Transcript A View of Life

Chapter 2
Chemistry of Life
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Outline
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Basic Chemistry
– Atoms
– Molecules and Compounds
– Chemical Reactions
Properties of Water
Acids and Bases
Macromolecules
ATP
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Basic Chemistry
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There are 92 naturally-occurring elements.
– Over 90% of human body is composed of
four elements. (CHON)
 Carbon.
 Hydrogen.
 Oxygen.
 Nitrogen.
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Atoms
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An atom is the smallest unit of matter that
retains an element’s physical and chemical
properties.
– Positively-charged protons and neutral
neutrons are located in the nucleus.
– Negatively-charged electrons orbit the
nucleus in shells.
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Atoms
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An element’s atomic number is designated
by its number of protons.
An element’s atomic weight is designated by
its protons and neutrons.
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Elements and Atoms
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Molecules and Compounds
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A molecule and compound is a group of
atoms bonded together.
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Ionic Reactions
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During an ionic reaction, atoms give up or
take on an electron to stabilize their outer
shells of the atom.
Ions are particles that carry a positive (+) or
negative (-) charge.
– The attraction between oppositely
charged sodium ions and chloride ions
forms an ionic bond.
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Ionic “electron stripping” Reaction
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Covalent “electron sharing” Reactions
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In covalent reactions, atoms share electrons
in covalent bonds instead of losing or
gaining them.
– A single bond is formed when atoms
share a single pair of electrons.
– A double bond is formed when atoms
share two pairs of electrons.
– A triple bond is formed when atoms share
three pairs of electrons.
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Covalent Reactions
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Water and Living Things and a Third type of bondHydrogen bond
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The electrons in water spend more time
circling the larger oxygen atom than the
smaller hydrogen atom.
– Water is a polar molecule with the oxygen
end being slightly negative and the
hydrogen end being slightly positive.
 A hydrogen bond occurs when a
covalently bonded hydrogen is positive
and is attracted to a negatively charged
atom.
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Hydrogen Bonding between Water Molecules
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Some Properties of Water
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liquid at room
temperature.
solvent for polar
molecules.
cohesive.
temperature rises and
falls slowly.
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Acids and Bases
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Acids break down in water and release
hydrogen ions (H+).
Bases/alkaline take up hydrogen ions (H+)
or release hydroxide ions (OH-).
– Buffers help keep the pH within normal
limits by taking up excess hydrogen ions
or hydroxide ions.
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Water can break down to form Ions (atoms with a +
or – charge)
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pH Scale
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The pH scale measures acidity or alkalinity
of a solution.
– Neutral = 7.
– Acidic < 7.
– Basic > 7.
 Logarithmic Scale.
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Log scale
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The pH Scale
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Molecules of Life
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Four categories of molecules are unique to
cells.
– Carbohydrates.
– Lipids.
– Proteins.
– Nucleic Acids.
Macromolecules are synthesized by a
dehydration reaction, and degraded by a
hydrolysis reaction.
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pg.24a
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Synthesis of larger product (macromolecule)
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Breakdown of Molecule to simpler subunits
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Carbohydrates
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Carbohydrates function for quick and shortterm energy storage.
– Monosaccharide (simple sugar).
 Glucose.
– Disaccharide.
 Fructose.
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Complex Carbohydrates
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Polysaccharides.
– Starch (plants).
– Glycogen (animals).
– Cellulose (plant cell walls).
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Glucose molecule in various forms
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A Disacharride
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Plant Polysaccharide
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Animal polysaccharide
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Lipids
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Lipids contain more energy per gram than
any other biological molecule.
– Do not dissolve in water.
 Absence of polar groups.
– Fats.
 Animal origin, solid at room temperature.
– Oils.
 Plant origin, liquid at room temperature.
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Synthesis and breakdown of Fat
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Phospholipids and Steroids
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Phospholipids contain a phosphate head
and fatty acid tails.
– Polar head and non-polar tails.
 Soluble in water.
Steroids are lipids with a backbone of four
fused carbon rings.
– Estrogen and testosterone.
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Another Example of a lipid
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Cell membrane
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Other lipid examples
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Fig. 2.15bb
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Emulsyfier
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Bile salts
Tween
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Emulsyfication
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Proteins
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Proteins are macromolecules with amino
acid subunits.
– An amino acid has a central carbon atom
bonded to a hydrogen and three groups.
 Peptide bond - Any bond joining two
amino acids.
 Polypeptide - Single amino acid
chain.
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Building block of proteins
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Fig. 2.16a
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Peptide bond- bond between two amino acids
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Levels of Protein Organization
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Primary Structure.
– Linear sequence of amino acids.
Secondary Structure.
– Polypeptide takes on orientation in space.
Tertiary Structure.
– Final three-dimensional shape.
Quaternary Structure.
– Proteins with more than one polypeptide.
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Nucleic Acids
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Nucleic acids are huge macromolecules
composed of nucleotides.
– A nucleotide is constructed of a
phosphate, a pentose sugar, and a
nitrogenous base.
– Deoxyribonucleic acid (DNA).
 Double-stranded helix.
– Ribonucleic acid (RNA).
 Single stranded.
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Building block of an Nucleic Acid- A Nucleotide
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DNA Structure
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(ATP) Adenosine Triphosphate
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ATP is the primary cellular energy carrier.
– Energy currency of cells.
– Breaks down to adenosine diphosphate
(ADP) and a molecule of inorganic
phosphate, releasing energy to drive
cellular metabolism.
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Another nucleic acid example- ATP and ADP (cell
energy)
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Lecture Review
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Give an example of ionic bonding and explain it.
Give an example of covalent bonding and explain
it.
Relate the characteristics of water to its polarity
and hydrogen bonding.
List the four molecules of life and examples of
each.
Fat /triglyceride is composed of______ and
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The subunits of Proteins are _______ _______.
List some functions of proteins. What is a
polypeptide?
The subunits of Nucleic acids are ____________.
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