Question and answer about STOMATA

An opening stomata of a tomato leaf

Question 1 : Why does the stomata close during hot weather?

  
Answer :
Stomata, also known as stoma, close in hot weather to retain water. Even though open stoma are necessary for photosynthesis, they can dry out a plant. About 90% of water absorbed by a plant is lost through open stoma. The guard cells close the entrance for protection against dehydration.

Read more: http://wiki.answers.com/Q/Why_does_the_stomata_close_during_hot_weather#ixzz1x7SliJkg

Question 2 : Why does stomata close at night and open during day?

Answer :

Some Stomata close at night because of the heat, while others open at night because of the moisture. CAM plants such as cacti and pineapple open their stomata at night so that the moisture in the air can be absorbed. CAM plants are adapted to hot, dry environments such as deserts, so opening at day would just evaporate any water that the plant had absorbed. So CAM plants open at night and close at day, while plants adapted to environments such as the ones in forest open at day and close at night.

Read more: http://wiki.answers.com/Q/Why_does_stomata_close_at_night_and_open_during_the_day#ixzz1x7TOxCFr

An opening stomata of rose plant

Question 3 : SO, does stomata close or open during hot weather?

Answer (i):

There are multiple parts and functions of the stomata that work during the process of photosynthesis. The specialized guard cells in the stomata of plants are called guard cells; the most important part to the stomata. Guard cells control opening and closing of the pores in the response of the environment (Shuppan). They are undersurface of leaves for controlling gas exchange and water loss of the plant. Guard cells are in pairs and shaped like a kidney bean so that stomata can exist between them. During warm weather, when a plant is likely to lose excessive water the guard cells close eliminating as much water evaporation from the interior of the leaf. 

Read more : http://uwstudentweb.uwyo.edu/d/dbrouss1/stomate.htm

Answer (ii) :

These stomata structures alter in size according to their turgor, which is mostly determined to the water concentration in them. When water concentration drops in the stroma areas, the opening to the external environment closes. Stomata therefore play a regulating role in the homeostasis of water control. During a particular hot day, while the stomata is open for photosynthesis, transpiration can occur at a much higher rate due to the temperature. When this occurs, the water concentration drops in the stomata and therefore it loses turgor, and in turn the stomata opening closes. This ensures that water concentration is kept near its preferred level. This type of water transpiration occurs in mesophyte plants, which occupy climates that are of average rainfall and of average temperature.

Read more : http://www.biology-online.org/5/2_plant_water_regulation.htm

http://www.biologycorner.com/APbiology/cellular/notes_alternative_paths.html

 

Tekanan Darah Rendah / Low Blood Preasure(Hypotension)

 Penyakit tekanan darah rendah atau Hipotensi (Hypotension) adalah suatu keadaan di mana tekanan darah seseorang turun dibawah angka normal, iaitu mencapai nilai rendah 90/60 mmHg. Tidak seperti tekanan darah tinggi, tekanan darah rendah ditentukan terutama oleh tanda-tanda dan gejala-gejala dari aliran darah yang rendah dan bukan oleh angka tekanan darah yang spesifik. Tekanan darah ditentukan oleh dua faktor, iaitu :

i) Jumlah darah yang dipam oleh ventrikel kiri jantung ke dalam arteri-arteri. 

ii) Daya tahan (resisten) pada aliran darah yang disebabkan oleh dinding-dinding dari arteriol (arteri-arteri yang lebih kecil).

 

 Pada umumnya tekanan darah cenderung lebih tinggi jika lebih banyak darah yang dipam ke dalam arteri-arteri atau jika arteriol-arteriol adalah sempit dan keras. Jika arteriol-arteriol sempit dan keras, keadaan ini akan menahan aliran darah, meningkatkan tekanan darah. Sebaliknya, tekanan darah cenderung lebih rendah jika lebih sedikit darah yang dippma ke dalam arteri-arteri atau jika arteriol-arteriol adalah lebih besar dan lebih lentur. Disebabkan itu, ia mempunyai kurang ketahanan (resisten) pada aliran darah.

