Biology 1A Intro: Course Logistics, Foundations, Water

Name: Biology 1A Lecture 1
Uploaded: 2015-05-01T18:10:40+00:00
Duration: 46 min 55 s
Channel: Saylor University
Description: Summary and key takeaways on Biology 1A Lecture 1: Summary & Key Takeaways, covering Course Administration The first week contains no labs or discussion

Saylor University

May 01, 2015

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46 min video

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2 min read

YouTube video ID: w3HtRAryxXI

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The first week contains no labs or discussion sections. Students must switch lab or discussion sections by Friday; changes depend on capacity and are not guaranteed. Starting next week, each student attends the assigned section. All Biology 1A exams occur in the morning, either 8:00–9:00 a.m. or 8:00–11:00 a.m. The first lab exam takes place on Wednesday night, March 16, from 6:30–8:30 p.m. The exam schedule includes a first exam on Friday, February 18 (8:00–9:00 a.m.), a second exam on Friday, April 1 (8:00–9:00 a.m.), and a final exam on May 9 (8:00–11:00 a.m.).

Academic Expectations

Success requires moving beyond memorization to application and synthesis. Students read the textbook, focusing on material covered in lectures, and review lecture notes posted on BSpace before each class. Office hours serve as the primary venue for resolving questions; email responses are not guaranteed for large classes.

Introduction to Biology

Biology studies life from molecular levels to ecosystems. Evolution functions as the central theme, explaining that all living organisms are modified descendants of common ancestors. Systems biology integrates molecular data with computational models to predict dynamic network behavior. Emergent properties arise from interactions among components, making it necessary to examine whole systems rather than isolated parts.

Chemical Foundations of Life

Matter consists of elements that combine into compounds with properties distinct from their constituent elements. Carbon, hydrogen, oxygen, and nitrogen comprise over 95 % of living matter; approximately 25 elements are essential for life. Trace elements such as selenium, zinc, and iodine are required in small amounts for enzymatic function and hormonal health. Iodine deficiency causes the thyroid gland to enlarge as it attempts to produce sufficient thyroid hormone.

Properties of Water

Water’s bent molecular shape creates polarity, giving each molecule a partial positive charge on hydrogen atoms and a partial negative charge on the oxygen atom. Hydrogen bonding between adjacent molecules forms a cohesive network. This network produces four key biological properties:

Cohesion and adhesion – water molecules stick together and to other surfaces, enabling transport in plants.
Temperature moderation – high specific heat buffers climate and maintains cellular homeostasis.
Expansion upon freezing – a crystalline lattice forms when water freezes, occupying more space than liquid water.
Solvent versatility – water dissolves a wide range of substances, making it the primary biological solvent.

Takeaways

The first week has no labs, section changes must be submitted by Friday, and all exams are scheduled for morning hours with specific dates provided.
Students succeed by shifting from memorization to synthesis, using the textbook, lecture notes on BSpace, and office hours for support.
Biology examines life from molecules to ecosystems, with evolution as a unifying theme and systems biology linking data to computational models.
Life’s chemistry relies on carbon, hydrogen, oxygen, nitrogen and trace elements; deficiencies such as lack of iodine cause thyroid enlargement.
Water’s polarity and hydrogen bonding create cohesion, temperature regulation, expansion when frozen, and solvent versatility essential for cellular function.

Frequently Asked Questions

Why is evolution described as the overarching theme in an introductory biology course?

Evolution provides a unifying framework that explains how all living organisms are modified descendants of common ancestors, guiding interpretation of biological data across molecular, organismal, and ecosystem levels.

How does hydrogen bonding give water its unique properties relevant to biology?

Hydrogen bonds form between the partial positive hydrogen of one water molecule and the partial negative oxygen of another, creating a cohesive network that yields high surface tension, temperature moderation, expansion upon freezing, and the ability to dissolve many substances, all supporting cellular processes.

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Does this page include the full transcript of the video?

Yes, the full transcript for this video is available on this page. Click 'Show transcript' in the sidebar to read it.

Helpful resources related to this video

If you want to practice or explore the concepts discussed in the video, these commonly used tools may help.

Campbell Biology Textbook Recommended

This is the primary textbook recommended for the course, essential for reading assignments and mastering the biological concepts covered in lectures.

Amazon →

Molecular Biology Model Kit

These kits allow students to physically build molecular structures like water, helping them visualize polarity and hydrogen bonding.

Amazon →

Academic Planner For College Students

The course emphasizes not falling behind and provides specific exam dates; a planner helps track deadlines and study schedules.

Amazon →

Highlighter Set For Textbook Study

Active reading of the textbook is required; highlighters help organize and synthesize complex biological information.

