The Nature of Life

Outline Attributes of Living Organisms Chemical and Physical Bases of Life Molecules Bonds and Ions Acids and Bases Energy Carbohydrates, Lipids, Proteins Enzymes Nucleic Acids

Attributes of Living Organisms Composition and Structure  Cells - Structural units of organisms. - Cytoplasm - Interior cell matrix.  Nucleus - Houses genetic material (DNA) suspended in cytoplasm. - Cell Wall - Bounds cytoplasm.

Attributes of Living Organisms Growth  Increase in mass accompanied by an increase in volume. - Most growth results from production in new cells and includes variation in form. Reproduction  Producing offspring. - Always resemble parents.

Attributes of Living Organisms Response to Stimuli  Plants respond to stimuli such as light, temperature, and gravity. - Callose and callus are two substances that may accumulate at wound sites in plant cells.

Attributes of Living Organisms Metabolism  Collective product of all biochemical reactions in an organism. - Respiration - Energy release. - Photosynthesis - Energy harnessing. - Digestion - Large insoluble food molecules converted to smaller soluble molecules. - Assimilation - Conversion of raw materials into cell substances.

Attributes of Living Organisms Movement  Occurs at all levels of organization. - Cytoplasmic streaming. Organization Complexity  Molecules are organized into compartments, membranes, and other structures within cells and tissues. Environmental Adaptation  Natural selection adapts organisms to their environment.

Chemical and Physical Bases of Life Matter  Occupies space  Has mass  Composed of elements Atoms - Smallest stable subdivision of an element.  Nucleus - Center of an atom. - Protons - Positively charged particles. - Neutrons - Neutral particles.

Oxygen Atom Model

Chemical and Physical Bases of Life Atomic Number - Number of protons.  Cannot change within an element. Atomic Mass - Combined number of protons and neutrons.  Electrons - Negative electrical charges circling the nucleus. - Orbitals - Volume of space in which a given electron occurs 90% of the time.

Chemical and Physical Bases of Life An electron’s distance from the nucleus depends on its energy level.  Electron Shell - Outermost shell determines the atom’s reactivity.  Moving to an orbital farther away consumes energy.  Moving to an orbital closer in releases energy.

Orbital Models

Chemical and Physical Bases of Life Isotope - Form of an element that varies in its atomic weight (Varying number of neutrons).  Radioactive isotopes are unstable and spontaneously split into smaller parts.

Molecules Molecule - Two or more atoms bound together.  Compound - Two or more elements united in a definite ratio by chemical bonds. Molecules are in constant motion, with a temperature increase or decrease speeding up or slowing down the atoms.

Molecules Random collisions between molecules capable of sharing electrons are the basis for all chemical reactions.  Usually controlled by specific enzymes. - When a water molecule is formed, two hydrogen atoms become attached to an oxygen atom.

Molecules Polarity affects atom alignment.  Water molecules form a cohesive network as the slightly positive hydrogen atoms are attracted to the slightly negative oxygen atoms. - Cohesion - Attraction of similar molecules.  Capillary movement in plants. - Adhesion - Attraction of dissimilar molecules.

Water Molecules

Chemical and Physical Bases of Life Valence  Combining capacity of an atom or an ion. Bonds and Ions  Bonds are forces that move molecules by attracting and holding atoms. - Number of electrons in an atom’s outermost orbital determines how many chemical bonds can be formed by that particular atom.

Bonds and Ions Covalent Bond  Forms when two atoms complete their outermost energy level by sharing a pair of electrons.  Polar - Electrons are shared unequally.  Nonpolar - Electrons are shared equally.

Bonds and Ions Ionic Bond  Forms when electrons in outermost orbital are completely removed from one atom and transferred to another atom. - Ions - Formed when molecules lose or gain electrons.

Bonds and Ions Hydrogen Bond  Forms as a result of attraction between positively charged hydrogen atoms in polar molecules and negatively charged atoms in other polar molecules. - Only have 7-10% strength of covalent bonds.

Acids and Bases Acids are chemicals that release hydrogen atoms (H + ) when dissolved in water. Bases (alkaline compounds) are compounds that release negatively charged hydroxyl ions (OH - ) when dissolved in water.  pH scale represents measurement of H + ion concentration. - 7 = Neutral - <7 = Acidic - >7 =Alkaline

Energy Energy - The capacity to perform work. Thermodynamics - Study of energy and its conversions from one form to another.  First Law - Energy is constant. It cannot be increased or diminished, only converted from one form to another.  Second Law - Energy flow is uni-directional and there will always be less energy remaining after the conversion than existed before.

Energy Electrons with the least potential energy are located within the single spherical orbital closest to the atom’s nucleus.  Electrons with the most potential energy are in the outermost orbital.

Monomers and Polymers Polymers - Formed when two or more small units (monomers) bond together.  Dehydration Synthesis - Removal of water in the formation of a bond.  Hydrolysis - Occurs when hydrogen becomes attached to one monomer and a hydroxyl group to the other.

Carbohydrates Carbohydrates are the most abundant organic compounds in nature.  Monosaccharides - Simple sugars with backbones of three to seven carbon atoms. (Glucose and Fructose)  Disaccharides - Formed when two monosaccharides bond together by dehydration synthesis. (Sucrose)  Polysaccharides - Formed when several to many monosaccharides bond together. (Cellulose)

Lipids Lipids are fatty or oily substances that are mostly insoluble in water. (Fats and Oils)  Typically store twice as much energy as carbohydrates. - Most consist of chain with carbon atoms.  Saturated - No double bonds.  Unsaturated - At least one double bond between carbon atoms.

Lipids Waxes - Lipids consisting of long-chain fatty acids bonded to long chain alcohol other than glycerol. Phospholipids - Constructed like fats, but one of the fatty acids is usually replaced by a phosphate group.

Proteins, Polypeptides, and Amino Acids Proteins regulate chemical reactions in cells, and are usually very large and consist of one or more polypeptide chains.  Polypeptides are chains of amino acids. - Each amino acid has two functional groups plus an R group.  Amino group (-NH 2 )  Carboxyl group (-COOH)

Proteins, Polypeptides, and Amino Acids Polypeptide Structure  Primary Structure - A sequence of amino acids fastened together by peptide bonds.  Secondary Structure - Coiling of polypeptide chains.  Tertiary Structure - Maintained by coils between R groups.  Quaternary Structure - Occurs when a protein has more than one kind of polypeptide.

Storage Proteins Some plant food-storage organs store small amounts of proteins in addition to large amounts of carbohydrates.  Seeds usually contain proportionately larger amounts of proteins in addition to their complement of carbohydrates.

Enzymes Enzymes are mostly large, complex proteins that function as organic catalysts under specific conditions.  Work by lowering energy of activation. - Temporarily bonds with potentially reactive molecules at a surface site.

Nucleic Acids Nucleic acids are very large, complex polymers.  Vital to internal communication and cell functioning.  Deoxyribonucleic Acid (DNA) composed of nucleotides. - Nitrogenous base, five-carbon sugar, and a phosphate.

Review Attributes of Living Organisms Chemical and Physical Bases of Life Molecules Bonds and Ions Acids and Bases Energy Carbohydrates, Lipids, Proteins Enzymes Nucleic Acids

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