Proteins

Question 1

Structure of an amino acid

Answer 1

amino group (N)
carboxyl group
alpha carbon (has R group attached)
R group (different in all 20 aa)

Question 2

3 main types of amino acids

Answer 2

1) amino acid with nonpolar R-groups (hydrophobic)
2) amino acid with polar R groups (hydrophilic)
3) amino acid with charged R groups (hydrophilic)

Question 3

Where is the peptide bond formed

Answer 3

between the carboxyl group of one amino acid and the amino group (N) of another

Question 4

What are the 3 forces controlling protein folding

Answer 4

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

Question 5

Primary protein structure

Answer 5

sequence of amino acids in polypeptide

Question 6

Secondary protein structure

Answer 6

alpha helix and beta pleated sheet, forms due to hydrogen bonding in polypeptide backbone

Question 7

Tertiary protein structure

Answer 7

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

Question 8

Why is it bad that protein folding forces are weak and why is it good

Answer 8

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

Question 9

3 features that proteins do work in the cell?

Answer 9

1) proteins can bind to other molecules
2) proteins can change shape
3) proteins can catalyze chemical reactions

Question 10

how do enzymes speed up reactions

Answer 10

enzymes have an active site that binds to substrates and brings the substrates in an arrangement that makes a reaction more likely to occur

Question 11

functions of microtubule

Answer 11

resists compression forces (pushing on your skin), moves chromosomes in cell division, moves transport vesicles

Question 12

where are microfilaments

Answer 12

dispersed in cell and there are many of them right under the plasma membrane called cortical microfilaments

Question 13

function of microfilaments

Answer 13

maintain cell shape (resist pulling) change cell shape, needed for muscle contraction and cell migration

Question 14

what are microfilaments made of

Answer 14

actin

Question 15

How do cells crawl

Answer 15

by extension of front edge of migrating cell

Question 16

lamellipodia

Answer 16

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

Question 17

Contraction of back end

Answer 17

myosin head catalyzes ATP, binds to microfilaments.
myosin tails: binds to other myosin tails
hinge region: can swivel head back which makes them move

Question 18

high energy configuration of myosin

Answer 18

hinge is opened, myosin is not contracting (low E config), hinge is shut, myosin is attached to microfilament which slides back and causes contraction

Question 19

function of non muscle myosin at back

Answer 19

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

Question 20

how do cancer cells use cell crawling

Answer 20

to migrate from tumor and invade bloodstream. instead of lamellipodia, called invadopodia

Question 21

Muscle Contraction initiation

Answer 21

neuron sends signal to muscle cell to contract
signal makes SER release Ca2+
Ca2+ goes into cytoplasm and these ions will make muscle contract

Question 22

function of troponin and tropomyosin

Answer 22

regulate access of myosin to actin microfilaments