Transcript Biochemistry

Biochemistry
I. Elements and Atoms
A. Elements
1. Introduction
a. A substance that is made up of only one type of
atom.
b. 92 natural elements
c. elements names are abbreviated by a symbol
2. Elements of living organisms
a. living organisms are composed of 6 main
elements.
Carbon, hydrogen, oxygen, nitrogen,
phosphorus, sulfur
Table 2-1
Briefly describe some benefits and
limitations of Trace Elements
Trace elements
Elements used by an organism in very small
amounts making up less than .01% of the human
body weight..
b. Examples of trace elements:
iron – hemoglobin carries oxygen in the
blood. A deficiency can cause anemia.
iodine – normal activity of the thyroid
gland. A deficiency can cause a goiter.
magnesium – chlorophyll of your cells
Check Your Understanding
1. Is a trace element an essential element?
Explain? Yes, because an organism requires
them for survival if only in small
amounts.
2. Iron (Fe) is a trace element required for
the proper functioning of hemoglobin ,
the molecule that carries oxygen in red
blood cells. What might be the effects of
an iron deficiency?
The person can have low oxygen in the blood or too
few red blood cells commonly known as anemia.
Do you know what makes up the
periodic table?
•
1. Elements-is a pure substance that
consist entirely of one type of atom.
2. Atom-the basic unit of matter(meaning
it can not be cut).
B. Atoms
1. Introduction
a. the smallest particle of an element that has the
characteristics of that element.
2. Atoms structure
a. Neutrons - uncharged subatomic particles found
in the nucleus
b. Protons - positively charged particles found in the
nucleus
c. Electrons - negatively charge particles found
outside the nucleus
• d. Atomic number - the number of protons and
electrons in a specific atom’s nucleus.
• e. Atomic mass/weight - the number of protons
and neutrons in a specific atom’s nucleus. This is
the size of the atom.
On the empty slide, create your own periodic table
key for the element your teacher gives you. Atomic
mass
Name
Atomic
Number
Symbol
f. number of electrons equals the number of protons, therefore
an atom is neutral. The positive protons and negative
electrons cancel each other out, but this does not mean
they are stable.
g. The number of neutrons= Atomic mass - Atomic number
Calculate the # of neutrons for this element
35.45-17=18 neutrons
Go back to your blank slide, calculate the number of
neutrons for your element.
3. Electrons and Energy levels
a. electrons move in energy levels around
the nucleus
b. 1st level - 2; 2nd level - 8; 3rd level - 18
c. Valence Electrons- are found in the outer
most energy level.
Bohr Diagram show energy levels and electron
#
Bohr diagram for Chlorine
• On the back page, create your own Bohr
diagram for the element you used on your
blank slide.
Individual Practice
Individual Practice: Create your own atom.
• Using a paper plate, you will create your
own atom.
• Your teacher will give you the element that
you must use.
• Using markers you must
– Add name of element
– Add protons and neutrons
– Add the right amount of energy levels and the
correct number of electrons.
Assignment Quiz grade 3-D model
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Bohr Element
Electrons
Protons
Neutrons
Orbital's
Periodic Table
• Rows (horizontal) are called periods
– Determine the energy level (orbital)
• Columns (vertical) are called families or
groups
– Determine valance electrons (reacting
electrons)
– Elements in the same family react in a similar
fashion
ex. Both chlorine and fluorine have 7 valence e- and
have a tendency to gain 1 e-
1. Attach the periodic table to IAN
2. Label the various families
3. Label the number of valence electrons (roman numeral)
Alkaline “earth” metals
Transition Metals
Inner Transition Metals
Noble Gases
Halogens
Alkali metals
8
C. Isotopes
1. When atoms of the same element differ in
the # of neutrons they contain(still contain the
same # of electrons).
2. Radioactive isotopes-nuclei are unstable
and break down at a constant rate over time.
(geologist can determine the age of rock and
fossils by analyzing isotopes).
Marble demonstration
textbook pg.36
II. Interactions of Matter
A. Compounds and Bonding
a. compound - two or more different elements
that are chemically combined (carbon dioxide)
b. chemical compound-the substance formed by
the chemical combination of two or more
elements in definite proportions.
c. properties of a compound can be very different
from the elements that make it up
•
Covalent bonding
a. the sharing of electrons between atoms
b. the electrons actually travel in the orbital shell of
both atoms
c. the structure that results when atoms are joined
together by covalent bond is a molecule(the
molecule is also the smallest unit of
compounds).
