27 Aug. 2012 Organelles.ppt 1

Cytoplasmic Organelles

Organized units of the cytoplasm

27 Aug. 2012 Organelles.ppt 2

Cytoplasmic Organelles

• Mitochondrion (-a)• Ribosomes• Endoplasmic

reticulum (ER)• Golgi apparatus• Lysosomes

• Peroxisomes• Cytoskeleton• Centrioles• Secretory vesicles• Cilium, cilia• Nucleus

27 Aug. 2012 Organelles.ppt 3

Mitochondrion

• Generates most ATP– "power plant of the cell"

• Double membrane– outer smooth, sausage-

shaped

– inner folded with enzymes

• Contains own DNA, probably evolved from symbiotic bacteria

27 Aug. 2012 Organelles.ppt 4

Endoplasmic reticulum (ER)

• Network of membranes enclosing spaces (cisternae) separate from rest of cytosol.

27 Aug. 2012 Organelles.ppt 5

Endoplasmic reticulum (ER)

• Rough ER – Associated with

ribosomes – Production of

proteins for membranes or export (exocytosis, secretion).

27 Aug. 2012 Organelles.ppt 6

Endoplasmic reticulum (ER)

• Smooth ER – NO ribosomes, membranes with integral

proteins,– Lipid metabolism & synthesis including

steroid hormones,– Absorption & transport of fats,– Enzymatic detoxification of drugs,

pesticides, etc. (natural & artificial),– Hydrolysis of stored glycogen to glucose,– Storage of Ca+2 ions in muscle cells.

27 Aug. 2012 Organelles.ppt 7

Ribosomes• Very tiny

– invisible under light microscope

• Dense specks of ribosomal RNA

• Free in cytoplasm or membrane-bound (ER)

27 Aug. 2012 Organelles.ppt 8

Ribosomes

• Sites of protein synthesis – mRNA specifies sequence of amino acids

– some proteins packaged in vesicles by ER

27 Aug. 2012 Organelles.ppt 9

Golgi apparatus

• Series of flat membranous sacs

• Modifies, concentrates, & packages proteins for secretion, exocytosis

• Movement to plasma membrane

• Production of lysosomes.

27 Aug. 2012 Organelles.ppt 10

Lysosomes

• Membranous bags of digesting enzymes,

• Destroy particles taken in by endocytosis and phagocytosis

• Remove and destroy worn out organelles

• Removal of excess cells & tissues– "cell suicide"

• Removal of bone matrix to release Ca+2

27 Aug. 2012 Organelles.ppt 11

Peroxisomes

• Resemble lysosomes, but not from Golgi apparatus

• Enzymes oxidize toxins and remove free-radicals.

27 Aug. 2012 Organelles.ppt 12

Cytoskeleton

• Protein "rods," filaments, and tubes running through cytosol

• Maintain or change shape of cell

• Move organelles

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Centrioles

• Clusters of microtubules, usually paired near nucleus– Organize mitotic spindle

– Bases (“motors”) of cilia and flagella

27 Aug. 2012 Organelles.ppt 14

Secretory vesicles

• Packages of chemicals for export (exocytosis)– hormones

– digestive enzymes

– sweat

– mucus

27 Aug. 2012 Organelles.ppt 15

Cilium, cilia

• Short whip-like “appendage”– move material past

cell

– linings of trachea & bronchi

• similar to flagellum (longer) on sperm cell

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Nucleus

• Enclosed in nuclear envelope

• Residence of chromosomes, DNA

• Active in synthesis & export of RNA

• Directs protein synthesis, development of cell