Download 11.2 DNA and reproduction

Matter and Change
• Chapter Nine: Acids, Bases and Solutions
• Chapter Ten: Chemical Reactions
• Chapter Eleven: The Chemistry of Living Things
Chapter Eleven: The Chemistry of
Living Things
• 11.1 The Chemistry of Carbon
• 11.2 Proteins, Fats and Nucleic Acids
Investigation 11B
The Structure of DNA
• How does a DNA molecule carry information?
11.2 Proteins, fats and nucleic acids
• Four important molecules in living
things are:
– carbohydrates
– proteins
– fats
– nucleic acids
11.2 Fats
•
•
Fats are high-energy molecules that
plants and animals use to store energy.
A fat molecule has a two-part structure.
11.2 Proteins
•
•
Proteins are basic molecular building blocks
of cells and all parts of animals.
Proteins are among the largest organic
molecules.
Why is the shape of a
protein important?
11.2 Saturated and unsaturated fats
• In a saturated fat,
carbon atoms are
surrounded by as many
hydrogen atoms as
possible.
• An unsaturated fat
has fewer hydrogen
atoms than it could
have.
11.2 Enzymes
• Thousands of chemical reactions are going
on in your body each second, involving
thousands of chemicals.
• Catalysts help control chemical reactions.
• You can think of catalysts as helper
molecules that allow a reaction to proceed
in many small steps instead of all at once.
11.2 Enzymes
• Enzymes are special protein catalysts.
11.2 Enzymes
• Enzymes are special proteins acting as catalysts.
The body has thousands
of different enzymes.
Each one is specific and
matched with its target
molecule.
11.2 DNA and nucleic acids
• Cells must continually create
the proteins they need.
• In the process called protein
synthesis, proteins are made
using the instructions found in
DNA molecules.
Where does the energy needed for this reaction come from?
11.2 DNA and nucleic acids
• DNA is a nucleic acid .
• A DNA molecule is put
together like a twisted
ladder.
This model shows a short
piece of the flattened DNA
ladder.
A DNA molecule is usually
twisted and much longer.
11.2 DNA
• Each side of the
ladder is made of:
– 5-carbon sugars
called deoxyribose
– and phosphate
groups.
11.2 DNA
• There are four
nitrogen bases in
two matched pairs.
11.2 DNA and amino acids
• The assembly of proteins is coded by a certain
sequence of nitrogen bases.
• Below the sequence of thymine, thymine and
adenine would build the amino acid leucine.
What base sequence stops the assembly of proteins?
11.2 DNA and reproduction
• When an organism reproduces, the DNA
molecule is able to make exact replicas of
itself.
11.2 DNA and reproduction
• These enzymes play a role when DNA copies
itself:
– Helicase enzymes untwist the DNA helix.
– Ligase enzymes unzip the DNA
– Polymerase enzymes rebuild nitrogen bases on the
open strands.
11.2 DNA and reproduction
• Changes in DNA are called mutations.
• Changes in DNA lead to new proteins,
and changes in living organisms that are
passed on in successive generations.