Exercise: Tug of War 2 of the same.
• Ionic bonding
a. the transfer of electrons from one atom to
another which will create an ion, or charged
atom
b. oppositely charged ions will attract to each in a
bonding fashion
c. atoms that loss electrons become positively charged
d. atoms that gain electrons become negatively
charged
e. Weak bonds are important to biological process they
dissociate when put into solutions
Chair exercise TE
Page 38
Van der Waals Forces
a. When molecules are close together a weak attraction b/t
oppositely charged regions of nearby molecules.
Example is the gecko.
What are some everyday products that demonstrate Van Der Waals Forces?
•
Glue and cosmetics products
• How can insects and reptiles walk on water?
• Water(H20) and Its Properties
a.70% plus of living organism are made up of
water
b. Polar covalent molecule-when the charges
are unevenly distributed(this is why water is
polar).
Note: The hydrogen's
are bonded to the
oxygen.
Tug of war: one big
one small
Continued Properties of H2O
-Hydrophobic interaction- when
nonpolar molecules cluster
together in the present of
a polar substance. (example: oil in water)
-Hydrophilic interaction-substances are water
loving and will dissolve in water (examples
sugar, ionic bonds)
-Temperature stabilization - water can absorb a
large amount of heat before vaporizing. (ex.
High “specific heat - stabilizing the earth temp.
High “heat of vaporization” - sweating)
•
Hydrogen bonding
a. The attraction b/t the hydrogen atom on one water
molecule and the oxygen atom of another water
molecule.
b. cohesion - the ability of water to stick to water (ex.
Surface tension - animals walking on water and
capillary action - xylem tubes in plants)
c. adhesion- the ability of water to stick to
other materials(graduated cylinder meniscus)
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Mixtures, Solutions, and Suspensions.
a. Mixture- a material composed of two or more elements
or compounds that are physically mixed together, but
not chemically.
- Earths atmosphere is a mixture gases.
List 3 of your own examples of mixtures:
_____________, _______________, _________________
There are two types of mixtures
involving water.
• Solutions-when ions gradually become
dispersed in water.
-Solute- the substance dissolved.
-Solvent- the substance in which
the solute dissolves.
• Suspensions-materials that do
not dissolve in water, but are
separated into smaller pieces
that do not settle(blood).
Mini-Lab
100ml graduated cylinder filled with 50ml of H2O
Pour 25g of sugar into the graduated cylinder.
Gently swirl the graduated cylinder in the air.
Answer the questions below
1. What did you observe when the solution was swirled?
Are their other methods that can give you the same
result as swirling?
2. Is their any evidence that the sugar dissolved into the
water?
3. Is the level of water still at the same height as before the
sugar was added? What is the difference in height?
4. Explain what happened to the sugar when it was added
to the water?
5. What is the solute?
6. What is the solvent?
Based on previous knowledge where
can you find these everyday
substances on the ph-scale?
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Human blood
Rain
Lemons
Detergent
Wine
Baking Soda
Bleach
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Acid and bases
a. acid -a substance that releases hydrogen ions (H+)
in water. Ex: HCl acid
b. base -a substance that releases hydroxide ion
(OH-) in water. Ex: NaOH
c. pH scale- the measure of the hydrogen/hydroxide
concentration in a solution. Scale range is 1 - 14
-7 being neutral (water)
-7 below is acidic (vinegar)
-7 above is a base (ammonia)
d. Measuring ph levels
-ph paper tells an acid or base
-litmus paper tells actual ph value
e. buffer - a substance that resist changes in pH when
an acid or base is added by either accepting or
releasing hydrogen ions. Ex: blood
Balancing Chemical Equations
Writing chemical equations
-Chemical equation - a description of what happens when two or
more chemicals react
- The number atoms in the reactant chemicals must equal the
number of atoms in the product chemicals
-Subscripts are used to indicate the number of atoms of each
element in the molecule/compound
-Co-efficent are used to indicate the number of
molecules/compounds used in the reaction
Sub-script
Practice Balancing equations
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1. _____ H2 + _____ O2
_____ H2O
2. _____ N2 +_____ H2
_____ NH3
3. _____ S8 + _____ O2 _____ SO3
4. _____ N2 + _____ O2
_____ N2O
5. _____ HgO
_____ Hg + _____ O2
Organic Chemistry The study of carbon compounds
• Experiment: In 1953, Stanely set up a
Fig. 4-2
EXPERIMENT
“Atmosphere”
closed system to simulate conditions
CH4
thought to have existed on the early
Water vapor
Electrode
earth. A flask of H2O simulated the primeval
NH
3 H2
sea. The H2O was heated so that some
Condenser
vaporized and moved into a second, higher
flask containing the “atmosphere” a mixture
Cooled water
of gases. Sparks were discharged in the
Cold
containing
water
organic
synthetic atmosphere to mimic lighting
molecules
• Results: Miller identified a variety
of organic molecules that are common in
living organisms such as amino acids (a
H2O
“sea”
chain of proteins required for DNA)
Question: What conclusion did Stanley
Sample for
chemical analysis
Miller draw when he found amino acids in
That life molecules could have been
the product experiment?
