Bioaa

Chapter 2

Cell Structure and function

Preparing and studying slides of plant cells

Materials - An Onion bulb, iodine and distilled water

Apparatus – Glass slide, cover slips, a light microscope, forceps, glass dropper, scalpel, mounting needle , filter paper

Procedure

A piece of onion scale is cut from an onion bulb using a scalpel.

The transparent epidermis from the inner surface of the onion is gently peeled off using a pair of forceps.

Put a drop of water onto the middle of the slide and place the epidermis on the drop of water.

With the help of a mounting needle, cover the specimen with a cover slip lowering it slowly.

Add a drop of iodine solution onto one side of the cover slip.

Place a filter paper at the opposite end to allow iodine to spread through the epidermis

Excess iodine solution is absorbed using another filter paper.

The slide is examined.

Observation

Conclusion

A typical plant cell has a fixed shape , cell wall, nucleus, cytoplalsm and a large vacuole.

Preparing and studying slides of animal cells

Materials – cheek cells, methylene blue solution, iodine solution and distilled water

Apparatus – Glass slide, cover slips, a light microscope, glass dropper, mounting needle , filter paper, toothe pick

Procedure

A blunt end of a clean toothpick is used to gently scrape the inner lining of the cheek.

The scrapings are mounted in a drop of water on a clean glass slide.

The specimen is the slowly covered with a cover slip using a mounting needle

A drop of methylene blue is laced onto one side of the cover slip. A filter paper is then placed at the opposite side of the cover slip to draw the solution across the specimen.

The slide is observed.

The steps are repeated using iodine solution.

Observation

Conclusion

A typical plant cell does not have a fixed shape. But has nucleus and cytoplalsm

Chapter 3

Movement of subtances across plasma membrane

Studying the movement of subtances across the plasma membrane

Problem Statement

What factor influences the diffusion of substances across a semi permeable membrane

Variable

Manipulated- Size of solute molecules

Responding- Colour of solution in the visking tube

Constant- Surrounding temperature

Hypothesis

The diffusion of molecules through a semi permeable membrane is based on the size of the molecules

Material- Benedict’s solution , 1% Starch suspension, Iodine solution, 30% glucose solution, visking tubing, cotton thread

Apparatus- Test tubes, beakers, Bunsen burners

Procedure

A visking tubing is soaked in the water for 5 minutes to soften it. One end of the visking tubing is tied firmly with a piece of cotton thread to prevent leakage.

The visking tubing is filled with 15ml of glucose solution and 15ml of starch suspension. other end of the visking tubing is tied with another piece of cotton thread. The colour is recorded.

The outer surface of the visking tubing is rinsed with water.

400ml of disttiled water and 15 ml of iodine are mixed in a beaker. The colour is recorded.

The visking tubing is immersed in the beaker solution for 40 minutes.

After 40 minutes, the visking tubing is transferred to a dry beaker. The colour of the solutions in the visking tubing and beaker is observed and recorded.

Both solutions are tested for the presence of glucose using benedicts solution. 2ml of each solution are poured into the separate tubes and 1 ml of benedicts is then added to each test tube.

The solution is heated in a boling water bath for 5 minutes and the change in colour is recorded.

Results

Visking tubing

15 ml of glucose + 15 ml of starch suspension

Colourless Blue black Positive. A brick red precipitate is formed

Beaker 400ml of distilled water + 15 ml of iodine solution

Yellow Yellow Positive. A brick red precipitate is formed

Conclusion

The diffusion of molecules across the semi permeable membraneis based on the size of molecules.

The Hyphothesis is accepted.

Chapter 3

Studying the osmosis using osmometer

Problem Statement

What substances can diffuse across a semi permeable membrane

Variable

Manipulated- Time

Responding- Increase in level of sucrose solution

Constant- Surrounding temperature and concentration of sucrose

Hypothesis

Water molecules can diffuse thorugh a semi permeable membrane

Material- 30% sucrose solution, distilled water, visking tubing, cottong thread

Apparatus- Retort stand, Cappilary tube, a ruler, marker pen, scissors, 250ml beaker, syringe, stopwatch

Procedure

A visking tubing about 8cm long is cut

The visking tubing is soaked in water for about 5 minutes to soften it.

