Dr. Paul's Virtually Biology Show.

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F

Facilitated diffusion. The movement of a substance from a region of high concentration to a region of low concentration across a plasma membrane where this movement can only happen through special protein channels and which involves no use of energy by the cell.
Flavin adenine dinucleotide (FAD) . FAD is fine....FAD is an electron acceptor found in the matrix of the mitochondrion. It is responsible along with NAD+ for accepting electrons and hydrogen ions from the Kreb's citric acid cycle for transfer to the electron transport systems along the inner mitochondrial membrane.
Fat. A lipid with usually three relatively saturated fatty acids attached to a glycerol molecule. Oils are similar except that the fatty acids are unsaturated. Fats and oils together are collectively called triglycerides if they have three fatty acids per glycerol.
Fatty acid. An organic acid consisting of a long non polar hydrocarbon chain with a carboxyl group at one end.
Feedback.The regulation of a control mechanism by the output of the system involving the control mechanism. In negative feedback, output from the system inhibits the production of more output. In positive feedback, output from the system enhances the production of even more output. Feedback is an important concept in hormonal and nervous system control of the body as well as in the study of social and economic systems.
Fermentation. An anaerobic process by which alcohol, lactic acid or other organic compound is produced using the pyruvate produced by glycolysis.
First law of thermodynamics. Under normal conditions energy cannot be created but only converted from one form to another.
Fitness. Fitness refers to the ability of an organism to leave copies of its genes relative to other organisms in the population. It may do so either by having descendants of its own(Classical fitness) or by influencing the reproductive success of relatives that share genes in common with it. The sum of the organism's classical fitness, plus the relative ability of the organism to leave copies of its genes found in relatives, is called inclusive fitness.

Fixed action Pattern(FAP). A sequence of stereotyped behaviors in response to a stimulus in the environment.

Flagellum. A long whip-like projection from the surface of cells and which propel the cell. Often a distinction is made between the eukaryotic flagellum and a prokaryotic flagellum which lacks microtubules. Eukaryotic flagella move internally while the prokaryotic flagella move because of energy transfer from the base.
Fluid mosaic model. The fluid mosaic model treats the cell membrane as a phospholipid bi-layer within which are embedded proteins with various functions. The phospholipid BI-layer can be thought of as the matrix of a mosaic and the proteins, the tiles.
fossil. A fossil is evidence or the remains or prehistoric life. On some occasions as in the case of fossils in amber the organism's remains are preserved but usually the organisms' structures are replaced by various minerals. Tracks of prehistoric creatures also are classed as fossils.

Frame shift mutation. A deletion or addition of a base in a region of DNA. The effect of frame shift mutations is to move every base beyond the mutation by one position meaning that when the mRNA that results from transcription is translated, the codons beyond the mutation point are different. This leads to a radically different sequence of amino acids from translation.

 

Functional Group. A functional group is a an atom or a small group of atoms that attach to another molecule and alter the properties of that molecule. In biology we typically think of biological molecules as consisting of a backbone made of covalently bonded carbon atoms to which various functional groups are attached.

Fungi. The kingdom Fungi are generally multicellular heterotrophs. They are decomposers that obtain their nutrients by external digestion of complex organic matter. In addition to being eukaryotes, fungi usually have a cell wall made of chitin. Examples of Fungi include yeasts, molds, and mushrooms.