Tag: biology

Carbohydrates are the preferred fuel for cellular respiration. Excess carbohydrates are stored as glycogen in muscles and liver. Glycogen storage is for short duration only. Glycogen reserves meet energy demand between meals and during intense physical exercises. Long term storage of carbohydrates occurs as fats. After storing glycogen, still extra carbohydrates available are converted to fats for long term storage in the body.

The fats contain more energy per gram than carbohydrates and as a result of this, the body tends to use fat to store energy over long periods of time and uses carbohydrates to store energy short-term.
Therefore, the correct answer is option B.

We need energy for doing work. Energy is provided by carbohydrates and fats. Carbohydrates and fats on oxidation liberate energy. As compared to fats, carbohydrates get easily oxidized and converted into glucose and provide energy. One gram of carbohydrate yields about 17 kilo-joule of energy, whereas one gram of fat produces 37 kilo-joule of energy. This is the reason why carbohydrates and fats are called as energy food.

Slightly less than half of the cholesterol in the body derives from biosynthesis de novo. Biosynthesis in the liver accounts for approximately 10% and in the intestines approximately 15%, of the amount produced each day. The cholesterol biosynthesis pathway involves enzymes that are in the cytoplasm, microsomes (ER), and peroxisomes. Synthesis of cholesterol, like that of most biological lipids, begins from the two-carbon acetate group of acetyl-CoA. Cholesterol synthesis does not occurs in pancreas, spleen and Brunner's gland. 

Oxidation refers to the direct breakdown of nutrients for energy. Fats or lipids have the highest energy content of 9 kcal/gm while proteins and carbohydrates have 4 kcal/gm.
Therefore, the correct answer is option D.

Products of $\beta$-oxidation are as follows-
a) Acetyl ${C} _{0}A$
b) $FAD{H} _{2}$
c) $NAD{H} _{2}$

Although, the main source of energy for our bodies is carbohydrates, fat is used as a source of backup energy in cases when carbohydrates are not available. This is a concentrated energy source but it is important to remember that each gram of fat has nine calories (over double the calories from protein and carbohydrates) so you should avoid having more than 20 to 35% of your daily calories from fat. In a 1,800 calorie diet, you should only consume 40-70 grams of fat.