Transcript Atoms - NorthMacAgScience

Chapter 2
The Chemistry of Life
1
Section 1
The Nature of Matter
2
Atoms

Atoms:
Basic unit of matter.
 Greek word atomos.



“unable to be cut”
Factoid:

Atoms are so small that if you lined up 100 million of
them, they would barely be the width of your pinky.
3


Though atoms are small, they are made of even
smaller particles.
P. 35, fig. 2-1
Protons-+ charged
 Neutrons-no charge
 Electrons- (-) charged

4

Protons & neutrons are bound together in the
nucleus of an atom.

Electrons are in constant motion around the
nucleus of an atom.

Atoms have equal numbers of protons &
electrons.
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

Electrons travel around the nucleus in an
electron cloud.
They travel in what are called orbitals.
Each orbital contains a certain # of electrons.
 1st orbital has 2e 2nd orbital has 8e 3rd orbital has 8e 4th orbital has 8e
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7
What Element is This?
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Elements & Isotopes

Elements –substances that consist of entirely of 1 type of atom.


Over 100 elements exist, but only about 25 are vital to living things.
The 4 most important elements are:




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Hydrogen
Carbon
Nitrogen
Oxygen
Elements are abbreviated by symbols.




H
C
N
O
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Atomic number:

# above the symbol of the element.
This number represents the # of electrons &
protons in that element.

Example:

Look at Carbon (C)
 What is it atomic #?



6
What does this mean?

6e & 6p
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Isotopes

Isotopes:
Atom of an element that have a different # of
neutrons then that of other atoms of the same
element.
 The sum of protons & neutrons in an atom is called
the atomic mass or atomic weight.
 Some examples:

Carbon-12
 Carbon-13
 Carbon-14


P. 36, fig. 2-2
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

Isotopes are identified by their mass #.
Since isotopes have the same # of electrons,
they have the same chemical properties.
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Radioactive Isotopes

Some isotopes are radioactive.
This means that their nuclei are unstable & they
breakdown over time.
 This radiation can be dangerous.
 But, scientists have a number of uses for them:

Can be used to treat cancers.
 Can be used to age rocks & other items.
 Can be used as a tracer in human organs.

14
Chemical Compounds



In nature most elements are found in
compounds.
Compounds –a substance formed by 2 or more
elements.
These compounds are usually written as
formulas such as:
NaCl
 H20
 CO2

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Chemical Bonds


Compounds are held together by chemical
bonds.
Bond formation involves the electrons that
surround an atom.


AKA Valence Electrons
The main types of chemical bonds are:
Ionic
 Covalent

16
Ionic Bonds


Ionic bond –when one or more electrons are
transferred from one atom to another.
Atoms that lose an electron have a pos. charge.


Atoms that gain an electron have a neg. charge.


Na+
Cl-
Pos. & neg. charged atoms are called ions.
Pos. atoms are cations.
 Neg. atoms are anions.

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
P. 38, fig. 2-3 shows a ionic bond b/t Na & Cl.
Na will easily lose an electron b/c it is a + Na ion.
 Likewise, Cl will easily gain an electron b/c it is a Cl ion.
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Ionic Bond
http://www.youtube.com/watch?v=xTx_DWbo
EVs&feature=player_detailpage
http://www.youtube.com/watch?v=G49gxlIlSIc
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Covalent Bonds

Covalent Bonds –a bond formed when electrons are
shared b/t atoms.

You can have single, double, or triple covalent bonds.


Molecules are formed when atoms are joined via a
covalent bond.


Read bottom paragraph on p. 38
A molecule is the smallest unit of most compounds.
P. 38, fig. 2-4
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Covalent Bonding
http://www.youtube.com/watch?v=lGEA5PVW
QiQ&feature=related
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Van der Waals Forces


Van der Waals Forces –a slight attraction that
develops b/t the opposite charged regions of
nearby molecules.
Example:
A gecko’s toes.
 Fig. 2-5

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Chapter 2
Section 2
Properties of Water
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
75% of the
Earth is
covered by
water.
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The Water Molecule


Water = H2O
Water exists in 3 states:




Liquid
Gas
Solid
Water as a molecule has a neutral charge.

Figure it out….

10e- & 10p+
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Characteristics of Water

Polarity:

Water molecules are polar b/c there is an uneven
distribution of e- b/t the O & H atoms.
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
Hydrogen Bonds:

B/c water is polar, it can attract other water
molecules.


