Download Chapter 2 Chemistry of Life - Cardinal Newman High School

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Chapter 2
Chemistry of Life
Copyright © 2007, 2005, 2002, 1997, 1992 by Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.
1
Objectives
• Define the terms atom, element, molecule,
and compound.
• Describe the structure of an atom.
• Compare and contrast ionic and covalent
types of chemical bonding.
• Distinguish between organic and inorganic
chemical compounds.
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Objectives (cont’d.)
• Discuss the chemical characteristics of
water.
• Explain the concept of pH.
• Discuss the structure and function of the
following types of organic molecules:
carbohydrate, lipid, protein, and nucleic
acid.
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Chapter 2
Lesson 2.1
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Levels of Chemical Organization
• Atoms
– Nucleus—central core of atom
• Proton—positively charged particle in nucleus
• Neutron—non-charged particle in nucleus
• Atomic mass—number of protons in the nucleus;
determines the type of atom
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Levels of Chemical Organization
• Atoms
– Energy levels—regions surrounding atomic
nucleus that contain electrons
• Electron—negatively charged particle
• May contain up to 8 electrons in each level
• Energy increases with distance from nucleus
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Levels of Chemical Organization
• Elements, molecules, and compounds
– Element—a pure substance; made up of only
one kind of atom
– Molecule—a group of atoms bound together
in a group
– Compound—substances whose molecules
have more than one kind of atom
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Chemical Bonding
• Chemical bonds form to make atoms more
stable
– Outermost energy level of each atom is full
– Atoms may share electrons, or donate or
borrow them to become stable
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Chemical Bonding
• Ionic bonds
– Ions form when an atom gains or loses
electrons in its outer energy level to become
stable
• Positive ion—has lost electrons; indicated by
superscript positive sign(s), as in Na+ or Ca++
• Negative ion—has gained electrons; indicated by
superscript negative sign(s), as in Cl–
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Chemical Bonding
• Ionic bonds
– Ionic bonds form when positive and negative
ions attract each other because of electrical
attraction
– Electrolyte—molecule that dissociates (breaks
apart) in water to form individual ions; an ionic
compound
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Chemical Bonding
• Covalent bonds
– Covalent bonds form when atoms shared their
outer energy to fill up and thus become stable
– Covalent bonds do not ordinarily easily
dissociate in water
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Chapter 2
Lesson 2.2
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Inorganic Chemistry
• Organic molecules contain carbon-carbon
covalent bonds and/or carbon-hydrogen
covalent bonds; inorganic molecules do
not
• Examples of inorganic molecules: water
and some acids, bases, and salts
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Inorganic Chemistry
• Water
– Water is a solvent (liquid into which solutes
are dissolved), forming aqueous solutions in
the body
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Inorganic Chemistry
– Water is involved in chemical reactions
• Dehydration synthesis—chemical reaction in which
water is removed from small molecules so they
can be strung together to form a larger molecule
• Hydrolysis—chemical reaction in which water is
added to the subunits of a large molecule to break
it apart into smaller molecules
• Chemical reactions always involve energy
transfers, as when energy is used to build ATP
molecules
• Chemical equations show how reactants interact to
form products; arrows separate the reactants from
the products
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Inorganic Chemistry
• Acids, bases, and salts
– Water molecules dissociate to form equal
amounts of H+ (hydrogen ion) and OH–
(hydroxide ion)
– Acid—substance that shifts the H+/OH–
balance in favor of H+; opposite of base
– Base—substance that shifts the H+/OH–
balance against H+; also known as an
alkaline; opposite of acid
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Inorganic Chemistry
• Acids, bases, and salts
– Ph—mathematical expression of relative H+
concentration in an aqueous solution
• 7 is neutral (neither acid nor base)
• Ph values above 7 are basic; ph values below 7
are acidic
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Inorganic Chemistry
• Acids, bases, and salts
– Neutralization occurs when acids and bases
mix and form salts
– Buffers are chemical systems that absorb
excess acids or bases and thus maintain a
relatively stable ph
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Chapter 2
Lesson 2.3
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Organic Chemistry
• Carbohydrates—sugars and complex
carbohydrates)
– Contain carbon (C), hydrogen (H), oxygen (O)
– Made up of six-carbon subunits called
monosaccharides or single sugars (e.g.,
glucose)
– Disaccharide—double sugar made up of two
monosaccharide units (e.g., sucrose, lactose)
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Organic Chemistry
• Carbohydrates—sugars and complex
carbohydrates)
– Polysaccharide—complex carbohydrate made
up of many monosaccharide units (e.g.,
glycogen made up of many glucose units)
– Function of carbohydrates is to store energy
for later use
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Organic Chemistry
• Lipids—fats and oils
– Triglycerides
• Made up of one glycerol unit and three fatty acids
• Store energy for later use
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Organic Chemistry
• Lipids—fats and oils
– Phospholipids
• Similar to triglyceride structure, except with only
two fatty acids, and with a phosphorus-containing
group attached to glycerol
• The head attracts water and the double tail does
not, thus forming stable double layers (bilayers) in
water
• Form membranes of cells
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Organic Chemistry
• Lipids—fats and oils
– Cholesterol
• Molecules have a steroid structure made up of
multiple rings
• Cholesterol stabilizes the phospholipid tails in
cellular membranes and is also converted into
steroid hormones by the body
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Organic Chemistry
• Proteins
– Very large molecules made up of amino acids
held together in long, folded chains by peptide
bonds
– Structural proteins
• Form structures of the body
• Collagen is a fibrous protein that holds many
tissues together
• Keratin forms tough, waterproof fibers in the outer
layer of the skin
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Organic Chemistry
• Proteins
– Functional proteins
• Participate in chemical processes
• Examples: hormones, cell membrane channels and
receptors, enzymes
• Enzymes
– Catalysts—help chemical reactions occur
– Lock-and-key model—each enzyme fits a
particular molecule that it acts on as a key fits
into a lock
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Organic Chemistry
• Proteins
– Proteins can combine with other organic
molecules to form glycoproteins or
lipoproteins
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Organic Chemistry
• Nucleic acids
– Made up of nucleotide units
• Sugar (ribose or deoxyribose)
• Phosphate
• Nitrogen base (adenine, thymine or uracil,
guanine, cytosine)
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Organic Chemistry
• Nucleic acids
– DNA (deoxyribonucleic acid)
• Used as the cell’s “master code” for assembling
proteins.
• Uses deoxyribose as the sugar and A, T (not U),
C, and G as bases
• Forms a double helix shape
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Organic Chemistry
• Nucleic acids
– RNA (ribonucleic acid)
• Used as a temporary “working copy” of a gene
(portion of the DNA code)
• Uses ribose as the sugar and A, U (not T), C, and
G as bases
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Organic Chemistry
• Nucleic acids
– By directing the formation of structural and
functional proteins, nucleic acids ultimately
direct overall body structure and function
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