The Endomembrane System. A series of membranes found in the interior of a eukaryotic cell. It...

The Endomembrane SystemThe Endomembrane System

The Endomembrane SystemThe Endomembrane System

A series of membranes found in the interior of a eukaryotic cell. It divides the cell into compartments, channels the passage of molecules through the interior of the cell and provides surfaces for the synthesis of lipids and some proteins.

The Endomembrane SystemThe Endomembrane System

One of the fundamental distinctions between eukaryotes and prokaryotes.

The Endomembrane SystemThe Endomembrane System

1. Nuclear Envelope

2. Endoplasmic reticulum (ER)

3. Golgi Apparatus

4. Vesicles (Vacuoles)

Nuclear EnvelopeNuclear Envelope

• Double membrane

• Pores permit exit ofribosomal subuints

• Separates nucleoplasm from cytoplasm

Endoplasmic ReticulumEndoplasmic Reticulum

System of membrane channels continuous with outer membrane of the nuclear envelope.

Rough ER is:Rough ER is:

Contiguous with the outer membrane of the nuclear envelope.

Studded with ribosomes on the cytoplasm side.

Function of Rough ERFunction of Rough ER

Protein synthesis and modification.

Function of Rough ERFunction of Rough ER

1. Protein synthesis and modification.2. Membrane Synthesis3. Distributes Transport Vesicles

Destinations of Rough ER Destinations of Rough ER ProteinsProteins

• Exported from the cell• Sent to lysosomes or vacuoles• Embedded in plasma membrane

Smooth ERSmooth ER

Continuous with rough ER

No ribosomes (hence smoothsmooth)

Function of smooth ERFunction of smooth ER

1. Synthetic processesPhospholipidsPhospholipidsSteroidsSteroidsFatty acidsFatty acids

2. Forms transport vesicles3. Stores Calcium4. Detoxifies poisons

Golgi ApparatusGolgi ApparatusDelivery System Of the CellDelivery System Of the Cell

Discovered in 1898Discovered in 1898

NamedFor

Camillo Golgi

Golgi ApparatusGolgi Apparatus

• Stack of 3-20 slightly curved saccules.

• 1 to few (protists)• 20 or more - animal cells• Several hundred – plant cells

Golgi ApparatusGolgi Apparatus

Receives protein-filled vesicles that bud from the ER.

Vesicles fuse with membrane of Golgi apparatus cis face.

Golgi ApparatusGolgi Apparatus

• Proteins modified as they pass through (form glycoproteins)

• Move to outer (trans) face after modification.

• Vesicles form & move to different locations in cell.

• At plasma membrane, vesicles discharge contents as secretions.

VesiclesVesiclesEnzyme StorehousesEnzyme Storehouses

Lysosomes – Intracellular digestion centers; bud from endomembrane system

Microbodies Peroxisomes – Enzymes catalyze the removal of

hydrogen atoms.

Glyoxysomes – Found in plants. Enzymes convert fats into carbohydrates

Lysosomes Intracellular digestion centersIntracellular digestion centers

Produced by Golgi

Membrane-enclosed vesicles

Contains digestive enzymes (function best in acidic environment)

Break down organelles

Animation: Lysosome FormationAnimation: Lysosome Formation

LysosomesLysosomes Intracellular digestion centersIntracellular digestion centers

Eliminates cells engulfed by phagocytosis.

White blood cells use lysosomes to digestengulfed bacteria.

AutodigestionAutodigestion - when lysosomes digestparts of cells.

ApoptosisApoptosis - programmed cell death, a normal part of development

Tadpole tail absorption. Degeneration of webbing between fingers

PeroxisomesPeroxisomes

• Abundant in cells that metabolize lipids

• Detoxify alcohol in liver and yeast cells

• Forms hydrogen peroxide that is brokendown to water and oxygen by catalase.

RH2 + O2 R + H2O2 H2O + O2

GlyoxysomesGlyoxysomes(Peroxisomes in plants)(Peroxisomes in plants)

In leaves carry out reactions the uses up O2 and releases CO2 that can be used in photosynthesis

In germinating seeds - convert oils into sugars used as nutrients by growing plants.

VacuolesVacuoles• Large membranous sac

• Larger than vesicles

• Store substances

• Vacuoles in protozoans include digestive

vacuoles and water-regulating contractile

vacuoles.

VacuolesVacuoles

In protozoans include digestive vacuoles and water-regulating contractile vacuoles.

VacuolesVacuoles

Plant cell vacuoles (usually one or two) more prominenet; water-filled and give support to cell.

Plant vacuoles store water, sugars, salt, pigments, and toxic substances to protect plant from herbivores.