CHAPTER 6
A TOUR OF THE CELL
Cytology: science/study of cells
Light microscopy resolving power~ measure of
clarity
 Electron microscopy
TEM ~ electron beam to study cell
ultrastructure
SEM ~ electron beam to study cell surfaces
 Cell fractionation ~ cell separation; organelle study
 Ultracentrifuge ~ cell fractionation; 130,000rpm
A cell is a living unit greater
than the sum of its parts
• While the cell has many structures that have
specific functions, they must work together.
Types of cells
Prokaryote
bacteria cells
- no organelles
- organelles
Eukaryote
animal cells
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Eukaryote
plant cells
Cell Types: Prokaryotic
Nucleoid: DNA
concentration
No organelles with
membranes
Ribosomes:protein synthesis
Plasma membrane: (all
cells); semi-permeable
Cytoplasm/cytosol(all cells)
Cell types: Eukaryotic
 Nucleus:membrane enclosed organelle containing
chromosomes
 Membrane bound organelles of specialized form and
function
 Generally larger than prokaryotic cells
Cell Size
As cell size increases, the surface area to volume
ratio decreases
Rates of chemical exchange may then be
inadequate for cell size
Cell size, therefore, remains small
Why organelles?
 Specialized structures

specialized functions
mitochondria
 cilia or flagella for locomotion
 Containers


partition cell into compartments
create different local environments
chloroplast
 separate pH, or concentration of materials

distinct & incompatible functions
 lysosome & its digestive enzymes
 Membranes as sites for chemical reactions


unique combinations of lipids & proteins
embedded enzymes & reaction centers
Golgi
 chloroplasts & mitochondria
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ER
Cells gotta work to live!
 What jobs do cells have to do?

make proteins
 proteins control every
cell function

transfer energy
 for daily life
 for growth

make more cells
 growth
 repair
 renewal
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Proteins do all the work!
proteins
cells
DNA
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organism
Repeat after me…
Proteins do all the work!
Cells functions
 Building proteins
read DNA instructions
 build proteins
 process proteins

 folding
 modifying
 removing amino acids
 adding other molecules


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e.g, making glycoproteins
for cell membrane
address & transport proteins
Building Proteins
 Organelles involved
nucleus
 ribosomes
 endoplasmic reticulum
(ER)
 Golgi apparatus
 vesicles

The Protein Assembly Line
nucleus
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ribosome
ER
Golgi
apparatus
vesicles
Nucleus
DNA
 Function
chromosome
protects DNA
Structure



histone protein
nuclear envelope
 double membrane
 membrane fused in spots to create pores
 allows large macromolecules to pass through
nuclear
pores
What kind of
molecules need to
pass through?
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nuclear
pore
nucleolus
nuclear envelope
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Nucleolus
 Function

ribosome production
 build ribosome subunits from rRNA & proteins
 exit through nuclear pores to cytoplasm &
combine to form functional ribosomes
large subunit
small
subunit
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rRNA &
proteins
ribosome
nucleolus
large
subunit
Ribosomes
 Function

small
subunit
protein production
 Structure


rRNA & protein
2 subunits combine
0.08mm
Ribosomes
Rough
ER
Smooth
ER
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Types of Ribosomes
 Free ribosomes


suspended in cytosol
synthesize proteins that
function in cytosol
 Bound ribosomes


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attached to endoplasmic
reticulum
synthesize proteins
for export or
for membranes
membrane proteins
Endoplasmic Reticulum
 Function



processes proteins
manufactures membranes
synthesis & hydrolysis of many compounds
 Structure

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membrane connected to nuclear envelope &
extends throughout cell
Types of ER
rough
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smooth
Smooth ER function
 Membrane production
 Many metabolic processes

synthesis
 synthesize lipids
 oils, phospholipids, steroids & sex hormones

hydrolysis
 hydrolyze glycogen into glucose
 in liver
 detoxify drugs & poisons
 in liver
 ex. alcohol & barbiturates
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Synthesize components of the
Endomembrane System
 Build new
membrane

synthesize
phospholipids
 builds membranes

ER membrane
expands
 bud off & transfer
to other parts of
cell that need
membranes
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Rough ER function
 Produce proteins for export out of cell
protein secreting cells
 packaged into transport vesicles for export

Which cells
have lot of
rough ER?
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Golgi Apparatus
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Vesicle transport
protein
vesicle
budding
from rough
ER
ribosome
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migrating
transport
vesicle
fusion
of vesicle
with Golgi
apparatus
Any Questions!!
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2007-2008