Enzymes are organic molecules that are essential raw materia

Enzymes are organic molecules that are essential raw materials for a chemical reaction that are converted into some of it products increase the speed of a chemical reaction determine the nature of the products of a reaction alter the direction in which a chemical reaction proceeds Molecules formed when electrons are unequally shared are non-polar molecules salts polar molecules Which of the following does not describe a mixture? chemical bonds are formed includes both heterogeneous and homogenous examples components can be separated physically properties of its components are retained

Solution

Ans. 4. Enzymes as organic molecules that B. increase the speed of a chemical reaction. Note: “C” is also correct statement.

Enzymes are biomolecules (mostly proteins; few are RNA, too) or organic molecules that act as biocatalyst (catalyst in a biochemical reaction of the cell), thus increase the rate (speed) of a chemical reaction by lowering the activation energy of the specified reaction.

Option A. Incorrect. Enzymes are NOT converted into products; they are (bio)catalysts.

Option C. Determine the nature of the products of a reaction. True statement.

Enzymes are highly specific in their catalysis- they bind to specific substrate and convert it into specific product(s). For example, consider restriction endonuclease (enzymes), EcoR1 and BamH1. For a hypothetical case, EcoR1 cuts a 100 kb DNA fragment into three fragments- 10 kb, 30 kb and 60 kb. BamH1 cuts the same DNA into 5 fragments- 20 kb, 20 kb, 30 kb, 10 kb and 20 kb. Therefore, the nature of product obtained from a substrate depends on the enzyme, i.e. different enzymes convert the same substrate (reactant) into different products.

Option D: Need explanation of “chemical reaction”. Generally, enzymes catalyze a chemical reaction inside cell and shall not be compared to a chemical reaction occurring in a purely non-biological system in general. The comparison can only be made for a specified reaction. Since, here no chemical reaction is mentioned, a generalization can’t be made.

So, enzymes catalyze a particular reaction in a particular direction under given “set of reaction environments like pH, temperature, substrate concertation, product concentration, modulators, etc”. Thus, they don’t alter the direction of a chemical reaction, unless there is a change in ““set of reaction environments”. SO, this statement is incorrect.

Ans. 5. Correct option: C. polar molecules

Consider the case of water molecule (H₂O). A larger difference in the electronegativity of the two atoms in a bond (say, O and H-atoms in a O- H bond) causes partial charge separation because the electronegative atom (O-atom) pulls the bonding electrons slightly towards itself, i.e. electrons are shared unequally or placed more close to electronegative O-atom. Thus, the electronegative O- atom gets a partial negative charge and the less electronegative H- atom gets a partial positive charge. It makes the bond polar (two poles of charge- a partial negative pole of O-atom, and partial positive charge on H-atom).   

Non-polar molecule has bonding electrons equally shared between two atoms because both the atoms in the molecule has the same electronegativity. For example, O₂ or H₂ , etc.

Salts are ionic compounds. Sharing of electrons occurs only in covalent compounds, not in ionic compounds.    

Ans. 6. Correct option A. Chemical bonds are formed. Formation of a “chemical bond” produces “compounds” – these are NOT mixtures.

Mixture is an aggregation or combination of two or more chemical species (or substances) where each component retains (preserves) its chemical and physical nature.

A homogenous mixture (milk mixed with water), heterogenous mixture (table sugar mixed table salt).

The components of a mixture can be separated by physical methods like boiling, freezing, centrifugation, hand-picking, solubility, etc.

Each component of a mixture retains its physical and chemical properties. For example, a mixture of table sugar mixed table salt tastes sweet (sugar) as well as salty (salt).