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Chapter 6
Chemistry in Biology
6.1 Atoms, Elements, and Compounds
Atoms
 Chemistry is the study of matter.
 Atoms are the building blocks of matter.
 Neutrons and protons are located at the
center of the atom.
 Protons are positively charged particles.
 Neutrons are particles that have no charge.
Chapter 6
Chemistry in Biology
6.1 Atoms, Elements, and Compounds
 Electrons are negatively charged particles that
are located outside the nucleus.
Electron Arrangement
• Electrons are organized in different energy
levels or shells
• The inner most level can hold 2 electrons
• 2e, 8e, 8e, 18e, 18e, 32e, 32e
• Valence Electrons:
the electrons in the
outermost level
• These are responsible
for atoms bonding
together
Chapter 6
Chemistry in Biology
6.1 Atoms, Elements, and Compounds
Elements
 Element: is a pure substance that cannot be
broken down into other substances by
physical or chemical means.
 Each element has a unique name and symbol.
Element Examples
Chapter 6
Chemistry in Biology
6.1 Atoms, Elements, and Compounds
The Periodic Table of Elements
 Horizontal rows are called periods.
Tells the number of energy levels in each
row
 Vertical columns are called groups or
families.
Tells the number of valence electrons in
each family
Chapter 6
Chemistry in Biology
6.1 Atoms, Elements, and Compounds
Compounds:
 A pure substance formed when two or more
elements combine
 Compounds are always formed from a specific
combination of elements in a fixed ratio.
 Compounds cannot be broken down into
simpler compounds or elements by physical
means.
Compound Examples
• NaCl
• 5 H2O
• 7 CaCl2
Chapter 6
Chemistry in Biology
6.1 Atoms, Elements, and Compounds
Isotopes
 Atoms of the same element that have the
same number of protons and electrons but
have a different number of neutrons
• Elements are held together in compounds by
bonds.
• There are 2 main types of bonds:
• Covalent
• Ionic
Chapter 6
Chemistry in Biology
6.1 Atoms, Elements, and Compounds
Chemical Bonds
 Covalent bonds
 Chemical bond that
forms when electrons
are shared
 Occurs between nonmetals
Chapter 6
Chemistry in Biology
6.1 Atoms, Elements, and Compounds
Ionic Bonds
 Electrical attraction between two oppositely
charged atoms (ions) or groups of atoms
Chapter 6
Chemistry in Biology
• Atoms are donated or gained
• Occurs between metals and non-metals
Chapter 6
Chemistry in Biology
6.1 Atoms, Elements, and Compounds
 The elements identified as metals tend to
donate electrons.
 The elements identified as nonmetals tend
to accept electrons.
• Atomic number = number of protons
• Atomic Mass = average mass of all the
isotopes of an element
– You can round this to find the mass number for
the most common isotope of the element
• Mass number = protons + neutrons
6.2 Chemical Reactions
• 2 H + O → H2O
• Which side contains the reactant(s)?
• The product(s)?
• What makes this reaction occur?
Chapter 6
Chemistry in Biology
6.2 Chemical Reactions
Energy of Reactions
 Activation energy is
the minimum amount
of energy needed for
reactants to form
products in a
chemical reaction.
Chapter 6
Chemistry in Biology
6.2 Chemical Reactions
 This reaction is
exothermic and
released heat energy.
 The energy of the
product is lower than
the energy of the
reactants.
Chapter 6
Chemistry in Biology
6.2 Chemical Reactions
 This reaction is
endothermic and
absorbed heat energy.
 The energy of the
products is higher
than the energy of
the reactants.
• We will learn about biological catalysts in the
near future!
6.4 The Building Blocks of Life
• All living things are compose of organic
molecules
• The six most common elements found in
organic molecules include:
C, H, N, O, P, S.
Chapter 6
Chemistry in Biology
6.4 The Building Blocks of Life
Organic Chemistry
 The element carbon
is a component of
almost all biological
molecules.
Chapter 6
Chemistry in Biology
6.4 The Building Blocks of Life
Macromolecules
 Carbon atoms can be joined to form carbon
molecules.
 Macromolecules are large molecules formed
by joining smaller organic molecules together.
 Monomers: small, repeating organic
molecules that usually form larger molecules
 They are also called biological polymers
• There are four major macromolecules
associated with biology:
• Carbohydrates
• Lipids
• Proteins
• Nucleic acids
Chapter 6
Chemistry in Biology
Chapter 6
Chemistry in Biology
6.4 The Building Blocks of Life
Carbohydrates
 Compounds composed of carbon, hydrogen, and
oxygen in a ratio of 1C: 2H: 1O
 General formula: (CH2O)n
Chapter 6
Chemistry in Biology
6.4 The Building Blocks of Life
 If n is between three and seven the compound
is called a simple sugar or monosaccharide.
