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8 Mar 2019

6b. Cells take in materials from the extracellular space by endocytosis, which requires the use of plasma membrane to enclose materials within a vesicle. It would take too much energy for cells to continually synthesize new plasma membrane to replace the membrane that is used to form these vesicles. Yet the plasma membrane of cells that are continually endocytosing material does not become smaller and smaller. So, given your understanding of the endomembrane system, where does the membrane come from? [5 pts]

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Deanna HettingerLv2

9 Mar 2019

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Related questions

1. Name two similarities and two differences between thecellular processes of importing

protein into the ER and importing protein to the nucleus.

2. What proteins are directly involved in the transportation ofcargo in a clathrin-coated

vesicle?

a. Dynamin

b. Adaptins

c. Cargo receptors

d. t SNARES

3. Suppose a cell was treated with colchiine, a drug causingmicrotubule disassembly.

What would happen within the cell? Why?

Suppose there were a genetic defect in the genes that code forkinesins and dyneins.

What would happen within the cell? Why?

4. Which of the following are true about microtubules?

a. They are utilized by the disease causing bacteriaLysteria.

b. Instability in the minus-end of the microtubule is caused bythe hydrolization of GTP.

c. Centrosomes contain binding sites for microtubules composed atype of tubulin ring.

d. Cellular concentrations of tubulin are above the criticalconcentration for plus-end

polymerization.

e. Motor proteins can attach organelles to the microtubules.

5. Indicate which of the following statements are false:

a. Membrane fusion is energetically unfavorable and thusrequires ATP or similar high

energy molecule to occur

b. Clathrin is responsible for capturing specific molecules fortransport in coated vesicle

structures.

c. Receptor proteins that are incorporated into an endosome canbe retrieved back to the

membrane domain it originated from; can return to a new domainof the membrane; or

can enter the lysosome for digestion.

d. Transport vesicles occasionally bud from the trans Golginetwork to fuse with the

plasma membrane in a process called constitutive exocytosis.

e. Most components of the endocytic vesicle membrane eventuallyare returned to the

plasma membrane for reuse.

6. Match the following organelles with their function:

Organelle Bank:

a. Mitochondria

b. Endoplasmic reticulum

c. Nucleus

d. Lysosome

e. Endosome

f. Peroxisome

g. Golgi apparatus

_____ quality control of mRNA

_____ location of oxidative phosphorylation

_____ responsible for detoxifying organic molecules (livercells)

_____ houses and protects genetic material

_____ responsible for modification and sorting of proteins andlipids

_____ location of ATP synthesis

_____ responsible for sorting endocytosed materials

_____ site of degradation and digestion

_____ responsible for oxidizing toxic molecules

_____ location of lipid synthesis

_____ location of hormone synthesis (adrenal cells)

B. Which organelle(s) from the above list communicate(s) withother organelle(s)

through the use of vesicular transport? ________________

C. Which organelle(s) from the above list receive proteins madein the

cytosol?___________________

D. Through which organelle(s) must proteins pass to reach theorganelle(s) which do not

receive proteins made exclusively in thecytosol?______________

E. Entrance into which organelle(s) requires that proteinsunfold and snake through the

membrane? _________________

F. How do organelles maintain their position in the cytosol? Bespecific.

G. Give 2 advantages that eukaryotic cells gain by havingorganelles.

7. Which of the following statements are true regardingactin?

a. They are arranged in a

crimsonwalrus870

Class 6: Viruses (and Cells, continued)

Making connections: viruses and microbes Match the cell biology concept (on page 1) with an important application of that concept (on page 2). Then answer the follow-up questions at the bottom of page 2.

