Lipid (Biology)

Lipid is chemically defined as a substance that is insoluble in water and soluble in alcohol, ether, and chloroform. Lipids are an important component of living cells. Lipids are the main constituents of plant and animal cells. Cholesterol and triglycerides are lipids.

Fatty Acids

The common feature of these lipids is that they are all esters of moderate to long chain fatty acids. Acid or base-catalyzed hydrolysis yields the component fatty acid, some examples of which are given in the following table, together with the alcohol component of the lipid. These long-chain carboxylic acids are generally referred to by their common names, which in most cases reflect their sources. Natural fatty acids may be saturated or unsaturated, and as the following data indicate, the saturated acids have higher melting points than unsaturated acids of corresponding size.

Protein (Biology)

Proteins

Proteins are macromolecules. They are constructed from one or more unbranched chains of amino acids, which is polymers. Proteins are the most diverse group of biologically important substances and are often considered to be the central compound necessary for life. In fact, the translation from the Greek root word means “first place.”

Amino Acids

Amino acids bonded together by the dehydration synthesis. By continually adding amino acids, called peptides, two amino acids join together to form dipeptides; as more peptides join together, they form polypeptides. Proteins vary in length and complexity based on the number and type of amino acids that compose the chain. There are about 20 different amino acids, each with a different chemical structure and characteristics. For instance, some are polar, others are non-polar.

Protein Structure

The first level, or primary structure, is the linear sequence of amino acids that creates the peptide chain. In the secondary structure, hydrogen bonding between different amino acids creates a three-dimensional geometry like an alpha helix or pleated sheet. An alpha helix is simply a spiral or coiled molecule, whereas a pleated sheet looks like a ribbon with regular peaks and valleys as part of the fabric. The tertiary structure describes the overall shape of the protein. Most tertiary structures are either globular or fibrous. Generally, nonstructural proteins such as enzymes are globular, which means they look spherical. The enzyme amylase is a good example of a globular protein. Structural proteins are typically long and thin, and hence the name, fibrous.

Enzyme (Biology)

Enzymes are biological molecules (proteins) that act as catalysts and to help complex reactions to occur everywhere in life. Proteases would go to work and help break down the peptide bonds between the amino acids. Enzymes take part in the reaction - that is how they provide an alternative reaction pathway. But they do not undergo permanent changes and so remain unchanged at the end of the reaction. They can only alter the rate of reaction, not the position of the equilibrium.

Lock and key hypothesis

This is the simplest model to represent how an enzyme works. The substrate simply fits into the active site to form a reaction intermediate.

Redox and Electrolysis (Chemistry)

Oxidation and reduction in terms of oxygen transfer

Definitions:

Oxidation is gain of oxygen

Reduction is loss of oxygen

Redox is a contraction of the name for chemical reduction-oxidation reaction. A reduction reaction always occurs with an oxidation reaction. Redox reactions include all chemical reactions in which atoms have their oxidation state changed; in general, redox reactions involve the transfer of electrons between chemical species. The chemical species from which the electron is stripped is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. Oxygen is not necessarily included in such reactions as other chemical species can serve the same function.

Electrolysis is the process by which ionic substances are decomposed (broken down) into simpler substances when an electric current is passed through them. For electrolysis to work, the ions must be free to move. Ions are free to move when an ionic substance is dissolved in water or when melted.

Here is what happens during electrolysis:

- Positively charged ions move to the negative electrode during electrolysis. They receive electrons and are reduced.

- Negatively charged ions move to the positive electrode during electrolysis. They lose electrons and are oxidized.

The substance that is broken down is called the electrolyte.

Chemical Bonding (Chemistry)

Chemical compounds are formed by the joining of two or more atoms. A stable compound occurs when the total energy of the combination has lower energy than the separated atoms.

Since opposite charges attract via a simple electromagnetic force, the negatively charged electrons that are orbiting the nucleus and the positively charged protons in the nucleus attract each other. An electron positioned between two nuclei will be attracted to both of them, and the nuclei will be attracted toward electrons in this position. This attraction constitutes the chemical bond.

Strong chemical bonding is associated with the sharing or transfer of electrons between the participating atoms. The atoms in molecules, crystals, metals and diatomic gases—indeed most of the physical environment around us—are held together by chemical bonds, which dictate the structure and the bulk properties of matter.

The two extreme cases of chemical bonds are:

-         Covalent bond: bond in which one or more pairs of electrons are shared by two atoms.

   Ionic bond: bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other.

Force (Physics)

Force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. When the interaction ceases, the two objects no longer experience the force. Forces only exist as a result of an interaction. 

Forces (interactions) between objects can be placed into two broad categories:

- Contact forces: are those types of forces that result when the two interacting objects are perceived to be physically contacting each other. Examples of contact forces include frictional forces, tension forces, normal forces, air resistance forces, and applied forces.

     - Forces resulting from action-at-a-distance: are those types of forces that result even when the two interacting objects are not in physical contact with each other, yet are able to exert a push or pull despite their physical separation. Examples of action-at-a-distance forces include gravitational forces. For example, the sun and planets exert a gravitational pull on each other despite their large spatial separation.

Dynamics (Physics)

Dynamics:

Dynamics is the name given to the rules of motion. It’s something that you would think would be one of the first things to be figured out, but wasn’t fully locked down until fairly recently. That being said the rules haven’t changed much and are fairly predictable, at least on large scales.

Scalar quantities:

·         - Have a magnitude only.

·         - Energy, Length, Mass, Speed, Temperature and Time are all scalar quantities.

Vector quantities:

·        -  Have both a magnitude and a direction

·         - Displacement, Force, Velocity, Acceleration and Momentum are all vector quantities.