 Gejala umum pada seseorang yang mengalami tekanan darah rendah adalah mereka sering mengeluh dengan keadaan sering pening, sering menguap, penglihatan terkadang dirasakan kurang jelas terutama selepas duduk lama lalu bangun dan terus berjalan, berpeluh dingin, merasa cepat letih tidak bertenaga, bahkan sehingga boleh mengalami pengsan yang berulang.

 Orang-orang yang mempunyai tekanan darah rendah mempunyai risiko yang lebih rendah dari stroke, ginjal dan jantung. Olahragawan, orang-orang yang berolahraga secara teratur, orang-orang yang memelihara berat badan yang ideal, dan orang-orang bukan perokok cenderung mempunyai tekanan-tekanan darah yang lebih rendah. Oleh karenanya, tekanan darah rendah diinginkan sepanjang ia tidak cukup rendah untuk menyebabkan gejala-gejala dan merosak organ-organ dalam tubuh badan.

 Faktor-faktor yang mengurangkan isipadu darah, mengurangkan jumlah darah yang dipam oleh jantung dan ubat-ubatan adalah penyebab terjadinya tekanan darah rendah. Ada beberapa perkara yang boleh dilakukan untuk memperbaiki keadaan tekanan darah rendah (hipotensi) yang menimpa, di antaranya:
 

i) Minum air putih dalam jumlah yang cukup banyak antara 8 hingga 10 gelas per hari, sesekali minum kopi agar memacu peningkatan degupan jantung sehingga tekanan darah akan meningkat.

ii) Pengambilan ubat-ubatan (meningkatkan darah) hanya dilakukan apabila gejala hipotensi yang dirasakan benar-benar mengganggu aktiviti seharian, selain itu doktor hanya akan memberikan vitamin   support/placebo) serta beberapa saran yang dapat dilakukan bagi pesakit.

iii) Mengambil makanan yang cukup kandungan kadar garamnya.

iv) Pada golongan wanita dianjurkan untuk mengenakan sarung kaki(stocking) yang elastik.

v) Beriadah dengan teratur seperti berjalan pagi selama 30 minit, dengan kadar minimum 3 kali seminggu dapat membantu mengurangkan timbulnya gejala.

Sekali lagi harus difahami bahawa tekanan darah rendah membawa erti bekalan darah tidak maksimum ke seluruh bahagian tubuh badan. Terdapat juga kajian telah membuktikan bahawa pengambilan buah anggur(klik sini) dapat menyembuhkan penyakit tekanan darah rendah.

Blood Clotting Mechanism

What are blood clots? (klik to get the link)

Blood is a liquid that flows within blood vessels. It is constantly in motion as the heart pumps blood through arteries to the different organs and cells of the body. The blood is returned back to the heart by the veins. Veins are squeezed when muscles in the body contract and push the blood back to the heart.

Blood clotting is an important mechanism to help the body repair injured blood vessels. Blood consists of:

• red blood cells containing hemoglobin that carry oxygen to cells and remove carbon dioxide (the waste product of metabolism),
  
• white blood cells that fight infection,
  
• platelets that are part of the clotting process of the body, and
  
• blood plasma, which contains fluid, chemicals and proteins that are important for bodily functions.

Complex mechanisms exist in the bloodstream to form clots where they are needed. If the lining of the blood vessels becomes damaged, platelets are recruited to the injured area to form an initial plug. These activated platelets release chemicals that start the clotting cascade, using a series of clotting factors produced by the body. Ultimately, fibrin is formed, the protein that crosslinks with itself to form a mesh that makes up the final blood clot.

The medical term for a blood clot is a thrombus (plural= thrombi). When a thrombus is formed as part of a normal repair process of the body, there is little consequence. Unfortunately, there are times when a thrombus (blood clot) will form when it is not needed, and this can have potentially significant consequences.

What does a blood clot look like?

Picture of a how blood clot is formed

What causes blood clots?