 Ex. C6H12O6
 Glucose is one very important
monosaccharide used by cells for energy
• It is found in the human bloodstream
 Two monosaccharides joined together form a
disaccharide.
 Sucrose and lactose are two examples of
disaccharides.
 Sucrose is table sugar
 Lactose is milk sugar
How are disaccharides formed?
• Dehydration synthesis: formation of
disaccharide by removing water from the
monosaccharides
 Longer carbohydrate molecules are called
polysaccharides.
 Glycogen is an example of a polysaccharide.
 Animals store it in the liver
 It is a short term energy storage molecule
How do organisms get energy from
these?????
• The bonds between them are broken,
releasing energy
• Hydrolysis: adding water to split a
disaccharide or polysaccharide and release
energy
Functions of Carbohydrates:
• Primary source of energy for organisms
• Structural support in plants (cellulose)
• Main component in shells (chitin)
Carbohydrates Are:
• Manufactured by green plants only:
• Occurs during photosynthesis
• 6 CO2 + 6 H2O → C6H12O6 + 6 O2
Chapter 6
Chemistry in Biology
6.4 The Building Blocks of Life
Lipids
 Molecules made mostly of carbon and
hydrogen
 Make Up:
Fats
Oils
Waxes
Functions of Lipids
 Primary function is to store energy
 Make up cell structures
 Form chemical messages between cells
 Protection (wax on plant leaves)
Lipid Structure:
• Fatty acid tail
• Fatty acid tail is a chain of carbon atoms
bonded to hydrogen atoms and other carbon
atoms by single or double bonds
• The bonds determine if the lipid is classified
as saturated, unsaturated or polyunsaturated
Basic Structure of Lipids
Chapter 6
Chemistry in Biology
6.4 The Building Blocks of Life
Saturated fats have tail chains with only single
bonds between the carbon atoms.
 Unsaturated fats: lipids that have at least
one double bond between carbon atoms in
the tail chain
 Fats with more than one double bond in the
tail are called polyunsaturated fats.
Important Biological Lipids:
• Phospholipids: create the structure and
function of the cell membrane
• Hydrophilic head: dissolves in water
• Hydrophobic tail: does not dissolve in
water
• Why is this important?
Lipids
• Also, responsible for the formation of
important steroids including hormones and
cholesterol
Chapter 6
Chemistry in Biology
6.4 The Building Blocks of Life
Protein
 A compound made of small carbon compounds
called amino acids
 Amino acids are small compounds that are
made of carbon, nitrogen, oxygen,
hydrogen, and sometimes sulfur.
Chapter 6
Chemistry in Biology
6.4 The Building Blocks of Life
 Amino acids have a central carbon atom.
 One of the four carbon bonds is with hydrogen.
 The other three bonds are with an amino group
(–NH2), a carboxyl group (–COOH), and a variable
group (–R).
Chapter 6
Chemistry in Biology
• Amino acids are bonded together in a chain
by peptide bonds
• Proteins are also called polypeptides
Protein Functions:
• Make up mass
• Involved in almost all functions
– Structure
– Chemical signals between cells
– Control cell growth and repair
– Enzymes (biological catalysts)
Enzymes
• Enzymes: biological catalysts
• Made of proteins
Chapter 6
Chemistry in Biology
6.2 Chemical Reactions
Enzymes
 Catalyst is a substance
that lowers the activation
energy needed to start a
chemical reaction.
 Activation energy: the minimum amount of
energy needed for reactants to form products
in a chemical reaction.
• It does not increase how much product is
made.
• It does not get used up in the reaction.
• How do enzymes work?
Chapter 6
Chemistry in Biology
6.2 Chemical Reactions
Substrates: Reactants that bind to the enzyme
Active site: Specific location where a substrate
binds on an enzyme
Chapter 6
Chemistry in Biology
6.2 Chemical Reactions
 The active site changes shape and forms the
enzyme-substrate complex, which helps
chemical bonds in the reactants to be broken
and new bonds to form.
 Factors such as pH, temperature, and other
substances affect enzyme activity.
Chapter 6
Chemistry in Biology
• Nucleic Acids:
• Made up of smaller subunits called
nucleotides
• Nucleotides consist of carbon, nitrogen,
oxygen, phosphorus, and hydrogen atoms
Nucleic Acid Functions:
• Store and transmit genetic information
• Two types of nucleic acids:
– DNA
– RNA