Many carbohydrates contain one or more modified monosaccharide units that have had one or more groups replaced or removed.

Chitin is one of many naturally occurring polymers. It is one of the most abundant natural materials in the world. Over time it is bio-degradable in the natural environment. Its breakdown may be catalyzed by enzymes called chitinases, secreted by microorganisms such as bacteria and fungi, and produced by some plants.

Chitin is composed of repeating units of N-acetylglucosamine, a nitrogen-containing form of glucose.

You will get the answer in the riddle itself, if you read the riddle carefully.

The riddle says "A cowboy arrives in town on Friday." So Friday is the name of the horse on which he comes. Hence, the only possibility is he arrives on the horse friday on Tuesday, stays for 3 days and leaves on the same horse on Friday. 

Photosynthesis takes place inside plant cells in small things called chloroplasts.

Chloroplasts contain a green substance called chlorophyll and this absorbs the light energy needed to make photosynthesis happen.

Protons carry a positive electrical charge, electrons carry a negative electrical charge and neutrons carry no electrical charge at all. The protons and neutrons cluster together in the central part of the atom, called the nucleus, and the electrons 'orbit' the nucleus.

$$\begin{gathered} Given 3.2% of 500 × 2. 4% of ? = 312 \\ Then, \\ 3.2 x 500100 x 2.4 x ?100 = 312 \\ 16 x 2.4x?100 = 312 \\ 9.6 x ?25 = 312 \\ 9.6 x ? = 7800 \\ ? = 78009.6 \\ ? = 812.5 \end{gathered}$$

A complete binary tree is a binary tree where all the levels have maximum number of nodes except possibly the last level.

The depth of complete binary tree of n nodes will be Dn=log 2 (n+1) where Dn is the height or depth of the tree and n is the number of nodes.

Protein digestion occurs in the stomach and duodenum in which 3 main enzymes:

1. Pepsin secreted by the stomach 

2. Trypsin and

3. Chymotrypsin secreted by the pancreas

Break down food proteins into polypeptides that are then broken down by various exopeptidases and dipeptidases into amino acids.

Most bacteria divide by binary fission, a form of cell division in which DNA replication and segregation occur simultaneously. This process involves active partitioning of the single bacterial chromosome and positioning of the site of septation.

Bacteria reproduce by binary fission. In this process the bacterium, which is a single cell, divides into two identical daughter cells.

Binary fission begins when the DNA of the bacterium divides into two replicates. The bacterial cell then elongates and splits into two daughter cells each with identical DNA to the parent cell. Each daughter cell is a clone of the parent cell.