1. A Tour of the Cell Figures 4.8 – 4.16
CHAPTER 4
A Tour of the Cell
Figures 4.8 – 4.16

2. Some functions of membrane proteins
Cytoplasm
Fibers of
extracellular
matrix c
Enzymatic activity b
Cell signaling a
Attachment to
cytoskeleton and
extracellular
matrix e
Intercellular
joining f
Cell-cell
recognition d
Transport
Cytoplasm
Cytoskeleton
Figure 4.8

3. This behavior leads to the description of a membrane as a fluid mosaic
Membrane phospholipids and proteins can drift about in the plane of the membrane
This behavior leads to the description of a membrane as a fluid mosaic
Molecules can move freely within the membrane
A diversity of proteins exists within the membrane

4. Selective Permeability
Membranes of the cell are selectively permeable
They allow some substances to cross more easily than others
They block passage of some substances altogether

5. The traffic of some substances can only occur through transport proteins
Glucose, for example, requires a transport protein to move it into the cell

6. THE NUCLEUS AND RIBOSOMES: GENETIC CONTROL OF THE CELL
The nucleus is the manager of the cell
Genes in the nucleus store information necessary to produce proteins

7. Structure and Function of the Nucleus
The nucleus is bordered by a double membrane called the nuclear envelope
It contains chromatin
It contains a nucleolus

8. Ribosomes
Chromatic
Nucleolus
Pore
Nuclear
envelope
Figure 4.9

9. Ribosomes
Ribosomes build all the cell’s proteins

10. How DNA Controls the Cell
DNA controls the cell by transferring its coded information into RNA
DNA 1
Synthesis of
mRNA in the
nucleus
mRNA
The information in the RNA is used to make proteins
Nucleus
Cytoplasm 2
Movement of
mRNA into
cytoplasm via
nuclear pore
mRNA
Ribosome 3
Synthesis of
protein in the
cytoplasm
Protein
Figure 4.10

11. THE ENDOMEMBRANE SYSTEM: MANUFACTURING AND DISTRIBUTING CELLULAR PRODUCTS
Many of the membranous organelles in the cell belong to the endomembrane system

12. The Endoplasmic Reticulum
The endoplasmic reticulum (ER)
Nuclear
envelope
Produces an enormous variety of molecules
Is composed of smooth and rough ER
Ribosomes
Rough ER
Smooth ER
Figure 4.11

13. Rough ER
The “roughness” of the rough ER is due to ribosomes that stud the outside of the ER membrane

14. The functions of the rough ER include
Producing proteins
Producing new membrane

15. After the rough ER synthesizes a molecule it packages the molecule into transport vesicles4
Transport vesicle
buds off
Secretory
protein inside
transport
vesicle
Ribosome 3
Protein 1
Rough ER 2
Polypeptide
Figure 4.12

16. Smooth ER
The smooth ER lacks the surface ribosomes of ER and produces lipids, including steroids

17. The Golgi Apparatus The Golgi apparatus
Works in partnership with the ER
Refines, stores, and distributes the products of cells
Transport
vesicle
from ER
“Receiving” side of
Golgi apparatus
Golgi apparatus
New vesicle forming
Transport vesicle
from the Golgi
“Shipping” side of
Golgi apparatus
Plasma membrane
Figure 4.13

18. A lysosome is a membrane-enclosed sac
Lysosomes
A lysosome is a membrane-enclosed sac
It contains digestive enzymes
The enzymes break down macromolecules

19. Lysosomes have several types of digestive functions
They fuse with food vacuoles to digest the food
Lysosome
Digestive enzymes
Plasma
membrane
Digestion
Food
Food vacuole
(a) Lysosome digesting food
Figure 4.14a

20. They break down damaged organelles
Lysosome
Digestion
Damaged
organelle
(b) Lysosome breaking down damaged organelle
Figure 4.14b

21. Vacuoles are membranous sacs
Two types are the contractile vacuoles of protists and the central vacuoles of plants
Central
vacuole
Contractile
vacuoles
(a) Contractile vacuoles in a protist
(b) Central vacuole in a plant cell
Figure 4.15

22. A review of the endomembrane system
Rough ER
Transport
vesicle from ER
Golgi
apparatus
Secretory
vesicle from Golgi
Secretory
protein
Vacuole
Lysosome
Plasma membrane
Figure 4.16