Cell Biology

References

mwd — Tue, 23 Jan 2007 17:18:00 +0000

References

Ref_ER_LUMEN: DePierre, J.W.; Dallner, G. Structural Aspects of the membrane of the Endoplasmic reticulum. Biochim. Biophys. Act. 415:411-472,1975

Jennifer J. Smith1, Marcello Marelli1, Rowan H. Christmas1, Franco J. Vizeacoumar2, David J. Dilworth1, Trey Ideker1, Timothy Galitski1, Krassen Dimitrov1, Richard A. Rachubinski2 and John D. Aitchison. Transcriptome profiling to identify genes involved in peroxisome assembly and function. The Journal of Cell Biology, Volume 158, Number 2, July 22, 2002 259-271

Li X, Baumgart E, Dong GX, Morrell JC, Jimenez-Sanchez G, Valle D, Smith KD, Gould SJ. PEX11alpha is required for peroxisome proliferation in response to 4-phenylbutyrate but is dispensable for peroxisome proliferator-activated receptor alpha-mediated peroxisome proliferation. Mol Cell Biol. 2002 Dec;22(23):8226-40.

Sacksteder KA, Jones JM, South ST, Li X, Liu Y, Gould SJ. PEX19 binds multiple peroxisomal membrane proteins, is predominantly cytoplasmic, and is required for peroxisome membrane synthesis. J Cell Biol. 2000 Mar 6;148(5):931-44.

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com

Chapter 2.2: Organelles and Membranes

mwd — Wed, 04 Jan 2006 09:31:00 +0000

2.2.1. Endoplasmic Reticulum (rough/smooth).

2.2.2. Mitochondria.

2.2.3. Cell Membrane/Cell wall.

2.2.5. Golgi apparatus/complex.

2.2.6. Lysosomes.

2.2.7. Peroxisomes.

2.2.8. Cytosol.

2.2.9. Cytoskeleton & Microtubules.

2.2.10. Membrane bound proteins.

2.2.10.1. Protein channel.

2.2.10.2. Protein "pump".

2.2.10.3. Protein receptor.

2.2.10.4. Cell recognition.

2.2.10.5. Globular Proteins.

2.2.11. For plants: Vacuoles

2.2.12. Vesicles

2.2.13. Centrioles.

2.2.14 Chloroplasts

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.

Chapter 2.2.7: Peroxisomes

mwd — Wed, 11 Jan 2006 04:57:00 +0000

Peroxisomes

It used to be thought that peroxisomes are formed by the budding of
smooth Endoplasmic Reticulum (ER). However, now it is thought that they
form through self-assembly. (reference)
The peroxisome is another major source of Oxygen utilization (along with
the mitochondrion). There are specific proteins associated with the
peroxisomes membrane, also there are 3 oxidation enzymes associated with
peroxisomes:

D-amino acid oxidase

Urate Oxidase

Catalase

The enzyme contents vary with various types of cells. One of the main
functions of peroxisomes in liver cells is detoxification. This is
done by the oxidation of substances like:

Alcohol - About 1/2 of the ethanol one drinks is converted to
acetaldehyde by oxidation.

Phenols

Formic acid

Formaldehyde

Why peroxisomes are not like lysosomes.

Peroxisomes are organelles that contain oxidative enzymes, such as D-amino acid
oxidase, urate oxidase, and catalase. They may resemble a lysosome, however,
they are not formed in the Golgi complex. Peroxisomes are distinguished by a
crystalline structure inside a sac which also contains amorphous gray material.
They are self replicating, like the mitochondria. Components accumulate at a
given site and they can be assembled into a peroxisome. They may look like
storage granules, however, they are not formed in the same way as storage
granules.

Peroxisomes function to rid the body of toxic substances like hydrogen
peroxide, or other metabolites. They are a major site of oxygen utilization
and are numerous in the liver where toxic byproducts are going to accumulate.

