Organelles – Part IOrganelles – Part I

OrganellesOrganelles

• Organelles are ‘tiny organs.’Organelles are ‘tiny organs.’

– Organs are to humans as organelles Organs are to humans as organelles are to cells.are to cells.

NucleusNucleus

• Function:Function:– The nucleus is the cell’s genetic The nucleus is the cell’s genetic

control center.control center.• Stores DNAStores DNA• Makes RNA Makes RNA • Makes ribosomes Makes ribosomes • Directs the synthesis of proteinsDirects the synthesis of proteins

NucleusNucleus

• Structure:Structure:– The nucleus has 3 parts:The nucleus has 3 parts:

• It is surrounded by the It is surrounded by the nuclear envelope nuclear envelope (membrane)(membrane) that has tiny pores that has tiny pores which which material can pass into and out of the nucleus.material can pass into and out of the nucleus.

• Inside it contains Inside it contains – DNADNA

» When DNA is spread out it is called When DNA is spread out it is called chromatinchromatin..» When DNA is coiled up it is called When DNA is coiled up it is called

chromosomeschromosomes..– The The nucleolusnucleolus, which appears as a dark spot inside , which appears as a dark spot inside

the nucleus, manufactures ribosomes.the nucleus, manufactures ribosomes.

NucleusNucleus

• Structure:Structure:– The nucleus has 3 parts:The nucleus has 3 parts:

• Inside it contains Inside it contains – DNADNA

» When DNA is spread out it is called When DNA is spread out it is called chromatinchromatin..» When DNA is coiled up it is called When DNA is coiled up it is called

chromosomeschromosomes..

NucleusNucleus

• Structure:Structure:– The nucleus has 3 parts:The nucleus has 3 parts:

– The The nucleolusnucleolus, which appears as a dark spot inside , which appears as a dark spot inside the nucleus, manufactures ribosomes.the nucleus, manufactures ribosomes.

NucleusChromatin

Nucleolus

Pore

Ribosomes

Roughendoplasmicreticulum

Two membranesof nuclearenvelope

RibosomesRibosomes

• Function:Function:– Ribosomes manufacture proteins based on Ribosomes manufacture proteins based on

instructions they get from the DNA in the instructions they get from the DNA in the nucleus.nucleus.

• Structure:Structure:– Ribosomes are Ribosomes are small spherical structures.small spherical structures.– They They float in the cytoplasmfloat in the cytoplasm OR are OR are connected to connected to

the rough ERthe rough ER..– They are composed of proteins & RNA.They are composed of proteins & RNA.

RibosomesRibosomes

Endoplasmic Reticulum (ER)Endoplasmic Reticulum (ER)

• There are two types of ER:There are two types of ER:– Smooth ERSmooth ER– Rough ER Rough ER

Smooth ERSmooth ER

• Function:Function:– The smooth endoplasmic reticulum has a variety of The smooth endoplasmic reticulum has a variety of

functions:functions:• Synthesizes lipids Synthesizes lipids • Processes toxins and drugs in liver cellsProcesses toxins and drugs in liver cells• Stores and releases calcium ions in muscle cellsStores and releases calcium ions in muscle cells

• Structure:Structure:– Smooth endoplasmic reticulum is composed of Smooth endoplasmic reticulum is composed of

flattened sacs that often extend throughout the flattened sacs that often extend throughout the entire cytoplasmentire cytoplasm

Rough ERRough ER

• Function:Function:– The rough ER has three functions: The rough ER has three functions:

• Synthesis of proteins (in the attached ribosomes)Synthesis of proteins (in the attached ribosomes)• Modification of proteins.Modification of proteins.• Packing of proteins.Packing of proteins.

• Structure:Structure:– Rough endoplasmic reticulum is the same as Rough endoplasmic reticulum is the same as

the smooth but it is dotted with ribosomes the smooth but it is dotted with ribosomes which make it bumpy.which make it bumpy.

Golgi Apparatus (Golgi Golgi Apparatus (Golgi Bodies)Bodies)

• Function:Function:– They receive and modify ER products They receive and modify ER products

then modify, sort, package and ship them then modify, sort, package and ship them to other organelles or the cell surface.to other organelles or the cell surface.

• Structure:Structure:– The Golgi apparatus looks like stacks of The Golgi apparatus looks like stacks of

membranous sacs.membranous sacs.

LysosomesLysosomes

• Function:Function:– They contain enzymes that break down:They contain enzymes that break down:

• FoodFood• Damaged organellesDamaged organelles• Bacteria with which they fuse. Bacteria with which they fuse.

• Structure:Structure:– Lysosomes are made by the Golgi Apparatus.Lysosomes are made by the Golgi Apparatus.– They are tiny spheres of enzymesThey are tiny spheres of enzymes

Interesting Facts…Interesting Facts…

• Abnormal lysosomes can cause fatal Abnormal lysosomes can cause fatal diseases.diseases.

• When a cell is damaged the nucleus When a cell is damaged the nucleus sends a message to the lysosome telling sends a message to the lysosome telling it to explode – the enzymes inside eat it to explode – the enzymes inside eat the cell – for this reason we also call the cell – for this reason we also call lysosomes ‘suicide sacs’lysosomes ‘suicide sacs’

Huntingdon’s diseaseHuntingdon’s disease

Pompe’s diseasePompe’s disease

Tay-sachs diseaseTay-sachs disease

VacuolesVacuoles

• Function:Function:– Vacuoles can do all kinds of things.Vacuoles can do all kinds of things.

• They can contain pigment (color)They can contain pigment (color)• They can contain poison.They can contain poison.• They have contain food or water.They have contain food or water.

– Plants have Plants have central vacuolescentral vacuoles that function store large that function store large amounts of wateramounts of water

• Structure:Structure:– Vacuole is the general term given to any other Vacuole is the general term given to any other

membrane sac in the cell.membrane sac in the cell.