Explain any five of the following terms (innot more than four lines each):
(i) Osmosis

osmosis, in botany and chemistry, the flow of one constituent of a solution through a membrane while the other constituents are blocked and unable to pass through the (selecyively permeable membrane)membrane. experimentation is necessary to determine which membranes permit selective flow, or osmosis, because not all membranes act in this way. many membranes allow all or none of the constituents of a solution to pass through; only a few allow a selective flow




glycolysis
Glycolysis, chemical process in which glucose is broken down, or catabolized, into the simpler sugar lactic acid, and energy is released.


(ii) Phototaxis

movement of organism caused by light: movement of an organism either toward or away from a source of light . Phototaxis is called positive if the movement is in the direction of light and negative if the direction is opposite.


(iii) Transpiration

Transpiration
Transpiration, evaporation of water particles from plant surfaces, especially from the surface openings, or stomata, on leaves . Stomatal transpiration accounts for most of the water loss by a plant, but some direct evaporation also takes place through the surfaces of the epidermal cells of the leaves.


(iv) Saponification:Saponification is the hydrolysis of an ester under basic conditions to form an alcohol and the salt of a carboxylic acid (carboxylates). Saponification is commonly used to refer to the reaction of a metallic alkali (base) with a fat or oil to form soap. Saponifiable substances are those that can be converted into soap.

Sodium hydroxide (NaOH) is a caustic base. If NaOH is used a hard soap is formed, whereas when potassium hydroxide (KOH) is used, a soft soap is formed. Vegetable oils and animal fats are fatty esters in the form of triglycerides. The alkali breaks the ester bond and releases the fatty acid salt and glycerol. If necessary, soaps may be precipitated by salting it out with saturated sodium chloride. The saponification value is the amount of base required to saponify a fat sample.



(v) EmulsionA suspension of small globules of one liquid in a second liquid with which the first will not mix: an emulsion of oil in vinegar

related extra topics

Chemotaxis, a kind of taxis, is the phenomenon in which bodily cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food (for example, glucose) by swimming towards the highest concentration of food molecules, or to flee from poisons (for example, phenol). In multicellular organisms, chemotaxis is critical to early (e.g. movement of sperm towards the egg during fertilization) and subsequent phases of development (e.g. migration of neurons or lymphocytes) as well as in normal function.
Chemotaxis is called positive if movement is in the direction of a higher concentration of the chemical in question, and negative if the direction is opposite.

Phototropism is directional growth in which the direction of growth is determined by the direction of the light source. In other words, it is the growth and response to a light stimulus. Phototropism is most often observed in plants, but can also occur in other organisms such as fungi. Phototropism is one of the many plant tropisms or movements which respond to external stimuli. Growth towards a light source is a positive phototropism, while growth away from light is called negative phototropism (or Skototropism). Most plant shoots exhibit positive phototropism, while roots usually exhibit negative phototropism, although gravitropism may play a larger role in root behavior and growth. Some vine shoot tips exhibit negative phototropism, which allows them to grow towards dark, solid objects and climb them.

Phototropism in plants such as Arabidopsis thaliana is regulated by blue light receptors called phototropins.[1] Other photosensitive receptors in plants include phytochromes that sense red light[2] and cryptochromes that sense blue light


rgds