Chapter 2

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Transcript Chapter 2

Chapter 2
The Chemistry of Life
Section 1 – The Nature of Matter
• Atoms are the basic unit of matter.
• Subatomic particles that make up atoms are
protons, neutrons, and electrons.
• Protons – positively charged particles
• Neutrons – carry no charge, neutral
• Protons and neutrons are found in the nucleus
of the atom
Electrons
• Electron – negatively charged particle
• In constant motion in the space surrounding
the nucleus.
Elements
• Element – pure substance that consists
entirely of one type of atom.
– Represented by a one- or two- letter symbol.
– Elements are arranged into the periodic table.
Chemical Compounds
• A chemical compound is a substance formed
by the chemical combination of two or more
elements in definite proportions.
Chemical Bonds
• Ionic bonds – formed when one or more
electrons are transferred from one atom to
another.
• Covalent bonds – formed when electrons are
shared between atoms.
• Van der Waals forces – when molecules are
close together, a slight attraction can develop
between oppositely charged regions of nearby
molecules. These attractions are not as strong
as ionic or covalent bonds.
Section 2 - Properties of Water
• Polarity – a molecule in which the charges are
unevenly distributed is a polar molecule.
– A water molecule is polar because there is an
uneven distribution of electrons between the
oxygen and hydrogen atoms.
Hydrogen Bonds
• A single water molecule may be involved in as
many as four hydrogen bonds at the same
time.
– Cohesion: an attraction between molecules of the
same substance.
– Adhesion: an attraction between molecules of
different substances.
Mixture
• Mixture – a material composed of two or
more elements or compounds that are
physically mixed together but not chemically
combined.
Solutions
• Solution – all components are evenly
distributed throughout.
– Solute – the substance that is dissolved
– Solvent – the substance in which the solute
dissolves
Suspensions
• Suspension – mixture of water and nondissolved materials.
– Materials will separate into pieces but do not
settle out
Acids, Bases and pH
• The pH scale – a measurement system that
indicates the concentration of H+ ions in a
solution.
– Ranges from 1 – 14
– 7 is neutral
– Under 7 is acidic
– Above 7 is basic
Acids
• Any compound that forms H+ ions in
solutions.
– pH value below 7
Bases
• Any compound that produces hydroxide (OH-)
ions.
– pH value above 7
Buffers
• Weak acids or bases that can react with strong
acids or bases to prevent sharp, sudden
changes in pH.
– Help control pH and retain homeostasis in the
body.
Section 3 – Carbon Compounds
• Macromolecule: LARGE carbon molecule
• Polymer: Large molecule formed when many
smaller molecules bond together
Carbohydrates
• 2 H atoms for every O & C
– 1. Simplest carbs: Called Monosaccharides
(one sugar)
-Ex: glucose; fructose
- 2. Disaccharides – two sugars
-Sucrose (glucose + fructose)
- 3. Polysaccharides – many sugars
-Starch, glycogen, and cellulose
Lipids
• Lipids: Fats; Organic compounds that have a
large proportion of C-H bonds and less O than
carbs.
• Insoluble in water because lipids are nonpolar
• Saturated Fat: Animal fats
• Unsaturated Fat: Oils
Proteins
• A large, complex polymer composed of
carbon, hydrogen, oxygen, nitrogen, and
usually sulfur; have an “R” group that makes
each different
• Made from amino acids
• 20 common amino acids
• Proteins are the building blocks of many
structural components
Proteins
• Amino Acids are linked together when an Hgroup and –OH group are removed to form
water
• The covalent bond formed between A.A. is a
PEPTIDE BOND
Nucleic Acids
• A complex macromolecule that stores cellular
info. in the form of a code
• Nucleic acids are made up of smaller subunits
called Nucleotides
• Nucleotides consist of three basic parts:
– 1. Nitrogen-containing base
– 2. Pentose sugar
– 3. Phosphate group
Types of Nucleic Acids
• 1. DNA: Deoxyribonucleic acid
– Master copy of organism’s genetic info.
– Contains instructions used to form organism’s
enzymes and proteins
2. RNA: Ribonucleic acid
– Forms a copy of DNA for use in making copies and
proteins
Section 4 - Chemical Reactions
• Chemical formulas describe the substances in
the reaction and arrows indicate the process
of change
• Reactants – starting substances on the left
side of the arrow
• Products – substances formed during the
reaction on the right side of arrow
• Arrow can be read as “yields” or “react to
form”
Energy in Reactions
• Key to starting a chemical reaction is energy
• Energy in the form of heat is need
• Most compounds in living things cannot
undergo chemical reactions without energy
Activation Energy
• Minimum amount of energy needed for
reactants to form products in a chemical
reaction
Energy Change in Chemical
Reactions
• In every chemical reaction, there is a change in
energy due to the making and breaking of chemical
bonds
• Exothermic reactions – energy of the product is
lower than the energy of the reactants
– Energy is released in the form of heat
• Endothermic reactions – energy of the products is
higher than the energy of the reactant
– Heat energy is absorbed
Endothermic Reaction
Exothermic Reaction
Enzymes
• Catalyst – substance that lowers the activation
energy needed to start a chemical reaction
• Enzymes – special proteins that are the biological
catalysts that speed up the rate of chemical reactions
in biological processes
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Essential to life
Not used up by the chemical reaction
Can be used again
Most enzymes are specific to one reaction
Enzymes
• Substrates – reactants that bind to the
enzyme
• Active Site – specific location where a
substrate binds on an enzyme
– The active site and substrates have
complementary shapes
– Only the substrate with the same shape as the
active site will bind to the enzyme
– Example : Lock & Key
Enzymes
• Once the substrates bind to the active site, the
site changes shape and forms the enzymesubstrate complex
• The new complex helps chemical bonds in the
reactants to be broken and new bonds are
formed
• The substrates react to form products
• The enzyme then releases the products
•
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Enzymes
• Factors such as pH, temperature, and other
substances affect enzyme activity
• Enzymes affect many biological processes
– Examples:
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Photosynthesis
Respiration
Snake bite
Fruit ripening