One end of the tube is tightly tied with a piece of cotton thread. The visking tubing is filled with 30% sucrose solution using a syringe.

The other end of the visking tubing Is tied to the bottom of the capillary tube.

The outer surface of the visking tubing is rinsed with distilled water

The capillary is the clamped vertically to the retort stand. The visking tubing is then immersed into a beaker filled with distilled water.

The initial level of the sucrose solution is marked with a marker pen at the beginning of the experiment. The level of sucrose solution is then marked and recorded every 10minutes for a duration of 40 minutes .

Results

Time 0 10 20 30 40

The increase in height of sucrose solution from the initial level

0 30 60 90 108

Conclusion

Small molecules like water can easily duffuse through semi permeable membranes such as the visking tubing. The increase in the level of the sucrose solution is due to the process of osmosis. Hyphothesis is accepeted.

Effects of hypotonic, hypertonic and isotonic solutions on animal cells.

AimTo study the effects of hypotonic, hypertonic and isotonic solutions on animal cells.

Materials- Fresh chicken blood, 0.15 M sodium chloride solutions, 0.50 M sodium chloride solutions,Distilled water, Filter paperApparatus- Glass slides, Cover slips, Filter papers, Light microscope, Test tubes, Beakers, Dropper

Procedure

4 slides were labeled as A, B, C and D.

A drop of blood was dropped on slide A and covered with a cover slip and is observedunder a light microscope.

A drop of distilled water was dropped on slide B and covered with a cover slip. A dropof blood was put at one side of the cover slip.The blood is allowed to spread by placing a filter paper on the opposite side.

The slide was observed under a light microscope .

Steps 3 and 4 were repeated using 0.15 and 0.50M sodium chloride solutions on slideC and D respectively.

Observations

Slide Observation Discussion

A Red blood cell have biconcave shape

Shape is normal

B(red blood cells in distilled water)

Cells swell and burst The red blood cell are placed in a hypotonic solutionWater diffuses into the red blood cells by osmosis causing cells to swell and burstThe contents are released to the surroundingsHaemolysis occurs

C(red blood cells in 0.15m sodium chloride)

Red blood cells retain their shape and size

The concentration is isotonic to the cytoplasmic fluidNo net movement of water in and out

D(redblood cells in 0.50 sodium chloride)

Red blood cells shrink and crenate

The concentration is hypertonic to the cytoplasmis fluid of red blood cellsThere is a net of outflow of water from the cells by osmosis. The cell have become shrivelled.

Conclusion

Observation on animal cells in above .

Effects of hypotonic, hypertonic and isotonic solutions on plant cells.

Aim To study the effects of hypotonic, hypertonic and isotonic solutions on plant cells.

MaterialOnion bulb, 0.5 M sucrose solutions, 1.0 M sucrose solutions, Distilled water

ApparatusLight microscope, Glass slides, Cover slips, Razor blade / scalpel, A pair of forceps, Mounting needle, Filter papers

ProcedureFour slides are prepared and labelled A,B,C and D

A thin layer of epidermal cell of onion was stripped using a pair of forceps and mounted on slide A.

A drop of distilled water was dropped on it and covered with a cover slip.

The slide was examined under a light microscope using low power and then high power.

The epidermal cells are drawn and labelled.

A drop of 0.5M sucrose solution is placed at one side of the cover slip. The solution is allowed to spread by placing a filter place at the opposite end of the cover slip.

The epidermal cells are then observed under the microscope. The epidermal cells are drawn and labelled.

Steps 6 and 7 are repeated by substituting 0.5 m with 1.0 m sucrose solution

Observations

Slide Observation Discussion

A(plant cells in distilled water)

Cells appear turgid. The vacuoles swell up into larger sizes.

