Clep Biology

If molecular weight is the addition of the atomic masses in a molecule, the weight of glucose (C6H12O6) is ___.

180. Carbon (6x12), Hydrogen (12x1) and Oxygen ( 16x6) = 72+12+96 = 180. When you have a stable molecule, you can usually just double the atomic number for each element to get its approximate atomic mass. Carbon has an atomic number of 6, which means an atomic mass of 12.

Proteins constitute about 80 percent of the dry weight of muscle, __ percent of that of skin, and 90 percent of that of blood.

70. Their building block is the amino acid, which has an amino end (NH2) and a carboxyl end (COOH). Proteins are sometimes referred to as macromolecular polypeptides because they are very large molecules and because the amino acids of which they are composed are joined by peptide bonds.

DNA is not simply crammed into the nucleus; it is organized, by molecular interaction with specific nuclear ________, into a precisely packaged structure, creating a dense, compact fiber called chromatin

Proteins. An extreme example of the ordered folding and compaction that chromatin can undergo is seen during cell division, when the chromatin of each chromosome condenses and is divided between two daughter cells.

....are the building blocks of proteins.

Amino acids. They have what is called an amino group at one end, which is -NH2, and a carboxyl group (-COOH) at the other end. These amino acids are joined by peptide bonds to form proteins

The polarity of the water molecule plays a major part in the formation of _______ solutions. If an ionic compound, such as sodium chloride, is placed in water, the polar water molecules reduce the electrostatic attraction between the positively charged sodium and negatively charged chloride ions.

Aqueous . Water dissolves the sodium chloride (salt), and the ions then become hydrated, or surrounded by water molecules. As a result, their charge is effectively dispersed over a larger structure, and this keeps the sodium and chloride from recombining.

The mass of particles within an atom are measured in ___________ Units (a.m.u.).

Atomic mass

The ______ number of an element is the number of protons contained in its nucleus.

Atomic. For example, oxygen has 8 protons in its nucleus, so its atomic number is 8. Protons have a mass of approximately one atomic mass unit or a.m.u., and they have a charge of +1.

The number of protons--the ______ number--is unique for each element, e.g. Carbon is 6. However, the number of neutrons can differ, resulting in substances known as isotopes.

Atomic. They differ from each other in atomic mass/weight, which is the number of protons plus neutrons in an atom. For example, carbon may have an atomic number of 6, but it has two isotopes C-12 and C-14. This means it can either have an atomic mass of 12 or 14, depending on whether it has 6 neutrons, or 8 neutrons. Below is a table showing the isotopes of Hydrogen:

A(n) _________ (self-feeder) is an organism that makes its own food--it converts energy from an inorganic source by photosynthesis or chemosynthesis.

Autotroph. Chemosynthesis is the capture of energy released by certain inorganic chemical reactions.

Most atoms found in biological systems tend to gain or lose their outer electrons to achieve a Noble Gas, outer electron shell configuration of two or eight electrons. The number of electrons that are gained or lost is characteristic for each element, and is the cause of atomic _______.

Bonding. The gain or loss determines the number and types of chemical bonds that atoms of that element can form. Thus, elements whose outer shells are not filled are chemically reactive. In other words, each type of atom has a certain number of electrons in its outer shell. This number determines how reactive it is, or how likely it is to bond with other atoms. If an atom has two or eight electrons in its outer shell, then it is stable--otherwise, it will probably bond with other atoms until it ends up with two or eight electrons in the outer shell.

The general formula Cx(H2O)x is commonly used to represent many _____________, which means "watered carbon." They are formed by green plants from carbon dioxide and water during the process of photosynthesis.

Carbohydrates. That formula indicates any number of Carbon atoms combined with any number of water molecules. Carbohydrates serve organisms as energy sources and as essential structural components. In addition, part of the structure of nucleic acids, which contain genetic information, consists of carbohydrates.

There are two main types of carbohydrates: sugars and ________.

Starches. These compounds contain only carbon, hydrogen, and oxygen, usually in the ratio 1:2:1.

A hydrocarbon is hydrophobic except when it has an attached ionized functional group such as ________ acid (COOH). If so, the molecule is hydrophilic.

