Download Understanding Our Environment

The Nature of Life
Outline
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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 16-18 carbon
atoms.
 Saturated - No double bonds.
 Unsaturated - At least one double bond
between carbon atoms.
Lipids
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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
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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 (-NH2)
 Carboxyl group (-COOH)
Proteins, Polypeptides, and Amino Acids
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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
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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
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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
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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
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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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