Download Chapters 4 and 5 Mrs. Svencer CP Biology 4.1 Life Requires About

Chapters 4 and 5
Mrs. Svencer
CP Biology
4.1 Life Requires About 25
Chemical Elements

Matter
–

Element
–
–

pure substance - can’t be broken down by chemical reactions.
Ex: Gold, mercury, oxygen.
C, H, O, N – make 96% of living matter
Trace Elements
–
–

anything that occupies space and mass – “stuff” of the
universe (ex: desk, pencil, you…)
< .01% of body mass
critical for life
Compound
–
–
2+ elements chemically combined in a fixed ratio
Ex: water- H2O, sodium chloride - NaCl
Figure 4-1
This chart compares
percentages of various
elements in your body. All of
the elements represented are
essential to life.
4.2 Chemical Properties are based
on the structure of atoms
Atom vs. Element
Atom:
-no observable traits (like Element)
-no melting or boiling points, density, color
An atom has an atomic number.
Atoms




“atomos” – “indivisible”
Smallest possible particle of an element
Ex: oxygen atom, gold atom
Made of subatomic particles
–
–
–
Proton: positive electrical charge (+)
Electron: negative electrical charge (-). e-, least
mass
Neutron: electrically neutral – no charge
Figure 4-4
This model of a
helium atom
indicates the number
of each kind of
subatomic particle it
contains. Though no
visual model can
accurately show an
atom's structure,
models can help you
in understanding
certain aspects of an
element's chemical
behavior.
An element’s physical and chemical
properties depend on the number and
arrangement of subatomic particles.

Nucleus: core of an atom
–
–
protons and neutrons
e- found in cloud around nucleus


–
travel at great speeds
attracted to (+)
Number of protons = atomic number
Isotopes

Same # of protons, different # of neutrons
–
12C has 6 neutrons, 13C has 7 neutrons

–
6+6
6+7
Radioactive isotopes – nucleus decays, gives off
radiation

Useful as “biological spies” in organisms
Figure 4-5
Atoms of three isotopes of carbon differ only
in their numbers of neutrons. The isotopes are
named for the total number of particles in
their nuclei (protons plus neutrons). Carbon13, for example, has 6 protons and 7 neutrons,
for a total of 13.
Electrons and Reactivity


e- belong to different energy levels
e- fill the 1st levels 1st
–
–
–
1st level = 2 e2nd level = 8 ePartially filled levels make atoms more reactive;
they want to fill their highest occupied energy levels
Figure 4-7
An atom's lowest (first) energy level can hold
up to 2 electrons. The second level can hold
up to 8. Notice that the second energy levels
of carbon, nitrogen, and oxygen atoms are
unfilled with 4, 5, and 6 electrons,
respectively. (Remember that atomic models
are limited in what they can represent. Energy
levels are not actual physical locations.)
5.1 Carbon is KEY!

Carbon can connect to 4 other atoms.
–



It has 4e- in its outer cloud, but wants 8e-
Organic : carbon
Inorganic : no carbon
Hydrocarbons – consist of C and H, fuels
–
Ex: methane CH4
Figure 5-1
The carbon backbones of organic
molecules can take many shapes. These
molecules may include single, double,
and rarely, triple bonds. The only rule is
that each carbon forms a total of four
bonds.
Functional Groups

Group of atoms - acts in predictable ways
Figure 5-2
These four common functional groups give
specific properties to the organic molecules
that contain them.

Hydroxyl groups - hydrophilic
–
–

Monomers
–

Hydrophilic =“water-loving”
Hydrophobic = “water-fearing”
Single molecular units
Polymers
–
Long chains of monomers
Four groups of large Biomolecules




Carbohydrates
Lipids
Proteins
Nucleic Acids
Building and Breaking Polymers

Dehydration reaction: BUILDING
–
–

Water released
Monomer added
Hydrolysis reaction: BREAKING
–
–
Water added
Polymer broken down
Dehydration
Figure 5-4
In the dehydration reaction,
two monomers bond to each
other, making a polymer chain
longer. The hydroxyl group of
one monomer reacts with a
hydrogen atom from the other
monomer. The reactions
involved ultimately release a
water molecule.
Hydrolysis
Figure 5-5
In the hydrolysis reaction, the
addition of a water molecule
breaks the polymer chain.
5.2 Carbohydrates - fuel , building
material