synthesized from nonliving molecules
III. Life substances
A. The properties of carbon that make it so important.
1. Introduction
a. can bond with hydrogen, oxygen, phosphorous,
sulfur, and nitrogen.
b. can form single, double, or triple bonds
Ring
Chain
Branched
c. freedom of bond rotation to assume a variety of
shapes. Forms chains, ring shaped, or
branched will affect the distinctive affect of the
organic molecule.
d. can form isomers-one of two or more
compounds that differ in structure but
has the same molecular formulas
Hydrogen =
Carbons=
Hydrogen=
Carbons=
Empirical Formula:
e. contains 4 valence electrons
f. can form up to 4 covalent bonds
Check your understanding
1. Which molecules in figure 4.5 are isomers?
Butane and 2-Methylpropane and 1-Butene and 2- Butene
Fig. 4-5
Ethane
Propane
1-Butene
(a) Length
Butane
(b) Branching
2-Butene
(c) Double bonds
2-Methylpropane
(commonly called isobutane)
Cyclohexane
(d) Rings
Benzene
Functional/Chemical groups are molecular
components attached to the skeleton that will
chemically react affecting molecular functions.
Fig. 4-9
Estradiol
Testosterone
A comparison of chemical groups of female estrogen and male testosterone.
Differ only in the chemical groups attached to a common carbon skeleton
(shaded in blue). These subtle variation in molecular architecture distinguish
one major developmental difference between man and woman.
The 7 important chemical
groups in biological processes
1. Hydroxyl can clean the air we breathe of
pollutants
2. Carbonyl used making aldehydes and ketones
3. Carboxyl building amino acids
4. Amino builds protein chains
5. Sulfhydryl found in co-enzymes and certain
proteins
6. Phosphate to release or store energy
7. Methyl can be a deadly gas.
Fig. 4-10a
CHEMICAL
GROUP
Hydroxyl
Carbonyl
Carboxyl
STRUCTURE
(may be written HO—)
NAME OF
COMPOUND
In a hydroxyl group (—OH), a
hydrogen atom is bonded to an
oxygen atom, which in turn is
bonded to the carbon skeleton of
the organic molecule. (Do not
confuse this functional group
with the hydroxide ion, OH–.)
The carbonyl group ( CO)
consists of a carbon atom
joined to an oxygen atom by a
double bond.
When an oxygen atom is
double-bonded to a carbon
atom that is also bonded to
an —OH group, the entire
assembly of atoms is called
a carboxyl group (—COOH).
Alcohols (their specific names
usually end in -ol)
Ketones if the carbonyl group is
within a carbon skeleton
Carboxylic acids, or organic
acids
Aldehydes if the carbonyl group
is at the end of the carbon
skeleton
EXAMPLE
Ethanol, the alcohol present in
alcoholic beverages
Acetone, the simplest ketone
Acetic acid, which gives vinegar
its sour taste
Propanal, an aldehyde
FUNCTIONAL
PROPERTIES
Is polar as a result of the
electrons spending more time
near the electronegative
oxygen atom.
A ketone and an aldehyde may
be structural isomers with
different properties, as is the
case for acetone and propanal.
Can form hydrogen bonds with
water molecules, helping
dissolve organic compounds
such as sugars.
These two groups are also
found in sugars, giving rise to
two major groups of sugars:
aldoses (containing an
aldehyde) and ketoses
(containing a ketone).
