Endomembrane System

By Mariah Ghant, Saori Ishizuka, and Monica Lin

The set of membranes found in eukaryotic

cells that carry out a variety of tasks in the cell

Tasks include: Synthesis of proteins Protein transport

into membranes and organelles out of the cell

Metabolism and movement of lipids Detoxification of poisons

Definition

Nuclear Envelope Endoplasmic

Reticulum (Smooth and Rough)

Golgi Apparatus Lysosomes Vacuoles Plasma Membrane

Major Parts of the Endomembrane

Nuclear Envelope

Structure Double Membrane Perforated by pore

structures Nuclear side is lined

with nuclear lamina Ribosomes on

cytoplasmic side

Function Encloses the nucleus Separates its

contents from the cytoplasm

Endoplasmic Reticulum Rough ER

Function Makes secretory

proteins (glycoproteins)

Keeps proteins seperated

Makes transport vesicles

“Membrane Factory” for the cells

Structure Many proteins and

phospholipids added to its own membrane

Has ribosomes continuous with

smooth ER

Endoplasmic Reticulum Smooth ER

Function Structure Synthesis of Lipids Metabolism of

Carbohydrates Detoxification of

Drugs and Poisons Stores calcium ions

Lacks ribosomes Membranes system

of interconnected tubules

Golgi ApparatusFunctions

Multiple interactions with the product of the ER (proteins): Modifies Stores Sends to multiple

destinations 2 poles of Golgi stack:

Cis face- receives vesicles containing ER products

trans face- dispatches vesicles

Structure

Consists of flattened membranous sacs (citernae)

LysosomesFunctions

Used in animal cells to digest macromolecules

Autophagy- process of recycling the cell’s own organic material

Phagocytosis- process of intracellular digestion in amoebas and small organisms

Structure

Membranous sac of hydrolytic enzymes

VacuolesFunctions

Their functions vary in different cells: Food Vacuoles- fuses with

the lysosome during the process of phagocytosis

Contractile Vacuoles- pump excess water out of the cell

Central Vacuole- located in mature plant cells; holds important organic compound reserves; main repository of inorganic ions

Major role in the growth of plants

Structure

Membrane-bounded vesicles

Container shape Contains pigments

that color cells

Plasma MembraneFunctions

Encloses the entire cell

Protein secretion occurs here after they’ve been carried by transport vesicles

Structure

Thin layer of cytosol between central vacuole and plasma membrane

The endomembrane interacts with the nucleus

via nuclear envelope The nuclear envelope is connected to the

rough ER, which encloses the nucleus

Interactions

1. Nuclear envelope is connected to rough ER2. Membranes and proteins produced by the ER flow in the

form of transport vesicles to the Golgi3. Golgi pinches off transport vesicles and other vesicles that

give rise to: lysosomes other types of specialized vesicles vacuoles

4. Lysosome is then available for fusion with another vesicle for digestion

5. Transport vesicle carries proteins to plasma membrane for secretion

6. Plasma membrane expands by fusion of vesicles; proteins are secreted from the cell

Review

Video

http://www.youtube.com/watch?v=PASnAaulK-Y