Carboxyl. Why do we care if an organic molecule is attracted to water or not? Since cells in an organism are 70-90% water, the degree to which organic molecules interact with water affects their function.

Since carbon can make covalent bonds with another carbon atom, carbon chains and rings that serve as the backbones of organic molecules are possible. This property is known as __________.

Catenation. Carbon has four electrons in outer shell, and can bond with up to four other atoms (usually H (Hydrogen), O (Oxygen), N (Nitrogen), or another C). It often forms up into what are known as "carbon chains" and "carbon rings" which form the backbones of organic molecules. For example, in butane, we have 4 carbon atoms which form the backbone of the molecule:

______ is a polysaccharide that forms the fibrous part found in plant cell walls.

Cellulose. In terms of human diets, cellulose is indigestible, and thus forms an important, easily obtained part of dietary fiber. As compared to starch and glycogen, cellulose resists the actions of enzymes that break down storage polysaccharides (such as starch).

The element carbon is the basis of known life. Biological systems, while unique to each species, are based on its ________ bonding properties.

Chemical. Apart from carbon, 'organic' chemicals (associated with living things) usually contain all or some of hydrogen, nitrogen, oxygen, phosphorus and sulphur

The nucleus of the average human cell is only six micrometers (6 ´ 10-6 meter) in diameter, yet it contains about 1.8 meters of DNA. This is distributed among 46 ___________, each consisting of a single DNA molecule about 40 millimeters (1 1/2 inches) long.

Chromosomes. It's an extraordinary packaging problem. If you enlarge this by a million times, a DNA molecule would still be a thin string two millimeters thick, and the average chromosome would contain 40 kilometers (25 miles) of DNA. At this magnification, with a diameter of only six meters, the nucleus would contain 1,800 kilometers of DNA

The hydrogen bonds make water molecules sticky, a property known as ________.

Cohesion. The hydrogen bonds also make water molecules stick to other materials, particularly solids--a property known as adhesion.

The formation of the ester bond by ____________ (the removal of water from a molecule) allows the linking of monosaccharides into disaccharides and polysaccharides.

Condensation. A common plant polysaccharide is starch, which is made up of many glucoses.

During a condensation reaction of monomers, a hydroxyl (OH) group is removed from one monomer and a hydrogen (H) is removed from the other. This results in a ________ bond between them, thereby forming a polymer.

Covalent. A monomer is a molecule that can combine with others to form a polymer. In a condensation reaction, water is given off when one monomer gives off OH and another gives off an H. In the process, the two monomers join together to form a polymer

Vacuoles are single-membrane organelles located within the cell--a space within a cell that is empty of _________, lined with a membrane, and filled with fluid.

Cytoplasm. Many organisms will use vacuoles as storage areas. "Vesicles" are much smaller than vacuoles and function in transport within and to the outside of the cell.

The ____________ maintains the shape of the cell as well as anchoring organelles, moving the cell and controlling internal movement of structures.

Cytoskeleton. The cytoskeleton consists of fibrous proteins that occur in the cytoplasm. The cytoplasm was defined earlier as the material between the plasma membrane (cell membrane) and the nuclear envelope.

According to the most widely accepted theory, the universe began 10 to 20 billion years ago with the Big Bang , when a very small "egg" of high _______ and temperature exploded and formed the expanding universe.

Density. It is also estimated that about 1,000,000 years later the universe was sufficiently cool for atoms to form. There have been many modifications and arguments around this theory in recent times.

Of the two major types of nucleic acids, ________________ acid (better known as DNA) is the physical carrier of inheritance for 99% of living organisms. DNA functions in information storage. The English alphabet has 26 letters and over 50,000 words. DNA has 4 letters (C, G, A, and T) and 20 words (the 20 amino acids) that can make an infinite variety of sentences (polypeptides).

Deoxyribonucleic. DNA and RNA are the two major types of nucleic acids. The nucleotide of DNA consists of a deoxyribose sugar molecule to which is attached a phosphate group and one of four nitrogenous bases: two purines (adenine and guanine) and two pyrimidines (cytosine and thymine). The bases are represented as C (cytosine), G (guanine), A (adenine) and T (thymine).

