Tag: biology

Lipids are hydrophobic means water hating. They are water insoluble. Lipids are non-polar molecules while water is polar molecule, so there is no way for water to attach to a lipid molecule. Instead, the non-polar lipids will bind to themselves, which is why oils and fats form droplets on the surface of water.

Membrane phospholipids are amphipathic having a polar head made of phosphate residue and a non-polar lipid tail. The polar phosphate head is exposed on the surface while non-polar lipids are embedded within the interior of membrane.

• The yeast changes the sugar in the dough into carbon dioxide gas and ethanol (alcohol).
•  The gas, trapped in the dough, makes it rise; the alcohol produced during fermentation evaporates during baking. Hence, When you add yeast to the dough, it rises because the rapidly reproducing yeast cells release carbon dioxide due to anaerobic respiration.

Yeast are the organism that executes the process of fermentation in which they break down the sugar into its simpler forms for obtaining energy. In this process carbon dioxide and alcohol are also forms and CO$ _2$ helps the dough to rise. The process is favorable in humid and warm conditions in colder environment it slows down.

Fermentation is a form of anaerobic respiration in which alcohol is formed by the breakdown of glucose in the absence of oxygen. It usually done by the yeast. In alcoholic fermentation, pyruvic acid is converted into ethanol with the liberation of carbon dioxide. The alcoholic fermentation equation is as follows: 
C$ _6$H$ _{12}$O$ _6$ + 2 ADP + P --> 2 C$ _2$H$ _5$OH + 2 CO$ _2$ + 2 ATP

Anaerobic respiration refers to the type of respiration that takes place without oxygen. In plants, the glucose is anaerobically converted to ethyl alcohol, ATP and carbon dioxide.

Intracellular acidosis occurs due to lactic acid accumulation, it has been regarded as the most important cause of skeletal muscle fatigue. Lactic acid is formed and accumulated in the muscle under conditions of high energy demand, rapid fluctuations of the energy requirement and insufficient supply of oxygen. Subsequently, the pyruvate synthesised during glycolysis is converted to lactic acid in anaerobic condition. Thus, the correct answer is option D.

Fermentation is an anaerobic process which takes place in the absence of oxygen that converts sugar to acids or alcohol. It occurs in yeast, bacteria, and also in oxygen-starved muscle cells, as in the case of lactic acid fermentation. 

Facultative anaerobes are organisms which can switch over to the anaerobic mode of respiration when needed they can also grow in absence of oxygen.