Amazon →

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Full Transcript YouTube

Uh good morning. Uh welcome to biology
1A. My name is Mike Mian. I'm the
academic coordinator for biology 1A. I
will deal with a lot of the
administrative issues, uh grades, exams,
things like that. Uh my contact
information is on the syllabus. I'll
also be the lecturer for biology 1A.
There are no labs and no discussions
this week. I'm going to say it one more
time. There are no labs, no discussion
this week. All labs, all discussions
begin next week. You don't need to come
to lab this week to check into lockers.
No lab, no discussion this week. All
right, very clear. Now, a lot of you are
trying to switch lab sections or
discussion sections, etc. We've put all
that information on bespace about how to
do that. We'll try to process everything
this weekend. So, the deadline's pretty
much on Friday. Submit any forms you
want to try to switch discussion or lab
times and we'll see what we can do.
We'll work on it over the weekend and
we'll inform you by Monday whether or
not we were able to make the section
changes. Now, we can't guarantee section
changes. The problem is everything is
full. So, basically, if you want
section, let's say 12 for lab, I have to
have a student come out of section 12
and they have to move into maybe the
section that you're coming out of. So,
it's not real easy to do, but we will
process that. Uh deadline's pretty much
Friday. We'll process everything over
the weekend so that next week when you
go to lab and go to discussion, you must
go to the assigned section that you're
in. Okay, any questions about that?
No questions. Excellent. So, let's just
discuss the syllabus. Uh, I sent it to
you already via Bspace. You definitely
should read this carefully. I'm going to
go over the exam dates with you right
now. This is for the biology 1A class.
The first exam is Friday, February 18th.
That's in the morning, 8 to 9:00 a.m. It
will be in various rooms throughout the
campus. You'll get an exam handout as we
get closer to that. The second exam is
also on a Friday, and that is April 1st.
It's not April 1st, fool's joke. Exams
actually on April 1st, that Friday, 8 to
9:00 a.m. And then the final is May 9th,
8 to 11:00 a.m. Okay. So again, the
exams for bio 1A are 8 to 9:00 a.m. or 8
to 11:00 a.m. It's in the morning. Now,
the first lab exam for biology 1A lab is
going to be on a Wednesday night. I
think it's March 16th, 6:30 to 8:30.
That's at night. Uh please make sure for
the bio 1A exams you come in the
morning. For the bio1 lab exam, it's
going to be Wednesday night. We have had
many students who don't come to the exam
on that first Friday because they're
thinking it's at night. Question um for
the one exam, do we have labs that So
the question is, do you have lab the
week of the lab exam? No, because we
normally have labs on Wednesday night
and the exam is going to be Wednesday
night. So you will not have lab that
week and we'll talk more about that on
Monday night because the first lab
lecture is next Monday 5:00 to 6:30 here
in Pimentel. Any questions? Uh, words of
advice, studying. I know you've heard
that bio 1A and 1AL are both very hard
classes, and that's not a false rumor.
It's true. Okay? You're going to work
very hard in both classes. We are here
to help you, though. Okay? There's going
to be office hours. GSIS will have
office hours. The faculty will have
office hours. I'll have office hours.
Everyone teaching this class is teaching
it because they want to, okay? They're
not assigned to it. They want to teach
it. So, we really are here to help you.
But you have to take the initiative to
come to us. Okay? So like I said, we
have office hours. There's email. If you
email us 50 questions at midnight and
the exam's 8 in the morning, don't
expect responses probably. Okay? So be
prepared a little bit. Send us the email
a day or two ahead of time. The key
thing for this class, I think, is do not
fall behind.
Okay? So say that mentally out out loud
to yourself right now. Do not fall
behind.
All right, great. Now, really what
happens is this class is unlike the high
school biology classes. This class will
and the lab class will require you to
not only know a lot of facts because
those facts serve the foundation, but
you have to be able to apply those facts
and synthesize the information. And
that's a much higher integrative step
than usually what you did in high
school. So if you try to wait till the
night before the exam and try to cram,
the results usually are not very good
and it's very difficult if you do poorly
on that first exam to try to make up
that ground. Okay? So I'm just warning
you. I've done this for over 20 years.
Uh that's over 25,000 students fall,
spring, and summer. And the number one
consistent thing I see amongst all those
students who come talk to me, and
usually it's they're not doing well, is
they fell behind. They didn't realize it
was going to require so much work. So
don't fall behind when you study. Focus
not only on memorization but also on
application. Okay. Any questions about
that? Okay. So again, we're here to
help. We have office hours. We'll be
posting those on BSpace. And again,
welcome and good luck in the class.
Yes. Here we go. Great. Uh, well, thanks
a lot, Mike. And good morning, everyone.
My name is Jennifer Dana. I'm a
professor in molecular and cell biology,
and this is my, I think, third or maybe
fourth year teaching bio1a. There's a
break in the middle there. And, um, my
own research is on um, nucleic acid
structure and function. And I've been
very interested for my whole career in
uh in understanding how RNA molecules
are used in biology and in cells to do
all sorts of interesting things. So I
really I'm really a molecular biologist
and and my focus is on molecules and
that's what we'll be talking about in
this section of bio1a.
So um I just want to amplify a couple of
things that that Mike mentioned. So, if
you look at the at take a quick look at
the syllabus,
you'll see that in my section of the
