Download 2-1 Checkpoint - Jordan High School

Chapter 2
The Chemical Level
of Organization
2-1: Atoms
• All matter is composed of elements
– Atom—smallest unit of matter
Atomic Structure
• Atoms contain:
– Protons (p+)
– Neutrons (n0)
– Electrons (e-)
• Number
of protons = atomic number
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• Nucleus contains protons & neutrons
– Electron cloud contains electrons in
electron shells (levels)
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Isotopes
• Isotopes—neutron number differs
• Protons + neutrons = mass number
• Ex: carbon
– C12: 6 protons, 6 neutrons
– C13: 6 protons, 7 neutrons
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Electron Shells
• Atoms are neutral (protons = electrons)
• Electrons occupy shells around nucleus
– Unfilled shells make atom unstable
• Shells:
– 1st shell = 2 e– 2nd shell = 8 e2-5
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2-1 Checkpoint
1. Define atom.
2. How is it possible for two samples of
hydrogen to contain the same number
of atoms but have different weights?
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2-2: Chemical Bonds
• Atoms become stable by combining
through chemical bonds
• Molecules—contain more than 1 atom
– Ex: O2, H2
• Compound—2 or more elements bond
– Ex: H2O, CO2, C6H12O6
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Ionic Bonds
• Add an electron = -1 charge (anion)
Lose an electron = +1 charge (cation)
• Ionic bonds—created when an anion
& cation attract
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Covalent Bonds
• Covalent bond—electrons shared
between elements
• Single covalent bond—share 1 pair
electrons
• Double covalent bond—share 2 pairs
of electrons
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• Unequal sharing creates a polar
covalent bond
– One end slightly positive (δ+)
– Other end slightly negative (δ-)
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Hydrogen Bonds
• Hydrogen bond—weak attraction
between molecules
• Positive end of one molecule attracts to
negative end of another molecule
• Important for DNA, water
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2-2 Checkpoint
1. Define chemical bond, and identify
several types of chemical bonds.
2. Why does oxygen combine readily with
other elements, but neon does not?
3. Which kind of bond holds atoms in a
water molecule together? What
attracts water molecules to each
other?
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2-3: Chemical Reactions
• Chemical reactions
reactants  products
• Metabolism—all the chemical
reactions in the body
• Energy allows body to perform work
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Types of Reactions
• Decomposition reaction—molecules
broken down
AB  A + B
• Used in hydrolysis—breaks molecules
to form water
• Catabolism breaks down molecules in
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• Synthesis reaction—molecules made
A + B  AB
• Used in dehydration synthesis—
breaks down water to form molecules
• Anabolism forms new molecules in
cells
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• Exchange reaction—reacting
molecules are shuffled
AB + CD  AD + CB
Reversible Reactions
• Many reactions are reversible
A + B ↔ AB
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2-3 Checkpoint
1. What is the molecular formula for
glucose, with 6 carbon atoms, 12
hydrogen atoms, and 6 oxygen atoms?
2. Identify and describe three types of
chemical reactions important to human
physiology.
3. Glucose is converted into 2 threecarbon molecules. What type of
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reaction
is this?
2-4: Enzymes
• Enzymes speed reactions in the body
– Also called catalysts
• Exergonic reactions release energy
• Endergonic reactions require/absorb
energy
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2-4 Checkpoint
1. What is an enzyme?
2. Why are enzymes needed in our cells?
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2-5: Inorganic & Organic
Compounds
• Inorganic compounds—molecules
without both carbon & hydrogen
– H2O, CO2, O2, acids, bases & salts
• Organic compounds—contain both
carbon & hydrogen
– Carbs, lipids, proteins, nucleic acids
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2-5 Checkpoint
1. Distinguish between inorganic
compounds and organic compounds.
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2-6: Water
• Chemical reactions in body require
water
• Water has high heat capacity
– Takes a lot of energy change temperature
of water
• Water dissolves & disperses many types
of molecules
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• Most chemical reactions occur in
solutions
– Contain fluid solvent & dissolved solutes
• Ionic bonds broken apart by
dissociation
– Cations & anions mix with water
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2-6 Checkpoint
1. List the chemical properties of water
that make life possible.
2. Why does water resist changes in
temperature?
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2-7: Body Fluid pH
• pH—concentration of hydrogen atoms
– pH scale goes 0 – 14
• pH below 7 = acidic
pH 7 = neutral
pH above 7 = basic (alkaline)
• pH of blood = 7.35 – 7.45
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2-7 Checkpoint
1. Define pH, and explain how the pH
scale relates to acidity and alkalinity.
2. Why is an extreme change in pH of
body fluids undesirable?
