Unit 2
The Chemistry of Life
Learning Targets
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Describe the bonding properties of carbon atoms
Compare and understand the importance of the four macromolecules:
carbohydrates, lipids, proteins, and nucleic acids.
Describe how bonds break and reform during chemical reactions
Explain why and how chemical reactions release or absorb energy.
Explain the effect of catalysts on activation energy.
Describe and explain how enzymes regulate chemical reactions.
Carbon Based
Molecules
Carbons unique bonding
properties
 Building blocks of life because they are the
basis of most molecules that make up living
things.
 Organisms obtain energy (food) and turn it
into ATP (cells power source for all life
processes).
 Unique atomic structure because it has four
unpaired electrons on the outer energy level
and can form covalent bonds with up to four
other atoms!!!!!!
Three types of molecular
structures
 Straight Chain
 Branched Chain
 Ring
Monomer / Polymer
Polymer= molecule that contains many
Monomers bonded together.
Monomer=
small
molecular
subunit
How many monomers are above?
Four Carbon Based
Molecules in Living Things
/ Macromolecules
1. Carbohydrates
2. Lipids
3. Proteins
4. Nucleic Acids
Carbohydrates
 Fruits, grains, sugars, starches
 Monosaccharides, Disaccharides,
Polysaccharides
 Made up of carbon, hydrogen, and oxygen,
generally in a 1:2:1 ratio
 When broken down they provide a source of
usable chemical energy for cells
 Major part of plant cell structure too!!!
Monosaccharides
 Monomers
 Simple sugars -> glucose= C6H12O6
Disaccharides
 Two monosaccharides linked together
 Transport = organisms use it to move
glucose from place to place
 Ex- Sucrose= common table sugar (made
from glucose and fructose)
 Ex- Lactose= milk sugar (made from
glucose and galactose)
Polysaccharides
 Many monosaccharides linked together
to form long branches or chains.
 Polymers
 Ex- starch and glycogen -> energy
storage in plants and animals
 Ex- Cellulose- cell walls in plants
Lipids
 Nonpolar molecules that are insoluble in water
(they don’t dissolve)
 Examples such as fats, oils (coconut, olive, corn),
waxes, cholesterol, steroids, fatty acids, glycerol,
 Function- Some are broken down for cell use, some
are stored for later energy use, and others are parts
of cell structures.
 Monomer- glycerol and fatty acids (no true
monomer)
 Polymer- lipids
3 Main Lipids
 1. Fats or Triglycerides= energy storage
molecules
Three fatty acids bonded to glycerol
2a. Saturated fatty acids= held
together by a single covalent bond
and is solid at room temperature.
Has the maximum number of hydrogen
atoms possible
2b. Unsaturated fatty acids= one or
more double bonds between the
carbon atoms.
Not saturated with hydrogen atoms
2c. Polyunsaturated- two
or more double covalent
bonds
Good fatty acids
3. Phospholipids
 Form the bilayer of the cell membrane
 One glycerol, two fatty acids, and a
phosphate
 Hydrophobic tails- afraid of water (nonpolar)
 Hydrophilic heads- love water (polar)
Proteins
 Most varied- a part of everything from moving your
leg to digesting your pizza.
 Protein is the polymer made up of monomers called
amino acids.
 Amino acids are referred to as the “building blocks”
of proteins and are thought to be the first
molecules on Earth.
 We use 20 different amino acids to build proteins in our
bodies.
 Your body makes 12 and the others need to be ingested
through meat, beans, and nuts.
Amino Acids
 All have similar structures:
hydrogen atom, an amino
group (NH2), and a carboxyl
group (COOH).
 NH2 and COOH are always
present.
 The R group (side group) is
different for each group
 Central carbon is covalently
bonded to four atoms
(functional group) with one
always being a hydrogen.
Proteins Cont.
 Held together by covalent bonds called peptide bonds.
The bonds form between the amino group of one amino
acid and the carboxyl group of another amino acid.
Peptide bond
•Polypeptide forms between two amino acids
•They are a single chain of three or more amino acids linked
together by peptide bonds.
Functions of Proteins
 1. Catalyzing enzymes- speed up
the rates of reactions
Activate metabolic reactions
Lowers activation energy-> the amount of
energy to get a reaction started
On-going
Needs certain factors-> pH, temperature,
and concentration
Ex- Human enzymes work best at 98.6,
above 104 they fall apart.
 2. Defensive proteins- basis of the bodies
endocrine and immune systems. They attack
invading microbes and cancer cells.
Ex- antibodies attack viruses and bacteria
Ex- fibrinogen = protein that causes your blood
to clot
 3. Storage proteins / Nutrient - bind
with iron and calcium to provide
nourishment for an organism.
 4. Transport proteins- allows larger
molecules to move in and out of cells.
Ex- Hemoglobin= carries oxygen
Ex- Myoglobin= carries oxygen to muscles
 5. Support Proteins- provide structural support
and protection.
Ex- Keratin in your hair, skin, and nails
Ex- Fibrin- allows your blood to clot
Ex- Collagen and elastin- major components of
connective tissue
6. Motion Proteins such as myosin and actin
cause muscles to contract or change shape.
7. Messenger proteins- allow different cells to
communicate.
Ex- Hormones- regulate body functions
Ex- Insulin- regulates glucose levels
Ex- Vasopressin- tells your kidneys to reabsorb
water
Nucleic Acids
 Detailed instructions that build proteins and are stored in
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extremely long carbon based molecules.
Nucleic acid = polymer
Nucleotides = monomer
Nucleotides are made up of: sugar, phosphate group, and a
nitrogen base (Adenine, thymine, guanine, and cytosine.