Cell Biology concepts
1. Bacteria that cannot construct new cell wall material become fragile and break down.
2. During influenza infection, the viral enzyme neuraminidase is required to release new viruses from the host cell in which they were made. Once released, the new viruses can infect many additional cells.
3. Thermus aquaticus is a bacterium found in hot springs and can live at temperatures up to ~80Â°C (175Â°F). It has adapted so that its enzymes are most functional at the elevated temperatures, compared with many organismsâ enzymes that function best ~37Â°C (98Â°F).
4. Until the isolation and investigation of retroviruses, scientists thought that RNA could be copied from DNA, but DNA could not be copied from RNA. Research on this class of viruses led to an update to this âCentral Dogmaâ of biology.
5. Some bacteria have adapted, so that the enzymes involved in making cell wall materials have a slightly different shape and can no longer be bound by certain drugs.
6. Rhizobia are bacteria that colonize the roots of certain plants (legumes, including beans and peas). The host plant benefits from the prokaryotesâ ability to âfixâ nitrogen, converting N2 from the atmosphere into a form that is usable by the plant.
7. Many species of bacteria contain the enzyme cellulase. More than 10 billion such bacteria and other symbiotic microbes may be found in a single milliliter of material from inside the digestive system of ruminant mammals.
8. Fungi, including those that cause athleteâs foot, use ergosterol to maintain healthy membranes. Animal cells do not make ergosterol, they use a similar lipid â cholesterol.
9. During retrovirus infection, a DNA copy is made of the virusâs RNA genome. A cut is made in the host cellâs DNA and the DNA copy of the viral genome is pasted into the host chromosome by a viral enzyme called integrase.
10. Prokaryotic cells contain smaller ribosomes (â70Sâ ribosomes) than eukaryotic cells (â80Sâ ribosomes). Both types of ribosomes synthesize proteins, but the macromolecules they use to do it are somewhat different.

2
Applications
_______ Oseltamivir, also called Tamiflu, binds and inhibits the viral protein neuraminidase.
_______ Clotrimazole is a drug that is used to treat certain infections. It interferes with synthesis of ergosterol, a lipid involved in phospholipid membranes.
_______ Penicillin is a drug that interferes with synthesis of peptidoglycans (these are biological molecules that are part protein and part carbohydrate) that are present in certain cell walls.
_______ HIV is often treated with several drugs that inhibit different parts of the viral replicative cycle. Raltegravir is an example of a drug that interferes with the integration of viral genes into the host cellâs chromosome.
_______ Cows, like other vertebrates, lack the ability to breakdown cellulose. Yet they are able to live on a diet of grass and other vegetation high in cellulose.
_______ Enzymes isolated from extremophiles have been very useful in laboratory research. For example, Taq polymerase facilitates PCR, a revolutionary technique for production of DNAs of particular sequences, which requires cycling reactions through high temperatures.
_______ Plants and animals require nitrogen to make biological macromolecules, however theyâre unable to convert atmospheric nitrogen (N2) into a biologically useful form.
_______ Azithromycin is a drug that binds to 70S ribosomes and blocks synthesis of any new proteins.
_______ Methicillin-Resistant Staphylococcus aureus (MRSA) can cause life-threatening infections of the skin and bloodstream. One of the reasons MRSA infections are so serious is that they are resistant to treatment by many antibiotics, including methicillin and penicillin.
_______ The enzyme reverse transcriptase, isolated from retroviruses, is an important tool in molecular biology research. Scientists interested in learning what genes are turned on in particular cells use it to make DNA copies of RNAs they are studying (The DNA copies are useful because they are more stable).

When you have completed the matching activity, answer these follow-up questions:
â¢ What types of infections can be treated with the following drugs?
o Penicillin
o Clotrimazole
o Azithromycin
o Tamiflu
o Raltegravir
â¢ Why are these drugs (above) safe for you to take? That is, why donât they kill your cells?
â¢ Cancer cells are your own human cells that have become deregulated so that they divide and pile up in an uncontrolled way. Many chemotherapy drugs treat cancer by interfering with cell division and other cell processes.
o Why are there so many more side effects for individuals undergoing chemotherapy than for individuals taking antibiotics?