Wednesday, December 22, 2010


Red Blood Cell
Born very early in the born marrow
I pass through blood vessels no matter how narrow
I live but for three months and not a day more
From the lungs, I take up a gas that you need in every flow ... Who am I?

Granulocyte (a leucocyte)
My nucleus is lobed and my cytoplasm granular
A soldier I am with a nucleus irregular
To eat your enemy is my function
And, for that, I have both gut and gumption ... Who am I?

At a cut, I act fast and cause a clot
This is my life, this is my plot
But I do it only when you need me too
For if you lose your blood, you'd soon turn blue ... Who am I?

Lymphocyte / Granulocyte (a leucocyte)
Smooth and large, my nucleus is round
In the lymphatic system am I found
I shoot out antibodies when I get the chance
Pathogens shrivel up and fall into a dead trance ... Who am I?

While blood plasma takes up 55% of blood fluid, blood cells make up the remaining 45%

blood cells : sel-sel darah
blood plasma : plasma darah
blood transport : pengangkutan darah
blood vessel : salur darah
granulocyte : granulosit
interstitial fluid : cecair intertis
leucocyte : leukosit
lymph duct : nodus limfa
lymphatic system : sistem limfa
lymphocyte : limfosit
phagocytes : sel-sel fagositosis
platelet : platlet
valve : injap


Blood plays many important roles, and one of them is transport.

It transports oxygen, enzymes, water, nutrients (glucose, vitamins, minerals, fatty acids, glycerol and amino acids), carbon dioxide, hormones, antibodies, waste substances, and even heat!

Transport of oxygen;
  • Cell involved - Red blood cell
  • Pigment used - Haemoglobin
  • Oxygen transported by the blood in the form of oxyhaemoglobin

Carbon dioxide transported in blood;
  • 70% in the form of hydrogen carbonate ions
  • 23% in the form of carbomino-haemoglobin
  • 7% in the form of dissolved gas in plasma

Possible consiquences to his health if a man's erythrocyte count is below normal;
  • When less oxygen reaches the cells in his body, the man may suffer from anaemia. As a result, he may faint easily, feel tired and be unenergetic.


Study the following details for a better understanding of gametogenesis and what happens after it.
  1. Process and location
    • Male - Spermatogenesis in the testes.
    • Female - Oogenesis in the ovaries.
  2. Parent cell for gametogenesis
    • Male - Primary spermatocyte.
    • Female - Primary oocyte.
  3. Cell produced after Meiosis I
    • Male - Two secondary spermatocytes.
    • Female - One secondary oocyte (X) and one (1st) polar body (Y).
  4. Cell produced after Meiosis II
    • Male - Four spermatids.
    • Female -
      • From the secondary oocyte (X): One ovum + One polar body.
      • From the first polar body (Y): Two other polar bodies.
  5. What happens to cells produced after Meiosis II?
    • Male - Spermatids differentiate into sperms.
    • Female - All three polar bodies will degenerate; only the ovum will survive.
  6. When does Meiosis II occur?
    • Male - Immediately after Meiosis I.
    • Female -
      • For the first polar body: immediately after Meiosis I.
      • For the second oocyte: only after a sperm penetrates the oocyte.
  7. What happens during sexual intercourse?
    • Male - Sperms are ejaculated from a male's penis into a female's vagina.
    • Female - Sperm from a male swim upwards, from a female's vagina, through the cervix, into the uterus and then to the Fallopian tubes.
  8. Site for fertilisation
    • Male - none.
    • Female - In the Fallopian tubes of the female reproductive system.
  9. Product of fertilisation
    • Male - none.
    • Female - A diploid zygote (containing 46 chromosomes), which then develops into an embryo.

What happens after sexual intercourse?
  • Possibility I
    • A sperm meets the secondary oocyte and penetrates it.
    • Meiosis II quickly occurs in the secondary oocyte, and an ovum and a polar body is formed.
    • The polar body degenerates.
    • The nucleus of the ovum fuses with the nucleus of the sperm.
    • Fertilisation is successful and a diploid zygote is formed.
    • The female is pregnant.
  • Possibility II
    • None of the sperms meet the secondary oocyte. This could mean ovulation has
      • not occurred yet;
      • occurred but the secondary oocyte, which can only live for 24 hours, has died.
    • No fertilisation occurs.
    • No zygote is formed.
    • The female is not pregnant; she gets her next period as usual.


