Proteins Flashcards
(22 cards)
Structure of an amino acid
amino group (N) carboxyl group alpha carbon (has R group attached) R group (different in all 20 aa)
3 main types of amino acids
1) amino acid with nonpolar R-groups (hydrophobic)
2) amino acid with polar R groups (hydrophilic)
3) amino acid with charged R groups (hydrophilic)
Where is the peptide bond formed
between the carboxyl group of one amino acid and the amino group (N) of another
What are the 3 forces controlling protein folding
1) hydrophobic interactions - nonpolar aa end up buried inside protein
2) ionic bonds - bonds between positive and negative amino acids
3) Hydrogen bonds - form on N-H on amino group, form in polypeptide backbone
4) Disulfide bridges - forms between cysteines, can help stabilize protein folding shape
Primary protein structure
sequence of amino acids in polypeptide
Secondary protein structure
alpha helix and beta pleated sheet, forms due to hydrogen bonding in polypeptide backbone
Tertiary protein structure
alpha helix and beta pleated sheets interact with each other
it is determined by hydrogen bonds, hydrophobic interations, ionic bonds, and disulfide bridges that form on R groups
Why is it bad that protein folding forces are weak and why is it good
Bad - high temperatures can cause proteins to change shape (high fevers are lethal for this reason)
Good - proteins can easily change shape (alternative conformations) without a lot of energy
3 features that proteins do work in the cell?
1) proteins can bind to other molecules
2) proteins can change shape
3) proteins can catalyze chemical reactions
how do enzymes speed up reactions
enzymes have an active site that binds to substrates and brings the substrates in an arrangement that makes a reaction more likely to occur
functions of microtubule
resists compression forces (pushing on your skin), moves chromosomes in cell division, moves transport vesicles
where are microfilaments
dispersed in cell and there are many of them right under the plasma membrane called cortical microfilaments
function of microfilaments
maintain cell shape (resist pulling) change cell shape, needed for muscle contraction and cell migration
what are microfilaments made of
actin
How do cells crawl
by extension of front edge of migrating cell
lamellipodia
thin region made of microfilaments like a net, the actin microfilaments are assembled at front of lamellipodia and disassembled at the back. the front edge extends to the front to pull forward
Contraction of back end
myosin head catalyzes ATP, binds to microfilaments.
myosin tails: binds to other myosin tails
hinge region: can swivel head back which makes them move
high energy configuration of myosin
hinge is opened, myosin is not contracting (low E config), hinge is shut, myosin is attached to microfilament which slides back and causes contraction
function of non muscle myosin at back
binds to cortical microfilaments at back of cell, when non muscle myosin contracts they slide cortical microfilaments toward each other which causes the membrane to shrink which shortens the cell in that region to help it move forward
how do cancer cells use cell crawling
to migrate from tumor and invade bloodstream. instead of lamellipodia, called invadopodia
Muscle Contraction initiation
neuron sends signal to muscle cell to contract
signal makes SER release Ca2+
Ca2+ goes into cytoplasm and these ions will make muscle contract
function of troponin and tropomyosin
regulate access of myosin to actin microfilaments
