Chapter 6 Biology Notes
Chapter 6 Voc. Word List: elements, trace elements, atom, proton, electron, neutron, valance electron, quarks, isotopes, ions,
radioactivity, compounds, Covalent Bond, molecule, Ionic Bond, mixture, solution, solute, solvent, concentration, solubility,
acid, base, pH, Polar, Nonpolar, Diffusion, Brownian Motion, Robert Brown, concentration gradient, dynamic equilibrium,
capillary action, Hydrogen bond, organic, inorganic, isomer, macromolecule, nutrients, nutrition, carbohydrates,
Monosaccharide, Disaccharide, Polysaccharide, Lipid, Unsaturated fats, Saturated fats, Proteins, peptide bonds, amino acid,
enzyme, catalyze, inhibitor, substrate, nucleic acids, nucleotides, purine, pyrimidine, DNA, and RNA
Chapter 6.1: The Chemistry of Life
 Elements: A substance that can not be broken down into simpler substances except by nuclear means.
o Elements are made of all the same atoms.
o 92 elements are natural occurring and the others are made in a lab (synthetic)
o Most two abundant in the universe is Hydrogen 93.5% and Helium 6.3 %
o Most two abundant on Earth are Oxygen 46.6 % and Silicon 27.7 %
o Most elements are identified by a one or two letter abbreviation called symbol (some have three letters).
 The first letter is capitalized and the second (or third) are lower cased.
 Some symbols are only one letter
o Only 25 are essential to living organisms.
 C, H, N, and O-together make up 96% of the mass in the human body
o Trace elements are present in living things in very small quantities.
 Ex. Cu and Fe
 Atoms: The building blocks of matter and the smallest particle of an element that exhibits characteristics of that element.
o Parts of an atom:
 Protons: Positive charged particles found in the nucleus of an atom
 Atomic number = # of Proton
 Neutrons: no charge and are also found in the nucleus of an atom
 Atomic mass (Mass #) –Atomic Number = # of Neutron
 Electrons: Negative charged particles found outside the nucleus of an atom
 Number of Protons = Number of electrons
 Have energy levels 1-8 (electron cloud or shells)
 Valence electrons: the number of electrons found in the outermost shell
 Quarks: Are the subatomic particles that make up protons, electrons, and neutrons.
 Isotopes: When atoms of the same element have a different mass numbers. They are different amounts of neutrons but the
same amount of protons.
o Ions: charged particles +(cation), or – (anion)
 Radioactivity: is the spontaneous process through which unstable nuclei emit radiation. During radiation decay both
protons and neutrons can be released changing the identity of the element.
 Compounds: is a substance that is composed of atoms of two or more different elements that are chemically combined.
Each of the elements in the compound lose their chemical characteristics when chemically bond.
o Example: water
 Mixture: Combination of two or more components that retain their identities. Can be broken down by physical means.
Two Types
1. Heterogeneous mixture: Not evenly distributed and often different parts of the mixture have different
properties. Ex. Soil
2. Homogeneous mixture: The substances are uniformly distributed, so all parts have the same properties. Ex.
Steel, air, brewed coffee, and Kool-Aid
o Solution: 2 parts solute (what is being dissolved) and solvent (What is doing the dissolving) and are
always a homogeneous mixture
 Most are liquid like salt water and magma, but some are solids like bronze (from Tin and Copper)
and brass (from Copper and Zinc) and gases like air (mainly Nitrogen and Oxygen)
 Concentration of a solution is the ratio of the amount of solute to the amount of solvent
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
Solubility-Is the maximum amount of solute that can be dissolved in a solvent.
Chemical Bonding:
1.
Covalent bonds - 2 atoms sharing an electron in the outer most shell.
 The attraction of the positively charged nuclei for the shared, negatively charged electrons holds the atoms
together.
 Examples: sugars, fats, water, and proteins
 Molecule - A pure substance that consists of atoms held together by covalent bond. So water is a molecule
 No overall charge
 Ex. Water H2O  2 H + 1 O
 Most common form
 Polar covalent bond: Covalent bonds that the atoms do not share the electrons equally. While Nonpolar bonds do.
2.
Ionic bonds - The attractive force between a (+) metal ion and a (-) nonmetal ion.
 When atoms combine with each other by gaining or losing electrons in outermost energy level
o .Ex. Na+ + Cl- yields NaCl (table salt)
 Have an electrical charge.
Chemical Reactions: These occur when bonds are formed or broken.
o Reactants are the elements or compounds in the beginning of a written chemical equation before the
reaction takes place: Na + Cl →NaCl (→means yield sign)
o Products are the elements or compounds formed after the chemical reaction takes place:
Na + Cl → NaCl
o All of the chemical reactions that occur within living organisms are known as metabolism.
 Metabolic reactions break down and build molecules that are important for the functioning of
organisms.
