Transcript Chapter 2 The Chemistry of Life

Chapter 2
The Chemistry of Life
Life depends on chemistry.
Millions of chemical reactions occur in living
organisms every day. Organisms rely on
chemical reactions in order to function. Food
must be broken down, gases must be
exchanged, molecules must be built.
And unlike everything else on Earth, life is
made of four special molecules in
particular…
Unit Theme Questions

We will answer the questions…
 What
 If
do you need to get in your diet to live?
you eat the cells of other plants and animals
all the time, including their DNA, why aren’t
you part-cow now? Part-lettuce? Part-corn?
Levels of Organization
Levels of Organization

http://micro.magnet.fsu.edu/primer/java/sci
enceopticsu/powersof10/
Section 2-1
The Nature of Matter
Atoms

Atom - Basic unit of matter.
 All
matter - including living things - is made up
of groups of atoms “stuck” (bonded) together.
Elements

Element – a kind or “species” of atom. There are
100+ elements or kinds of atoms.

Living things are mostly made of six elements:
C, H, O, N, P, S (in order of most to least
common)
1.
2.
3.
4.
5.
6.
Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus
Sulfur
Elements

What element is…
 N?
 C?
 S?
 P?
 H?
 O?
Chemical Compounds

Compound and Molecules – “clumps of
atoms,” substances formed by the chemical
bonding of two or more elements

Written as chemical formulas. Letter = element,
small number = how many atoms of the element
are in one molecule
Example: Water or H2O = 2 hydrogen atoms and 1
oxygen atom
 Example: Glucose or C6H12O6 = 6 carbon atoms, 12
hydrogen atoms, and 6 oxygen atoms

Chemical Compounds

How many atoms of each element are in
these compounds?
(Nitric acid) HNO3
 (Salt or Sodium Chloride) NaCl
 (Potassium Phosphate) KPO4
 (Carbon dioxide) CO2
 (Sulfur dioxide) SO2
 (Glycerol) C3H8O3

CHECKPOINT

A living thing is made up of cells, which are
made up of ___________, which are made
up of ___________, which are different
kinds of ___________.
Chemical Reactions

Chemical reaction – atoms break and/or make bonds to form
different compounds, represented by an arrow
 Reactants – elements or compounds that enter into a
reaction; come BEFORE the arrow
 Products – elements or compounds that are produced by the
reaction; come AFTER the arrow
Example: 2H2O2
(reactant)

Example: 2K + Cl2 
(reactants)
2H2O + O2
(products)
2KCl
(product)
Chemical Reactions

Identify the products and reactants in each
of these reactions.
8 Fe + S8 -> 8 FeS
 2 H2O -> 2H2 + O2
 Zn + 2 HCl -> ZnCl2 + H2
 NaCl + AgNO3 -> NaNO3 + AgCl
 C10H8 + 12O2 -> 10CO2 + 4H2O

Section 2-3
Organic Molecules Carbon Compounds
The Chemistry of Carbon


Organic molecules – carbon-based molecules
Carbon forms the backbone or basic structure of life’s
molecules, because it is abundant and flexible.

Can bond with up to 4 other atoms at once.
 Can form single, double or triple bonds.
 Bonds easily with other carbon atoms to form the backbone of
large organic molecules.
 Can bond with many different elements
such as H, O, P, S, N.
Four Groups of Organic Molecules

Most molecules in cells are so large they
are called macromolecules or “giant
molecules.”

Most macromolecules = polymers, which are
chains of repeating smaller molecules called
monomers.

Polymerization – Joining monomers
together to make a polymer

Organic molecules are classified into 4
groups:
1. Carbohydrates
2. Lipids
3. Nucleic acids
4. Proteins
Macromolecules

For each macromolecule, you should know:
 At
least 2 examples (not the food they’re in, the
names of the chemicals themselves)
 Functions (jobs) in living cells
 Name of monomer
 Name of polymer

Remember our question: what do you need to
get in your diet to live?
 These
four macromolecules!
Carbohydrates



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Examples: Sugars (like glucose) and starches
Functions:
 Main source of ENERGY for living things
 Used for structure in plants and some animals
Monomer – monosaccharide (simple sugar, like glucose),
Polymer – polysaccharide (complex carbohydrate, like
starch)
Nucleic Acids



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Examples: DNA and RNA
Function: Store and transmit genetic INFORMATION
Monomer – nucleotide
Polymer – nucleic acid
Proteins


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Examples: enzymes, cell membrane proteins,
muscle proteins
Functions: Many!
 Control rate of chemical reactions
 Regulate cell processes
 Structure
 Movement and transport
 Growth and repair
 Chemical communication
Monomer – amino acid
Polymer – polypeptide or protein
Structure or shape of a protein is extremely
important to its function.
Lipids
Examples: Fats, oils, waxes, phospholipids
 Functions:
 Long-term energy STORAGE
 Make up parts of biological membranes and waterproof
coverings
 Generally not
soluble (doesn’t mix)
in water
 No monomers or
polymers.

