INTRODUCTION
An adult human body
consists of about 75
trillion cells.
There are at least 260
varieties of cells.
Cells differentiate
considerably in size,
shape, and function.
Cells have different,
distinctive shapes that
make possible their
functions.
HISTORY
Late 1600’s, Robert Hooke
was looking through a
primitive microscope at
some plant tissue (cork).
 Saw cube-like structure that
reminded him of monk’s
rooms (cells) so he named
the structure cells.
OVERVIEW OF THE CELLULAR BASIS OF LIFE
Cells are made up of 4 elements primarily: Carbon, Oxygen,
Hydrogen, and Nitrogen.
The other elements are important for cell functions:
 Calcium- blood clotting and other things.
 Iron- necessary to make hemoglobin (carries oxygen in the blood.
 Iodine is required to make the thyroid hormone that controls
metabolism.
 Calcium, potassium, and sodium- carry electrical impulse.
Electrolytes.
 Sodium and Potassium: nerve impulse and muscle contractions.
OVERVIEW OF THE CELLULAR BASIS OF LIFE
Cells are about 60% water.
Interstitial fluid- all the cells of the body are constantly bathed in
a dilute saltwater solution.
 Comes from the blood.
 All exchanges between cells and blood are made through this
fluid.
Cell size:
 2micrometers (1/12000th of an inch) to over 1 meter (3 feet)
 Long cells are nerve cells to your feet.
OVERVIEW OF THE CELLULAR BASIS OF LIFE
Cell structure reflects the job.
 Disk shaped - red blood cells
 Threadlike extensions - nerves
 Toothpick shaped - smooth muscle cells
 Cube-like - epithelial cells
 White blood cells - wander freely through the body tissue.
And protect the body by destroying bacteria and other
foreign substances.
ANATOMY OF A GENERALIZED CELL
All cells have three
main regions:
nucleus, cytoplasm,
and plasma
membrane.
 Nucleus- usually located
near the center of the cell
 Cytoplasm- semifluid in
the cell
 Plasma membrane- forms
the outer cell boundary.
NUCLEUS
DNA- contains the blueprint that contains all the instructions
needed for building the whole body
 Instructions for building proteins.
 If a cell ejects its nucleus it is programmed to die.
Nucleus usually forms to the cell shape so not always round.
Nucleus has three distinct regions:
 Nuclear envelope
 Nucleoli
 Chromatin
NUCLEAR ENVELOPE
Double membrane barrier
Between the two layers is fluid-filled moat.
At various points the two layers of the
nuclear envelope approach each other
and fuse- nuclear pores penetrate
through the fused regions
Selectively permeable but much freer than
else where because of large pores.
Encloses a jellylike fluid called
nucleoplasm in which nucleoli and
chromatin are suspended.
NUCLEOLI
One or more small, dark staining,
essentially round bodies.
Ribosomes are assembled here
Then the ribosomes are released
into the cytoplasm.
Ribosomes do protein synthesis.
CHROMATIN
Loose network of bumpy
threads
When a cell is dividing to
form two daughter cells
the chormatin threads
coil and condense to
form dense, rodlike
bodies called
chromosomes
PLASMA MEMBRANE
Fragile transparent barrier that contains
the cell contents and separates them
from the surrounding environment.
Consists of 2 lipid layers arranged “tail
to tail” in which protein molecules
float.
 Most of the lipid portion is
phospholipids with a substantial
amount of cholesterol.
 The heads are polar (hydrophilic)
 The tails are nonpolar (hydrophobic).
These tails make the cell relatively
impermeable to most water-soluble
molecules.
CELL MEMBRANE
PLASMA MEMBRANE
Some proteins are enzymes
Many proteins mounted on the cell exterior are receptors
for hormones or other chemical messengers.
Most proteins are for transport functions.
Glycoproteins- are a sugar protein. The cell surface is a
fuzzy, sticky area.