Carbohydrate
–
–

Organic compound - sugar molecules
Any sugar is a multiple of CH2O
Monosaccharide
–
–
–
Simple sugar, 1 sugar unit
Ex: glucose, fructose, galactose
All end in -ose
Figure 5-6
The complete structural
diagram of the
monosaccharide glucose
(left) shows all its atoms.
The simplified
representation (right)
shows just the core ring
formed by some of the
carbon and oxygen atoms.
Ring shapes are common in
sugar molecules found in
nature.
Complex Sugars

Disaccharide
–
–

“double sugar” – 2 monosaccharides
Ex: sucrose, plant sap, table sugar
Polysaccharide
–
–
Many simple sugars together
All glucose monomers – store sugar


–
Plants – starch
Animals – glycogen
Cellulose: in plants, protects/stiffens plant

Fiber –can’t be digested by humans
Figure 5-7
Sucrose is a
disaccharide
(double sugar)
consisting of
two
monosaccharid
es linked
together.
Figure 5-8
Glycogen, cellulose, and starch are three
types of polysaccharides found in food.
Though all three polymers are composed
of the same monomer, glucose, the way
the glucose monomers link together is
different for each.
5.3 Lipids - fats and steroids

Lipid: Hydrophobic
–

boundary for cells
Fat:
–
3 carbon backbone = glycerol + 3 fatty acids (long
hydrocarbon chains)
Figure 5-9
Certain vegetable oils contain unsaturated fat
molecules, which have at least one double
bond in at least one of the fatty acid chains. In
this case, the double bond is located about
halfway along the bottom chain.
Saturated Fat vs. Unsaturated Fat

Saturated fat:
–
–
–

max possible # of H atoms in chain
all single bonds
animal fats - lard , butter
Unsaturated fat:
–
–
–
–
< max # of H atoms in one or more or its fatty acid chains
some double bonds
fruits, vegetables, and fish
corn oil, olive oil
Steroids and Cholesterol

Steroids
–
–
–

Lipids - four fused rings of carbon for base
All steroids - core set of four rings
Functional groups on rings differ
Cholesterol
–
–
Essential in cell membranes
Where other steroids are produced
Figure 5-10
The only difference in these two
steroid hormones is the location
of their functional groups. Yet,
these two molecules contribute to
major differences in the
appearance and behavior of male
and female mammals.
5.4 Proteins – cellular functions

Protein: polymer of amino acids
–



20 kinds of amino acids
Amino acid: central carbon atom bonded to
four partners
Polypeptide: chain of amino acids
Denaturation: protein loses its normal shape
–
change in temperature, pH
Figure 5-12
All amino acids consist of a central carbon
bonded to an amino group, a carboxyl group,
and a hydrogen atom. The fourth bond is with
a unique side group. The differences in side
groups convey different properties to each
amino acid.
Figure 5-13
The order of amino acids
makes each polypeptide
unique. There are 129 amino
acids in this protein, called
lysozyme. The three-letter
symbols are abbreviations for
the amino acid names.
5.5 Enzymes = proteins that speed
up specific reactions in cells

Activation energy:
–


Catalyst: speed up chemical reactions
Enzyme: special protein – catalyst in organisms
–
–

Ex: sucrase, amylase
-ase = enzyme
Substrate: binds to the enzyme; must fit into active site
–

“start up” energy - triggers a chemical reaction
Ex: sucrose
Active site: place (on enzyme) where the substrate fits
–
Lock and key
Figure 5-15
The activation energy barrier is
like a wall between two parts of a
pond. If an enzyme lowers the
wall, more frogs have enough
energy to reach the other side.
Figure 5-16
A substrate binds to an enzyme
at an active site. The enzymesubstrate interaction lowers the
activation energy required for
the reaction to proceed. In this
example, water is added to the
weakened bond in sucrose,
breaking sucrose into glucose
and fructose.
The End