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2-8: Acids, Bases & Salts
• Acid—substance that breaks apart &
releases hydrogen ions
HCl  H+ + Cl-
• Base—substance that removes
hydrogen ions; frees a hydroxide (OH-)
ion
NaOH  Na+ + OH2 - 32
Salts
• Salt—break down in water, release
cations & anions
– Electrolytes—conduct electric currents
Buffers & pH
• Buffers—stabilize pH
– Ex: antacids
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2-8 Checkpoint
1. Define the following terms: acid, base,
salt.
2. How does an antacid decrease
stomach discomfort?
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2-9: Carbohydrates
• Carbohydrate—organic molecule with
C, H, & O
– Sugars & starches
• Most important source of energy
Monosaccharides
• Simple sugars (glucose)
• Can be a straight-chain or a ring
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Disaccharides & Polysaccharides
• Disaccharide—2 monosaccharides
linked through dehydration synthesis
– Monosacc. 1 + Monosacc. 2  Disacc. +
H2O
• Disaccharide split through hydrolysis
– Disacc. + H2O  Monosacc. 1 + Monosacc.
2
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Dehydration Synthesis
Hydrolysis
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• Polysaccharide—chain of monosacc.
– Starches—from plants
– Cellulose—from cell walls of plants (fiber)
– Glycogen—animal starch; chain of glucose
molecules used as energy
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2-9 Checkpoint
1. A food contains organic molecules with
the elements C, H, and O. What class
of compounds do these molecules
represent, and what are their major
functions in the body?
2. When two monosaccharides undergo a
dehydration synthesis reaction, what
type of molecule is formed?
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2-10: Lipids
• Lipid—organic molecule with C, H, & O
– Fats, oils & waxes
• Source of energy, forms cell structures
Fatty Acids
• Fatty acid—chain of carbon atoms
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Fats
• Glycerol + fatty acids  fat
– Triglyceride = glycerol & 3 fatty acids
• Saturated fats
– Fatty acid chains have single bonds (animal
fats)
• Unsaturated fats
– Chains have double bonds (plant oils)
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Steroids
• Steroid—lipid molecule in rings
• Cholesterol
– Functions in cell membranes, hormones
• Most cholesterol comes from diet
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Phospholipids
• Phospholipid—contains glycerol head
& 2 fatty acid tails
– Important in cell membranes
• Head is hydrophilic, tails are
hydrophobic
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2-10 Checkpoint
1. Describe lipids.
2. Which kind of lipid would be found in a
sample of fatty tissue taken from
beneath the skin?
3. Which lipids would you find in human
cell membranes?
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2-11: Proteins
• Protein—most abundant compound
– Contain C, H, O, & N
Protein Function
• Many functions including:
– Structural support
– Movement & transport
– Enzymes
– Hormones
– Defense (skin & nails)
Protein Structure
• Proteins composed of amino acids
(a.a.)
– 20 different a.a. in human body
– a.a. determine protein function
• Peptide bonds link a.a. into chains to
form proteins
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• a.a. sequence determines function
– Incorrect a.a. can cause disfunction
• Protein shape also determines function
– Changes in temperature or pH causes
denaturation—change in shape
(irreparable)
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2-11 Checkpoint
1. Describe a protein.
2. How does boiling a protein affect its
structural and functional properties?
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2-12: DNA & RNA
• Nucleic acids—store & process genetic
information
– Contain C, H, O, N, & P
• DNA determines inherited
characteristics
• RNA make proteins from DNA code
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Structure of Nucleic Acids
• Nucleic acids composed of nucleotides
• Nucleotide structure
– Phosphate
– Sugar (deoxyribose or ribose)
– Nitrogenous base: adenine (A), guanine
(G), cytosine (C), thymine (T), uracil
(U)
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• DNA is a double helix of two strands
– Complementary base pairs bond
strands
– A – T, G – C
• RNA is a single strand
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Compare DNA & RNA
Sugar
Strand Type
Base Pairs
Function
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DNA
deoxyribose
double
A, T, G, C
genetic info
RNA
ribose
single
A, U, G, C
protein synthesis
2-12 Checkpoint
1. Describe a nucleic acid.
2. A large organic molecule composed of
ribose sugars, nitrogenous bases, and
phosphate groups is which kind of
nucleic acid?
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2-13: ATP
• Adenosine triphosphate (ATP)—
most important high-energy compound
• Adenosine diphosphate (ADP) combines
with a phosphate to form ATP
– Breakdown of ATP releases energy
• ADP + phosphate + energy ↔ ATP +
H2O
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2-13 Checkpoint
1. Describe ATP.
2. What are the products of the
breakdown of ATP?
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