Biology 1
Exam 2, Cell Biology
November 2015
Name ___________________
Instructions
Answer all of the following questions. Each response is worth up to 3 points unless otherwise noted.
Bring your exam responses to our next class meeting.
You may use notes, textbooks, the Internet and documentaries.
All responses must be in your own words.
You may consult with fellow classmates, but each student must turn in their own responses written
in their own words; if any responses are found to be identical or very similarly worded, all students
submitting those responses will receive no credit for the entire exam and may be reported to the
Lesley University Academic Integrity Committee.
Plagiarism of any form will also be reported Academic Integrity Committee. 1. Below is a painting by David Goodsell depicting a mycoplasma cell which has a diameter of 0.25µm
(micrometers). The orange strands running throughout the interior is DNA. Ribosomes are shown in
magenta, while phosopholipids are show in light green.
a. Based on the information presented here, is mycoplasma a prokaryote or eukaryote? Give two
reasons why.
b. Mycoplasma can cause illness in humans. If a mycoplasma cell is found by a macrophage (a
type of immune system cell), it will be taken into the macrophage to be digested and rendered
harmless. What is this process is involved in this phenomenon and what steps are involved?
2. Read or listen to the NPR news story “Proposed Treatment To Fix Genetic Diseases Raises Ethical
Issues”: http://www.npr.org/blogs/health/2013/10/09/229167219/proposed-treatment-to-fixgenetic-diseases-raising-ethics-issues
a. Why do mitochondria have their own
DNA?
b. Why can problems with mitochondrial
DNA be lethal, as described in this news
story in the case of Leigh’s Disease?
c. Why does the news story and the
potential treatment it covers discuss the
mother’s eggs so heavily?
d. The protein ATP synthase is essential
for mitochondria to carry out their
function in the cell, and in some
instances of Leigh’s Disease, ATP
synthase is not able to function properly.
Given the location of ATP synthase
(shown in this image from EO Wilson’s
Life on Earth), what kind of protein is it?
In other words, with the terms covered in
chapter 5 of Biology, which one best
applies to ATP synthase? Which parts
(turquoise, green, purple or orange) of
ATP synthase are hydrophilic? (the grey
objects are phospholipids)
e. Why do mitochondria have significant
amounts of membrane within their
interiors, as shown in the image below from the NPR news story?
f. What kind of microscope do you think was used to take this image included with the news story?
Why do you think so?
3. Below are two images of African green monkey cells at 4500x magnification, taken from a journal
article by Manfred Schliwa who examined the effects of fungal toxin cytochalasin D on actin. The cell in
Published January 1, 1982
panel b has been treated with cytochalasin D while the one in panel a was not. Note that the
arrowheads in panel b point out clumps of actin not seen in a.
F I GURE 2 Who l e -moun t prepara t i ons of Tr i ton X-100-ext rac ted ce l l s v i ewed in a h i gh-vo l tage e l ect ron m i croscope . (a) Cont ro l
cel l . Nota.
e presence
of f i l ament
bund lthe
es (st
ress f ibers)
and more oror less
Which panel
depicts
control
experiment
condition?
un i form f iExplain.
l ament ne twork ext end i ng throughout the cel l .
(b) Ce l l t reated w i th 2 pg / m l cytocha l as i n D for 15 m i n . Nume rous dense foc i (ar rowheads) have formed throughout the cy top l asm .
The f i l amentous
tworkofismicroscope
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appear
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ne tworkWhy
. St ressdo
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think
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you know?
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cy toske l e tons
cy tocha
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i n D does
not i ncrease
the degree of How
i n tota l prot e i ns re l eased upon cy tocha l as i n t reat fo l ddoi ncrease
ne t work d i srupt i on , depo l ymer i za t i on seems un l i ke l y . There men t vs . DMSO t rea tment , i f the prot e i n concent ra t i on i n
disrupts
What
cellular
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d. Cytochalasin
fore , the second
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. I f organization
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ved f rom
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erm i ned.
one problem
and / or breakaffected,
i ng o f f i l and
ament swhat
w i th is
subsequent
re l ease would
i nto theyou expect the cell treated with this toxin to have?
buf f er occursExplain.