The peroxisome is made as a phospholipid bilayer, encapsulating oxidative
materials. They would be 'sphere-ish' in shape, not necessarily a
perfect sphere, and sometimes, they may take other shapes. But most
electron micrographs I have seen (2 dimensions) show them as circles.
(As you may be aware, the Cell membrane is also a phospholipid bilayer.)
Peroxisomes have membrane proteins that are critical for peroxisomal function,
to import proteins into their interiors, proliferate or segregate to daughter cells
(reference)
The main differences would be:

1. Types of phospholipids used.

2. Size of the membrane (i.e. peroxisomes are MUCH smaller
than the cell).

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.

Chapter 2.0: Parts of the Cell

mwd — Tue, 03 Jan 2006 20:15:00 +0000

Some interesting things are, what are the organelles with DOUBLE lipid
bilayer membranes?

Nucleus

Mitochondria

Chloroplasts

2.1. Cell/plasma Membrane

2.1.1. Phospholipids

2.1.2. Cholesterol

2.1.3. Semi-permeable/Osmosis

2.1.4. Proteins/channels

2.1.5. Hydrophobic/Hydrophilic

2.1.6. Self-assembly

2.2. Internal Organelles/membranes

2.2.1. Endoplasmic Reticulum (rough/smooth).

2.2.2. Mitochondria.

2.2.3. Cell Membrane/Cell wall.

2.2.5. Golgi apparatus/complex.

2.2.6. Lysosomes.

2.2.7. Peroxisomes.

2.2.8. Cytosol.

2.2.9. Cytoskeleton & Microtubules.

2.2.10. Membrane bound proteins.

2.2.10.1. Protein channel.

2.2.10.2. Protein "pump".

2.2.10.3. Protein receptor.

2.2.10.4. Cell recognition.

2.2.10.5. Globular Proteins.

2.2.11. For plants: Vacuoles

2.2.11.1. Vesicles.

2.2.11.2. Centrioles.

2.2.11.3. Chloroplasts.

2.3. Genetic Material.

2.3.1. Prokaryotes.

2.3.2. Eukaryotes.

2.3.2.1. Nucleus.

2.3.2.2. Nuclear membrane.

2.3.2.3. Nucleolus.

2.3.3. DNA/RNA - what is RNA and DNA?

2.3.4.1. What are codons?

2.3.4. Rna polymerase.

2.3.5. Histones - DNA packing.

2.4. Cytoplasm

2.5. How Energy is supplied: Mitochondria/Chloroplasts

- Glycolysis

Citric acid cycle/Krebs cycle - overview in the UK.

- Electron Transport

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.

Chapter 2.2.6: Lysosomes

mwd — Wed, 04 Jan 2006 10:31:00 +0000

First I think it is important to understand how scientists "see" small
cellular organelles. One way they see these organelles is through staining,
when you stain a organelle or a cell, you will see different characteristics
based on the stain. Another way to 'see' what is there is by separating
the cell by the size and weight of the organelles (through centrification,
basically spinning the contents of the cell around VERY fast in a substance
that allows different layers of 'stuff' depending on its density).

The lysosome is about the same, the lysosome tends to stain
more granular than the peroxisome. A peroxisome will
often have a crystalline structure inside. (like a crystalline
shape inside a sphere).

Lysosomes

The structures vary in size from 0.2 to 2 micrometers in diameter.
The staining reveals a crystal like matrix in spherical vesicles.
The crystalloid matrix is urate oxidase.
These are small organelles containing around 40 enzymes for intercellular
digestion. The lysosome membrane helps to protect the enzymes as much
as it helps protect the cell. This is because the optimal pH for these
enzymes is around a pH of 5. The membrane of the lysosome is again a
lipid bilayer and is thought to have a ATP hydrolysis to pump H+ into
the lysosome to maintain the pH. This also has another affect, that is
free protons. Other small molecules can pass through the lysosome membrane,
but will then become charged by picking up a free proton, then they are
less likely to be able to leave the lysososome.

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.

Chapter 2.2.10: Proteins

mwd — Wed, 04 Jan 2006 09:37:00 +0000

1. Membrane Proteins.

2. Enzymatic Proteins.

3. DNA Binding/regulatory Proteins.

4. Non-membrane transport Proteins.

5. Structural Proteins.

6. Peptides and peptide hormones.

I. Membrane proteins:

One role of proteins in cells is for transport of molecules/ions into or
out of cells. Three methods of doing this are through active, facilitated
or passive transport. Other roles of membrane proteins are in cell recognition,
receptors, cell to cell communication.

