Identification by Structure - Biochemistry

An easy way to distinguish the substrate nd the product from the enzyme is that the enzyme will end in "ase". The following are the common substrates, enzymes and the associated products.

The structure is a ketopentose. Keto- refers to the ketone at the second carbon and pentose refers to a carbohydrate with five carbons.

Amylopectin & amylose are joined to make starch. Cellulose is found in the cell wall of plant cells. Glycogen and maltose are not found in plants.

This is the ring/cyclic structure of D-fructose.

This ring structure is of D-glucose. The hydroxyl group on the first carbon (the carbon to the bottom right of the oxygenin the ring) can face either down (the alpha conformation) or up (the beta conformation). Note that the beta conformer is more thermodynamically stable since all the hydroxyl groups on the ring would be in the equitorial position, thus minimizing steric hinderance and intramolecular electrostatic repulsion.

The correct structures of the disaccharides are:

Maltose = glucose + glucose

Sucrose = glucose + fructose

Lactose = glucose + galactose

The pictured structure represents arachidonic acid due to the 20-carbon carboxylic acid chain with characteristic unsaturated (double) bonds after carbons 5, 8, 11, and 14.

Oleic acid is a fatty acid consisting of 18 carbon molecules and a single unsaturated (double) bond after carbon 9, as pictured.

The structure represents cholesterol. The hydroxyl group attached to the terminal cyclohexane and the 6-carbon chain on the opposite end are easily recognizable substituents.

Unsaturated fats are said do be unsaturated because of their lack of saturation with hydrogen atoms, due to carbon's ability to make four bonds, and one or more carbons in the hydrocarbon tail of an unsaturated fatty acid contains a double bond to another carbon. Both unsaturated and saturated fats are lipids, but neither contain cholesterol nor glycogen.

Triacylglycerols, like phospholipids and glycolipids, have long, hydrophobic, fatty acid tails. Steroids are characterized by their ABCD ring structure. Isoprene, the building block of steroids and polyisoprenoids, has five carbon atoms.

The structure is adenine because of the characteristic amine group on carbon 6 and lack of any other substituents.

The structure represents guanine because of the characteristic carbonyl group at carbon 6 and amine group and carbon 2.

The structure represent thymine because of the characteristic carbonyl groups at both carbons 2 and 4 and the methyl group at carbon 5.

The structure represents uracil because of the carbonyl groups attached to both carbons 2 and 4 and the lack of any other substituents.

The structure represents cytosine because of the characteristic amine group on carbon 4, instead of the carbonyl group that is present on carbon 4 of both thymine and uracil.

Pyrimidines are nitrogenous bases with 1 ring structure, whereas purines are nitrogenous bases with 2 ring structures. Cytosine and thymine are pyrimidines since they both have one ring structure, whereas adenine and guanine are purines with two connected ring structures. (Note: in RNA, uracil would be considered a pyrimidine in the place of thymine.) One way to help you remember which bases belong to which chemical groups, remember that pyrimidines, like pyramids are sharp, and sharp things CUT - Cytosine, Uracil, and Thymine.

The six-membered ring is a pyrimidine. The purine ring system has two rings: a six-membered and a five-membered ring. These aromatic rings are hydrophobic, making them relatively insoluble. The pyrimidine bases in nucleotides are cytosine, uracil, and thymine; the purine bases in nucleotides are adenine and guanine.

A nucleoside is the nitrogenous base bound to a sugar via glycosidic bond. A nucleotide is a nitrogenous base bonded to a sugar bonded to the phosphate. This nitrogenous base is cytosine. If it were bound to ribose, it would be called cytidine. Although cytosine is a pyrimidine like uracil and thymine, pyrimidine is a class of ring structure, not the specific name of a base.