, i t shou l d be poss i b l e to recover re l eased comMe t abo l i c Inh i b i tors
ponen t s i n the superna t ant . Nega t i ve st a i n i ng of the superna t e
of cytocha l as i n- t rea t ed cy toske l e tons revea l s nume rous f i l aBr i e f pre t rea tment of ce l l s w i th i nh i b i tors o f energy me t abmen t f ragment s , 0 .2-4 par t i n l ength wh i ch , by v i r tue of the i r
o l i sm be fore cy tocha l as i n t rea tment abo l i shes the ma r ked
4. tMeat
hascanbeen
salt cured,
can last
much
longer
meat.
decora
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th S1,
be shown
to be like
F-acjerky
t i n (For
i g .salt
7) . cod,changes
i n ce
l l shape
, d i ssothan
l ut i onuncured
o f f i l ament
cab l esSalt
, and for curingf ragment
is achieved
substantial
amounts
to the
surface
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of meat,
which
then
F i l ament
s may by
a l soapplying
be encount
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t es of of salt
ma t i on
of dense
f i l amentous
aggrega
t es (3,
15, 26)
. To test
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ro
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dehydrates it, giving foods like jerky a dry texture compared to raw and cooked meats. Using concepts
f requency
(dain
t a the
based
on three
i ndependent
i ment s) . of salt
cy tocha
i n-effect.
i nduced d i srupt i on of the three-d i mens i ona l cycovered
reading,
explain
why the exper
application
hasl as
this
Interest i ng l y , superna t es of cytocha l as i n- t rea t ed cy toske l e tons
toske l e ta l f i l ament ne twork , BSC- l ce l l s we re pre t rea t ed w i th
f requent l y show wha t appear to be ne t work f ragment s , i .e .,
o l i gomyc i n , d i n i t ropheno l , 2-deoxyg l ucose , or comb i na t i ons of
shor t ac t i n f i l aments i n end- to-s i de cont ac t w i th another ac t i n
these i nh i b i tors o f energy me t abo l i sm . In these exper i ment s ,
f i l ament (F i g. 7) . I f decora t ed w i th S1, ar rowheads po i nt
gross morpho l og i ca l changes norma l l y occur r i ng i n cy tocha l towards the s i te of cont ac t .
as i n- t reated, un i nh i b i t ed ce l l s are b l ocked. Cy toske l e t a l prep-
5. Listen to this NPR news story on microbial transplants (but not while you’re eating): http://
www.npr.org/sections/health-shots/2013/09/10/216553408/microbe-transplants-treat-somediseases-that-drugs-cant-fix.
a. Why does Dr. Kelly describe the fecal transplant as being like an organ transplant?
b. Are the cells being transplanted eukaryotic or prokaryotic?
c. Why do researchers think this procedure is effective at combatting C. difficile?
You may need to look beyond the information in the news story to answer these questions.
6. Why do plants need both chloroplasts and mitochondria to take care of their energy needs?
7. In the order in which they perform their functions in producing and distributing proteins, fill in the
table below with the components of the endomembrane system.
Organelle
Function
1
2
3
4
8. Watch Dr. Rob Knight’s TED Talk, then answer the following questions. https://www.ted.com/talks/
rob_knight_how_our_microbes_make_us_who_we_are?language=en
a. Consider the image of "microbes" found in the gut shown at 1:15. What kind of microscope
was used to produce this image? Why does it have color?
b. How are microbes in the human microbiome identified and characterized?
c. According to Rob Knight, how many "human" cells make up a typical person's body? How
many "other" cells are there?
d. Are these “other” cells mostly prokaryotic or eukaryotic?
e. What happens to a number of children who are given antibiotics within 6 months of birth?
f. Based on this TED Talk and the microbial transplant NPR story, what benefits or harms do you
think foods and supplements labeled as “probiotic” may have?