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Unit 2
Chemical Basis for Life
Chapter 6
Chemistry in Biology
Section
Section
Section
Section
1:
2:
3:
4:
Atoms, Elements, & Compounds (p. 148-155)
Chemical Reactions (p. 156-160)
Water & Solutions (p. 161-165)
The Building Blocks of Life (p. 166-171)
Section 1
Atoms, Elements, and Compounds
Objectives

Living things consist of atoms of different elements

Ions form when atoms gain or lose electrons

Atoms share pairs of electrons in covalent bonds
The atom

The atom is the smallest basic unit of matter

Atoms are very small
The atom

There are three parts of a an atom
Subatomic
particle
Charge
Location
Proton
Positive
Nucleus
Neutron
Neutral
Nucleus
Electron
Negative
Surrounding
nucleus
Elements

An element is one particular type of atom, and it cannot be broken down into
a simpler substance by ordinary chemical means

Gold

Aluminum

Helium

Atoms & Elements
Key Elements

In biology, there are SIX very important elements

Carbon

Hydrogen

Oxygen

Phosphorus

Sulfur

Nitrogen
How are elements different


The number of protons determines the identity of an element

Carbon: 6 protons

Oxygen: 8 protons
The number of electrons determines the property of an element

Carbon: 6 electrons, 4 on OUTSIDE

Oxygen: 8 electrons, 6 on OUTSIDE
Carbon diagrams
Chemical Party
https://www.youtube.com/watch?v=wBCmt_pJTRA
Lonely Atoms

Atoms rarely are found alone in nature

They will do ANYTHING to get to 8 electrons on the outside

Steal

Dump

Share
Compounds

A compound is a substance made of atoms of different elements bonded
together

Result of sharing, stealing, or dumping electrons

Atoms bonded in a specific ratio
Carbon Compounds (more about this
later)

Carbon can form many various bonds to form

Carbohydrates

Proteins

Nucleic acids

Lipids
Ionic Bond

Ionic bonds are formed through the electrical force between oppositely
charged ions


Opposites attract!
Ex: Salt aka sodium chloride (NaCl)

Positive sodium (Na+)

Negative chloride (Cl-)
NaCl – ionic bond
Ions

Ions are atoms that have gained or lost one or more electrons.

Results in a change in electrical charge

Gain e-
becomes negative

Lose e-
becomes positive
Ions, cont.

Very important to organisms

Hydrogen ions (H+) needed to produce chemical energy in cells

Calcium ions (Ca2+) needed for all muscle movement in your body

Chloride ions (Cl-) needed for many chemical signals in the brain
Covalent Bond

Not all atoms easily gain or lose their electrons!

Some atoms share their electrons instead!

Covalent Bond: forms when atoms share a pair of electrons

Usually a very strong bond

Atoms may have several covalent bonds to share several electrons
H2O – covalent bond
CO2 – covalent bond
Covalent Bond, cont.

Molecule: two or more atoms held together by covalent bonds

Ex: carbon dioxide (CO2)

Carbon atoms needs 4 electrons to fill outer level, oxygen needs two

Carbon shares with 2 oxygen!

Ions, Ionic Bonds, & Covalent Bonds
Review

What are atoms?

How are the particles that make up atoms diagrammed?

What are the similarities between covalent and ionic bonds?
Section 2
Chemical Reactions
Objectives

Bonds break and form during chemical reactions.

Chemical reactions release or absorb energy.
Evidence of a chemical reaction
Temperature change
Formation of a solid (precipitate)
Color change (sometimes)
Odor (sometimes)
Formation of gas
Chemical Reaction... Gummy bear torture
 Bonds
break & form during chemical
reactions


Plant/Animal cells break down sugars to get
usable energy
Cells build protein molecules by bonding amino
acids together
 Chemical
reactions change substances into
different substances by breaking and forming
chemical bonds
 Reactants
are the substance changed during
a chemical reactions

Oxygen (O2) & Glucose (C6H12O6)
 Products
are the substances made by a
chemical reaction

Carbon Dioxide (CO2) & Water (H2O)
6O2 + C6H12O6
6CO2 + 6H2O
Reactants & Products
 Energy


Bond energy is the amount of energy that will
break a bond between two atoms.
Every atom has different bond energy


A SPECIFIC amount of energy is needed to break bonds
in an oxygen molecule
A SPECIFIC amount of energy is needed to break bonds
in a glucose molecule
 Energy

is needed to break bonds in molecules
is released when bonds are formed
The amount of energy released is equal to the
energy that breaks the same bond

Energy needed to break apart water molecule = energy
released when hydrogen & oxygen atoms bond to form
a water molecule
 All


chemical reactions involve changes in energy
Energy added to the reactants breaks their chemical
bonds
When new bonds form in the products, energy is
released
 Energy
is both absorbed and released during a
chemical reaction!