  1. State the function of human heart.
    It pumps blood throughout the body.
  2. Everything in heart seems to come in fours:
    There are four main blood vessels in the heart. Name the blood vessels labelled A, B, C and D in the diagram, and state their functions.

    A: Aorta - transports oxygenated blood to all parts of the body from the left ventricle of the heart.

    B: Pulmonary artery - transports deoxygenated blood to the lungs from the right ventricle of the heart.

    C: Pulmonary vein - transports oxygenated blood from the lungs to the left atrium of the heart.

    D: Vena cava - brings in deoxygenated blood from all parts of the body to the right atrium of the heart.
  3. There are four chambers: left atrium, right atrium, left ventricle and right ventricle. Explain why the left ventricle has the thickest muscle wall.
    (Tip: Where does it pump its blood to? Does it undergo high pressure?)
    It must be able to withstand very high pressure because it pumps blood to all parts of the body.
  4. There are four main valves: bicuspid valve, tricuspid valve and two semi-lunar valves. State their function.
    (Tip: All valves ensure a one-way flow of blood)
    • Bicuspid valve - prevents the backflow of blood between the left ventricle and the left atrium.
    • Tricuspid valve - prevents the backflow of blood between the right ventricle and the right atrium.
    • Semi-lunar valves - while one of them prevents the backflow of blood between the left ventricle and aorta, the other prevents it between the right ventricle and the pulmonary artery.
  5. There are four structures involved in the beating of the heart: sinoatrial node (SAN), atrio-ventricular node (AVN), bundle of His and Purkinje fibres. State the functions of the SAN and AVN.
    (Tip: The two nodes act like batteries and generate electrical impulses that cause the cardiac muscles to contract)
    The two nodes act like batteries to produces electrical impulses that cause the cardiac muscles to contract.
  6. The pacemaker of a patient's heart fails to function. An electronic pacemaker is used to replace the original pacemaker. Explain how this works.
    (Tip: Think about the function of the SAN - the electronic pacemaker has the same function)
    The electronic pacemaker generates electrical impulses that make the cardiac muscles contract and the heart beat.
  7. Compare the rate of blood flow in blood vessels A and D.
    (Tip: Which of the blood vessels is an artery or a vein? Which undergoes more pressure? So, in which of them will blood flow more and at a greater speed?)
    • A, the aorta, is the largest artery and undergoes very high pressure. So, in it, blood flows at a greater speed.
    • D, the vena cava, the largest vein, does not undergo as much pressure. Thus, in it, blood flow is slower.


Our blood is exposed to the air when there is a wound. We do not want harmful microorganisms to infect the wound, nor do we wish to lose blood at the site of injury.

The good news is this: our blood contains platelets, which help blood to clot. A clot closes the wound and disallows blood loss.

Question & Answer

1. Which cells and proteins/enzymes are involved in the mechanism of blood clotting? What are their function?
Platelet (cell) - initiates the clotting of blood.
Thrombokinase (enzymes)
- catalyses the conversion of prothrombin to thrombin.

Thrombin (enzymes)
- catalyses the conversion of fibrinogen to fibrin.

Prothrombin (plasma protein)
- produces thrombin when activated.

Fibrinogen (plasma protein)
- produces fibrin when activated.

Fibrin (thread-like structures)
- traps red blood cell to produce a clot.

2. State the characteristics of blood platelets.
No regular shape, mere cell fragments, no nucleus, no haemoglobin.

3. Where are the plasma proteins involved in clotting of blood
a) synthesised?
b) found?
Blood plasma.

4. What happens if:
i) clotting does not happen?

Loss of blood and blood pressure, and infection at the site of the wound due to exposure to microorganisms.
ii) a wounded person suffers from haemophilia?
Blood will not clot when there is a wound, resulting in loss of blood and possible death.

