1/21/2011 1 1. Your Roadmap for Success in Chapter 6 Preview the chapter: 1. Read Summary (p. 171). 2. Skim the Assessment questions (p. 171‐173). 3. Rewrite Learning Objectives for the chapter and each section in the form of possible test questions. (So, four sets of questions.) 4. Look at pictures. 2. Your Roadmap for Success in Chapter 6 • You are expected to read all parts of each section (1, 2, 3) on your own. You are responsible for knowing this material. • We will be covering most of the book content during class with slides, discussions, demos, and other activities. However, we can’t possibly cover all chapter content during class. 3. Your Roadmap for Success in Chapter 6 Assignments will include (at minimum): 1. Reading the chapter 2. Questions from each Section Assessment 3. Questions from the Chapter Assessment 4. Chapter notes (more later) 5. Class activities or labs
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1/21/2011
1
1. Your Roadmap for Success in Chapter 6
Preview the chapter:
1. Read Summary (p. 171).
2. Skim the Assessment questions (p. 171‐173).
3. Rewrite Learning Objectives for the chapter and each section in the form of possible test questions. (So, four sets of questions.)
4. Look at pictures.
2. Your Roadmap for Success in Chapter 6
• You are expected to read all parts of each section (1, 2, 3) on your own. You are responsible for knowing this material.
• We will be covering most of the book content during class with slides, discussions, demos, and other activities. However, we can’t possibly cover all chapter content during class.
3. Your Roadmap for Success in Chapter 6
Assignments will include (at minimum):
1. Reading the chapter
2. Questions from each Section Assessment
3. Questions from the Chapter Assessment
4. Chapter notes (more later)
5. Class activities or labs
1/21/2011
2
4. Your Roadmap for Success in Chapter 6
Assessments will include (at minimum):
1. The assignments mentioned
2. Quiz for each section
3. Test at the end of the chapter
4. Behavior/positive participation
There will be at least one extra credit opportunity offered per chapter.
Biology
Chapter 6: The Chemistry of Life1. Atoms and Their Interactions2. Water and Diffusion3. Life Substances
• A Compound is a substance that is composed of atoms of two or more different elements that are chemically combined .
• These elements are in exact proportions.
• Example: Water is always made up of ___ hydrogen atom(s) and ___ oxygen atom(s), bonded together in exactly the same way, to form a water molecule.
Compounds and Bonding
• Most matter is in the form of compounds.
• Why and how do atoms combine?
– Atoms combine with other atoms:
• Only when conditions are right
• To become more stable
• When is an atom usually most stable?
• How does an atom become more stable?
Covalent Bonds vs. Ionic Bonds
• Covalent bonds form when two atoms share electrons in their outermost shell (energy level).– Atoms are held together by the attraction between the positively‐charged nuclei and the shared, negatively‐charged electrons.
– Most compounds in organisms have covalent bonds (ex. sugars, fats, proteins, water).
• Molecule: Group of atoms held together by covalent bonds and having no overall charge.
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Compounds and Molecules• Molecular Compounds form when different atoms share their outermost electrons.
Hydrogen atoms have 1 electron.How many electrons does an oxygen atom have? (see pg. 147)
– On Earth, oxygen and hydrogen normally exist as gases.
– But as a compound (water), they can be liquid, solid, or gas.
**When a compound is formed, changes occur and a new substance forms.
Covalent Bonds vs. Ionic Bonds
• Most atoms have an equal # of electrons and protons; therefore, they have an electrical charge of ________.
• Ionic bonds form when atoms gain or lose an electron from their outer energy level.
• An ion is an atom (or group of atoms) that _____ or _____ electrons and has an _______ __________.
• An ion is a charged particle.
Covalent Bonds vs. Ionic Bonds
• Ions are held together by a different kind of chemical bond than covalent bonds.
• An ionic bond is the attractive force between two ions of opposite charge.
