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 Biology II ( Assignment ) July 16,2010

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PostSubject: Biology II ( Assignment ) July 16,2010   Sat Jul 17, 2010 8:32 pm

1. Draw And Label The Parts Of A Prokaryotic Cell


2. Draw And Label The Parts Of Cell Membrane/Plasma Membrane.



3. Explain The Fluid Mosaic Model Of Cell Membrane


Fluid Mosaic Model

According to the fluid mosaic model of S. J. Singer and Garth Nicolson 1972, the biological membranes can be considered as a two-dimensional liquid where all lipid and protein molecules diffuse more or less easily. This picture may be valid in the space scale of 10 nm. However, the plasma membranes contain different structures or domains that can be classified as (a) protein-protein complexes; (b) lipid rafts, (c) pickets and fences formed by the actin-based cytoskeleton; and (d) large stable structures, such as synapses or desmosomes.

4. Differentiate Diffusion From Osmosis.


Diffusion


Diffusion refers to the process by which molecules intermingle as a result of their kinetic energy of random motion. Consider two containers of gas A and B separated by a partition. The molecules of both gases are in constant motion and make numerous collisions with the partition. If the partition is removed as in the lower illustration, the gases will mix because of the random velocities of their molecules. In time a uniform mixture of A and B molecules will be produced in the container.

The tendency toward diffusion is very strong even at room temperature because of the high molecular velocities associated with the thermal energy of the particles.



Osmosis

If two solutions of different concentration are separated by a semi-permeable membrane which is permeable to to the smaller solvent molecules but not to the larger solute molecules, then the solvent will tend to diffuse across the membrane from the less concentrated to the more concentrated solution. This process is called osmosis.

Osmosis is of great importance in biological processes where the solvent is water. The transport of water and other molecules across biological membranes is essential to many processes in living organisms. The energy which drives the process is usually discussed in terms of osmotic pressure.



5. Define The Following Terms:

Isotonic

1. Having equal tension.

2. Pertains to a muscular contraction in which the muscle remains to be in a relatively constant tension while its length changes, as in isotonic muscle.

3. Isoosmotic, i.e. having the same (or equal) osmotic pressure and same water potential since the two solutions have an equal concentration of water molecules.

4. Pertaining to a solution that has the same tonicity as some other solution with which it is compared. For example, blood serum is isotonic to a physiologic salt solution. Solutions that have same tonicity will result in no net flow of water across the cell membrane.


Hypotonic

1. having a lesser degree of tone or tension, as in a ‘hypotonic muscle’

2. having a lesser osmotic pressure in a fluid compared to another fluid, as in a ‘hypotonic solution’ – compare hypertonic, isotonic

3. refers to a solution with a comparatively lower concentration of solutes compared to another


Hypertonic

Having a greater degree of tone or tension.

Having a higher osmotic pressure in a fluid relative to another fluid.

Of or pertaining to a solution (e.g. extracelllular fluid) with higher solute concentration compared with another. (see: hypotonic, isotonic). For example, if the extracellular fluid has greater amounts of solutes than the cytoplasm, the extracellular fluid is said to be hypertonic.

Plasmolysis

The shrinking of protoplasm away from the cell wall of a plant or bacterium due to water loss from osmosis, thereby resulting in gaps between the cell wall and cell membrane.

Cytolysis

(1) Osmotic lysis, i.e. the bursting or rupturing of cell membrane when the cell can no longer contain the excessive inflow of water (or extracellular fluid).

(2) The degeneration or dissolution of cell caused by the disruption of cell membrane.

Semi-Permeable Membrane

A membrane that is selectively permeable, i.e. being permeable to only certain molecules and not to all molecules.
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PostSubject: ahahah!   Sat Jul 17, 2010 9:19 pm

tnX catiis !!!! lol!
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Biology II ( Assignment ) July 16,2010
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