¶ … living things are characterized by the following seven characteristics namely mobility, respiration, excretion, sensitivity or response to external stimulus, growth, feeding, and reproduction. Though there may be variations between animal and plant kingdom (ex, plants take in carbon dioxide and prepare their own food), these characteristics are commonly observed among all living things. Biology is a very broad field that encompasses the study of characteristics of living things. It includes botany, zoology and all other sub-disciplines that range from microbiology to evolution and ecology.

Evolution is the branch of biology that deals with the study of natural development of living organisms and the changes in them over time. Evolution refers to the heritable changes that occur in a population over a period of time. All the diversity that is observed currently in plant and animal kingdom can be ascribed to evolution over a long period of time.

Atoms are the smallest, fundamental building blocks of every living and non-living matter. Molecules are nothing but groups of atoms bound together by means of chemical bonds.

5) Water is a universal solvent that dissolves most molecules and it is non-reactive as well. All plant and animal life is dependant on water and together with the sun it is responsible for maintaining the complex weather cycles around the world and is the fundamental component of all food chain. It is also a buffer against sudden and drastic changes in temperature of the earth.

6) Carbohydrates are simple sugars or complex polymers made up of carbon, hydrogen and oxygen. Carbohydrates represent the main source of energy to the human body. Sugars, starch and cellulose are different forms of carbohydrates.

7) Lipids are organic molecules that are insoluble in water and other polar solvents. ((Ex, oil). This property of lipids is important as they makeup the cell membrane of all living beings.

8) Proteins are complex amino acid molecules that are essential for carrying out a variety of important functions. Asides providing structural support for the cell membrane, proteins also act as antibodies, messengers and enzymes that are indispensable for the proper functioning of the body.

9) Nucleic acids are large molecules or polymers that result by the combination of nucleotides. DNA and RNA are two main nucleic acids. ATP is another important nucleic acid, which supplies the energy demands of the cell.

10) There are two main types of reactions namely exergonic reactions and endergonic reactions. Exergonic reactions give away energy while endergonic reactions require energy.

11) Enzymes are proteins that catalyze specific biochemical reactions. They are synthesized inside the cells and function under specific conditions. They have a key role in cell metabolism.

12) A Prokaryotic Cell

[Mark Rothery]

13) An Eukaryotic Cell

[Mark Rothery]

14) Photosynthesis is the best example of light energy being converted into chemical energy. The pigments in chloroplasts use light energy to create energy carrier molecules namely ATP (Adenosine Triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate), which in turn react with Co2 and water to form sugar and oxygen.

15) The C3 cycle also known as the Calvin cycle is a light independent reaction (dark reaction) which fixes the carbon during photosynthesis. The carbon thus fixed up during the C3 cycle is used up to produce glucose.

16) The following chemical reaction explains the metabolization of glucose.

C6H12O6 + 6 O2 --> 6 CO2 + 6 H2O + energy. Essentially this breakdown of glucose involves the removal of hydrogen and the combination with oxygen resulting in water and oxidized carbon as end products.

17) Glycolosis refers to the chemical process of extracting energy from stored glucose. During glycolosis a sequence of reactions occur whereby one molecule of glucose is converted into 2 molecules of pyruvate along with the release of 2 molecules of ATP and 2 molecules of NADH. Glycolosis takes places within the cell cytoplasm.

18) Chromosomes are composed of proteins and nucleic acid (DNA). They are found inside the nucleus of the cells and genetic information is stored in them in the form of genes.

19) DNA has a double helical structure and is made up of two polynucleotides held together by weak...

The four different nitrogenous bases in the DNA lead to four types of nucleotides. The base pairs are arranged parallel to each other giving a double helical structure to the DNA molecule with the phosphates arranged on the outside of the helix.
20) Since DNA replication is nothing but an exact copy of the DNA all the genetic information is passed on intact to the new cell thereby maintaining genetic constancy.

