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Lecture 2
Chemical Basis of Life

Introduction:
A. Chemistry deals with the composition of
substances and how they change.
B. A knowledge of chemistry is necessary
for the understanding of physiology
because of the importance of chemicals
in body processes.
Structure of Matter:
A. Elements and Atoms:
1.
Matter is anything that takes up space.
2.
All matter is composed of elements, 92 of which occur
naturally.
3.
Living organisms require about 20 elements, of which
oxygen, carbon, hydrogen, and nitrogen, phosphorus and
sulfure are most abundant. If Ca included (99%)
4.
Elements are composed of atoms; atoms of different
elements vary in size and in how they interact.
C. Bonding of Atoms:
1.
Ionic bond
2.
Covalent bond
3.
Disulfide bond
4.
Hydrogen bond
C. Bonding of Atoms:
1. Atoms form bonds by gaining,
losing, or sharing electrons.
2. Electrons are found in shells
around the nucleus.
a. The first energy shell holds
two electrons; the other energy
shells each hold eight electrons
when on the outside.
C. Bonding of Atoms:
3.
Atoms with incompletely filled
outer shells tend to be reactive to
form stable outer shells of 8.
4.
When atoms gain or lose
electrons, they become ions with
a charge. Whether they gain or
lose will depend on how many
they have in the outer shell to
start with.
5.
Oppositely-charged ions attract
each other and form an ionic
bond.
E. Formulas:
1.
A molecular formula represents the
numbers and types of atoms in a molecule.
2.
Various representations, called structural
formulas, can be used to illustrate
molecules.
G. Acids and Bases:
1. Substances that release ions in water are called
electrolytes.
2. Electrolytes that release hydrogen ions in water
are called acids.
3. Electrolytes that release ions that combine with
hydrogen ions in water are called bases.
G. Acids and Bases:
4.The concentrations of H+ & OH- in the
body is very important to physiology.
5.pH represents the concentration of
hydrogen ions [H+] in solution.
Chemical Constituents of Cells:
A. Compounds that contain both hydrogen and
carbon are called organic, the others are inorganic
1. Water
B.
Inorganic Substances
a. Water is the most abundant compound in
living things and makes up two-thirds (60-75%) of
the human body.
b. Water is an important solvent so most metabolic
reactions occur in water.
c. Lubricant
d. Temperature regulator
B.
1.
2.
Water Compartments
Intracellular Fluid (65% of total body water)
Extracellular fluid (35%)
a.Plasma
b.Lymph
c. Tissue fluid or interstitial fluid
d.Specializied fluid
(Synovial fluid and
Cerebrospinal fluid and
aqueos humor)
B.
Inorganic Substances
2. Oxygen
a.Oxygen is needed to release energy
from nutrients and is used to drive
the cell's metabolism.
3. Carbon Dioxide
a.Carbon dioxide is released as a waste product
during energy-releasing metabolic reactions.
Energy is released in the form of ATP
Blood gases (arterial blood tells about Respiratory and
circulatory system)
Nitric Oxide (NO)
Endothelium of blood vessels
Vasodilation
Impulse transmission
Immune system
Clinical trials in Pulmonary H
Premature birth babies
C. Organic Substances:
1. Carbohydrates
a. Carbohydrates provide energy for cellular activities and are
composed of carbon, hydrogen, and oxygen.
b. Carbohydrates are made from monosaccharides (simple
sugars); disaccharides are two monosaccharides joined together;
complex carbohydrates (polysaccharides), such as starch, are
built of many sugars.
Glucose+Glucose= Maltose
Glucose+Fructose=Sucrose
Glucose+Galactose=Maltose
Starches-plant, cell-enzymes convert to ATP
e.g Glycogen
2.
Lipids:
a. Lipids are insoluble in water and include fats,
phospholipids, and steroids.
b. Fats supply energy, are composed of oxygen,
carbon, and hydrogen, and are built from
glycerol and three fatty acids.
2.
Lipids:
c. Phospholipids contain glycerol, two fatty
acids,
and a phosphate group, and are important in cell
structures. e.g Cell membrane, myeline
d. Steroids are complex ring structures, and include
cholesterol, which is used to synthesize the sex
hormones.
e.
f.
Chylomicrons by small intestine and lipoproteins
by liver
LDL and HDL
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3.
Proteins:
a. Proteins have a great variety of functions in the
body---as structural materials, as energy sources,
as certain hormones, as receptors on cell
membranes, as antibodies, and as enzymes to
catalyze metabolic reactions.
3.
Proteins:
b. Proteins contain C, O, H, and nitrogen atoms;
some also contain sulfur.
c. Building blocks of proteins are the amino acids,
each of which has a carboxyl group, an amino
group and a side chain called the R group.
3.
