Macromolecules - 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.

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.

Carbohydrates are known as sugars or saccharides. Virtually all carbohydrates end in the suffix "-ose," making them easy to identify. Ribose is a five-carbon sugar found in RNA. Some other common carbohydrates include deoxyribose, glucose, cellulose, and lactose. Sucrose is the technical name of table sugar, which is also a carbohydrate.

The other classes of molecules are fats, proteins, and nucleic acids. Fats, or lipids, can be further broken down into other categories, such as sterols and glycerolipids. Sterol lipids generally have the suffix "-ol" and include cholesterol and estradiol (estrogen). Glycerolipids include triglycerides. Proteins are formed from amino acids. Enzymes are a class of protein and generally have the suffix "-ase," such as helicase. Other proteins often have the suffix "-in" or "-en," such as insulin.

Lipids are hydrophobic, which means that they are insoluble in water, a polar solvent. Lipids can store abundant energy. Lipids contain large nonpolar regions, which means that they are soluble in nonpolar solvents. Triglycerides are only one type of lipids. Other types include, but are not limited to: monoglycerides, diglycerides, phospholipids, and fatty acids.

Maltose is a type of disaccharide that consists of two molecules of the monosaccharide glucose. Monosaccharides come together to produce a disaccharide and a molecule of water: condensation reaction. Polysaccharides include starch, glycogen, and cellulose. Starch is responsible for plant energy storage and includes amylose and amylopectin. Glycogen is used in animals for energy storage. Cellulose is a structural molecule utilized in plants.

Monosaccharides come together to produce a disaccharide and a molecule of water. Lactose is a disaccharide that consists of a molecule of the monosaccharides glucose and galactose. Maltose is a type of disaccharide that consists of two molecules of the monosaccharide glucose. Sucrose is a disaccharide that consists of a molecule of both the monosaccharides glucose and fructose.

Vitamins A, D, E, K are all fat-soluble vitamins. Fat-soluble vitamins are absorbed through the intestinal tract with the help of fat (i.e. lipids). Because these vitamins are not water-soluble they are not excreted in urine and thus are more likely to accumulate in the body, leading to hypervitaminosis (i.e. excess amounts of vitamins A, D, E, and K can lead to health consequences.). Vitamin C is water-soluble and is excreted in urine; therefore, regular intake is important.

Humans can obtain vitamins from a variety of mechanisms. Diet—consumption of food—is an intuitive resource that provides humans with vitamins; however, there are certain vitamins that are obtained by other means. Intestinal microorganisms help us produce both vitamin K (a fat soluble vitamin) and biotin. After exposure to sunlight’s natural ultraviolet light vitamin D is synthesized within the skin. Vitamin deficiencies can be very serious and include the following disorders: rickets, beriberi, scurvy, and night-blindness.

Cholesterol is the precursor to all steroid hormones. Cholesterol is used as a structural component in cell membranes. It is also a precursor for many hormones—including testosterone and progesterone—and vitamins. Cholesterol is involved in cell communication including: intracellular transport, cell signaling, and nerve conduction. There are two primary types of cholesterol: LDL and HDL.

Cellulose is a polysaccharide in which the monomers are linked by a beta linkage. This linkage requires a specialized enzyme that is not found in human beings. As a result, humans cannot break down cellulose.

Glycogen is used to store glucose in the body, and can be broken down to release energy. Starch is used to store glucose in plants, but can also be broken down by humans. Amylose is a component of starch.

Unlike carbohydrates and proteins, lipids are mainly nonpolar molecules. As a result, they are unable to be dissolved in aqueous solutions, such as blood. This makes them require a lipoprotein in order to be transported through the bloodstream. Without these proteins, lipids would be insoluble in the blood and cause clots.