a. The structure of a cell
There are two types of cells that we want to talk about, the plant cell and animal cell.
Animal cell
-cytoplasm
-a nucleus
-vacuoles
-a cell membrane
In the picture beside, there are extra cells, lyosome and mitochondrion. But, I was not discussing about that if you want to know more about the structure of an animal cell you can click the link: http://www.cartage.org.lb/en/themes/sciences/zoology/animalphysiology/anatomy/animalcellstructure/animalcellstructure.htm.
Plant cell
-cytoplasm
-a nucleus
-a vacuole
-a cell membrane
-chloroplasts
-a cell wall
Just like the first picture, there are different cells that I was not discussing, mitochondria and endoplasmic reticulum, If you want to know more about the structure of a plant cell I've prepared you another link: http://www.enchantedlearning.com/subjects/plants/cell/.
Now, I want to tell you the functions of cells in plant and animal.
Cytoplasm
Cytoplasm is basically the substance that fills the cell. It is a jelly-like material that is eighty percent water and usually clear in color. It is more like a viscous (thick) gel than a watery substance, but it liquefies when shaken or stirred.
Vacuole
Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain cases they may contain solids which have been engulfed.
Nucleus
The function of the nucleus is to maintain the integrity of these genes
and to control the activities of the cell by regulating gene expression — the nucleus is, therefore, the control center of the cell.
Cell Membrane
It basically protects the cell from outside forces. It consists of the lipid bilayer with embedded proteins.
Chloroplasts
Chloroplasts are organelles found in plant cells and other eukaryotic organisms that conduct photosynthesis. Chloroplasts capture light energy, store it in the energy storage molecules ATP and NADPH and use it in the process called photosynthesis to make organic molecules and free oxygen from carbon dioxide and water.Cell Wall
The cell wall is the tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, in addition to acting as a filtering mechanism. A major function of the cell wall is to act as a pressure vessel, preventing over-expansion when water enters the cell.
b. Cell division
Cells are like organisms, as they grow, they multiply. Cells also multiply to replace old cells that die. This process takes place in organisms all the time. there are two types of organisms that I want to discuss, multicellular organism and unicellular organism.
Multicellular Organisms
Multicellular organisms are organisms that consist of more than one cell, in contrast to single-celled organisms. To form a multicellular organism, these cells need to identify and attach to the other cells.
Unicellullar Organisms
A unicellular organism, also known as a single-celled organism, is an organism that consists of only one cell, in contrast to a multicellular organism that consists of multiple cells.
Cells multiply by dividing themselves. The nucleus and cytoplasmof one cell divide to produce two cells. The new cells produced
are identical to the original cell.
The process can be repeated. The two new cells can later divide to form four cells.
Cells also die, they do not live forever. our skin cells can live up to three weeks, while cells lining our intestines are replaced by new cells every three days. Some cells also divide to help repair damaged parts of our body.
The examples of unicellular organisms are bacteria and paramecia, they multiply by dividing themselves. The picture on the left side shows a cell division in a paramecium.there are more common unicellular organisms example such as, algae, amoeba and fungi, but were not discussing about that.
There is one more example of unicellular organism called yeast. Yeast multiple by a special way called budding . During the process of budding, a small bad grows from a yeast cell. The bud then increases in size and breaks away from the original yeast cell.
c. From cell to organism
Human beings
All the organs in our body are made up of cells. Let us take a look how cells form an organism such as a human being.
Cell->Tissue->Organ->System->Organism
Cell
The cell is the basic structural and functional unit of all known living organisms.
Tissue
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of similar cells and from the same origin, that together carry out a specific function.
Organ
In biology, an organ is a collection of tissues joined in a structural unit to serve a common function.
There is a "main" tissue, parenchyma, and "sporadic" tissues, stroma. The main tissue is the one that is unique for the specific organ.
System
In biology, a biological system (or organ system or body system) is a group of organs that work together to perform a certain task.
Organism
In biology, an organism is any contiguous living system (such as animal, fungus, micro-organism, or plant). Our body is made up of many systems working together.
Plants
Plants are organised like human beings. They have cells , tissues, organs and systems. However, there are only two systems in plants - the shoot system and the root system.
Cell->Tissue->Organ->System->Organism
Cell
Plant cells are eukaryotic cells that differ in several key respects from the cells of other eukaryotic organisms.
Tissue
The major classes of cells differentiate from undifferentiated meristematic cells (analogous to the stem cells of animals) to form the tissue structures of roots, stems, leaves, flowers, and reproductive structures.
Organ
In biology, an organ is a collection of tissues joined in a structural unit to serve a common function.
System
The shoot system of a plant is formed when the organs - leaves, stems, flowers and fruits - work together.
Organism
A plant is made up of the shoot system and the root system working together.
d. Energy in cells
Life is an energy intensive process. It takes energy to operate muscles, extract wastes, make new cells, heal wounds, even to think. It’s in an organism’s cells where all this energy is spent. In some cells, as much as half of a cell’s energy output is used to transfer molecules across the cell membrane, a process called ‘active transport.’
Cell movements require energy and thousands of energy-hungry chemical reactions go on in every living cell, every second, every day. The kind of energy cells use is chemical bond energy, the shared electrons that holds atoms together in molecules. Cells got energy by: Nutrients enter the cell through the cell membrane.
The cell converts the nutrients into the energy. Oxygen is needed for this process known as respiration. This energy is used by the cell for cell division, growth and repair.
the amount of energy a cell needs depends on its function.
I have an experiment of putting 2 flask 30 ml of hot water each. Then, on flask a, we put 1 tablespoon of yeast and on flask b, we put 1 tablespoon of yeast and 1 tablespoon of sugar. we put the sugar, yeast and water through the funnel. And put balloons on top of each flask. We set a stopwatch and measure the length of the balloon several times. The result is, flask b has wider balloon length it is because a yeast need energy to grow and multiply and in flask b the sugar is the energy. The conditions necessary for yeast to grow and divide are heat, water and sugar. Here are the pictures:
e.Information in cells
When organisms reproduce, they pass on certain characteristics or genetic traits to their young. These characteristic are contained as genes and are stored in the thread-like structures in the cell nucleus.
I've posted a video about cell division, you can click it if you wish to know more about cell division.
