biology - chp 2 - the chemistry of life - powerpoint
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Chapter 2
The Chemistry of Life
Section 1: The Nature of Matter
Objectives
• What three subatomic particles make up atoms?
• How are all the isotopes of an element similar?
• 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
Subatomic particles• Protons - • Neutrons - • Electrons -
Positively charged (+)
Not charged (neutral)
Negatively charged (-)
Bind together to form the nucleus
Electrons Protons
Neutrons
Nucleus
Element• A pure substance that consists
of just one type of atom
6
CCarbon12.011
Atomic number
An elements atomic number = number of protons
Isotope• Atoms of the same element
that differ in the number of neutrons they contain
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.
Atoms are made up of protons and neutrons in a nucleus. Electrons are in constant motion in the space around the nucleus.
2. Why do all isotopes of an element have the same chemical properties
They have the same number of electrons
3. What is a covalent bond?
A bond formed when electrons are shared between atoms
4. What is a compound? How are they related to molecules
A compound is a substance formed by the chemical combination of two or more elements in definite proportions. A molecule is the smallest unit of most compounds
5. How do Van der Waals forces hold molecules together?
When the sharing of electrons are unequal, a molecule has regions that are charged. An attraction can occur between oppositely charged regions of nearby molecules
6. How are ionic bonds and Van der Waals forces similar? How are they different?
In both cases, particles are held together by attractions between opposite charges. The difference is that ionic charges are stronger
Section 2: Properties of Water
Objectives• Why are water molecules polar?
• What are acidic solutions? 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
Oxygen atom has greater attraction for electrons, therefore the oxygen atom is negative and the hydrogen end is positive
2. Compare acidic and basic solutions in terms of their H+ ion and OH- ion concentrations
Acid have more H+ ions than OH-
ions, and bases have more OH-
ions than H+ ions
3. What is the difference between a solution and a suspension?
In a solution, all components are evenly distributed. In a suspension, un-dissolved particles are suspended
4. What does pH measure?
The concentration of H+ ions in a solution
5. The strong acid hydrogen floride (HF) can be dissolved in pure water. Will the pH of the solution be greater or less than 7?
less than 7
Section 3: Carbon Compounds
Objective• What are the functions of each
group of organic compounds?
• 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
Life’s backbone
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 thingscarbohydrate, lipid, protein, nucleic acids
2. Describe at least one function of each group of organic compoundscarbohydrates – energylipids – store energyproteins – form tissuenucleic acids – transmit hereditary information
3. Compare the structures and functions of lipids and starches
Lipids are made from carbon and hydrogen. Starches are made of carbon, hydrogen and oxygen. They both can be used to store energy
Section 4: Chemical Reactions and Enzymes
Objectives• What happens to chemical bonds
during chemical reactions?
• How do energy changes affect whether a chemical reaction will occur?
• 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 reactions
1. pH
2. Temperature
3. Concentration
of enzyme
Homework
1. What happens to chemical bonds during chemical reactionsBonds are broken in reactants and new bonds are formed in products
2. Describe the role of energy in chemical reactionssome chemical reactions release energy, and other chemical reactions absorb energy. Energy changes determine how easily a chemical reaction will occur
3. What are enzymes, and how are they important to living things?
Enzymes are biological catylasts. Cells use enzymes to speed up virtually every important chemical reaction that takes place in cells
4. Describe how enzymes work, including the role of the enzyme substrate complex
Substrates, the reactants of an enzyme-catylzed reaction, attach to the enzyme at an active site and form an enzyme – substrate complex. Once the complex is formed, the enzyme helps convert substrate into product
5. 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)
A change in pH could change the shape of hexokinase. This change would diminish the ability of glucose and ATP to bind to the active site of the enzyme.