21) Genes are composed of DNA and carry the information necessary for protein synthesis. The particular arrangement of the nucleotides makes a gene code for a specific protein or a RNA molecule. The synthesis of proteins by genes is critical for the control of various bodily functions.

22) Different types of RNA such as transfer RNA, messenger RNA and Ribosomal RNA are involved in protein synthesis. The transfer RNA selects the amino acids that are to be rearranged while the messenger RNA provides the instructions about the sequence of the amino acids. The ribosomal RNA is responsible for the actual attaching process. (Different sequences yield different proteins)

23) Mutations to the DNA will affect the composition of the gene. This in turn means that the mRNA from that gene will carry a different message leading to the formation of polypeptides (translation of mRNA), which have a different sequence of amino acids. Consequently, the proteins derived from this polypeptide will also have different function.

24) Gene expression is controlled in many ways in Eukaryotes. DNA binding activators hold the key in controlling gene expression. The chromatin structure may also inhibit access to specific genes for the transcription factors thus blocking transcription initiation. Activators, repressors, RNA transport, RNA degradation all affect gene expression.

25) The cell cycle of the prokaryotes is divided into three distinct phases. First is the growth phase G. where the cell grows followed by the replication of the DNA (S phase) and the final division or separation called cytokinensis. (Phase C)

26) The eukaryote cell cycle is a bit more complex than the prokaryote cell as it involves multiple chromosomes along with histones and similar protein molecules. Following the initial growth phase G1, the S. phase proceeds with replication of the DNA and synthesis of other protein substances. Next is the G2 phase wherein the DNA is repaired. Next is the M. phase (attachment of microtubules) which involves the separation of sister chromatids (mitosis). This is finally followed by the actual cell division or cytokinensis resulting in two daughter cells.

27) Interphase, prophase, metaphase, anaphase, and telophase / cytokinensis are the five phases of mitosis.

28) Meiosis occurs in two stages namely meiosis1 and meiosis 2. Crossing over and chromosomal alignment are two key events in meiosis. Crossing over happens in stage 1 of meiosis and homologous chromosomes are exchanged resulting in genetic recombinations. Chromosomal alignment refers to the random shuffling and alignment of the paternal and maternal chromosomes.

29) Cytokinensis is the final phase of the mitosis process wherein the cell with two separate nuclei in the opposite sides is divided into two approximately equal cells. This is done by cleavage of the cell wall and cytoplasmic split.

30) Mendel was the first proponent of the theory of heredity. By his experiments with the pea plants he created a revolutionary breakthrough in the understanding of traits and how they were transferred to successive generations. Mendel's principle of segregation' and the 'principle of independent assortment' laid the foundation for modern genetics.

31) Mendel's law of segregation explains inheritance of single traits. During gamete formation alleles segregate and they are randomly united during fertilization. The dominance of the alleles explains the expression of a particular character trait or its phenotype.

32) Inheritance of multiple traits is explained by the law of independent assortment. Mendel proposed that 'genes on different chromosomes are inherited independently'.

33) Our success with the human genome project has provided us with complete mapping of the 20,000 to 25,000 genes present in the DNA. Though much analysis pertaining to the billions of chemical base pairs that constitute the DNA is yet to be completed, the completion of human genome project has made available a variety of gene tests that can identify genetic disorders.

34) There are many genetic disorders that are ascribed to errors in single genes that are inherited. Examples include cystic fibrosis, muscular dystrophy and albinism. In all these cases the abnormal gene hinders the production of a particular protein that is usually synthesized in a normal body without the genetic anomaly.

35) Biotechnology is the convergence of biology and information technology that has resulted in a paradigm shift in our understanding of bio-molecular chemistry and its application in the field of medicine.

36) DNA recombination occurs naturally by way of homologous recombination. (After transformation). Strands of DNA are exchanged between homologous nucleotide sequences. The Helicobacter pylori bacterium is the most common example of recombinant species that absorbs DNA from its environment.

37) Biotechnology has provided scientists with new means to understand the complexity of protein functions. Molecular cloning, an important tool in biotechnology, has…