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High school biology
Course: High school biology > Unit 1
Lesson 2: Important molecules for biology- Elements and atoms
- Introduction to carbohydrates
- Introduction to proteins and amino acids
- Introduction to lipids
- Introduction to nucleic acids and nucleotides
- Introduction to vitamins and minerals
- Biological macromolecules review
- Biological macromolecules
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Introduction to nucleic acids and nucleotides
Nucleic acids, crucial macromolecules for life, were first discovered in cell nuclei and exhibit acidic properties. DNA and RNA, composed of nucleotide building blocks, store hereditary information. These polymers have a backbone of alternating ribose and phosphate groups, with nitrogenous bases forming ladder rungs. The sequence of nucleotides encodes genetic information, making nucleic acids fundamental to life. Created by Sal Khan.
Want to join the conversation?
- I think I might have an interesting question here:
At- 2:34on the video, Sal points out that the nitrogenous base part of the molecule has some basic characteristics and that the phosphate group part of the molecule has some acidic characteristics. 2:40
However, I paused to count the number of hydrogens in each and I saw that the phosphate group has a relatively small number (two hydrogens) whereas the nitrogenous base has more (four hydrogens), or in other words a higher concentration.
Since acidity/basicity is determined by the concentration of H+ atoms, wouldn't that make the nitrogenous base the more acidic one out of the two instead?
I mean I'm just speculating, but does anyone have a good explanation?(24 votes)- it depends on the nitrogenous base whether it is adenine, guanine or cytosine more hydrogen or oxygen molecules are added I hope this helps(3 votes)
- is DNA and RNA the only two types of nucleic acids discovered?(12 votes)
- In nature, yes. But researchers have actually created synthetic structures that can actually function similarly, using different molecules. These are sometimes called xeno nucleic acids (XNA).(18 votes)
- what are nucleic acids used for?(9 votes)
- Nucleic acids are the building blocks of DNA and RNA. DNA stores and expresses genetic and hereditary information, while RNA is used to move the information around through transcription and translation to create proteins to work for the cell.
Hope that helps!(22 votes)
- Way too fast!(4 votes)
- then slow it down to 0.5x lol(18 votes)
- If silicon has very similar properties to carbon, is it possible for DNA to be made of silicon?(7 votes)
- I do not believe so due to the size of Silicon being much larger than that of Carbon, though I suppose in some ways it could form something similar to DNA(5 votes)
- duude i totally thought it was NEW-clee-oh-tide not
new-CLAY-oh-tide(6 votes)- Don't think it matters all that much. Everyone will still know what you are saying :)(3 votes)
- whats the definition of a macro molecule? Do carbohydrates, proteins, lipids and nucleic acids all count as macro molecules?(3 votes)
- A macromolecule is a molecule containing a very large amount of atoms, such as a protein, nucleic acid, or synthetic polymer.(8 votes)
- Is a nucleoside a type of nucleic acid?(4 votes)
- No, nucleoside is the combination of sugar and base. (when you remove phosphate from nucleoTide).(6 votes)
- .....I am beyond lost. It's like he's speaking a foreign language, can someone help me please, I'm scared this will be on the test and I won't know what they're talking about.(4 votes)
- Don't fret! What do you want to start with first? We'll go as slowly as you need.(4 votes)
- I don’t see a difference between Adenosine mono phosphate and Deoxyribosine moniphosphate2:37(2 votes)
- In the five carbon sugar of Deoxyadenosine Monophosphate, it is missing a oxygen atom while the Adenosine Monophosphate has the "missing" oxygen atom.(6 votes)
Video transcript
- [Narrator] We are
now going to talk about what is perhaps the most
important macro molecule in life, and that is known as nucleic acid. Now first of all where
does that name come from? Well scientists first
observed this in the nucleus of cells and so that's where
you get the nucleic part. And it has some acidic properties and so that's where you get the acid part. And perhaps the most
famous of the nucleic acids is deoxyribonucleic acid or DNA for short. And we'll go into some
depth in this as we go through our journey in biology, but you might already know
that this is the molecule that stores our hereditary information. This DNA, to a large
