Biology 1000 Chapter 2 Notes
Biology 1000 Chapter 2 Notes Bio 1000
Popular in Biology
Popular in Biology
verified elite notetaker
verified elite notetaker
verified elite notetaker
verified elite notetaker
verified elite notetaker
verified elite notetaker
This 6 page Class Notes was uploaded by Meagan Womble on Saturday August 27, 2016. The Class Notes belongs to Bio 1000 at Auburn University Montgomery taught by Penny Ragland in Fall 2016. Since its upload, it has received 42 views. For similar materials see Biology in Biology at Auburn University Montgomery.
Reviews for Biology 1000 Chapter 2 Notes
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 08/27/16
Biology Notes Chapter 2 **PAY ATTENTION TO KEY TERMS** ALL KEY TERMS ARE TYPED IN RED AND BOLDED All organisms consist of the same kinds of molecules, but small differences in the way those molecules are put together can have a big effect. Even though atoms are about 20 million times smaller than a grain of sand, they consist of even smaller subatomic particles. o Protons which are positively charged subatomic particles that occur in the nucleus of all atoms. o Neutrons which are uncharged subatomic particles in the atomic nucleus. The nucleus is the core of an atom that is occupied by proton and neutrons. Negatively charged electrons move around the nucleus. o Electrons are negatively charged subatomic particles. Charge is an electrical property. o Opposite charges attract while like charges repel. A normal atom has about the same number of protons and electrons. The negative charge of an electron is the same magnitude as the positive charge of a proton, so the two charges cancel one another out. This results to an atom with the same number or protons and electrons carrying no charge. All atoms have protons. The number of protons in the nucleus is called the atomic number, and it determines the type of atom or element. Elements are pure substances, each consisting of only atoms with the same number of protons in their nucleus. All atoms with six protons in their nucleus are carbon atoms, no matter how many electrons or neutrons they have. All atoms of an element had the same number of protons, but they can differ in the number of other subatomic particles. Isotopes are forms of an element that differ in the number of neutrons their atom carries. The total number of neutrons and protons in the nucleus of an isotope is its mass number. The most common carbon isotope has six protons and 6 neutrons. A radioisotope is an isotope with an unstable nucleus that breaks up spontaneously. Radioactive decay is the process by which atoms of a radioisotope emit energy and subatomic particles when their nucleus spontaneously breaks up. The atomic nucleus cannot be altered by ordinary means, so radioactive decay is unaffected by external factors such as temperature, pressure, or whether the atoms are part of molecules. Each radioisotope decays at a predictable rate into predictable products. Radioisotopes are often used in tracers, which are substances with a detectable component. When delivered into a biological system, a radioactive tracer may be followed as it moves through the system with instruments that detect radiation. An electron has mass but no size, and its position in space is described as more of a smudge than a point. It carries energy, but only in incremental amounts. An electron also gains energy only by absorbing the precise amount needed to take it to the next energy level. Likewise, it loses energy only by emitting the exact difference between two energy levels. A shell model is a model of electron distribution in an atom. The shell model helps us to visualize how electrons populate atoms. In this model, nested “shells” correspond to successively higher energy levels. We draw a shell model of an atom by filling it with electrons from the innermost shell. Once the innermost shell is full then we move outwards until there are as many electrons as the atom has protons. When an atom’s outermost shell is filled with electrons, it is said to have no vacancies and it is in its most stable state. Helium, neon, and argon are examples of elements with no vacancies. Atoms of these elements are chemically stable, which means they have very little tendency to interact with each other. As a result, these elements occur most frequently in nature as solitary atoms. When an atom has a vacancy they are considered chemically active because they are “searching” for more or another atom to bond with. Electrons really like to be in pairs when they populate atoms. Atoms that have unpaired electrons are called free radicals. With few exceptions, free radicals are very unstable, easily forcing electrons among other atoms or ripping electrons away from them. This property makes free