1. Tour of the Cell
11/19/2018

2. I. Why do cells have organelles (little organs)?
mitochondria
I. Why do cells have organelles (little organs)?
Specialized structures
specialized functions
cilia or flagella for locomotion
Containers
partition cell into compartments
create different local environments
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
chloroplasts & mitochondria
chloroplast
Golgi
Why organelles?
There are several reasons why cells evolved organelles. First, organelles can perform specialized functions. Second, membrane bound organelles can act as containers, separating parts of the cell from other parts of the cell. Third, the membranes of organelles can act as sites for chemical reactions.
Organelles as specialized structures
An example of the first type of organelle is cilia, these short filaments act as "paddles" to help some cells move.
Organelles as Containers
Nothing ever invented by man is as complex as a living cell. At any one time hundreds of incompatible chemical reactions may be occurring in a cell. If the cell contained a uniform mixture of all the chemicals it would not be able to survive. Organelles surrounded by membranes act as individual compartments for these chemical reactions. An example of the second type of organelle is the lysosome. This structure contains digestive enzymes, these enzymes if allowed to float free in the cell would kill it.
Organelle membranes as sites for chemical reactions
An example of the third type of organelle is the chloroplast. The molecules that conduct the light reactions of photosynthesis are found embedded in the membranes of the chloroplast. ER

3. II. Isolation of organelles A. Occurs by process of cell fractionation
II. Isolation of organelles A. Occurs by process of cell fractionation. B. Based on various densities of organelles. C. Begins with breaking open cell membranes without damaging organelles; Called homogenization.

5. Homogenate is spun in a centrifuge to separate the pellet of organelles from the liquid (supernatant).
Pellet is removed, and the supernatant is spun again at
higher speed to cause heaviest of
remaining organelles to settle out.

7. Heaviest to lightest cell fractions are nuclei, mitochondria/chloroplasts,
parts of membranes, then ribosomes.
G. Specific metabolic processes are
identified with certain cell fractions, and then tied to specific organelles.

8. Types of cells Eukaryote animal cells Eukaryote plant cells
Prokaryote bacteria cells
Eukaryote animal cells
Eukaryote plant cells

9. II. General Types of cells
Basic cell structures
1. Plasma membrane
2. Cytosol (jelly-like substance)
3. Ribosomes
4. DNA
B. Prokaryotic cells have DNA in nucleiod region; No membrane around
DNA.

11. C. Eukaryotic cells have DNA in
membrane-bound nucleus.
D. Eukaryotes also have membrane-bound
organelles floating in cytoplasm (region
between nucleus and cell membrane).
E. Eukaryotes are bigger than prokaryotes.

12. F. Eukaryotes have many internal membranes that divide internal space into compartments.
G. Compartmentalization allows for multiple metabolic processes to occur at the same time.