Proteins:
d. Proteins have complex shapes held together by
hydrogen bonds.
e. Protein shapes, which determine how proteins
function, can be altered (denatured) by pH,
temperature, radiation, or chemicals.
4. Nucleic Acids:
a. Nucleic acids form genes and take part protein
synthesis.
b. They contain carbon, hydrogen, oxygen, nitrogen,
and phosphorus, which are bound into building
blocks called nucleotides.
4.
Nucleic Acids:
c. Nucleic acids are of two major types: DNA (with
deoxyribose) and RNA (with ribose).
d. RNA (ribonucleic acid) functions in protein
synthesis; DNA (deoxyribonucleic acid) stores the
molecular code in genes.
Summary
Chapter 3
Cells
Introduction:
A.
The human body consists of 75 trillion cells
that vary considerably in shape and size yet
have much in common.
B.
200 different kind of human cells
B.Differences in cell shape make different
functions possible.
A Composite Cell:
A. A composite cell includes many different
cell structures.
B.A cell consists of three main parts---the
nucleus, the cytoplasm, and the cell
membrane. RBC is exception
C. Within the cytoplasm are specialized
organelles that perform specific functions for
the cell.
D. Cell Membrane:
1.
The cell membrane regulates the movement
of substances in and out of the cell,
participates in signal
transduction, and
helps cells adhere to other cells.
2.
It is made of Phospholipids, cholesterol,
proteins
D. Cell Membrane:
2. General Characteristics
a.
The cell membrane is
extremely thin and selectively
permeable.
b.
It has a complex surface with
adaptations to increase
surface area.
D. Cell Membrane:
3. Cell Membrane Structure:
a. The basic framework of the cell membrane
consists of a double layer of phospholipids,
with fatty acid tails turned inward.
b. Molecules that are soluble in lipids (gases,
steroid hormones) can pass through the lipid
bilayer.
D. Cell Membrane:
c. Embedded cholesterol molecules strengthen the
membrane and help make the membrane less
permeable to water-soluble substances.
d. Many types of proteins are found in the cell
membrane, including transmembrane proteins
and peripheral membrane proteins.
D. Cell Membrane:
e. Membrane proteins perform a variety of functions
and vary in shape.
f. Some proteins function as receptors on the cell
surface, starting signal transduction.
g. Other proteins aid the passage of molecules and
ions.
D. Cell Membrane:
h. Proteins protruding into the cell anchor supportive
rods and tubules.
i. Still other proteins have carbohydrates attached;
these complexes are used in cell identification.
Membrane proteins called cellular adhesion
molecules (CAMs) help determine one cell’s
interactions with others.
Movements Through Cell Membranes
A. The cell membrane controls what passes through it.
B.
Mechanisms of movement across the membrane
may be passive, requiring no energy from the
cell (diffusion, facilitated diffusion, osmosis,
and filtration) or active mechanisms, requiring
cellular energy (active transport, endocytosis,
and exocytosis).
Movements Through Cell Membranes
(cont.)
C. Passive Mechanisms
1. Diffusion
a.
Diffusion is caused by the random motion
of molecules and involves the movement
of molecules from an area of greater
concentration to one of lesser
concentration until equilibrium is
reached.
Movements Through Cell Membranes (cont.)
C1b. Diffusion enables oxygen and carbon dioxide
molecules to be exchanged between the air and
the blood in the lungs, and between blood and
tissue cells.
Movements Through Cell Membranes
C2.Facilitated Diffusion
a.
Facilitated diffusion uses membrane
proteins
that function as carriers to move
molecules (such as glucose) across the cell
membrane.
b. The number of carrier molecules in the
cell membrane limits the rate of this process.
Movements Through Cell Membranes
C3.Osmosis
a.
Osmosis is a special case of diffusion in which
water moves
from an area of greater water
concentration (where there is less osmotic pressure)
across a selectively permeable membrane to an area of
lower water concentration (where there is greater osmotic
pressure).
Movements Through Cell Membranes
A solution with the same osmotic pressure as body
fluids is called isotonic; one with higher osmotic
pressure than body fluids is hypertonic; one with
lower osmotic pressure is hypotonic.
Movements Through Cell Membranes
C4. Filtration
a. Because of hydrostatic pressure, molecules can be
forced through membranes by the process of
filtration. Blood pressure is a type of hydrostatic
pressure.
Movements Through Cell Membranes
D. Active Mechanisms
1.
Active Transport
a.
Active transport uses ATP to move
molecules from areas of low
concentration to areas of high
concentration through carrier
molecules in cell membranes.
b.
As much as 40% of a cell's energy
supply may be used to fuel this
process.
Meiosis
G. Cell aging
Cell differentiation reflects genetic control of
the nucleus as certain genes are turned on
while others are turned off.