The Chemistry of Life CHAPTER 2. Atoms, Ions, and Molecules SECTION 1:
-
Upload
ada-barker -
Category
Documents
-
view
219 -
download
0
Transcript of The Chemistry of Life CHAPTER 2. Atoms, Ions, and Molecules SECTION 1:
The Chemistry of Life
Chapter 2
Atoms, Ions, and Molecules
Section 1:
Objectives1. What three subatomic particles make up
atoms?
2. How are all the isotopes of an element similar?
3. What are the two types of chemical bonds?
The Big Idea• Life Depends on chemistry
• Chemical reactions keep you alive
Atom• Basic unit of matter
Democrites
DALTON’S ATOMIC THEORYDalton performed experiments, unlike Democritus, to test his theory on atomic structure.Theory included the following ideas:All elements are composed of submicroscopic indivisible particles called atoms.Atoms of the same element are identical.Atoms of different elements can physically mix together or chemically combine with one another in whole-number ratios to form compounds.Chemical reactions occur when atoms are separated, joined, or rearranged.
• Protons -
• Neutrons -
• Electrons -
Positively charged (+)
Not charged (neutral)
Negatively charged (-)
Subatomic particlesBind together to form the nucleus
Electrons Protons
Neutrons
Nucleus
What are the 3 major parts of an atom?• Proton
• Neutron
• Electron
Describe Proton• Protons are positively charged particles found in the
atomic nucleus. Protons were discovered by Ernest Rutherford..
• Experiments done in the late 1960's and early 1970's showed that protons are made from other particles called quarks. Protons are made from two 'up' quarks and one 'down' quark.
Describe Neutron• Neutrons are uncharged particles found in the atomic
nucleus. Neutrons were discovered by James Chadwick in 1932.
• Experiments done in the late 1960's and early 1970's showed that neutrons are made from other particles called quarks. Neutrons are made from one 'up' quark and two 'down' quarks.
Describe Electron• Electrons are negatively charged particles that
surround the atom's nucleus. Electrons were discovered by J. J. Thomson in 1897.
• Electrons determine properties of the atom. Chemical reactions involve sharing or exchanging electrons.
Describe nucleus• The nucleus is the central part of an atom. It
is composed of protons and neutrons.
• The nucleus contains most of an atom's mass.
• It was discovered by Ernest Rutherford in 1911.
Describe Quark• Believed to be one of the basic building blocks of matter. Quarks
were first discovered in experiments done in the late 1960's and early 1970's.
• Three families of quarks are known to exist. Each family contains two quarks. The first family consists of Up and Down quarks, the quarks that join together to form protons and neutrons.
• The second family consists of Strange and Charm quarks and only exist at high energies.
• The third family consists of Top and Bottom quarks and only exist at very high energies.
Describe isotope• Atoms that have the same number of
protons but different numbers of neutrons
What is the Electron Cloud Model?
• Model of the atom pictures the electrons moving around the nucleus in a region called an electron cloud.
• The electron cloud is a cloud of varying density surrounding the nucleus. The varying density shows where an electron is more or less likely to be. Atoms with electrons in higher energy levels have additional electron clouds of different shapes that also show where those electrons are likely to be.
For more information, click here:
http://regentsprep.org/Regents/physics/phys05/catomodel/cloud.htm
Element• A pure substance that consists of
just one type of atom
6
CCarbon12.011
Atomic number
An elements atomic number = number of protons
Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14
6 electrons6 protons6 neutrons
6 electrons6 protons8 neutrons
6 electrons6 protons7 neutrons
6
CCarbon12.011 Mass number
The Sum of protons and neutrons in the nucleus of an atom is its mass number
• The weighted average of the masses of an elements isotope is called its atomic mass
Radioactive isotopes• Can be dangerous
• Can be used practically• Radioactive dating
• Treat cancer
• Kill bacteria
Compounds• A substance formed by the chemical
combination of two or more elements in definite proportions
• Ex) H2O, NaCl
Table Salt
Ionic Bonds• Formed when one or more electrons
are transferred from one atom to another
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
• If an atom loses an electron it becomes positive
• If an atom gains an electron it becomes negative
Ions• Positively and negatively charged
atoms
Covalent Bonds• Forms when electrons are shared
between atoms
Molecule• The structure that results when atoms
are joined together by a covalent bond
• Smallest unit of most compounds
Van der Waals Forces• A slight attraction that develops
between the oppositely charged regions of nearby molecules due to unequal sharing of electrons
Homework
1. Describe the structure of an atom.2. Why do all isotopes of an element have the
same chemical properties?3. What is a covalent bond?4. What is a compound? How are they related
to molecules?5. How do Van der Waals forces hold
molecules together?6. How are ionic bonds and Van der Waals
forces similar? How are they different?
Properties of Water
Section 2:
Objectives1. Why are water molecules polar?
