Organelles

CELL ORGANELLES

An organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer.

- Largest organelle- Contains all of a eukaryotic

cell’s DNA- Serves 2 important

functions ;1. Directs all activity in the

cell2. controls growth & reproduction of the cell

Components of the Nucleus

Nuclear envelope

Nucleoplasm

Nucleolus

Chromatin

Chromosome

Nuclear Envelope

Membrane of the nucleus

Consist of two lipid bilayers folded together as a single membrane

Different kinds of membrane proteins are embedded in the two lipid bilayers. Some are receptors and transporters.

Fibrous proteins that attach to the inner surface of the nuclear envelope anchor DNA molecules and keep them organized. During cell division, these proteins help the cell parcel out the DNA into its offspring.

Chromosomes

Chromatin is the name for all of the DNA, together with its associated proteins, in the nucleus.

Each molecule of DNA, together with its many attached proteins, is called a chromosome.

Do you know that chromosomes change in appearance over the lifetime of a cell ?

MITOCHONDRIA

The energy mechanism !!

We all know that every action requires energy This energy is stored in the form of ATP.

(ADENOSINE It is produced in the mitochondria through the process of oxidative phosphorylation.

THEY ARE FOUND IN HIGH CONCENTRATIONS IN THE MUSCLE CELLS THAT REQUIRE MORE ENERGY.

Although the primary function of mitochondria is to produce energy, they also play an important role in the metabolism and synthesis of certain other substances in the body

NEWSPAPER ARTICLE 1-Scientists at the University of California in Davis (UCD) demonstrate in a new study that children with autism are also highly likely to suffer from defects in their mitochondria, which are structures generally refer to as the “power plants” of the cell. 

JUST LIKE HOW THE BRAIN IS THE 2ND –LARGEST ENERGY CONSUMING ORGAN it stands to reason that not providing sufficient FUEL(ENERGY) for neurons to function properly may lead to impaired capabilities and AUTISM is the physical CAUSE Of this neural “starvation.”

According to this report Children with mitochondrial diseases may present exercise intolerance, seizures and cognitive decline, among other conditions

evidence of mitochondrial dysfunction and changes in mitochondrial DNA were detected in the blood of these young children with autism.

CURING MIROCHONDRIAL DEFECTS !!!!!!

TO DIAGONISE mitochondrial dysfunction WE NEED TO CARRY OUT A MUSCLE BIOPSY !

ARGHHHHHHHHHHHH WHATS THAT ! ????????????????

 a muscle biopsy is a procedure in which a piece of muscle tissue is removed from an organism and examined microscopically. A biopsy needle is usually inserted into a muscle, where a small amount of tissue remains

A muscle biopsy can lead to the discovery of problems with a nervous system, which leads us to knowing the problems that has occurred in our body due to the defects in the mitochondria.

The Endomembrane System

A series of interacting organelles between the nucleus and the plasma membrane

Main function : Make lipids, enzymes, and proteins for secretion or insertion into cell membranes. Also destroys toxins and recycle wastes.

Endoplasmic Reticulum (ER)

An extension of the nuclear envelope

Forms a continuous compartment that folds over and over into flattened sacs and tubes

There are two types ;

1. Rough ER

2. Smooth ER

Vesicles

Small, membrane-enclosed, sac-like organelles. Form in great numbers, in a variety of types.

Transports substances from one organelle to another, or to and from the plasma membrane.

Others, like peroxisomes, contains enzymes that digest fatty acids and amino acids. Can also inactivate hydrogen peroxide, a toxic by-product of fatty acid breakdown.

Later, enzymes in the peroxisomes convert hydrogen peroxide to water and oxygen or they use it in reactions that break down alcohol and other toxins.

DO YOU KNOW?

Drink alcohol, and the peroxisomes in your liver and kidney cells degrade nearly half of it !!

Peroxisomes

• Organelle with multifaceted functions

• Responsible for a multitude of metabolic functions within cells.

• They contain over 50 different functional enzymes capable of

forming highly variable structures adapted to the specific needs

of the organism.

• One of the most important features of peroxisomes is the spatial

isolation (compartmentalization) of metabolic pathways in which

poisonous hydrogen peroxide is formed.

• Its destruction therefore is one of the most important functions

of the peroxisomes.

• Because hydrogen peroxide is harmful to the cell, peroxisomes also contain the enzyme catalase, which decomposes hydrogen peroxide either by converting it to water or by using it to oxidize another organic compound.

