Saturday, April 17, 2010
Try playing & learn at the same time :)
Thursday, April 15, 2010
Sunday, April 11, 2010
Red Blood Cells
Introduction to Red Blood Cells.
Red blood cells are also known as RBCs, red blood corpuscles (an archaic term), haematids, erythroid cells or erythrocytes (from Greek erythros for "red" and kytos for "hollow", with cyte translated as "cell" in modern usage). The capitalized term Red Blood Cells is the proper name in the US for erythrocytes in storage solution used in transfusion medicine.
Information on Red Blood Cells.
Human erythrocytes are produced through a process named erythropoiesis, developing from committed stem cells to mature erythrocytes in about 7 days. When matured, these cells live in blood circulation for about 100 to 120 days. At the end of their lifespan, they become senescent, and are removed from circulation.
-Life cycle (Erythropoiesis)
Erythropoiesis is the development process in which new erythrocytes are produced, through which each cell matures in about 7 days. Through this process erythrocytes are continuously produced in the red bone marrow of large bones, at a rate of about 2 million per second in a healthy adult. (In the embryo, the liver is the main site of red blood cell production.) The production can be stimulated by the hormone erythropoietin (EPO), synthesised by the kidney. Just before and after leaving the bone marrow, the developing cells are known as reticulocytes; these comprise about 1% of circulating red blood cells.
This phase lasts about 100–120 days, during which the erythrocytes are continually moving by the blood flow push (in arteries), pull (in veins) and squeezing through microvessels such as capillaries as they compress against each other in order to move.
Relating to what we have learned- embryonic stem cells
-Artificially grown red blood cells
In 2008 it was reported that human embryonic stem cells had been successfully coaxed into becoming erythrocytes in the lab. The difficult step was to induce the cells to eject their nucleus; this was achieved by growing the cells on stromal cells from the bone marrow. It is hoped that these artificial erythrocytes can eventually be used for blood transfusions.
-How it looks like
-Red Blood Cell in the human blood
- Red Blood Cell in the blood vessel.
The artery that enters any organ divides and thins six to eight times before becoming an arteriole, the capillaries' control valve. Subsequently, the arteriole itself will branch two or three times, reducing its diameter to just 9 microns, and will continue on as a capillary. Some of these capillaries are so small that they cannot let even some large blood cells pass through them. Even red blood cells pass through such capillaries in single file, or else by distorting their shape.
The blood proceeding along the arteries at 1.5 kilometers an hour (0.93 miles per hour) slows down by a thousandth of that rate when it enters the capillaries. Every region of the body has been penetrated by an extraordinarily wide ranging network of capillaries. The capillaries in just one single person could stretch from one end of the USA to the other.109 This incomparable mechanism is brought into being to nourish all the cells in the body. In fact, a cell can be no further than 20 to 30 microns from a capillary—a distance of 0.02 millimeters (0.0007874 inch), which is sufficient to grasp the scale of this magnificent network that visits 100 trillion cells.
How does waste from the red blood cell goes into the lungs and how does oxygen molecules enters the red blood cell from the alveoli (tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place)
-Function of Red Blood Cells
Red blood cells (also referred to as erythrocytes) are the most common type of blood cell and the vertebrate organism's principal means of delivering oxygen (O2) to the body tissues via the blood flow through the circulatory system. They take up oxygen in the lungs or gills and release it while squeezing through the body's capillaries.
-What are the organelles found in the cell?
The organelles found in red blood cells include a plasma membrane and the cells' cytoplasm is rich in hemoglobin, an iron-containing biomolecule that can bind oxygen and is responsible for the blood's red color.
green = heme groups
red & blue = protein subunits
-List the structural features of the cell.
They are biconcave discs, having a depressed center on both sides. These depressed centers allow the cells to have more cell membrane surface which can be exposed to diffusing oxygen while transiting the lungs. This structure also allows them to be more flexible with the ability to twist and bend through the blood vessels.
-What are the functions of these organelles?
Hemoglobin facilitates transportation of oxygen and the plasma membrane keeps the hemoglobin in the cell.
-Why are these functions of the organelles important to the living cell?
Hemoglobin helps in transportation in oxygen so without hemoglobin, the cell will not carry oxygen so it would be useless and die. The person would also die.
Plasma membrane keeps the hemoglobin inside the cell if not it would be all round our blood.
-Diseases involving the red blood cells
- Anemias (or anaemias) are diseases characterized by low oxygen transport capacity of the blood, because of low red cell count or some abnormality of the red blood cells or the hemoglobin.
