Thursday, March 26, 2009

Biology ~ Experiment of Visking tubing

Appendix ~ Experiment 3.1

The movement of substances across a semi- permeable membrane

Title : The movement of substances across a semi permeable membrane

Objective : To study the movement of substances across a semi permeable membrane

Problem statement : What factor influences the diffusion of substances through a semi permeable membrane?

Hypothesis : The diffusion of molecules across a semi permeable membrane is based on the size of the molecule


a) Manipulated : Size of solute molecules

b) Responding : Colour of solution

c) Fixed : Temperature and time

Materials : Iodine solution, Benedict’s solution, 1% starch suspension, 30% glucose solution and distilled water

Apparatus : A Visking tube, cotton thread, test tubes, beaker and water bath


- Soak the Visking tube in water for 5 minutes to soften it. Open the Visking tube and tie one end of the tube with cotton thread to prevent leakage.

- Fill the Visking tube with 15ml of glucose solution and 15ml of starch suspension. Tie the other end of tube tightly with cotton thread. Record the colour of the solution

- Rinse the outer surface of Visking tube with distilled water.

- Mix 400ml of distilled water with 15ml iodine solution in a beaker. Record the coilour of the solution

- Place the Visking tube in the beaker and leave it for 40 minutes.

- After 40 minutes, take the Visking tube out and put aside

- Observe and record the colour of solution in the Visking tube and in the beaker.

- Test both solutions for the presence of glucose using Benedict’s solution. Pour 2ml of each solution into separate test tube and add 1ml of Benedict’s solution. Heat the mixture in the water bath for 5 minutes and record the colour change.

Result :

Solution in




Benedict’s test

Initial colour

Final colour

Visking tube

15 ml sucrose solution + 15 ml starch solution

White precipitate

Blue black
( positive for starch)

Brick red colour

(positive for sucrose)


Distilled water +

20 drops iodine solution


Yellow (negative for starch)

Brick red precipitate (positive for sucrose)


  1. Based on the results, make an inference regarding the size of the iodine molecules as compared to the size of the starch molecules.
    - comment on size of iodine compared to starch molecules
    - then relate the size of iodine to the ability of iodine to diffuse through Visking tubing

  2. What are inference can you make regarding the size of the starch molecules when compared to the size of the pores on the Visking tube?
    comment on size of starch compared to iodine molecules
    - then relate the size of starch to the ability of starch to diffuse through Visking tubing

  3. What do the results of Benedict’s test show? What inference can you make from the result?
    - Benedict test is use to test the presence of glucose (sucrose) in a solution.
    - 2ml of solution which we want to test is pour in a test tube, then add several drops of benedict's solution before heating the test tube for about 5 minutes.
    - If the color of solution change into brick red precipitate at the end, that show that positive for glucose test ( means glucose is present)

  4. Predict the outcome of the result if the experiment is repeated by filling the Visking tube with glucose solution and the beaker with starch suspension?
    - What will happen if we change the solution for this experiment?
    - Glucose solution will diffuse from region to what region? What will be happen in iodine test and Benedict's test?

  5. Based on the experiment, what analogy can you make between the Visking tube and the digestive system?

- we know that digestive system function in absorbing nutrients from foor digestion.

- So, both only allow certain molecules to pass through depend upon the size


  1. Comment on your hypothesis. Is your hypothesis accepted or rejected?

Monday, March 23, 2009

Biology ~ Passive transport and active transport


1.Passive transport
• Simple diffusion
• Facilitated diffusion
• Osmosis
-no require energy

2.Active transport
- require energy



• movement of substances such as oxygen and lipid soluble
• from higher concentration region to the lower concentration region
• across the plasma membrane or not


• movement of water
• from lower concentration region to the higher concentration region
• across the plasma membrane


• transport of substances such as non-soluble substance, ion and large molecules
• from higher concentration region to the lower concentration region
• through carrier protein


• movement of substances such as ion at root hair, glucose and amino acid
• from lower concentration region to the higher concentration region
• with the use of energy in the form of ATP



