The Chemistry of Life

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The Chemistry of Life

• Chapter 2

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2-1 The Nature of Matter

• Biology is the study of living things and living
  things follow the rules of chemistry
• Biochemistry is the chemistry of living organisms

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• Elements any substance that cannot be broken
  down chemically into simpler substances

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• An element is a pure substance that is made
  entirely of one kind of atom.
• Elements are represented by a one- or two- letter
  symbol
• Ex C carbon, Na sodium

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• There are six elements essential to every
  organism and these elements account for 97 of
  the compounds present in the organism
• Carbon (C)
• Hydrogen (H)
• Oxygen (O)
• Nitrogen (N)
• Phosphorous (P)
• Sulfur (S)

CHONPS!!!
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• The subatomic particles that make up atoms are
• protons
• neutrons 0
• electrons -

• overall, atoms are neutral

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• Atoms of same element that differ in their number
  of neutrons are known as isotopes.
• ex Carbon has three isotopescarbon-12,
  carbon-13, and carbon-14

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• Some isotopes are radioactive, meaning that their
  nuclei are unstable and break down at a constant
  rate over time
• Although the radiation can be dangerous, they
  have important scientific and practical uses
• determine the ages of rocks and fossils
• treat cancer
• kill bacteria that cause food to spoil
• labels or tracers to follow the movement of
  substances within organisms

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Chemical Compounds

• In nature, most elements are found combined with
  other elements in compounds.
• A chemical compound is a substance formed by the
  chemical combination of two or more elements in
  definite proportions .
• The physical and chemical properties of a
  compound are different from the elements from
  which it is formed.

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• The atoms in compounds are held together by
  chemical bonds formed when electrons are shared
  or transferred between atoms.
• 2 main types of bonds are ionic bonds and
  covalent bonds

ex sodium chloride (NaCl table salt)
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• When one or more electrons are transferred from
  one atom to another, an ionic bond is formed.
• An atom that loses an electron has a positive
  charge.
• An atom that gains an electron has a negative
  charge.
• These positively and negatively charged atoms are
  known as ions

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Chemical Bonds
Sodium ion (Cl-)
Sodium atom (Na)
Sodium ion (Na)
Sodium atom (Cl)
Protons 11 Electrons - 11 Charge
0
Protons 11 Electrons - 10 Charge
1
Protons 17 Electrons - 18 Charge
-1
Protons 17 Electrons - 17 Charge
0
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• A covalent bond forms when electrons are shared
  between atoms.
• Sharing two electrons is called a single bond
• Sharing four electrons is called a double bond
• Sharing six electrons is called a triple bond
• The electrons that are shared travel in the
  orbitals of both atoms

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• polar covalent bond when electrons of a bond
  are not shared equally (example H2O)
• One side of molecule has a slight charge, the
  other has a slight charge
• polar molecules can easily dissolve in water,
  while nonpolar molecules cant
• nonpolar covalent bond when electrons are
  shared equally (example H2 or CO2 gas)
• Other examples include oils fats

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• A hydrogen bond is a weak attraction between a
  slightly positive hydrogen atom in a molecule and
  a nearby slightly negative atom of another
  molecule
• ex hydrogen bonds in water

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2-2 Properties of Water

• Cohesion is an attraction between molecules of
  the same substance.
• water is extremely cohesive because of hydrogen
  bonding
• Cohesion creates surface tension allowing some
  insects to walk on water

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• Adhesion is the attraction between molecules of
  different substances
• ex Ex water in a graduated cylinder / meniscus

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• Solutions and Suspensions
• A mixture is a material composed of two or more
  elements or compounds that are physically mixed
  but not chemically combined.
• In a solution all components are evenly
  distributed. The dissolved substance is the
  solute and the substance it is dissolved in is
  the solvent.
• Ex salt-water

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• Mixtures in which a substance does not completely
  dissolve, but the movement of water keeps the
  small molecules suspended is known as a
  suspension - Ex blood

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• Ionization is the process by which a nonionic
  compound is converted to ions
• A water molecule can form hydrogen (H) and
  hydroxide (OH-) ions
• The pH scale uses a range of numbers, 0 14, to
  indicate the level of H and OH- ions in a
  solution

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• Acids have a pH less than 7 and more H in
  solution.
• Bases have a pH greater than 7 and more OH- in
  solution.

H gt OH- OH- gt H
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• So how does the pH scale relate to living
  things?
• Even very small changes in levels of H and OH-
  ions inside a cell can trigger important chemical
  reactions
• blood pH must be near 7.4 (6.8 or 8.0 death)
• Controlling pH is important for maintaining
  homeostasis.
• One way the body controls pH is with buffers,
  which are weak acids or bases that can react with
  strong acids or bases to prevent sharp, sudden
  changes in pH.

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2-3 Carbon Compounds

• Organic chemistry is the study of all compounds
  that contain bonds between carbon atoms.
• Macromolecules are large, complex molecules made
  of a carbon skeleton other atoms and molecules
  that form by a process known as polymerization.

