Key Concepts:
-What are elements and compounds?
-What are the main kinds of organic molecules in living things?
-How is water important to the function of cells?
PRENTICE HALL - CELLS AND HEREDITY
CHAPTER 1 - CELLS STRUCTURE AND FUNCTION
Section 3 – Chemical Compounds in Cells
Key Terms and
Connections
Main Ideas and Visuals
Elements and Compounds
-Air is a mixture of gasses including both elements
and compounds.
E.g. Three gasses in the air include oxygen,
nitrogen, and carbon dioxide.
Element------------------->
Compound---------------->
Elements:
-An element is any substance that cannot be
broken down into simpler substances.
-The smallest unit of an element is an atom, and
each element is only made up of one kind of atom.
E.g. Some elements found in organisms include
carbon, hydrogen, oxygen, nitrogen, phosphorus,
and sulfur.
Compounds:
-A compound is formed when two or more
elements chemically combine.
-Most elements in organisms occur in the form of
compounds.
-The smallest unit of many compounds is a
molecule.
E.g.
Water
is
an
QuickTime™ and a
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Questions and
Comments
example of a compound.
Organic and Inorganic Compounds:
-Many compounds found in organisms contain
carbon.
-Most compounds that contain carbon are called
organic compounds.
E.g. Some important groups of organic
compounds found in living things are
carbohydrates, lipids, proteins, and nucleic
acids.
-Since foods you eat come from living things, many
of these compounds are found in food.
-Organisms also contain compounds that do not
contain carbon called inorganic compounds.
E.g. Some inorganic compounds include water and
table salt.
Carbohydrates
Carbohydrate-------------> -A carbohydrate is an energy-rich organic
compound made of carbon, hydrogen, and oxygen.
E.g. Sugars and starches are 2 examples of
carbohydrates.
-Sugars are produced during the food-making
process that takes place in plants (photosynthesis).
When these sugar molecules combine, they form
complex carbohydrates: large molecules called
starches.
-Plant cells store excess energy in molecules of
starch, thus many foods that come from plants
contain starch.
E.g. These foods include potatoes, pasta, rice, and
bread.
-When you eat these foods, your body breaks
down the starch into glucose, a sugar that your
-What is the distinction
between compounds
that contain carbon and
compounds that do not?
Why are compounds
containing carbon called
“organic” compounds?
-How can a compound
be energy-rich? What
energy does it store?
-How can a cell store
“energy” in molecules of
starch? What form of
energy do they store?
- Does the mitochondria
Lipids----------------------->
-Lipids are very similar
to carbohydrates! They
are made of the same
elements, and are both
energy-rich.
Proteins-------------------->
cells use to produce energy.
in cells convert glucose
-Carbohydrates are also important components of
into cellular energy?
some cell parts.
E.g. The cellulose that makes up cell walls is a type
of carbohydrate. Carbohydrates are also found in
cell membranes.
Lipids
-Lipids are energy-rich organic compounds made
of carbon, hydrogen, and oxygen.
E.g. Fats, oils, and waxes are all lipids.
-Lipids contain even more energy than
carbohydrates.
-The cell membrane is mainly made of lipids.
-Cells store energy in lipids for later use.
E.g. During the wintertime, a dormant bear lives on
the energy stored as fat within its cells.
Proteins
-Proteins are large organic molecules made of
carbon, hydrogen, oxygen, nitrogen, and, in some
cases, sulfur.
E.g. Foods high in protein include meat, eggs, fish,
nuts, and beans.
Structure of Proteins:
Amino acids---------------> -Amino acids are the smaller molecules that make
up protein.
-The 20 amino acids are like the
-Cells combine the 20 types of existing amino acids
26 letter of the alphabet. By
in a variety of different ways to produce different
combining different letters in
kinds of proteins.
different orders, thousands of
-If proteins are made up
of the molecules, amino
acids, then aren’t they
compounds and not
molecules?
words can be formed.
Enzyme-------------------->
Nucleic acids------------->
Functions of Proteins:
-Proteins form parts of the cell membrane and also
make up many of the organelles within a cell.
-An enzyme is also a type of protein that speeds up
chemical reactions within living things.
-Without enzymes, many chemical reactions
necessary for life would either take too long to
occur, or would not occur at all.
Nucleic Acids
-Nucleic acids are very long organic molecules
made of carbon, oxygen, hydrogen, nitrogen, and
phosphorus.
-Nucleic acids contain the instructions cells need to -So are nucleic acids
carry out all the functions of life.
-The two kinds of nucleic acids are, DNA & RNA.
DNA-------------------------> -DNA (Deoxyribonucleic Acid) is the genetic
material that carries out information about an
organism, and is passed from parent to offspring.
-The information in DNA also directs all of the cell’s
functions, thus most of the DNA within a cell is
found in the cell’s chromatin.
RNA-------------------------> -RNA (Ribonucleic Acid) is found in the cytoplasm
and nucleus, and it plays an important role in the
production of proteins.
Water and Living Things
-Water takes up about 2/3 of your body, and it
plays many important roles in cells.
E.g. Most chemical reactions in cells involve
substances that are dissolved in water, and water
molecules themselves take part in many chemical
reactions within cells.
*Most chemical reactions within cells could not
take place without water.
-A cell without water
-Water also helps cells maintain their size and
would be like a balloon
shape.
with no air.
-Finally, since water changes temperature slowly, it
helps keep the temperature of cells from changing
rapidly.
located within the
chromatin of cells?
-What is this important
role?
Doesn’t the cytoplasm
do this? Or is the
cytoplasm mostly made
up of water?