The Chemical Level of Organization professor edit
Transcript of The Chemical Level of Organization professor edit
© 2012 Pearson Education, Inc.
PowerPoint® Lecture Presentations prepared by
Jason LaPres
Lone Star College—North Harris
2 The Chemical Level of Organization__professor edit
© 2012 Pearson Education, Inc.
An Introduction to the Chemical Level of
Organization • Chemistry
• Is the science of that deals with the structure of
matter
• Matter is defined as anything that takes up space
and has mass (weight)
• Topics of this chapter include:
• The structure of atoms
• The basic chemical building blocks
• How atoms combine to form increasingly complex
structures
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2-1 Atoms and Atomic Structure
• Matter
• Atoms are the basic particles of matter
• Atoms join together to form chemicals with different
characteristics
What do atoms have to do with the human body?
Think, pair, share…..
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2-1 Atoms and Atomic Structure
• Elements
• Pure substance composed of atoms of only one
kind.
• Cannot be broken down into simpler substances
• Carbon is always carbon, oxygen is always oxygen
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Can you give examples of what happens to the human
body when there is too much or too little of these
elements?
-calcium
-sodium
-iron
Think, pair, share…..
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2-1 Atoms and Atomic Structure
• Atoms are composed of subatomic particles
• Proton p+
• Positive charge
• Neutron n
• Neutral, similar to size and mass of a proton
• Electron e-
• Negative charge, much lighter than protons
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2-1 Atoms and Atomic Structure
• Atomic Structure
• Atomic number
• Number of protons
• Nucleus
• Contains protons and neutrons
• Electron cloud
• Contains electrons (which are attracted to protons)
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Figure 2-2 The Arrangement of Electrons into Energy Levels
The first energy level
can hold a maximum of
two electrons.
The second and third
energy levels can
each contain up to 8
electrons.
Hydrogen, H
Atomic number: 1
1 electron
Lithium, Li
Atomic number: 3
(3 protons 3 neutrons)
3 electrons
Hydrogen (H). A typical hydrogen atom has one proton and one electron. The electron orbiting the nucleus occupies the first energy level, diagrammed as an electron shell.
Helium (He). An atom of helium has two protons, two neutrons, and two electrons. The two electrons orbit in the same energy level.
Neon, Ne
Atomic number: 10
(10 protons 10 neutrons)
10 electrons
Lithium (Li). A lithium atom has three protons, three neutrons, and three electrons. The first energy level can hold only two electrons, so the third electron occupies a second energy level.
Neon (Ne). A neon atom has 10 protons, 10 neutrons, and 10 electrons. The second level can hold up to eight electrons; thus, both the first and second energy levels are filled.
Helium, He
Atomic number: 2
(2 protons 2 neutrons)
2 electrons
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2-1 Atoms and Atomic Structure
• Electrons and Energy Levels
• Electrons in the electron cloud determine the reactivity of an
atom
• The electron cloud contains shells, or energy levels that hold a
maximum number of electrons
• Lower shells fill first
• Outermost shell is the valence shell, and it determines
bonding
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2-2 Molecules and Compounds
• Chemical Bonds
• Involve the sharing, gaining, and losing of electrons in the
valence shell
• Three major types of chemical bonds
1. Ionic bonds
• Attraction between cations (+ charged) and anions (- charged)
2. Covalent bonds
• Strong electron bonds involving shared electrons
3. Hydrogen bonds
• Weak polar bonds based on partial electrical attractions
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2-2 Molecules and Compounds
• Chemical Bonds
• Form molecules and/or compounds
• Molecules
• Two or more atoms joined by strong bonds
• Compounds
• Two or more atoms OF DIFFERENT ELEMENTS
joined by strong or weak bonds
• Compounds are all molecules, but not all molecules are
compounds
• H2 = molecule only H2O = molecule and compound
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2-2 Molecules and Compounds
• Ionic Bonds
• One atom—the electron donor—loses one or more
electrons and becomes a cation, with a positive
charge (if you lose negativity, you become positive)
• Another atom—the electron acceptor—gains those
same electrons and becomes an anion, with a
negative charge (if you gain negativity, you become
more negative)
• Attraction between the opposite charges then draws
the two ions together Opposites attract!
