CELL BIOLOGY 020.306 MIDTERM STUDY
GUIDE 2024
1. Nucleolus. 11 points.
A. Name (or describe) two specific types of proteins or nucleic acids that would be likely to be
found in a nucleolus (a subcompartment of the nucleus). 4 nucleus
1: rRNA, rDNA, ribosomal proteins, snoRNAs, histones, RNA Pol I (not mRNAs, ribosomal
protein genes, carbohydrates, or lipids)
2:
-1 pt max for “DNA” with no further explanation
B. Do you think there are phospholipid molecules that localize to a nucleolus? 3 nucleus
Circle one: YES NO
Explain: phospholipids are found in membranes (lipid bilayers) and the nucleolus is not
membrane-bound
C. The nucleolus can be identified in many types of microscopy as a dark region of the nucleus.
Select a type of microscopy below and explain why the nucleolus appears darker than the
surrounding region. Your answer should include both characteristics of the nucleolus and the
type of microscopy. 4 nucleus/methods 1
3
Select one type of microscopy:
phase contrast transmission electron fluorescence microscopy using a DAPI stain for DNA
The signal detected is light (phase contrast) or electrons (TEM) that pass through the sample
and the material in the nucleolus is dense because it contains a lot of molecules and therefore
prevents the light or electrons from passing through. For DAPI, the signal is the emission
wavelength generated by the fluorescent dye DAPI which binds DNA. There is less DNA and
therefore less DAPI in the nucleolus than the surrounding area.
2. Glycoproteins. 18 points
A. Name one extracellular matrix glycoprotein discussed in this course and briefly describe the
function of that protein. ECM 3
Name: laminin, fibronectin, elastin, collagen
Briefly describe function:
, 2. continued
Extracellular matrix glycoproteins are synthesized at the ER by co-translational translocation.
B. Which of the following is a characteristic of all ER signal sequences that is most important for
initiating the process of co-translational translocation (instead of translation in the cytosol)?
Select the best answer. Membranes 3
a. binding to the ribosome
b. binding to the channel of the translocon
d. binding to signal recognition particle (SRP)
e. binding to the SRP receptor
f. binding to the mRNA
C. Which of the five different proteins
diagrammed on the right (labeled 1-5).
would you predict might have an N-
terminal ER signal sequence? 3
membranes
Circle all that apply:
1 2 3 4 5
Consider a glycoprotein that is part of the extracellular matrix (not a transmembrane domain
protein) and is synthesized by co-translational translocation.
D. What would be the size of this glycoprotein in a cell that did not have functional signal
peptidase? 2 membranes
a. same length as in the presence of signal peptidase
b. longer than in the presence of signal peptidase
c. shorter than in the presence of signal peptidase
E. Using the diagrams of a microsomes below, draw a diagram of the protein after completion
of the co-translational translocation process in a normal microsome (left) and in a microsome
that is missing signal peptidase (right). 3 membranes
Normal microsome Microsome lacking signal peptidase
1 2
GUIDE 2024
1. Nucleolus. 11 points.
A. Name (or describe) two specific types of proteins or nucleic acids that would be likely to be
found in a nucleolus (a subcompartment of the nucleus). 4 nucleus
1: rRNA, rDNA, ribosomal proteins, snoRNAs, histones, RNA Pol I (not mRNAs, ribosomal
protein genes, carbohydrates, or lipids)
2:
-1 pt max for “DNA” with no further explanation
B. Do you think there are phospholipid molecules that localize to a nucleolus? 3 nucleus
Circle one: YES NO
Explain: phospholipids are found in membranes (lipid bilayers) and the nucleolus is not
membrane-bound
C. The nucleolus can be identified in many types of microscopy as a dark region of the nucleus.
Select a type of microscopy below and explain why the nucleolus appears darker than the
surrounding region. Your answer should include both characteristics of the nucleolus and the
type of microscopy. 4 nucleus/methods 1
3
Select one type of microscopy:
phase contrast transmission electron fluorescence microscopy using a DAPI stain for DNA
The signal detected is light (phase contrast) or electrons (TEM) that pass through the sample
and the material in the nucleolus is dense because it contains a lot of molecules and therefore
prevents the light or electrons from passing through. For DAPI, the signal is the emission
wavelength generated by the fluorescent dye DAPI which binds DNA. There is less DNA and
therefore less DAPI in the nucleolus than the surrounding area.
2. Glycoproteins. 18 points
A. Name one extracellular matrix glycoprotein discussed in this course and briefly describe the
function of that protein. ECM 3
Name: laminin, fibronectin, elastin, collagen
Briefly describe function:
, 2. continued
Extracellular matrix glycoproteins are synthesized at the ER by co-translational translocation.
B. Which of the following is a characteristic of all ER signal sequences that is most important for
initiating the process of co-translational translocation (instead of translation in the cytosol)?
Select the best answer. Membranes 3
a. binding to the ribosome
b. binding to the channel of the translocon
d. binding to signal recognition particle (SRP)
e. binding to the SRP receptor
f. binding to the mRNA
C. Which of the five different proteins
diagrammed on the right (labeled 1-5).
would you predict might have an N-
terminal ER signal sequence? 3
membranes
Circle all that apply:
1 2 3 4 5
Consider a glycoprotein that is part of the extracellular matrix (not a transmembrane domain
protein) and is synthesized by co-translational translocation.
D. What would be the size of this glycoprotein in a cell that did not have functional signal
peptidase? 2 membranes
a. same length as in the presence of signal peptidase
b. longer than in the presence of signal peptidase
c. shorter than in the presence of signal peptidase
E. Using the diagrams of a microsomes below, draw a diagram of the protein after completion
of the co-translational translocation process in a normal microsome (left) and in a microsome
that is missing signal peptidase (right). 3 membranes
Normal microsome Microsome lacking signal peptidase
1 2
