OpenStax Chapter 3

Fats

A fat molecule consists of two main components—glycerol and fatty acids.

Unsaturated Fatty Acid

A hydrocarbon chain that contains a double bond. Most unsaturated fats are liquid at room temperature and are called oils. If there is one double bond in the molecule, then it is known as a monounsaturated fat (e.g., olive oil), and if there is more than one double bond, then it is known as a polyunsaturated fat (e.g., canola oil). Unsaturated fats help to lower blood cholesterol levels whereas saturated fats contribute to plaque formation in the arteries.

Saturated Fatty Acid

A hydrocarbon chain that contains all single bonds - meaning that each carbon is "saturated" with hydrogen. Saturated fatty acids tend to get packed tightly and are solid at room temperature. Olive oil, corn oil, canola oil, and cod liver oil are examples of unsaturated fats.

Polypeptides

A long protein polymer formed by amino acids binding together with peptide bonds. Polypeptides are the polymers of proteins.

Monomers

A monomer is a molecule that can bind with another molecule to make a polymer. Mono means single or one unit Poly means many An example of a monomer are monosaccharides (simple sugars like glucose) that can join together to make polysaccharides (complex sugars like starch).

Polymer

A polymer is a molecule that is made of two or more monomers.

Amino Acids

Amino acids are the monomers that make up proteins, meaning a protein is made of many amino acids bound together. Amino acids are made of an amino group and a carboxylic acid. There are 20 amino acids present in proteins. Ten of these are considered essential amino acids in humans because the human body cannot produce them and they are obtained from the diet. Each amino acid is attached to another amino acid by a covalent bond, known as a peptide bond, which is formed by a dehydration reaction.

Trans Fats

An increase in trans fats in the human diet may lead to an increase in levels of low-density lipoproteins (LDL), or "bad" cholesterol, which in turn may lead to plaque deposition in the arteries, resulting in heart disease. A good way to remember LDL being the "bad" cholesterol is to think of it as the "Lousy" cholesterol, whereas HDL is the "happy" cholesterol or "good" cholesterol.

Chitin

Carbohydrates serve various functions in different animals. Arthropods (insects, crustaceans, and others) have an outer skeleton, called the exoskeleton, which protects their internal body parts. This exoskeleton is made of the biological macromolecule chitin, which is a polysaccharide. Chitin is also a major component of fungal cell walls.

Cellulose

Cellulose is the most abundant natural biopolymer. The cell wall of plants is mostly made of cellulose. Cellulose is made up of glucose monomers.

DNA

DNA has a double-helix structure. The "backbone" of the DNA molecule are a sugar and a phosphate group. The rest of the DNA molecule is made up of nitrogenous bases. The two strands of the helix run in opposite directions, meaning that the 5′ carbon end of one strand will face the 3′ carbon end of its matching strand. For base pairing, A (adenine) can pair with T (thymine), and G (guanine) can pair with C (cytoseine). This is known as the base complementary rule. In other words, the DNA strands are complementary to each other. If the sequence of one strand is AATTGGCC, the complementary strand would have the sequence TTAACCGG. During DNA replication, each strand is copied, resulting in a daughter DNA double helix containing one parental DNA strand and a newly synthesized strand.

Denaturation

Denaturation is caused by changes in temperature, pH, and exposure to chemicals which leads to permanent changes in the shape of the protein, leading to loss of function.

Disaccharides

Disaccharides form when two monosaccharides undergo a dehydration synthesis reaction. When the two monomers are joined it forms a special type of covalent bond known as a glycosidic bond. Common disaccharides include lactose, maltose, and sucrose. Lactose is a disaccharide consisting of the monomers glucose and galactose. It is found naturally in milk. Maltose, or malt sugar, is a disaccharide formed by a dehydration reaction between two glucose molecules. The most common disaccharide is sucrose, or table sugar, which is composed of the monomers glucose and fructose.

Enzymes

Enzymes are catalysts in biochemical reactions. Each enzyme is specific for the substrate (a reactant that binds to an enzyme) it acts on. Enzymes that break down their substrates are called catabolic enzymes, enzymes that build more complex molecules from their substrates are called anabolic enzymes, and enzymes that affect the rate of reaction are called catalytic enzymes. It should be noted that all enzymes increase the rate of reaction (speeds up the reaction) and, therefore, are considered to be catalysts.

Fatty Acids

Fatty acids are the monomers that build lipids, meaning that you put many fatty acids together to build more complex lipids.

Glycogen

Glycogen is the storage form of glucose in humans and other vertebrates and is made up of monomers of glucose. Whenever blood glucose levels decrease, glycogen is broken down to release glucose in a process known as glycogenolysis.

Hormones

Hormones are usually small proteins or steroids, secreted by endocrine cells that act to control or regulate specific physiological processes, including growth, development, metabolism, and reproduction. For example, insulin is a protein hormone that helps to regulate the blood glucose level.