Some release more energy than they absorb (Generous)
Some absorb more energy than they release (Greedy)
 Generous
chemical RXNs that release more
energy than they absorb



= Exothermic reaction
Excess energy is the difference in bond energy
between the reactants and products
Excess energy is often released as heat or light

Cellular respiration releases usable energy for your
cells & heat!
 Greedy
chemical RXNs that absorb more energy
than they release

= Endothermic reaction

In photosynthesis, plants absorb energy from sunlight and
use that to make sugars and carbohydrates
Exothermic VS. Endothermic graphs
But how does a rxn start?

Some energy must first be absorbed by the reactants in ANY chemical reaction


The amount of energy needed will vary
Activation energy is the amount of energy that needs to be absorbed for a
chemical reaction to start

Push a rock up a hill
Activation energy

Activation Energy
Catalysts & Enzymes

A catalyst is a substance that lowers the activation energy needed to start a
chemical reaction.

Special proteins called enzymes are the biological catalysts that speed up the
rate of chemical reactions in biological processes.
Enzymes

https://www.youtube.com/watch?v=XTUm-75-PL4
Review

What are the parts of a chemical reaction?

How can energy changes be related to chemical reactions?

What is the importance of enzymes in living organisms?
Section 3
Water and Solutions
Objectives

Life depends on hydrogen bonds in water.

Many compounds dissolve in water.

Some compounds form acids or bases.
CELLS
•Organisms’ bodies, (their _____________),
WATER
are made up of mostly ____________________
STRUCTURE
•The water in cells gives the cell _______________
TRANSPORTS
and ___________________
materials within
organisms.
•All of the processes necessary for an
organism’s life take place within the
WATERY ENVIRONMENT of the cell
______________________________
______________________
1. HIGH
SPECIFIC HEAT
______________________
2. COHESION
______________________
3. ADHESION
Hydrogen Bonding
Negative Charge
POLAR
•Water is a “______________”
molecule
•Form when atoms in a molecule
UNEQUAL pulls on the
have ____________
ELECTRONS
_____________ they share.
Positive Charge
•Opposite charges of polar molecules can
HYDROGEN
interact to form ____________________
bonds.
•An attraction between a slightly
POSITIVE
_______________
hydrogen atom
and a slightly ______________
NEGATIVE
atom.
(Usually
_______________________________)
OXYGEN OR NITROGEN
•Hydrogen bonds are part of the
PROTEINS
structures of _______________
and
of ______________
DNA
Positive Charge
Shared Electrons
Cohesion: the attraction among
__________________
of the same
MOLECULES
substance.
Cohesion from hydrogen bonds makes
water molecules _____________________.
STICK TOGETHER
Cohesion produces __________________,
SURFACE TENSION
( “skin on water” )
Adhesion: the attraction among
__________________
MOLECULES of ______________
DIFFERENT
substances.
For example, water molecules stick to other
things.
Water in a test tube, (water is attracted
to the ____________)
GLASS
Materials such as
SUGARS
________________
and
____________
cannot be
OXYGEN
transported form one part
of an organism to another
unless they are dissolved
in blood, plant sap, or
other water based fluids.
SOLUTION
______________:
Mixture of a substance
that is the same
throughout.
SOLVENT
___________:
Substance that is present
in the greater amount and
dissolves another
substance.
SOLUTE
___________:
Substance that dissolves
in a solvent.
Mixtures
Heterogeneous

A mixture with easily separated
parts with their distinct properties
Homogeneous

A mixture that it the SAME
throughout and hard to tell
individual characteristics
ACIDS
BASES
Some compounds form ______________
or _____________
BREAK UP
IONS
because they _______________
into _______________
WATER
when they dissolve in ___________.
BASE:
ACID:
Compounds
that release
a proton
- a hydrogen ion(H+) –
when it dissolves
in water
Compounds that
remove H+ ions
from
a solution
More basic
More acidic
neutral
pH Scale examples
Review

How does the structure of water make it a good solvent?