By combining oxygen with _________, an isotope of hydrogen, one gets heavy water ( D2O).

Deuterium. Heavy Water is important in chemical research and is also used as a neutron moderator in some nuclear reactors

_ are attempts to reduce the amount of fats present in specialized cells known as adipose cells that accumulate in certain areas of the human body.

Diets. By restricting the intakes of carbohydrates and fats, the body is forced to draw on its own stores to makeup the energy debt.

Water tends to __________ into H+ and OH- ions, where the oxygen retains the electrons and only one hydrogen. Thus, becoming a negatively charged ion known as hydroxide (OH-).

Dissociate. Pure water has the same number of H+ and OH- ions. Acidic solutions (Acids) have more H+ ions than OH- ions. Basic solutions (Bases) have the opposite. As the H+ concentration increases, the OH- concentration decreases and vice versa.

In chemical reactions, when two reactants bond together we call it a combination, as in A+B -> C. In ____________, we represent the reaction by C -> A+B. (note: -> represents a right arrow)

Dissociation. These chemical reactions are read from left to right, so (A+B -> C) represents A+B combining to form C. On the other hand (C -> A+B) shows the opposite--C breaking up into A and B.

The nuclear envelope is a ______-membrane structure. Numerous pores occur in the envelope, allowing RNA and other chemicals to pass, but not allowing DNA to pass.

Double

In an atom, _________ occupy orbitals, or areas where they are most likely to be found.

Electrons

Chemical bonds store ______. The C-C covalent bond has 83.1 Kcal (kilocalories) per mole, while the C=C double covalent bond has 147 Kcal/mole.

Energy. Chemical bonds are potential energy, until they are converted into another form of energy, say, kinetic energy. It takes energy to break chemical bonds; that's why it takes heat energy to break the hydrogen bonds in liquid water until the water molecules break apart and float off as gas.

The orbitals (types s,p,d and _) are arranged in shells, or increasing energy levels from the nucleus outward.

F. The major energy levels into which electrons fit, are (from the nucleus outward) K, L, M, and N. Sometimes these are numbered, with electron configurations being: 1s22s22p1, etc. The nomenclature above tells us the 1st energy level (shell) has 2 electrons in the s orbital, and 2nd energy level has 2 electrons in its s orbital, plus one electron in its p orbital.

What you see below is the Modern Periodic Table of elements. Phosphorous in column VA, row 3 has ____ electrons in its outer shell, and has three shells in total.

Five. Each numbered row tells us how many electron shells an atom has, and each roman numeralled column ending in A, how many electrons in the outer shell.

Nucleic Acids are substances that comprise the _______ material of living cells. They direct the course of protein synthesis, thereby regulating all cell activities. Furthermore, by their transmission from one generation to the next, they are the vehicle for inherited characteristics.

Genetic. Nucleic acids are how characteristics are passed on from one generation to the next. The molecules of nucleic acids are long chains consisting of repeating structural units called nucleotides. Each nucleotide is made up of a central sugar group, to which are attached a phosphate group and a nitrogenous organic base.

The products of photosynthesis are assembled to make _______. Thus, energy from sunlight is converted into the C-C covalent bond energy.

Glucose. Photosynthesis is the process by which plants create carbohydrates using sunlight as an energy source. This energy is stored in the chemical bonds of sugar. One mole of glucose (6.022137 x 1023 molecules) yields 673 Kcal of energy. A calorie is the amount of heat needed to raise one gram of water one degree C. A Kcal has 1000 times as much energy as a cal.

A ___________ is a compound that is made up only of C (carbon) and H (hydrogen) atoms. The carbon atoms join together to form the framework of the compound; the hydrogen atoms attach to them in many different configurations. Benzene and methane are good examples.

Hydrocarbon . Acetylene and butane are also hydrocarbons. They are principal components in natural gas, petroleum, coal and bitumens.

