Functional groups are specific arrangements of atoms commonly attached to carbon skeletons. These functional groups are also called chemical groups. They can affect molecular function by being directly involved in chemical reactions. An example is the molecules shape.
The hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, phosphate, and methyl groups are the most important functional groups in biological processes.
The hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, and phosphate gruops are hydrophilic and have an increase in the solubility of organic compounds in water.
The methyl group is not reactive and often acts as a recognizable tag on biological molecules.
Hydroxyl Group:
In a hydroxyl group a hydrogen atom is bonded to an oxygen atom, and this is bonded tothe carbon skeleton of an organic molecule. This bond is -OH and sometimes may be seen as HO-.
The name of the compound is alcohols. Ethanol is an example of this.
Functional properties:
-It is polar
-Can form hydrogen bonds with water molecules and helps dissolve organic compounds
Carbonyl Group:
This group consists of a carbon atom bonded to an oxygen atom by a double bond. The bond looks like -C=O.
In the carbonyl group there is two compound groups, ketones and aldehydes.
Ketones are when the carbonyl group is within the carbon skeleton.
Aldehydes are when the carbonyl group is at the end of the carbon skeleton.
An example of a ketone is acetone.
An example of an aldehyde is propanal.
Functional properties:
-A ketone and aldehyde can be structural isomers with different properties
-These groups are found in sugars:
aldoses(containing an aldehyde)
ketoses(containing a ketone)
Carboxyl Group:
A carboxyl group is when an oxygen atom is double-bonded to a carbon atom that is also bonded to an -OH group. -COOH is a carboxyl group.
The names for the compounds are carboxylic acids or organic acids.
An example of a carboxyl group is acetic acid.
Functional properties:
-Has acidic properties
-It is found in cells in the ionized form with a charge of 1-
Amino Group:
This group consists of a nitrogen atom bonded to two hydrogen atoms and to the carbon skeleton.
The name of a compound is amines.
An example is Glycine.
Functional properties:
-Acts as a base
-Ionized with a 1+ charge, under cellular conditions
Sulfhydryl Group:
Sulfhydryl group has a sulfur atom bonded to an hydrogen atom, it resembles a hydroxyl group in shape.
The compound name for this is Thiols.
An example is cysteine.
Functional properties:
-Two sulhydryl groups can react by forming a covalent bond
-Cross-linking of cysteines in hair proteins maintains the curliness or straightness of hair
Phosphate Group:
In this group a phosphorous atom is bonded to four oxygen atoms . One oxygen atom is bonded to the carbon skeleton.
The name compound is organic phosphates.
An example of this is glycerol phosphate.
Functional properties:
-Contributes a charge to the molecule it is a part of
-Has the potential to react with water, therefore releasing energy
Methyl Group:
This group has a carbon bonded to three hydrogen atoms. It may be attached to a carbon or a different atom.
The compound name of this is methylated compounds.
An example is 5-methyl cytidine.
Functional properties:
-It can affect expressions of genes
-Arrangements of methyl groups in male and female sex hormones affects their shape and function
Quiz:
1. Which function is true about the amino group?
a)has acidic properties
b)acts as a base
c)affects expression of genes
2. Which chemical group could be defined as an aldehyde
a)a carbon atom joined to an oxygen atom by a double bond at the end of the carbon skeleton
b)a carbon atom joined by an oxygen atom by a double bond in the middle of the carbon skeleton
c)can be a structural isomer
d)Both b and c
3. Which action could produce a carboxyl group?
a) a carbon atom double bonded to an oxygen atom
b)a carbon atom double bonded to an oxygen atom and also bonded to a nitrogen atom
c)a carbon atom double bonded to an oxygen atom and the carbon atom is also bonded to an -OH group
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