4.4 The endomembrane system and proteins and 4.5 Cytoskeleton

Chapter 4 biology

What makes up the endomembrane system?

• Nuclear envelope

• Lysosomes

• vesicles

• endoplasmic reticulum

• golgi apparatus

• plasma membrane

What are lysosomes?

They’re present in animal cells and break down large biomolecules and worn out organelles

What is the endoplasmic reticulum (ER)

• Is continuous with the nuclear envelope

• Hollow part of the ER tubules is called the lumen or cisternal

• Interconnected sac and tubules

The rough endoplasmic reticulum…

• Modifies proteins

• Ribosomes attach to the cytoplasmic surface and manufacture proteins

• Proteins are modified in the cisternal part of the RER

The smooth endoplasmic reticulum…(SER)

• Has few to no ribosomes

• Synthesizes lipids, carbohydrates and steroid hormones.

• Stores CA⁺⁺

What is the purpose of the golgi apparatus?

Sorts, packages and tags lipids or proteins within the transport vesicle

The receiving side of the golgi apparatus is called…?

The cis face

the opposite side of the golgi apparatus is called…

the trans face

The cytoskeleton…

Is a network of protein fibers with several functions

What is the cytoskeletons functions

• Helps maintain the shape of the cell

• Holds some organelles in specific positions

• Allows movement of cytoplasm and vesicles within the cell

• Enables cells within multicellular organisms to move

What are the three fibers within the cytoskeleton?

• Microfilaments

• Intermediate filaments

• Microtubules

Microfilaments…

• Are involved with movement

• Determines and stabilizes the shape

• Enables cellular movement

• and is made from actin monomers

Intermediate filaments…

• Provides mechanical strength and helps stabilize cell shape and anchors the nucleus and other organelles in place

• Tough and flexible fibers assembled from protein subunits

Microtubules…

• Forms rigid internal skeleton for some cells

• Provide framework for motor proteins to move structures within cell

• Strong but not as flexible

• Made from 13 chains of tubulin dimers

What is ultrastructure?

9+2 array of microtubules…9 doublets on outside and 2 unfused in center

What is the endomembrane system?

Consists of internal membranes and organelles in eukaryotic cells that work together to modify, package and transport lipids and proteins

What do lysosomes help break down?

• Proteins

• Polysaccharides

• Lipids

• Nucleic acid

Where else can ribosomes be found?

Floating in the cytoplasm

What are trans proteins?

Proteins that go along the membrane

What are secreted proteins?

Made within the cell and are then secreted from the cell

What are two classes of proteins that ribosomes in the RER manufacture?

Trans and secreted proteins

What are microfilaments composed of?

Actin monomers

What are microtubules made of?

Tubulin dimers