Introductory Topics - Biology

There are four classes of biological molecules: fats, carbohydrates, proteins, and nucleic acids. Of these, fats produce the most energy per gram at a whopping nine calories per gram. Carbohydrates and proteins produce less than half of this, at only four calories per gram.

The R group is a side chain connected to the central carbon atom in an amino acid. The central carbon atom of an amino acid can bind to four other groups. In an amino acid, the central carbon will always bind to a carboxyl group, and amine group, and a hydrogen atom. The fourth bond, however, will be different for each amino acid, linking the central carbon to the R group.

Waxes provide skin with a waterproof coating. Waxes are made out of fats.

Hemoglobin is a protein responsible for transporting oxygen. DNA polymerase repairs DNA molecules. Amylase is the protein that helps convert starch to glucose.

Phospholipids are a type of complex lipid. They consist of a glycerol, two fatty acids, and a polar phosphate group with an alcohol. Their function is to create cell membranes, specifically the fluid mosaic model. They have a polar "head" and a non-polar "tail." The head is hydrophilic ("water loving"), and the tail is hydrophobic ("water hating"), making it perfect for making membranes.

DNA is composed of three key components. The backbone of the molecule is made of deoxyribose sugars and phosphate groups. The coding region of DNA is composed of the nitrogenous bases: adenine, thymine, cytosine, and guanine.

A single subunit of DNA is composed of one deoxyribose, one phosphate, and one nitrogenous base. This subunit is called a nucleotide.

A nucleoside is a nucleotide without a phosphate group: only a deoxyribose sugar and a nitrogenous base.

Amino acids are the subunit for proteins, and are not found in DNA.

Proteins are composed of amino acids linked together by peptide bonds. Nucleic acids are linked by phosphodiester bonds and polysaccharides are held together by glycosidic linkages. Lipid polymers are linked by simple covalent bonds.

In DNA, guanine will always pair with cytosine (C-G) and adenine will always pair with thymine (A-T). In RNA, thymine is replaced with the pyrimidine uracil, meaning that adenine will pair with uracil in RNA (A-U). Guanine and uracil will never be paired together.

Lipids, or fats, are formed from hydrocarbon chains. The carbon atoms link together and bond to hydrogen to fill their orbitals. When all the bonds in the molecule are single bonds, the lipid is saturated. There is no such thing as a "di-saturated fat."

When there is a single double bond in the chain, the lipid is mono-unsaturated. When there are multiple double bonds in the chain, the lipid is unsaturated. Trans fats have a double bond with the adjacent hydrogen atoms on opposite sides of the carbon chain, maintaining a linear structure.

Most fats in the body are triglycerides. Their primary function is long-term energy storage.

Proteins are made up of a string of amino acids. Ribosomes are responsible for facilitating the formation of covalent peptide bonds between amino acids to build the polypeptide chain. Proteins called chaperones then help fold the protein into the proper shape.

Nucleotides are found in DNA and ribonucleotides are found in RNA. Nucleosomes are small regions of DNA that are tightly wound around histone proteins. Phosphates are functional groups made of one phosphorus atom and four oxygen atoms. Phosphates are found in numerous molecules, including DNA, RNA, and phospholipids in the cell membrane, but are not generally found in proteins.

The question states that the pump transports ions against their concentration gradient. This means that this pump must use active transport. Recall that active transport requires energy in the form of ATP. ATP, or adenine triphosphate, is a type of nucleotide because it contains a nitrogenous base, a pentose sugar, and phosphate groups.

Lipids and carbohydrates (such as glucose) are the energy source for the body; however, these macromolecules themselves do not provide energy for cellular processes. They undergo metabolism and generate ATP, the molecule used by cellular processes that require energy.

All proteins have at least a primary, secondary, and tertiary structure, but only some, such as hemoglobin, have a quaternary structure. Secondary structures are determined by hydrogen bonding between different amino acids in the polypeptide chain that form the primary structure. There may be multiple and different secondary structures in a single protein.

Amino acids link together by peptide bonds to form proteins. Nucleotides link together to form nucleic acids like DNA and RNA. Monosaccharides are sugars that form links to form carbohydrates. Fatty acids attach to a glycerol backbone to form lipids, except those that are derived from cholesterol.

Phosphorous is found in nucleotides, but not amino acids. In certain reactions, proteins can be modified by kinases to contain phosphate groups. Kinases are enzymes that catalyze the transfer of phosphate groups onto substrates. They function in signal transduction pathways.

There are only a few residues (amino acids in proteins) which can be phosphorylated: Serine, threonine, tyrosine, histidine, arginine, and lysine.

Organic compounds are defined as solids, liquids, or gases whose molecular structure includes carbon. Inorganic compounds, in contrast, do not contain carbon. Organic compounds might contain other elements, like hydrogen and oxygen, but not all compounds need these other elements to be considered organic.

In the water cycle, there are abiotic and biotic factors that contribute to the recycling of water. The process by which non-living things return water to the atmosphere is called evaporation. Plants, on the other hand, intake water through their roots and release the water as vapor through tiny openings on leaves called stomata. This process is called transpiration.

Molecules that are hydrophobic or "water fearing" will have a hard time dissolving in an aqueous solution. Lipids, which are nonpolar molecules, would not be able to dissolve in water.

Proteins are synthesized through dehydration synthesis reactions, which is the removal of water between two amino acids. In this case, two hydrogen atoms are removed from the amine group and one oxygen is removed from the carboxyl group, forming a peptide bond between the carbon atom of one amino acid and the nitrogen atom of the other amino acid.

The sequence of amino acids is called a protein's primary structure. Each protein has a unique sequence of amino acids. A difference of just one amino acid in a chain of hundreds can be deadly to the organism. For example, mutation leading to a single amino acid change is responsible for sickle cell anemia.

A helix is formed when Hydrogen bonds occur between the amino group in one peptide bond and the carboxyl group of another in the same polypeptide chain.