Biology ~ Transport of substances across plasma membrane



Click to see flash animation
fluidity of membrane


1. Draw and label the plasma membrane
2. Describe each structure found in the plasma membrane
3. Explain why the plasma membrane is called fluid mosaic model

Biology ~ Regulating the internal environment


The environment which cells body lives within and usually contains interstitial fluid and blood plasma

- Physical factors: body temperature, blood pressure, osmotic pressure
- Chemical factors : salt content, sugar content, PH value

~> Why need to maintain at optimal level??
- Because to enable cells to function properly
- So, the mechanism to maintain the constant internal environment is called HOMEOSTASIS

- Involves various system
- Usually corrective mechanism that bring back to normal condition, called negative feedback mechanism
Examples of homeostasis is to maintain the body temperature, blood PH and maintain glucose level so that our cells were in optimum level to carry out life process efficiently.

~click below for note on homeostasis

Examples of question:
Explain how body response towards the changed in the osmotic level
(10 points = 10 marks)

- When the osmotic pressure is above the normal level, it means that our body face the loss of water
- So, osmoreceptor in the brains will detect the high osmotic pressure in the blood and it will send impulse to the pituitary glands
- For corrective mechanism, the pituitary gland will secretes the antidiuretic hormones (ADH) into bloodstream
- ADH hormones acts on kidney to absorbs more water back into the body
- So, the osmotic pressure decrease and return to normal
- When the osmotic pressure is below the normal, it means that our body had large intake of water
- Osmoreceptor in the brain will detect the low osmotic pressure in the blood and send impulse to the pituitary gland.
- Corrective mechanism, pituitary gland will secrete less ADH hormone into bloodstream
- So less water is absorbed by kidney
- Negative feedback occur, the osmotic pressure returns to normal

Friday, March 20, 2009

Biology ~ System in multicellular organism


Multicellular organism is made up of many cells which organized to form tissues, organ, system and then the organism. There are plant and animals. We need to know the types of tissues, organs and system which made both plant and animals. But bear in mind that organization in plants is more simple than in animals.

System in plant
-shoot system
-root system

Organ in plant

Tissue in plant
~> Meristematic tissue
-young and actively dividing
-not undergo differentiation
-tip of roots and bud of shoots

~> Permanent tissue
Mature tissue that undergo differentiation
3 types:
-epidermal tissue
-ground tissue that are parenchyma, collenchyma and sclerenchyma
-vascular tissue that are phloem xylem


Explain the leaf as an organ (10 marks)
- click on the image for larger preview-

Thursday, March 19, 2009

Biology ~ The cell organization in multicellular organism


Cell -> Tissue -> Organ-> System -> Organism

Cell = The basic unit of life
Tissue = A group of cells that perform same function
Organ = Made up from several types of tissues & perform specialized function
System = Consist several types of organ
Multicellular organism = From systems that work together

Example of skin as an organ (explanation may worth 10 marks for essay)
~> Characteristic
- Largest organ cover the entire body
- Composed two layers, dermis & epidermis
- Consist various types of tissue such as epithelial tissue, nerve tissue, smooth muscle tissue and connective tissue

~> Function
-Barrier against infections
-Prevent water loss
-Prevent physical trauma

~ Epithelial tissue function as basal layer that undergo continuous cell division
~ Smooth muscle tissue attach to hair follicle as hair erector muscle
~ Sensory nerve ending tissue as eceptor that detect stimuli and send impulse to other part of nervous system
~ Connective tissue such as blood to supply oxygen and nutrient to the cells. Then adipose- stores energy + insulate the body

For system in human, there are about 11 systems and all of those systems have been learned in science subject during form 3. For all of the systems, we need to know the basic function and the organs that made it up. Lets we named all of it:
1. Nervous system
2. Circulatory system
3. Skeletal system
4. Digestive system
5. Respiratory system
6. Reproduction system
7. Excretory system
8. Lymphatic system
9. Muscular system
10. Intergumentary system
11. Endocrine system


- if you want the answer, please leave your e-mail in the comment box =)

Biology ~ The cell organization in unicellular

In this subtopic, we will learn more on:
- The living process in amoeba and paramecium
- The organization in multicellular organism in the form of tissue, organ, system and organism

-Living thing that capable of undergo vital function & living process.