Section 2-4:
Chemical Reactions
and Enzymes
Energy in Reactions

Chemical reactions don’t
happen automatically. (see
graphs)

Some reactions are too slow or
require too much energy to happen
in cells… unless they have help.

Activation energy – the energy
needed to get a reaction started
Enzymes


Enzymes = proteins
that speed up chemical
reactions that take
place in cells
Activation energy
without enzyme
Activation energy
with enzyme
Enzymes work by
lowering the activation
energy of the reaction,
making it easier which
makes it faster.
Course of Reaction
Enzymes and Reactions

Think cars:
 Which
car finishes the race first, the one that
took MORE gas before it would start, or the
one that took LESS?
Enzyme Action

Catalyst = A chemical that speeds up a
reaction without being used up or altered.

Enzymes are biological catalysts.

Each enzyme = unique shape = only binds to a
specific reactant = only catalyzes one kind of
reaction.
Enzyme Animations
http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter2/animation__ho
w_enzymes_work.html
http://www.lpscience.fatcow.com/jwanamaker/animations/Enzyme%
20activity.html
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapter25/animation__en
zyme_action_and_the_hydrolysis_of_sucrose.html
Enzyme Action
Products
Enzyme
Substrates
Active site
Products are
released. Enzyme
is available again.
Substrates bind to
enzyme at active site.
Chemical reaction occurs and
substrates are changed to products.
Enzyme Action
Product is
released. Enzyme
is available again.
Reactants bind
to the enzyme at
the active site.
Chemical reaction
changes reactants
to products.
Effects of Altered pH or Temperature
on Enzyme Action
A change in the enzyme
prevents reactants from
binding. Shapes don’t match.
Chemical reaction can’t
occur. Reactants don’t get
changed to products.
Summary: An enzyme outside of its OPTIMAL environment does not function as well,
which means it will not make the reaction proceed as QUICKLY.
pH and Buffers

pH scale – measurement system of
how acidic or basic something is.
Ranges from 0 –14
 pH
> 7 : base (soaps, cleaners)
 pH = 7 : neutral (pure water)
 pH < 7 : acid
(tomatoes, lemons)

pH in human cells must be kept
between 6.5 and 7.5 or chemical
reactions will be affected.

pH and temperature affect how well
enzymes work because they change
the shape of the protein.
Optimal Temperature and pH

Every enzyme has an
optimal (best)
temperature and pH
 Temperature
or pH that’s
too high or low makes the
enzyme less effective
 Optimum temp/pH tends to
match the organism’s
natural environment
What’s this enzyme’s optimum temperature?
Effect of Cold Temperature

If it COLDER than the optimum
temperature, the substrate is moving more
slowly, so it doesn’t encounter the enzyme
as often = reaction slows down
http://www.kscience.co.uk/animations/model.swf
Effect of pH and High Temperature

If it is too HOT, or the pH is too HIGH OR
LOW, the enzyme is denatured
 Denaturation
= the warping of a protein’s
shape
 The high temp or wrong pH breaks bonds
between amino acids = unravels enzyme =
substrate can’t fit anymore = reaction stops
http://highered.mcgrawhill.com/sites/0072507470/student_view0/chapt
er2/animation__protein_denaturation.html
Enzyme Thought Problems
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1. Two plants live in a 35 degree environment. Which
one is more likely to survive and reproduce: the one
whose enzymes work best at 30 degrees, or the one
whose enzymes work best at 20 degrees? Why?
2. Your body temperature is 98.6 degrees, and your
body’s pH is close to 7. At what temperature and pH
do you think most human enzymes probably work?
3. Your cells can live at 90 degrees. The cells of
bacteria from Antarctic ice, however, die at 70
degrees. Why?
4. Your body must maintain homeostasis: you must
keep your body at a constant temperature and pH.
Why is this essential to your survival?
Enzyme Thought Problems
5. At which pH do each of
these enzymes perform
optimally (best)? At which
pH do these enzymes
become denatured?
 6. Which enzyme is
probably found in a human
stomach?
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