Protein and Enzymes

Question 1

ΔF508 mutation

Answer 1

• most common mutation in cystic fibrosis
• found on the CFTR gene (cystic fibrosis transmembrane regulator, =250,000 bp and 24 exons)
• deletion mutation of 3 nucleotides -> phenylalanine at position 508 lost
• ΔF508-CFTR stays in ER and is targeted for destruction -> only about 2% of needed protein gets to cell membrane

Question 2

competitive inhibitors

Answer 2

• compete for same site as substrate
• high amounts of substrate will overcome the inhibitor
• Vmax remains the same, but Km is higher

Question 3

non-competitive inhibitors

Answer 3

• bind to a site different from substrate
• changes the substrate binding site
• substrate can not overcome this change
• Vmax is lower, but Km is the same

Question 4

Vmax

Answer 4

maximum velocity of a reaction that can occur in presence of enzyme

Question 5

Km

Answer 5

• michaelis constant
• is the substrate concentration that is found at 1/2Vmax in a michaelis-menten plot
• low Km indicates strong binding affinity

Question 6

lineweaver burke plot

Answer 6

• turns data from michaelis-menten plot from a hyperbolic shape to a straight line
• x-axis is 1/S and y-axis is 1/V
• the line crosses the y-axis at 1/Vmax
• the line crosses the x-axis at -1/Km

Question 7

variable changes in competitive inhibition

Answer 7

• Vmax remains the same

* Km increases

Question 8

variable changes in non-competitive inhibition

Answer 8

• Vmax decreases

* Km remains the same

Question 9

enzymes

Answer 9

catalytic proteins

Question 10

defensive proteins

Answer 10

e.g. antibodies

Question 11

hormonal and regulatory proteins

Answer 11

control physiological processes

Question 12

receptor proteins

Answer 12

receive and respond to molecular signals

Question 13

storage proteins

Answer 13

store amino acids

Question 14

structural proteins

Answer 14

physical stability and movement

Question 15

transport proteins

Answer 15

carry substances (e.g. hemoglobin)

Question 16

genetic regulatory proteins

Answer 16

regulate when, how, and to what extent a gene is expressed

Question 17

secretory proteins are synthesized by

Answer 17

ribosomes bound to the ER (constitutive pathway)

Question 18

cytoplasmic proteins are synthesized by

Answer 18

free ribosomes in cytoplasm

Question 19

golgi apparatus

Answer 19

distribution center for proteins and lipids from the ER to vesicles and plasma membrane

Question 20

endosome

Answer 20

• sorting centers for material from outside the cell or golgi
• sends it to lysosomes for destruction, or back to the membrane/golgi for further use

Question 21

proteasome

Answer 21

barrel-shaped protein complex that degrades damaged or ubiquitin-tagged proteins

Question 22

protein folding is

hint when does it happen

Answer 22

co-translational

Question 23

dominant negative effect

Answer 23

• protein subunits A and B need to form a complex to become active
• if subunit A is misfolded and inactive, but can still join subunit B, then the entire complex becomes inactive

Question 24

exocytic transport system

Answer 24

• ER -> vesicle -> golgi apparatus -> vesicle -> plasma membrane
• secretory proteins
• membrane proteins

Question 25

COP II

Answer 25

* coatamer protein II * expressed on vesicle released from RER that will target the cys golgi (closest to ER) * KEY: ER -> cys golgi

Question 26

COP I

Answer 26

* coatamer protein I * retrograde transport * if components belonging in ER (ie chaperones) make it to the golgi, the vesicle gets tagged with COP I to go back to ER * Key: cys golgi -> ER

Question 27

core glycosylation happens when

Answer 27

co-translational

Question 28

core glycosylation of protein

Answer 28

* simple high mannose added * N-glycosylation (n-linked) * done in ER

Question 29

complex glycosylation of protein

Answer 29

* done in golgi | * O-glycosylation

Question 30

constitutive pathway

Answer 30

the default pathway = exocytic pathway | others need regulated pathway, which requires signals

Question 31

CFTR

Answer 31

* cystic fibrosis transmembrane regulator * allows for Cl- to exit cells * important for maintenance of gradients

Question 32

which amino acid would you not find in an α-helical domain

Answer 32

proline (helix breaker)

Question 33

sigmoidal curve indicative of

Answer 33

cooperative binding (i.e hemoglobin)

Question 34

michaelis-menten kinetics

Answer 34

only applies to single subunit enzymes (rare in human body)