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Structure of Atoms
Atoms are made up of protons (+), neutrons (0), and electrons (-).
Protons and neutrons are in the nucleus of the atom.
Electrons are in constant motion outside the nucleus (electron cloud).
ELEMENTS are pure substances consisting of one type of atom.
ISOTOPES Isotopes are atoms of the same element
that have a different number of neutrons. This results in the isotopes having the same
atomic number, but different atomic masses.
Carbon-12, Carbon-13, and Carbon-14 are isotopes.
Radioactive isotopes can be used to determine the age of materials, treat cancer, and to trace the movement of substances in organisms.
Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14
6 electrons6 protons6 neutrons
6 electrons6 protons8 neutrons
6 electrons6 protons7 neutrons
Section 2-1
Figure 2-2 Isotopes of Carbon
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Chemical Compounds A chemical compound is a substance
formed by the chemical combination of two or more elements in definite proportions.
The chemical formula for a compound tells the types of elements that are in it, and the ratio in which the atoms of those elements combine.
Ex) H2O means two hydrogen atoms always combine with one oxygen atom to form a water molecule.
CHEMICAL BONDS Ionic bonds form when two or more
electrons are transferred from one atom to another. Ex) NaCl
Covalent bonds form when electrons are shared between atoms. Ex) water
Van der Waals forces are slight attractions that occur between oppositely charged regions of nearby molecules. Not as strong as ionic or covalent bonds.
Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-)
Transferof electron
Protons +11Electrons -11Charge 0
Protons +17Electrons -17Charge 0
Protons +11Electrons -10Charge +1
Protons +17Electrons -18Charge -1
Section 2-1
Figure 2-3 Ionic Bonding
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Water, Water Everywhere If you have ever seen
a photograph of Earth from space, you know that much of the planet is covered by water.
Water makes life on Earth possible. If life as we know it exists on some other planet, water must be present to support that life.
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Properties of Water
Water molecules are neutral, but polar. There is a slightly negative charge on oxygen, and slightly positive charge on the hydrogen atoms.
Water molecules are polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms.
Water is extremely cohesive because of its ability to form hydrogen bonds.
Cohesion vs. Adhesion Cohesion is the
attraction between molecules of the same substance. Ex) water molecules to each other
Adhesion is the attraction between molecules of different substances. Ex) water molecules cling to the inside of a plant stem
Mixtures
Mixtures are materials composed of two or more elements or compounds that are physically mixed together but not chemically combined.
Two types of mixtures made with water are homogenous mixtures and suspensions.
Homogenous mixtures Solution: Mixture of two or
more substances in which the molecules of the substance are evenly distributed.
Solvent- substance in which a solute is dissolved to form a solution. Ex) water
Solute- substance dissolved in a solvent to make a solution Ex) salt
Suspensions
Mixtures of water and undissolved materials that are so small they do not settle out.
Examples are blood and milk.
Acids, Bases, and pH
pH measures the concentration of hydrogen ions (H+) in solution. Ranges from 0 to 14.
ACIDIC solutions have high H+ concentrations, and a pH less than 7.
BASIC solutions have a low concentration of H+, and a pH greater than 7.
Solutions with pH of 7, such as pure water, are NEUTRAL.
BUFFERS are weak acids and bases that can react with strong acids or bases to prevent sudden changes in pH.
Oven cleaner
Bleach
Ammonia solution
Soap
Sea water
Human bloodPure waterMilkNormalrainfall
Acid rainTomatojuice
Lemon juice
Stomach acid
NeutralIn
crea
sing
ly B
asic
Incr
easi
ngly
Aci
dic
Section 2-2
pH Scale
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Carbon Compounds
Carbon forms strong covalent bonds. Carbon atoms can bond to other
carbon atoms to form long chains. Carbon-carbon bonds can be single,
double, or triple bonds. Carbon atoms can close upon
themselves to from rings.
Methane Acetylene Butadiene Benzene Isooctane
Section 2-3
Figure 2-11 Carbon Compounds
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Macromolecules Macromolecules are made from thousands
of smaller molecules. Monomers-small unit that can join with
other small units to form polymers. Polymers-large compound formed from
combinations of many monomers. Four groups of organic compounds found in
living things are carbohydrates, lipids, nucleic acids, and proteins.
Carbohydrates Carbohydrates are compounds made up of
carbon, hydrogen, and oxygen atoms, usually in a ratio of 1 : 2 : 1.