1-Unicellular organism
~ One single cell only
Eg: Paramecium, bacteria, Amoeba

2-Multicellular organism
~ More than one cell
Eg: plant & animal

Unicellular organism – Amoeba sp
-Enclosed by plasma membrane
-Changes shape as respond towards stimuli (eg: food)
-Ectoplasm: gel-like outer part of cytoplasm
-Endoplasm: inner cytoplasm
-Freshwater, ponds, damp soil
-Free living, some parasitic
-Exchange of O2 and CO2 by simple diffusion through plasma membrane
-Waste product removed from cell by simple diffusion
-Osmoregulation by contractile vacuole (removal of excess water)
~>Find more on: Locomotion, Feeding and Reproduction

- The video on Amoeba locomotion -

- The video on Amoeba feeding -

Multicellular organism
~>Multicellular organism is organism that consist of more than one cell
Example: plant, animal

~In multicellular organism, life begin from a single cell that known as zygote.
-Example: human
~The cell grow, change shape and differentiate to carry out specific function.
-Means that a single cell do not have to carry out all vital process such in a single Amoeba to sustain life.

~Cells of multicellular organism differentiate and undergo specialisation to perform task efficiently.
-Example: - Red blood cell for transport
- White blood cell for defence
- Nerve cell for impulse transmission

Structure question

Paramecium is a freshwater protozoan. Answer the following questions.

(a)How many contractile vacuoles present in the paramecium? (1 marks)
(b) (4 marks)
i- Water is always diffusing into the paramecium. Why is this so?
ii- Name the process by which the water enters the paramecium.
iii- Name the substance that is eliminated when the contractile vacuole contracts.
(c)What would be happen to the paramecium of the contractile vacuole stops contracting? (1 marks)
(d)Describe how the paramecium gets its
i- Oxygen supply
ii- Food (4 marks)

Biology ~ Plant and animal cells

The second chapters in Biology form four. We need to know more on:
- How to draw and label the diagram of plant cell and animal cell.
- Characteristic and function of each structure and organelles in the cells.
- The density of certain organelles in specific cells
- The cell organization in unicellular organism


- The living cells -

- The animal cell and plant cell -

- Plant cell

- Animal cell

For each organelle and structure labelled, we must know the characteristic and function.

Match the organelle with exact function

- Click to see larger image -
- if you want the answer, please leave your e-mail in the comment box =)

- Click to see interactive animation of the cell

Biology ~ Careers in Biology

On January'09

The first thing I asked my students to do is the folio entitled 'Careers in Biology'. The scope is to introduce them to the different careers in biology as they need to learn more on different fields in biology

-The description

Folio of Careers Related To Biology

  1. Cover - Title: Careers in Biology

- Name:

- 1/C number :

- Class :

  1. Biodata - Name :

- Gender

- Date of Birth

- Mother’s name

- Father’s name

- Occupation

- Adress

- Result in PMR

  1. Careers in biology (6 – 10 careers for each person)

- A picture ( draw, cut & paste, printout )

- Description

- Roles

Sources :

- Internet

- Newspaper

- Magazines

- Advertisement

Format :

- Use A4 paper

- Handwriting or typing

Example of website

- Google search ~ careers in biology

- Wikipedia search ~

- put the careers name. eg:




- The marking scheme:

- over 100 marks

Submit on due

Biodata included





/10 marks

/10 marks

/30 marks

/20 marks

/20 marks

/10 marks

For my students, I will post the marks of the folio if there is any request.

Saturday, March 14, 2009

d FiRst dAy...

hmm.. i just turn up to have my own blog.. =)
well, i'll keep trying to do my best..