00:00
Before we move into the course, it's really important
for us to establish what life is.
00:06
Some might debate that viruses and prions are non living.
But certainly, cells are living.
00:13
So we're going to explore some brief comparisons between
eukaryotic and bacterial or prokaryotic cells.
00:20
Yes, there's another division, another type of cells
called archaeas. But they're not really components of human body.
00:26
We're going to be dealing primarily with
bacterial cells and eukaryotic cells
and on occasion throughout this course,
we'll be exploring some mechanism of viruses.
00:39
So comparing prokaryotic and eukaryotic cells,
they both have ribosomes, they both have DNA.
00:46
They both have cell membranes. Bacterial cells have cell walls
whereas eukaryotic cells generally do not have cell walls.
00:57
Plant cells have cell walls.
And fungal cells have cell walls.
01:02
However, animal cells lack a cell wall at all.
Both cell membranes are composed of phospholipid bilayers.
01:10
Both have ribosomes although
prokaryotic and eukaryotic ribosomes are slightly different.
01:18
We'll explore those in further lectures.
01:22
And then in general, a eukaryotic cell is about
ten times larger than a prokaryotic cell.
01:29
And as I mentioned, in addition we'll be visiting
viruses and prions briefly.
01:34
Viruses, technically they are non living.
They're composed of a protein capsid, so a protein outer coat
with a nucleic acid or DNA core.
Sometimes an RNA core in the case of retroviruses.
01:49
In addition, some virus like the AIDS virus
also have a viral envelope
which has enveloped protein studded over the surface
for recognition purposes.
02:02
And finally, prions. Prions have given us
some questions to think about
because they contain no DNA. However, they're contacting
other proteins, can cause them to fold in a different way.
02:15
And they seem to have some sorts of genetic capacities,
yet zero DNA.