Blood clots form when there is damage to the lining of a blood vessel, either an artery or a vein. The damage may be obvious, such as a laceration, or may occur on the microscopic level. As well, blood will begin to clot if it stops moving and becomes stagnant.

Injured or cut

Formation of fibrin mesh

The blood start to clot

Fibrin network trap the erythrocyte

Venous thrombosis or blood clots in a vein occur when a person becomes immobilized and muscles are not contracting to push blood back to the heart. This stagnant blood begins to form small clots along the walls of the vein. This initial clot can gradually grow to partially or completely occlude or block the vein and prevent blood from returning to the heart. An analogy to this process is a slow moving river. Over time, weeds and algae start to accumulate along the banks of the river where the water flows more slowly. Gradually, as the weeds start to grow, they begin to invade the center of the river because they can withstand the pressure of the oncoming water flow.

Arterial thrombi (blood clots in an artery) occur by a different mechanism. For those with atherosclerotic disease, plaque deposits form along the lining of the artery and grow to cause narrowing of the vessel. This is the disease process that may cause heart attack, stroke, or peripheral artery disease. If a plaque ruptures, a blood clot can form at the site of that rupture and can completely or partially occlude the blood flow at that point.

Blood clots in the heart. In atrial fibrillation, the atrium or upper chamber of the heart does not beat in an organized manner. Instead, it jiggles, and blood tends to become stagnant along the walls of the atrium. Over time, this may cause small blood clots to form. Clots can also form in the ventricle after a heart attack when part of the heart muscle is injured and unable to contract normally. Since the damaged area doesn't contract with the rest of the heart, blood can start to pool or stagnate, leading to clot formation.

Blood leaking out of a blood vessel.  Blood clots can form when blood leaks out of a blood vessel. This is very beneficial when a person gets a cut or scrape wound, because the clot helps stop further bleeding at the wound site. The clotting mechanism works well following trauma as well. Broken bones, sprains and strains, and nosebleeds all result in bleeding that is controlled by the body's clotting mechanism.

Blood clots causing other medical problems. Sometimes, normal blood clotting can cause medical problems because of its location. For example, if bleeding occurs in the urine from any of a variety of reasons (such as infection, trauma, or tumor) clots may form and prevent the bladder from emptying, causing urinary retention. Clot formation in the uterus may cause pain when the clots are passed through the cervix and can lead to vaginal bleeding, either as part of menstruation or as abnormal vaginal bleeding (menorrhagia, dysmenorrhea).

Dear students, if you are asked, what are the 2 diseases that related to the blood clotting problem, the answer is :

1) Haemophillia

2) Thrombosis

Haemophillia as one of the sex-linked disease

Chances to get haemophillia

Cardiac ventricle from patient who suffered an acute fatal myocardial infarction. Cross-sectional view of coronary artery reveals dark red thrombi (circles).

Enzyme Action - Key & Lock Hypothesis

Fluid Mosaic Model of Plasma Membrane

Movements of Substances Across the Plasma Membrane

Passive Diffusion
Simple diffusion is the movement of a substance from a region of high concentration to a region of low concentration. This is known as moving down the concentration gradient. For example; a pinch of table sugar placed at the bottom of a glass containing water will dissolve in water completely to form a solution of uniform concentration. The sugar is referred to as the solute and water as the solvent. Compounds in a tea bag placed in a cup of hot water diffuse uniformly throughout the water until the colour of the water is brown. You can also use potassium permanganate instead of tea leaves.
Diffusion is faster at high temperatures. It is also faster in gases than in liquids and is slowest in solids.

Passive diffudion

Osmosis
Osmosis is defined as the movement of water molecules from a region of higher concentration of water to a region of lower concentration of water through a semi-permeable membrane.
The plasma membrane is selectively permeable to molecules. Smaller molecules cross the cell membrane more easily than large molecules. Water, carbon dioxide and oxygen cross the membrane easily. Glucose and other large compounds are too large to cross easily.