Types of Proteins:

Transmembrane Protein:

Globular Protein:

Glyco-protein:
- Glyco-proteins are processed in the Endoplasmic reticulum, and a carbohydrate chain is added on.

A Functional look at Membrane Proteins:

Transport Proteins:

There are two ways that molecules pass through transmembrane proteins:

uniport - which is where one molecule is transported, and
cotransport - where 2 molecules are
transferred.
Also there are two basic types of cotransport:
symport, which is where two molecules
are transported in the same direction and
antiport, where the molecules
are transported opposite directions through the membrane (which will be shown
by the Na - K ATPase pump coming up). Here are the types of transport.

2.1.4.1. Active Transport (these can be either uniport or cotransport):

This transport, which will require energy, is going against
the electro-chemical
gradient. An example of this can be found in the
Na/K ATPase The Sodium-Potassium ATPase pump, this is important especially in the nerves
of all animals. This is commonly used to generate a
membrane potential.

2.1.4.2. Facilitated Transport (these can be either uniport or cotransport):

Facilitated transport is as it sounds, facilitates transport.
This occurs because it moves with the
electro-chemical
gradient.

2.1.4.3. Passive Transport:

Small molecules that are uncharged can move directly through
the membrane in the direction of high concentration to low
concentration. Molecules that have a charge (positive or
negative) it will tend to move to the side of the membrane
that have the opposite electrical potential.

Proteins role in this is through forming channels through
the membrane that facilitate transfer of the molecules
in accordance to the electrical and chemical gradients.

Putting these all together in a membrane is done in the following
example of the Sodium-Potassium
ATPase pump in conjunction with the Potassium leak, and the glucose
symport with Sodium.

Cell Recognition:
Cell recognition occurs through

Cell-Cell Communication:

Receptors:

Enzyme proteins

Binding Proteins:

DNA binding

Non-membrane bound Transport Proteins:

Hormone transport -

Structural Proteins

Peptides and peptide hormones

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.

Chapter 2.1.5: Na _ K ATPase (Sodium-Potassium ATPase pump)

mwd — Wed, 11 Jan 2006 04:35:00 +0000

This is both an example of how Active anti-port and co-transport works
and an example showing part of how nerves and other cells generate a
electrical potential on their membrane surfaces.

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.

Chapter 2.2.1: The Endoplasmic Reticulum

mwd — Wed, 04 Jan 2006 10:11:00 +0000

The Endoplasmic Reticulum (ER) is a very amazing part of the cell! (Well I
guess every part of the cell is amazing if you see all of what it does).
It is responsible for a wide range of tasks! Including the biosynthesis of:
lipids for constructing new membranes, proteins (via ribosomes) and complex
carbohydrates. The ER membrane typically makes up more than half of the total
membrane in the cell and is located between the nucleus and the cytosol and
specifically the golgi apparatus.
This means
that there is 2 membranes between the nucleus and the Golgi Apparatus, the
outside ER membrane and the nuclear membrane (This is because the ER is
continuous with the outer nuclear membrane). However, there are 2 membranes
between the golgi and the ER and there is a LARGE amount of transfer between
the two organelles, which suggests there is probably transport occurring through
transport vesicles (shown below).

The ER is a made up of two phospholipid bilayer membranes.
The enclosed 'sac' is called the ER lumen, the internal space of the ER. The
ER is thought to be a single continuous membrane (Reference). Also there are two types of ER:

Rough ER: Is associated with ribosomes (the dots on its boundaries)
and the membranes tend to be in 'sheets' or flatten sacs called
cisternae.

Smooth ER: Which lacks ribosomes, and is also more of a mesh of
smaller interconnecting tubes.

The Endoplasmic Reticulum:

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.

Chapter 2.2.5: Golgi Apparatus/complex

mwd — Wed, 04 Jan 2006 10:16:00 +0000

The Golgi apparatus is involved in intracellular membrane maintainance.
It modifies products via glycosylation, packages them and vesicles which
transport the product to the proper destination.