 Determine your blood type
 Changes in glycoproteins occur in cells that are being
transformed into cancer cells
SPECIALIZATIONS OF THE PLASMA MEMBRANE
Microvilli- tiny fingerlike projections that greatly increase the
cell’s surface area for absorption so that the process
occurs more quickly.
Membrane junctions- vary structurally depending on their
roles.
 Tight junctions- impermeable junctions that bind cells
together into leakproof sheets that prevent substances from
passing through the extracellular space between cells
 Keep digestive enzymes from seeping into the blood
stream.
SPECIALIZATIONS OF THE PLASMA MEMBRANE
Membrane junctions
Desmosomes- anchoring junctions that prevent
cells subjected to mechanical stress (skin cells)
from being pulled apart.
Gap junctions- commonly seen in the heart and
between embryonic cells, function mainly to
allow communication.
Connexons- connected to neighboring cells.
CYTOPLASM
The cellular material outside the nucleus and inside the plasma
membrane.
Site of most cellular activity. Factory area
3 major elements: cytosol, organelles, and inclusions.
 Cytosol is semitransparent fluid that suspends the other elements.
 Organelles are the metabolic machinery of the cell.
 Inclusions are not functioning units but are chemical substances
that may or may not be present
 Include fat droplets, glycogen granules, pigments such as
melanin, mucus and other secretory products and various
crystals.
CYTOPLASMIC ORGANELLES
Mitochondria- sausage-shaped organelles
 Squirm, lengthen and change shape almost continuously.
 Outer membrane is smooth but inner membrane has shelves
called cristae.
 Carry out reactions in which oxygen is used to break down
foods.
 Captured and used to form ATP molecules
 Powerhouse of the cell
 Liver cells and muscle cells have lots of mitochondria
 Unfertilized egg has few mitochondria
CYTOPLASMIC ORGANELLES
Ribosomes- tiny round, dark bodies made of
proteins and one variety of RNA called
ribosomal RNA.
Protein synthesis
Some float free in the cytoplasm and others
attach to membranes.
Rough endoplasmic reticulum has ribosomes
attached to it.
CYTOPLASMIC ORGANELLES
Endoplasmic Reticulum- is a system of fluid-filled
cisterns that coil and twist through the cytoplasm.
 Mini circulatory system for the cell
 Carries substances - mostly proteins
 Rough ER has ribosomes (export proteins)
 Smooth ER continuation of the rough variety. Does not
do protein synthesis. It does cholesterol synthesis and
breakdown (fat and detoxification of drugs) found in the
liver and testes
CYTOPLASMIC ORGANELLES
Golgi Apparatus- appears as a stack of flattened
membranous sacs, associated with swarms of tiny
vesicles.
 Traffic director of the cell
 Modify and package proteins
 Sends proteins out of the cell.
 Secretory vesicles pinch off and go to the cell
membrane and fuse with the membrane. The
membrane then ruptures to the outside of the cell.
Mucus and digestive enzymes are packaged this way.
CYTOPLASMIC ORGANELLES
Lysosomes- breakdown bodies, appear in different sizes and
are membrane bags containing powerful digestive
enzymes.
 Eat nonusable or worn-out cell structures and foreign
substances that enter the cell.
 Demolition site.
 Abundant in white blood cells
Homeostatic Imbalance:
 If the lysosomal membrane becomes fragile when a cell is
injured or deprived of oxygen and when excessive amounts
of vitamin A are present the cell self digests.
CYTOPLASMIC ORGANELLES
Peroxisomes- membranous sacs containing powerful oxidase
enzymes that use molecular oxygen (O2) to detoxify a
number of harmful or poisonous substances (alcohol and
formaldehyde)
 Disarm dangerous free radicals: highly reactive chemicals
with unpaired electrons that can scramble the structure of
proteins and nucleic acids.
 Convert free radicals into hydrogen peroxide
 Catalase converts excess hydrogen peroxide into water.
