BIOL 540 EXAM #2 QUESTIONS WITH CORRECT ANSWERS!!

BIOL 540 EXAM #2 QUESTIONS WITH
CORRECT ANSWERS!!
What are the 2 levels of metabolic control? Which has the fastest effects? -
ANSWER1. Trancriptional
2. Translational - fastest

Which of the following is correct?
a) proteins operate in a graded fashion
b) proteins are either on or off - ANSWERB

What are the 2 roles of tRNA - ANSWER1. match correct aa with correct tRNA
2. codon-anticodon interaction

Describe the steps involved in tRNA activation. - ANSWER1. Amino acid and
enzyme form complex; energy provided from ATP hydrolysis and AMP attaching to
complex

2. tRNA binds amino acid and throws off enzyme and AMP

What kind of tRNA mismatches do not have a large effect? - ANSWERsubstitution of
a nonpolar aa for another nonpolar aa

A ribosome is structurally described as a _____________ _________. -
ANSWERribonucleoprotein complex

How many components are there in a ribosome? What are the subunits? -
ANSWER1. Large subunit
2. Small subunit

Where are ribosomes found? - ANSWERcytosol, chloroplast, mitochondria

Describe the process of protein synthesis initiation. - ANSWER1. Start codon (AUG)
is recognized.

2. eIF1 stabilizes initiator methionine (formyl-Met) and blocks A site --> eIF2-GTP
brings in initiator methionine --> eIF3 inhibits large subunit binding until eIF2-GTP is
hydrolyzed

3. eIF4A removes secondary structure --> eIF4E binds to 7' methylguanosine cap -->
eIF4G binds eIF4E and poly (A) binding protein to signal "good" --> eIF5 facilitates
large and small subunit association

Describe the process of elongation in protein synthesis. - ANSWEREF1⍺-GTP brings
tRNA into A site and if correct will hydrolyze GTP and leave tRNA at A site -->
peptidyl transferase catalyzes formation of peptide bond --> GTP on EF2-GTP
hydrolyzed to correct site

, What are the STOP codons? - ANSWERUGA, UAG, UAA

What are the two releasing factors in protein synthesis? - ANSWEReRF1: ???
eRF: ???

What is a translocon? - ANSWERcomplex of proteins associated with translocating
peptides across a membrane

Distinguish between cotranslational and post-translational protein targeting -
ANSWERCotranslational = translocon

Post-Translational
= Nuclear localization signal
= Mitochondrial TIM/TIM (unfolds protein and threads it through)
= Chloroplast TIC/TOC
= Peroxisome

________________________ recognizes that protein is at correct location. -
ANSWERsignal peptidase

What are the 2 roles of glycosylation? - ANSWER1. targeting/localization of glycosyl
groups
2. protection of proteins from acidic degradation

What does glycosyltransferase do? - ANSWERtransfers glycosyl group from
nucleoside disphophsate to protein

Distinguish between N-linked and O-linked glycosylation linkages. - ANSWERN-
linked = linked to nitrogen
- begins in ER and finishes in Golgi
- 2+9+3 structure
- requires Asn-X-Thr/Ser sequence
- two classes = high mannose, complex protein

O-linked = linked to oxygen
- occurs only in Golgi (no ER involvement)
- sugars bond to Ser or Thr

Describe each of the following reaction orders:
a) first order
b) second order
c) pseudo-first order
d) zero order - ANSWERa) First Order = unimolecular
b) Second Order = bimolecular
c) Pseudo-First Order = one substrate is in such excess that it appears first order
d) Zero Order = one reagent in such excess that enzyme is never unoccupied

What are the 2 things that enzyme velocity depends on? - ANSWER1. amount of
substrate