biochem 3

• Phosphate groups alternate with pentose sugars to form the backbone of a DNA strand, with the bases pointing inward from the backbone chain.
• DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are types of nucleic acids, which are chains of repeating monomers called nucleotides.
• The four nitrogenous bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G).
• Each nucleotide of DNA consists of three parts: nitrogenous base, pentose sugar, and phosphate group.
• A five carbon sugar called deoxyribose attaches to each base in DNA.
• Carbohydrates include sugar, glycogen, starch and cellulose.
• Monomers are simple compounds whose molecules can join together to form polymers.
• Disaccharides are formed by combining two monosaccharides by dehydration synthesis, are simple sugars, and examples include molecules of the monosaccharides glucose and fructose combined to form a molecule of the disaccharide sucrose.
• Lipids are biomolecules that are soluble in organic solvents and insoluble in water, made from atoms of carbon, hydrogen, and oxygen.
• The ratio of hydrogen to oxygen atom in carbohydrates is usually 2:1, the same as in water.
• Carbohydrates represent only 2-3% of our total body mass.
• Polymers are large molecules formed by the covalent bonding of many identical small building block molecules.
• Examples of monosaccharides include trioses, tetroses, pentoses, hexoses and heptoses.
• Polysaccharides are formed by combining many monosaccharides into long chains which may branch profusely, are usually insoluble in water and do not taste sweet.
• Macromolecules are small organic molecules that combine into very large molecules.
• In humans and animals, carbohydrates function mainly as a source of chemical energy for generating ATP needed to drive metabolic reactions.
• The reaction of two monomers is a dehydration synthesis wherein a hydrogen atom is removed from one monomer and a hydroxyl group is removed from the other monomer to form a molecule of water.
• Major carbohydrate groups include Monosaccharides, Disaccharides, and Polysaccharides.
• Monosaccharides are the simplest form of carbohydrates, because they cannot hydrolyze anymore, contain from 3 to 7 carbon atoms, and are designated by names ending in -ose with a prefix that indicates the number of carbon atoms.
• Carbohydrates are considered important sources of energy and compose of elements carbon, hydrogen, and oxygen.
• A carbon atom has four electrons in its valence shell and to become stable, it will form four covalent bonds to fill its outer valence shell.
• These bonds may be with other carbon atoms or with other elements such as hydrogen and oxygen.
• When two carbon atoms form a covalent bond, each atom can share one, two, or three electrons to form a single, double, or triple bond.
• Carbon atoms bond to each other in different ways to form compounds of various shapes including straight-chain, branch-chain, or ring compounds (closed chain).
• These compounds can have any number of carbon atoms and will contain atoms of other elements, the most frequently occurring of which is hydrogen.
• Carbon is the central element in all biomolecules and it has four outer shell electrons (valence = 4).
• Once bound to other elements, carbon is very stable.
• Alcohols contain an -OH group, which is polar and hydrophilic due to its electronegative O atom.
• Esters predominate in dietary fats and oils and also occur in our body triglycerides.
• Thiols have an -SH group, which is polar and hydrophilic due to its electronegative S atom.
• Some amino acids contain -SH groups, which help stabilize the shape of atoms.
• Phosphates contain a phosphate group, which is very hydrophilic due to the dual negative charges.
• Ketones contain a carbonyl group within the carbon skeleton.
• Aldehydes have a carbonyl group at the end of the carbon skeleton.
• Amines have an -NH2 group, which can act as a base and pick up a hydrogen ion, giving the amino group a positive charge.
• All amino acids have an amino group at one end.
• Carboxylic acids contain a carboxyl group at the end of the carbon skeleton.
• Antibodies are proteins that defend against invading microbes.
• Other proteins work as “motors” to drive muscle contraction.
• Proteins are large molecules that contain carbon, hydrogen, oxygen, and nitrogen, are much more complex and structured than carbohydrates or lipids, and have many roles in the body and are largely responsible for the structure of body tissues.