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matrenka [14]
3 years ago
7

Why have scientists developed vaccines?

Biology
2 answers:
GuDViN [60]3 years ago
7 0

Answer:

to treat illnesses (number 3)

Explanation:

:3

Dennis_Churaev [7]3 years ago
3 0

Answer:

  • scientists have developed vaccines to prevent diseases
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Approximately how far apart were north america and europe 200,000 years ago
Ne4ueva [31]

The correct answer is - 1,180 km.

North America and Europe move away from one another, though on the other end of the plates, the Eurasian and the North American plates are actually merging. Since the rate of moving away is 2 cm per year, and the current distance is 1,184 km between North America and Europe, the distance between them 200,000 years ago was 1,180 km.

To get to the result we only need to multiply the number of years with the annual movement

2 x 200,000 = 400,000

Then divide the result with 100,000, as that is how much cm are in one km

400,000 / 100,000 = 4

And we get 4 km, in this case 4 km less, thus the distance between the two, 200,000 years ago, was 1,180 km.

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3 years ago
All the following are part of photosynthesis except:
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I’m not sure I think it’s D.) Hope I could help :)))



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3 years ago
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In which city is the Gujarat High Court situated?<br><br>​
yan [13]
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Ahmedabad, India
6 0
2 years ago
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Why is it important to test both the left and right side during an mmt?
Debora [2.8K]
MMT stands for Manual Muscle Testing. In this test, the muscle disorders are examined such as muscle weakness or paralysis. It is a part of physical therapy where it is important to test both the left and right side to assess the physical strength of the muscles of a patient.
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3 years ago
Are viral infections curable? Why or why not?
Anna11 [10]

Answer:

no.

Explanation:

Viruses, on the other hand, are not cellular. We can't kill them simply by disrupting their cells. They are infective nucleic acids which cannot replicate outside of living cells. They must invade a human cell to reproduce, because they cannot produce energy or synthesize molecules on their own. Some viruses replicate inside human cells and then bud off from the human cell inside an "envelope" made from the human cell's own membrane, which helps them evade the immune system on their way to infecting another human cell. Many viruses are protected by protein capsids, which are extremely protective--unlike a bacterial cell wall or membrane, the virus doesn't have to be alive inside the capsid or exchange nutrients and waste with the environment across the capsid; the capsid is merely there to protect the nucleic acid of the virus.

Viruses need to match some sort of receptor in order to gain entry into human cells, and in some viruses, this receptor is one of the few good targets for drug therapy; however, unlike antibacterials, the drug will only work for that particular virus/receptor, because each virus uses a different receptor.

Viruses spend time inside human cells, which protects any outer antigens from some of the aspects of the immune system. There are times when viruses are especially vulnerable during replication, but there are reasons they are harder than bacteria to target with these antireplication drugs: 1) unlike for most bacteria, the drugs need to be small enough to enter the human cell where the virus is replicating, 2) unlike for most bacteria, the drugs can't simply target a protein shared by most viruses; furthermore, many viruses hijack human proteins which cannot be targeted. Overall, there are comparatively few antiviral drugs compared to antibiotics because of the huge difficulty in obtaining selective toxicity. And 3) most drugs available target a certain step of viral replication for a certain family of viruses; however, by the time the patient shows symptoms, the virus has already created countless copies of itself or become latent in human cells, and at that point it is too late for most of the antiviral drugs to be super helpful since they target the replication itself. Even when a good antiviral drug is developed, most of them work only against a single species (or at best, a family) of viruses, which is not the case for most antibiotics.

Many viruses don't spread in ways where they can easily targeted (Polio moves from the GI tract to lymph nodes and then to the blood stream on it's way to the spinal cord to cause paralysis; it is vulnerable to the immune system in vaccinated individuals while it is forced to travel in the blood. In contrast, some viruses like rabies, herpes, and varicella-zoster spread through neurons in order to evade the immune system. Other viruses form syncytia because they travel directly from cell to cell). Also remember that some viruses integrate themselves into human DNA and remain latent for long periods of time, which prevents them from being cleared by drugs or the immune system. The human immune system does have its ways of dealing with viruses, which I can get into in greater detail in another post. For certain viruses, the only way we have to treat them is to use interferons to ramp up the immune system (a very unpleasant therapy which must often be maintained for very long periods of time).

One of the reasons that vaccines for some viruses are not effective is that oftentimes, a live (attenuated) vaccine cannot be made for those certain viruses since the reversion mutation rate is too high to provide an acceptable risk; for many viruses, only killed strains can be used, if at all. Without a live attenuated virus strain multiplying inside cells, certain critical aspects of the immune system are not activated against these certain viruses. In cases where killed viruses are able to be used as vaccines, the protection is lesser (for instance, no type-switching to IgA antibodies which would be more effective than IgM) and shorter-lived.

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3 years ago
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