Ionic Bonds, cont’d• Ionic compounds are less abundant in living things than are covalent molecules.
• However, ions are very important in biological processes.
• Examples:– Sodium and potassium ions are required for transmission of nerve impulses.
– Calcium ions are necessary for muscles to contract.
– Plant roots absorb essential minerals in the form of ions.
Chemical ReactionsWhat is going on during a chemical reaction?
• Bonds between atoms are formed or broken, causing substances to combine and recombine as different molecules.– Chemical reactions occur over and over again inside cells.
• Metabolism: All of the chemical reactions that occur within an organism. – These chemical reactions are essential for the organism’s function.
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Chemical Reactions and Chemical Equations
• Chemical reactions are represented by chemical equations.
• Symbols and formulas are used to represent each element or substance.
2H2 + O2 2H2O
(Reactants) (Products)
Chemical Reactions and Chemical Equations
Reactants: Substances that undergo chemical reactions
6.2 Water and DiffusionWhy is water (perhaps) the most important compound in living organisms?
• Most life processes can occur only when molecules and ions are free to move and collide with one another.– This condition is met in water.
• Material transportation (blood, plant sap)
• Water makes up 70‐95% of most organisms.
Three (3) important characteristics of water…
1. Water is polar. What does this mean?
• In a covalent bond, electrons are not always shared equally. – For example: In water molecules, electrons are more strongly attracted to the O atom than to the H atoms).
Polar molecule: unequal distribution of charge resulting in a positive end (+) and a negative end (‐)
Why can water dissolve so many things? Polar water molecules attract:
• Ions (so ionic compounds like NaCl dissolve easily)
• Other polar molecules (like sugar)
• Water molecules
Hydrogen bond: A weak bond formed by the attraction of opposite charges between hydrogen and oxygen
• Hydrogen bonds hold many large molecules (e.g., organic compounds like proteins) together.
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Because of water’s polarity:
• Creeps up thin tubes (capillary action)
• Surface tension
2. Water resists temperature changes.• Good insulator
• Cells are in an aqueous environment, so they are protected from sudden changes in temperature.
3. Water expands when it freezes.
• Rare characteristic among substances.
• Ice is less dense than liquid water – floats.
– Allows life to continue underwater in winter.
– Helps make soil.
Diffusion
• Water is one way to move substances in living systems.
• Diffusion is another way.– Kinetic energy of objects in motion – applies to matter
– Ping‐Pong balls
– Random motion of molecules = Brownian motion
– Characteristic of gas, liquid, and some solid molecules
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• Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.
• Result of random movement of atoms.
• Three KEY factors:
1. Concentration (primary controlling factor)
2. Temperature
3. Pressure
Results of diffusion
• Two substances (e.g., colored corn syrup and pure corn syrup) will eventually be evenly distributed (concentration same everywhere).
– Atoms continue to move randomly and collide, but no changes in overall concentration.
– This condition is called dynamic equilibrium.
Concentration gradient: difference in concentration of a substance across space.
• Ions and molecules diffuse from area of high concentration to low concentration “move with the gradient”
• If no interference, diffusion continues until there is NO concentration gradient (dynamic equilibrium).
• One IMORTANT way cells move stuff in and out of cell!
• Disaccharide– Two monosaccharide molecules linked together.
– A two‐sugar carbohydrate• Example: glucose and fructose joined sucrose
1. Carbohydrates (p. 163)
• Polysaccharide– Largest carbohydrate molecules– Polymers composed of many monosaccharide units– Examples of glucose polymers: 1. Starch‐ food storage in plants; highly branched
chains; e.g., seeds, bulbs2. Glycogen – food storage in mammals; more highly
branched; e.g., liver3. Cellulose – cell walls and structural support in
plants; long chains hooked together like chain‐link fence.
• What function do they have?1. Regulate cell processes2. Carry out chemical reactions3. Build cell structures4. Control immune system5. Turn genes on or off