course, we're going to cover the first
10 chapters of the of the textbook. This
is the book right here,
Campbell Biology. And um and actually uh
we're really going to focus on the the
uh starting with chapter five. So if you
take a look at the textbook, you'll see
that the first four chapters are really
very introductory material. They tell
they talk and we'll talk a little bit
about what I think are the highlights of
that material today. So basically they
cover what is biology um and some of the
basic chemistry that you need to know to
be able to understand the material that
we're going to talk about in this
course. For uh some of you or even for
many of you, this material will be
review. And so if it is then that's fine
and you should just um look through that
material and make sure that you are
familiar with it. For uh for others of
you this material some of it might be
new to you. And if it is or if you don't
feel very comfortable with the chemistry
that's presented in the text please do
make sure that you actually read uh more
of the material than I'm focusing on in
the lecture because it will be critical
for you to have that foundation to
understand the material that's going to
come later in the course.
Now students uh you know every year they
ask uh what do I need to know out of the
book? There's obviously a lot of
material in the book and we're not going
to cover it all in gory detail during
lecture. So what I try to do in lecture
is to call your attention to the things
that I think are really the the most
exciting and interesting and critical
things for you to understand and and to
come away knowing from this course. Um
do I want you to not read anything else
in the book? No. Read whatever you want
to read. But you should be sure to make
sure that you really understand and
focus on the material that we're
covering in lecture. When I write an
exam, I'm going to focus on the material
that we have specifically discussed in
the lectures and that is covered in
somewhat more detail in the course. And
each of my lectures will tell you
exactly what you need to read in the
book to be uh sure that you have the
background that you need to know in
terms of studying for the exam.
And uh finally, whoops. Okay, let's see.
Can we switch to the slides, please?
So, uh Mike mentioned BSpace. So, what
what I'll plan to do is be posting each
week before the usually by the end of
the weekend, I will post the uh lecture
notes for the lectures to come that
week. So, if you want to read ahead,
you're welcome to download those and
look at them. Uh but they will be there
for you on Vspace, uh the week ahead of
the lectures.
Okay. Um, my office hours are going to
be Mondays 12 to 1 pm and Fridays 1:15
to 2:15 p.m. This is also in the uh it's
listed in here, so if you don't need to
necessarily write it down, it's also on
BSpace if you forget. And I'm going to
hold office hours in VLSB 2084. Okay,
this is a little bit bigger room than my
office. I tried to do it in my office in
the past and that was a little bit
tough. So, uh, so please, uh, come to my
office hours if you have questions. You
can also send me an email, but um
there's a lot of uh students in the
class obviously, so um I can't guarantee
that I'll be able to answer uh questions
uh by email. And in general, I encourage
you to if you have questions, please
come to my office hours.
Okay. So, um today, uh as I mentioned,
we're going to be focusing on the very
beginning material in the textbook. And
these are the specifically the pages
that you should uh have a look at and
focus on as you're studying this
material. But like I said, please be
sure to look through the first four
chapters of the text. And if any of that
introductory material is not familiar to
you, you do need to know it for the
course. Okay? And um and what I want to
just cover today in class is to talk a
little bit about the levels of
biological organization. We're going to
talk a little bit about the chemistry of
life. And then we're going to talk a
little bit about the properties of water
that are essential for understanding um
the way that biological molecules and
systems can function because without
water none of us would be here.
Okay. And one one other thing I want to
mention. So of course the class is quite
large and um it makes it harder for us
to have a a personal connection. But if
you are sitting in the audience and I
say something that doesn't make sense,
there's a good chance that a lot of your
classmates feel the same way. So if
there is a burning question that comes
up when I'm uh giving the the lecture,
please do ask a question because I think
that's important for everyone's
understanding.
Okay. So, um, as you as we think about
biology and and especially as you start
to look at the textbook, you'll see
that, um, an important underlying theme
in all of what we're going to be
discussing is evolution. And this is a,
um, a theme in biology that really
underscores everything that we think
about from whether we're thinking about
molecules, whether we're thinking about
organisms, or whether we're thinking
about whole ecosystems, right? Is
everything is really interconnected. And
we'll be touching on that theme uh quite
a bit as we go through this material.
And um and so biology is really the the
scientific study of life, trying to
understand how it is that life exists,
how it works, and how uh different kinds
of uh levels of different systems in
biology interact.
And biologists who um uh study various
aspects of biology ask questions such as
how does a single cell develop into a
whole organism?
How does the human brain work? And how
do living things interact in
communities? Right? And so there's many
different kinds of biologists and uh one
can ask questions at many different
levels and for many of us. So when I was
at the stage that you are all at um I
realized that what I really found
fascinating and most exciting was
molecules and I was very interested in
how molecules that are found in biology