• A variety of substrates are broken down by such oxidative reactions in peroxisomes, including uric acid, amino acids, and fatty acids.

• The oxidation of fatty acids is a particularly important example, since it provides a major source of metabolic energy. In animal cells, fatty acids are oxidized in both peroxisomes and mitochondria, but in yeasts and plants fatty acid oxidation is restricted to peroxisomes.

Assembly of Peroxisomes

Peroxisomal disorders

Illnesses due to peroxisomal defects are usually fatal

Zellweger Spectrum

So severe that the patients die during infancy

PROTEIN SYNTHESIS MECHANISM – THE RIBOSOMES

Ribosomes are organelles that consist of RNA and proteins. They are responsible for assembling the proteins of the cell.

Depending on the protein production level of a particular cell, ribosomes may number in the millions.

The protein making mechanism A ribosome is a component of cells that

assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule.

THE CENTRAL DOGMA OF BIOLOGY – we learned thIs ! REMEMBER !!!!

Diamond blackfan Anemia

Diamond Blackfan anemia (DBA) is an inherited red cell aplasia caused by mutations in one of several r-proteins. 

One of the proteins would be the RPS19 protein.

The RPS19 protein is involved in the production of RIBOSOMES. As such, loss of RPS19 function would be predicted to affect translation and Protein biosynthesis and have a much broader impact.

Disease features may be related to the nature of RPS19 mutations.

The disease is characterized by dominant inheritance, and therefore arises due to a partial loss of RPS19 protein function

Lysosomes

Vesicles that contain powerful digestive enzymes.

Serve as waste disposal and recycling centers

Enzymes inside them break large molecules into smaller subunits that the cell can use as building material or eliminate.

Different kinds of molecules are broken down by different lysosomal enzymes

Lysosome malfunction

In some people, a genetic mutation causes a deficiency or malfunction in one of the lysosomal enzymes

As a result, molecules that would normally get broken down accumulate instead.

Tay-Sachs Disease

Enzyme responsible for ganglioside break-down misfolds and is destroyed

Usually, affected infants seem normal for the first few months

Symptoms begin to appear as ganglioside accumulate higher and higher levels inside their nerve cells

Within 3 to 6 months, the child becomes irritable, listless and may have seizures. Blindness, deafness and paralysis follow.

Affected children usually die by the age of 5

Treatment

Options for treatment are still ongoing.

Potential therapies involve blocking ganglioside synthesis or using gene therapy to deliver a normal version of the missing enzyme to the brain.

All treatments are still considered experimental, and Tay-Sachs is still incurable

Golgi apparatus

it was identified in 1898 by the Italian physician Camillo Golgi, after whom the Golgi apparatus is named.

It processes and packages proteins after their synthesis and before they make their way to their destination; it is particularly important in the processing of proteins for secretion.

Due to its fairly large size, the Golgi apparatus was one of the first organelles to be discovered and observed in detail.

Interesting facts

Due to its fairly large size, the Golgi apparatus was one of the first organelles to be discovered and observed in detail.

Golgi apparatus during mitosis

In animal cells, the Golgi apparatus will break up and disappear following the onset of mitosis or cellular division. During the telophase the Golgi apparatus reappears; however, it is still uncertain how this occurs.

Science news article : Artificial Golgi may provide new insight into key cell structure

Scientists in new york and north carolina have reported to have assembling the first functioning prototype of an artificial golgi organelle.

This key structure inside the cell helps to process and package hormones , enzymes and other substances that allow the body to function normally.-hence it works exactly like the real golgi apparatus in our body.

This lap-on-a-chip device could lead to a faster and safer method in producing heparin.

WHAT IS HEPARIN ? I WILL EXPLAIN !!!

CONTINUING….

This device ahs also been tested in labs and it has said to have quickly and efficiently produced heparin.

It did so in as assembly line fashion which was tested using a combination of enzymes, sugars and other raw materials.

During this experiment it was shown that this device has a strong clot fighting potential.

It is believed that in the future, In the case of an golgi apparatus defect in an individual this “artificial golgi” could lead to a faster and safer method for producing heparin.

Plastids

Membrane-enclosed organelles that function in photosynthesis or storage in plants and algal cells.

Common types ; chloroplasts, chromoplasts and amyloplasts

Chloroplasts are found in photosynthetic cells of plants and many protists.

Credits

ARCHPEDIATRICS.com

http://www.ismrd.org/the_diseases/storage_in_lysosomal_diseases

http://www.mun.ca/biology/scarr/iGen3_04-05.html

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2829960/