In osmosis water moves from a region of low solute concentration to a region of high solute concentration. In the diagram above water moves from A to B through the semi-permeable membrane(SP). The glucose molecules in B are too large to pass across the semi-permeable membrane, SP and enter A. Incoming water molecules cause the level of the glucose solution in B to rise while the level of water in A drops.

Osmosis can also be demonstrated using a peeled potato. A hollow is made in a potato; the potato is placed on a petri dish containing distilled water. Sugar crystals are placed in the hollow. Twenty four hours later, it is found that the sugar crystals have formed a solution and that the water level in the petri dish has decreased because water has moved to the hollow by osmosis.

 

Types of Solutions
Most animal cells are isotonic with their environment. This means that the concentrations of the salts inside the cells are equal to the concentrations of the salts in the blood so that there is no net flow of water in either direction. A solution whose osmotic concentration is lower than the salt concentration of the blood or that of the body fluids is referred to as hypotonic. On the other hand, a hypertonic solution has a higher osmotic concentration than that of the body.

If red blood cells are placed in a hypotonic solution, water will diffuse into the red blood cells by osmosis . This water will accumulate in the cells and the cells  will expand in size and finally the cells will burst. On the other hand, if the red blood cells are put in a hypertonic solution, water will diffuse out from the cells to the hypertonic solution, causing the cells to shrink.

 

Facilitated Diffusion
Some molecules are too big to pass through the plasma membrane. In order to cross the membrane, they attach themselves to carrier proteins on the plasma membrane, which will carry them across the membrane, just as a river ferry does when it carries people with their properties across a river. Such carrier proteins transport their substances from a region of high concentration to a region of low concentration. Facilitated diffusion does not require energy.

 





 Active Transport

A cell will sometimes accumulate a certain compound at higher concentration than it is in the surrounding medium. A liver cell, for example, will continue to pick up glucose from the blood even when the concentration of glucose in the liver far exceeds that present in the blood. For human, the sodium- 

    potassium pump is a very good example to explain the active transport. Sodium ions(Na+) are pumped  

    out of te cell and the potassium ions(K+) are pumped into the cell. Energy is needed for this process in  

    the form of ATP.

The movement of charged molecules(ion) in active transport uses both a carrier protein and the energy provided by ATP to pump the molecules against the concentration gradient. Active transport is also important in nerve action, muscle contraction and kidney function. Active transport requires energy.

Do you know about AIDS and HIV?

Definition for AIDS and HIV

AIDS = Acquired Immunodeficiency Defence Syndrome
HIV = Human Immunodeficiency Virus that caused AIDS and attacks the cells of the human's immune system.


The transmission of HIV :
- through placenta(from mother to foetus)
- through body fluids(eg : blood or semen)
- through unprotected sex(with an infected person)
- sharing the needles for injections of drugs or tattoos
- blood transfussion

How to avoid yourself  / Protection steps :

- educational programs

- treating blood products used to destroy the virus

- using condoms

- not having sex(with many partners)

•

Versi Bahasa Melayu tentang HIV dan AIDS :

AIDS bermaksud (Acquired Immuno Deficiency Syndrome) atau Sindrom Kurang Daya Tahan Melawan Penyakit.

A	Acquired : Bermaksud jangkitan yang dipindahkan daripada individu kepada individu lain dan bukan daripada keturunan.
I	Immuno  : Keupayaan semulajadi badan melawan penyakit/jangkitan.
D	Deficiency : Kurang/lemah.
S	Syndrome : Gabungan tanda-tanda dan gejala-gejala

APA ITU HIV
HIV bermaksud Human Immunodeficiency Virus. Sejenis virus daripada kumpulan retrovirus yang menghasilkan jangkitan sepanjang hayat pesakit. Kuman virus ini boleh menyebabkan kerosakan sistem daya tahan tubuh secara perlahan-lahan.