Due to ________ bonding, water molecules associate strongly. In an ice crystal, the association is a highly ordered, but loose structure. When the ice melts, this orderly arrangement breaks down partially and the molecules pack more closely together. This makes the liquid denser than the solid, which is why ice forms on top of liquid wate

Hydrogen. If ice were denser than liquid water, it would sink and water reservoirs would freeze from the bottom up. As heat energy is added and the temperature of ice rises, the molecules in ice vibrate faster, eventually breaking some of their hydrogen bonds; these molecules then begin to move around as well as vibrate and ice begins to melt. Because hydrogen bonds must be broken, ice melts at a much higher temperature than similar substances that do not form hydrogen bonds.

In ice, we find another type of bond called ________ bonds. These result from the weak electrical attraction between the positive end of one H2O molecule and the negative end of another.

Hydrogen. These bonds are very weak--although taken in a large enough quantity, the result is strong enough to hold molecules together or in a three-dimensional shape.

Functional groups are clusters of atoms with characteristic structure and functions. For instance, polar molecules (with +/- charges) are attracted to water molecules and are termed "___________".

Hydrophilic. Nonpolar molecules are repelled by water and do not dissolve in water--they are hydrophobic.

One of the most common functional groups is the -OH (________) group. Its presence will enable a molecule to be water soluble.

Hydroxyl . If something is water soluble, that means it will dissolve in water. Take, for example, any basic alcohol - ethanol which has a formula of C2H5 -OH.

Isomers are molecules with _________ molecular formulas but a different arrangement of their atoms

Identical. This is different from the sense in which we understand 'isotopes'. Isotopes are variations of an element--they have the same atomic number, but differing atomic mass (same number of protons, different number of neutrons. Isomers are variations

In an _____ bond, two or more atoms bond together to form a molecule by transferring electrons to each other.

Ionic. The atoms exchange electrons in a way that all of the atoms end up with a full outer shell. For example, when Sodium combines with Chlorine, Sodium loses the one electron it has in its outer shell, and chlorine gains one electron, ending up with eight electrons in its outer shell. Both Sodium and Chlorine are now stable. You can tell how many electrons an atom has in its outer shell by looking at the periodic table. As you can see, Na (Sodium), has 1 electron in the outer shell, because it is in column IA. Likewise Cl (Chlorine) is in column VIIA.

__ are involved mainly with long-term energy storage. They are generally insoluble in polar substances such as water.

Lipids. Secondary functions of lipids are as structural components (building block in cell membranes) and as "messengers" (hormones) that play roles in communications within and between cells. They are composed of three fatty acids (usually) covalently bonded to a 3-carbon glycerol. The fatty acids are composed of CH2 units, and are hydrophobic/not water soluble.

Mixing like oil and water," is an old adage, but it has a fair bit of science behind it. Fatty (oily) substances are a part of organic macromolecules known as ______ , which have areas lacking polar covalent bonds. Water molecules dislike such molecules, causing fats to clump together.

Lipids. The structure of many molecules can greatly influence their solubility (ability to be dissolved). Sugars, such as glucose, have many hydroxyl (OH) groups, which tend to increase the solubility of the molecule.

Each organic molecule group has small molecules (monomers) that are linked repeatedly to form a larger organic molecule (_____________).

Macromolecule. They can be joined together to form polymers that are the large macromolecules made of three to millions of monomer subunits.

Because electrons move at speeds near to that of light, we need to think of them as matter (having ____ is a property of matter), and energy ( or quanta of energy), like photons. This is also known in physics as wave-particle duality.

Mass

After the formation of the earth, there are several theories for how life began, leaving aside the supernatural. The idea of panspermia hypothesized that life originated out in space and came to earth inside a _________.

Meteorite. In 1969, a meteorite (left-over bits from the origin of the solar system) landed near Allende, Mexico. The Allende Meteorite (and others of its sort) have been analyzed and found to contain amino acids, the building blocks of proteins--one of the four organic molecule groups basic to all life.

____________ are made up of globular proteins called tubulins. They play an important role in cell division (mitosis) and serve as a "temporary scaffolding" for other organelles.

Microtubules. They participate in the formation of spindle fibres during cell division (mitosis). They help give shape to many cells and are major components of cilia and flagella, the 'limbs' that enable cell movement.