are able to do all sorts of interesting
things. How is it that molecules can
ultimately confer the ability to
replicate and to reproduce and to
ultimately to think and to be who we are
as humans? So I think that for me that
really it was that level of
understanding that I wanted to be
working at but various you know
everybody's different and we all have uh
passions that that we have that uh that
tell sort of dictate the level at which
we want to understand something and
that's true in biology as well. Um, and
so as I mentioned, evolution is really
the overarching theme in biology. And
your book talks quite a bit about this
and and gives a little bit of the
history of Charles Darwin and his uh
original research. And and the thing
about evolution is that it really makes
sense of everything that we know about
living organisms. And um what we find is
that organisms that are alive are
modified descendants of common
ancestors. So that's a fame that runs
through really all of biology.
And one of the I uh point out here that
there's a really great I don't know if
anybody here may have seen this already,
but it's it's not that new, but it's a
really great three-part series that runs
on NOVA called Becoming Human. And um
you can actually download this for free
from the NOVA website. You can also buy
it for not very much off of iTunes. And
um this is a great uh series if you're
interested at all in sort of the
evolutionary history of humans because
it really talks about uh the work that's
gone into understanding human evolution
both at the level of anthropology and
looking at bones and trying to make
sense of of skeletons but also at the
level of molecules. So one of the things
that's really revolutionized the field
of anthropology in recent years is
genomic sequencing, DNA sequencing. So
it's been possible to um make a lot of
uh inferences about the connections
between different organisms and
different uh human ancestors by looking
at DNA sequencing data. And you may be
familiar with the fact that uh fairly
recently it was possible to sequence the
genomic DNA of Neanderthal
um uh uh remains. And so it was possible
to do some comparative analysis of the
DNA sequences found in Neanderthalss and
compare them to modern humans. And so
this kind of research at the molecular
level is really very important for
informing our uh thinking about in about
human evolution. And this goes on in
many other areas of biology as well. So
that's just one example of this the way
that this theme runs through everything
that we think about in biology. Um now
your book also talks about uh the
biological hierarchy and this is really
the idea that uh ultimately uh we start
off at the at the sort of highest level
thinking about the whole biosphere. So
this is really the way that all living
systems interact on the earth and how we
interact with our environment. And um
and then within the biosphere of course
we have various different kinds of
ecosystems and these can be divided into
communities and various populations of
organisms that live in these
communities. And then we can continue to
break it down into uh organs and systems
that are made up of individual cells.
inside of the cells or organels and and
molecules of course and these are what
comprise the tissues that we find in
living systems. And so in my section of
this course, we're really going to be t
focusing on this area over here,
figuring out what looking at how cells
are put together, how organels are made
up, and the molecules that we find in
those kinds of compartments. And what
you'll see is that in in biology, a lot
of it is about compartmentalization,
right? So cells are really just a way of
containing a set of molecules in a
particular place. And within the cells,
they're also uh compartments that are
highly organized. And that allows the
molecules that are inside of those cells
not to just to be floating around inside
of a a bag, but they actually are uh
positioned such that they can carry out
very specific kinds of functions. and
we'll be focusing on some of those kinds
of processes.
Okay. And so um this is another theme
that comes up in the textbook which is
the idea of emergent properties. So um
you know when we try to do experiments
as as scientists, it's very difficult to
um to do an experiment especially if
you're somebody like me who is studying
molecules. It's very hard to do that if
we are looking at an entire cell because
there's a lot of molecules in the cell,
right? I mean, a lot and many different
kinds and they're interacting and
they're changing and they're dynamic and
they're uh you know, they're moving
around. They're getting made and
destroyed all the time. And so, um if we
really want to understand the very
detailed chemical behavior of some of
those molecules, it's often easier to um
work with molecules individually or at
least in small sets. so that we can try
to define what's actually happening with
let's say a particular protein enzyme
and what kinds of activities it might
have and um but of course ultimately the
cell and the organism and the whole
biosphere really right is made up of the
properties that come together that are
produced when all of those molecules and
cells are interacting and so this is
really the idea of emergent properties.
So, uh, these are, uh, properties that
result from the interaction of all of
these individual components. And so as
we go through uh the material that that
I'll be covering in this section, you'll
see that we're often going to be talking
about individual molecules. But I want
you to keep in mind that it's really uh
in biology, we're really have to be
aware that each of those molecules
individually is really interacting in a
much larger framework in the context of
a cell or a tissue or an organism.
Right? And so as as scientists, we have
to be very uh cautious and just always
keep that in our minds. If we're working
with a an individual molecule that's
been purified in the laboratory, we
learn things about it, but uh it may
behave differently in the context of a
