Chapter 2: Chemical Level of Orgnanization Flashcards
identify the main chemical elements of the human body.
All forms of matter, both living and nonliving, are made up of a limited number of building blocks, chemical elements-Each element is a substance that cannot be split into a simpler substanceby ordinary chemical means-Twenty six different chemical elements are normally present in the body - Four elements called the major elements constitute about 96% of the body’s mass: oxygen, carbon, hydrogen and nitrogen
● Oxygen (O)
● Carbon (C)
● Hydrogen (H)
● Nitrogen (N)-
Eight elements called the lesser elements constitute 3.6% of the body’s mass: Calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium and iron ● Calcium (Ca) ● Phosphorus (P) ● Potassium (K) ● Sulfur (S) ● Sodium (Na) ● Chlorine (Cl) ● Magnesium (Mg) ● Iron (Fe)-
14 elements called trace elements constitute 0.4% of total body mass: ● Aluminum (Al) ● boron (B) ● chromium (Cr), ● cobalt (Co), ● copper (Cu), ● fluorine (F), ● iodine (I), ● manganese (Mn) ● molybdenum (Mo) ● selenium (Se) ● silicon (Si) ● tin (Sn) ● vanadium (V) ● zinc (Z)
describe the structures of atoms
Atoms: the smallest units of matter that retain the properties and characteristics of the element
Nucleus: the dense central core of an atom.
Electrons: negatively charged subatomic particle moving about in the large space surrounding the nucleus (number of electrons = number of protons)
Electron Shell: (1) 2, (2) 8, (3) 18
Protons: positively charged subatomic particle located in the nucleus
Neutrons: uncharged (neutral) subatomic particle located in the nucleus
Atomic number: the number of protons in the nucleus of an atom
Mass number: protons + neutrons
Isotopes: Although all atoms of one element have the same number of protons, they may have different numbers of neutrons and thus different mass numbers; Isotopes are atoms of an element that have different numbers of neutrons and therefore different mass numbers
.Atomic mass: the average mass of all an element’s naturally occurring isotopes
describe how valence electrons form chemical bonds.
Chemical Bond - The forces that hold together the atoms of a molecule or a compound
Valence shell of electrons: outermost shell of an atom; The likelihood that an atom will form a chemical bond with another atom depends on the number of electrons in it. An atom with a valence shell holding eight electrons is chemically stable, which means it is unlikely to form chemical bonds with other atoms.
distinguish among ionic, covalent, and hydrogen bonds.
1) Ionic bond (cation, anion, electrolyte): Held by opposite charges
Cation: a positively charged ion
Anion: a negatively charged ion
Electrolyte: An ionic compound that breaks apart into positive and negative ions in solution
2) Covalent bond; single, double, triple (nonpolar, polar, electronegativity): share electrons
Atoms form a covalently bonded molecule by sharing one, two, or three pairs of valence electrons. The larger the number of electron pairs shared between two atoms, the stronger the covalent bond. Covalent bonds may form between atoms of the same element or between atoms of different elements; the most common chemical bonds in the bod-
Single: when two atoms share one electron pair
Double: when two atoms share two pairs of electrons
Triple: when two atoms share three pairs of electrons-
Nonpolar: two atoms share the electrons equally—one atom does not attract the shared electrons more strongly than the other atom. The bonds between two identical atoms are always nonpolar covalent bonds-
Polar: the sharing of electrons between two atoms is unequal—the nucleus of one atom attracts the shared electrons more strongly than the nucleus of the
other atom. When polar covalent bonds form, the resulting molecule has a partial negative charge near the atom that attracts electrons more strongly. This atom has greater electronegativity, the power to attract electrons to itself. At least one other atom in the molecule then will have a partial positive charge
3) Hydrogen bond: forms when a hydrogen atom with a partial positive charge attracts the partial negative charge of neighboring electronegative atoms, most often larger oxygen or nitrogen atoms. Thus, hydrogen bonds result from attraction of oppositely charged parts of molecules rather than from sharing of electrons as in covalent bonds, or the lossor gain of electrons as in ionic bonds. weak compared to ionic and covalent bonds. Thus, they cannot bind atoms into molecules. However, hydrogen bonds do establish im-portant links between molecules or between different parts of a large molecule, such as a protein or nucleic acid● Surface tension: a measure of the difficulty of stretching or breaking the surface of a liquid. At the boundary between water and air, water’s surface tension is very high because the water molecules are much more attracted to one another than they are attracted to molecules in the air. The influence of water’s surface tension on the body can be seen in the way it increases the work required for breathing. A thin film of watery fluid coats the air sacs of the lungs. So, each inhalation must have enough force to overcome the opposing effect of surface tension as the air sacs stretch and enlarge when taking in air.
define a chemical reaction.
