dried strips of cobalt chloride paper: one on the upper and the other on the lower surface of a leaf of the potted plant.

• Take two glass slides and place one over the upper and the other over the lower side of the leaf.

• Clip the slides together using binder clips.

Note the time taken by the cobalt chloride paper to change its blue color to pink.

Result:

The time taken to change color of the cobalt chloride paper from blue to pink on the lower leaf surface is less than the upper surface. 

Rate of respiration

 Respiration is the process during which simple carbohydrates, like glucose, break down into simpler substances and liberate carbon dioxide and energy.

 The compound used, or oxidized, during respiration is called a respiratory substrate.

 The rate of respiration can be measured in terms of gas exchange, that is, consumption of the respiratory substrate oxygen, or evolution of carbon dioxide.  Materials required for this experiment includes, Procedure

• Using a spatula, place about 30 germinating bean seeds in a conical flask.

• Pour 4ml of potassium hydroxide solution into a measuring cylinder.

• Transfer the potassium hydroxide solution from the measuring cylinder into a small test tube.

• Tie a cotton thread around the neck of the test tube.

• Suspend the test tube in the conical flask above the germinating seeds.

• Close the mouth of the conical flask with a cork.

• Insert one end of a delivery tube into the conical flask through the cork and dip the other in a beaker containing water.

• Observe the position of the water level in the delivery tube. This is the initial reading of the water level in the delivery tube.

• Use your finger to take some petroleum jelly.

• Apply the petroleum jelly on the cork to make the apparatus air tight.• Keep the apparatus undisturbed for two hours.

Result:

After two hours, you will see that the level of water has risen in the delivery tube at the end dipped in the beaker of water. Note this level as the final level.

Photosynthesis  Photosynthesis is the process in which light energy is converted into chemical energy. Using the energy of light, carbohydrates such as sugars are synthesised from carbon dioxide and water.

 The name photosynthesis is derived from the Greek words, photo for ‘light’ and synthesis meaning ‘putting together’  Oxygen is also released, as a waste product. Light is the major factor for photosynthesis to take place and by doing this experiment we need to prove that light is necessary for photosynthesis. Materials required Procedure:

1. Take a healthy potted plant and keep it in a dark place for 2-3 days, this de-starches the leaves.

2. Cut out two uniform strips of black paper.

3. Select a healthy de-starched leaf and cover a portion of the leaf on both sides using these two uniform pieces of black paper.

4. Fix both the ends of the black paper to the leaf using paper clips.

5. Now, place the potted plant in sunlight for a whole day.

6. Pluck the covered leaf in the late afternoon and remove the black paper from the leaf.

7. Take a beaker containing distilled water and place it over a hot plate and boil the water.

8. Put the experimental leaf in to the boiling water and boil it for 5-10 minutes till the leaf becomes soft.

9. Remove the beaker from the hot plate and allow it to cool for some time.

10. Take another beaker containing distilled water and place it over the hot plate and boil it at about 60oC.

11. Pour some alcohol into a clean boiling tube.

12. Place the boiling tube in the beaker with water that is being boiled.

13. Remove the leaf from the beaker using a forceps.

14. Place the leaf in the boiling tube containing alcohol.

15. Keep the boiling tube in the beaker till the leaf becomes colourless.

16. Remove the leaf from the boiling tube using the forceps.

17. Dip the leaf in a beaker containing distilled water and wash it.

18. Now place the leaf in a Petri dish.

19. Using a dropper take few drops of iodine solution and pour this drop by drop on the leaf.

Result:

• After iodine treatment, the colour of the exposed portion of the leaf turns blue-black.

• The colour of the unexposed portion of the leaf turns pale yellowish brown. 

Separating photosynthesis pigment

 Photosynthetic plants convert light energy from the sun to chemical food energy. During photosynthesis, molecules referred to as pigments are used to capture light energy.

 Pigments are chemical compounds which reflect only certain wavelengths of visible light. Plant leaves contain four primary pigments: chlorophyll a (dark green), chlorophyll b (yellowish-green), xanthophyll's (yellow) and carotenoids (orange).

 To separate and visualize the four primary pigments of green plants, we can use a simple technique called chromatography.

 For this experiment we need the following materials

Procedure:

 Take a few freshly plucked green spinach leaves.

 Using scissors, cut the spinach leaves into small pieces and let them fall into the mortar.

 Take a measuring cylinder that contains 5ml of acetone and pour it into the mortar.

 Grind the spinach leaves using the mortar and pestle.

 Place the extract into a watch glass using a spatula.

 Take a strip of filter paper having a narrow notch at one end of the strip.

 Take a pencil and a scale and draw a horizontal line with a pencil about 2-3 cm away from the tip of the notch.

 Put a drop of the pigment extract in the middle of the line with the help of a capillary tube.

 Allow the drop to dry and repeat till four or five drops are placed on the paper.

 Take the chromatographic chamber and pour ether acetone solvent in it.

 Fold one end of the filter paper strip and staple it.

 Using a thread, hang the filter paper strip in the chromatographic chamber.

 The loading spot should remain about 1 cm above the solvent level.

 Leave the chromatographic chamber undisturbed for some time.

 We can observe, as the solvent moves through the paper, it spreads the different pigments of the mixture to various distances.

 When the solvent rises about 3/4th up the strip, remove the strip carefully and let it dry.

Result:

 The dried chromatographic paper strip shows four distinct paper bands. Different pigments can be identified by their colors