cell or an organism. Okay? And so um and
this is sort of just characterized by
the idea that uh we can sort of use this
analogy of a functioning bicycle. So we
can examine all the pieces and parts
that make up a bicycle and learn a lot
about how they work, but we probably
won't really understand uh the whole
bicycle unless we have it assembled into
its uh functional form. Right? So and
that's same is true in biology. So
there's sort of this tension between
trying to understand the individual
parts at a level at which uh we you know
we feel like we really know how they
behave and how they work and the
chemistry behind them. But uh we also
have to be cognizant of the fact that
they may work differently in the once
they're in the um in inside of an
assembled cell or organism.
Okay. Okay. And then um and I just want
to point out uh
that systems biology is kind of one of
the
uh I would say you know future
directions of of a lot of the kinds of
biology that we're going to be talking
about here which is that um there's a
really major effort to try to take a lot
of the information that we've been
learning about individual molecules in
biology and start to understand how it
is that they really do all work together
inside of a large network in the cell.
And so this is a this is an area of
biology called systems biology. And um
it's the idea that we can uh come up
with models that tell us about the
dynamic behavior of entire biological
systems. And how do we do that? Well,
you know, we start with understanding
individual molecular behavior, but then
we have to start asking how is it that
these molecules interact when they're
together in a cell? And um these are
important for asking questions like how
do drugs affect uh something like blood
pressure? Uh how do we think about
treating uh somebody that has a disease
like cancer? If we give them a drug
that's going to inhibit the growth of
cancer, what is it going to do to the
rest of the systems in their body, the
tissues in their body, right? And so we
have to start thinking uh more globally
about how these molecular interactions
are actually working. And this is a big
challenge and it really involves not
only experimental science and working
with individual uh samples, but we also
have to use computational biology.
There's an increasing effort and I think
it's really exciting that there's been a
lot a big influx of people into biology
who have very uh have a lot of interest
in mathematics and uh computation who
are coming up with increasingly
sophisticated models for the behavior of
molecules inside of large networks. So
can we understand what happens when for
example a small molecule drug is
introduced into a body into someone's
body. Uh it goes to it gets localized to
various places. It interacts with
individual molecules in their body but
it also uh gets metabolized. It gets
broken down in the liver by various
enzymes and those metabolites might have
various activities and eventually uh the
drug gets excreted. And so um it's a
it's a process that we can begin to
model computationally and then the hope
is that those kinds of models will allow
us to then as experimentalists go back
and test ideas that come out of those
models. So there's a kind of a back and
forth and um I think increasingly in
biology certainly in in the field of
molecular biology this is a this is a
very exciting time because there's a lot
of opportunities I think for taking
molecular understanding and really
trying to start to integrate it into the
the whole body put the bicycle back
together.
Okay. And so um chapter two of the
textbook really uh talks about the
chemical foundations for life. And um
why do we have to talk about chemistry
in a biology class?
Well,
molecules are chemicals, right? And so
they they really um we find that you
know living organisms of course are
subject to the basic laws of both
physics and chemistry. So um if we want
to be able to talk in any detail about
these kinds of molecules and their
behaviors in biological systems, we have
to understand some of the basic
chemistry. So um like I said, please
have a look at chapter 2. For a lot of
you, this will be review, but for some
of you, it might not be. So if it if
some of that material looks new, please
be sure that you that you study it.
Um
and I want to just point out a few a few
key concepts here. And I think these a
lot of these ideas will be um probably
obvious to many of you. Um but first of
all, matter consists of chemical
elements both in pure form and in
combinations called compounds, right?
And so um just as in in any science, we
have uh certain terms that we need to
learn and be familiar with so that we
can all converse at the same level about
this material. So we need to understand
what matter is. Organisms are composed
of it. And basically matter is anything
that takes up space and has mass. All
right.
And so uh to understand matter we have
to understand a little bit about the
elements and compounds. So um matter is
made up of elements. And an element is a
substance that cannot be broken down to
anything else to any other substance by
chemical reactions. Okay, that's an
element.
And um there they are over there.
And a compound is a substance that
consists of two or more elements that
come together in a fixed ratio. So that
we can write a chemical formula for a
compound. Right? So, water, H2O, that's
a very simple compound. Um, but there
are much more complex compounds that
make up many of the larger biological
molecules that are found in biology.
And most importantly, a compound has
characteristics that are very different
from those of its component elements.
All right? And so, um, we can ask, is
oxygen an element or a compound?
It's O2, but it's an element, right?
Yeah.
Iron is also an element, but water and
carbon dioxide are both compounds,
right?
Okay. And this is just a figure uh taken
out of the book. So, this shows a very
simple example of two elements. So,
here's sodium, which is a metal,
and chlorine, which is actually a