- Iron deficiency anemia is the most common anemia; it occurs when the dietary intake or absorption of iron is insufficient, and hemoglobin, which contains iron, cannot be formed
- Sickle-cell disease is a genetic disease that results in abnormal hemoglobin molecules. When these release their oxygen load in the tissues, they become insoluble, leading to mis-shaped red blood cells. These sickle shaped red cells are rigid and cause blood vessel blockage, pain, strokes, and other tissue damage.
Affected by Sickle-cell disease, red blood cells alter shape and threaten to damage internal organs.
- Thalassemia is a genetic disease that results in the production of an abnormal ratio of hemoglobin subunits.
- Spherocytosis is a genetic disease that causes a defect in the red blood cell's cytoskeleton, causing the red blood cells to be small, sphere-shaped, and fragile instead of donut-shaped and flexible.
- Pernicious anemia is an autoimmune disease wherein the body lacks intrinsic factor, required to absorb vitamin B12 from food. Vitamin B12 is needed for the production of hemoglobin.
- Aplastic anemia is caused by the inability of the bone marrow to produce blood cells.
- Pure red cell aplasia is caused by the inability of the bone marrow to produce only red blood cells.Hemolysis is the general term for excessive breakdown of red blood cells. It can have several causes and can result in hemolytic anemia.
- Hemolysis is the general term for excessive breakdown of red blood cells. It can have several causes and can result in hemolytic anemia.
- The malaria parasite spends part of its life-cycle in red blood cells, feeds on their hemoglobin and then breaks them apart, causing fever. Both sickle-cell disease and thalassemia are more common in malaria areas, because these mutations convey some protection against the parasite.
- Polycythemias (or erythrocytoses) are diseases characterized by a surplus of red blood cells. The increased viscosity of the blood can cause a number of symptoms.
- In polycythemia vera the increased number of red blood cells results from an abnormality in the bone marrow.
- Hemolytic transfusion reaction is the destruction of donated red blood cells after a transfusion, mediated by host antibodies, often as a result of a blood type mismatch.
- Some other diseases have been removed as it is too difficult to understand. Those who are interested to know the hard ones can go to
Information: http://web.buddyproject.org/web019/web019/blood.html and
Picture (Capillaries drawn):
Definition of alveoli: New Oxford American Dictionary.
Hemoglobin diagram: http://en.wikipedia.org/wiki/File:1GZX_Haemoglobin.png
Most information obtained from http://en.wikipedia.org/
Christopher, Carisa, Yi Lin, Jaime, Pei Shan, Priyanka
Thursday, April 8, 2010
Red blood cells are also called erythrocytes.
Firstly there are three parts in the cell that contain organelles. The nucleus, the cytoplasm and the surface. In the nucleus there are chromosomes, a nuclear membrane and a nucleolus. In the cytoplasm there are centrioles, chloroplast (plant cell), cytoskeleton, endoplasmic reticulum, golgi apparatus, lyosome, mitochondria, ribosomes and vacuoles. In the surface there are cell wall (plant cell) and cell membrane (plasma membrane).
There are other parts of organelles
It has a regular shape due to the cell wall and it also has a rectangular shape with many different looking and types of organelles.
The nucleus is the control center of the cell that dictates what all of the other organelles do. The nucleus also stores the DNA.The endoplasmic reticulum (ER) is where most chemical reactions take place. The cell makes lipids and other chemicals, and it sometimes has ribosomes attached.Ribosomes are the only organelle that every cell has, including bacteria. They take information from the DNA and use it to make proteins.The golgi apparatus is essential in packaging different products from the ER and the ribosomes into their final form. If it is a product that needs to be sent to other cells, the golgi apparatus packs them and sends them out.Mitochondria are often referred to as the powerhouses of the cell. This is because they take in sugar and create ATP, the type of energy your cell needs to function.The plasma membrane, or cell membrane, is not just the covering of the cell. It also plays a vital role in getting nutrients into the cell and sending waste products out.Chromosomes are normally in the form of chromatin. It contains genetic information. It is also composed of DNA.Moreover it is thickened for cellular division.There is a set number per species (i.e. 23 pairs for human)
They each have a specific function that helps the cell perform its function.
A Report by: Karan Sarat, Yuzhe Ng, Zheng Jie, Lionel Lim, Darryl Lam & Jasper Phang
(a) What are the Organelles Found In The Cell?
They are the: nucleus, cytoplasm, plasma membrane, cell wall and vacuole. As you can see the root hair cell has fewer organelles than most other cells.
(b) List The Structural Features Of The Cell?