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Figure 2-3a The Formation of Ionic Bonds
Formation of ions
Sodium atom Sodium ion (Na)
Attraction between opposite charges
Formation of an ionic compound
Sodium chloride (NaCl)
Chloride ion (Cl) Chlorine atom
Formation of an ionic bond. A sodium (Na) atom loses an electron, which is accepted by a chlorine (Cl) atom. Because the sodium (Na) and chloride (Cl) ions have opposite charges, they are
attracted to one another. The association of sodium and chloride ions forms the ionic compound sodium chloride.
1
3
2
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Figure 2-3b The Formation of Ionic Bonds
Chloride ions
(Cl)
Sodium ions
(Na)
Sodium chloride
crystal. Large
numbers of sodium and
chloride ions form a
crystal of sodium
chloride (table salt).
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2-2 Molecules and Compounds
• Covalent Bonds
• Involve the sharing of pairs of electrons between
atoms
• One electron is donated by each atom to make the pair
of electrons
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Figure 2-4 Covalent Bonds in Four Common Molecules
Molecule Electron Shell Model and
Structural Formula
Hydrogen
(H2)
Oxygen
(O2)
Carbon
dioxide
(CO2)
Nitric
oxide
(NO)
HH
OO
OCO
NO
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2-2 Molecules and Compounds
• Covalent Bonds
• Nonpolar covalent bonds
• Involve equal sharing of electrons because atoms
involved in the bond have equal pull for the electrons
• Polar covalent bonds
• Involve the unequal sharing of electrons because one
of the atoms involved in the bond has a
disproportionately strong pull on the electrons
• Form polar molecules — like water
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Figure 2-5 Polar Covalent Bonds and the Structure of Water
Hydrogen atom
Hydrogen atom
Hydrogen atom
Oxygen atom
Oxygen atom
2
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2-2 Molecules and Compounds
• Hydrogen Bonds
• Bonds between adjacent molecules, not atoms
• Involve slightly positive and slightly negative
portions of polar molecules being attracted to one
another
• Hydrogen bonds between H2O molecules cause
surface tension
• Because of the extensive hydrogen bonding in water, the molecules tend to
stick to each other in a regular pattern. The tension on the surface of water
occurs when water molecules on the outside of the system align and are
held together by hydrogen bonding to create an effect similar to a net made
of atoms. For example, the surface tension of water allows water spiders to
literally walk on water.
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Figure 2-6 Hydrogen Bonds between Water Molecules
KEY
2
Hydrogen
Oxygen
Hydrogen bond
2
2
2
2 2
2
Do you see the
net/regular pattern
being formed?
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2-2 Molecules and Compounds
• States of Matter
• Solid
• Constant volume and shape
• Liquid
• Constant volume but changes shape
• Gas
• Changes volume and shape
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2-3 Chemical Reactions
• In a Chemical Reaction
• Either new bonds are formed or existing bonds are broken
• Reactants
• Materials going into a reaction
• Products
• Materials coming out of a reaction
• Metabolism
• All of the reactions that are occurring at one time
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Figure 2-7 Chemical Notation
Atoms
The symbol of an element indicates one atom of that element. A number preceding the symbol of an element indicates more than one atom of that element.
VISUAL REPRESENTATION CHEMICAL NOTATION
one atom
of hydrogen one atom
of hydrogen
one atom
of oxygen
one atom
of oxygen
two atoms
of hydrogen
two atoms
of hydrogen
two atoms
of oxygen two atoms
of oxygen
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Figure 2-7 Chemical Notation
Molecules
A subscript following the symbol of an element indicates a molecule with that number of atoms of that element.
hydrogen molecule composed of two
hydrogen atoms
hydrogen
molecule composed of two
oxygen atoms
oxygen
molecule
oxygen molecule
water molecule composed
of two hydrogen atoms
and one oxygen atom
water
molecule
VISUAL REPRESENTATION CHEMICAL NOTATION
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Figure 2-7 Chemical Notation
In a description of a chemical reaction, the participants at the start of the reaction are called
reactants, and the reaction generates one or more products. An arrow indicates the direction of
the reaction, from reactants (usually on the left) to products (usually on the right). In the following
reaction, two atoms of hydrogen combine with one atom of oxygen to produce a single molecule
of water.
Reactions
Chemical reactions neither create nor destroy
atoms; they merely rearrange atoms into new
combinations. Therefore, the numbers of atoms
of each element must always be the same on
both sides of the equation for a chemical
reaction. When this is the case, the
equation is balanced.
