The Endomembrane System (2A)

Endomembrane System Components

• ER

• Golgi

• Vesicles

• Cell Membrane

• Vacuoles

• Lysosomes

• Peroxisomes

Functions (as a whole)

Synthesizes, distributes, stores, and exports molecules

Endoplasmic Reticulum (ER) Structure

Flattened sacs (rough) and tubes (smooth) continuous with the nuclear membrane

Smooth ER Functions

1. Produces lipids (phospholipids, cholesterol, and steroid hormones)

2. Detoxification of alcohol and drugs (especially in liver cells)

3. Stores calcium ions (especially in muscles cells)

Rough ER Functions (has attached ribosomes)

1. Produces proteins for secretion

   a. helps proteins fold properly

   b. initial protein modifications including adding carbohydrate chains and removing some excess amino acids

2. Produces membrane proteins + phospholipids

3. Produces enzymes for lysosomes

Golgi Apparatus (Golgi Body) Structure

Look like flattened pancakes, layers are not physically connected to each other

Golgi Apparatus Function

Accept proteins from the ER and make final modifications to those proteins. Then ships the proteins to their final destination (usually cell membrane or lysosomes).

Lysosomes

1. Membrane enclosed sacs

2. Contain enzymes that were produced by the ER and processed by the Golgi

3. Maintains an acidic pH

Lysosomes Function

1. Digestive functions

   a. recycle organelles

   b. combine w/ food vacuoles to digest the materials inside

Vacuoles

Membrane enclosed sacs

Vacuoles Functions

1. Storage of resources or cell products

2. Maintain cell structure

   a. large permanent vacuole in plant cells (tonoplast)

   b. contractile vacuole - protects some protists from exploding when they take in excess water

Peroxisomes Structure

small membrane-bound sacs (like lysosomes and vesicles)

Peroxisomes Function

1. metabolize hydrogen peroxide (peroxisomes have catalase)

2. break down triglycerides

   • the products of this digestion can be substrates for cellular respiration when carbohydrates are not available