Chemical Reaction: occurs when new bonds form or old bonds break between atoms. Chemical reactions are the foundation of all life processes, and the interactions of valence electrons are the basis of all chemical reactions.● Reactants: the starting substances● Products: the ending substances ● Catalysts: chemical compounds that speed up chemical reactions by lower- ing the activation energy needed for a reaction to occur (Figure 2.9). The most important catalysts in the body are enzymes. A catalyst does not alter the difference in potential energy be- tween the reactants and the products. Rather, it lowers the amount of energy needed to start the reaction
describe the various forms of energy.
Potential (due to position) (difference b/w reactants and products (CATALYSTS DON’T CHANGE THIS)
and Kinetic (due to motion)
compare exergonic and endergonic chemical reactions.
EXERGONIC - release more energy than they absorb (R energy >P energy)
ENDERGONIC - absorb more energy than they release (R energy , P energy)
In body they happen together, and energy from one is used for the other ex. break down of glucose (EX)
explain the role of activation energy and catalysts in chemical reactions.
AE - Collision energy needed to break chemical bonds
speed rxn with higher concentration and higher temperature increase the chance this will happen.
catalysts - speed up reaction by lowering the AE, most important in body are enzymes
Enzyme: protein molecules that are catalysts in living cells. Some enzymes consist of two parts—a protein portion, called the apoenzyme and a non- protein portion, called a cofactor- The cofactor may be a metal ion (such as iron, magnesium, zinc, or calcium) or an organic molecule called a coenzyme. Coenzymes often are derived from vitamins.- The names of enzymes usually end in the suffix -ase. All enzymes can be grouped according to the types of chemical reactions they catalyze.1. Enzymes are highly specific. Each particular enzyme binds only to specific substrates(the reactant molecules on which the enzyme acts)
- Of the more than 1000 known enzymes in your body, each has a characteristic three-dimensional shape with a specific surface configuration, which allows it to recog- nize and bind to certain substrates.-active site: the part of the enzyme that catalyzes the reaction. thought to fit the substrate like a key fits in a lock. In other cases the active site changes its shape to fit snugly around the substrate once the substrate enters the active site. This change in shape is known as an induced fitenzyme-substrate complex: a temporary intermediate compound formed when substrates make contact with the active site on the surface of the enzyme molecule2. Enzymes are very efficient 3. Enzymes are subject to a variety of cellular controls Function:1. The substrates make contact with the active site on the surface of the enzyme molecule,forming a temporary intermediate compound called the enzyme–substrate complex. In this reaction the two substrate molecules are sucrose (a disaccha- ride) and water. 2. The substrate molecules are transformed by the rearrangement of existing atoms, the breakdown of the substrate molecule, or the combination of several substrate molecules into the products of the reaction. Here the products are two monosac- charides: glucose and fructose. 3. After the reaction is completed and the reaction products move away from the enzyme, the unchanged enzyme is free to attach to other substrate molecules
Describe the basic structure of ions,
Ions: an atom that has a positive or negative charge because it has unequal numbers of protons and electrons. . An ion of an atom is symbolized by writing its chemical symbol followed by the number of its positive (+) or negative (–) charges● Ionization: the process of giving up or gaining electrons
Describe the basic structure of molecules,
Molecule: When two or more atoms share electrons. . A molecule may consist of two atoms of the same kind, such as an oxygen molecule. Two or more different kinds of atoms may also form a molecule, as in a water molecule (H2O). In H2O one atom of oxygen shares elec- trons with two atoms of hydrogen.
Describe the basic structure of free radicals
Free radical: an atom or group of atoms with an unpaired electron in the outermost shell. A common example is superoxide, which is formed by the addition of an electron to an oxygen molecule. Having an unpaired electron makes a free radical unstable, highly reactive, and destructive to nearby molecules; become stable by either giving up their unpaired electron to, or
taking on an electron from, another molecule. In so doing, free radicals may break apart important body molecules
Describe the basic structure of compounds.