Balanced equation
Unbalanced equation
VISUAL REPRESENTATION CHEMICAL NOTATION
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Figure 2-7 Chemical Notation
Ions
A superscript plus or minus sign following the symbol of an element indicates an ion. A single plus
sign indicates a cation with a charge of 1. (The original atom has lost one electron.) A single minus
sign indicates an anion with a charge of 1. (The original atom has gained one electron.) If more than
one electron has been lost or gained, the charge on the ion is indicated by a number preceding the
plus or minus sign.
sodium ion chloride ion calcium ion sodium
ion
chloride
ion calcium
ion the chlorine
atom has gained
one electron
the calcium
atom has lost
two electrons
A sodium atom becomes a sodium ion
Electron lost
Sodium atom (Na)
Sodium ion (Na)
the sodium
atom has lost
one electron
VISUAL REPRESENTATION CHEMICAL NOTATION
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2-3 Chemical Reactions
• Basic Energy Concepts
• Energy
• The power to do work
• Work
• A change in mass or distance
• Kinetic energy
• Energy of motion
• Potential energy
• Stored energy
• Chemical energy
• Potential energy stored in chemical bonds
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2-3 Chemical Reactions • Breaking chemical bonds
• AB A + B
• Hydrolysis (You are breaking up A-B [hydro = water; lysis =
break]; A-H and HO-B are the products)
• A-B + H2O A-H + HO-B
• Forming chemical bonds
• A + B AB
• Dehydration synthesis (You are removing water from A and B
[dehydrating them]; water and A-B are the products)
• A-H + HO-B A-B + H2O
Forming A-B
Breaking A-B
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2-4 Enzymes
• Chemical Reactions
• In cells cannot start without help
• Activation energy is the amount of energy needed to
get a reaction started
• Enzymes are protein catalysts that lower the
activation energy of reactions
• Promote the chemical reaction
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Figure 2-8 The Effect of Enzymes on Activation Energy
Without
enzyme
Activation energy
required
Reactants
Stable
product
With enzyme
En
erg
y
Progress of reaction
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2-5 Organic and Inorganic Compounds
• Nutrients
• Essential molecules obtained from food
• Metabolites
• Molecules made or broken down in the body
• Inorganic Compounds
• Molecules not based on carbon and hydrogen
• Carbon dioxide, oxygen, water, and inorganic acids, bases, and salts
• Organic Compounds
• Molecules based on carbon and hydrogen
• Carbohydrates, proteins, lipids, and nucleic acids
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2-6 Properties of Water
• Water
• Accounts for up to two-thirds of your total body weight
• A solution is a uniform mixture of two or more
substances
• It consists of a solvent (water) in which atoms,
ions, or molecules of another substance, called a
solute (NaCl—table salt), are individually
dispersed
• Concentration
• The amount of solute in a solvent (a salty solution
like brine has a high concentration of NaCl)
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2-6 Properties of Water
• Solubility
• Water’s ability to dissolve a solute in a solvent to
make a solution
• Reactivity
• Most body chemistry occurs in water
• High Heat Capacity
• Water’s ability to absorb and retain heat
• Lubrication
• To moisten and reduce friction (think about joints)
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2-6 Properties of Water
• High Heat Capacity
• When molecules are heated, they get excited. They
move around faster as they gain more energy. Water
is a polar molecule (has a plus end and a minus end).
Positive attracts to negative and water molecules
stick together through strong bonds. Because the
molecules are being held tightly in place by these
bonds, the H2O molecules do not move much when
heated. It takes more and more heat to move the
molecules, causing water to have a high specific heat
capacity.
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2-6 Properties of Water
• The Properties of Aqueous Solutions
• Ions and polar compounds undergo ionization, or
dissociation in water
• NaCl becomes Na+ ion and Cl- ion in water
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2-6 Properties of Water
• The Properties of Aqueous Solutions
• Electrolytes and body fluids
• Electrolytes are inorganic ions that conduct electricity
in solution
• Electrolyte imbalance seriously disturbs vital body
functions
Why is electricity important in our body?
