BIOLOGYINDEEP

A PYLOMERS


Polymers are large molecules composed of many similar smaller molecules linked together. The individual smaller molecules are called monomers. When small organic molecules are joined together, giant molecules are produced. These giant molecules are known as macromolecules.

Generally speaking, all macromolecules are produced from a small set of about 50 monomers. Different macromolecules vary because of the arrangement of these monomers. By varying the sequence, an incredibly large variety of macromolecules can be produced. While polymers are responsible for the molecular "uniqueness" of an organism, the common monomers mentioned above are nearly universal.

The variation in the form of macromolecules is largely responsible for molecular diversity. Much of the variation that occurs both within an organism and among organisms can ultimately be traced to differences in macromolecules. Macromolecules can vary from cell to cell in the same organism, as well as from one species to the next.
PYLOMER;BIOLOGICAL MACROMOLECULES
There are four basic kinds of biological macromolecules. They are carbohydrates, lipids, proteins and nucleic acids. These polymers are composed of different monomers and serve different functions.
1>CARLBOHYDRATES;
Carbohydrates are one of the four major classes of organic compounds in living cells. They are produced during photosynthesis and are the main sources of energy for plants and animals. The term carbohydrate is used when referring to a saccharide or sugar and its derivatives. Carbohydrates can be simple sugars or monosaccharides, double sugars or disaccharides, composed of a few sugars or oligosaccharides, or composed of many sugars or polysaccharides.
Carbohydrates: Monosaccharides

A monosaccharide or simple sugar has a formula that is some multiple of CH2O. For instance, glucose (the most common monosaccharide) has a formula of C6H12O6. Glucose is typical of the structure of monosaccharides. Hydroxyl groups (-OH) are attached to all carbons except one. The carbon without an attached hydroxyl group is double-bonded to an oxygen to form what is known as a carbonyl group. The location of this group determines whether or not a sugar is known as a ketone or an aldehyde sugar. If the group is not terminal then the sugar is known as a ketone. If the group is at the end, it is known as an aldehyde. Glucose is an important energy source in living organisms. During cellular respiration, the breakdown of glucose occurs in order to release its stored energy.
Carbohydrates: Disaccharides

Two monosaccharides joined together by a glycosidic linkage is called a double sugar or disaccharide. The most common disaccharide is sucrose. It is composed of glucose and fructose. Sucrose is commonly used by plants to transport sugar from one part of the plant to another. Disaccharides are also oligosaccharides. An oligosaccharide consists of a small number of monosaccaharide units (from about two to ten) joined together. Oligosaccharides are found in cell membranes and assist other membrane structures called glycolipids in cell recognition.
Carbohydrates: Polysaccharides

Polysaccharides can be composed of hundreds to thousands of monosaccharides combined together. These monosaccharides are joined together through dehydration synthesis. Some examples of polysaccharides include starch, cellulose and glycogen. Polysaccharides have several functions including structural support and storage.
2>LIPIDS;include fats, phospholipids and steroids. Lipids help to store energy, cushion and protect organs, insulate the body and form cell membranes.
Lipids are very diverse in both their respective structures and functions. These diverse compounds that make up the lipid family are so grouped because they are insoluble in water. They are however soluble in other organic solvents such as ether, acetone and other lipids. Major lipid groups include fats, phospholipids, steroids and waxes.
Lipids: Fats

Fats are composed of three fatty acids and glycerol. These triglycerides can be solid or liquid at room temperature. Those that are solid are classified as fats, while those that are liquid are known as oils. Fatty acids consist of a long chain of carbons with a carboxyl group at one end. Depending on their structure, fatty acids can be saturated or unsaturated. While fats have been denigrated to the point that many believe that fat should be eliminated from the diet, fat serves many useful purposes. Fats store energy, help to insulate the body and cushion and protect organs.
Lipids: Phospholipids

A phospholipid is composed of two fatty acids, a glycerol unit, a phosphate group and a polar molecule. The phosphate group and polar head region of the molecule is hydrophillic (attracted to water), while the fatty acid tail is hydrophobic (repelled by water). When placed in water, phospholipids will orient themselves into a bilayer in which the nonpolar tail region faces the inner area of the bilayer. The polar head region faces outward and interacts with the water. Phospholipids are a major component of cell membranes which enclose the cytoplasm and other contents of a cell.
Lipids: Steroids and Waxes

Steroids have a carbon backbone that consists of four fused ring-like structures. Steroids include cholesterol, sex hormones (progesterone, estrogen and testosterone) and cortisone. Waxes are comprised of an ester of a long-chain alcohol and a fatty acid. Many plants have leaves and fruits with wax coatings to help prevent water loss. Some animals also have wax-coated fur or feathers to repel water. Unlike most waxes, ear wax is composed of phospholipids and esters of cholesterol.
3>PROTEIN;composed of amino acid monomers and have a wide variety of functions including molecular transport and muscle movement.
Proteins are very important molecules in cells. By weight, proteins are collectively the major component of the dry weight of cells. They can be used for a variety of functions from cellular support to cellular locomotion. While proteins have many diverse functions, all are typically constructed from one set of 20 amino acids.
Amino Acids

Most amino acids have the following structural properties:

A carbon (the alpha carbon) bonded to four different groups:
A hydrogen atom (H)
A Carboxyl group (-COOH)
An Amino group (-NH2)
A "variable" group
Of the 20 amino acids that typically make up proteins, the "variable" group determines the differences among the amino acids. All amino acids have the hydrogen atom, carboxyl group and amino group bonds.
Polypeptide Chains

Amino acids are joined together through dehydration synthesis to form a peptide bond. When a number of amino acids are linked together by peptide bonds, a polypeptide chain is formed.
Proteins

One or more polypeptide chains twisted into a 3D shape forms a protein. The unique shape of the protein determines its function. For instance, structural proteins such as collagen and keratin are fibrous and stringy. Globular proteins like hemoglobin, on the other hand, are folded and compact.
Protein Synthesis

Proteins are synthesized in the body through a process called translation. Translation occurs in the cytoplasm and involves the translation of genetic codes that are assembled during DNA transcription into proteins. Cell structures called ribosomes help translate these genetic codes into polypeptide chains that undergo several modifications before becoming fully functioning proteins.
4>NUCLEIC ACIDS;include DNA and RNA. Nucleic acids contain instructions for protein synthesis and allow organisms to transfer genetic information from one generation to the next.
Nucleic acids allow organisms to transfer genetic information from one generation to the next. There are two types of nucleic acids: deoxyribonucleic acid, better known as DNA and ribonucleic acid, better known as RNA.

When a cell divides, its DNA is copied and passed from one cell generation to the next generation. DNA contains the "programmatic instructions" for cellular activities. When organisms produce offspring, these instructions, in the form of DNA, are passed down. RNA is involved in the synthesis of proteins. "Information" is typically passed from DNA to RNA to the resulting proteins.Nucleic acids: Nucleotides

Nucleic acids are composed of nucleotide monomers. Nucleotides have three parts:
A Nitrogenous Base
A Five-Carbon Sugar
A Phosphate Group
Similar to what happens with protein monomers, nucleotides are linked to each other through dehydration synthesis. Interestingly, some nucleotides perform important cellular functions as "individual" molecules, the most common example being ATP.In polynucleotides, nucleotides are joined to one another by covalent bonds between the phosphate of one and the sugar of another. These linkages are called phosphodiester linkages.

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