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.

Chapter 2.2.2: The Mitochondria

mwd — Wed, 04 Jan 2006 09:53:00 +0000

Mitochondrion is the singular form of mitochondria. The mitochondria
major role is ATP production in the eukaryotic cell. These are mobile
and flexible organelles, although in some cells they tend to stay in
a fixed position. The fixed position is especially true of cells or locations
in cells where there will be a need for a high amount of ATP production, such
as, near flagella or between myofibrils of muscle.
Note this organelle has a double membrane the folded inner membrane is called the Cristae, while the outter membrane is smooth.
Mitochondria are also self-reproducing, they have their own circular DNA, with a slightly modified version of the codons.
This differs with the eukaryote codon table.

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.

Chapter 2.1: Cell Membrane

mwd — Tue, 03 Jan 2006 20:19:00 +0000

2.1.1. Phospholipids

2.1.2. Cholesterol

2.1.3. Semi-permiable/Osmosis

2.1.4. Proteins/channels

2.1.5. Hydrophobic/Hydrophilic

2.1.6. Self-assembly

The phospholipid bilayer which the cell membrane is an example of, is
composed of various cholesterol, phospholipids, glycolipids and
proteins. Below is an example of a simple phospholipid bilayer.

The smaller molecules between the phospholids is Cholesterol which
helps to give rigidity or stability to the membrane. The phospholipids
are the hydrophilic circles with hydrophobic tails. And since most of
the cell and area surrounding the cell is made up of water, these fatty
acid tails always 'push' away from the water. Causing either a bilayer
as above or a 'micelle' which is a single layer circle of phospholipids
with the tails pointing in.

There are different are 10 main types of lipids in cell membranes. Each
type of cell or organelle will have a differing percentage of each
lipid, protein, and carbohydrate. The main types of lipids are:

- Cholesterol

- Glycolipids

- Phosphatidylcholine

- Sphingomyelin

- Phosphatidylethnolamine

- Phosphatydilinositol

- Phosphatidylserine

- Phosphatidylglycerol

- Diphosphatidylglycerol (Cardiolipin)

- Phosphatidic acid

2.1.1. Phospholipids:

Phospholipids are made up of a hydrophilic (likes water)head and a hydrophobic (fears/moves away from water) tail. The head group has a 'special' region that changes between various phospholipids.
This head group will differ between cell membranes [types of cells] or different concentrations of specific 'head groups'. The fatty acid tails call also differ, but there is always one saturated and one unsaturated 'leg' of the tail.

Phospholipids are 2 fatty acids one saturated and one unsaturated
(shown by the double bond) that are linked to a glycerol.

2.1.2. Cholesterol:

I have symbolized cholesterol as:

Cholesterol is a major component of cell membranes and serves many
other functions as well. Cholesterol helps to 'pack' phospholipids in
the membranes, thus giving more rigidity to the membranes. Also
cholesterol serves diverse functions such as: it is converted to
vitamin D (if irradiated with Ultra Violet light, modified to form
steroid hormones, and is modified to bile acids to digest fats.

2.1.3. Semi-permiable/Osmosis

The membranes of cells are a fluid, they are semi-permeable, which means
some things can pass through the membrane through osmosis or diffusion.
The rate of diffusion will vary depending on the its: size, polarity,
charge and concentration on the inside of the membrane versus the
concentration on the outside of the membrane. When something is
permeable it means that something can spread throughout, like (The
perfume is permeating the room.). Here is a list of some molecules
and how they relate to passing through the membrane without assistance,
in other words, through osmosis:

Hydrophobic Molecules:

O2 - Oxygen

N2 - Nitrogen

benzene

Small uncharged Polar Molecules:

H2O - Water

urea

glycerol

C02 - Carbon Dioxide

Large Uncharged Polar Molecules:

Glucose

Sucrose

Ions:

H+ - Hydrogen ion

Na+ - Sodium ion

K+ - Potassium ion

Ca²+ - Calcium ion

Cl- - Chloride ion

Various substances will pass through the membranes at varying rates
through osmosis.

