A Tour of the Cell

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5

Fig. 6-10

Nucleolus

Nucleus

Rough ER

Nuclear lamina (TEM)

Close-up of nuclear envelope

1 µm

1 µm

0.25 µm

Ribosome

Pore complex

Nuclear pore

Outer membrane

Inner membrane

Nuclear envelope:

Chromatin

Surface of

nuclear envelope

Pore complexes (TEM)

Slide 34

Pores regulate the entry and exit of molecules from the nucleus

The shape of the nucleus is maintained by the nuclear lamina, which is composed of protein

Slide 35

In the nucleus, DNA and proteins form genetic material called chromatin

Chromatin condenses to form discrete chromosomes

The nucleolus is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesis

Slide 36

Ribosomes: Protein Factories

Ribosomes are particles made of ribosomal RNA and protein

Ribosomes carry out protein synthesis in two locations:

In the cytosol (free ribosomes)

On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)

Slide 37

Fig. 6-11

Cytosol

Endoplasmic reticulum (ER)

Free ribosomes

Bound ribosomes

Large subunit

Small subunit

Diagram of a ribosome

TEM showing ER and ribosomes

0.5 µm

Slide 38

Concept 6.4: The endomembrane system regulates protein traffic and performs metabolic functions in the cell

Components of the endomembrane system:

Nuclear envelope

Endoplasmic reticulum

Golgi apparatus

Lysosomes

Vacuoles

Plasma membrane

These components are either continuous or connected via transfer by vesicles

Slide 39

The Endoplasmic Reticulum: Biosynthetic Factory

The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells

The ER membrane is continuous with the nuclear envelope

There are two distinct regions of ER:

Smooth ER, which lacks ribosomes

Rough ER, with ribosomes studding its surface

Slide 40

Fig. 6-12

Smooth ER

Rough ER

Nuclear envelope

Transitional ER

Rough ER

Smooth ER

Transport vesicle

Ribosomes

Cisternae

ER lumen

200 nm

Slide 41

Functions of Smooth ER

The smooth ER

Synthesizes lipids

Metabolizes carbohydrates