Acid/Bases/pH
 Acid: Compound that produces H+ when dissolved in water
o Ex. HCl is added to water and H+ and Cl- forms and the solution of HCl is called Hydrochloric Acid (pH 2)
found in the stomach to break down food.
 Base: Compound that produces an (OH-) Hydroxide ion when dissolved in water
o NaOH is called Sodium Hydroxide
 Dissolves in water and forms Na+ and OH- ions. (pH 10)
 pH: pH scale 0-14 with less than 7 is an acid and greater than a 7 is a base and 7 is neutral
Chapter 6.2: Water and Diffusion
Water is important for several reasons:
1. Polar - molecule with an unequal distribution of charge.
 Each one has a (+) and (-) end.
2. Resist temperature change
3. Expands when freezes
4. Excellent solvent
5. Density: D=mass/volume
 The density of water is 1 g/cm3: the density of ice is 0.9 g/cm3
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6.
7.
8.
High surface tension
o Diffusion is the net movement of particles from an area of higher concentration to an area of lower
concentration.
 Diffusion results because of the random movement of particles called Brownian motion
 In 1827, Scottish scientist Robert Brown used a microscope to observe pollen grains
suspended in water- he found evidence that atoms and molecules have random movementcharacteristic of liquids, gases, and some solids
o Three key factors that affect rate of diffusion
a.) Concentration
 Concentration gradient is the difference in concentration of a substance across space going
inside and outside of a cellular layer.
 Dynamic Equilibrium is the same concentration of the substance inside and outside a cellular
layer.
b.) pressure
c.) temperature
Creeps up thin tubes by capillary reaction
High heat of vaporization (due to H bond) -helps us cool down
o Hydrogen bonds - The positively charged H+ atoms of one water molecule attracts the negatively charged Oof the other the other water molecule.
 Weak bond
 Important because it helps hold large molecules together
 Ex. Keeps proteins together
Chapter 6.3 - Organic Chemistry (Life Substances)
Anything that is living contains Carbon atoms.
 Carbon has 4 electrons available for bonding in its outermost shell.
 Carbon bonds:
 Single
 Double
 Triple
Organic molecules: will have the same simple chemical formula but often differs in structure. When this happens it is called
an isomer.
Large molecules are called macromolecules.
 carbohydrates, proteins, lipids, and nucleic acids
A polymer: a large molecule formed when smaller molecules are formed, when many smaller molecules bond together usually
in a long chain.
 Ex. Cholesterol
Macromolecules:
The first three are types of macromolecules are nutrients.
 Nutrients are chemicals our cells need to survive.
 Nutrition is the study of nutrients.
1.
Carbohydrates (sugars and starches)
 Used by cells to store and release energy
 Contain C, H, and O with a ratio of about 2 H and 1 O for each Carbon atom.
 Function: First used energy supply for body (%2)
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2.
3.
4.
3 kinds:
 Monosaccharide - simple sugar ex. Glucose and Fructose
 Disaccharide - 2 sugar molecule
 Ex. Sucrose - table sugar (glucose + fructose)
 Polysaccharide - polymers composed of many simple sugars. Ex. Starch
Lipids (Fats)
 Has a glycerol (3-C molecule) + 3 fatty acids.
 Contain C-H bonds and less O than carbohydrates.
 Function: Second used energy supply for body (stored)
 18-30% of body
 Nonpolar
 2 kinds:
 Unsaturated fats - have fatty acid chains with C=C, and are liquid at room temperature.
 Examples are vegetable oils, peanuts, corn, and olive oil
 Saturated fats - chains are C-C, and are solid at room temperature.
 Ex. Fats from steak
Proteins
 Large complex polymer with C, H, O, N, are sometimes S.
 Amino acids - basic building block of proteins, 20 kinds.
 Covalent bonds formed between amino acids are called peptide bonds.
 Function: Build and repair body parts
 18-20 % of body
 Make up tissues such as: Bone, Muscle, Skin
 Important for: muscle contraction, immunity (antibodies), and chemical reactions (enzymes).
 Enzymes –type of protein that usually speed up a chemical reaction, but occasionally will slow it down.
 Catalyst-speeds up a chemical reaction
 Inhibitor-slows or even stops a chemical reaction
 Each enzyme acts on a specific molecule or set of molecules called substrates.
 Each substrate fits into the active site found in the enzyme-See p. 162 of textbook.
Nucleic acids (DNA and RNA)
 Complex macromolecule that stores information in cells in the form of a code.
 The have C, H, O, N, and P atoms
 Nucleotides are the building blocks (monomers) of nucleic acids.
 Each nucleotide contains a 5-C sugar (ribose), a N-containing base (either purine or pyrimidine) and a Pgroup.
 Purine bases: adenine and guanine
 Pyrimidine bases: cytosine, thymine, uracil
 DNA (deoxyribonucleic acid) - master copy of genetic information code.
 A-T and G-C
 RNA (ribonucleic acid) - forms a copy of DNA
 A-U and G-C
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