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Bio 134
Ch. 6
6.1Atoms, Elements, and
Compounds
P. 148-155
Main Idea
Matter is composed of tiny particles called atoms
Atom
Building blocks of matter
Structure of an Atom
Nucleus – the center of the atom where protons and neutrons are located
Protons – positively charged particles Neutrons – particles that have no
charge Electrons – negatively charged
particles located around the nucleus
Inside an Atom
Element
A pure substance that cannot be broken down into other substances by physical or chemical means
Are made of 1 type of atom
Isotopes Atoms of the same element that
have different numbers of neutrons Add the number of protons and
neutrons
Compounds
Are a pure substance formed when two or more different elements combine
H2O
– 2 hydrogens, 1 oxygen
What are 2 characteristics of compounds?
1. Always formed in a fixed ratio– Example: Water – H2O – always has 2 H
for every 1 O
2. Can only be broken down into specific parts by a chemical reaction
Chemical Bond
The force that hold two substances together– Example: water (H2O), salt(NaCl),
methane (CH4)
Chemical Bond
They travel around the nucleus in areas called energy levels
A partially filled energy level is not stable. Atoms become more stable by losing e- or
attracting e- from other atoms
Covalent Bonds
a chemical bond that forms when e- are shared
Molecule
Substances with covalent bonds– Example: water (H2O)
Covalent bonds can be single (sharing only 1 pair of e-) double (sharing 2 pairs of e-) or triple (sharing 3 pairs of e-)
Ionic Bond
Ion – an atom that has lost or gained one or more electrons and has a positive or negative charge
Ionic Bonds – when + charged ions bond with – charged ions
NaCl Ionic Bond
Van der Waals Forces
When molecules come close together, the attractive forces between slightly positive and negative regions pull on the molecules and hold them together.
The strength of the attraction depends on the size of the molecule, its shape, and its ability to attract electrons
End of 6.1
6.2 Chemical Reactions
p. 156 - 160
Main Idea
Chemical reactions allow living things to grow, develop, reproduce, and adapt
Reactants and Products
Chemical reaction – the process by which atoms or groups of atoms in substances are reorganized into different substances
-Chemical bonds are broken down or formed
How do you know a chemical reaction has taken place? Color change Production of heat Production of light Formation of a gas, solid, or liquid
Example of a chemical reaction:
Chemical Equations
Reactants – the starting products are always on the left side of the arrow
Products – the substances formed during the reaction are always on the right side of the arrow
Reactants Products
Balanced Equations
Law of Conservation of Mass – states that matter can not be created nor destroyed
The number of atoms of each element on the reactant side must be equal to the number of atoms of the same element on the products side
Why do we balance chemical equations? Because matter can not be created nor
destroyed
Paper Burning Demo
Paper Burning Check…
How do we know a reaction took place?
What happened when we covered the paper with the glass cover?
What was needed in order for the paper to burn?
Energy of Reactions
Activation Energy – the minimum amount of energy needed for reactants to form products in a chemical reaction– Example – a candle will not burn until you
light the wick, the flame provides the activation energy for the reaction of the substances in the candle
Types of Reactions
Exothermic reactions – it releases energy in the form of heat
Types of Reactions Endothermic reactions – it absorbs
heat energy
Back to Paper burning…
What was the activation energy that started the reaction of the paper burning?
Was it an endothermic or exothermic reaction?
Enzymes
Catalyst – a substance that lowers the activation energy needed to start a chemical reaction
Enzymes – are biological catalysts that speed up the rate of chemical reactions in biological processes
Enzyme Activity
Substrates – the reactants that bind to the enzyme
Active site – the specific location where a substrate binds on an enzyme
Substrates and Active Sites
What are the factors that affect Enzyme Activity? pH Temperature Other substances
End of 6.2
6.3Water and Solutions
P. 162 - 165
Why is water so important in
Biology?