Has acidic properties
because the covalent bond
between oxygen and hydrogen
is so polar; for example,
Acetic acid
Acetate ion
Found in cells in the ionized
form with a charge of 1– and
called a carboxylate ion (here,
specifically, the acetate ion).
Fig. 4-10b
CHEMICAL
GROUP
Amino
Sulfhydryl
Methyl
In a phosphate group, a
phosphorus atom is bonded to
four oxygen atoms; one oxygen
is bonded to the carbon skeleton;
two oxygens carry negative
charges. The phosphate group
(—OPO32–, abbreviated P ) is an
ionized form of a phosphoric acid
group (—OPO3H2; note the two
hydrogens).
A methyl group consists of a
carbon bonded to three
hydrogen atoms. The methyl
group may be attached to a
carbon or to a different atom.
(may be
written HS—)
STRUCTURE
NAME OF
COMPOUND
Phosphate
The amino group
(—NH2) consists of a
nitrogen atom bonded
to two hydrogen atoms
and to the carbon
skeleton.
The sulfhydryl group
consists of a sulfur atom
bonded to an atom of
hydrogen; resembles a
hydroxyl group in shape.
Amines
Thiols
Organic phosphates
Methylated compounds
EXAMPLE
Glycine
Because it also has a
carboxyl group, glycine
is both an amine and
a carboxylic acid;
compounds with both
groups are called
amino acids.
FUNCTIONAL
PROPERTIES
Acts as a base; can
pick up an H+ from
the surrounding
solution (water, in
living organisms).
(nonionized) (ionized)
Ionized, with a
charge of 1+, under
cellular conditions.
Glycerol phosphate
Cysteine
Cysteine is an important
sulfur-containing amino
acid.
In addition to taking part in
many important chemical
reactions in cells, glycerol
phosphate provides the
backbone for phospholipids,
the most prevalent molecules in
cell membranes.
Two sulfhydryl groups
can react, forming a
covalent bond. This
“cross-linking” helps
stabilize protein
structure.
Contributes negative charge
to the molecule of which it is
a part (2– when at the end of
a molecule; 1– when located
internally in a chain of
phosphates).
Cross-linking of
cysteines in hair
proteins maintains the
curliness or
straightness
of hair. Straight hair can
be “permanently” curled
by shaping it around
curlers, then breaking
and re-forming the
cross-linking bonds.
Has the potential to react
with water, releasing energy.
5-Methyl cytidine
5-Methyl cytidine is a
component of DNA that has
been modified by addition of
the methyl group.
Addition of a methyl group
to DNA, or to molecules
bound to DNA, affects
expression of genes.
Arrangement of methyl
groups in male and female
sex hormones affects
their shape and function.
Overview: The Molecules of Life
• All living things are made up of four classes
of large biological molecules: carbohydrates,
lipids, proteins, and nucleic acids
• Within cells, small organic molecules are
joined together to form larger molecules
• Macromolecules are large molecules
composed of thousands of covalently
connected atoms
• Molecular structure and function are
inseparable
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
2. Macromolecules
a. living organism make large
macromolecules “know as giant molecules”
b. Macromolecules are formed by a process called
polymerization-building large molecules by joining
smaller ones.
c. monomers- are the smaller unit joined
together to
form polymers.
d. Polymer-large compound formed from the
combination of many monomers
Straw exercise:
http://video.google.com/videosearch?hl=en&source=hp&q=pol
ymerization&um=1&ie=UTF-8&sa=N&tab=wv#
b. when many monomers are chemically combined
this is known as a condensation/dehydration
reaction, and water is given off as a by product
c. when a polymer is broken down into its many
monomers, this is known as a hydrolysis reaction,
and water is added. This reaction occurs in
digestion
Fig. 5-2b
Fig. 5-2a
HO
1
2
3
H
Short polymer
HO
1
2
1
2
3
4
H
Unlinked monomer
Dehydration removes a water
molecule, forming a new bond
HO
HO
H
3
Hydrolysis adds a water
molecule, breaking a bond
H2O
4
H2O
H
HO
1
2
3
Longer polymer
(a) Dehydration reaction in the synthesis of a polymer
(b) Hydrolysis of a polymer
H
HO
H
Bread Activity
B. 4 main groups of Organic Compounds
1. Carbohydrates (polymers)
a. contains carbon, hydrogen and oxygen in a
1: 2:1 ratio
b. provide energy to living cells
c. Monosaccharides - single sugars that serve
as a major fuel for cells and as raw material
for building molecules.
glucose (C6H12O6) most common=sugar
fructose=fruits
galactose=milk
D. disaccharides- linking two
monosaccharide's together
E. polysaccharide - many sugars formed by
joining monosaccharide
-Excess sugars can be stored as
1. Glycogen can release glucose from
the liver when glucose levels
become low.
