Biology avEs T 1 o NS A. Definition/Comparison Questions Instructions: In your own words, define the pairs of terms given below. Write in complete sentences, stating the differences and relationships...

Part A
Part A.
1. The similarities among living organisms indicate that all of them have evolved from some single common ancestor. Through the process of gradual modifications, adaptations and natural selection, over a million and a half different species have evolved from a common ancestral form. This process is called evolution. Darwin explained evolution of species Natural selection. He beleuved that as in artificial selection man selects animals or plants with desired characters, same way nature also selects only those individuals which are with more favourable variations and are best adapted to the environment. This sorting out of individuals with useful variations and was called natural selection.
2. Exothermic is related to change in enthalpy. Exergonic is related to change in gibbs free energy. In exothermic reactions energy is released in the form of heat or light. In exergonic reactions the flow of energy is positive and it flows from system to the surroundings.
3. In many cases accumulation of end product of the reaction inhibits the first step of the reaction. This is called allosteric modulation or feedback inhibition. allosteric regulation is when something binds to the active site to physically block the substrate from entering--that is the key point about allosteric regulation/inhibition, something physically gets in the way of the reaction. Feedback inhibition is when the products of the enzymatic reaction stop genetic expression of the enzyme. So the product acts to stop transcription, hence no more enzyme, and the reaction eventually stops because all the enzymes get used up. When the product of the reaction is no longer present (gets used, or sent away) then the gene is expressed again resulting in new enzyme.
4. Extrinsic or peripheral membrane proteins are superficially attached to either face of lipid biomolecular membrane. They can be easily removed by physical methods. Intrinsic or integral membrane proteins penetrate the lipid partially or wholly and are tightly held by strong bonds. To remove them, the membrane is to be disrupted. The integral proteins occurs in various forms and performs varied functions.
5. Prokaryotic cells are the most primitive cells. They are surrounded by a single membrane system. Genetic material is not enclosed by a membrane so that a distinct nucleus is not found. Example: bacteria and cyanobacteria. Essentially all animal and plant cells are eukaryotic. They have more elaborate internal organization than the prokaryotic cells. They have nuclear membrane that separates nuclear material from the cytoplasm.
6. Enzymes are proteinaceous substances which are produced by the living cells to accelerate the biochemical reactions in and outside the the cells in living organisms without undergoing any change. Therefore, they are called biocatalysts. Example : lipase, protease, etc. Ribozyme is an RNA which functions as an enzyme. Its active site is made up of only RNA.
7. Passive transport is the transport of molecules which does not require energy and takes place along the concentration gradient. The transport proteins of biomembranes are in the form of charged channels extending through the lipid bilayer. The channels remain closed. They open only when required substances have to pass through these channels. Active transport is the movement of molecules or ions against the concentration gradient which means that the molecules move from the region of their low concentration to the region of their high concentration.
8. ATP or adenosine triphosphate is the most important energy carrier. It carries energy in two terminal phosphate bonds. The formation of these bonds requires large amount of energy. Hence, these bonds are known as high energy bonds. These bonds are unstable and can easily breakdown releasing corresponding high amount of energy: ATP ( ADP + Pi + energy. The energy released is used by the cell for completing the...