The distilled water is hypotonic to the cell sap of the epidermal cellsThe net flow of water by osmosis into the vacuoles cause them to swellAt this point, the cells are highly turgid. The vacuoles and cytoplasm exert an outward force against the plasma membrane and cell wall. The cells do not burst because of their rigid cell walls.

B(plant cells in 0.5M sucrose solution)

The shape and the structure remains the same.

0.5M is isotonic to the cell sapThe cells do not lose or gain water.

C(plant cells in 1.0M sucrose solution)

The epidermal cells looks flaccid, the vacuoles loses water and becomes smaller. The cytoplasm shrinks and the plasma membrane pulls away from the cell wall.

1.0M is hypertonic to the cell sap of the epidermal cells.There is net outflow of water from the vacuoles by osmosis.The plant cells have undergone plasmolysis.

Conclusion

Observation on plant cells in above .

Concentration of an external solution which is isotonic to the cell sap of a plant

Aim To determine the concentration of an external solution which is isotonic to the cell sap of a plant

Problem statementWhat is the concentration of an external solution which is isotonic to the cell sap of a plant?

HypothesisWhen the external solution is isotonic to the cell sap of the plant, there is no net gain in the size of the plant cell

Variable

Constant :

Manipulated :

Responding

MaterialPotato, distilled water, filter paper and sucrose solutions with concentration of 0.1M, 0.2M, 0.3M, 0.4M, 0.5 and 0.6M

ApparatusPetri dishes, knife, forceps, ruler and cork borer

Procedure

7 petri dishes were labeled as A – G.

Petri dish A was filled with distilled water

Each petri dish was filled with different solution according to the table below:Petri dish B C D E F GSucrose solution(M)0.1 0.2 0.3 0.4 0.5 0.6

A cork borer was used to bore 21 potatoes in cylindrical strips. Each strip was cut to a length of 5cm.

3 strips were placed in each petri dish and left for an hour.

After an hour, the strips were removed. The potato strips were wiped dry and the length of each strip was measured.

Measurements were recorded.

A graph of elongation of potato strip against the concentration of sucrose solution was plotted.

Observations

Differentiating between reducing and non-reducing sugars

MaterialBenedict’s solution, dilute hydrochloric acid, sodium hydrogen carbonate powder, 10% glucose solution and 10% sucrose solution.

ApparatusTest tubes, beaker, dropper, tripod stand, wire gauze, Bunsen burner

Procedure2ml of benedict’s solution is added to an equal volume of glucose solution in a test tube.

The mixture is shaken and then heated by placing the test tube in a beaker of boiling water for a few minutes.

The colour of the precipitate that is formed is observed.

The test is repeated by replacing the glucose solution with sucrose solution.

If the sucrose solution produces a negative result, the experiment is continued, using another sample of sucrose solution. This time the sucrose solution is added to 1ml of dilute hydrochloric acid and bolied for a few minutes.

The mixture is then left to cool

A small amount of sodium hydrogen carbonat is added ti neutralise the acid.

Steps 1 tlo 3 are repeated when the effervescence stops.

The colour of the precipitate formed is observed and recorded in the table below.

Observations

Sugar Observation InferenceGlucose A bric red precipitate is

formedGlucose is a reducing sugar

Sucrose (without HCL) The colour of the benedict’s solution remains unchanged

Sucrose is a non reducing sugar

Sucrose (bolied w HCL) A brick red precipitate is formed

A positive result with Benedicts solution can only be obtained if the sucrose solution is first bolied with HCL

Conclusion

Reducing sugar produce red brick precipitate when tested with Benedicts solution.

Effect of temperature on the activity of enzyme amylase on starch

AimTo study the effect of temperature on the activity of enzyme amylase on starch

Problem statementWhat is the effect of temperature on the activity of enzyme amylase on starch?

Hypothesis

The rate of the activity on salivary amylase on starch increase with the increase in temperature until it reaches the optimum temperature of 37.