They have in comparison to other cell a large surface area which helps them collect water. They are found near the tip of the roots and appear like hairs. The whole structure is quite delicate. It can only survive for a few days and don't properly develop into a proper hair.
(c) What Are The Functions Of These Organelles?
Nucleus: the nucleus controls all the activities taking place in the cell and it is also responsible for cell division.
Cytoplasm: The cytoplasm plays a mechanical role, i.e. (example) to maintain the shape, the consistency of the cell and to provide suspension to the organelles.
Plasma membrane/cell membrane: The plasma membrane will allow certain substances to cross it but not others
Cell wall: A major function of the cell wall is to act as a pressure vessel, preventing over-expansion when water enters the cell
Vacuole: produces turgor pressure against cell wall for support
- stores water and various chemicals
- may store insoluble wastes
(d)Why are these functions of the organelles important to the living cell?
Nucleus: The nucleus:It contains DNA,in other words,deoxyribose acid; it is therefore the 'brain' of the cell because DNA contains "instructions" needed for the cell to reproduce and do other functions.Cells without a nucleus can survive for short periods,but cannot survive for long-term periods
Cell membrane: The cell membrane is like the skin of the cell.It also gives the cell its shape,and ,like a skin,prevents certain substance from entering it.
Cytoplasm: Cytoplasm can be said as the material that lies within the cell membrane,contains a lot of water, and the other organelles of the cells. It provides a platform upon which they can operate within the cell.So,without the cytoplasm,the cell will dry up and the organelles cannot operate.
The cell wall provides the most significant difference between plant cells and other cells.It is rigid and gives the plant a definite shape. The cell wall is the reason for the difference between plant and animal cell functions. Because the plant has evolved this rigid structure, they have lost the opportunity to develop nervous systems, immune systems, and most importantly, mobility.
Plant cells use their vacuoles for storing nutrients,and function as a storage organelle. In a sense, the vacuole can be regarded as equivalent to the extra cellular space of animals. The simple space-filling function of the vacuole is of great importance to plants, which capture energy from the sun rather than move to capture food.
Question 1: What are the organelles found in the muscle cell?
Answer: This includes the cell membrane which is not stated down here*
6. Golgi Apparatus
9. Secretory Vesicle
10. Larger Mitochondria
11. Small, numerous vacuoles
12. Rough Endoplasmic Reticulum
13. Smooth Endoplasmic Reticulum
15. Cytoskeleton (Micro-tubules & [Micro]-Intermediate filaments)
Question 2: List the structural features of the cell.
Question 3: What are the functions of these organelles?
Question 4: Why are these functions of the organelles important to the living cell?
The answer to all the questions:
-The nucleus is the most obvious organelle in any eukaryotic cell. It is enclosed in a double membrane and communicates with the surrounding cytosol via numerous nuclear pores. Within the nucleus is the DNA responsible for providing the cell with its unique characteristics. The DNA is similar in every cell of the body, but depending on the specific cell type, some genes may be turned on or off - that's why a liver cell is different from a muscle cell, and a muscle cell is different from a fat cell. When a cell is dividing, the nuclear chromatin (DNA and surrounding protein) condenses into chromosomes that are easily seen by microscopy.
-The prominent structure in the nucleus is the nucleolus. The nucleolus produces ribosomes, which move out of the nucleus and take positions on the rough endoplasmic reticulum where they are critical in protein synthesis.
-The cytosol is the "soup" within which all the other cell organelles reside and where most of the cellular metabolism occurs. Though mostly water, the cytosol is full of proteins that control cell metabolism including signal transduction pathways, glycolysis, intracellular receptors, and transcription factors. 4. Cytoplasm:
-This is a collective term for the cytosol plus the organelles suspended within the cytosol.
-The centrosome, or MICROTUBULE ORGANIZING CENTER (MTOC), is an area in the cell where microtubules are produced. Plant and animal cell centrosomes play similar roles in cell division, and both include collections of microtubules, but the plant cell centrosome is simpler and does not have centrioles.
During animal cell division, the centrioles replicate (make new copies) and the centrosome divides. The result is two centrosomes, each with its own pair of centrioles. The two centrosomes move to opposite ends of the nucleus, and from each centrosome, microtubules grow into a "spindle" which is responsible for separating replicated chromosomes into the two daughter cells. The explanatory for centrioles is shown below.
6. Centriole (animal cells only):
-Each centriole is a ring of nine groups of fused microtubules. There are three microtubules in each group. Microtubules (and centrioles) are part of the cytoskeleton. In the complete animal cell centrosome, the two centrioles are arranged such that one is perpendicular to the other.