2.1.4. Membrane proteins:

One role of proteins in cells is for transport of molecules/ions into or out of cells. Three methods of doing this are through active, facilitated or passive transport. Other roles are in cell recognition, receptors, cell to cell communication. There is more information on membrane proteins and other proteins in later sections.

2.1.5. Hydrophobic/Hydrophilic

A very simplistic idea of what these characteristics are is:

Hydrophilic and hydrophobic are, respectively, the like and dislike.
Hydrophilic areas of a phospholipid, or a protein are 'attracted' to
water, and hydrophobic regions are repelled by water.

2.1.6. Self-assembly

Self-assembly occurs due to the thermodynamics, if the phospholipids are
in a water (or other polar solution) the tails will want to be 'away'
from the solution. The could all go to the top (like oil on water), or
they could have the tails point toward each other. With the tails
pointing toward each other, this could form 2 different formations.

First would be a micelle which
would like like a ball with the phospholipid heads on the outside and
the tails pointing together like this or in the form of a lipid bilayer:

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com

Chapter 1.1: Introduction to Cell biology

mwd — Tue, 03 Jan 2006 14:57:00 +0000

A. What is a cell - Water, carbon, elements.

B. Size of Cells.

C. What is the difference between elements?

D. What is living?

E. What is interesting about Cell biology?

What is a cell?

Cells are structural units that make up plants and animals, also there many single cell organisms. What cells all have in common is they are small 'sacks' composed mostly of water. The 'sacks' are made from a phospholipid bilayer (which will be explained in detail in chapter 2). The membrane is semi-permeable (allowing some things to pass in or out of the cell and blocking others), there are also other methods of transport that we will get into later.

So what is in a cell? The cell as we mentioned is a fluid like membrane that surrounds the contents of the cell. Each component will be discussed in more detail later.

Cells are 90% fluid (cytoplasm) which consists of free amino acids, proteins, glucose, and numerous other molecules. The cell environment (ie. the contents of the cytoplasm, and the nucleus, as well as, they way the DNA is packed) affect the gene expression/regulations, and thus are VERY important parts of inheritance, below are approximations of other
components:

2% Others - Phosphorus (P), Sulphur (S), etc.

As far as molecules that make up the cell:

A picture of a cell:

What is inside the cell is the cytoplasm which is:

Cytosol - a lot of water - it is everything except the organelles.; Organelles (which also have membranes) in 'higher' eukaryote organisms:

Nucleus (in eukaryotes) - where genetic material (DNA) is located, RNA is transcribed.

Endoplasmic Reticulum (ER) - Important for protein synthesis. It is a transport network for
molecules destined for specific modifications and locations.
There are two types:

Rough ER - has ribosomes, and tends to be more in 'sheets'.

Smooth ER - Does not have ribosomes and tends to be more of a tubular network.

Ribosomes - half are on the Endoplasmic Reticulum, the other half are 'free' in the cytosol, this is
where the RNA goes for translation into proteins.

Golgi Apparatus - important for glycosylation, secretion.

Lysosomes - Digestive sacks - the main point of digestion, these are only found in animal cells.

peroxisomes - Use oxygen to carry out catabolic reactions, in both plant and animals.

Microtubules - made from tubulin, and make up centrioles,cilia,etc.

Cytoskeleton - Microtubules, actin and intermediate filaments.

Mitochondria - convert foods into usable energy. (ATP production) A mitochondrion does this through aerobic respiration. They have 2 membranes, the inner membranes shapes differ between different types of cells, but they form projections called cristae. The mitochondrion is about the size of a bacteria, and it carries its own genetic material and ribosomes.

Vacuoles - More commonly associated with plants. Plants commonly have large vacuoles.; Found in Plants and not in animals:
Plastids - minute granules found in plant cells which have their own membrane, ribosomes
and DNA. The most commonly know is the chloroplast.
Chloroplasts - convert light/food into usable energy. (ATP production)

Cell Wall - found in prokaryotic plants and it provides structural support and protection.

Size of Cells

Eukaryotes are typically 10 times the size of prokaryotic cells. Plant cells are on average some of the largest cells, which may be because of the large water filled vacuoles in some plant cells.

So, you ask, what are the relative sizes of biological molecules and cells?