2. What are acidic solutions?
3. What are basic solutions?
The Big Idea
• Much of our planet is covered in water• Water is necessary for life to exist• If life exists on other planets, there most
likely is water present• Water has many properties that make
life possible
Polarity(-)
(+)
The oxygen atom has a stronger attraction for electrons
Hydrogen Bonds• Because of waters partial charges, they
can attract each other and create hydrogen bonds
• Not as strong as covalent or ionic bonds
• Waters ability to create multiple hydrogen bonds gives it many special properties
Cohesion• Attraction between molecules of the
same substance
Adhesion• Attraction molecules of different
substances
Mixture• Material composed of two or more
elements or compounds that are physically mixed but not chemically combined
• Ex.) salt & pepper, earths atmosphere
Solutions• Mixture of two or more substances in
which the molecules are evenly distributed
• Ex. salt water
• Settles out over time
Solutions
Cl-
Water
Cl-
Na+
Water
Na+
Solute• Substance that is dissolved
• Ex. salt
Solvent• The substance that does the dissolving
• Ex. Water
Suspensions• Mixture of water and non-dissolved
materials
• Ex. sugar solution, blood
• Separate into pieces so small, they never settle out
The pH scale• Indicated the concentration of hydrogen
ions in a solution
Neutral
Acid
Base
Acids• Any compound that forms H+
(hydrogen) ions in solution
Base• A compound that produces OH-
(hydroxide) ions in solution
Buffers• Weak acids or bases that can react with
strong acids or bases to prevent sharp, sudden pH changes
Homework
1. Use the structure of a water molecule to explain why its polar
2. Compare acidic and basic solutions in terms of their H+ ion and OH- ion concentrations
3. What is the difference between a solution and a suspension?
4. What does pH measure?
5. The strong acid hydrogen fluoride (HF) can be dissolved in pure water. Will the pH of the solution be greater or less than 7?
Carbon-Based Molecules
Section 3:
Objective1. What are the functions of each group
of organic compounds?
LIFE’S BACKBONE• Most of the compounds that make up living things contain
carbon. In fact, carbon makes up the basic structure, or “backbone,” of these compounds. Each atom of carbon has four electrons in its outer energy level, which makes it possible for each carbon atom to form four bonds with other atoms.
• As a result, carbon atoms can form long chains. A huge number of different carbon compounds exist. Each compound has a different structure. For example, carbon chains can be straight or branching. Also, other kinds of atoms can be attached to the carbon chain.
Section 2-3
Interest Grabber
Methane Acetylene Butadiene Benzene Isooctane
MACROMOLECULES “GIANT MOLECULES”
• Formed by a process called polymerization
Monomers• Smaller units
Polymers• Linked up monomers
Carbohydrates• Compounds made up of carbon,
hydrogen, and oxygen atoms usually in a ratio of 1:2:1
• Main source of energy
• The monomers of starch are sugars
• Single sugar molecules are called monosaccharides
• The large macromolecules formed from monosaccharides are known as polysaccharides
Starch
Glucose
Lipids• Made mostly from carbon and hydrogen
atoms
• Used to store energy
Lipid Glycerol
Fatty Acids
Proteins• Macromolecules that contain nitrogen
as well as carbon, hydrogen, and oxygen
• Proteins are polymers of molecules called amino acids
Amino Acids
General structure Alanine Serine
Carboxyl group
• More than 20 different amino acids, can join to any other amino acid
• The instructions for arranging amino acids into many different proteins are stored in DNA
• Each protein has a specific role
• The shape of proteins can be very important
Proteins
Amino Acids
Nucleic Acids• Macromolecules containing hydrogen,
oxygen, nitrogen, carbon, and phosphorus
Double Helix
Nucleotides• Consists of 3 parts: 5-carbon sugar,
phosphate group and nitrogen base
Nitrogen Base
5-Carbon Sugar
Phosphate group
2 kinds of nucleic acids• RNA (ribonucleic acids) – contains
sugar ribose
• DNA (deoxyribonucleic acid) – contains sugar deoxyribose
Homework
1. Name four groups of organic compounds found in living thing
2. Describe at least one function of each group of organic compounds
3. Compare the structures and functions of lipids and starches
Chemical Reactions and Enzymes
Section 4 & 5:
Objectives1. What happens to chemical bonds during
chemical reactions?
2. How do energy changes affect whether a chemical reaction will occur?
3. Why are enzymes important to living things?
The Big Idea• Living things are made up of chemical
compounds
• Everything that happens to an organism is based on chemical reactions
Chemical Reactions• A process that changes or transforms
one set of chemicals into another
Reactants• Elements or compounds that enter into
a reaction
Products
• Elements or compounds produced by a chemical reaction
Example Reaction: Getting rid of carbon dioxide• In the blood
• In the lungs
CO2 + H20 H2CO3 (carbonic acid)
H2CO3 CO2 + H2O
Released as you breathe
Energy in reactions Energy-Absorbing Reaction Energy-Releasing Reaction
Products
Products
Activation energy
Activation energy
Reactants
Reactants
Activation Energy• The energy that is needed to get a
reaction started
Enzymes• Some chemical reactions are too slow
or have activation energies that are too high to make them practical for living tissue
• These chemical reactions are made possible by catalysts
Catalyst• Substance that speeds up the rate of
chemical reactions
• Work by lowering a reactions activation energy
Enzyme• Biological catalysts
• Speed up reactions in cells
• Very specific
• Named for the reaction is catylzes
• Enzyme names always end in -ase
Reaction pathwaywithout enzyme Activation energy
without enzyme
Activationenergywith enzyme
Reaction pathwaywith enzyme
Reactants
Products
Substrates• The reactants of enzyme catalyzed
reactions
• The active site of the enzyme and the substrate have complementary shapes
• Fit like a lock and key
Enzyme Action
Enzyme – substrate complex
Glucose
Substrates
ATP
Substratesbind toenzyme
Substratesare convertedinto products
Enzyme-substratecomplex
Enzyme(hexokinase)ADP
Products
Glucose-6-phosphate
Productsare released
Active site
Regulation of Enzyme Activity• Enzymes are affected by any variable that
affects chemical reactions1. pH
2. Temperature
3. Concentration
of enzyme
Homework
1. What happens to chemical bonds during chemical reactions
2. Describe the role of energy in chemical reactions3. What are enzymes, and how are they important to
living things?4. Describe how enzymes work, including the role of
the enzyme substrate complex5. A change in pH can change the protein. How might
a change in pH affect the function of an enzyme such as hexokinase (hint: think about the analogy of the lock and key)