Think, pair, share…
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2-6 Properties of Water
• The Properties of Aqueous Solutions
• Hydrophilic and hydrophobic compounds
• Hydrophilic
• hydro- = water, philos = loving
• Interacts with water
• Includes ions and polar molecules
• Hydrophobic
• phobos = fear
• Does NOT interact with water
• Includes nonpolar molecules, fats, and oils
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2-7 pH and Homeostasis
• pH
• The concentration of hydrogen ions (H+) in a solution
• Neutral pH
• A balance of H+ (hydrogen) and OH (hydroxide)
• Pure water = 7.0
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2-7 pH and Homeostasis
• Acidic pH Lower Than 7.0
• High H+ concentration
• Low OH concentration
• Basic (or alkaline) pH Higher Than 7.0
• Low H+ concentration
• High OH concentration
• pH of Human Blood
• Ranges from 7.35 to 7.45
Where in the body is
the pH not near 7?
Think, pair, share….
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2-7 pH and Homeostasis
• pH Scale
• Has an inverse relationship with H+ concentration
• More H+ ions mean lower pH, less H+ ions mean higher
pH
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Figure 2-10 pH and Hydrogen Ion Concentration
1 mol/L
hydrochloric
acid
Stomach
acid
Beer,
vinegar,
wine,
pickles
Tomatoes,
grapes
Extremely
acidic Increasing concentration of H Neutral Increasing concentration of OH Extremely
basic
Urine
Saliva,
milk
Blood Ocean water Pure
water Eggs
Household bleach Household
ammonia
Oven cleaner
1 mol/L sodium
hydroxide
14 13 12 11 9 10
1014 1013 1012 1011 1010 109 8
108 7
107 6
106 5
105 4
104 3
103 2
102 1
101 pH [H]
0 100
(mol/L)
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2-8 Inorganic Compounds
• Acid
• A solute that adds hydrogen ions to a solution
• Proton donor
• Strong acids dissociate completely in solution
• Base
• A solute that removes hydrogen ions from a solution
• Proton acceptor
• Strong bases dissociate completely in solution
• Weak Acids and Weak Bases
• Fail to dissociate completely
• Help to balance the pH
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2-8 Inorganic Compounds
• Buffers and pH Control
• Buffers
• Weak acid/salt compounds
• Neutralize either strong acid or strong base
• Sodium bicarbonate is very important in humans
• Antacids
• Basic compounds that neutralize acid and form a salt
• Alka-Seltzer, Tums, Rolaids, etc.
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2-9 Carbohydrates
• Organic Molecules
• Contain H, C, and usually O
• Are covalently bonded
• Contain functional groups that determine chemistry
• Carbohydrates
• Lipids
• Proteins (or amino acids)
• Nucleic acids
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2-9 Carbohydrates
• Carbohydrates
• Ex:
• Monosaccharide — simple sugar
• Disaccharide — two sugars
• Polysaccharide — many sugars
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2-9 Carbohydrates
• Monosaccharides
• Simple sugars
• Glucose, fructose, galactose
• Disaccharides
• Two simple sugars combined by a chemical reaction
• Sucrose, maltose
• Polysaccharides
• Many monosaccharides combined by a chemical reaction
• Glycogen, starch, cellulose
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Table 2-4 Carbohydrates in the Body
Why are carbohydrates important? What
are the consequences of a “low carb” diet?
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2-10 Lipids
• Lipids
• Mainly hydrophobic molecules such as fats, oils, and waxes
• Made mostly of carbon and hydrogen atoms with a –COOH at
the end (carbon, oxygen, and hydrogen)
• Include:
• Fatty acids
• Eicosanoids
• Glycerides
• Steroids
• Phospholipids and glycolipids
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2-10 Lipids
• Fatty Acids
• Long chains of carbon and hydrogen
• Are relatively nonpolar
• Fatty acids may be:
• Saturated with hydrogen (no covalent bonds)
• Unsaturated (one or more double bonds)
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Figure 2-14b Fatty Acids
Unsaturated
A fatty acid is either saturated (has single
covalent bonds only) or unsaturated (has
one or more double covalent bonds). The
presence of a double bond causes a
sharp bend in the molecule also known as a “kink”
Saturated
Single bonds
create a
straight
molecule,
which can be
easily packed
together to
form a solid at
room
temperature,
like butter.
The double
bond
introduces a
kink in the
structure
(cannot pack
as tightly), so
it forms a
liquid, like
olive oil.
