How Does It Work ArtifactBy David PorterNathan AnthonyReinaldo RosaJulie Bowen

Passive Transport• Diffusion-The act of spreading something more widely. • Dialysis-The separation of particles in a liquid on the basis of

differences in their ability to pass through a membrane.• Osmosis-The tendency of molecules of a solvent to pass

through a semipermeable membrane from a less concentrated solution into a more concentrated solution.

• Facilitated Diffusion-(also known as facilitated transport or passive-mediated transport) is a process of passive transport (as opposed to active transport), with this passive transport aided by integral membrane proteins. Facilitated diffusion is the spontaneous passage of molecules or ions across a biological membrane passing through specific trans membrane integral proteins.

• Filtration-The action or process of filtering something.

Passive Transport

• While active transport requires energy and work, passive transport does not. There are several different types of this easy movement of molecules. It could be as simple as molecules moving freely such as osmosis or diffusion. You may also see proteins in the cell membrane that act as channels to help the movement along. And of course there is an in-between transport process where very small molecules are able to cross a semi-permeable membrane.

• Sometimes, proteins are used to help move molecules more quickly. It is a process called facilitated diffusion. It could be as simple as bringing in a glucose molecule. Since the cell membrane will not allow glucose to cross by diffusion, helpers are needed. The cell might notice outside fluids rushing by with free glucose molecules. The membrane proteins then grab one molecule and shift their position to bring the molecule into the cell. That's an easy situation of passive transport because the glucose is moving from higher to lower concentration. It's moving down a concentration gradient. If you needed to remove glucose, the cell would require energy.

• LETTING CONCENTRATION DO THE WORK• Sometimes cells are in an area where there is a large concentration difference. For example,

oxygen molecule concentrations could be very high outside of the cell and very low inside. Those oxygen molecules are so small that they are able to cross the lipid bilayer and enter the cell. There is no energy needed for this process. In this case, it's good for the cell because cells need oxygen to survive. It can also happen with other molecules that can kill a cell.

Passive Transport • OSMOSIS• Another big example of passive transport is osmosis. This is a water

specific process. Usually, cells are in an environment where there is one concentration of ions outside and one inside. Because concentrations like to be the same, the cell can pump ions in an out to stay alive. Osmosis is the movement of water across the membrane.

• For a cell to survive, ion concentrations need to be the same on both sides of the cell membrane. If the cell does not pump out all of its extra ions to even out the concentrations, the water is going to move in. This can be very bad. The cell can swell up and explode. The classic example of this type of swelling happens when red blood cells are placed in water. The water rushes in to the cells, they expand and eventually rupture

Active Transport• Pumps-A mechanical or biological device using suction or

pressure to raise or move liquids, compress gases, or force air into inflatable objects such as tires.

• Endocytosis-The taking in of matter by a living cell by invagination of its membrane to form a vacuole.

• Exocytosis-A process by which the contents of a cell vacuole are released to the exterior through fusion of the vacuole membrane with the cell membrane

Active Transport• Substance moving across a membrane from lower

concentration to higher concentration, using energy supplied through ATP, controlled by the Mitochondria

• Commonly occurs are in the small intestine.

Cell Metabolism• Catabolism-The breakdown of complex molecules in living

organisms to form simpler ones, together with the release of energy; destructive metabolism.

• Anabolism-The synthesis of complex molecules in living organisms from simpler ones together with the storage of energy; constructive metabolism

• Enzymes-A substance produced by a living organism that acts as a catalyst to bring about a specific biochemical reaction.

Cell Metabolism• The chemical processes occurring within a living cell or

organism that are necessary for the maintenance of life. In metabolism some substances are broken down to yield energy for vital processes while other substances, necessary for life, are synthesized.

• Occurs in all cells.

Protein Synthesis• Transcription-The action or process of transcribing something.• Translation-The act or process of translating.

Protein Synthesis• 1. Transcription

Before the synthesis of a protein begins, the corresponding RNA molecule is produced by RNA transcription. One strand of the DNA double helix is used as a template by the RNA polymerase to synthesize a messenger RNA (mRNA). This mRNA migrates from the nucleus to the cytoplasm. During this step, mRNA goes through different types of maturation including one called splicing when the non-coding sequences are eliminated. The coding mRNA sequence can be described as a unit of three nucleotides called a codon.

• 2. Translation The ribosome binds to the mRNA at the start codon (AUG) that is recognized only by the initiator tRNA. The ribosome proceeds to the elongation phase of protein synthesis. During this stage, complexes, composed of an amino acid linked to tRNA, sequentially bind to the appropriate codon in mRNA by forming complementary base pairs with the tRNA anticodon. The ribosome moves from codon to codon along the mRNA. Amino acids are added one by one, translated into polypeptidic sequences dictated by DNA and represented by mRNA. At the end, a release factor binds to the stop codon, terminating translation and releasing the complete polypeptide from the ribosome

Growth• Cell Growth-The term cell growth is used in the contexts of cell

development and cell division (reproduction) When used in the context of cell division, it refers to growth of cell populations, where one cell (the "mother cell") grows and divides to produce two "daughter cells".

• Cell Reproduction-The term cell growth is used in the contexts of cell development and cell division (reproduction) When used in the context of cell division, it refers to growth of cell populations, where one cell (the "mother cell") grows and divides to produce two "daughter cells".