Download Unit 05 - Lessons 1-4

2.2 Properties of Water
I. Water s unique properties allow life to exist on Earth.
A. Life depends on hydrogen bonds in water.
B. Water is a polar molecule.
1. Polar molecules have slightly charged regions due to unequal
sharing of electrons.
_
Ex) water molecule
*oxygen hogs electrons and is
partially negative
O
*hydrogen becomes partially
H
H
positive
+
+
2.  Oppositely charged ends of neighboring water molecules are
attracted to each other (like a magnet).
a. This allows water to bead up on smooth surfaces.
2.2 Properties of Water
C. Hydrogen bonds are responsible for three important properties of
water.
1. high specific heat – water absorbs large amounts of energy
without raising its temperature very much
2. cohesion – molecules stick to themselves
Ex) water rising above the level of a glass without spilling
3. adhesion – molecules stick to other charged molecules that are
near them
Ex) water not spilling out of container that is flipped upside
down with a paper lid
2.2 Properties of Water
D. Many compounds dissolve in water to form a solution.
1. solution – formed when one substance dissolves in another
a. A solution is a homogeneous mixture (mixed together so
well that you cannot distinguish the different parts)
b.  Like Dissolves Like – polar water is able to dissolve any
polar substance or any ionic compound due to the charges
Ex) salt (NaCl – ionic compound) dissolves in water
c. solvent – substance that dissolves other substances
d. solute – substance that is dissolved
solution
2.2 Properties of Water
E. Some compounds form acids or bases.
1. Some compounds break into ions (dissolve) in water.
a. acids – releases a hydrogen ion (H+) it dissolves in water
1. creates acidity
2. have high H+ concentration
b. bases - removes hydrogen ions from solution
1. creates alkalinity
2. have high OH- concentration
2.  We measure H+ concentration with the pH scale.
a. pH scale runs from 0-14
Stronger H+ conc.
ß Acids
Neutral
Bases à Weaker H+ conc.
2.2 Properties of Water
3. Most organisms need to keep their internal pH close to 7
(neutral)
a.  accomplished with the help of chemicals called buffers
Ex) buffers in your blood maintain a normal pH and keep your
body at homeostasis
2.3 Carbon-Based Molecules
II.  Carbon-based molecules are the foundation of life.
A. Carbon – can form covalent bonds with up to four other atoms,
including other carbon atoms
1. structure - 3 general types of structures
a. straight chain
b. branched chain
c. ring
2.3 Carbon-Based Molecules
B.  Many carbon-based molecules are made of many small subunits
bonded together.
a. monomers – individual subunits
b. polymers – combinations of monomers
2.3 Carbon-Based Molecules
C. Carbohydrates are made of carbon, hydrogen, and oxygen.
1.  monosaccharides – simple sugars
Ex) glucose
2. polysaccharides – starches, cellulose, and glycogen
2.3 Carbon-Based Molecules
3. Carbohydrates can be broken down to provide energy for cells.
4. Some carbohydrates are part of cell structure.
Polymer (starch)
Starch is a polymer of
glucose monomers that
often has a branched
structure.
Polymer (cellulose)
monomer
Cellulose is a polymer of
glucose monomers that
has a straight, rigid
structure
2.3 Carbon-Based Molecules
III. Lipids are nonpolar molecules that include fats, oils, and
cholesterol.
A.  Many contain carbon chains called fatty acids.
B.  Fats and oils contain fatty acids bonded to glycerol.
Triglyceride
C. Lipids have several different functions.
1.  broken down as a source of energy (fats)
2.  used to make hormones
2.3 Carbon-Based Molecules
3. make up cell membranes
a. polar phosphate head
b. nonpolar fatty acid tails
Phospholipid
2.3 Carbon-Based Molecules
D. Fats and oils have different types of fatty acids.
1. saturated fatty acids
2. unsaturated fatty acids
2.3 Carbon-Based Molecules
IV.  Proteins are polymers of amino acid monomers.
A.  Twenty different amino acids are used to build proteins in
organisms.
B.  Amino acids differ in side groups, or R groups.
C.  Amino acids are linked by peptide bonds.
2.3 Carbon-Based Molecules
D.  Proteins differ in the number and order of amino acids.
1.  Amino acids interact to give a protein its shape.
2.  Incorrect amino acids change a protein s structure and
function.
Hemoglobin
hydrogen bond
2.3 Carbon-Based Molecules
V.  Nucleic acids are polymers of monomers called nucleotides.
A. Nucleotides are made of a sugar, phosphate group, and a
nitrogen base.
A phosphate group
nitrogen-containing
molecule,
called a base
deoxyribose (sugar)
B. There are 2 kinds: DNA and RNA.
1.  DNA stores genetic information.
2.  RNA builds proteins.
DNA
RNA
2.5 Enzymes
VI. Enzymes are catalysts for chemical reactions in living things.
A. Catalysts – substances that speed up chemical reactions by
decreasing activation energy needed
B. Enzymes – are catalysts in living things
1.  Enzymes are needed for almost all processes.
2.  Most enzymes are proteins.
3.  Disruptions in homeostasis can prevent enzymes from
functioning.
2.5 Enzymes
4. Enzymes function best in a small range of conditions.
5.  Changes in temperature and pH can break hydrogen bonds.
6.  An enzyme s function depends on its structure.
a. An enzyme s structure allows only certain reactants to bind to
the enzyme.
1. substrates – bind to enzyme s active sites
substrates
(reactants)
enzyme
Substrates bind to
an
enzyme at certain
places called active
sites.
2.5 Enzymes
b. Lock-and-Key Model – only particular substrates will bond to
certain enzymes (like keys in a lock…only certain keys work)
1. substrates brought together
2. bonds in substrates weakened
Substrates bind to an
enzyme at certain places
called active sites.
The enzyme brings
substrates together
and weakens their
bonds.
The catalyzed reaction forms
a product that is released
from the enzyme.