poisonous gas. Right? So these are both
elements but when they come together
they form an edible salt sodium
chloride. So we wouldn't want to have
much to do with these uh elements but
salt we use the every day right. So
that's just a very simple example of the
difference between elements and
compounds.
Now um in life so there are uh only
about 25 of all of the elements are
essential in life. the rest are not. And
of those 25, there's only four elements
that make up the vast majority of the
molecules that are of biological
importance. And those four are carbon,
hydrogen, oxygen, and nitrogen, right?
And they make up more than 95% of all
living matter.
And then what's what about the other 4%?
Well, the other 4% are mostly um
calcium, phosphorus, potassium, and
sulfur. Just so just four additional
elements. So, eight just eight elements
make up the vast majority of the
molecules that are found in biology. Um
and then there are of course a few trace
elements that are interestingly they're
also required by organisms and but
they're required in very small
quantities and those will be things like
selenium for example or zinc. Okay,
those are compounds that if we don't
have selenium or zinc in our diet at
all, uh we will not be healthy, right?
We will have serious problems. But if we
have too much of those uh trace metals
in our diet, we will also uh not be very
healthy, right? So it's important to
have trace metals around available but
not in in quantities that are too high.
Does anybody know? So why do we need
what are what do you think some of those
trace materials are actually doing? Does
anybody know why we need them in trace
amounts? Why would we need zinc?
I heard catalyst.
Yeah. So, that's sort of right. So, you
know, there are certain enzymes that
actually require um metals like zinc in
their active site and so that uh there's
and and there but they're only needed um
in a few enzymes in the body for
example. So that's why they're typically
needed just in trace amounts.
Was there a qu I saw a hand up back
there maybe? No. Okay. Okay. And then
this is also this is just a a table and
um in the ninth this is from the eighth
edition of the book. In the ninth
edition the table is drawn a little
differently. The material is all the
same. Um basically again showing you the
percentage of human body weight that is
comprised of these different elements.
Interestingly it's oxygen that is the is
the most abundant right followed by
carbon. We might have thought it would
be carbon but you know
and then we have uh these elements here
that are present in much lower
quantities. And then here are the some
of the trace elements down here.
Okay. And then um if we have
deficiencies of some of the essential
elements um both plants and animals have
uh will show effects. They'll show a
phenotype for that deficiency. Right?
And these are just a couple of examples.
So, um, this is an an experiment that
was done where this is a corn field and
we're, uh, these are two sets of corn
plants that are growing, one of which is
growing in soil that has an abundance of
nitrogen available for the plants.
And the plants on the right are growing
in soil that is nitrogen deficient. And
so what you can see is that the plants
that are uh have a rich source of
nitrogen are much taller. They're much
the leaves are much darker green. They
just look like healthier plants, right?
So um these plants are growing, but uh
they don't look nearly as healthy as the
ones that have an abundant source of
nitrogen. And then here's another
example. So this is a this is a an
example of a deficiency in humans. So
you know, humans need iodine. And again,
this is one of the trace elements that
you need and it's actually required for
the production of hormones that are made
in the thymus which is located in the
neck.
So if uh in diets and cultures where
there is not enough iodine that's
present in the diet then what tends to
happen is that the thymus enlarges
because it's straining to make enough of
the um of thyroid hormone and this
causes the the organ to actually
enlarge. And so you can actually see
that in this case right here where her
uh thymus gland has really enlarged due
to this deficiency of iodine in the
diet. So you probably know that um in in
um in our country iodine is added to
salt. So we have iodized salt and that's
a way that people are able to ensure
that they get enough iodine to avoid
this kind of deficiency.
Okay. And then I want to talk um now a
little bit about water because this is
really the molecule that makes life
possible. And so when you read in the
newspaper that you know water has been
found on Mars or somewhere else or on
the moon for example or there's evidence
of water, the reason that people get so
excited about this is because it's
really um thought to be unlikely that
life at least anything like the life
that we know would be able to evolve in
the absence of water. And so why is
that? Well, um, basically
on our planet, water is the biological
solvent, right? It's the it's the, um,
medium in which everything that is
related to life has been able to evolve
and continues to evolve. And in
addition, uh, we find that all living
organisms require water more than any
other substance. Right? So, we can go a
long time without food, but we can't go
very many days without water, right?
Because it's really essential for all of
the chemical reactions that are going on
in our bodies. It's essential for our
bodies to be able to um extract
nutrients, to metabolize nutrients, and
to excrete waste products. And u for all
of the all of those chemical reactions
to occur efficiently, there really has
to be sufficient water around and
available.
And we find that most cells are
surrounded by water. And even within the
cells, about 70 or more percent of the
cell itself is made up of water. And
that's a really important thing to think
about. So when we start talking about
DNA molecules and RNA molecules and cell
membranes and um and proteins and
lipids, it's important to remember that