7. Golgi apparatus:
-The Golgi apparatus is a membrane-bound structure with a single membrane. It is actually a stack of membrane-bound vesicles that are important in packaging macromolecules for transport elsewhere in the cell. The stack of larger vesicles is surrounded by numerous smaller vesicles containing those packaged macromolecules. The enzymatic or hormonal contents of lysosomes, peroxisomes and secretory vesicles are packaged in membrane-bound vesicles at the periphery of the Golgi apparatus.
-Lysosomes contain hydrolytic enzymes necessary for intracellular digestion. They are common in animal cells, but rare in plant cells. Hydrolytic enzymes of plant cells are more often found in the vacuole.
-Peroxisomes are membrane-bound packets of oxidative enzymes. In plant cells, peroxisomes play a variety of roles including converting fatty acids to sugar and assisting chloroplasts in photorespiration. In animal cells, peroxisomes protect the cell from its own production of toxic hydrogen peroxide. As an example, white blood cells produce hydrogen peroxide to kill bacteria. The oxidative enzymes in peroxisomes break down the hydrogen peroxide into water and oxygen.
10. Secretory Vesicle:
-Cell secretions - e.g. hormones, neurotransmitters - are packaged in secretory vesicles at the Golgi apparatus. The secretory vesicles are then transported to the cell surface for release.
-Mitochondria provide the energy a cell needs to move, divide, produce secretory products, contract - in short, they are the power centers of the cell. They are about the size of bacteria but may have different shapes depending on the cell type. Mitochondria are membrane-bound organelles, and like the nucleus have a double membrane. The outer membrane is fairly smooth. But the inner membrane is highly convoluted, forming folds (cristae) as seen in the cross-section, above. The cristae greatly increase the inner membrane's surface area. It is on these cristae that food (sugar) is combined with oxygen to produce ATP - the primary energy source for the cell.
-A vacuole is a membrane-bound sac that plays roles in intracellular digestion and the release of cellular waste products. In animal cells, vacuoles are generally small.
13: Smooth Endoplasmic Reticulum:
-Throughout the eukaryotic cell, especially those responsible for the production of hormones and other secretory products, is a vast network of membrane-bound vesicles and tubules called the endoplasmic reticulum, or ER for short. The ER is a continuation of the outer nuclear membrane and its varied functions suggest the complexity of the eukaryotic cell. The smooth endoplasmic reticulum is so named because it appears smooth by electron microscopy. Smooth ER plays different functions depending on the specific cell type including lipid and steroid hormone synthesis, breakdown of lipid-soluble toxins in liver cells, and control of calcium release in muscle cell contraction.
14. Rough Endoplasmic Reticulum:
-Rough endoplasmic reticulum appears "pebbled" by electron microscopy due to the presence of numerous ribosomes on its surface. Proteins synthesized on these ribosomes collect in the endoplasmic reticulum for transport throughout the cell.
-Ribosomes are packets of RNA and protein that play a crucial role in both prokaryotic and eukaryotic cells. They are the site of protein synthesis. Each ribosome comprises two parts, a large subunit and a small subunit. Messenger RNA from the cell nucleus is moved systematically along the ribosome where transfer RNA adds individual amino acid molecules to the lengthening protein chain.
-As its name implies, the cytoskeleton helps to maintain cell shape. But the primary importance of the cytoskeleton is in cell motility. The internal movement of cell organelles, as well as cell locomotion and muscle fiber contraction could not take place without the cytoskeleton. The cytoskeleton is an organized network of three primary protein filaments:
- microtubules - actin filaments (microfilaments) - intermediate fibers
Done by: Benz Kew(Group leader)
With the help of other group members: Su En, Shamemi, Teoh Yun, Lincoln & Hao En
Note the unique characteristics of each kingdom
1. Kingdom Monera
2. Kingdom Protista
3. Kingdom Fungi
4. Kingdom Plantae
5. Kingdom Animalia
Monday, April 5, 2010
Sunday, April 4, 2010
Saturday, April 3, 2010
Area of focus:
a. What are the organelles found in the cell?
b. List the structural features of the cell.
c. What are the functions of these organelles?
d. Why are these functions of the organelles important to the living cell?
CELLS alive! Interactive Animal and Plant Cell:http://www.cellsalive.com/cells/cell_model.htm
2. PurposeGames.com is a web site for educational learning and having fun at the same time.
Interactive Game on Cell Organelles:http://www.purposegames.com/game/153