Compound: a substance that contains atoms of two or more different elements. Most of the atoms in the body are joined into compounds
describe synthesis, decomposition, exchange, and reversible reactions.
● Decomposition reactions (catabolism): split up large molecules into smaller atoms, ions, or molecules. Decomposition reaction: AB (molecule) → breaks down into → A (atom, ion or molecule A) + B (atom, ion or molecule). The decomposition reactions that occur in your body are collectively referred to ascatabolism. catabolic reactions are usually exergonic because they re- lease more energy than they absorb.● Exchange reaction: consist of both synthesis and decomposition reactions. Example: AB + CD → AD + BC. the bonds between A and B and between C and D break (decomposition) and new bonds form (synthesis) between A and D and B and C. ● Reversible reaction: the products can revert to the original reactants. A reversible reaction is indicated by two half-arrows pointing in opposite directions: AB → ← A + B . some reactions are reversible only under special conditions● Oxidation-reduction reactions: . Oxidation refers to the loss of electrons; in the process the oxidized substance releases energy. Reduction refers to the gain of electrons; in the process the reduced substance gains energy. Oxidation–reduction reactions are always parallel; when one substance is oxidized, another is reduced at the same time
describe the properties of water and those of inorganic acids, bases, and salts.
Most of the chemicals in your body exist in the form of com- pounds. Biologists and chemists divide these compounds into two principal classes: inorganic compounds and organic com- pounds- Inorganic compound: usually lack carbon and are structurally simple. Their molecules also have only a few atoms and cannot be used by cells to perform complicated bio- logical functions. They include water and many salts, acids, and bases.● Inorganic compounds may have either ionic or covalent bonds. Water makes up 55–60% of a lean adult’s total body mass; all other inorganic compounds combined add 1–2%.
Inorganic compounds that contain carbon include car- bon dioxide (CO2), bicarbonate ion (HCO ), and carbonic acid (H2CO3).
Organic compound: always contain carbon, usually contain hydrogen, and always have covalent bonds. Most are large molecules, many made up of long carbon atom chains. Organic compounds make up the remaining 38–43% of the human body.-
Water: the most important and abundant inorganic compound in all living systems. Although you might be able to survive for weeks without food, without water you would die in a matter of days. Nearly all the body’s chemical reactions occur in a watery medium. Water has many properties that make it such an indis- pensable compound for life.● Most important property of water is polarity - the uneven sharing of valence electrons that confers a partial negative charge near the one oxygen atom and two partial positive charges near the hydrogen atoms in a water molecule● This property makes water an excellent solvent for other ionic or polar substances, gives water molecules cohe- sion (the tendency to stick together), and allows water to resist temperature changes.
Acid: a substance that dissociates into one or more hydrogen ions and one or more anions. ● Hydrogen ion (H+): Because H+ is a single proton with one positive charge, an acid is also referred to as a proton donor-
Base: removes H+ from a solution and is therefore a proton acceptor. Many bases dissociate into one or more hydroxide ions (O ) and one or more cations. ● Hydroxide ion (OH-)-
Salt: when dissolved in water, dissociates into cations and anions, neither of which is H+or OH-. In the body, salts such as potassium chloride are electrolytes that are important for carrying electrical currents (ions flowing from one place to another), especially in nerve and muscular tissues
distinguish among solutions, colloids, and suspensions.
Mixture: a combination of elements or compounds that are physically blended together but not bound by chemical bonds.
Solution: one ore more solute dissolved into a solvent to produce a homogenous mixture
(Concentration: can be expressed in several ways● Mole: the amount of any sub- stance that has a mass in grams equal to the sum of the atomic masses of all its atoms. For example, 1 mole of the element chlo- rine (atomic mass = 35.45) is 35.45 grams)
Colloid: differs from a solution mainly because of the size of its particles. The solute particles in a colloid are large enough to scatter light. For this reason, colloids usually appear translucent or opaque.-
Suspension: the suspended material may mix with the liquid or sus- pending medium for some time, but eventually it will settle out. Blood is an example. When freshly drawn, an even, reddish color. After blood sits for a while in a test tube, red blood cells settle outof the suspension and drift to the bottom of the tube. The upper layer, the liquid portion of blood, appears pale yellow and is called blood plasma.