Maklumat Tambahan tentang AIDS & HIV :

Sebagaimana yang anda mungkin telah ketahui AIDS berpunca dari serangan virus yang dipanggil HIV atau Human Immunodeficiency Virus. HIV menyerang sistem daya tahan badan seseorang sehingga ia menjadi lemah dan punah lantas ia tidak berupaya melawan serangan penyakit, sekalipun penyakit-penyakit yang biasanya ringan dan boleh disembuhkan. Seseorang yang telah disahkan dijangkiti HIV dipanggil sebagai positif HIV. Ini tidak semestinya bermakna orang itu menghidap AIDS.

AIDS pula adalah nama yang diberi kepada kumpulan penyakit-penyakit yang dihidapi oleh orang-orang yang positif HIV, akibat sistem daya tahan yang telah lemah. Penyakit-penyakit yang paling biasa adalah radang paru-paru, batuk kering, beberapa jenis barah, jangkitan kulat dan beberapa jenis penyakit kulit seperti kayap. Jangkitan-jangkitan oportunistik ini (yang mengambil kesempatan tehadap sistem daya tahan badan yang telah lemah) mungkin menyerang beberapa tahun selepas seseorang itu dijangkiti HIV.

Individu yang menunjukkan HIV positif digelar Pembawa HIV. Pembawa HIV kelihatan sihat dan dapat menjalankan aktiviti harian seperti orang biasa untuk satu jangkamasa yang panjang (5 - 10 tahun).

Tanda-tanda dan Gejala AIDS :

• Susut berat badan melebihi 10% tanpa sebab tertentu.
• Cirit-birit berlarutan.
• Demam yang berpanjangan.
• Batuk-batuk yang berterusan.
• Penyakit kandisiasis di bahagian mulut.
• Barah kulit (Kaposi's Sarcoma).
• Penyakit herpis simplex(sejenis kayap) merebak dan berulangan.
• Jangkitan Paru- Paru (Pneomocystitis carinii pneumonia)
• Sejenis protozoa boleh menyebabkan kematian 10-30% pesakit jika tidak dirawat. 

Susut berat badan

Radang Otak

Ulser mulut

Seseorang itu tidak dijangkiti HIV melalui :

• Berpegang tangan dan bersalaman.
• Berkongsi kemudahan awam misalnya telefon.
• Berkongsi menggunakan cawan, gelas dan sudu.
• Melalui makanan atau minuman.
• Ciuman/pelukan.
• Gigitan serangga seperti nyamuk dan kutu.
• Pergaulan di sekolah atau di tempat kerja.
• Berkongsi buku (sekolah).
• Berkongsi menggunakan bilik mandi dan tandas.
  
  
  
  
  
  
  
  

Just try to guest the type of immunity for these pictures...(form 5)

Hahaha....!

Picture A

Picture B

Picture C

Picture D

QUESTIONS :

1)  Try to state the type of immunity shown by the diagram(Picture 1 - 4). 

2)  Differentiate between immunity type :- 

     => Picture A and Picture D

     => Picture A and Picture C

    based on the criteria learned.

Happy Trying.... =)

Blood Clotting Mechanism

Human Blood Circulatory System

About Red Blood Cell(Erythrocytes)

• A RBC has a strange shape -- small biconcave disc that is round and flat, sort of like a shallow bowl.
• A RBC has no nucleus. The nucleus is extruded from the cell as it matures.
• A RBC can change shape to an amazing extent, without breaking, as it squeezes single file through the capillaries
• A RBC contains hemoglobin, a molecule specially designed to hold oxygen and carry it to cells that need it. 

The primary function of red blood cells is to transport oxygen from the lungs to the cells of the body. RBCs contain a protein called hemoglobin that actually carries the oxygen. Hemoglobin combines loosely with oxygen in the lungs where the oxygen level is high and then easily releases it in the capillaries where the oxygen level is low. Each molecule of hemoglobin contains four iron atoms. Each iron atom can bind with one molecule of oxygen (which contains two oxygen atoms, called O2) for a total of four oxygen molecules or eight atoms of oxygen for each molecule of hemoglobin. The iron in hemoglobin gives blood its red color.