Fig. 2-7
The (+) & (-) charges are weaker than the charges of
+ & - ions.
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28

When 2 or more water molecules join up, they
are held there by a hydrogen bond.
Hydrogen
Bond
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

Hydrogen bonds are weaker than ionic or
covalent bonds.
Also, a water molecule can bond to 4 other
water molecules at a time.

This enables water to have some interesting
properties.
30
http://www.youtube.com/watch?v=KiZJOTt3D
l0&feature=related
31

Cohesion –attraction b/t molecules of the same
substance.

Example:
Water forms beads on a smooth surface.
 The reason why some insects can walk on water.


AKA surface tension or water tension.

Fig. 2-8
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
Adhesion –an attraction b/t molecules of
different substances.

Example:

Capillary action
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35
Solution & Suspensions



Water isn’t always pure, it is often found in a
mixture.
Mixture –a material composed of 2 or more
elements or compounds that are physically
mixed together, but not chemically combined.
Examples:
Salt & pepper
 Sand & sugar
 Earth's atmosphere & its gases

36

The 2 types of mixtures that can be made w/
water are:
Solutions
 Suspensions

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Solutions

Solution –a homogeneous mixture of 2 or more
substances in which the molecules are evenly
distributed.

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Solute –substance which is dissolved.
Solvent –substance that dissolves the solute.
Examples:


Salt water
Sugar water

Fig. 2-9

Water is the greatest solvent on Earth!
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Suspensions

Suspension – mixture of water & nondissolved
substances.
blood
 Oil & Water
 Sand & water

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Acids, Bases, & pH

The pH Scale


Fig. 2-10
Pure water = 7
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Acids
Acid –any compound that forms H+ ions in a
solution.
 Ex:

Hydrochloric acid
 Sulfuric acid
 Nitric acid

41

Bases
Base –a compound that produces OH- ions in a
solution.
 Examples:

Lye
 Ammonia
 Oven cleaner

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
Buffers

The pH of fluids w/in cells in the human body are
generally between 6.5-7.5.
If higher or lower it may interfere w/ chem. reactions.
 Buffers have a lot to do w/ maintaining ph in our bodies
& therefore our homeostasis.


Buffers –weak acids or bases that can react w/
strong acids or bases to prevent sudden changes in
pH.
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Section 2-3
Carbon Compounds
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
Read the 1st paragraph….
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The Chemistry of Carbon

Carbon is heavily studied in chemistry for a few
reasons:

C atoms have 4 valence e-.
This means that C can join w/ many other atoms via
strong covalent bonds.
 C can bond such elements as:


H, O, P, S, & N
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
Also, C can bond to other C atoms.

This gives C the ability to form chains.

These chains can be unlimited in length.
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Carbon-carbon bonds can be:
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Single 2e
Double 4e
Triple 6e
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Carbon can form:
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Chains
Rings
Branches
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Macromolecules

Macromolecules –extremely large molecules
found in living orgs.


“Giant molecules”
Macromolecules are made of thousands or even
hundreds of thousands of molecules.
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
Macromolecules are made by polymerization.

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In this process, large compounds are formed by
joining smaller ones together.
The smaller units, called monomers join to form
polymers.

Monomers can be identical or they can be like beads
multicolored necklace.
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
There are 4 groups of organic carbon compounds
found in living things:
Carbohydrates (Carbs)
 Lipids
 Proteins
 Nucleic acids

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Carbohydrates

Carbohydrates –compounds made up of C, H,
& O atoms.
Usually in the ratio of 1:2:1
 Ex:



C6H12O6
Orgs. use carbohydrates as a main source of
energy (E).
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
Examples of Carbs:
Starch
 Sugars
 Cellulose



We break down sugars for energy.
Plants store energy in starches.
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
Single sugar molecules = monosaccharides

Ex:
Galactose
 Fructose
 Glucose

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NOTE: Items them end in “ose” are sugars.
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
2 sugar molecules = disaccharides
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Ex:

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Glucose + Fructose = Sucrose
A large macromolecule formed from many
monosaccharides is a polysaccharide.

Ex:

Glycogen
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Also known as animal starch.
Plants have cellulose & starch as their polysaccharides.
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Lipids

Lipids –a carbon compound made from mostly
C & H.