Variables

Constant :Volum of saliva, volume and concentration of starch suspension, Ph of medium

Manipulated : Temperature of medium

Responding : Rate of enzymatic reaction

Materials 1 % starch solution, iodine solution, ice, distilled water

Apparatus 5 beakers, 10 test tubes, syringe, glass rod, dropper, white tile, thermometer, Bunsen burner, tripod stand, wire gauze, stop watch

Procedure5 ml of saliva was collected in a beaker after rinsing one’s mouth with clean water.5 ml of distilled water was added into the beaker to dilute the saliva.

5 test tubes were labeled as A, B, C, D and E and each of it were filled with 2 ml ofsaliva.

5 test tubes were labeled as A1, B1, C1, D1 and E1 and each of it were filled with 5ml of starch solution.

Test tubes A and A1, B and B1 , C and C1, D and D1, E and E1 areimmeredsed respectively into five different water baths with temperature which are kept constant at 0, 28 37 ,45 and 60

The test tubes are left for 5 minutes

A drop of iodine solution Is placed into each groove of the white tile.

After five minutes, the starch suspension in test tube A1 is poured into the saliva solution in A.

The mixture is stirred using a glass rod. A stopwatch is started immediately

Use a dropper to remove a drop of mixture from the test tube and place It into iodine solution in the first groove. ( counted as zero minute)

The iodine test is repeated every minute 10 minutes. The dropper is rinsed in a beaker distilled water after each sampling.

Record the time taken for the completion of the hydrolysis of starch that is when the mixture gives a negative iodine test (no longer turns blue black)

The test tubes containing mixture are kept in their respective water baths throughout experiment.Steps are repeated for test tubes B,C,D,E

Observation

Test Tubes Temperature Time take for Hydrolysis of

starchTo be completed

Rate of enzymatic reaction

1/t (minute)

A 0 Not completed after 10 minutes

0

B28 2 0.50

C37 1 1

D45 3 0.33

E 60 Not completed after 10 minutes

0

Conclusion

Changes in temperature affect the activity of salivary amylase on starch. Salivary amylase is inactive at 0 and denatures at 60

The rate of reaction catalysed by the salvary amylase is highest at 37 which is optimum temperature. Hyphothesis is accepted.

Effect of pH on the enzyme activity

Aim To study the effect of pH on the enzyme activity

ProblemstatementWhat is the effect of pH on the enzyme activity

Hypothesis Pepsin works best in acidic mediumVariables

Constant : Volume and concentration of albumen suspension, volume and concentration of pepsin solution and temperature of medium.

Manipulated : pH of Medium

Responding Rate of enzymatic reaction

MaterialsAlbumen suspension, 1% pepsin solution, 0.1M hydrochloric acid, 0.1 M sodium hydroxide solution, pH paper, distilled waterApparatus Test tube, syringe, thermometer, stopwatch, beaker, Bunsen burner tripod stand, filter funnel,wire gauze

ProcedurePrepare and albumen suspension by mixing egg white with 500ml of ditilled water. Boil the suspension and leave it to cool.Discharge large particles using glass wool.

Label the three test tubes P,Q and R

5ml of albumin suspension was poured into each test tube, P, Q and R.

The following solutions were added into each test tube.Test tube SolutionP 1 ml hydrochloric acid + 1 ml pepsinsolutionQ 1 ml sodium hydroxide + 1 ml pepsinsolutionR 1 ml distilled water + 1 ml pepsinsolution

A piece of pH paper was dipped into each test tube. The pH value was recorded.

All test tubes were placed into a beaker of water bath at 370C for 20 minutes.

The change in the content of the test tube was observed and recorded.

Observation

Test tubes Ph Mixture

Beginning End

P 3 Cloudy Clear

Q 7 Cloudy Cloudy

R 8 Cloudy Cloudy

Conclusion

The activity of pepsin is affected by the Ph of its medium. An acidic medium pH3 is the most suitable medium for pepsin to function effieciently

The hyphothesis is accepted

Effects of substrate concentration on the activity of salivary amylase

Problem statementWhat is the effect of substrate concentration on the activity of salivary amylase

HyphothesisThe rate of enzymatic reaction increases with the increase in substarte concentration until it reaches a maximum rate.