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2-10 Lipids
• Eicosenoids:
• Leukotrienes
• Active in immune system
• Prostaglandins
• Local hormones, short-chain fatty acids
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2-10 Lipids
• Glycerides
• Fatty acids attached to a glycerol molecule
• Have three important functions
1. Energy source
2. Insulation
3. Protection
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2-10 Lipids
• Steroids
• Types of steroids:
• Cholesterol
• Component of plasma (cell) membranes
• Estrogens and testosterone
• Sex hormones
• Corticosteroids and calcitriol
• Metabolic regulation
• Bile salts
• Derived from steroids
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2-10 Lipids
• Phospholipids and Glycolipids
• Contain either a phosphate group (phospholipid) or a
sugar (glycolipid)
• Generally, both have hydrophilic heads and
hydrophobic tails and are structural lipids,
components of plasma (cell) membranes
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Figure 2-18c Phospholipids and Glycolipids
WATER
Hydrophilic
heads
Hydrophobic
tails
Phospholipid Glycolipid
In large numbers,
phospholipids and
glycolipids form micelles,
with the hydrophilic
heads facing the water
molecules, and the
hydrophobic tails on the
inside of each droplet.
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Table 2-5 Representative Lipids and Their Functions in the Body
What happens when you eat too much saturated fats?
Think, pair, share…
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2-11 Proteins
• Proteins
• Are the most abundant and important organic
molecules
• Contain basic elements
• Carbon (C), hydrogen (H), oxygen (O), and nitrogen (N)
• Basic building blocks
• 20 amino acids
DNARNAPROTEIN Genetic
information
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2-11 Proteins
1. Support
• Structural proteins
2. Movement
• Contractile
proteins
3. Transport
• Transport (carrier)
proteins
4. Buffering
• Regulation of pH
5. Metabolic Regulation
• Enzymes
6. Coordination and Control
• Hormones
7. Defense
• Antibodies
• Seven Major Protein Functions
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Figure 2-19 Amino Acids
Structure of an Amino Acid
Nitrogen containing group
Central carbon
-COOH group
•R group
•Different amino acids have different
•R groups.
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2-11 Proteins
• Hooking Amino Acids Together
• Requires a dehydration synthesis
• Forms a peptide bond
• Resulting molecule is a peptide
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Figure 2-20 The Fomation of Peptide Bonds
Peptide Bond Formation
Glycine (gly) Alanine (ala)
HYDROLYSIS DEHYDRATION
SYNTHESIS
Peptide bond
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2-11 Proteins
• Protein Shape
• Primary structure
• The sequence of amino acids along a polypeptide
• Secondary structure
• Hydrogen bonds form spirals or pleats
• Tertiary structure
• Secondary structure folds into a unique shape
• Quaternary structure
• Final protein shape — several tertiary structures together
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Figure 2-21 Protein Structure
A1 A2 A3 A4 A5 A8 A6 A7 A9
A1 A2 A3 A4
A5
A6 A7 A9 A8
A10
A11 A12 A13 A14
Pleated sheet
Hydrogen bond
OR
Alpha-helix
Hydrogen
bond
A1
A2
A3 A5
A6
A7 A9
Linear chain of amino acids
OR
Heme units
Hemoglobin
(globular protein)
Keratin or collagen
(fibrous protein)
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2-11 Proteins
• Fibrous Proteins
• Structural sheets or strands
• Globular Proteins
• Soluble spheres with active functions
• Protein function is based on shape
• Shape is based on sequence of amino acids
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2-11 Proteins
• Enzyme Function
• Enzymes are catalysts
• Proteins that lower the activation energy of a chemical
reaction
• Are not changed or used up in the reaction
• Enzymes also exhibit:
1. Specificity — will only work on limited types of
substrates (lock and key)
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Figure 2-22 A Simplified View of Enzyme Structure and Function
Substrates bind to active site of enzyme
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Figure 2-22 A Simplified View of Enzyme Structure and Function
Once bound to the active site, the substrates are held together and their interaction facilitated
Enzyme-substrate
complex
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Figure 2-22 A Simplified View of Enzyme Structure and Function
Substrate binding alters the shape of the enzyme, and this change promotes product formation
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Figure 2-22 A Simplified View of Enzyme Structure and Function
Product detaches from enzyme; entire process can now be repeated
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2-11 Proteins
• Cofactors and Enzyme Function
• Cofactor
• An ion or molecule that binds to an enzyme before
substrates can bind
• Coenzyme
• Nonprotein organic cofactors (vitamins)