Biology 101 - Cell Biology Part 2

Osmosis. Water will always move from areas of low solute to areas with a higher solute concentration. Osmosis is generally tested in cases where two compartments are separated by a semipermeable membrane. The membrane allows water, but not solute, to pass through; osmosis is thus required to promote similar solute concentrations on both sides.

Itis one with the same solute concentration as a solution to which it is compared.

For example, fluids that are administered in an IV should be isotonic with human cells. In other words, they should have the same osmolality, or solute concentration.

In comparison to a reference solution, a hypertonic solution has a greater solute concentration, while a hypotonic solution has a smaller solute concentration.

For example, say that a certain compartment contains 4 grams of NaCl per liter of solution. A solution of 2 g NaCl per L solution would be hypotonic, while a solution of 8 g NaCl per L solution would be hypertonic.

Shark cells are likely hypertonic to human cells.

To avoid excessive water loss or gain, shark cells must be specialized to be isotonic, or at least close, to their surroundings. Since the ocean is composed of salt water, shark cells likely contain more solute than the cells of land-dwelling species.

Gap junctions

The electrical impulse that triggers contraction must travel throughout the entire heart muscle, beginning at the SA node. Gap junctions facilitate the movement of ions, allowing the cells to act together as one unit.

They lack membrane-bound organelles. They generally contain one circular chromosome within a nucleoid region, but can also possess circular plasmids outside the genome.

Prokaryotic cells always comprise unicellular organisms.

1. Prokaryotic cells

2. Eukaryotic cells

Prokaryotic cells are generally simpler and include bacterial species. Eukaryotes can range from single-celled organisms (like yeast) to complex animals (like humans).

The fluid contained within a cell.

In contrast, the cytoplasm includes both the intracellular fluid and all of the extranuclear organelles.

Includes both the intracellular fluid, or cytosol, and the organelles. The only organelle that is not included in the cytoplasm is the nucleus.

The nucleus is encased in a double membrane, known as the nuclear envelope. This membrane is marked by channels called nuclear pores. Inside, a fluid (the nucleoplasm) surrounds linear chromosomes.

It is located within the nucleus. It serves as the site of ribosomal RNA transcription and synthesis of ribosomal subunits.

It contains both an outer and an inner membrane. The intermembrane space is located between the two, while the mitochondrial matrix is the innermost space, bounded by the inner membrane.

Both membranes are phospholipid bilayers.

mitochondria

Just like prokaryotic asexual reproduction, which produces identical daughter cells, this method of division yields identical organelles.

They break down engulfed pathogens, nutrient molecules, and components of the cell itself that are no longer functional.

Like the stomach, a lysosome contains enzymes and an acidic interior.

The ER is a folded membrane divided into two regions: rough ER and smooth ER.

Rough ER contains ribosomes bound to its surface, while the smooth ER does not.

It modifies molecules that arrive from the ER. It has the ability to break off into vesicles and can thus facilitate the exocytosis of these modified products.

• chloroplasts

• vacuoles

Chloroplasts resemble mitochondria and perform the reactions of photosynthesis. Vacuoles are involved in storage.