2. Starch (spaghetti)
3. Plants store excess sugars as plant
starch in the chloroplast.
4. Cellulose gives plants their strength
and flexibility (wood and paper)
5. Chitin is another structural polysaccharide, is
found in the exoskeleton of arthropods
Chitin also provides structural support for the
cell walls of many fungi
Fig. 5-6
Chloroplast
Mitochondria Glycogen granules
Starch
0.5 µm
1 µm
Glycogen
Amylose
Amylopectin
(a) Starch: a plant polysaccharide
(b) Glycogen: an animal polysaccharide
Fig. 5-10
(a) The structure
of the chitin
monomer.
(b) Chitin forms the
exoskeleton of
arthropods.
(c) Chitin is used to make
a strong and flexible
surgical thread.
CARBOHYDRATES Check your
Understanding
-Milk contains carbohydrates lactose and galactose.
-Fruits contain carbohydrates fructose
-Potatoes contain carbohydrates starch
1. What is the source of energy for these carbohydrates?
They get energy from sunlight
2. What function do these carbohydrates serve in living
things? They provide living organisms with energy
2. Lipids
a. contains carbon, hydrogen, and oxygen in
different ratios than carbohydrates.
-The components lipids consist of are a
glycerol and fatty acid
Fatty Acid Chain
Glycerol
b. used for stored energy, insulation, protective
coatings, cell membranes and as hormones
c. all are insoluble in water (hydrophobic)
d. steroids are also lipids
e. mainly seen as fats, oils, and waxes.
• Can be saturated where all the carbons have a
hydrogen attached at every possible spot. No double
bonds (usually solid at room temp)
• Can be unsaturated carbons are double bonded
resulting in a kink in the carbon chain (usually liquid a
room temperature)
• Polyunsaturated when fatty acids have more than
one double bond (peanut oil)
Fig. 5-12
Structural
formula of a
saturated fat
molecule
Stearic acid, a
saturated fatty
acid
(a) Saturated fat
Structural formula
of an unsaturated
fat molecule
Oleic acid, an
unsaturated
fatty acid
(b) Unsaturated fat
cis double
bond causes
bending
LIPIDS Check your Understanding
1.
What are the components of a lipid?
Carbon, hydrogen, oxygen in diiferent ratios than carbohydrates
2.
Would you describe the picture shown to be a saturated or an
unsaturated fat?
Unsaturated usually
liquid at room
temperature
3.
4.
Is saturated or unsaturated more healthy? Unsaturated
Which of these substance stores the most energy?
A. One gram of fat
B. One gram of alcohol
C. One gram of carobohydrate
D. One gram of nucliec acid
Bell Ringer
• What are some negative effects of
carbohydrates in the body?
The break down of sugar molecules (diabetics)
• What are some negative effects of lipids
in the body?
To much fat high cholesterol not being able to breaks down the fat, loss
Of H2O
3. Proteins
a. contain carbon, hydrogen, oxygen, nitrogen, and
sulfur
b. used for cell structure, as enzymes, hemoglobin, and
the immune system
c. monomer unit is the amino acid. 20 common
variations
d. all amino acid are identical in amino group and
carboxyl groups.
e. They differ in the R-group
-can be acidic or basic
-can be polar or nonpolar
Table 5-1
• Enzymes are a type of protein that acts as a
catalyst to speed up chemical reactions
• Enzymes can perform their functions
repeatedly, functioning as workhorses that
carry out the processes of life
Animation: Enzymes
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
e. amino acids are bonded together by peptide bonds to
form polypeptides
f. structural levels
1. Primary - order of amino acids
2. Secondary - coiling or sheet design
3. Tertiary - over all three-dimensional shape due
to “R” groups of the amino acids
4. Quaternary - the arrangement assumed by two
or more polypeptides bonding together
Fig. 5-21
Sickle-Cell Disease: A Change in
Primary Structure
Primary
Structure
Secondary
Structure
Tertiary
Structure
Quaternary
Structure
pleated sheet
+H N
3
Amino end
Examples of
amino acid
subunits
helix
•A slight change in primary structure can affect a protein’s structure and
ability to function
•Sickle-cell disease, an inherited blood disorder, results from a single amino
acid substitution in the protein hemoglobin
Fig. 5-22c
10 µm
Normal red blood
cells are full of
individual
hemoglobin
molecules, each
carrying oxygen.