These are all approximations:

Small

0.1 nm (nanometer) diameter of a hydrogen atom

0.8 nm Amino Acid

2 nm Diameter of a DNA Alpha helix

4 nm Globular Protein

6 nm microfilaments

10 nm thickness cell membranes

200 nm (200 to 500 nm) Lysosomes

200 nm (200 to 500 nm) Peroxisomes

1 um (micrometer)

(1 - 10 um) the general sizes for Prokaryotes

1 um Diameter of human nerve cell process

2 um E.coli - a bacterium

3 um Mitochondrion

5 um length of chloroplast

6 um (3 - 10 micrometers) the Nucleus

9 um Human red blood cell

10 um

(10 - 30 um) Most Eukaryotic animal cells

90 um Amoeba

100 um Human Egg

1 mm (1 millimeter, 1/10th of a centimeter)

1 mm Diameter of the squid giant nerve cell

2 mm Diameter of a frog egg

Large

What is the difference between elements/compounds?

The various elements that make up the cell are:

2% Others - Phosphorus (P), Sulphur (S), etc.

The difference between these elements is their respective weights, electrons and in general their properties. A given element can only have so many other atoms attached. For instance carbon (C) had 4 electrons in its outer shell and thus can only bind 4 atoms, Hydrogen only has 1 electron and thus can only bind to one other atom. An example would be Methane which is CH4. Oxygen only has 2 free electrons, but will some times form a double bond, which is a 'ester' (which typically smell good or bad).


   Methane    Water   Methanol (Methyl Alcohol)
   -------    -----   -------------------------
      H       H   H      H
      |        \ /       |
    H-C-H       O      H-C-O-H
      |                  |
      H                  H

As far as molecules that make up the cell:

Here is a list of Elements, symbols, weights and biological roles.



ELEMENT (Symbol)Atomic Weight   Biological role

Calcium   (Ca)  40.1            Bone; muscle contraction
Carbon    (C)   12.0            Constituent(backbone) of
                                organic molecules
Chlorine  (Cl)  35.5            Digestion and photosynthesis
Copper    (Cu)  63.5            Part of Oxygen-carrying
                                pigment of mollusk blood.
Fluorine  (F)   19.0            For normal tooth enamel
                                development
Hydrogen  (H)    1.0            Part of water and all organic
                                molecules
Iodine    (I)  126.9            Part of thyroxine (a hormone)
Iron      (Fe)  55.8            Hemoglobin, oxygen caring
                                pigment of many animals
Magnesium (Mg)  24.3            Part of chlorophyll, the photo-
                                synthetic pigment; essential
                                to some enzymes.
Manganese (Mn)  54.9            Essential to some enzyme actions.
Nitrogen  (N)   14.0            Constituent of all proteins and
                                nucleic acids.
Oxygen    (O)   16.0            Respiration; part of water; and
                                in nearly all organic molecules.
Phosphorus(P)   31.0            High energy bond in ATP.
Potassium (K)   39.1            Generation of nerve impulses.
Selenium  (Se)  79.0            For the working of many enzymes.
Silicon   (Si)  28.1            Diatom shells; grass leaves.
Sodium    (Na)  23.0            Part of Salt; nerve conduction
Sulfur    (S)   32.1            Constituent of most proteins.
                                Important in protein structure:
                                Sulfide bonds are strong.
Zinc      (Zn)  65.4            Essential to alcohol oxidizing
                                enzyme.

What is living?

This is a topic that is been of many long discussions and it depends on your initial definitions. Some definitions are:

1. The quality that distinguishes a vital and functional being from a; dead body or purely chemical matter.
: 2. The state of a material complex or individual characterized by the
capacity to perform certain functional activities including metabolism,
growth, and reproduction.
: 3. The sequence of physical and mental experiences that make up the
existence of an individual.

Under these varying definitions life may or may not include a virus that is only 'alive' if it can insert its genetic material into a living cell. To me live is the substance that can react to its environment, grow, improve and reproduce. To have less of a definition would include to much to have more would not include some cells.

What is interesting about Cell biology?

