2007年1月24日星期三

Analogy of Animal Cell


Animal Cell








Animal cells are in our human bodies as well in animals. There are various kinds of animal cells such as red blood cell, nerve cell and so on. Different cells have different appearances and the figure on the left shows the general form of animal cells






An animal cell normally consists of many organelles, including:

a) Nucleus

b) Cytoplasm

c) Cell membrane(aka Plasna membrane)

d) Endoplasmic reticulum

h) Lysosomes

g) Mitochondria

h) Golgi apparatus

i) Ribosomes

Here I would like to make analogy for some of the parts.


Nucleus




Nucleus is the central part as well as the most important part of a cell. It contains nuleolus, chromatin, nucleoplasm and is surrounded by a porous nuclear envelope. Nucleus controls all the important activities of the cell so we can say that it is just like the headquarter of the whole cell.

-Nucleolus

Nucleolus is in the middle of the nucleus. It is a knot of chromatin and it is the part that manufactures ribosomes(small particles that produces proteins). It is the radical resource of the proteins in the cell.

Ribosomes


Ribosomes are small round structures made by nucleolus. They play a very essential role in the process of synthesising proteins. They can be sorted into two types-ribosomes attached to rough ER and free ribosomes. The ribosomes of the first type are found along rough ER and they produce the basic proteins in it. Free ribosomes are found lying in the cyoplasm. Proteins made by these ribosomes are normally used within the cytoplasm ot the cell. We can say that ribosomes are like manufactorers.

Rough Endoplasmic Reticulum(Rough ER)

Rough endoplasmic reticulum has a rough surface when viewed under the electron microscope. This is because small particles(ribosomes) are attached to its outer surface. Rough ER is involved in the synthesis and transportation as well as sorting of proteins.When proteins are made in rough ER, it will form vesicles to transport the proteins to golgi apparatus. If we compare the nucleus to the headquarter of the cell, the is just like the Ministry of Transportation.

Golgi Apparatus

Golgi Apparatus, also known as Golgi body, is shaped like a disc. It is made up of stacks of flattened spaces surrounded by membranes. Vesicles(small spherical spaces enclosed by a membrane) can be seen fusing with one side of the Golgi apparatus andpinching off from the opposite side all the time. In this way, Golgi apparatus is involved in transport of molecules out of the cell since the molecules are packaged in the vesicles. Another function of is modifing suvstances made by the rough ER. In the animal cell, the Golgi apparatus is like the postal office.

Lysosomes

Lysosomes are spherical organelles that contain digestive enzymes. They are built in the Golgi apparatus. They have the ability to fuse with vacuoles and release enzymes into it. Lysosomes are usually more than one in a cell. They are responsible for digestion of excess or worn organelles, food particles and engulved viruses and bacteria. Therefore they are call "scrap yard" of a cell.


Mitochondria


Mitochondria (plural form of mitochondrion) are small sausage-shaped organelles lying in the cytoplasm. Aerobic respiration, during which food substances are oxidised, occurs in them. Energy released during respiration may be stored as Adenosine Triphosphates(ATP). That's why mitochondria can provide the cell with energy. This energy may be used by the cell to carry out cell activities, for instance, growth and reproduction. Mitochondria are just like the Ministry of Energy in the cell.


Plasma Membrane


Plasma membrane, aka cell surface membrane, is a thin layer that surrounds the cytoplasm of the cell. Unlike cell wall that plant cells have, plasma membrane is not strong enough to support the cell in order to help it have a fixed shape. The plasma membrane is a partially permeable membrane (not neccessarily semi-permeable) so it allows only some substances to cross it. Therefore, the plasma membrane controls substances entering or leaving the cell.

Interesting Biology Facts

The normal core body temperature of a healthy, resting adult human being is stated to be at 98.6 degrees fahrenheit or 37.0 degrees celsius. Though the body temperature measured on an individual can vary, a healthy human body can maintain a fairly consistent body temperature that is around the mark of 37.0 degrees celsius.

The normal range of human body temperature varies due to an individuals metabolism rate, the higher (faster) it is the higher the normal body temperature or the slower the metabolic rate the lower the normal body temperature. Other factors that might affect the body temperature of an individual may be the time of day or the part of the body in which the temperature is measured at. The body temperature is lower in the morning, due to the rest the body received, and higher at night after a day of muscular activity and after food intake.

Body temperature also varies at different parts of the body. Oral temperatures, which are the most convenient type of temperature measurement, is at 37.0 °C. This is the accepted standard temperature for the normal core body temperature. Axillary temperatures are an external measurement taken in the armpit or between two folds of skin on the body. This is the longest and most inaccurate way of measuring body temperature, the normal temperature falls at 97.6 °F or 36.4 °C. Rectal temperatures are an internal measurement taken in the rectum, which fall at 99.6 °F or 37.6 °C. It is the least time consuming and most accurate type of body temperature measurement, being an internal measurement. But it is definitely, by far, not the most comfortable method to measure the body temperature of an individual.


Age Temperature (°F)
0 - 3 month 99.4


3 - 6 month 99.5

6 month - 1 year 99.7

1 - 3 year 99.0

3 - 5 year 98.6
5 - 9 year 98.3

9 - 13 year 98.0

The first systematic measurements of human body temperature were performed by the German physician Carl Wunderlich. In 1861 he measured the temperatures of one million healthy individuals (a sample size that seems too large to be believed). The average value was reported as 37 degrees celsius. When converted this value becomes 98.6 degreed fahrenheit. So what's the problem? Wunderlich's value has only two significant figures while the converted value has three. The last digit (the "point six" at the end) should be regarded with great suspicion. Wunderlich's converted value should really be stated as "ninety eight point something" if one is being honest.