_________ are compounds with elements in definite, fixed ratios, like water. Those atoms are held together usually by one of the three bonds - ionic, covalent or hydrogen. On the other hand, soil is a mixture with uncertain components

Molecules. Molecular formulas are the simplest expression of the composition of a substance. For example, the sugar glucose has 6 Carbons, 12 hydrogens, and 6 oxygens per repeating structural unit. The formula is written C6H12O6.

Disaccharides are formed when two _______________ are chemically bonded together.

Monosaccharides. A monosaccharide is a simple sugar which cannot be broken down into a simpler sugar. Disaccharides are sugars made up of two monosaccharides. Sucrose, a common plant disaccharide, is composed of the monosaccharides glucose and fructose. Lactose, milk sugar, is a disaccharide composed of glucose and the monosaccharide galactose

In covalent bonds, when electrons spend more time with one atom than the other, a type of covalent bond, known as a polar bond develops. Water (H2O) is an example. Since the electrons spend so much time with the oxygen (oxygen having a greater electronegativity, or electron affinity), that end of the molecule acquires a slightly ________ charge.

Negative. The water molecule is thus polar, having positive and negative sides.

The rightmost column of the periodic table contains inert elements known as the ___________, because they tend to occur in elemental form and are least likely to react.

Noble gases. These elements are called noble gases because they don't usually react with other elements--they are usually found in pure form. On the other hand, most other elements (i.e. oxygen, hydrogen) are found combined with other elements. It was later determined that the noble gases had outer electron shells containing two (as in the case of Helium) or eight (Neon, Xenon, Radon, Krypton, etc.) electrons. This gives them chemical stability. You will learn later why having two or eight electrons in the outer shell means chemical stability

The ancient Greek philosophers developed the concept of the atom, calling it the fundamental particle of matter that could not be broken down. Today we accept that elements are substances consisting of one type of atom. However, we also discovered that atoms can be broken down - in _______ reactions.

Nuclear

In 1950, Stanley Miller designed an experimental test for Oparin's hypothesis that cellular life was preceded by a period of chemical evolution. According to the theory, pre-cellular life would have begun with the formation of _____________.

Nucleic Acids. Miller's (and subsequent) experiments have not proven life originated in this way. It's only shown that conditions thought to have existed over 3 billion years ago were such that the spontaneous (inorganic) formation of organic macromolecules "could" have taken place. The simple inorganic molecules that Miller placed into his apparatus, produced a variety of complex organic molecules.

All kinds of atoms contain varying quantities of subatomic particles, arranged around a _______, as if in a solar system

Nucleus

The _______ occurs only in eukaryotic cells, and houses many different types of nucleic acids--the more famous ones being DNA and RNA.

Nucleus. A cell that contains a distinct nucleus is known as a eukaryotic cell, as opposed to a prokaryotic cell (no nucleus). RNA moves out into the cytoplasm ( what lies between the nucleus and the cell wall).

Another nucleic acid known as Ribonucleic Acid (RNA) is commonly present in the _______ and cytoplasm of cells. Most cytoplasmic RNA is associated with the ribosomes in a cell, where protein synthesis occurs.

Nucleus. Protein synthesis is the process whereby proteins are created. Viruses, which are noncellular, contain a single nucleic acid molecule--either RNA or DNA.

Around the _______, electrons are arranged in orbitals, and each orbital can hold only two electrons.

Nucleus. Orbitals come in different shapes and sizes. The s orbital is spherical, and located closest to the nucleus. The px, py, and pz orbitals are dumbbell shaped, along the x, y, and z axes respectively.

Ionic bonds generally form between elements in Group I (having ___ electron in their outer shell) and Group VII-A (having seven electrons in their outer shell).

One. Such bonds are relatively weak, and tend to disassociate in water; i.e. salt produces solutions that have both Na and Cl ions.

In the early days of science, inorganic substances could be extracted from the rocks, sediments, or waters of the Earth, whereas _______ substances were found only in the tissues or remains of living organisms.

Organic. The word 'inorganic' refers to nonliving things, whereas 'organic' refers to living things. Glucose is an organic substance while common salt is not.

A(n) heterotroph (other-feeder) is an ________ that obtains its energy from another organism.

