Cells, Etc. - Writers Writing - http://maxpages.com/fanficsnstuff/Cell

Prokaryotic Cells

Simpler cellular organization with no nucleus or other membrane bound organelles. In these cells, the DNA floats freely within the cytoplasm. Examples of Prokaryotic organisms are bacteria such as E. Coli and Salmonella.

Eukaryotic Cells

More complex cellular organization; examples of Eukaryotic organisms are mammals, reptiles, humans... you get the point right? :P

1. Nucleus- DNA/chromosomes, controls cellular activities via genes.
2. Nucleolus- The site for ribosome synthesis; located within the nucleus.
3. Rough Endoplasmic Reticulum (Rough E.R.)- with ribosomes; involved in protein synthesis.
4. Smooth Endoplasmic Reticulum- without ribosomes, involved primarily in lipid synthesis.
5. Golgi Apparatus- packaging center for molecules; cellular digestion.
6. Lysosome- contains hydrolytic enzymes for intra-cellular degredation.
7. Peroxisome- involved in several metabolic processes, some of which create hydrogen peroxide as a biproduct; this is in turn changed to water.
8. Chloroplast (only in plant cells)- site of photosynthesis. The chloroplast is made of stacked grana and thylakoids, the site of chlorophyll and photosynthesis.
9. Chromoplast- non-green pigments; also known as accesory pigments that protect the chloroplast from high light intensities.
10. Leukoplast- stores starch.
11. Mitochondria- ATP production; the electron transport chain of cellular respiration occurs here on the inner membrane.
12. Vacoule - Found in both plants and animals; in plants, it is very large; in both, it serves for storage purposes.
A. Cell (Plasma Membrane)- Composed of fluid-like phospholipid bilayer, proteins, cholestorol and glycoproteins. This is common in both eukaryotic and prokaryotic cells.

B. Cell Wall- In plant cells the cell wall covers the cell membrane and provides stronger protection to the cell. It is composed of carbohydrate cellulose or chitin, or a carbohydrate derivitive (peptidoglycan).

C. Cytoplasm- Material outside of the nucleus in which the cell organelles float.
1. Site for metabolic activity.
2. Cyotosol- Solutions with dissolved substances such as glucose, carbon dioxide, oxygen, etc.
3. Organelles- Membrane bound subunits of cells with specialized functions.

D. Cytoskeleton- Supportive metabolic structure composed of microtubules and microfiliments; these are arranged in 9/2 rings, with 9 microtubules surrounding 2 inner microtubules. The cytoskeleton also plays an important part in mitosis/meiosis.

E. Mitochondria- this is basically the energy factory of the cell; it produces the ATP needed for transportation in and out of the cell; this is where the electron transport chain of cellular respiration occurs.

F. Nucleus- holds the DNA within chromosomes nesecarry for reproduction (and life as we know it) to occur; also within the nucleus is the nucleolus.

Organisms must use the sun's energy (directly or indirectly) to become and remain in an organized state.

A. Metabolism- series of chemical reactions involved in storing (anabolism) or releasing (catobolism) energy.

B. Enzymes- Biological Catalyst. Facilitates metabolic chemical reactions by speeding up rates and lowering heat requirements, including the activation energy barrier.

C. Adenosine Triphosphate (ATP)- a high-energy molecule. Energy stored in ATP is released by breaking phosphate to phosphate bonds and creating adenosine diphosphate (ADP) or adenosine monophosphate (AMP). ATP is recycled by adding back phosphate groups using energy from the sun.

Photosynthesis

Sunlight or radiant energy is captured by chlorophyll and carotenoid photopigm,ents (found in cytoplasm in prokaryotes and choloroplasts in eukaryotes) in two main steps:

A. Light dependant reactions (light reactions)- the captures light energy is transferred to electrons that come from water. Oxygen is a by-product.

B. Light independent reactions (dark reactions)- energized electrons are transferred to carbon dioxide (reduction reactions) to form glucose (in the Calvin-Benson cycle).

Cell Respiration

Highly energized electrons stored temporarily in glucose are removed (oxidation reactions) in a step wise fashion to maximize energy capture in each step:

A. Glycolysis- Anaerobic process in cytoplasm in which glucose, a six-carbon compound, is oxidized to two pryuvates, which are both three carbon chains, to two pryuvates, which are both three carbon chains.

B. Krebs Cycle- Aerobic process that oxidizes pyruvates to carbon dioxide; occurs in nine steps, where some products that will be further used are NAD+ and FADH2.

C. Chemiosmotic phosphorylation- the energized electrons released during the previous steps are used to concentrate hydrogen ions in one area (of the cell membrane in prokaryotes; of the mitochondrion in eukaryotes) to create a chemical gradient between positively and negatively charged ions (ie. battery). The potential energy resulting from this osmotic gradient is used to resynthesize ATP from ADP and AMP. After electrons have been used, they must be transferred to oxygen.

Source: BarCharts, Inc. Biology: The Basic Principles of Biology.

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Page Updated Tue Dec 16, 2003 10:45am EST