What makes cell biology particularly interesting is that there is so much that is not understood. Cells are a complex system in and of themselves. And when you add to a individual cell its environment, whether that is the single celled organism or multicellular, there is a complex web reactions. One organism, like the human, can have the same genetic material in every cell, yet, there are over 200 types of cells in the human, that are different shapes, sizes and and carry out very different functions. And ALL of these cells were developed from 1 (one) cell.

Food for thought - to be discussed in the final chapters.

Biology is the understanding of complex systems. Which is how in basic terms how we get a functional system when things tend to move toward lower energy states. For example, if you took food scraps and left them in a compost pile they cells and proteins would break down to more basic compounds. The system maintains and generates new proteins. Without constantly breaking down and building new proteins, enzymes, DNA, cells, the larger system would
break down.

Complexity - A cell is more like a balanced eco-system then a simple unit.

inter-relations of cells - between cells in multi-cellular or organisms
there is communication, exchanges of information and needed resources.
(like a red blood cell bringing oxygen, other cells producing a hormone,
or one bacterium transferring a plasmid to another).

Intra-relations of a cell - Within a cell organelles, gene expression
work together to maintain the cell.

The cell and its environment - The environment around the cell influences
and is required at times how, when or if a gene is expressed. It is not
as simplistic as the 'gene' causes A or B, it is the entire cell, the cells
around and the larger environment.

Its ability to Live and reproduce.

Its ability to grow and change.

It is what makes up you and the food you eat.

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.

Chapter 1.2: Types of Cells

mwd — Tue, 03 Jan 2006 19:38:00 +0000

Chapter 1.2: Types of Cells

The major differences between Prokaryotic and Eukaryotic cells are that prokaryotes don't have a nucleus and rarely have membrane bound organelles, (the only exception I have heard of is bacteria with vacuoles). The both do have DNA for genetic material, have a exterior membrane, have ribosomes, accomplish similar functions, and are very diverse. For instance, there are over 200 types of cells in the human body, that very greatly in size, shape, and function.

Prokaryotes:

Prokaryotes are cells without a nucleus. They have genetic materials but are not enclosed within a membrane. These include bacteria and cyanophytes. The genetic material is a single circular DNA and is contained in the cytoplasm, since there is no nucleus. Recombination happens through transfers of plasmids (short circles of DNA that pass from one bacterium to another). They do not engulf solids nor do they have centrioles or asters. There are pictures of two prokaryotes below. Prokaryotes have a cell wall made up of peptidoglycan.

Eukaryotes:

These are cells with a nucleus, this is where the genetic material is surrounded by a membrane much like the cells membrane. Eucaryotic cells are found in humans and other multicellular organisms (plants and animals) also algae, protazoa. They have both a cellular membrane and a nuclear membrane, also the genetic material forms multiple chromosomes,
that is linear and complexed with proteins that help it 'pack' and is involved in regulation.

Eukaryotes are composed of both plant and animal cells. Plants vary from animal cells in that they have large vacuoles, cell wall, chloroplasts, and a lack of lysosomes, centrioles, pseudopods, and flagella or cilia. Animal cells do not have the chloroplasts, and may or may not have cilia, pseudopods or flagella, depending on the type of cell.

Please send questions/comments/suggestions to: Mark Dalton at markwdalton@gmail.com.

Title page

MedRounds Publications — Tue, 03 Jan 2006 14:30:00 +0000

TEXTBOOK OF CELL BIOLOGY

Second Edition

Mark Dalton

Published and distributed by MedRounds Publications, Inc.

All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording, or any information storage and retrieval system, without permission in writing from the publisher.

Published in The United States of America.

[NEXT]

About this Course - written for beginners to biology

mwd — Tue, 03 Jan 2006 14:23:00 +0000

This course is meant to help those that are interested in learning
about Cell Biology. This course material is not for credit, unless
you have made some other arrangements or this is being used as a
supplement in a 'for credit' course.

This course is to help the beginner to biology to understand cell biology
in simple term. This textbook is an informal introduction to biology.

Chapters will be added as time allows to view the original course:
http://www.ccgb.umn.edu/~mwd/cell.html

If you have questions, corrections or comments feel free to email me at:
markwdalton@gmail.com