Download Cellular Biology Script Slide 1. For this first unit we start by reviewing

Cellular Biology Script
Slide
1. For this first unit we start by reviewing cells.
2. You may find the cellsalive website on this page a fun and informative site to visit as you review
cellular biology
3. The cell is amazing. Look at all the parts of a cell!
a. The nucleus—the boss
i. See the arrow pointing to pores in the nucleus membrane? The pores are
designed so the DNA can quickly send a message out via mRNA when a gene
activated.
4. Often this message is sent to the ribosomes (those little protein making factories on the rough
endoplasmic reticulum) when a new protein, often enzymes, are needed. The ribosomes get
the message “start stringing together amino acids now…this one first, then this one, then…until
the message “complete” is received and the new enzyme is sent on its way either to the
5. Golgi apparatus (the warehouse and distribution center directing macromolecular traffic ) for
packaging and sending the newly manufactured protein where it is needed.
6. The enzyme is often packaged in secretory vesicles..they may contain lipids, proteins,
glycoproteins, enzymes…what the cell needs. They will break off from the Gogi apparatus and
move to intracellular or extracelluar destinations…or even to the cell surface for release.
7. See the lysosomes—they are the intracellular digestive system…. They can contain over 40
digestive enzymes to break down no longer needed substances such as amino acids, fatty acids,
sugars…so they can be used again--and encapsulate indigestible material stored in residual
bodies. Sometimes high concentrations of lipid will accumulate as residual bodies. “age
pigment or lipofuscin is sometime noted in older individuals on assessment.” Lack of enzymes
(from a genetic defect) can lead to a number of conditions that cause cellular injury or even
death. Pompe disease and Tay-Sacs are rare examples.
8. Gout though is more common example. It is the result of undigested uric acid that accumulates
in the lysosome and actually damages the lysosomal membrane so enzyme can leak out and
cause tissue injury and as you know if you’ve had gout or tx it –severe pain!
9. Wolman disease is a lysosomal acid lipase deficiency that alters the structure of kidneys and
the liver.
10. Peroxisomes—are similar to lysosomes and can remove hydrogen peroxide a free radical that
can severely damage cells. They are also believed to have a role in synthesis of phospholipids
necessary for nerve cell myelination.
11. Sometimes all this runs on the battery power ATP. Certainly all the various pumps (recall the
Sodium and Potassium pump—as an example) need energy. It takes energy to move against a
concentration gradient….the cell needs potassium inside and sodium outside so the battery
making machine the mitochondrion get busy “burning (oxidizing ) glucose (recall the Krebs
cycle!)—key thing to remember is with oxygen you get a lot more batteries then without it! A
cell need lots of batteries –and without oxygen will become injured almost immediately. Will
start to die in a few minutes…Just of interest
12. The cytoskeleton composed of tiny microtubules
13. It can be assembled and reassembled as needed for cell division and other functions.
Breakdown of the cytoskeleton (a genetic alteration that does not allow the cytoskeleton to stay
together) has been implicated in Alzheimer’s Disease.
14. Microtubules are important for cilia and the flagella of sperm. How they all beat together to
move the mucus blanket with its debris out of the respiratory track is still not well know. We do
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know that cigarette smoke (and anesthetic drugs) disrupt the intracellular movement and
cellular motility by their affect on microtubules and microfilaments. Hence the smokers cough
in the morning when cilia begin to function again after hours of no cigarette smoke exposure.
All the above are bathed in cytoplasm which is mostly made up of water and is about ½ the cell
volume. If the sodium levels are too high in the blood the water will move out of the cell
causing cellular dehydration. If sodium levels are too low in the blood water will move into the
cell. This is especially dangerous for the cells of the brain as there is little room for expansion
within the skull.
Everything is “kept inside” so to speak with this amazing membrane called the plasma
membrane. It controls what enters and what exits, and provides a protective barrier for the cell
It is made up of lipids, phospholipids, glycolipids and cholesterol that keep it flexible and only
semi-permeable.
The oily core region doesn’t want water soluble molecules to just enter at will. They need a
carrier to get through the oily core region but oxygen and carbon dioxide which are highly lipid
soluble are allowed to move quickly across the concentration gradient which is nice since this
movement is needed continually in order to generate the energy for life in the mitochondria.
The membrane proteins that you see going in and out of the cell membrane serve as pores,
channels, and carriers. For example, glucose, although it can move freely into nerve cells and
must be available for the brain, does not move across the cell membrane of most other cells. It
needs a door to be opened by insulin and then carried into the cell. The membrane protein is
also involved in cellular communication with its numerous receptors to receive “the text
messages” sent via molecules from other organs and cells.
They also serve as cell surface receptors. The cell can up regulate and down regulate the
number of these receptors when stimulated to do so by chemical messengers. These messages
or cellular chatter are produced based on needs of the cell. As clinicians we are starting to learn
some of the vocabulary of this chatter and have used this knowledge to design medication to
encourage up regulation (metformin). We also have medications to block the reception of the
signals such as ARBs and Beta blockers.
Proteins also play a role in cell adhesion and most importantly serve as markers clearly telling
the immune system this cell is a friend! This is important since the immune system cells are
always on a search and destroy mission looking for foes or abnormal cells that do not display the
friend protein antigen. Interestingly, many proteins are electrically charged and therefore
change their shape and function in the presence of acid/base imbalances or excessive heat.
Because of their multiple functions dysfunction can result in numerous pathologies.
They also actually “fry” when body temperatures reach 109 degrees F or higher. This is not
consistent with life.
WOW—each cell has so many things in common….but what about the specialized cells? How do
they know what to do? What makes them—well special? On to DNA!