Main Idea
The properties of water make it well suited to help maintain homeostasis in an organism
Polar molecule
Molecles that have an unequal distribution of charges and have oppositely charged regions
Example of polarity – the reason water and oil don’t mix – water is polar and oil is not
Example of polarity – Water and Oil
Hydrogen bond
A weak interaction ivolving a hydrogen atom and a F, O, or N atom
Is a strong type of van der Waals interaction
Hydrogen Bonding
Mixture
Combination of two or more substances in which each substance retains its individual characteristics
Examples of mixtures:
Homogeneous mixture
A mixture that has a uniform composition throughout
Examples:
Solution
When all of the components are evenly distributed throughout– Example: saltwater
Solvent
The substance in which another substance is dissolved
Example: water
Solute
The that is dissolved in the solvent
Example: salt
Heterogenous mixture
The components remain distinct, you can tell what they are individually
Example: a salad – has lettuce, vegetables, dressing – each ingredient remains independent
Suspension
When a particles in a liquid are not dissolved, and remain moving
Colloid
a heterogeneous mixture in which the particles do not settle out– Example – milk – protein and fat don’t
settle out
Blood
Solution – blood is a solution because it has many dissolved particles in it
Suspension – blood is a suspension because it has many particles suspended in it such as cells
Acids and Bases
Acid – substances that release Hydrogen ions (H+) when dissolved in water
Base – substances that release hydroxide ions (OH-) when dissolved in water
pH
The measure of concentration of H+ in a solution
pH of pure water is 7 (neutral) pH of lower than 7 are acidic
– have more H+ pH of higher than 7 are basic
– -have more OH-
pH Scale
Buffers
Mixtures that can react with acids or bases to keep the pH within a particular range
In cells, buffers keep the range between 6.5 and 7.5
In blood, buffers keep the range at about 7.4
End of 6.3
6.4 The Building Blocks of Life
p. 166 - 171
How does Chemistry relate to
Biology?
Main Idea
Organisms are made of carbon-based molecules
Organic Chemistry
Carbon can form covalent bonds with 4 other atoms, including other carbons
Can form straight chains, branched chains, and rings
Macromolecules
large molecules that are formed by joining smaller organic molecules together
Polymers
Molecules made from repeating unit of identical or nearly identical compounds linked together by a series of covalent bonds
Poly means many
P. 167
Use table 6.1 and list examples and functions of the 4 biological macromolecues
Carbohydrates
Compounds composed of carbon, hydrogen, and oxygen in a ratio of 1O, 2H, 1C
(CH2O)n – n is the number of units in the chain
Carbohydrate functions
Energy source – monosaccharide, disaccharide, sucrose (table sugar), lactose (in milk)
Structural support – in plants, cellulose provides support in cell walls– In animals Chitin is a polysaccharide that is the
main component in the hard outer shell of shrimp, lobsters, and some insects and fungi
Lipids
Molecules made mostly of carbon and hydrogen that make up fats, oils, and waxes
Primary function is to store energy– In animals, stored in fat cells– In plants, used as waxy coating on some
leaves
p. 169
Use your textbook to describe the following:– Saturated fats
– Unsaturated fats
– Polyunsaturated fats
Types of fats
– Saturated fats - Lipids that have tail chains with only single bonds between the carbon atoms
– Unsaturated fats - Lipids that have at least one double bond between carbon atoms
– Polyunsaturated fats - Fats with more than one double bond in the tail
Other Lipids
Phospholipid - Responsible for the structure and function of the cell membrane, serves as a barier in biological membranes
Steroid – examples: cholesterol and hormones such as estrogen and testosterone
Proteins
A compound made of small carbon compounds called amino acids
Amino acids
Small compounds that are made of carbon, nitrogen, oxygen, hydrogen, and sometimes sulfer
Amino Acid Structure
Have a central carbon atom An amino group (H2N)
A H atom A variable group – this makes each one
different (20 different groups)
3-D structure
Proteins have up to 4 levels of structure:– Primary structure - # of amino acids in a
chain and the order they are in– Secondary structure – folds into a uinque
3-d shape (helix and pleat)– Tertiary structure – globular or long fibers– 4th level – combining with other proteins
Nucleic Acid
Complex macromolecules that store and transmit genetic information
Made of smaller nucleotides
Nucleotides
Composed of carbon, nitrogen, oxygen, phosphorus, and hydrogen atoms
6 major nucleotides
DNA and RNA
Nucleic acids found in living organisms
ATP
The storehouse of chemical energy that can be used by the cells
End of 6.4
End of Ch. 6