10 µm
Fibers of abnormal
hemoglobin deform
red blood cell into
sickle shape.
What Determines Protein Structure?
• In addition to primary structure, physical and
chemical conditions can affect structure
• Alterations in pH, salt concentration,
temperature, or other environmental factors
can cause a protein to unravel
• This loss of a protein’s native structure is
called denaturation
• A denatured protein is biologically inactive
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 5-23
Denaturation
Normal protein
Renaturation
Denatured protein
PROTIENS
Check you Understanding
• Which part of the amino acid is the same
in every amino acid?
Amino group and carboxl group
• In what way are R-groups different?
Acidic or basic
Polar or non-polar
• Explain why proteins are considered
polymers but not lipids?
Proteins are made up of many monomers that become polymers. Lipids
are made of gycerol and 3 fatty acid chains
Nucleic acids store and transmit
hereditary information
• The amino acid sequence of a polypeptide
is programmed by a unit of inheritance
called a gene
• Genes are made of DNA, a nucleic acid
• There are two types of nucleic acids:
– Deoxyribonucleic acid (DNA)
– Ribonucleic acid (RNA)
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
4. Nucleic acids
a. contains carbon, hydrogen, oxygen, and nitrogen
b. used for encoding cellular information and as carrier
molecules
c. monomer unit: nucleotide
d. nucleotide subunits:
- 5 carbon sugar (ribose or deoxyibose)
-phosphate group
-1 nitrogen base (adenine, guanine, cytosine,
thymine, or uracil)
-The order of nitrogenous
bases affect the information
contained (alphabet).
e. two nucleic acid polymers
1. DNA - record the cellular
instructions
2. RNA - reads and then carries out
the instructions
f. other nucleotides and
their functions are:
ATP - energy for the cell
NAD - hydrogen carrier for
chemical reactions
NUCLEIC ACIDS Check you
Understanding
1. What are the three basic parts of a
nucleotide? 5 carbon sugar, phosphate group, and a
nitrogenous base.
2. Does the sequence of nitrogenous
bases effect the information it contains
and how? Yes
ABCDEFGHIJKLMNOPQRSTUVWXYZ
Fig. 5-UN2a
Fig. 5-UN2b
Matter and Energy
• Have you ever sat around a campfire or watched flames flicker in a
fireplace? The burning of wood is a chemical reaction—a process that
changes one set of chemicals into another set of chemicals. A chemical
reaction always involves changes in chemical bonds that join atoms in
compounds. The elements or compounds that enter into a chemical
reaction are called reactants. The elements or compounds produced by
a chemical reaction are called products. As wood burns, molecules of
cellulose are broken down and combine with oxygen to form carbon
dioxide and water vapor, and energy is released.
Reactants are oxygen
1. What are the reactants when wood burns?
and cellulose.
2. What are the products when wood burns?
Products are carbon dioxide
3. What kinds of energy are given off when wood burns?
and water.
Light and heat are given off. Some students may also mention sound
(the crackling
a fire).
4. Wood doesn’t
burn allofby
itself. What must you do to start a fire? What
does this mean in terms of energy?
To start a fire, you must light it with a match and kindling.
You are giving the wood some energy in the form of heat.
5. Once the fire gets started, it keeps burning. Why don’t you need to keep
restarting the fire?
Once the fire gets going, it gives off
Chemical Reactions
Chemical Reactions
• A process that changes one set of chemicals into
another set of chemicals.
-some reactions happen
slowly like rust
Iron + Water + Oxygen => Rust
Reactants
Product
-Reactant is the breaking of bonds
-Products is the formation of new bonds
-some happen
quickly like
hydrogen gas
igniting.