 Liver and kidney cells which both are very active in
detoxification
CYTOPLASMIC ORGANELLES
Cytoskeleton- elaborate network of protein structures
extends throughout the cytoplasm.
 Act as cell’s bones and muscles
 Determines cell shape
 Intermediate filaments- help form desmosomes provide internal guy wires to resist pulling forces
 Microfilaments- cell motility and in producing changes
in cell shape
 Microtubles- tubelike, distribution of organelles and are
very important during cell division
CYTOPLASMIC ORGANELLES
Centrioles- paired lie close to the nucleus
Rod-shaped bodies that lie at right angles to
each other
Made up of fine microtubules
Mitotic spindle
CYTOPLASMIC ORGANELLES
Cilia- whip-like cellular extensions that move
substances along the cell surface.
Flagella- sperm tail that helps with movement.
CELL PHYSIOLOGY
Membrane Transport Solution- homogeneous mixture of 2 or more components.
 Solvent- dissolving medium (body has water)
 Solutes- substances that are present in smaller amounts.
 Intracellular fluid- solution containing small amounts of
gases (oxygen and carbon dioxide) nutrients, and salts,
dissolved in water.
 Interstitial fluid- continuously bathes the exterior of our cells
 Selective permeability- means that a barrier allows some
substances to pass through it while excluding others.
PASSIVE TRANSPORT PROCESSES:
DIFFUSION AND FILTRATION
Diffusion- the process by which molecules tend to scatter themselves
throughout the available space.
 The speed of diffusion is affected by the size of the molecules (the smaller
the faster and the warmer the faster).
 Molecules move passively through the membrane if:
 They are small enough to pass through its pores
 They can dissolve in the fatty portion of the membrane.
 Simple diffusion- unassisted diffusion of solutes through the plasma
membrane.
 Lipid-soluble or small enough to pass through the membrane pores.
 Osmosis- diffusion of water through a selectively permeable membrane
 Facilitated diffusion- means for certain needed substances (glucose) to
enter the cell.
FILTRATION
The process by which water and solutes
are forced through a membrane by fluid.
Pushes a fluid from a high pressure to a
low pressure.
Kidneys
Not selective process
ACTIVE TRANSPORT PROCESSES
Solute pumping- similar to facilitated diffusion
Uses ATP to energize its protein carriers
instead of kinetic energy.
Solute pumps pump the ATP to the molecules
Amino acids and some sugars and most ions
Nerve cell transmissions
ACTIVE TRANSPORT PROCESSES
Bulk Transport Exocytosis- out of the cell
 Secretes hormones, mucus, and other cell products
 Packaged before released into a vesicle
 Endocytosis- into the cell
 Released into the cytoplasm.
 Phagocytosis
 Bulk-phase endocytosis- the cell forms a tiny pit and
then its edges fuse around the droplet of extracellular
fluid unlike phagocytes this is routine activity for a cell.
CELL DIVISION
2 major periods: interphase and cell division
Interphase is really metabolic phase not resting
phase.
Events of cell division:
Mitosis: 1st is division of nucleus and 2nd
cytokinesis is division of the cytoplasm
(happens when mitosis is nearly completed)
CYTOKINESIS
Occurs during late anaphase and completes during
telophase.
At the end two daughter cells exist.
 Genetically identical to the mother cell
 Carry out normal cell activity until it is their turn to divide.
 Sometimes the cytoplasm does not divide. This leads to
binucleate or multinucleate cells.
 Fairly common in the liver.
Mitosis gone wild is the basis for tumors and cancers.
METABOLISM AND T3 AND T4 HORMONES
The sum total of the chemical reactions that occur in the
body
T3 and T4 are thyroid hormones that are required for
normal development of brain tissue. Also normal
metabolism of the body.
 Too little you have lack of concentration and focus
Can also cause infertility.
 Too much leads to anxiety disorders.
 Iodine required for normal thyroid activity.