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• The smaller units, or monomers, join together to
  form polymers.

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• There are 4 major classes of macromolecules
• 1) Carbohydrates
• 2) Lipids
• 3) Proteins
• 4) Nucleic Acids
• 1) Carbohydrates carbon backbone hydrogen
  oxygen in a 21 ratio (CH2O)
• found in all known types of living cells
• provide quick energy
• digestion breaks carbohydrates down into simple
  sugars or monosaccharides

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• Single sugar molecules are called
  monosaccharides. Monosaccharides include glucose
  and fructose (found in many fruits).
• Two monosaccharides joined together are called
  disaccharides.
• Many monosaccharides joined together are called
  polysaccharides
• ex starch and
• cellulose in plants

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• 2) Lipids are made from carbon, hydrogen and
  oxygen atoms, but not in a fixed ratio
• 2 primary functions
• Long-term storage of energy
• Building of structural parts of cell membranes
• Building blocks (monomers)
• fatty acids glycerol
• Ex fats, oils and
• waxes in saturated
• and unsaturated forms

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• 3) Proteins compounds made of C, H, O N atoms
  (a few have S)
• building blocks are amino acids
• joined together by peptide bonds
• dipeptide 2 amino acids joined together
• polypeptide a long chain of amino acids
• The type, number and sequence of amino acids is
  what makes each protein different, even though
  they are all made from the same 20 basic amino
  acids.

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• Protein functions include
• structural components of cells
• messengers/receptors between cells
• defense against disease
• make up skin, hair, muscles, parts of the
  skeleton
• act as enzymes

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• The instructions for arranging amino acids into
  many different proteins are stored in DNA.

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• 4) Nucleic Acids compounds made of C, H, O, N,
  P, S atoms
• code for the amino acid sequence to make protein
  and contain the genetic information of all
  organisms
• 2 kinds deoxyribonucleic acid (DNA) and
  ribonucleic acid (RNA)
• Function store and transmit genetic information

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• The basic units of nucleic acids, nucleotides,
  are made from a 5-carbon sugar, a phosphate
  group, and a nitrogenous base.

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• DNA 3 parts
• Phosphate group
• Sugar is deoxyribose
• Nitrogen bases are
• Adenine
• Thymine
• Guanine
• Cytosine
• double-stranded
• Genetic code for organisms or blueprint of life

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• RNA 3 parts
• Phosphate group
• Sugar is ribose
• Nitrogen bases are
• Adenine
• Uracil
• Guanine
• Cytosine
• Single-stranded
• Involved in making proteins

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• In 1953 Watson Crick proposed a model for DNA
  structure
• Nucleotides pair in a certain way to form a
  double helix
• T-A A-T
• (A-U in RNA)
• C-G G-C

Purines
Pyrimidines
Adenine
Guanine
Cytosine
Thymine
Phosphate group
Deoxyribose
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• A strand of DNA is millions and millions of
  nucleotides long and the pattern of the bases
  determines the code.
• One section of DNA a gene, which codes for just
  one trait in organisms. A strand of DNA has
  millions of genes in it.

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2-1

• The particles that move around the nucleus of an
  atom are called
• neutrons.
• protons.
• electrons.
• isotopes.

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2-1

• The atomic number of a carbon atom is 6. How many
  neutrons does the isotope carbon-14 have?
• 6
• 8
• 12
• 14

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2-1

• Which of the following statements about the three
  isotopes of carbon is true?
• They are all radioactive.
• They have different numbers of electrons.
• They have the same chemical properties but differ
  in atomic mass.
• They have the same number of protons and
  neutrons.

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2-1

• A chemical compound consists of
• Electrons mixed with neutrons.
• two or more elements combined in a definite
  proportion.
• two or more elements combined in any proportion.
• at least three elements combined by ionic or
  covalent bonds.

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2-2

• A molecule in which the charges are unevenly
  distributed is called a
• polar molecule.
• cohesive molecule.
• hydrogen molecule.
• covalent molecule.

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2-2

• A dissolved substance is called a
• solvent.
• solution.
• solute.
• Suspension.

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2-2

• A compound that produces hydroxide ions in
  solution is called a(an)
• base.
• buffer.
• acid.
• salt.

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2-2

• Hydrogen bonds between water molecules result
  from
• adhesion between water molecules.
• magnetic attractions between water molecules.
• uneven electron distribution in each water
  molecule.
• ionic bonds in the water molecule.

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2-2

• On a pH scale, a value of 2 means that the
  solution has
• equal concentrations of H and OH- ions.
• the same concentration of H ions as pure water.
• higher concentration of H than in pure water.
• lower concentration of H than in pure water.

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• Large carbohydrate molecules such as starch are
  known as
• lipids.
• monosaccharides.
• proteins.
• polysaccharides.

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• Many lipids are formed from glycerol and
• fatty acids.
• monosaccharides.
• amino acids.
• nucleic acids.