radicals dangerous to life. Atoms with an unequal number of protons and electrons are ions. An ion carries a net, or overall, charge. A chemical bond is an attractive force that arises between two atoms, and it is one way that atoms rid themselves of vacancies. Chemical bonds make molecules out of atoms. A molecule consists of atoms held together in a particular number and arrangement by chemical bonds. A compound is a molecule that has atoms of more than one element. The term “bond” applies to a continuous range of atomic interactions. However, we can categorize most bonds into distinct types based on their different properties. Which type forms depends on the atoms taking part in the molecule. Ionic bond is a type of chemical bond in which a strong mutual attraction links ions of opposite charge. They can be quite strong. Ion returns their respective charges when participating in an ionic bond. One “end” of an ionically bonded molecule has a positive charge, and the other “end” has a negative charge. Any such separation of charge into distinct positive and negative regions called polarity. In a covalent bond, two atoms share a pair of electrons, so each atom’s vacancy becomes partially filled. Sharing electrons links atoms together. Covalent bonds can be stronger than ionic bonds but not always. Two or more electrons form between atoms then they share multiple pairs of electrons. Atoms share electrons unequally in a polar covalent bond. All living organisms are mostly water, many of them still live in it, and all of the chemical reactions of life are carried out in waterbased fluids. Water has unique properties that arise from the two polar covalent bonds in each water molecule. Overall, the molecule has no charge, but the oxygen atom carries a slight negative charge, and the two hydrogen atoms carry a slight positive charge. This results in the molecule itself being polar. The polarity of individual water molecules is what attracts them to one another. A hydrogen bond is an attraction between a covalently bonded hydrogen atom and another atom taking part in a separate polar covalent bond. Like iconic bonds, hydrogen bonds form by the mutual attraction of opposite charges. However, unlike ionic bonds, hydrogen bonds do not make molecules out of atoms, so they are not chemical bonds. The polarity of the water molecule ad its ability to form hydrogen bonds make water an excellent solvent. A solvent is a liquid in which other substances dissolve. Substances that dissolve easily in water are hydrophilic, or water loving. Hydrogen bonds among many water molecules are collectively stronger than an ionic bond between two ions. Solute is a dissolved substance. Salt is an ionic compound that releases ions other than H+ or OH when it is dissolves in water. A uniform mixture such as such that dissolves in water is called a solution. Chemical bonds do not form between molecules of solute and solvent, so the proportions of the two substances in a solution can vary. The amount of solute that is dissolved in a given volume of fluid is its concentration. Many nonionic solids also dissolve easily in water. Water does not interact with hydrophobic substances such as oils. Hydrophobic describes a substance that resists dissolving in water. Oil consists of nonpolar molecules, and hydrogen bonds do not form between nonpolar molecules and water. Molecules of some substances resist separating from one another, and the resistance gives rise to a property called cohesion. Water has cohesion because hydrogen bonds collectively exert a continuous pull on its individual molecules. Cohesion is a part of many processes that sustain multicelled bodies. Evaporation is the process in which molecules escape from the surface of a liquid and becomes vapor. Evaporation of water is resisted by hydrogen bonds among individual water molecules. This requires a lot of energy in order for water to be evaporated. All atoms jiggle nonstop, so the molecules they make up jiggle as well. We measure the energy of this motion as degrees of temperature. Adding energy makes the jiggling faster so as a result the temperature rises. Temperature stability is an important part of homeostasis because most of the molecules in life function properly only between a certain range of temperature. Below 32 degrees F, water molecules do not jiggle enough to break hydrogen bonds between them, and they become locked in the rigid, latticelike bonding pattern of ice. A hydrogen atom is just a proton and an electron. When a hydrogen atom participates in polar covalent bond, the electron is pulled away from the proton just a bit. Hydrogen bonding in water tugs on that proton even more, so much that the proton can be pulled right off of the molecule. A water molecule can temporarily lose