these molecules are all surrounded by
water and so they have large shells of
hydration and that will affect their
behavior. will affect their ability to
interact with each other and with other
molecules. And it also means that um
that inside of the cell the environment
is what we call aquous, right? It's an
aquous environment. It's not a
hydrophobic environment. It's a
hydrophilic environment in general,
right? That means that molecules are
constantly interacting with water in
various ways. And so it's really
important to understand a little bit
about the structure of water and the
chemistry of water because it influences
so much of what we're going to be
talking about and thinking about in
biology.
And as I mentioned, the abundance of
water is really the main reason that the
earth is uh habitable at all. If we
didn't have water on this planet, um
very unlikely that we would find life,
certainly not as we know it. And this is
just a picture of of the planet. You
know, Earth is called the blue planet
for a reason, right? So, from space, uh
it's it's very clear that this planet
has a lot of water on it. More than 70%
of the surface is covered by uh water or
ice.
And so that um what can we say about a
little a little bit about the chemistry
of and of water that be influences its
behavior? And um so it's important to
understand that the water molecule is
what's called a polar molecule. And that
means that um that the opposite ends of
the molecule have opposite charges. And
that comes about because of the chemical
structure of water. So you all know that
water's chemical formula is H2O. So we
have one oxygen atom and we have two
hydrogen atoms that come together. And
um when they interact, they actually
don't interact in a symmetrical way. And
because of that asymmetry in the way the
molecule is structured, it sets up the
polar behavior of the of the water
molecule. And I'm going to show you that
here in a moment. Um and it's this
polarity that allows water molecules to
interact by means of hydrogen bonding.
Okay. Hydrogen bonding. And so I think
the next I think this slide has Yeah. So
this just shows um what I was mentioning
about the asymmetry of the structure of
water, right? So water is a kind of a
bent molecule and it looks like this.
And so what these partial charge
symbols indicate is that at one end or
one s one on one side of the water
molecule where the hydrogens's are this
tends to be positively charged in this
in these regions and on the on the other
side where the oxygen atom is localizing
the charge tends to be negative. Right?
So it's a polarized molecule for that
reason. We have negative charge over
here. we have positive charge over here
and because of that and so if you
imagine us um water molecules in liquid
water let's say these molecules are all
shaped this way and they all have this
polar property. So that means that
anywhere that we have a hydrogen on one
water molecule where we have this
partial positive charge that's a
available and and and it'll be a
favorable interaction to um be close to
an oxygen which has this partial
negative charge on an on an an adjacent
water molecule. So this sets up a
hydrogen bonding network. And so you can
imagine that we have lots of water
molecules in a liquid. These are all
going to be interacting in this way,
right? And when we have other forms of
water, for example, ice, what we find is
that in ice, the water molecules are
even more highly arranged, right?
They're they're arranged in a very
specific kind of lattice. It's sort of
called a crystallin lattice because if
you look at the structure all of the
water molecules are arrayed in a very
symmetrical way. And so if you um you
know if you uh have a let's say you have
a
um trying to think of a good example of
this. You know you have a have a can of
soda or something that you want to chill
quickly and you put it in the freezer
and then you forget about it and you go
back later and usually what has
happened?
Yes. Somebody said it's exploded. Right.
And that's because um as water freezes
it actually expands. And the reason it
expands is that the molecules in the ice
take up more space because they're
organized in this highly um sort of
crystallin network. They take up a lot
more space than they do when they're in
a liquid where they are interacting more
like this. They're packing more closely
together.
Now, I was going to show you a little um
video here. Let's see if I can get this
to work.
And this has sound to it. So we And I
have this plugged in. So can we um can
we have the sound turned on? Hopefully
this will work.
Okay. So, so that you know, so
understandably there's been a huge
amount of research that's gone into
understanding the structure of water and
how water molecules interact of course
with other kinds of molecules like
biological molecules that we'll be
talking about. And um and so I'll I'll
try to remind you um in later lectures,
but please do keep in mind that
everything that we're going to discuss
with these larger biomolecules is really
uh we have to think about the fact that
they are all in the context of water and
they are all interacting with water
molecules all the time.
So there are really four properties of
water that are probably the most
important in terms of contributing to
the um fitness of our earth for
supporting life and
these are the these are the properties
listed here and your book talks a lot
more about these um but first one is
cohesive behavior. So that means that as
we just discussed, water molecules like
to be together, right? They like to
interact with each other. They form
these hydrogen bonding networks. And it
turns out they not only form those
hydrogen bonding networks with each
other, but they also form hydrogen
bonding interactions with other kinds of
molecules. And that can really influence
the chemical behavior of those other
molecules. And we'll see this when we
start talking about in particular
nucleic acid structures and protein
structures like we're going to discuss
