BIOL 1090 Lecture Notes - Lecture 3: Hydrophile, Glycolipid, Lipid Bilayer

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11 Feb 2015

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Influenza: non-lytic or integrative: viral dna is inserted in host genome. Dna=provirus; viral progeny bud at cell surface; cell can survive, often with impaired function (ex. Function of biological membranes: cell boundary, define/enclose compartments, control movement of material into/out of cell, allow response to external stimuli, enable interactions between cells, provide scaffold for biochemical activities. Plasma membrane: trilaminar (means the membrane is 3 layers thick, 6nm thick) Structure of biological membranes: fluid-mosaic model, bilayer of amphipathic (having both hydrophobic and hydrophilic regions) lipids, proteins: The mitochondria has an inner membrane that contains a very high concentration of protein: ex. The myelin sheath of a neuron contains very low amounts of protein. Myelin sheath consists of layers of plasma membrane, forming insulation around the nerve axon. This is important because the axon is responsible for electrical signals and insulation is key for not short circuiting .

Related Questions

1. A mutation in the gene encoding the integrase enzyme rendersthe protein non-functional. How would the affect the HIV infectioncycle?

Formation of the provirus would be stopped.
Reverse transcription would no longer be possible.
The gp120 glycoprotein would no longer be able to bind to the CCR5receptor.
Cutting and assembling the capsid would be halted.

2. If the viral gene is AUGCCCAGG and the mRNA used to make theviral protein is UACGGGUCC, then the virus is a :

Negative strand RNA virus
Double stranded DNA virus
Retrovirus
Positive strand RNA virus

3. Would treating prions with enzymes that digest nucleotides bean effective neutralization method?

No, prions lack amino acids.
Yes, prion nucleic acids would be susceptible to enzymaticdigestion.
No, prions lack phosphodiester bonds and would not be subject todigestion by these types of enzymes.
Yes, the bonds between the amino acids would be hydrolyzed.

4. Most Americans born before 1970 have a permanent scar ontheir shoulders from the smallpox vaccine. Why don't youngerAmericans have one?

Smallpox has been eradicated by a worldwide vaccinationprogram.
Smallpox is no longer lethal.
A safer less damaging vaccine was developed in the early1970's.
The vaccine is no longer effective due to antigenic shift.

5. What kind of pathogen would retain its ability to causeinfections after being treated with powerful proteolytic chemicalsthat would destroy all proteinaceous material?

A virus
A bacterium
A prion
A fungus
A viroid

6. Select all of the false statements concerning AIDS.

AIDS kills the patient.
Patients die as a result of opportunisticinfections.
AIDS shuts down the immune system.
HIV therapy (HAART) can clear the virus from thebloodstream.

HIV therapy (HAART) can clear the virus from the patient'sbody.

7. Why do viruses only infect specific types of cells?

Viruses only attack epithelial cells, such as the cells liningthe lungs.
If a host cell is weakened, viruses have an easier time infectingit.
The initial choice is random but once a cell type is chosen itbecomes the preferred host.
The host cells have the correct surface receptor that the virus canfit into.
Viruses infect the first cells they encounter.

8. Nucleotide analogs are a class of drugs that are highlyeffective against many types of viruses. They work by halting thereplication of viral genes. They are equally effective at stoppingthe spread of prion diseases.

True
False

9. An experimental chemical has been shown to selectively cleavephosphodiester bonds. How would the affect a virus?

Dissociate the envelope
Fragment the genome
Hydrolyze the protein coating
Alter the host binding site
Digest the capsid

10. HIV uses cell surface receptors to enter host cells. Whydoes switching from a CCR5 co-receptor to a CXCR4 co-receptoreventually shut down the immune system?

Macrophages have CCR5 co-receptors.
T-helper cells have CXCR4 co-receptors.
T-helper cells are not involved in coordinating immuneresponses.
Only macrophages are killed by HIV.

erinhornet258

Question 1 10 pts

What three kinds of cells are infected by HIV?

macrophages, T-Helper cells and dendritic cells

B-cells, skin cells and T-helper cells

B-cells, T-Helper cells and T-killer cells

macrophages, dendritic cells and cytotoxic T-cells

Question 2 10 pts

Sometimes an HIV infected cell is not killed immediately after infection, but lives on, and continues to be a source of the infection for the lifetime of the patient. What is the mechanism that allows the HIV virus to remain in the cell, to get passed down to all descendants of that cell, and to retain the ability to be reactivated for the lifetime of the patient?

Question 3 10 pts

List the three processes that viruses are dependent on their host cells for.

Question 4 10 pts

What does the ELISA test for HIV infection measure?

HIV-specific antibodies

Hepatitis B-specific antibodies

circulating HIV particles

HIV-specific DNA

Question 5 10 pts

What is the cell surface receptor for HIV?

CD4

CD8

MHCII

HIV

Question 6 10 pts

What is the likely origin of HIV-1?

infection of humans by a simian virus native to the chimpanzee

germ warfare research by the CIA

sexually transmitted to humans through relations with sheep

a new human-chimpanzee hybrid virus accidentally made in a laboratory with recombinant DNA

Question 7 10 pts

How does AZT block the production of infectious virus?

It acts as a substitute for a DNA nucleotide that can only be inserted by the viral reverse transcriptase. The presence of the AZT in the DNA aborts the production of new viral DNA.

It directly blocks the reverse transcriptase.

It blocks the protease that cuts apart the three viral proteins, which is a necessary step during viral synthesis.

It blocks the adsorption of the virus to the CXCR4 and CCR5 receptors on the T-cell surface.

Question 8 10 pts

How do protease inhibitors work?

It blocks the protease that cuts apart the three viral proteins, which is a necessary step during viral synthesis.

It directly blocks the reverse transcriptase.

It acts as a substitute for a DNA nucleotide that can only be inserted by the viral reverse transcriptase. The presence of the AZT in the DNA aborts the production of new viral DNA.

It blocks the adsorption of the virus to the CXCR4 and CCR5 receptors on the T-cell surface.

Question 9 10 pts

What are the 2 most common causes of a false negative result in the HIV test?

Questions 10-13

The next set of 4 questions deal with the possible ways that a virus, not necessarily the HIV, can enter the body. Answer TRUE or FALSE to each question.

Question 10 2.5 pts

Some viruses can enter the body through breaks in the skin.

True

False

Question 11 2.5 pts

Some viruses can enter the body through the anal/genital tract.

True

False

Question 12 2.5 pts

Some viruses can enter the body through the oral cavity and the digestive tract.

True

False

Question 13 2.5 pts

Some viruses can enter the body through inhalation via the respiratory tract.

True

False

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?

BIOL 1090 Lecture Notes - Lecture 3: Hydrophile, Glycolipid, Lipid Bilayer

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