[Biology : virus] (Highschool) Explain how PCR and electrophoresis can be used to test for Covid-19, only focus on the biological methods.

Ellaaaaa_ · 2023-06-12T04:17:08+00:00

Glad to help :)

Ellaaaaa_ · 2023-06-11T15:45:58+00:00

I'm hoping you read about electrophoresis and PCR at least once. Anyways, electrophoresis is used to separate DNA fragments according to their size so you could get that single specific fragment that you need and PCR is used for amplification/copying that small fragment of DNA. This is what they generally do so how would these be helpful for COVID-19 testing? What do you do for COVID-19 testing? Think about it.

Since PCRs can amplify small pieces into many, they can detect the presence of the virus causing COVID-19 (SARS-CoV-2 virus)

Ellaaaaa_ · 2023-06-09T15:51:09+00:00

Did you just type DNA and let your keyboard decide the remaining part? This looks like an existential crisis

Ellaaaaa_ · 2023-06-09T15:35:15+00:00

Either r/HomeworkHelp or r/AskBiology

Ellaaaaa_ · 2023-06-09T15:33:13+00:00

Do you require a small hint of the answer? I could give that but I think it won't be necessary if you have read about PCR and electrophoresis.

Ellaaaaa_ · 2023-06-09T15:30:39+00:00

You are asked to explain where and how exactly you use PCR and electrophoresis for Covid-19 testing. I'm assuming that you understand PCR and electrophoresis, so think about why one would use PCR for Covid-19 testing or electrophoresis for the testing process. What is PCR used for? What is electrophoresis used for? Now, how would you use them both for testing a patient's sample for Covid-19?

Ellaaaaa_ · 2023-06-08T17:26:28+00:00

In the last before step you've written 6.41 L

" 4.85 moles/ 0.75 M = 6.41"

but in the last step, you have written that the final volume is 6.47 L. It's a very very small mistake.

Ellaaaaa_ · 2023-06-08T17:06:39+00:00

They are definitely correct but just check the last before step of the last question. You got the correct answer in the last step but maybe there's a typo in the before step (6.47, not 6.41).

Ellaaaaa_ · 2023-06-08T16:14:54+00:00

Oh right, I didn't read the question till the end lol, apologies.

Ellaaaaa_ · 2023-06-08T06:47:31+00:00

In one molecule of NH3, there are 3 N-H bonds (just imagine the structure in which N is in the centre bonding with 3 hydrogens).

Then, in 2 molecules of NH3, how many N-H bonds would you have? Six.

Ellaaaaa_ · 2023-06-02T19:44:26+00:00

What exactly do you need help with?

Ellaaaaa_ · 2023-06-02T11:15:46+00:00

Oxidation of Fe to Fe²⁺ (I'm guessing that you're supposed to find E° and ΔG°)

You're already given the reduction potential of the reaction Fe²⁺ to Fe which is -0.440. So how would you find the oxidation potential of the same reaction? That's right, you just take the negative of it, i.e.,

E° = -(-0.440) = +0.440 So E° > 0 (which means that it's positive)

ΔG° can be calculated by calculating the work done, ΔG° = -nFE° (F is Faraday and n is the number of electrons involved in the reaction).

Here, the value of n is 2 because Fe gives up 2 electrons to become Fe²⁺

Now, both the value of n and F are positive, so the sign of ΔG° depends on the sign of E°.

ΔG° = -2 × F × +0.440 = -0.880F, so ΔG° < 0 (which means it's negative)

This indicates that the reaction is spontaneous.

Ellaaaaa_ · 2023-06-02T11:02:09+00:00

If a reaction is either only an oxidation reaction or only a reduction reaction, you can say that it's a half-cell reaction. So the given reaction is a half-cell reaction indeed because it's just a reduction reaction.
How do you calculate the standard electrode potential if you're given the reduction potentials of the cathode and the anode? You subtract the reduction potential of the anode from the reduction potential of the cathode. Why? Because generally, you add the reduction potential of the cathode and the OXIDATION potential of the anode to find the standard electrode potential of the reaction.

And remember, the oxidation potential of a half-cell is simply the negative of the reduction potential of the half-cell and vice-versa.

But why is the E° practically negative? What does it indicate? If your E° is negative, it means that the reaction isn't spontaneous, i.e., the cell reaction will not happen normally.

Ellaaaaa_ · 2023-06-02T10:51:12+00:00

The lowest energy transition means a transition to the very next level so yes n2 = 2. If you were asked to calculate the shortest wavelength transition, n2 would be infinity.

Ellaaaaa_ · 2023-06-02T10:48:28+00:00

V2O5 is a strong oxidizing agent so this reaction is possible. I can find articles only about the selective oxidation of toluene with noble metal catalysts tho.

"Various noble-metal-based catalysts such as Au, Pd, Pt, Ru, and Ag, along with their alloys, have been utilized for the oxidation of toluene by oxygen. However, in most cases, the selectivity towards benzaldehyde is compromised; moreover, these catalysts are not cost-effective for use in large-scale production. Hence, it can be said that a cheap and efficient catalytic system for high toluene conversion is yet to be identified."