on Friday where u these uh water
molecules because they have this ability
to hydrogen bond they greatly influence
the way that biological molecules fold
up and um and the way that they turn out
to function. Okay, so that's one thing
cohesive behavior. Second thing is that
water is really good at moderating
temperature. And um here in the Bay
Area, you know this based on our
proximity to the bay and to the Pacific
Ocean, right? You know that if we're
really close to uh to if we're down at
the bay or we're we're on the right on
the ocean, the temperature and the
weather there is often very different
than what it is just even a mile or two
inland, right? And why is that? Well,
the water has a very large effect on the
climate and it has a very large effect
on the on the resulting temperature. And
so that's a sort of a very large scale
example of this. But this goes on all
the time inside of cells as well. And so
our cells and and our bodies are able to
regulate temperature in part because
we're so we're composed of so much
water. We have a lot of water around.
It's very easy for water molecules to
absorb heat and also to distribute heat.
so that temperature stays relatively
constant.
Okay, so that's the second uh property
of water. Third one is expansion upon
freezing. So we just talked about that a
little bit and um and so this is again a
property that is um really important for
uh bi for biology and for biological uh
samples because it means that um that
because the structure of water changes
so much on going from a liquid to a
solid. It really influences the way that
uh that biological um or you know that
way that organisms can interact in their
environment. Okay. and and something
that all organisms have to deal with.
They have to deal with this change and
protect themselves against um freezing
that occurs when water gets cooled. And
then ultimately uh water is a very
versatile solvent. So it can be used to
dissolve various different kinds of both
large biological molecules but also very
small molecules and make them available
to organisms to absorb. And and that's a
critical element for example in human
nutrition, right? We absorb nutrients
and small molecules in part because they
are dissolved in water inside of our
bodies.
Okay. And so um and then I want want to
just bring up these two terms right
here, cohesion and adhesion. So these
are uh terms that really have to do
again with the behavior of water. And I
just want to make sure that um you're
familiar with these. So uh this
phenomenon of cohesion is really this
idea that hydrogen bonds hold water
molecules together right and they also
and like I said they not only hold water
molecules together but they also hold
other kinds of molecules together and we
look at when we start looking at the
structure of enzymes and you know
proteins that uh form enzymes and other
kinds of important biological molecules
we'll see that water is really um
important in the formation of those
kinds of molecular structures.
Okay. And that's because of this
property of cohesion.
Cohesion helps the transport of water
against gravity in plants. So, um, you
know, you might wonder, you know, how is
a how is a a redwood able to pull
nutrients all the way from the ground
to, you know, maybe 80 or 100 feet in
the air. And that's in part because of
the the way that water, the cohesion of
water and the interaction of water
molecules are able to um push nutrients
up. And of course there's lots of other
things going on as well. But the it's
the fundamental chemistry of water that
plays an intricate part in that process.
Okay. And then um cohesion together with
cohesion there's another term I want you
to know which is adhesion. So this is an
attraction between different substances.
Right? And so this is we see adhesion in
in those interacting water molecules
that we looked at. But of course there's
also adhesion that goes on between water
molecules and all the other molecules
that are found in life as well. So again
it's a property that is very important
for life because it allows uh molecular
interactions to occur that if we were
trying to um have a world made out of I
don't know um you know uh ethanol or
something wouldn't be wouldn't be as
efficient. Okay. So water just turns out
to be a very very convenient solvent for
all of these kinds of reasons.
Okay. And then this is really just my
last slide for today. This is I just
want you to be familiar with the
following units of both temperature and
energy. Okay. So, um in most of uh most
of the US we often use the British
system, but I want you to you know when
we're talking about various uh concepts
that we'll be discussing in this course,
we'll often refer to temperature on the
Celsius scale. So you need to be
familiar with uh the Celsius scale for
measuring temperature. Okay, this is the
symbol for that. Um we're also going to
talk about energy in terms of calories.
So a calorie is the amount of heat
that's required to raise the temperature
of one gram of water by one degree
Celsius.
And you should note that uh some of you
might know this, but the calories that
are listed on food packages, these are
actually kilo calories, right? where one
kilo calorie is just a thousand
calories. So that gives you a sense of
the scale that we're actually talking
about. So a calorie is a pretty small
amount of energy, right? And then
finally, we're also going to sometimes
refer to jewels and this is another unit
of energy that's very commonly used
where one jewel is equal to a fraction
of a calorie 239 calories. Or we also
also uh need to know this conversion.
One calorie is 4.184 jewels. Okay, so
just make sure that you're familiar with
those terms for temperature and energy.
Have a good day and I'll see you guys on
Friday.

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Saylor University

May 25, 2026

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Introduction to Biology

Chemical Foundations of Life

Properties of Water

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