Red Blood Cell / Erythrocytes

 About White Blood Cell(Leucocytes)

Our blood also contains white blood cells. There are several types of white blood cells. White blood cells are larger than red blood cells and have nuclei. They have different shapes and sizes. White blood cells are located in the lymph nodes and the spleen. Their main function is to produce antibodies that destroy foreign chemicals and pathogenic microorganisms in the blood. They are the “soldiers” of the body that protect it against disease(s).

White Blood Cell / Leucocytes

Lymphocyte among the erythrocytes

Eosinophil among the erythrocytes

About Platelet

Platelets are small fragments of cells formed in the bone marrow. Their function is to clot blood. For example, if you cut your finger accidentally with a knife, blood flows from your finger. The platelets trap red blood cells. The blood changes into a thick substance which is called a blood clot. This stops the bleeding. The clot hardens to form a scab. 

 

 

 Differences between artery and vein

Artherosclerosis, Oedema, Osteoporosis, Arthritis, Diabetes mellitus

What Is Atherosclerosis Heart Disease?

Atherosclerosis (ath-er-o-skler-O-sis) is a disease in which plaque (plak) builds up inside your arteries. Arteries are blood vessels that carry oxygen-rich blood to your heart and other parts of your body.

Plaque is made up of fat, cholesterol, calcium, and other substances found in the blood. Over time, plaque hardens and narrows your arteries, limiting the flow of oxygen-rich blood to your organs and other parts of your body. This can lead to serious problems, including stroke, or even death.

Artherosclerosis formation

What Is Oedema?

Oedema is the medical term for fluid retention in the body.

It occurs when there is a build-up of fluid (mainly water) in the body's tissues, causing swelling to occur in the affected area. As well as swelling or puffiness of the skin, oedema can cause:

• skin discolouration
• fluid-filled areas of skin that temporarily hold the imprint of your finger when pressed (known as pitting oedema)
• aching, tender limbs
• stiff joints
• weight gain or weight loss
• raised blood pressure and pulse rate

Oedema is often a symptom of an underlying condition. It can also be caused by a variety of factors such as high salt intake in the diet or being immobile for long periods of time and of course because of the problems with the lymphatic system of ones.

Oedema patient

What Is Osteoporosis?

Osteoporosis is a disease that weakens bones and makes them susceptible to fracture. Literally translated, osteoporosis means “bone that is porous” (osteo= bone and porosis= porous). This disease affects both men and women; however, 80% of those affected are women. This may be because women generally have smaller bones than men, and because at menopause women lose their estrogen protection, which is a major contributor to bone strength.

Comparison between healthy bone and person with osteoporosis

The most common locations where breaks occur are the hip, spine, and wrist. Fractures due to osteoporosis of the spine usually affect women after the age of 50, while fractures of the hip start later, usually in the 70′s. Not only can these fractures be associated with pain, but also with limitation in movement. The decrease in mobility that can occur leads to further deconditioning, which in turn further weakens muscles and bones. In addition, the constant pain and reduced mobility caused by these fractures can lead to clinical depression.

What Is Arthritis?

 Arthritis is a term that includes a group of disorders that affect your joints and muscles. There are more than 100 diseases that cause pain, stiffness and swelling from the inflammation of a joint or the area around joints. Arthritis symptoms include joint pain, inflammation and limited movement of joints. When a joint is inflamed it may be swollen, tender, warm to the touch or red. The three basic types of arthritis that may cause knee and hip pain: osteoarthritis and inflammatory arthritis (most commonly rheumatoid arthritis), and traumatic arthritis.

Arthritis patient hands's

For most people arthritis pain and inflammation cannot be avoided as the body ages. In fact, most people over the age of 50 show some signs of arthritis. Arthritis can be managed through a combination of medication, exercise, rest, weight-management, nutrition, and, in some cases, surgery. Your doctor can tell if you have arthritis through blood tests and x-rays. He or she will then be able to help you decide on the best treatment for your case.

What Is "Diabetes mellitus"

Diabetes mellitus is a condition in which the pancreas no longer produces sufficient insulin or cells stop responding to the insulin which is produced, so which glucose in the blood cannot be engrossed in to the cells of the body.