Organism. Animals, fungi, bacteria, and many protistans are examples.

A _______ bond is a link between the amino group [-NH2] of one amino acid and the carboxyl group [-COOH] of the next amino acid in the protein chain. All living things (and even viruses) use various combinations of the same twenty amino acids.

Peptide. Due to this special bond, although amino acids may have other formulas, those in protein invariably have the general formula RCH(NH2)COOH, where C is carbon, H is hydrogen, N is nitrogen, O is oxygen, and R is a group, varying in composition and structure, called a side chain.

In its solid form -- ice -- water is less dense than when it is liquid, another unusual property! The root of these anomalies in the water molecule is its electronic structure, due to a _____ covalently bonded molecule.

Polar. Most substances are denser in their solid form than they are in their liquid form -- in other words, the molecules are more closely packed together. However, water expands when it changes into a solid -- the molecules get further apart. Another anomaly in water - its melting point, 0 °C (32 °F), and boiling point, 100 °C (212 °F), are much higher than would be expected by comparison with analogous compounds, such as hydrogen sulfide and ammonia

A __________ is any self-contained cell or organism that lacks internal unit membranes. Bacteria are among the best-known organisms of this kind.

Prokaryote. Prokaryotes are one-celled organisms, and are among the oldest forms of life on earth.

About two thirds of the body is made up of __

Water

The atomic mass is the number of _______ plus neutrons in an atom.

Protons. Oxygen has an atomic number of 8 because it has 8 protons, and most oxygen atoms have an atomic mass of 16, because there are 8 protons + 8 neutrons. You will see why we say most, but not all oxygen atoms have an atomic mass of 16 in the next question

A majority of isotopes show nuclear instability, e.g. the tendency of C-14 to convert into C-12. They disintegrate spontaneously with a release of energy, resulting in a process known as ___________ decay.

Radioactive. This phenomenon is now used to determine the age of fossils and artifacts (carbon dating) and in medical diagnosis (radiology).

When stars/galaxies are moving away from us, the energy they emit is shifted to the red side of the visible-light spectrum. Those moving towards us are shifted to the violet side. A phenomenon called _________ is a strong evidence in the favor of the Big Bang theory.

Red Shift. This shift is an example of the Doppler effect. Similar effects are observed when listening to a train whistle-- it will sound higher (shorter wavelengths) approaching and lower (longer wavelengths) as it moves away. Likewise red wavelengths are longer than violet ones. Most galaxies appear to be moving away from ours. Remember, ROY G. BIV helps you to remember the colors of a rainbow, which helps you to easily figure out which color to expect from a moving star/galaxy. The longest wavelength color in the rainbow is Red, and the shortest wavelength is Violet.

Biochemically, living systems are separated from other chemical systems by three things - the capacity of ___________ from one generation to another, the presence of enzymes and other necessary complex molecules for living, and a membrane that separates the internal cells from the outer environment.

Replication. Most organisms today use DNA as the hereditary material, although recent evidence (ribozymes) suggests that RNA may have been the first nucleic acid system to have formed.

The nucleolus is an area of the nucleus where _________ are constructed.

Ribosomes

A lack of Vitamin C results in ______.

Scurvy.

The cell membrane is found in all cells. It _________ the inner parts of the cell from the outer environment.

Separates. It also acts as a selectively permeable barrier to allow certain chemicals, namely water, to pass and others to not pass.

The pH scale is a logarithmic scale representing the concentration of H+ ions in a solution. It is represented as the negative logarithm of the H+ ion concentration. If the pH of water is _____, then the concentration of H+ ions is 10-7.

Seven. If we have a solution with a concentration of 10-7, that means one in every 10 million molecules is H+ (10-7 = 1 / 107 = 1 / 10,000,000).

Take the case of Chlorine, which belongs to a group of elements with _____ electrons in the outer shell, instead of the desired eight. Thus, it will tend to gain one electron in any reaction, gaining a charge of (-1), which makes it a charged atom known as an ion.