Living things use carbohydrates as their main source of energy. Stored as glycogen in animals and starch in plants.
Plants and some animals use carbohyrates for structural purposes. Plants have cellulose, animals have chitin.
Carbohydrates for structure
Cellulose in plant cells
(we don’t have enzymes to digest it)
Chitin in animal cells—arthropod shells and insects. Also found incells walls of fungi
Monosaccharides are single sugar molecules, such as glucose.
Polysaccharides are large macromolecules formed from monosaccharides, such as starch.
Lipids Lipids are a group of organic
molecules made mostly of carbon and hydrogen atoms.
Generally not soluble in water. Grouped as fats, oils, and waxes. Used to store energy, form parts of
biological membranes, and form waterproof coverings.
Examples: steroids, triglycerides
Saturated fats have the maximum number of possible hydrogen bonds. Tend to be solid at room temperature. Examples: meat fat, Crisco, butter, lard, etc.
Unsaturated fats have at least one carbon-carbon double bond C=C.
Polyunsaturated fats contain C=C double bonds, and are liquid at room temperature, Examples: olive oil, vegetable oils
Nucleic acids Nucleic acids are macromolecules
containing hydrogen, oxygen, nitrogen, carbon, and phosphorus
Nucleotides have three parts: 5-carbon sugar, phosphate group, and a nitrogenous base.
Nucleic acids store and transmit hereditary or genetic information
Examples: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)
The Double Helix
Hydrogen bonds
Nucleotide
Sugar-phosphate backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Nucleotide is a sugar, phosphate, & nitrogen base
Proteins Proteins are macromolecules that
contain nitrogen, carbon, hydrogen, and oxygen.
Proteins are polymers of amino acids. Have an amino group (--NH2) and a carboxyl group (--COOH) at the other.
The amino acids form chains that fold into complex structures.
General structure Alanine Serine
Section 2-3
Figure 2-16 Amino Acids
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Amino group Carboxyl group
Proteins control the rate of reactions and regulate cell processes.
Proteins help form muscle and bone tissue.
Proteins help transport substances into and out of cells.
Help fight diseases.
CarbonCompounds
include
that consist of
which contain
that consist of that consist of that consist of
which contain which contain which contain
Section 2-3
Concept Map
Carbohydrates Lipids Nucleic acids Proteins
Sugars and starches
Fats and oils Nucleotides Amino Acids
Carbon,hydrogen,
oxygen
Carbon,hydrogen,
oxygen
Carbon,hydrogen,oxygen, nitrogen,
phosphorus
Carbon,hydrogen,oxygen,
nitrogen,
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Chemical reactions and enzymes
A chemical reaction is a process that changes one set of chemicals into another set of chemicals.
Chemical reactions always involve the breaking of bonds in the reactants (starting materials) and the formation of new bonds in the products (results of the reaction)
When this occurs, energy is either released or absorbed.
Evidence that a chemical reaction has occurred includes heat, light, or gas being given off. Products are different from the reactants.
Energy in Reactions Since chemical reactions involve changes in
chemical bonds, they also involve changes in energy.
Exothermic- reactions that release energy. Often occur spontaneously.
Endothermic- reactions that must absorb energy to take place.
The energy needed to get a reaction started is called the activation energy.
Energy-Absorbing Reaction Energy-Releasing Reaction
Products
Products
Activation energy
Activation energy
Reactants
Reactants
Section 2-4
Figure 2-19 Chemical Reactions
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Enzymes Enzymes are catalysts that speed up
chemical reactions that take place in cells. Enzymes lower the activation energy of the
reaction. Enzymes provide a site where substrates
(reactants) are brought together so that the reaction can occur.
This is often described as a “lock and key” mechanism. Products are released. The enzyme is not used up in the reaction.
Reaction pathwaywithout enzyme Activation energy
without enzyme
Activationenergywith enzymeReaction pathway
with enzyme
Reactants
Products
Section 2-4
Effect of Enzymes
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Glucose
Substrates
ATP
Substratesbind toenzyme
Substratesare convertedinto products
Enzyme-substratecomplex
Enzyme(hexokinase)
ADPProducts
Glucose-6-phosphate
Productsare released
Section 2-4
Figure 2-21 Enzyme Action
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Active site
Enzymes, cont.
Optimal temperature and pH are needed for most enzymes to be effective.
Enzymes in the human body function best near normal body temperature: 35-400 C.
Below the optimum temperature, the reaction is slower or may not occur at all.
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