Balancing Chemical Equations
Writing chemical equations
-Chemical equation - a description of what happens when two
or more chemicals react
- The number atoms in the reactant chemicals must equal the
number of atoms in the product chemicals
-Subscripts are used to indicate the number of atoms of each
element in the molecule/compound
-Co-efficient are used to indicate the number of
molecules/compounds used in the reaction
Sub-script
Practice Balancing equations
•
•
•
•
•
1. _____ H2 + _____ O2
_____ H2O
2. _____ N2 +_____ H2
_____ NH3
3. _____ S8 + _____ O2 _____ SO3
4. _____ N2 + _____ O2
_____ N2O
5. _____ HgO
_____ Hg + _____ O2
Energy In Reactions
Energy-Absorbing Rxn.
Energy-Releasing Rxn.
Activation
Energy
Products
Reactants
Activation Energy
Reactants
Energy-Releasing
Products
Products
Reaction
• Exergonic are chemical reaction that release
energy occur spontaneously (without
prompting)
• Endergonic are chemical reaction that
absorb energy will not occur without a
source of energy.
Energy-Absorbing Rxn.
Product
Reactants
Energy-Releasing Rxn
Reactants Activation
Energy
Activation Energy
Products
• Check Your Understanding:
• How would you compare the energy of
the products and reactants in the two
types of reaction graphs?
Energy absorbing the products have more energy than the reactants. In a
Energy releasing the products have less energy than the reactants.
• Which type of graph reaction is more
likely to be spontaneous Energy releasing reaction
Activation Energy and Enzymes
• Activation Energy is the energy needed to
get a reaction started.
• Catalyst is a substance that speeds up the
rate of a chemical reaction.
• Enzymes are proteins that speed up
chemical reactions that happen in cells.
Textbook Demonstration
Push a book off the desk. Observe how
much energy it took to push the book off
the desk.
Now prop the book at an angle and push the
book off the desk. Did it take the same
amount of energy?
What represented the activation energy and
the enzyme/catalyst
1.Identify the axes in the graph below?
2. What does the graph show would be the effect if enzymes were not
available within the cell?
3.Would a reaction take a longer or shorter time with an enzyme?
4. What would be an appropriate title for this graph?
Reaction
pathway
without enzyme
Activation
energy
without
enzyme
Reactants
Reaction
pathway
with enzyme
Products Activation
energy
with
enzyme
Substrates Specificity of
Enzymes
-Enzymes provide a site where a reactant can be brought
together to react.
-Substrates-reactant of a enzyme catalyst reaction.
-Substrates bind to a site on the enzyme called the active
site (lock and key).
-Enzyme-substrate complex when a enzyme binds to a
substrate because there are two or more reactants
present.
-Activation site only a restricted region of the enzyme
molecule actually binds to the substrate.
-Induced fit enhances their ability to catalyze the chemical
reactions.
1. Substrates enter active site; enzyme
changes shape such that its active site
enfolds the substrates (induced fit).
2.
Substrates held in
active site by weak
interactions, such as
hydrogen bonds and
ionic bonds.
Enzyme-substrate
complex
Active
site is
available
for two new
substrate
molecules
Enzyme
3. Active site can lower
EA and speed up a
reaction
5. Products are
released
4. Substrates are
converted to
products.
The substrate fits
into the active site
of the enzyme
creating a induced
fit(similar to the
clasp of a
handshake).
What effects enzyme activity?
• Changes in Temperature
• Ph Values
• Optimal ph is
determined by
finding the highest
point and dragging
straight down to the
x-axis
• What is the optimal
ph for pepsin? 2
Fig. 8-18
Rate of reaction
Optimal temperature for
typical human enzyme
Optimal temperature for
enzyme of thermophilic
(heat-tolerant)
bacteria
40
60
80
Temperature (ºC)
(a) Optimal temperature for two enzymes
0
20
Optimal pH for pepsin
(stomach enzyme)
100
Optimal pH
for trypsin
Rate of reaction
(intestinal
enzyme)
4
5
pH
(b) Optimal pH for two enzymes
0
1
2
3
6
7
8
9
10
What effects enzyme activity?
• Co-factors non-protein helpers for catalytic activity
• Co-enzymes are organic co-factors seen mostly in
vitamins
• Competitive inhibitors reduce enzyme productivity by
blocking substrates from entering active sites
• Noncompetitive inhibitors they impede enzymatic
reactions by binding to another part of the enzyme
Fig. 8-19
Substrate
Active site
Competitive
inhibitor
Enzyme
Noncompetitive inhibitor
(a) Normal binding
(b) Competitive inhibition
(c) Noncompetitive inhibition