Seven. In common salt, Chlorine (Cl) forms an ionic bond with Sodium (Na), which has just one electron in its outer shell. Sodium gives that electron to Chlorine and acquires a positive charge. Oppositely charged ions are attracted to each other, forming the molecule sodium chloride. Sodium combining with chlorine to form salt is an example of an ionic bond. In an ionic bond, electrons are transferred, as opposed to covalent bonds, where the electrons are shared.

Covalent bonds are formed when atoms _____ electrons. Like child custody between two parents, the electrons tend to spend more time with one atom than the other. The number of electrons shared differs based on the atoms involved.

Share. Since electrons move very fast they can be shared, effectively filling or emptying the outer shells of the atoms involved in the bond. Such bonds are referred to as electron-sharing, or covalent bonds. Have a look at how single covalent bonds in the molecule methane make both carbon and hydrogen atoms stable. Carbon normally has 4 electrons in its outer shell, and Hydrogen has 1. When four Hydrogen atoms bond with a Carbon atom through a covalent bond, they share electrons so that the Hydrogen atoms effectively end up with stable 2-electron outer shells, and the carbon atom ends up with an 8-electron outer shell.

Sugars are structurally the ________ carbohydrates. They are the structural unit which makes up the other types of carbohydrates.

Simplest. Monosaccharides are single (mono=one) sugars. Important monosaccharides include ribose (C5H10O5), glucose (C6H12O6), and fructose (same formula but different structure than glucose).

Fats and oils function for energy storage. Animals convert excess sugars (beyond their glycogen storage capacities) into fats. Fats yield 9.3 Kcal/gm, while carbohydrates yield 3.79 Kcal/gm. Fats store ___ times as much energy as glycogen.

Six. Animals convert excess sugars into fats, but most plants store excess sugars as starch, although some seeds and fruits have energy stored as oils (e.g. corn oil, peanut oil, palm oil, canola oil, and sunflower oil).

The four "letters" in the DNA code are cytosine, guanine, adenine, and _______ (list them separated by commas).

Thymine. These four "letters," usually just represented by C, G, A, and T, combine in various combinations to form a code that determines a person's trait. For example, your hair color has a piece of DNA strand corresponding to it.

The ____________ of water represents the unique conditions at which it can exist in all three phases in equilibrium.

Triple point. The triple point of any substance is that temperature and pressure at which the material can coexist in all three phases (solid, liquid and gas) in equilibrium. Specifically the triple point of water is 273.16 Kelvin at 611.2 Pa. Note: Kelvin is a different measurement of temperature. 0 on the Kelvin scale is equal to -273 on the Celsius scale. So to convert kelvin to celsius, just subtract 273.

The presence of a double C=C covalent bond reduces the number of hydrogens that can bond to the carbon chain, hence termed ___________.

Unsaturated. Fatty acids can be saturated (meaning they have as many hydrogens bonded to their carbons as possible) or unsaturated. Oils, which are liquids at room temperature, have unsaturated fatty acids. Note that we talked about covalent bonds earlier as one of the three types of molecular bonds. Most covalent bonds are single bonds, but double bonds can also form--which means that instead of bonding to two separate carbon atoms, a carbon would bond twice with one carbon atom. This is indicated by C=C, instead of C-C.

Antigens are substances located on the outside of cells, _______, and in some cases other chemicals

Viruses. Antibodies are chemicals (Y-shaped) produced by an animal in response to a specific antigen. This is the basis of immunity and vaccination

Hydrocarbons are insoluble in _____ and are less dense than water, so they float on its surface. They are usually soluble in one another, however, as well as in certain organic solvents.

Water. However, if burned completely with sufficient oxygen, they produce carbon dioxide and water, releasing heat. All hydrocarbons are combustible. If the oxygen is insufficient, the combustion yields mainly carbon monoxide.

It is vital to life, and yet a strange molecule. _____ participates in virtually every process that occurs in plants and animals. Although the molecules are simple in structure (H2O), the physical and chemical properties of the compound are extraordinarily complicated.

Water. It is a colorless, tasteless, and odorless liquid at room temperature. One of its most important properties is its ability to dissolve many other substances - a universal solvent. It exists in all three states - solid, liquid and gas, on Earth, and only one state in our two neighboring planets.