Lipids

Lipids include a diverse group of compounds that are largely nonpolar in nature. Cells store energy for long-term use in the form of fats. Lipids also provide insulation. Lipids are also the building blocks of many hormones and are an important component of all cellular membranes. Lipids include fats, oils, waxes, phospholipids, and steroids.

Phospholipids

Phospholipids are major constituents of the plasma membrane, the outermost layer of animal cells. A phospholipid is an amphipathic molecule, meaning it has a hydrophobic tail and a hydrophilic head.

Polysaccharides

Polysaccharides form when more than two monosaccharides undergo a dehydration synthesis reaction and are bound together by glycosidic bonds. Starch, glycogen, cellulose, and chitin are primary examples of polysaccharides. Starch is the stored form of sugars in plants and is made up of a mixture of amylose and amylopectin (both polymers of glucose).

Chaperones

Protein helpers known as chaperones (or chaperonins) help proteins properly fold into their 3-dimensional structure.

Proteins

Proteins may be structural, regulatory, contractile, or protective; they may serve in transport, storage, or membranes; or they may be toxins or enzymes.

Quaternary Structure

Quaternary structure is several tertiary structures folded together.

RNA

Ribonucleic acid, or RNA, is mainly involved in the process of protein synthesis. RNA is usually single-stranded and instead of using thymine as one of the nitrogenous bases, it instead uses uracil (U). There are four major types of RNA: messenger RNA (mRNA), ribosomal RNA (rRNA), transfer RNA (tRNA), and microRNA (miRNA). The first, mRNA, carries the message from DNA, which controls all of the cellular activities in a cell. Ribosomal RNA (rRNA) is a major constituent of ribosomes on which the mRNA binds. Transfer RNA (tRNA) is one of the smallest of the four types of RNA. It carries the correct amino acid to the site of protein synthesis.

Secondary Structure

Secondary structure is the folding together of several primary structures. The two secondary structures are the α-helix and β-pleated sheet. The helix looks like a spiral staircase, like a strand of DNA. The sheet looks like a flat sheet of paper.

Monosaccharides

Simple sugars, the most common of which is glucose. Depending on the number of carbons in the sugar, they also may be known as trioses (three carbons), pentoses (five carbons), and or hexoses (six carbons). Galactose and fructose are other common monosaccharides.

Tertiary Structure

Tertiary structure is a lot of folded secondary structures together and is a 3-dimensional structure. It can be a combination of folded alpha helices and beta pleated sheets. When a protein is denatured and loses this 3-dimensional structure then it no longer functions.

Carbohydrates

The ratio of carbon to hydrogen to oxygen is 1:2:1 in carbohydrate molecules. So glucose for example follows this formula: 6 Carbon 12 Hydrogen (twice as many hydrogen) 6 Oxygen Carbohydrates are classified into three subtypes: monosaccharides, disaccharides, and polysaccharides.

Nucleic Acids

The two main types of nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). DNA is the genetic material found in all living organisms. It is found in the nucleus of eukaryotes and in the organelles, chloroplasts, and mitochondria. In prokaryotes, the DNA is not enclosed in a membranous envelope. In eukaryotic cells but not in prokaryotes, DNA forms a complex with histone proteins to form chromatin, the substance of eukaryotic chromosomes (the DNA wraps itself around the histone proteins). The other type of nucleic acid, RNA, is mostly involved in protein synthesis. The DNA molecules never leave the nucleus but instead use an intermediary to communicate with the rest of the cell. This intermediary is the messenger RNA (mRNA). Other types of RNA—like rRNA, tRNA, and microRNA—are involved in protein synthesis and its regulation. The monomers that make up nucleic acids are known as nucleotides.

Primary Structure

The unique sequence of amino acids in a polypeptide chain is called its primary structure.

Biological Macromolecules

There are four major classes of biological macromolecules (carbohydrates, lipids, proteins, and nucleic acids). Combined, these molecules make up the majority of a cell's dry mass (recall that water makes up the majority of its complete mass). Biological macromolecules are organic, meaning they contain carbon. In addition, they may contain hydrogen, oxygen or nitrogen. Carbohydrates, Lipids and Proteins are all components of the plasma membrane (cell membrane).

Steroids

They do not resemble the other lipids, they are grouped with them because they are also hydrophobic and insoluble in water. Cholesterol is the most common steroid.

Hydrolysis

This reaction is one by which a polymer is broken down into two monomers by adding water. It is the opposite of the dehydration synthesis reaction. The word hydro means water and the word lysis means to burst open or break. So think of it this way, you are breaking down a polymer into two monomers by adding water to it.

Dehydration Synthesis

This reaction is one by which two monomers are bound together while releasing water from the molecule. This happens because when the two polymers connect to one another, it creates a water molecule. The word dehydration means to lose water and the word synthesis means to create. So think of it this way, you are creating a polymer, by connecting two monomers, while creating a molecule of water which gets released.

Wax

Wax covers the feathers of some aquatic birds and the leaf surfaces of some plants. Because of the hydrophobic nature of waxes, they prevent water from sticking on the surface by repelling water.