2010年10月4日月曜日

Ch.4 A Tour of the Cell

WHAT ARE THE PROBLEMS WITH SPERM MOTILITY?
Sperm motility is a problem. For example, his sperm shape is different from the other sperm shape, he has too much sperm, and how his sperms move is not right. When he as a fertility problem, it can cause a severe loss of self esteem, not to mention the frustration involved with not being able to have a baby. Knowing what can cause low sperm motility and other fertility problems for men can, however, help a man to know how to proceed with addressing the problem.

WHY DO NOT  ANIMALS PHOTOSYNTHESIZE?
Because if animals do photosynthesize, food chain will not work. Also animals can get energy from eating other organisms. That is why animals don't have cell wall so we can move easily. Plants cannot move, so they need to photosynthesize to get energy. Also animals need O2 to breathe. If we could photosynthesize, we will need CO2, which we produce now, but not use. There would be no O2 for animals to breathe. That is why I think that animals don't photosynthesize, because we don't need to.

WHAT HAPPENS IF A CELL GETS DISEASE?
There are some cell diseases. I am going to answer one of them, Leukemia. Leukemia is a disease that number of white blood corpuscle increases more than number of red blood corpuscle. The numbers those two blood cells will be unbalanced. Thus losing hair, having a fever, out of breath, feeling of less blood, and etc. It is usually caused from smoking, and some how.  There are many cell diseases like that. The reasons why those happen are mostly from genetic.



SUMMARY:
     Robert Hooke first observed cells in 1665. As we know about cells, we developed the microscopes. We have basically 4 kinds of microscopes. Light microscope, works by passing visible light through a specimen which can magnify objects about 1000 times, Electron microscope, uses a beam of electrons, which can magnify up to 100,000 times, Scanning Electron microscope, which can show a specimen with 3D, and Transmission Electron microscope, used to study the details of internal cell structure. Cell theory states that al living things are composed of cells and that all cells come from other cells.
     There are two types of cells. Prokaryotic cells, and eukaryotic cells. Prokaryotic cells compose bacteria and archaea, and eukaryotic cells compose other forms of life. The surface area of a cell is important for carrying out the cell's functions. Cells are all bounded by a plasma membrane. All have chromosomes carrying genes made of DNA. And they all contain ribosomes, tiny structures that make proteins according to instructions from the genes. The entire region between the nucleus and the plasma membrane is called the cytoplasm. There are various organelles in an eukaryotic cell. There are four different life processes in eukaryotic cells; 1) manufacturing 2) breakdown of molecules 3) energy processing, 4) structural support, movement, and communication.
     Phospholipids are the main components of biological membranes. It has two distinct regions; a negatively charged and thus hydrophilic phosphate group and two non-polar, hydrophobic fatty acid tails. Non-polar molecules such as O2 can easily pass through its hydrophobic interior. Some of these proteins form channels that allow specific ions and other hydrophilic molecules to cross the membrane.
     During a cell reproduction, as a cell prepares to divide, the DNA is copied and the thin chromatin fibers coil up. Nuclear envelope controls the flow of materials into and out of the nucleus. It connects with ER. Ribosomes are found in two locations. Free ribosomes are in the fluid of the cytoplasm, while bound ribosomes are attached to the outside of ER or nuclear envelope. Smooth ER is important in the synthesis of lipids. It is a detoxification in liver cells and also a calcium ion storage. Rough ER is a synthesis of membrane lipids and proteins, secretory proteins, and hydrolytic enzymes. It is also a formation of transport vesicles. Cell's structure and activities are organized by internal skeleton. Cytoskeleton supports the cell structure and cell motility. Microfilaments form a 3D network just inside the plasma membrane that helps support the cell's shape. Intermediate filaments serve mainly to reinforce cell shape and to anchor certain organelles. It holds nucleus as well. Microtubules are readily disassembled in a reverse manner and the tubulin subunits can then be reused in the cell. They can grow out from a centrosome. They shape and support the cell and also act as tracks along which organelles equipped with motor proteins can move. Cells have an ability to move. They have cilia which sweep.
     Three types of cell junctions are found in animal tissues. At tight junctions, the membranes of neighboring cells are every tightly pressed against each other, knit together by proteins. Anchoring junctions function like rivets, fastening cells together into strong sheets. Gap junctions are channels that allow small molecules to flow through protein-lined pores between neighboring cells.

KEY TERMS:
-Nucleoid: the region where the DNA of a prokaryotic cells is coiled
-Flagella: longer projections that help attach prokaryotes to surfaces
-Cellular metabolism: many of the chemical activities of cells that occur within organelles
-Chromatin: a material that makes up eukaryotic chromosomes
-Vesicles: the transfer of membrane segments that connect physically the membranes such as endo-membrane system
-Golgi apparatus: a structure of a cell that packages substances and send them out
-Lysosome: a digestive system of a cell
-Vacuole: digestion; storage of chemicals; cell enlargement; controls water balance
-Endosymbiosis: hypothesis of it proposes that mitochondria and chloroplasts were formerly small prokaryotes that began living within larger cells
-Granum: a stack for thylakoids


Animal-Cell.jpg

This is a diagram of a cell. As you can see, there are various structures in a cell. Those structures are grouped in four types as I mentioned in summary.
1) Manufacturing
-Nucleus: DNA synthesis; RNA synthesis. Nucleolus is inside.
-Ribosomes: protein synthesis. 
-Smooth ER: produces lipid. Detoxification in liver cells. Calcium ion storage.
-Rough ER: produces mainly protein. Has ribosomes attached. 

2) Breakdown
-Lysosomes: only in animal cells. Digestive system of cells. Recycles food.
-Vacuoles: Digestion. Storage of chemicals, cell enlargement, water balance.
-Peroxisomes: Diverse metabolic processes with breakdown of H2O2 by-product.

3) Energy Processing
-Mitochondria: makes chemical energy. 
-Chloroplasts: only in plant cells and some protists. produces light energy to chemical energy sugars

4) Support, Movement, and Communication Between Cells
-Cytoskeleton: including cilia, flagella, and centrioles in animal cells. maintains cell shape. anchorage for organelles: movement of organelles within cells and also cell itself. mechanical transmission of signals from exterior of cell to interior. communication between cells.
-Extracellular Matrix: only in animal cells. Binding of cells in tissues; surface protections; regulation of cellular activities.
-Cell junctions: communication between cells. binding of cells in tissues
-Cell walls: only in plants, fungi, and some protists. maintains the cell shape and skeletal support. protects surface. binding of cells in tissues.


5 Facts:
1) There are many structures in a cell. They all perform the important functions for a cell.
2) There are two different kinds of cell. Prokaryotic, and Eukaryotic. Prokaryotic cells are simpler than Eukaryotic.
3) Manufacturing, breaking down of molecules, energy processing, and structural support, movement, and communication are the main life process for eukaryotic cells.
4) Animal cells have lysosome and they do not have cell wall. Not having cell walls make it easier for animals to move. They have plasma membrane instead.
5) Plant cells have chloroplast, and cell wall. 



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