Hi, everyone! Welcome back to BOGObiology! This tutorial is going to cover proteins
and nucleic acids. We will discuss their structure their function and where they
can be found. Different groups of atoms combine to form biomolecules. When we
talked about carbohydrates and lipids, we used carbon hydrogen oxygen and
sometimes nitrogen. Now that we're discussing proteins and nucleic acids
we're going to add phosphorus and sulfur to the mix. For every kind of biomolecule,
it's important to understand its purpose, its location, and its structure. Using
this information, try to figure out what the relationship is between the
structure of the molecule and its function. Nucleic acids transfer the
genetic code between generations and also provide a "blueprint" that cells use
to make proteins. Usually nucleic acids are found in the
nucleus of the cell, although RNA will move out into the
cytoplasm to take part in protein synthesis. Usually nucleic acids are
helix-shaped with the double helix for DNA and a single helix for RNA.
Carbon, hydrogen, oxygen, nitrogen and phosphorus atoms are arranged strategically into
the building blocks of nucleic acids. These building blocks are ribose sugar
and then four other components called adenine, thymine, guanine and cytosine.
We also sometimes call these last four components nitrogen bases.
In RNA, there is an additional base called uracil which takes the place of thymine.
In the DNA molecule, all of these components are arranged in a shape that
resembles a twisted ladder. Notice how the sides of the ladder
alternate between ribose sugar groups and phosphate groups. Also notice how
adenine always pairs with thymine and guanine always pairs with cytosine.
The nitrogen bases are connected across the molecule using hydrogen bonds.
Adenine and thymine are connected using two hydrogen bonds, and guanine and
cytosine using three bonds.
We call these sets of nitrogen bases complementary pairs.
The order and combination of the base pairs in the DNA molecule
determines an organism's genetic code. Cells follow this code in order to
manufacture proteins.
This is actually a great way to segue into talking about proteins.
It's important to remember that there are
many, many, many kinds of proteins and we couldn't possibly talk about them all.
A few examples are enzymes, structural proteins, receptor proteins, motility
proteins, and contractile proteins. These are found in many different locations
including the digestive tract, the blood, neurons, cell membranes, and muscle tissue,
but there are obviously a lot more examples than that.
Proteins contain carbon hydrogen oxygen nitrogen and sometimes sulphur as well.
These atoms arrange themselves into something called an amino acid, which looks like this.
Notice how one of the carbons has an attachment called an R group.
There are actually 20 different R groups that could be attached to an amino acid,
and they are what makes each amino acid unique. The R group is the portion of the amino
acid that can sometimes contain an atom of sulfur. The 20 different varieties
serve as the building blocks for proteins. A series of amino acids is
strung together using connections called peptide bonds. Every time we attach a new
amino acid to the end of the chain, we remove one molecule of water in a
process called dehydration synthesis. When we've created a long string of
amino acids all connected in this way, we call it a polypeptide. When the
appropriate number of amino acids have been added, we fold up the polypeptide
into a structure known as a protein. The protein will have a specific shape
that's based on the task it will perform. Remember that a molecule is not
considered to be a protein until it's been folded.
The way the protein is coiled up can also make a huge difference in terms of its function.
Proteins may take on a primary secondary tertiary or quaternary structure.
When we have a number of protein subunits all working together, we call this a protein complex.
All right, that's pretty much it! If you enjoyed this video and found it
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