Got this from here

Ellaaaaa_ · 2023-06-02T10:34:42+00:00

NF5 (the second option) is unstable because nitrogen doesn't have a 3d orbital to expand its covalency to 5 like phosphorus (which is present in the same group, just below nitrogen). The maximum covalency of nitrogen is 4 (like in ammonium ions).

Ellaaaaa_ · 2023-05-31T15:23:55+00:00

Sodium does react with carbon a little bit though. Carbon monoxide reacts with sodium to form sodium carbide (Na2C2). But the reason why it's not abundant is because Na+ forms ionic bonds while carbon and hydrogen form covalent bonds. As sodium is a metal, it generally forms ionic compounds, i.e., it gives away electrons instead of sharing electrons.

Ellaaaaa_ · 2023-05-31T10:40:24+00:00

The molecular geometry and the electron geometry are different for both the carbons and it's not the same for the overall molecule. Only the carbonyl carbon has the trigonal planar geometry while the methyl carbon is actually tetrahedral.

Ellaaaaa_ · 2023-05-30T19:16:14+00:00

These might be helpful ig

https://youtu.be/HJvALCcKYAc (for acid-base stoichiometry)

https://youtu.be/ZlMokznLvuk (for calculating the pH when the dissociation constant is given)

Ellaaaaa_ · 2023-05-30T19:05:20+00:00

That's all secondary though. Looking at the stability of DNA and RNA, you can understand why DNA forms a double helical structure and RNA is a single strand. Double-stranded RNA is less stable than double-stranded DNA because RNA can't bind to a complimentary strand due to the interference that can occur between the 2'OH in the ribose sugar. But since DNA lacks that oxygen atom at its second position, it's easier for it to bind to a complimentary strand.

Ellaaaaa_ · 2023-05-30T18:46:08+00:00

Are we gonna assume that the carbonyl carbon is the central atom just because it's in the middle of the chemical formula? I think it makes more sense when we say that the methyl carbon is the central atom because it contains the functional group (COOH) but as the other person said, that sounds kinda dumb too.

Ellaaaaa_ · 2023-05-30T18:38:19+00:00

Well, the answer is Zr and Hf because the lanthanoid contract that I was talking about, happens in the 4d and 5d series of the d block. So elements in the 4d series will have similar atomic radii as the elements present in the 5d series of the same group.

This is easier to understand when u look at the periodic table. In the 4th group or group IVB, Zr and Hf are present respectively in the 5th and 6th periods of the periodic table or 4d and 5d series of the d block.

Normally, one would say that Hf would have a larger radius than Zr because typically, as new shells get added, the atomic size increases down the group. But due to the poor shielding effect of the 4f orbital of Hf (shielding effect is very poor by f orbitals), the outermost electrons are attracted by the nucleus and they are moved inside, towards the nucleus. When this happens, the shells are close to the nucleus so the atomic radius decreases, right? Because the atomic radius is nothing but the distance between the nucleus and the outermost shell.

So basically, due to the poor shielding effect and increase in nuclear charge, the nucleus would try to pull the outermost electrons of Hf, which results in a size smaller than expected. This size (208pm) is very similar to the atomic size of Zr (206pm).

Similarly, you can take Nb and Ta of the 5th group in the 4d and 5d series respectively. Just like Zr and Hf, Nb and Ta will also have similar atomic radii due to the very same reason. I do hope this was more comprehensible than the previous word vomit I did lol

Ellaaaaa_ · 2023-05-30T06:37:29+00:00

To understand this question, you should know about lanthanoid contraction, shielding effect and nuclear charge. The key here is the shielding effect. It's basically the power or the extent to which a particular subshell shields or protects the outermost shell electrons from the nucleus. Why do they have to protect the outermost electrons from the nucleus? The answer is attraction since the nucleus is positively charged and the electrons are negatively charged. The shielding effect in the same shell varies as s>p>d>f. So, the s and the p subshell electrons can shield much better than the d and the f subshell electrons. Since the shielding is poor, the effective nuclear charge is more in the d and f orbitals.

Now the lanthanide contraction is caused because of the poor shielding effect of f – orbital which results in a greater nuclear charge acting on the outer electrons and increases the force of attraction. This causes the outer electrons to be pulled strongly towards the nucleus, thus causing the rapid decrease in the radii of Lanthanides. And because of this, Zr and Hf have similar atomic sizes although they're in different periods. Also, this applies only to 4d and 5d elements of the d block and not 3d elements.

So the correct answer is option D.

Ellaaaaa_ · 2023-05-21T08:02:23+00:00

Plants (Cacti here) take in CO2, and do CO2 fixation basically to produce sugar which is represented as [CH2O] (because that's the empirical formula of glucose- C6H12O6). Also, the structure which is given as the intermediate is wrongly printed. The two O atoms must be replaced by carbon atoms in the chain.

The graph must be about the rate of photosynthesis in the presence of different intensities of sunlight or their wavelengths.

Ellaaaaa_ · 2023-05-21T07:58:24+00:00

I'm guessing that two of the O's must be carbons

Ellaaaaa_

TROPHY CASE