• Question 2. Short Answer
• Explain in one or 2 sentences why plants
need to have mitochondria in every cell,
even when the sun is shining.
• There are no motor proteins that move on
intermediate filaments. Can you suggest a
reason based on the structure of the
intermediate filaments? What does this tell
you about motor proteins? Question 3. Fill in the blanks:
• A small GTP-binding
the neck of each
coated vesicle and
helps in pinching off
the vesicle from the
• __________ is the
motor protein that
towards the plus end
of the microtubule. Question 4. Design an experiment using appropriate
experimental technique(s) to study the kinesin-assisted
transport of macromolecules.
1. Immunofluorescence microscopy: Primary antibodies bind to
cytoskeletal proteins. Secondary antibodies labeled with a
fluorescent tag bind to the primary antibody. Cytoskeletal proteins
glow in the fluorescence microscope.
2. Fluorescence techniques: Fluorescent versions of cytoskeletal
proteins are made and introduced into living cells. Fluorescence
microscopy and video cameras are used to view the proteins as
they function in the cell.
3. Computer-enhanced digital videomicroscopy: High resolution
images from a video camera attached to a microscope are
computer processed to increase contrast and remove background
features that obscure the image.
4. In vitro and in vivo studies [Figs. 17-19 to 17-22, pp 585-88] Question 5. Three phospholipids X, Y and Z are distributed in the
plasma membrane as shown. For which of these phospholipids does a
flippase probably exist?
a. X only
b. Z only
c. X and Y
d. Y and Z
e. X and Z
Explain your answer
Three phospholipids X, Y and Z are distributed in
the plasma membrane as shown. For which of
these phospholipids does a flippase probably
C = X and Y
Explain your answer briefly.
Lipids are inserted into the membrane on the
lumen face of the SER (which corresponds
to cytosolic side of the plasma membrane).
Therefore both X and Y would need
flippases to move to the external leaflet.
Must know that flipping can’t occur
spontaneously and that all lipids are
inserted into the same leaflet. Must mention
SER. Question 6. Based on your understanding of cell structure and
function, please state if the following statements are TRUE or
FALSE and provide an explanation for your choice.
• a) Membrane-bound and free ribosomes, are
structurally and functionally identical and differ
only in the proteins that they happen to be
making at a particular time.
• b) All of the glycoproteins in the intracellular
membranes have their oligosaccharide chains
facing the lumen, whereas those in the plasma
membrane have their oligosaccharide chains
facing the outside of the cell
• c) The pH of the chloroplast thylakoid space (or
lumen) increases in the light. a) Membrane-bound and free ribosomes, are structurally
and functionally identical and differ only in the proteins
that they happen to be making at a particular time.
TRUE. Cytosolic ribosomes are translating proteins with no
sorting signals/ proteins destined to remain in the
cytoplasm. Ribosomes of the RER are translating
proteins with ER signal sequence, i.e. the subsequent
events leading to attachment of ribosomes to the ER
membrane are a result of the interaction of the signal
peptide amino acid sequence with the signal recognition
particle (SRP) and the SRP receptor in the ER
membrane. b) All of the glycoproteins in the intracellular membranes
have their oligosaccharide chains facing the lumen,
whereas those in the plasma membrane have their
oligosaccharide chains facing the outside of the cell
TRUE. For glycoproteins as the oligosaccharide
chains are transferred onto the protein in the ER
lumen, then further modified in the Golgi. When
those proteins are secreted via exocytosis, the
oligosaccharide chains are facing the
extracellular space or comment on extracellular
space being topologically equivalent to
endomembrane lumen. c) The pH of the chloroplast thylakoid
space (or lumen) increases in the light.
FALSE. The pH of the thylakoid space
decreases due to accumulation of protons
driven into the space by the flow of
electrons along the photosynthetic
electron transport chain. QUESTION 7:
A typical time course for polymerization of
purified tubulin to form microtubules is
Explain the different
parts of the curve
labeled A, B and C.
How would the curve change if centrosomes
were added at the onset? ANSWER:
A typical time cou