an ion but with other molecules, the loss of a hydrogen ion is essentially permanent. We use a value called pH to measure the number of hydrogen ions in a waterbased fluid. A pH of 7 is neutral and the higher the number of hydrogen ions the lower the pH whereas the lower the number of hydrogen ions the higher the pH. An acid is a substance that gives up hydrogen ions in water. Acids can lower the pH of a solution and make it acidic (below pH 7). Bases accept hydrogen ions from water so they can raise the pH of the solution and make it basic (above pH 7). Under normal circumstances, fluid inside cells and bodies stay within a certain range of pH because they are buffered. A buffer is a set of chemicals that can keep pH stable by alternately donating and accepting ions that affect pH. Any buffer can neutralize only so many ions. Even slightly more than that limit can drastically change the pH level. The same elements that make up a living body also occur in nonliving things as well, but the proportions are different. Unlike sand or seawater, a body contains a lot of the molecules of life – complex carbohydrates and lipids, proteins, and nucleic acids – and these molecules consist of a high proportion of carbon atoms. Compounds that consist of primarily carbon and hydrogen atoms are called organic. Organic describes a compound that consists mainly of carbon and hydrogen atoms. We know that organic compounds ere present on Earth long before organisms were. Carbon’s importance to life rises from it versatile behavior. Carbon has four vacancies in its outer shell, so it can form four covalent bonds with many different atoms, including other carbon atoms. Many organic compounds have a carbon chain and this backbone forms rings. Small molecular groups that attach to the backbone impart chemical properties to make the molecule. Carbon’s ability to form chains and rings, and also to bond with many other elements mean that atoms of this element can be assembled into a wide variety of organic compounds. The function of the organic molecule depends on its structure. All biological systems are based on the same organic molecules, but the details differ among the organisms. Just as atoms bonded in different numbers and arrangements form different molecules, so does organic atoms. Cells assemble complex carbohydrates, lipids, proteins, and nucleic acid from small organic molecules. The small organic molecules – sugars, fatty acids, amino acids, and nucleotides – are called monomers when they are used as subunits of larger molecules. A molecule that consist of multiple monomers is a polymer. Cells build polymers from monomers and break down polymers to release monomers. These and other processes of molecular change are called reactions. Cells constantly run reactions as they acquire and use energy to stay alive, grow, and reproduce. Metabolism is all the enzymemediated chemical reactions by which cells acquire and use energy as they build and break down organic molecules. Metabolism also requires enzymes which are organic molecules that speed up a reaction without being changed by it. A common reaction called condensation is where an enzyme covalently bonds two monomers together. In hydrolysis, the reverse of condensation, an enzyme splits an organic polymer into its component monomers. A carbohydrate is an organic compound that consists of carbon, hydrogen, and oxygen in a ratio of 1:2:1. The term can apply to sugar molecules or a polymer of them, so these compounds are called saccharides (sugar). Monosaccharides (one sugar) are the simplest carbohydrates, and common types have a backbone of 5 or 6 carbon atoms. Disaccharides are two sugars. Monosaccharides and disaccharides are very soluble in water, so they move easily through the waterbased internal environments of all organisms. Breaking bonds of monosaccharide releases energy that can be harnessed to power other reactions. They are also remodeled into other important compounds. Foods that we call “complex” carbohydrates consists mainly of polysaccharides, which are chains of hundreds or thousands of monosaccharides monomers. The most common polysaccharides are cellulose, starch, and glucose. All consist only of glucose monomers, but as substances their properties are very different. Cellulose, the major structural material of plants, is the most abundant organic molecule on earth. Cellulose is the tough, insoluble carbohydrate that is the major structural material in plants. Hydrogen bonding locks its long straight chains of covalently bonded glucose monomer into tight, sturdy bundles. The bundles form tough fibers that act like reinforcing rods inside stems and other plant parts. Cellulose is insoluble in water and is not easily broken down. Dietary fiber usually refers to the