[BIOL 302] - Midterm Exam Guide - Everything you need to know! (14 pages long)

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BIOL 302
MIDTERM EXAM
STUDY GUIDE
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WHY STUDY PROTEINS
Major workhouses in the cell
Most structurally complex and functionally sophisticated molecules
Considered the "functional unit" in the cell
GENERAL PROTEIN FUNCTIONS
Structural protein- provides the cell with shape and structure
o Ex. Tubulin and actin
Enzymes- catalyze covalent bond breakage or formation
o Ex. Pepsin
Transport proteins- carries other molecules or ions
o Ex. Hemoglobin carrying oxygen
Motor protein- generates movement in cells and tissues
o Ex. Myosin
Storage protein- stores small molecules or ions
o Ex. Ferritin storing iron in the liver
Signal protein- carries signal from cell to cell
o Ex. Insulin-glucose levels
Receptor protein- detects signals and transmits them to the cell's
response machinery
o Ex. Insulin receptor
Gene regulatory protein- binds to DNA to switch genes on or off
o Ex. Transcriptional factors- lactose repressor
WHAT ARE PROTEINS MADE OF
Amino acids
Amino acids are linked together by peptide bonds
There are 20 different amino acids
o The side chain group is the main difference
Protein is made of amino acids linked together into a polypeptide chain
ANATOMY OF AN AMINO ACID
Monomers that form proteins
Formed by a central carbon or alpha carbon attached to an amino group,
carboxyl group, and unique side chain
To form bond between 2 amino acids, one oxygen and 2 hydrogens are
lost from carboxyl group and peptide bond is formed
Peptide bonds are strong covalent bonds
Total of 20 diff amino acids, each w/ varying chemical properties
o Due to varying side chain properties
Nonpolar amino acids will be found inside a protein or hydrophobic
enviro
Polar amino acids will be found exposed to outside of the protein
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POLYPEPTIDE CHAINS
Amino acids contain a central alpha C, an amino group (N-terminus), a
carboxyl group (C-terminus), and an R group (side chain)
Protein is made from a long chain of amino acids, called polypeptide
chain
Amino acids linked to each other through covalent bonding (called
peptide bond)
Peptide bonds formed between backbone of protein, not R groups
Linkages of amino acids to each other formed by condensation reactions,
where a water molecule is expelled in the formation of the peptide bond
linkage
N-terminus and C-terminus provide directionality and polarity
Linkages of amino acids through covalent peptide bonds creates long,
flexible molecules
o This allows them to fold in on themselves, creating conformations
WHAT ALLOWS PROTEINS TO FOLD
Fold into conformation of lowest energy
When it folds in on itself, noncovalent interactions constrain it in certain
ways
Noncovalent bonds are weaker than covalent, so you need multiple of
them to hold protein in tight conformation
3 types of noncovalent bonds help proteins fold
1. Hydrogen bonds
a. When a hydrogen atom is sandwiched between electron-attracting
atoms (oxygen or nitrogen)
2. Electrostatic attractions
a. Between charged groups
3. Van der waals attractions
a. Attractions between 2 atoms at very short distances
Hydrophobic forces help proteins fold into compact conformations
Hydrogen bonds help stabilize a molecule's folded shape
o Can be backbone-backbone, backbone-side chain, or side chain-side
chain
Hydrophobic side chains fold in ways that allows them to interact with
other hydrophobic side chains and stay away from aqueous enviro
surrounding them
o Hydrophilic side chains face outside of protein and interact with the
aqueous enviro
CAN PROTEIN FOLDING BE DISRUPTED/ CAN UNFOLDED PROTEINS
REFOLD AGAIN
Can be unfolded/ denatured by solvents/ factors that disrupt the
noncovalent bonds holding them together
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