degree, makes you you. And it's known as a macro molecule, and we've talked about macro
molecules in other videos, we've talked about carbohydrates, and we have talked about proteins. And DNA is a macro molecule because it can be made of
many millions of atoms. Just to get a sense of it,
you can see right over here, the double helix of DNA,
where you have one side of your helix right over
there and then another one right over here and then
you kind of have these rungs of this twisted ladder. A DNA molecule, let's
say in the human genome, a chromosome, for example, is primarily a really long DNA molecule. And they can have on the
order of a hundred million rungs to this ladder. Now another thing to appreciate
like many other macro molecules, DNA, or
nucleic acids in general, they are polymers in that
they're made up of building block molecules and those building
blocks for nucleic acids and DNA is the most famous nucleic acid and RNA, Ribonucleic acid
would be a close second. But the building blocks of
them are known as nucleotides. Nucleotides. And we see some examples
of nucleotides over here. This is deoxyadenosine monophosphate, which would be a nucleotide found in DNA. You can see the various parts of it. You have a phosphate
group right over here. You have a five carbon sugar,
which in this case, is ribose. And then you have what is
known as a nitrogenous base. And why is it called nitrogenous? Well all those blue
circles represent nitrogen and we've seen this before,
the grays are carbons. And the reds are oxygens
and the whites hydrogens. And so this part of the molecule has some basic characteristics. While this phosphate group at the end this has some acidic characteristics. And what happens is they
get stacked onto each other where the ribosephosphates
alternate to form the backbone of this DNA molecule. You can see it right over here where you have a phosphate and a ribose and a phosphate and a ribose. And then you have the
nitrogenous base forming part of the rung of the ladder. And the way that DNA
stores information is, every one of these nitrogenous
bases right over here this is adenine, it has a
complimentary nitrogenous base on the other to complete
that rung of the ladder. So adenine matches with thiamine and DNA and we'll see in future videos in RNA, it's a nitrogenous base known as urasil, and guanine matches with cytosine. Don't worry too much about this now, we'll go into some depth
in this in future videos when we talk about DNA and how
information is stored in it. But for the sake of this
video, just appreciate that the monomer for a nucleic acid like DNA is a nucleotide. So monomer, and to be very
clear, this would not be the only monomer, the
analogous nucleotide in RNA, which stands for ribonucleic acid would be adenosine monophosphate right over here. You can see the difference between the two that we have an oxygen right over here, and we don't have an
oxygen right over here. That's why this is
called deoxy, and that's why it's deoxyribonucleic acid. You're missing one of those oxygens on your five carbon sugar. But adenine as I mentioned is
not the only nitrogenous base. You could have a nucleotide
where the nitrogenous base is thiamine, and so once
again, this looks very similar but notice what is going on over here. You could have a nucleotide
that looks like this. Once again, you have your
five carbon sugar here, you have your phosphate group,
but the nitrogenous base here keeps on changing. And it's the order of
these different nucleotides that actually encodes
the information in DNA. Now one question you
might say is, well look, if I have this part of
the molecule that has basic characteristics, why
is it considered an acid? Well look at how this
molecule is structured. The basic parts form the
rungs of this ladder. So they're not going to be as reactive because they're really
tied, they're closer to the inside of the molecule
while the acidic parts, the phosphate groups are on the outside. So they're going to be more reactive. And so the molecule as
a whole is going to have an acidic characteristic. I'm going to leave you there. In future videos we're going to go into a lot more depth in the
importance of nucleic acid, especially DNA and RNA. And to just appreciate how
amazing these molecules are. Some folks theorize that
the first signs of life were nothing more than
self-replicating RNA molecules that eventually got enclosed
in some type of membrane structures, which eventually
started forming the genetic machinery of a cell etc, etc, etc. So this is why these
nucleic acids are sometimes considered the most fundamental
macromolecules to life.