What are the similarities and differences between solutions and suspensions?

What are the differences between acids and bases?
Section 4
The Building Blocks of Life
Objectives

Carbon atoms have unique bonding properties.

Four main types of carbon-based molecules are found in living things.
PROTEIN
____________________
LIPIDS
____________________
CARBOHYDRATES
____________________
ATP
____________________
NUCLEIC ACID
____________________
 Carbohydrates
are molecules composed of
carbon, hydrogen, and oxygen



Include sugars & starches
Can be broken down to provide useable energy
for cells
Major part of plant cell structure
 The
most basic carbs are simple sugars,
monosaccharides
 Polysaccharides
are polymers of
monosaccharides
•USED BY CELLS FOR __________
ENERGY ___________
SOURCE
AND
__________
ENERGY____________.
STORAGE
SIMPLE CARBS = _______________________________
ONE OR TWO SUGAR MOLECULES
COMPLEX CARBS =LONG
_____________________________
CHAINS OF SUGAR
MOLECULES
_____________________________
Ex) Starches such as potato,
________________________________
pasta, bread
________________________________
 Proteins

A
are the most varied of the carbon-based molecules in organisms
Have a role in movement, eyesight, digestion, etc.
protein is a polymer made of monomers called amino acids
 Amino
acids are molecules that contain carbon, hydrogen, oxygen,
nitrogen, and sometimes sulfur


Organisms use 20 different amino acids to build proteins
The body makes 12 of the 20, the other 8 come from food
CELLS
•MAKE UP _________________.
LIFE PROCESSES
•INVOLVED IN ALL _______ ____________.
ACIDS
•BUILDING BLOCKS = _________AMINO
__________.
ENZYME
•_________________=
TYPE OF PROTEIN THAT STARTS AND
SPEEDS UP CHEMICAL REACTIONS IN CELLS.
 Lipids
are nonpolar molecules that include
fats, oils, and cholesterol



Contain chains of carbon bonded to oxygen &
hydrogen
Some broken down for useable energy
Others are part of a cell’s structure
 Fatty
acids are chains of carbon atoms
bonded to hydrogen atoms.


Saturated fatty acids have single carbon-carbon
bonds
Unsaturated fatty acids have double carboncarbon bonds
WATER
•DON’T MIX WITH ______________.
CELL MEMBRANE
•PHOSPHOLIPIDS – MAKE UP ________
______________.
STORE___________.
ENERGY
•FATS AND OILS THAT _________
•ORGANISMS USE FATS AND OILS WHEN THEY HAVE
CARBOHYDRATES
USED UP ___________________.
FATS
•_________SOLID AT ROOM TEMPERATURE.
OILS
•_________LIQUID AT ROOM TEMPERATURE.
ENERGY CARRYING
•MAJOR ___________
___________ MOLECULE IN CELL.
CARBOHYDRATES AND __________
LIPIDS
•ENERGY IN __________________
AND
PROTEINS
_____________________
MUST BE TRANSFERRED TO
ATP IN CELL TO BE USED.
 Detailed
instructions to build proteins are
stored in extremely long carbon-based
molecules called nucleic acids

Nucleic acids are polymers that are made up of
monomers called nucleotides
 Nucleic
acids differ from the other carbonbased molecules


The others have a large # of functions
Nucleic acids have just 1 function… make
proteins


DNA stores info for putting amino acids together to
make proteins
RNA helps to build proteins
PROTEIN
•HAVE ALL INFO NEEDED TO MAKE __________.
BLUE PRINT
•“_______________”
OF LIFE.
•BUILDING BLOCKS OF NUCLEOTIDES
_____________.
DNA
RNA
•TWO TYPES: ________
AND _______.
 Each
subunit of a complete carbonbased molecule is called a monomer
A
polymer is a large molecule, or
macromolecule, made of many
monomers bonded together


Monomers of a polymer may be the
same (ex. Starches)
Or different (proteins)
COMPOUND
BUILDING BLOCK
(POLYMER)
(MONOMER)
PROTEIN
AMINO ACID
LIPID (FAT)
FATTY ACID
CARBOHYDRATE
SUGARS
NUCLEIC ACIDS
NUCLEOTIDE
Review

What is the role of carbon in living organisms?

What are the four major families of biological macromolecules?

What are the functions of each group of biological macromolecules?