Nitrogen bases always pair up in the same way!
 For DNA: A – T, C – G
 For RNA: A – U, C – G (thymine in RNA is replaced with uracil)
 Two types= DNA and RNA
 ONE FUNCTION!!!!!-> DNA and RNA work together to
make proteins. DNA passes on genetic instructions to RNA.
RNA decodes and turns the genetic information into a
protein.
DNA – Double Helix
The sides of the ladder are made of alternating sugar and
phosphate molecules. The sugar is a pentose called
deoxyribose. The deoxyribose and phosphate molecules are
held together by covalent bonds. Label the covalent bonds.
Label the thymines.
Label the adenines.
Label the guanines.
Label the cytosines.
In DNA, What nitrogenous base does adenine always pair
thymine
with? ___________________
In DNA, What nitrogenous base does guanine always pair
cytosine
with? ____________________
T and ______
A - ______
So… _____
C - _______
G
The two sides of the DNA ladder are held together loosely by
hydrogen bonds (small circles). Label the hydrogen
bonds.
In RNA, the pairing of nitrogenous bases is a little different.
Guanine still pairs with cytosine. But thymine is replaced by
uracil.
So… _____
A - ______
U and ______
C - _______
G
 DNA is the basis of genes and heredity.
Chemical Reactions
 When substances are changed into
different substances by breaking and
forming chemical bonds.
Reactants vs. Products
Reactants
Label
Them!!!!
Products
What causes bonds in oxygen
and glucose molecules to
break?
 Energy is added that causes the bonds
to break into oxygen and glucose.
 Each bond requires a different amount
of energy= Bond Energy
What happens when new
bonds form in carbon dioxide
and water?
 When new bonds form, energy is
released and this energy that is
released is equal to the amount of
energy that breaks the same bond.
 Sometimes bonds can form a chemical
equilibrium, meaning they are reversible
and the same on both sides of the
equation.
Example of Equilibrium
 Blood cells and plasma
transport materials
throughout the body.
 Carbonic acid (H2CO3)
dissolves in the blood
(leaving a bicarbonate,
HCO3)
 That bicarbonate is later
converted back into carbon
dioxide in the lungs and is
able to be expelled.
Chemical reactions release or
absorb energy
 Energy added = breaks chemical bonds
 Energy released= new bonds form
 Energy is released or absorbed and in
different amounts.
Activation energy
Amount of energy that needs to
be absorbed for a chemical
reaction to start.
Ex.- the energy you would need
to push a rock up a hill.
Exothermic
Releases more energy than it absorbs
Excess energy is typically given off in
heat or light
Reactants have more energy than
products
Ex- firefly squid, fireflies, cellular
respiration (releases usable energy as
well as keep your body warm).
Endothermic
Absorbs more energy than it
releases
Products have more energy than
reactants
Example- photosynthesis-> plants
absorb energy from the sun and
use that energy to make simple
and complex carbs.
Enzymes
How did the Venus Flytrap
digest the frog?
Enzymes-> type of protein
that helps start and run
chemical reactions in living
things.
Break down food into smaller
molecules that the body can
use.
What is activation energy?
The energy needed to get
things started
 Most of the time the activation energy for a
chemical reaction comes from an increase in
temperature-> sometimes the process is
very slow.
 In order to speed the process up substances
called catalysts decrease the activation
energy needed to start the chemical reaction
-> in the end it increases the chemical
reaction.
 When a catalyst (ex- enzymes) is present
less energy is needed and products form a
lot faster.
What are two functions of
catalysts in chemical reactions?
1. Decrease activation
energy
2. Increase reaction time.
Enzymes
 Definition= catalysts for chemical reactions in living
things (made by proteins)
 Reactants are usually found at very low
concentrations in the body, but really need to occur
quickly.
 Almost all are proteins= long chains of amino acids
 Each one depends on its structure to function
 Temperature, concentration, and pH can affect the
shape, function, rate, and activity of the enzyme.
 Work best at normal body temperature
 If temperature is a little elevated then the
hydrogen bonds will fall apart, the
enzymes structure will change, and its
ability to function will be lost.
 This is the reason why a high
temperature / fever is very dangerous to
a person.
Examples of enzymes in action
 Amylase is an enzyme in saliva that breaks
down starches into simpler sugars. Without
amylase it would take a million times slower
for you to chew, swallow, and digest your
food.
 Blood cell engulfing a pathogen
CHEMICAL ACTED
UPON
PRODUCTS
Lipase
Fats & oils
Glycerol & fatty
acids
Amylase
Starch
Maltose
Maltase
Maltose
Glucose
Pepsin
Protein
Polypeptides
Protease
Polypeptides
Amino acids
Catalase
Hydrogen
peroxide
Water and oxygen
ENZYME
 The structure is so important because each
enzyme’s shape is specific to a certain
reactant= allows them to fit perfectly
together just like a key fits into a lock
 Specific reactant an enzyme acts on are
called substrates
 The sites where substrates bind to enzymes
are called active sites.
 Enzymes bring substrate molecules close
together, then they decrease activation
energy, substrates attach together and their
bonds are weakened, and then the catalyzed
reaction forms a product that is released
from the enzyme.
Videos
 http://highered.mcgraw-
hill.com/sites/0072495855/student_vie
w0/chapter2/animation__how_enzymes
_work.html
 http://www.youtube.com/watch?v=Nd
MVRL4oaUo
Reflection
 On a sheet of paper, review the three
parts of the lock and key model and write
a paragraph (3-5 sentences) describing
the analogy. Consider why the model is
described as a lock and key. Also identify
the different parts and what happens to
each part after the reaction is complete.
You may use your notes