Recent comments in /f/askscience

Alternative-Boot2673 t1_jd8i087 wrote

Reply to Has the HIV virus become less deadly? by shaun3000

Not on point but, on behalf of a lifelong friend who survived 8 yrs after AIDS diagnosis in 1993, there are indirect deaths related to being HIV+ or diagnosed with AIDS: Treatment and protocols were/are costly and time consuming (continuous multiple doctor appointments with multiple specialists, then adhering to multiple regimens) so people died because they could not afford to get adequate and timely treatment; protease inhibitor side effects could kill you (cholesterol levels in the high 3 digits/low 4 digits = pulmonary embolisms); and early onset dementia (not sure if from HIV or AIDS), affected critical decision making (stopped heeding medical advice and adhering to treatment, began/increased self-medicating).

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EdSmith77 t1_jd8hyzy wrote

Reply to Before forming a peptide bond the amino acid contains a carboxyl group, which reacts with the amine group to produce a peptide bond and water is produced. What is the name for the new groups in an amino residue within a polypeptide, if there are any? Especially the C=O left from the carboxyl group? by flowergirlhyuck

If I understand your question, the group formed between the amine and carboxyl group with loss of a water molecule is called an amide. (I tried to parse what you meant by "new groups", and "C=O left from the carboxyl group"). The "C=O left from the carboxyl group" is part of the new group ("amide").

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Greyswandir t1_jd8hqjv wrote

Reply to When people can’t walk it means they have broken neural pathways. Then why can’t you just connect them? by CuteAlexaL

First off, there are lots of causes that could lead to someone not being able to walk, and severed nerves or damaged neural pathways are only one of them.

Nerves cannot be naturally regrown by the body, and are delicate and difficult to work with. So far it hasn’t really been possible to do the kind of reconnection you’re thinking of. But there are groups working on that! For example there are projects that implant sensors “upstream” of the break to measure signals and then stimulating electrodes “downstream” of the break to match those measures signals. They’ve started having some pretty remarkable success too.

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El_Sephiroth t1_jd8g124 wrote

Reply to comment by acquavaa in When the amplitude of a longitudinal wave changes, why doesn't the wavelength change? by senpai_maccer

The analogy really ain't that good. Try with a water wave or a guitar string. If you pull a guitar string further the vibration it has gets a bigger amplitude but its mechanical resistance and border limitations won't change. This means the string will move faster or slower but it will oscillate at the same frequency.

Since the frequency is the same, the note is the same. But since amplitude varies, the sound is more intense.

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slouchingtoepiphany t1_jd8fo7h wrote

Reply to What happens when we die? by darsenalmex11

You're asking a good question. When a cell dies, it's because it loses the ability to make ATP, the product of oxidative metabolism and glycolysis and is sometimes called the "universal currency" for cellular reactions. The lack of ATP results in many things going wrong, including the cell's ability to maintain the integrity of its membranes, but many other reactions that are deleterious to the cell also take place. The cells that are most vulnerable to this are those that are the most metabolically active, which include the brain and heart. When these fail, many of the body's systems also fail and death may be declared when an individual has lost circulatory, respiratory, or CNS (brain) function.

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ajnozari t1_jd8f1rj wrote

Reply to Before forming a peptide bond the amino acid contains a carboxyl group, which reacts with the amine group to produce a peptide bond and water is produced. What is the name for the new groups in an amino residue within a polypeptide, if there are any? Especially the C=O left from the carboxyl group? by flowergirlhyuck

AFAIK they still retain their original names.

You have the Amino group, Carboxyl Group which are alternatively referred to as terminus (N-terminus, C-terminus) if they are at the first and last amino acid in the chain respectively.

Then you have the R group that is also attached to the alpha-carbon of the amino acid. There is a fourth bond on this alpha carbon to a hydrogen.

To answer your question the carboxyl group from the newly added amino acid would (temporarily) be the c-terminus until a new amino acid is added to extend the chain.

If there are other names (I’m sure there are) they aren’t as commonly used.

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fastspinecho t1_jd8ckeq wrote

Reply to What happens when we die? by darsenalmex11

First of all, there are two clinical definitions of death. The traditional definition is irreversible loss of blood circulation. The heart doesn't "decide" to do this, but due to some injury it can no longer pump blood. This means it can no longer deliver oxygen to the rest of the body, which means most of your organs can no longer produce sufficient energy to maintain homeostasis. Among other things, cells need to constantly use energy to pump water out of themselves. Without energy, they usually swell up and rupture. Again, this is not a "decision" or signal sent to the body, any more than a balloon decides to pop when punctured by a needle.

The second definition of death is "brain death". This means that brain cells are no longer receiving blood, and are all dying for the reasons given above. Other organs may still be receiving blood, but legally the person is still dead.

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