Essential Cell Biology: Chapter 4 -
Protein Structure & Function
Protein molecules - ANS-Long chains of amino acids held together by peptide bonds
What are proteins referred to as? - ANS-Polypeptides
(Amino acid chains are called polypeptide chains)
What do proteins embedded in the plasma membrane form? - ANS-Channels and pumps that
control the passage of nutrients and other small molecules into and out of the cell
Enzyme function - ANS-Speed up (catalyze) chemical reactions
Structural protein function - ANS-Provide mechanical support to cells and tissues
Transport protein function - ANS-Carry small molecules or ions
Motor protein function - ANS-Generate movement in cells and tissues
(Uses hydrolysis of a tightly bound ATP molecule to drive an orderly series of conformational
changes)
Storage protein function - ANS-Stores amino acids or ions
Signal protein function - ANS-Carries signals from cell to cell
Receptor protein function - ANS-Detects signals and transmits them to the cells response
machinery
Gene regulatory protein function - ANS-Binds to DNA to switch genes on or off
Special purpose protein function - ANS-Highly variable
N terminus - ANS-The end of the polypeptide chain that carries the amino group (NH3+)
C terminus - ANS-The end of a polypeptide chain that carries the carboxyl group (COO-H)
, Amino acid side chain - ANS-Projects from the polypeptide backbone. It gives each amino acid
a unique property like polar (hydrophilic), nonpolar (hydrophobic), negative or positive charge
How many different amino acids are commonly found in proteins? - ANS-20
List the three types of noncovalent bonds that help proteins fold & maintain their shape -
ANS-Hydrogen bonds, electrostatic attractions, van der waals attraction
Hydrophobic interaction - ANS-A weak force that helps proteins fold into compact conformations
What factor determines a proteins FINAL folded conformation? - ANS-When free energy is
minimized
What does it mean when a protein is unfolded and how? - ANS-It means it is denatured by
treatment with a solvent that disrupt the noncovalent interactions holding the folded chain
What happens to a protein when the denaturing solvent is removed? - ANS-The protein refolds
back to its original conformation, a process called renaturation
Prions - ANS-Misfolded proteins that form aggregates that can damage to cells and whole
tissues.
It is infectious and causes neurodegenerative diseases like Alzheimer's or mad cow disease.
Question 4-1: Urea is a molecule that
disrupts the hydrogen-bonded
network of water molecules. Why
might high concentrations of urea
unfold proteins? The structure of
urea is shown here. - ANS-Urea is a very small molecule that functions both as an efficient
hydrogen-bond donor (through its -NH2 groups) and as an efficient Hydrogen bond acceptor
(through its -c=o group). It can squeeze between hydrogen bonds that stabilize protein
molecules and thus destabilize protein structures.
In addition, nonpolar side chains are held together in the interior of folded proteins because they
disrupt the structure of water if they are exposed.
At high concentrations of urea, the H-bonded network of water molecules becomes disrupted so
that these hydrophobic forces are significantly diminished.
Proteins unfold in urea as a consequence of its effect on these two forces.
Chaperone proteins - ANS-Assists proteins to fold into its correct conformation
Protein Structure & Function
Protein molecules - ANS-Long chains of amino acids held together by peptide bonds
What are proteins referred to as? - ANS-Polypeptides
(Amino acid chains are called polypeptide chains)
What do proteins embedded in the plasma membrane form? - ANS-Channels and pumps that
control the passage of nutrients and other small molecules into and out of the cell
Enzyme function - ANS-Speed up (catalyze) chemical reactions
Structural protein function - ANS-Provide mechanical support to cells and tissues
Transport protein function - ANS-Carry small molecules or ions
Motor protein function - ANS-Generate movement in cells and tissues
(Uses hydrolysis of a tightly bound ATP molecule to drive an orderly series of conformational
changes)
Storage protein function - ANS-Stores amino acids or ions
Signal protein function - ANS-Carries signals from cell to cell
Receptor protein function - ANS-Detects signals and transmits them to the cells response
machinery
Gene regulatory protein function - ANS-Binds to DNA to switch genes on or off
Special purpose protein function - ANS-Highly variable
N terminus - ANS-The end of the polypeptide chain that carries the amino group (NH3+)
C terminus - ANS-The end of a polypeptide chain that carries the carboxyl group (COO-H)
, Amino acid side chain - ANS-Projects from the polypeptide backbone. It gives each amino acid
a unique property like polar (hydrophilic), nonpolar (hydrophobic), negative or positive charge
How many different amino acids are commonly found in proteins? - ANS-20
List the three types of noncovalent bonds that help proteins fold & maintain their shape -
ANS-Hydrogen bonds, electrostatic attractions, van der waals attraction
Hydrophobic interaction - ANS-A weak force that helps proteins fold into compact conformations
What factor determines a proteins FINAL folded conformation? - ANS-When free energy is
minimized
What does it mean when a protein is unfolded and how? - ANS-It means it is denatured by
treatment with a solvent that disrupt the noncovalent interactions holding the folded chain
What happens to a protein when the denaturing solvent is removed? - ANS-The protein refolds
back to its original conformation, a process called renaturation
Prions - ANS-Misfolded proteins that form aggregates that can damage to cells and whole
tissues.
It is infectious and causes neurodegenerative diseases like Alzheimer's or mad cow disease.
Question 4-1: Urea is a molecule that
disrupts the hydrogen-bonded
network of water molecules. Why
might high concentrations of urea
unfold proteins? The structure of
urea is shown here. - ANS-Urea is a very small molecule that functions both as an efficient
hydrogen-bond donor (through its -NH2 groups) and as an efficient Hydrogen bond acceptor
(through its -c=o group). It can squeeze between hydrogen bonds that stabilize protein
molecules and thus destabilize protein structures.
In addition, nonpolar side chains are held together in the interior of folded proteins because they
disrupt the structure of water if they are exposed.
At high concentrations of urea, the H-bonded network of water molecules becomes disrupted so
that these hydrophobic forces are significantly diminished.
Proteins unfold in urea as a consequence of its effect on these two forces.
Chaperone proteins - ANS-Assists proteins to fold into its correct conformation
