Download General Info: Proteins: • Make up 10

General Info:
Proteins:
• Make up 10-30% of a cell’s mass
• Contain 4 elements: C, H, O and N. Some also contain S
and P
• Serve several functions:
1. Major function: Provides the basic structural material
to build cell parts and enzymes
2. Builds enzymes
3. Makes up hemoglobin of the blood (binds to oxygen)
4. Makes up contractile proteins of muscle
More general info:
Proteins:
•Are made up of smaller molecules
or “building blocks” called amino
acids
•There are 20 different types of
amino acids.
•Structure of an amino acid: an
amine group bound to a
carboxyl group (or organic acid
group)
Putting Proteins together:
•Amino acids are held together with bonds called peptide
bonds.
•The amine of one amino acid is attached to the carboxyl
group of the next in a chain.
•This happens during a dehydration synthesis reaction
(producing a water molecule).
Dehydration Synthesis:
Putting Proteins together:
•Two amino acids together make up a dipeptide.
•Ten or more amino acids bonded together make up a
polypeptide.
•A protein is 50 amino acids bonded together and arranged in
a 3-dimensional configuration.
What determines the difference between one protein and
another?
The combination of the 20 different types of amino acids!
Classifying proteins according to 2 basic
shapes:
1. Fibrous proteins: extended strand-like
appearance.
• Most have a simple structure, but can
display more complex structures.
• Strong and stable
• Well suited to provide structural
support (like a tendon)
Classifying proteins according to 2 basic shapes:
2. Globular protein: compact, spherical proteins
• A more complex structure
• Provide many functions in nearly every biological
process.
• Examples: enzymes and antibodies
Classifying Proteins according to their structural levels (p. 51)
1. Primary structure: All proteins have this level of structureit just refers to the string of amino acids bonded together in
a chain.
Classifying Proteins according to their structural levels (p. 51)
2. Secondary structure: All proteins have one of two types
of this structure held together with hydrogen bonds
between oxygen and hydrogen atoms.
• Most commonly- a chain that coils up like a slinky
• Others- several lined up side by side and pleated in
a sheet.
Classifying Proteins according to their
structural levels (p. 51)
3. Tertiary structure: Many, but not all
proteins have this level of structure:
• The coiled chain of amino acids is
folded back on itself like a loosely
wound ball of string.
• Makes a 3-D structure called a
globular protein.
Classifying Proteins according to their structural levels (p. 51)
4. Quaternary structure: occurs with a few proteins:
•
•
The tertiary protein bonds with 1-3 others forming a
complex group.
Example: hemoglobin
Protein Denaturization:
Proteins denature (unfold) outside the normal ranges of
homeostasis for:
•Temperature
•pH
This causes the protein to stop working properly.
•If the temp. or pH isn’t too extreme, they will refold when
homeostasis is restored.
•If the temp. or pH is extreme, they are permanently
changed and cannot do its original job.
Protein Denaturization:
Example: egg whites that are cooked
One type of protein shape denatures easily and other does not.
Which would denature easily and why?
Globular proteins- their structure is
very complex and held together with
H-bonds which are fragile and break
easily.
Fibrous proteins are rope-like and
stronger so they don’t break as easily.
Enzymes
•Enzyme: a globular protein that acts as a biological catalyst,
speeding up a reaction without changing itself.
•Enzyme structure is specific to its function. Each only helps
one type of reaction.
•Enzymes only increase the speed (rate) of a reaction, but the
speed of the reaction is 1 million times faster than it would
occur without the enzyme present!
•Some enzymes have a “helper” called a cofactor. Many of
these are vitamins. A vitamin cofactor is called a coenzyme.
•Most enzyme names end in “ase”
•The molecule or molecules that it acts on are called
substrates.
How does and enzyme do its work?
1. The enzyme binds to a substrate in a 3-D lock and key
form
2. The enzyme-substrate complex undergoes an internal
rearrangement of atoms so the substrate is changed into
something else.
3. The enzyme releases the product and goes on to find more
substrate and catalyze another reaction.
Why do our bodies only need a small amount of enzymes?
Enzymes aren’t changed during a chemical reaction.
They can be used over and over again!