Carbohydrates and Biomolecules

• Plaque is a soft, sticky film that builds up on your teeth and contains millions of bacteria. 
• When you eat, the bacteria in plaque use the sugars in your food to produce acids that eat away at the tooth enamel. Hence, Sugar + Plaque → acids.

In animals, the structurally similar glucose polymer is the more densely branched glycogen, sometimes called "animal starch". Glycogen's properties allow it to be metabolized more quickly, which suits the active lives of moving animals.

Carbohydrates are a source of energy and primary cellular fuel. Cereals like rice, wheat, maize are a primary source of carbohydrate for man. Humans can digest starch present in cereals but not cellulose. Hence, dietary starch is broken down into glucose inside the body which provides us with energy.

Carbohydrates provide us with energy. Carbohydrates can be monosaccharides (composed of one monomer unit only like glucose, fructose etc.), disaccharide (composed of two monomer units like maltose which is made up of two units of glucose; sucrose made up of one unit of glucose and one unit of fructose) or polysaccharide (made up of multiple monomer units example starch which is composed of multiple units of glucose).

Carbohydrates can be stored in body for subsequent use. Starch is an important storage polysaccharide in plants and glycogen is an important storage polysaccharide in animals. Both starch and glycogen are homopolymers of glucose.

The most commonly used artificial sweetener is aspartame. It was discovered by James M. Schlatter in 1965. It is used for deserts. It is used as a sugar substitute. It is not suitable for baking, as high temperatures it breaks it into its constituent amino acid. So, the correct answer is option C.

The cells, tissues, semen and embryo can be preserved for longer periods at lower temperatures using cryopreservation. When the cells are frozen, there is formation of ice crystals in the cells which will rupture the cells. The cryoprotectants like DMSO (dimethylsulphoxide) prevents the formation of these crystals when the cells are stored in liquid nitrogen. 

The blood glucose level in body is tightly regulated by a number of mechanism. The normal blood glucose level in humans should not exceed 140 mg per decilitre after meals and is maintained between 70 to 100 mg per decilitre under fasting conditions without food. Glucose is a precious metabolite and, hence, is actively reabsorbed by the kidney tubules. Any excess quantity of glucose is converted into glycogen which is stored in liver and muscles. Any further excess is converted to fats and stored for long term deposit. In humans and most other mammals, acetyl CoA formed in the liver during oxidation of fatty acids may enter the citric acid cycle or may be converted to ketone bodies, i.e., acetoacetate, $\beta$-hydroxy-butyrate and acetone for export to other tissues. Overproduction of ketone bodies can occur in conditions of severe starvation and in uncontrolled diabetes.

Carbohydrate, on the basis of the number of molecules present, is divided into monosaccharides, disaccharide and polysaccharides. Fructose is also known as the fruit sugar and is a monosaccharide. It is a 6 carbon molecule. Glycine is the simplest amino acid as it contains hydrogen in the side chain. Lactose is a disaccharide which means it has two molecules of same or different monosaccharide units. Lactose is also known as the milk sugar. 

Macromolecules are the molecules made by the attachment of micro molecule. These are complex molecules. Cellulose, DNA, and glycogen are macromolecules as they are formed by linkage of simple monomers.

Isomers are molecules that have the same molecular formula but have a different arrangement of the atoms in space. That excludes any different arrangements which are simply due to the molecule rotating as a whole or rotating about particular bonds. For example, in respiration, 3PGA and 2PGA, PGAL and DHAP, Glucose and Fructose. 

Respiratory quotient or R.Q is defined as the ratio of carbon dioxide evolved to oxygen taken in for respiratory break down of a substrate. The value of R.Q for oxidation of carbohydrates is unity and less than one for oxidation of fats and proteins. Thus if groundnut, which stores fats is used as respiratory substrate the value of R.Q will be less than one.

R.Q. is the ratio of amount of CO$ _2$ produced to the amount of O$ _2$ consumed by the cell for respiration. R.Q. value of protein is 0.8 as the volume of carbon dioxide released is less than the amount of oxygen. Carbohydrates, organic acid and starch have R.Q. of 1 or greater than 1.