Usually insoluble in water.
Examples:
Fats
 Oils
 Waxes
 Steroids

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
Lipids are used for:
Storing energy
 Parts of cell membranes
 Waterproof coatings


Fig. 2-14

Glycerol & a fatty acid
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3 types of fatty acids:

Saturated fatty acid

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Unsaturated fatty acid


Has the maximum # hydrogen atoms.
Has at least 1 double carbon-carbon bond.
Polyunsaturated fatty acid

Contain more than 1 carbon-carbon double bond.
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Nucleic Acids
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Nucleic acids –macromolecules containing H,
O, N, C, & P.
Nucleic acids are polymers made up of
nucleotides.
Nucleotides –consist of 3 parts:
A sugar
 A phosphate group
 A nitrogen base
 Fig. 2-15
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Nucleic acids store transmit
genetic info.

There are 2 types:
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DNA
RNA
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Proteins
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Macromolecules that contain N as well as C, H,
& O.
Proteins are polymers of molecules called amino
acids.
Amino acids are the building blocks of proteins.

So, AA’s are monomers of proteins.
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Proteins are some of the most diverse
macromolecules.
There are more than 20 AA in nature.
AA are held together by peptide bonds.

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Peptide bonds are covalent bonds.
The instructions for how AA are put together is
stored in our DNA.
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

Proteins do quite a few things for us.
They:
Control the rate of reactions
 Regulate cell processes
 Used to form bones & muscle
 Used for transport of substances
 Immune responses

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Carbon
Compounds
include
Carbohydrates
Lipids
Nucleic acids
Proteins
that consist of
that consist of
that consist of
that consist of
Sugars and
starches
Fats and oils
Nucleotides
Amino Acids
which contain
which contain
Carbon,
hydrogen,
oxygen
Carbon,
hydrogen,
oxygen
which contain
which contain
Carbon,hydrogen,
oxygen, nitrogen,
phosphorus
Carbon,
hydrogen,oxygen,
nitrogen,
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Section 2-4
Chemical Reactions & Enzymes
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Chemical Reactions

Chemical Reaction – process that changes, or
transforms, one set of chemicals into another.

Chemical reactions can happen very slowly or very
quickly.

Ex:



Rust formation on iron. (slow)
P. 49, fig. 2-18
Chemical reactions always involve the breaking
of chemical bonds.
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69
Look at this Reaction:
P. 49
Carbon Dioxide
Water
Carbonic Acid
CO2 + H2O  H2CO3
Reactants
Products
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Energy in Reactions

Chemical reactions can release E.
Called an exothermic reactions.
 This release can be in the form of:

Heat
 Light
 Sound


Chemical reactions can also absorb E.

Called an endothermic reactions.
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

Every org. must have a source of E to carry out
chemical reactions.
Where do they get this E?
Plants get E through photosynthesis.
 Animals get their E by consuming plants or animals


If you want to breathe, grow, think, or dream
you need a chemical reaction.

Chemical reactions occur when you metabolize, or
break down, digested food.
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Activation Energy


Activation energy –E that is needed to get a
reaction started.
P. 50, fig. 2-19
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Energy Absorbing
Activation
Energy
74
Energy Releasing
Activation
Energy
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Enzymes


Some chemical reactions are too slow or have
too high of a activation E to make them
practical.
To make these reactions a possibility you need a
catalyst.

Catalyst –substance that speeds up a chemical
reaction.

Catalysts lower the activation E required by a reaction.
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
Enzymes –proteins that act as a biological
catalyst.
Enzymes speed up chemical reactions that take place
in cells.
 P. 51, fig. 2-20


Enzymes are very specific.
They usually only catalyze one chemical reaction.
 Enzymes are often named after the reaction they
catalyze.

78
Enzyme Action


How enzymes do their job:
P. 52-53

You have 3 parts:
The Enzyme
 The Substrates
 The Enzyme-Substrate Complex



P. 53, fig. 2-22 bottom
Substrates –the reactants of enzyme-catalyzed
reactions.
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Enzyme Substrate Complex
80
Regulation of Enzyme Activity

Enzyme activity can be affected by:

Temp



Most enzymes work well at 37ºC.
pH
Cells can also control enzyme activity.

They have proteins that act as keys to enzyme activity.

On/off
81

Enzymes are essential for:
Regulating chemical pathways.
 Making materials that cells need.
 Releasing energy
 Transferring information

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