CELL STRUCTURES INVOLVED IN MANUFACTURING

4.6 Nucleus

• The nucleus is the cell’s genetic control center• The nucleus controls the cell’s activities and is responsible

for inheritance– Inside is a complex of proteins and DNA called chromatin,

which makes up the cell’s chromosomes– DNA is copied within the nucleus prior to cell division

4.6 Nucleus

• The nucleolus is in charge of transcribing DNA into RNA for protein synthesis.

4.6 Nucleus

• The nuclear envelope/ nuclear membrane is a double membrane with pores that allow material to flow in and out of the nucleus– It is attached to the ER

Two membranes ofnuclear envelope Nucleus

NucleolusChromatin

Pore

Endoplasmicreticulum

Ribosomes

TEM (left) and diagram (right) of the nucleus.

4.7 Ribosomes

• Ribosomes make proteins for use in the cell and export– Ribosomes are synthesized in the nucleolus, which is

found in the nucleus– Cells that must synthesize large amounts of protein

have a large number of ribosomes

4.7 Ribosomes

• Some ribosomes are free ribosomes; others are bound– Free ribosomes are suspended in the cytoplasm– Bound ribosomes are attached to the endoplasmic

reticulum (ER) associated with the nuclear envelope

Cytoplasm

Endoplasmic reticulum (ER)

Free ribosomes

Bound ribosomes

RibosomesER

Smallsubunit

Diagram of a ribosome

TEM showing ERand ribosomes

Largesubunit

4.8 Endomembrane system

• The membranes within a eukaryotic cell are physically connected and compose the endomembrane system– Includes the nuclear envelope, endoplasmic reticulum

(ER), Golgi apparatus, lysosomes, vacuoles, and the plasma membrane.

– The endomembrane system is involved in the synthesis, storage, and export of materials throughout the cell.

4.9 Endoplasmic Reticulum (ER)

• There are two kinds of ER—smooth and rough. • They are connected.• Smooth ER (lacks attached ribosomes)– Synthesis of lipids, oils, phospholipids, and steroids

• Rough ER (has attached ribosomes)– Synthesis of proteins, transported in vesicles

Smooth ER

Nuclearenvelope

Ribosomes

Rough ER

CELL STRUCTURES INVOLVED IN BREAKDOWN

4.10 Golgi apparatus (aka Golgi Body) and Vesicles

• The Golgi apparatus finishes, sorts, and ships cell products from the ER– Products travel in transport vesicles from the ER to

the Golgi apparatus– One side of the Golgi apparatus functions as a

receiving dock for the product and the other as a shipping dock

Golgi apparatusGolgi apparatus

“Receiving” side ofGolgi apparatus

Transportvesiclefrom ER

New vesicleforming

“Shipping” sideof Golgi apparatus

Transportvesicle fromthe Golgi

Protein production Protein delivery

1. Synthesized in Ribosome

2. Folded in ribosome on rough ER

3. Transport vesicle containing protein breaks off of rough ER

4. Transport vesicle brings protein to Golgi.

5. Golgi finishes the process, sorts the proteins, and ships the proteins in another transport vesicle.

6. The vesicle travels to the cell membrane, in which the protein is released and can go on to do its functions.

Transport vesiclebuds off

Secretoryproteininside trans-port vesicle

GlycoproteinPolypeptide

Ribosome

Sugarchain

Rough ER

1

2

3

4

Synthesis and packaging of a secretory protein by the rough ER.

Fig. 6-16-1

Smooth ER

Nucleus

Rough ER

Plasma membrane

Fig. 6-16-2

Smooth ER

Nucleus

Rough ER

Plasma membrane

cis Golgi

trans Golgi

Fig. 6-16-3

Smooth ER

Nucleus

Rough ER

Plasma membrane

cis Golgi

trans Golgi

4.11 Lysosomes

• A lysosome is a sac containing digestive enzymes– Digests macromolecules: proteins, carbs, nucleic

acids, lipids– Recycles cell parts by autophagy (means “self-

eating”)

Digestiveenzymes

LysosomePlasmamembrane

Digestiveenzymes

LysosomePlasmamembrane

Food vacuole

Digestiveenzymes

LysosomePlasmamembrane

Food vacuole

Digestiveenzymes

LysosomePlasmamembrane

Food vacuole

Digestion

Lysosome

Vesicle containingdamaged mitochondrion

Lysosome

Vesicle containingdamaged mitochondrion

Lysosome

Vesicle containingdamaged mitochondrion

Digestion

4.12 Vacuoles

• Vacuoles function in the general maintenance of the cell– Central vacuole in plants has hydrolytic functions

(hydrolysis)– Pigment vacuoles in plants provide color to flowers– Contractile vacuoles in protists help to expel water from

the cell

Nucleus

Chloroplast

Centralvacuole

Central vacuole in a plant cell.

Nucleus

Contractilevacuoles

Contractile vacuoles in Paramecium, a single-celled organism

4.13 A review of the structures involved in manufacturing and breakdown

• The following figure summarizes the relationships among the major organelles of the endomembrane system

Nucleus

VacuoleLysosome Plasma membrane

Smooth ER

Nuclearmembrane

Golgiapparatus

Rough ER

Transportvesicle

Transportvesicle