BioScience Dictionary

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Found Mole 661 times.

Displaying results 1 to 10.

1. 1,4-glucan branching enzyme (brancher, branching enzyme, Q enzyme)
An enzyme which makes new branches in glycogen or amylopectin molecules by moving a 1,4-D- glucan chain on the molecule to a primary hydroxyl group (an -OH group) on the same molecule.

2. 5-methylcytosine (5MeC)
This is the methylated form of cytosine (a nitrogenous base in nucleic acids); i.e., a methyl group has been added to the cytosine molecule.

3. Abnormal hemoglobin
Hemoglobin molecule with a different shape due to an altered amino acid sequence (ultimately caused by an altered DNA base sequence), such as in the inherited disease sickle-cell anemia .

4. Absolute configuration
The three-dimensional arrangement of the atoms around the chiral center of a molecule.

5. Absolute zero
This is the lowest possible temperature (0 Kelvin, -273.15 Celsius, -459.67 Fahrenheit). At this temperature, all molecular motion stops.

6. Absorbance (optical density)
This is a measure of the amount of light absorbed by a suspension of bacterial cells or a solution of an organic molecule; it is measured by a colorimeter or spectrophotometer . Absorbance values are used to plot the growth of bacteria in suspension culture s and to gauge the purity and concentration of molecules (such as proteins) in solution. Absorbance is defined as a logarithmic function of the percent transmission of a wavelength of light through a liquid.

7. Accumulation
Repeated exposures to a chemical may result in the progressive increase of its concentration in an organism, organ or tissue; illness or other effects may increase with successive doses. Factors involved in accumulation include selective binding of the chemical to tissue molecules, concentration of fat soluble chemicals in body fat, absent or slow metabolism of the chemical, and slow excretion of the chemical. Accumulation is a mass balance effect where input exceeds output.

8. Acetyl CoA
An intermediate compound formed during the breakdown of glucose by adding a two-carbon fragment to a carrier molecule (Coenzyme A or CoA).

9. Acetyl coenzyme A (acetyl CoA)
This coenzyme plays a huge role in intermediary metabolism, in which cells synthesize, break down or use nutrient molecules for energy production, growth, etc.

10. Acetyl group
A CH3CO- group on a larger molecule, where the -CH3 (a methyl group) is single-bonded to the carbon, an oxygen is single-bonded to the carbon, and the carbon has two other bonds to the rest of the molecule.

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