What is a Chemical Element?

Answer:

A chemical element, or an element, is a material which cannot be broken down or changed into another substance using chemical means. Elements may be thought of as the basic chemical building blocks of matter. Depending on how much evidence you require to prove a new element has been created, there are 117 or 118 known elements.

All substances consist of matter. Matter is anything which has mass and takes up space. Some important concepts to remember about matter are:

• Matter is made up of one or more of over 92 naturally-occurring elements.

• Each element is a pure substance, made up of only one type of atom.

Chemical bonds

compound is a combination of two or more chemically-bonded elements.

• IONIC BONDS

• COVALENT BONDS

• HYDROGEN BONDS

• In ionic bonds, electrons are actually transferred from one atom to another. Such attoms or aggregates of atoms are then called ions. The atom gaining an electron or electrons becomes negatively charged, called an anion. The atom which loses electrons becomes positively charged, called a cation. Since oppositely charged particles attract each other, oppositely charged ions can be held together by this attraction to form electrically neutral ionic compounds. Such attracttions are called IONIC BONDS.

• In covalent bonds, atoms share electrons in their outer energy level. If one pair of electrons are shared (e.g. H2) a SINGLE covalent bond is formed. Two pairs shared (e.g O2) form a DOUBLE bond. Three pairs (e.g. N2) a TRIPLE bond. Shared electrons, attracted equally to both atoms, as with H2, form a NON-POLAR COVALENT BOND. However, if one atom attracts the shared electrons more strongly than the other, the bond is a POLAR COVALENT BOND and produces polar molecules with positive and negative areas. Water is a polar molecule.

• Oppositely charged regions of polar molecules can attract one another. Such a bond between hydrogen and e.g. Oxygen or nitrogen is called a HYDROGEN BOND. These occur in water, proteins and other large molecules but are weak bonds (5% as strong as covalent bonds). However, large molecules may contain many H-bonds, e.g. between bases in DNA and can thus give strength and three-dimensional shape to, e.g proteins and nucleic acids.

Which chemical elements make up the most protoplasmic material?

Protoplasm is the viscid, translucent, polyphasic colloid with water as the continuous phase that makes up the essential material of all cells. It is composed mainly of nucleic acids, proteins, lipids, carbohydrates, and inorganic salts. The protoplasm surrounding the nucleus is known as the cytoplasm and that composing the nucleus is the nucleoplasm (also called karyoplasm).

Function of rna

The function of rna Ribonucleic acid is conveys /konvejs/ genetic information and catalyzes important biochemical reactions. There are three types of rna: messenger RNA (mRNA) is the RNA that carries information from DNA to the ribosome; transfer RNA (tRNA) and ribosomal RNA (rRNA), both of which are involved in the process of translation.

Describe the structure and functions of the cell membrane.

The plasma membrane is formed from a double layer of lipids and proteins and composes the cell's outer membrane. It surrounds the protoplasm of the cell and helps maintain its shape and structure. The plasma membrane separates each cell from its environment. The function of the plasma membrane is to regulate active transport. This process selectively allows certain substances to enter and leave the cell while barring others. It also sends and receives chemical and electrical messages, including signals for the cell to manufacture proteins or to divide.

Catabolism and anabolism

Catabolism is the set of metabolic pathways that breaks down molecules into smaller units to release energy. and anabolism is reverse procese when smaler units becoming biger one and the reactione require energy. And its take place in all organism and provide to individual to grow up, to decompose sugars, proteines, lipids in to a smaller units such as amino acids, fatty acids, nucleotides...

Function and structure of the cell nucleus

The nucleus is enclosed in a double layer of nuclear membrane. At numerous points these membranes are joined, forming the rims of circular openings, the water filled nuclear pores, through which large molecules e.g. ribonucleic acid (RNA) can pass in and out of the nucleus.

• The nucleolus contains the DNA coding. The function of DNA (Deoxyribonucleic acid) is to pass on the characteristics of one generation of cells to the next. The DNA is contained by a number of chromosomes, which consist of long strands of DNA tightly wound into coils with proteins called histones. The combination of DNA and histone proteins is known as chromation. The nucleolus also controls the synthesis of some of the cell's RNA.

DNA?

The function of DNA (Deoxyribonucleic acid) is to pass on the characteristics of one generation of cells to the next. The DNA is contained by a number of chromosomes, which consist of long strands of DNA

tightly wound into coils with proteins called histones. The combination of DNA and histone proteins is

known as chromation.