Tag: biology

Amino acids are amphoteric compounds having a carboxylic group, amino group, hydrogen and a substituent group bonded to same carbon atom called the $\alpha$-carbon atom. The substituent group may be having one or more carboxylic groups or amino groups. In case the substituent group is having an extra amino group, the amino acid will be having more than one amino groups and will be positively charged at neutral pH and will be a basic amino acid like lysine and arginine.

Enzymes, vitamins and hormones are critical to the central role of these elements in the metabolism. Some enzymes in addition to the proteinaceous part require an additional organic molecule coenzyme. Most of the coenzymes are derived from vitamins. Hormones are chemically a diverse group. They may be amines or steroids or peptides. The hormones regulate body metabolism over a longer duration and slowly effect the developmental changes during the development of an organism. The main difference between the enzyme (coenzyme) and hormones is the time scale of their operation. Both are similar in their role in regulating body metabolism.

Antibodies are the structures that help in maintaining the immunity of the body towards the antigens that are infectious agent whether be it bacteria or viruses.

Isomers are molecules that have the same molecular formula but have a different arrangement of the atoms in space. That excludes any different arrangements which are simply due to the molecule rotating as a whole or rotating about particular bonds. For example, in respiration, 3PGA and 2PGA, PGAL and DHAP, Glucose and Fructose. 

Lecithin is a phosphorylated glyceride. It is a phospholipid with glycerol, fatty acids ,a phosphate group and choline. It is found in the cell membrane. Palmitic acid is a saturated fatty acid with 16 carbon atoms. Adenylic acid is also called as Adenosine monophosphate (AMP). It is an adenosine with a phosphate group and the ribose sugar. It is an ester of phosphoric acid and the adenosine. Alanine is a neutral amino acid. It contains one amino group and one carboxylic group.

The composition of the different organic compounds in the animal body in terms of dry weight is as protein-71%, lipid-12%, nucleic acid-7%,  carbohydrate-5% and inorganic and other materials-5%. These four classes of organic material are important and form the basis of organic constituents in the cell. All these macromolecules except lipids are formed by the process of polymerisation. Due to their large size and complex 3-dimensional shape, these organic biomolecules function as structural components, enzymes, energy sources,molecular messengers, nutrient stores and sources of genetic information. Carbohydrates are polyhyroxyaldehydes or polyhyroxyketones or substances that gives this on hydrolysis. They are classified as monosaccharides, oligosaccharides and polysaccharides. Pentoses and hexoses are the most important sugars. Complex polysaccharides are important components of inter-cellular ground substances. Lipids are major and essential components of biological membranes. They are important dietery components and forms major forms of energy, because of their high calorific value. Protein is a polymer of different amino acids linked together by peptide bonds. Proteins can be fibrous or globular. Structural proteins serve as building materials for cells and tissues. Functional proteins regulate metabolism. Nucleotides, the monomer units of nucleic acids serve many important functions in cells. They store the genetic information in them. They are also primary carriers of chemical energy in cells, structural components of many enzyme cofactors and cellular second messengers. Thus, the four macromolecules play a significant role in performing various cellular functions.

A number of purine bases containing methyl substituents occur in plants and plant products and many of them have pharmacological properties. For example Theophylline is chemically 1,3-dimethylxanthine. It is found in tea. Theobromine occurs in cocoa. It is chemically 3,7-dimethylxanthine. Caffeine is present in coffee. It is chemically 1,3,7-trimethylxanthine. 

Necturus (Mud puppy, Amphibia) possesses three pairs of external gills. Pila (Apple snail, Mollusca) respires by means of gills (ctenidium) in water and by a pulmonary sac on land. Millipedes (Arthropoda) respire by tracheae (tracheal respiration) and toads (Amphibia) exhibit buccopharyngeal respiration.

Land animals respire with lungs. With the help of lungs, these animals take in the oxygen in the air. However, fishes do not have lungs. They respire with gills. With the help of the gills, they breathe in the oxygen present in the water. Fishes take in water through mouth. The gill filaments absorbs oxygen from this water and distribute to the rest of body.