Constant

Manipulated: concentration of starch

Responding Time taken for hydrolysis of starch to be completed

Constant Enzyme concentration, Temperature and pH of medium

MaterialStarch suspensions at various concentrations, 0.1% amylase or saliva suspension, iodine, distilled water

Apparatustest tubes, syringe, dropper, glass rod, white tile, wire gauze, measuring cylinder stopwatch

Procedure

Six test tubes were labeled as A, B, C, D, E and F.

4ml of starch suspension of various concentrations are poured into the following test tubes A,B,C,D,E,F

Test tubes are immeredsed respectively in water bath of 37

A drop of iodine solution is placed into each groove of the white tile.

1ml of 0.1% amylase is added to test tube A using a syringe

The stopwatch is started immediately. The contents are stirred with a glass rod.A drop of mixture is tested with the iodine solution on the white tile.

This step is repeated every 30 second interval until the mixture stops turning blue black. The time take for the starch to be completely hydrolysed is recorded.

Steps were repeated for test tubes B, C, D, E and F.At every sampling, the dropper must be rinsed with clean distilled water.

Observations

Test Tube

Concentration of starch

suspension

Time taken for hydrolysed of starch to

be completed

Rate of Reaction

= (substrate concentration/time)

(% minute)

A 0.1 240 4.0 0.025

B 0.2 240 4.0 0.050

C 0.3 240 4.0 0.075

D 0.4 240 4.0 0.100

E 0.5 300 5.0 0.100

F 0.6 360 6.0 0.100

Conclusion

The rate of enzymatic reaction increases with the increase in substrate concentration until it reaches maximum rate.

The hyphothesis is accepted.

Effect of enzyme concnetration on the activity of salivary amylase

Problem statementWhat are the effects of enzyme concentration on the activity of salivary amylase

HypothesisThe rate of enzymatic reaction increase with the increase in enzymatic concentration as long as there are no factors limiting the rate of reaction.

Variables

Constant : Substrate concentration, Temperature and Ph of medium Manipulated : Concentration of enzyme

Responding : time taken for the hydrolysis of starch to be completed

Materials 1 % starch solution, 0.8% amylase or saliva suspension ,iodine solution, distilled water

Apparatus test tubes, syringe, dropper, glass rod, white tile, wire gauze, measuring cylinder stopwatch

ProcedureSix test tubes were labeled as A, B, C, D, E and F.The test tubes contain the following mixtures

A : 0.5ml of 0.8% amylase + 2.5ml distilled waterB : 1.0ml of 0.8% amylase + 2.0ml distilled waterC : 1.5ml of 0.8% amylase + 1.5ml distilled waterD : 2.0ml of 0.8% amylase + 1.0ml distilled waterE : 2.5ml of 0.8% amylase + 0.5ml distilled waterF : 3.0ml of 0.8% amylase

Test tubes are immersed respectively in water bath of 37

A drop of iodine solution is placed into each groove of the white tile.

4ml of 1% of starch suspension is added to test tube A using a syringe

The stopwatch is started immediately. The contents are stirred with a glass rod.A drop of mixture is tested with the iodine solution on the white tile.

This step is repeated every 30 second interval until the mixture stops turning blue black. The time take for the starch to be completely hydrolysed is recorded.

All results are recorded and tabulated

Observation

Test Tubes Concentration of amylas

Time take for Hydrolysis of

Rate of enzymatic

starchTo be completed

reaction1/t (minute)

Seconds minutes

A 0.17 330 5.5 0.18

B 0.33 150 2.5 0.40

C 0.50 90 1.5 0.67

D 0.67 60 1.0 1.00

E 0.83 60 1.0 1.00

F 1.00 60 1.0 1.00

Conclusion

The rate of reaction increases with the increase in enzyme concentration until a certain concentration of enzyme is achieved.

The hyphothesis is accepted.

Conclusion

Changes in temperature affect the activity of salivary amylase on starch. Salivary amylase is inactive at 0 and denatures at 60

The rate of reaction catalysed by the salvary amylase is highest at 37 which is optimum temperature. Hyphothesis is accepted.