1. Organelles & Cell Structure
CELLULAR BIOLOGY
Organelles & Cell Structure

2. Prokaryote vs. Eukaryote Cells
Prokaryotes
The True Bacteria
No Nucleus or Nuclear Membrane
Small, often circular simple strand of DNA
Cell Wall, not membrane
Much smaller cells
Eukaryotes
Not Bacteria, more complex (plants, animals)
True Nucleus with nuclear membrane and complex DNA
Cell Wall (plants)
C. Membrane (animals)
Larger cells than bacteria
Often specialized cell function

3. Eukaryotic Cells: Plant vs. Animal Cells
Tougher cell membrane
More complex nucleus with
longer strands of DNA in
several chromosomes
Some vacuoles, but fewer
and smaller
No Chloroplasts
Mitochondria for cell
metabolism & energy
production
Complex Endoskeleton
Plant Cells
Permeable cell wall
Simple nucleus with shorter & fewer strands of DNA in chromosomes
Large vacuoles for storage
No Mitochondria
Chloroplasts for Photosynthesis
Simple Endoskeleton

4. Plant vs. Animal Cells Plant Cells Permeable cell wall
Simple nucleus with shorter & fewer strands of DNA in chromosomes
Large vacuoles for storage
No Mitochondria
Chloroplasts for Photosynthesis
Simple Endoskeleton

5. Plant vs. Animal Cells Animal Cells Tougher cell membrane
More complex nucleus with longer strands of DNA in several chromosomes
Some vacuoles, but fewer and smaller
No Chloroplasts
Mitochondria for cell metabolism & energy production
Complex Endoskeleton

6. Organelles of importance
Ribosomes—Function?
Production of proteins
Golgi Apparatus—Function?
Packaging and shipping center of cell for repackaging and shipping of proteins and lipids
Vacuoles—Function?
Storage, particularly in plant cells, water, starch, etc.

7. Endoplasmic Reticulum Rough ER vs. Smooth ER
No ribosomes on surface
Produces lipids
Usually located near cell membrane
Rough
Ribosomes on surface
Production of special proteins for incorporation into nucleus (RNA & DNA)
Located near nucleus

8. Lysosomes & Peroxisomes
Lysosomes—function?
Digestion and breakdown of molecules for use in other areas of cell
Peroxisomes—function?
Total breakdown of invaders—creation of waste material for excretion

9. MITOCHONDRIA Function? “Powerhouse of the Cell”
Turn nutrients into energy molecules the cell can use or package for other parts of the body
In Animals—converts carbohydrates and oxygen into CO2 and energy molecules
Will be detailed in future lecture

10. Chromosomes, Centrioles, & Spindle Fibers
Chromosomes—function?
Packages containing strands of DNA material which is reproduced and divided during cellular reproduction
Centrioles—function?
“Cable-like” organelles used for pulling the
cell membrane inward during division
Spindle Fibers—function?
Pull divided chromosomes to each side of cell during cellular reproduction and division

11. Cell Membrane & Cell Transport
Animal cell membranes are made up of two layers of phospholipids with a cholesterol molecules between the layers
Membrane is boundary between cell and environment
Membrane has selective permeability, which means only allows certain molecules to cross in and out of cell

12. Structure of Cell Membrane
Polar head on outside of layers is a phosphate group molecule designed to attract water
Glycerol backbone holds structure in place
Fatty acids form long tales which provide repellent from water

13. Cell membrane continued
Entire structure is phospholipid
Double layer is bi-layer with heads on outer border and fatty acids on inner
Membrane is fluid mosaic—that is has ability to flex and bend
Transport proteins aid in transport of certain molecules across membrane boundaries

14. Cellular Transport
All cells strive to maintain equilibrium with their outside environment
To maintain balance, molecules will move in and out of the cell until equilibrium is met.
Molecules may move through the membrane by passive means, through a transport protein, or through manipulation of cell membrane
When the membrane does not allow anything to cross—termed “selective”

15. Passive Transport: Diffusion
Diffusion is movement of materials from an area of high concentration to an area of lower concentration
The difference between concentrations is call the Concentration Gradient
Facilitated Diffusion may use a transport protein or energy because the gradient is too strong to pass through—EX: pouring material through a filter of some time may take some energy to push it

16. Passive Transport: Osmosis
Membrane does not limit diffusion of water. Water molecules always try for balance in and out of the cell—move towards equilibrium
Osmosis is the diffusion of water across the cell membrane
Again, no energy required, simple movement to maintain equilibrium

17. Passive Transport: Three modes of Osmosis
Isotonic Solutions (equal)
Dissolved substances inside and outside the cell are of the same percentage
There will be no movement of substances or water

18. Passive Transport: Three modes of Osmosis
2. Hypotonic Solutions (lower outside)
Concentration of dissolved substances is lower outside the cell in the solution
Substances will move from inside to outside
Water will move from the outside to the inside of the cell to maintain equilibrium
When water enters the cell via osmosis, the cell will swell from the pressure and may eventually burst from the pressure--This pressure is called Turgor Pressure
EX: RBCs will burst when mixed with distilled water
In Plants, cells will move water to vacuoles and actually become more rigid

19. Passive Transport: Three modes of Osmosis
3. Hypertonic Solutions (High outside)
Concentration of dissolved substances outside the cell is higher than inside
Substances will try to enter the cell
Water will move through the cell membrane causing the cell to shrink and shrivel—loss of this Turgor pressure is called plasmolysis
EX: putting RBC into 4% Ocean saltwater
Plant cells will shrivel and the plant will wilt

20. Active Transport: Requires Energy
Movement of particles across membranes from an area of low concentration to an area of high concentration
Movement against the concentration gradient
This movement by facilitated diffusion that requires energy expenditure by the cell

21. Active Transport: Exocytosis vs Endocytosis
Movement of particles from inside to outside the cell
Accomplished by
Cell Membrane manipulation
Endocytosis
Process by which a cell surrounds and takes in particles from environment
Does not pass thru membrane, engulfed and enclosed by membrane

22. Pinocytosis and Phagocytosis
Literally
“Cell Drinking”
Membrane manipulates to engulf large volumes of fluid
Cell can drink small particles and fluid
Phagocytosis
Literally
“Cell Eating:
Membrane manipulates to engulf large molecule of nutrient or “food”
Cell can eat large molecules