Proteins and Nucleic Acids : Key Biomolecules II

Proteins and Nucleic Acids : Key Biomolecules II


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
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