Organelles

Ribosomes:
>made of rRNA and protein.
>consists of large(60Svedberg) that is synthesized in nucleolus and small(40Svedberg) that is synthesized in nucleus.
>assembled in nucleus and transported to cytoplasm.

Polysomes: ribosomes often form polysomes which consist of a single mRNA that is being translated by several ribosomes at same time.

Types of Ribosomes
1)Free polysomes:-the sites for the synthesis for protein destined for the nucleus,peroxisomes,or mitochondria.
2)Membrane associated polysomes:-site of synthesis of secretory proteins,membrane protein and lysosomal enzymes.

Endoplasmic Reticulum:
>two forms smooth endoplasmic reticulum(SER) and rough endoplasmic reticulum(RER).

1)Smooth endoplasmic reticulum(SER):
>it's a network of membranous sacs.vesicles and tubules continuous with RER.
>contains enzymes involved in the biosyntheseis of triglycerides,phospholipids and sterols.
Functions of SER:
>detoxification reaction, making componds water solubles by steroids synthesis,hydroxylation reactions and conjugation reaction.
>glycogen degradation and gluconeogenesis:removal of phosphate group from glucose-6-phosphate by enzyme glucose-6-phosphatase.
>reaction in lipid metabolism.
>sequestration and release of clcium reaction.

2)Rough endoplasmic reticulum(RER):
>lipid bilayer continuous with outer nuclear membrane.
>cisternae have studded with ribsomes on the cytoplasmic side.
>RER ssynthesizes proteins so are very prominent in cells that are specialized in synthesis of proteins.

Golgi Apparatus:

>consists of disc-shaped smooth cisternae that are assembled In stacks (dictyosomes).
>have diameter of approximately 1nmicrometer and associated with numerous small
membrane-bound vesicles.
>Golgi apparatus has two distinct faces: . The cis (forming) face is associatedwith the RER. . The trans (maturing) face is often oriented toward the plasma membrane. The transmost region is a network of tubular structures known as the trans-Golgi network.

Functions of Golgi apparatus:
>Proteins and Lipids-The Golgi apparatus is the site of post-translational modification and sorting of newly synthesized proteins and lipids.
>Glycoproteins-Further modification of the carbohydrate moiety of glycoproteins produces complex and
hybrid oligosaccharide chains. This determines which proteins remain in the Golgi apparatus
or leave the Golgi apparatus to become secretory proteins, lysosomal proteins, or part of the
plasma membrane. Two diseasesare caused by a breakdown in this process,I-cell disease and
hyperproinsulinemia.

Lysosomes:

>spherical membrane-enclosed organelles that contain enzymes required for intracellular digestion.

>Lysosomes consist of two forms:
1)Primary Iysosomes:
>formed by budding from the trans side of the Golgi apparatus.
2)Secondary Iysosomes are formed by the fusion of the primary lysosome with the substrate
to be degraded.
>Lysosomes contain approximately 60 hydrolytic enzymes.
These include nucleases for degrading DNA and RNA, lipases for degrading lipids, glycosidases for degrading glycoconjugates (glycoproteins,proteoglycans, and glycolipids), proteases and peptidases for degrading proteins, and a variety of phosphatases.All lysosomal enzymes are acid hydrolases, with optimal activity at a pH of approximately 5.0.The synthesis of the lysosomal hydrolases occurs in the RER; the hydrolases are transferred to the Golgi apparatus, where they are modified and packaged into lysosomes.
Diseases caused by lysosomes are:

Peroxisomes(microbodies):

>single and spherical membrane-limited organelles(0.15-0.5 μm in diameter).
>contains a number of enzymes that form hydrogen peroxide(can damage to cell) which is immediately broken down by catalase.that oxidizes various potentially toxic molecules as well as prescription drugs, particularly in the large and abundant peroxisomes of liver and kidney cells.

>functions of peroxisomes:

• synthesis and degradation of hydrogen peroxide
• ß -oxidation of long-chain fatty acids 
• bile acid and cholesterol synthesis

diseases associated with peroxisomes include:

• zellweger syndrome
• X-chromosome-linked adrenoleukodystrophy
• hyperpipecolatemia.

Mitochondria:

>a double membrane enclosed organelles that have enzymes for ATP production

>0.5–1 μm in diameter and 1-10μm in length

>it contains its own DNA (double stranded circular), and make some of their own protein

Outer membrane:

it is seive like membrane that contains many transmembrane protein Porins that form channels through which small molecules (<5000 daltons) readily pass to enter the intermembrane space from the cytoplasm.

Inner membrane:

it has numerous infoldings called cristea that increase the total surface area.they contain the enzymes for electron transport and oxidative phosphorylation.the number of mitochondria and the number of cristea per mitochondria are proportional to the metabolic activity activity of the cells in which they reside.

Matrix is enclosed by inner membrane that contains

• dehydrogenases
• a double stranded DNA genome
• RNA, proteins and ribosomes
• intramitochondrial granules.