indigestible cellulose in our vegetable foods. Animals store sugars in the form of glycogen, a polysaccharide that consists of highly branched chains of glucose monomers. Muscle and liver cells contain most of the body’s glycogen. In starch, a different covalent bonding pattern between glucose monomers makes a chain that coils up into a spiral. Starch does not dissolve in water. Humans have hydrolysis enzymes that break down starch. Animals store sugar in the form of glycogen, a polysaccharide that consists of highly branched chains of glucose monomers. Lipids are fatty, oily, or waxy organic compounds. They do vary in structure but they all are hydrophobic. Many lipids incorporate fatty acids, which are small organic molecules that consist of a carbon chain “tail” of variable length, and a carboxyl group “head”. The tail is hydrophobic while the head is hydrophilic. Saturated fatty acids have only single bonds linking the carbons in their tails (aka hydrogen atoms). The tail is flexible and it wiggles freely. However, double bonds between carbons limit the flexibility of the tails of an unsaturated fatty acid. These bonds are cis or trans, depending on the way the hydrogens are arranged around them. The carboxyl group head of the fatty acid can easily form a covalent bond with another molecule. When it bonds to a glycerol it loses its hydrophilic character. Three fatty acids bonded to the same glycerol form a triglyceride, a molecule that is entirely hydrophobic. Most abundant and richest energy source in vertebrate bodies. They store more energy than carbohydrates. A fat is a substance that consists mainly of triglycerides. Triglycerides are commonly called saturated fats. A phospholipid has two fatty acid tails and a head that contains a phosphate group. The tails are hydrophobic, but the phosphate group is highly polar and it makes the head very hydrophilic. These opposing properties give rise to the basic structure of the cell membranes, which consists mainly of phospholipids. In a cell membrane, phospholipids are arranged in two layers – lipid bilayer. A wax is a complex, varying mixture of lipids with long fatty acid tails bonded to carbon rings or other structures. These molecules pack tightly, so waxes are firm and water repellent. Other types of waxes protect, lubricate, soften skin and hair. Steroids are lipids with no fatty acid tails; they have a rigid backbone that consists of twenty carbon atoms arranged in a characteristic pattern of four rings. Proteins are polymers of amino acids; an organic molecule that consists of one or more polypeptides. An amino acid is a small organic compound with an amine group, a carboxyl group, and a side chain called “R group” that defines the kind of amino acid. The covalent bonds that links amino acids in a protein is called a peptide bond. Protein synthesis. Carbohydrates, lipids, or both may get attached to a protein after synthesis. A protein with carbohydrates attached to it is called a glycoprotein. Protein shaped depends on hydrogen bond and other interactions that heat, some salts, shift in pH, or detergents can disrupt. Such disruption can cause proteins to their lose their threedimensional shape, or denature. Once a proteins shape unravels, so does it function. For a very few proteins, denaturation is reversible if normal conditions return. Prion is an infectious protein. Resists denaturation. Nucleotides are small organic molecules that function as energy carriers, enzyme helpers, chemical messengers, and subunits of DNA and RNA. Each consists of a monosaccharide ring bonded to a nitrogencontaining base and one, two, or three phosphate groups. The monosaccharides is a fivecarbon sugar, either ribose or deoxyribose, and the base is one of five compounds with a flat ring structure. When the third phosphate of nucleotide is transferred to another molecule, energy is transferred along with it. ATP is a nucleotide monomer of RNA. It also serves an important role as an energy carrier in cells. Nucleic acids are chains of nucleotides in which the sugar of one nucleotide is joined to the phosphate group of the next (RNA and DNA). RNA is ribonucleic acid. It is nucleic acid that consists of a chain of nucleotides. It carries out synthesis. An RNA molecule is a chain of four kinds of nucleotide monomers. There are many types of RNA, and they work together to carry out protein synthesis. DNA is deoxyribonucleic acid. It is nucleic acid that consists of two chains of nucleotides twisted into a double helix. It holds hereditary information. A DNA molecule consists of two chains of nucleotides twisted into a double helix. Hydrogen bonds hold the chains together. Each cell starts life with DNA inherited from a parent cell.
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'