5. Name the factors that may affect the clotting of blood.
Presence of platelets; presence of plasma proteins (prothrombin and fibrinogen); presence of Vit K, calcium and other clotting factors.

6. How does the mechanism of blood clotting work?
i) Cut/wound/exposure of blood to the air.
ii) Platelets release the enzymes thrombokinase.

iii)Thrombokinase converts prothrombin to thrombin.
iv) Thrombin catalyses the conversion of fibrinogen to fibrin.

v) Fibrin traps red blood cells and a clot is then formed.


Gregor Mendel is highly attributed for his work in genetics. The father of genetic studied the inheritance of characteristics from the common garden pea plant, Pisum sativum, and was credited with discovering the two basic laws of inheritance: the law of segregation and the law of independent assortment.
  1. All characteristics are controlled by pair of genes.
  2. a) A characteristic is a distinctive inherited feature. Three examples of characteristics in:
    • Plants - Height of plant, seed colour, seed shape.
    • Animals - Eye colour, height, colour of fur/skin.

    b) A trait is a variant for each characteristic. Two examples of traits in:
    • Plants - Yellow colour of seed, wrinkled seed shape.
    • Animals - Grey fur colour, green eyes.
  3. A gene is a specific segment of DNA.
  4. Two genes, each found on the same locus along a pair of homologous chromosomes, are needed to determine one characteristic.
  5. Each member of the pair of genes determining a particular characteristic is called an allele.
  6. A dominant allele is one which, when present, even singly, is strong enough to determine the phenotype. The two following conditions can allow a dominant allele to express itself in the phenotype.
    a) Homozygous dominant: two dominant alleles present.
    b) Heterozygous dominant: one dominant allele and one recessive allele present.
  7. A recessive allele can only determine a phenotype if it is present on both homologous chromosomes.


Aquatic plants - also called hydrophytic plants or hydrophytes - are plants that have adapted to living in aquatic environments.

One of the main problems facing submerged aquatic plants is their inability to obtain oxygen. Unlike terrestrial plants, these plants cannot obtain the vital gas through their stomata because they are submerged in water.

Therefore, the stems, roots, and leaves of submerged aquatic plants posses aerenchyma cells, which supply oxygen to the rest of the plants.

Aerenchyma is a parenchyma tissue with large intercellular air spaces. It stores and transports oxygen to living tissues.

Air spaces within the tissues help to keep the aquatic plant buoyant so that its leaves can reach the top of the pond, thus maximising the amount of sunlight it receives.

Submerged aquatic plants utilise living in water to their fullest advantage. Since these plants are in no danger of drying out, the leaves have few or no cuticles on the surface of their leaves.

In addition, the stems of these plants are limp and delicate with little strengthening tissue because they utilise the water for support.

The leaves tend to be thin, flexible and narrow. These finely dissected leaves offer little resistance to running water and can be dragged through the water without tearing.

Characteristics of hydrophytes:

1. A thin cuticle. Cuticles primarily prevent water loss, thus most hydrophytes have no need for cuticles.
2. Stomata that are open most of time because water is abundant and therefore there is no need for it to be retained in the plant. This means that guard cells on the stomata are generally inactive.
3. An increased number of stomata, that can be on either side of leaves.
4. A less rigid structure: water pressure supports them.
5. Flat leaves on surface plants for floatation.
6. Air sacs for floatation.
7. Smaller roots: water can diffuse directly into leaves.
8. Feathery roots: no need to support the plant.
9. Specialized roots able to take in oxygen.

For example, some species of buttercup (genus Ranunculus) float slightly submerged in water; only the flowers extend above the water. Their leaves and roots are long and thin and almost hair-like; this helps spread the mass of the plant over a wide area, making it more buoyant. Long roots and thin leaves also provide a greater surface area for uptake of mineral solutes and oxygen.

Wide flat leaves in water lilies (family Nymphaeaceae) help distribute weight over a large area, thus helping them float near surface.

Many fish keepers keep aquatic plants in their tanks to control phytoplankton and moss by removing metabolites.

Many species of aquatic plant are invasive species in different parts of the world. Aquatic plants make particularly good weeds because they reproduce vegetatively from fragments.