1. Cell Parts and Functions
Parts are collectively called organelles
“stuff” inside cell is cytoplasm (protoplasm): jellylike substance organelles float in
Organelles are MEMBRANE-BOUND, meaning each of them have their own fluid membranes

2. Cell Parts and Functions
Cell Membrane
Fluid Mosaic Model (Singer-Nicolson)
Held together by Van der Waals forces
Surrounds cell, controls what goes in and out. Today, “fluid mosaic” model of Singer is generally accepted. It says membrane is lipid bilayer with proteins embedded in it.
Lipid bilayers are commonly composed of phospholipids that have 2 non-polar hydrophobic “tails” facing inward, plus a hydrophilic head facing outward.
The heads are soluble in water, the tails in fats.
Other lipid materials may dissolve in the non-polar center of the membrane and diffuse laterally. The 2 layers themselves are fluid, and phospholipid molecules may move laterally.
Membrane is like a coat of wet paint – it runs and shifts
Polar molecules or ions K+, Na+, do NOT pass freely through this membrane
Held together by non-covalent bonds (Van der Waals forces)

3. Cell Parts and Functions
Cell Membrane
Proteins serve specific functions
Carbohydrate end of glycoproteins serve as receptors for certain hormones
Channels or gates
Membranes are asymmetric; inner and out surfaces are NOT the same. Glycoproteins are oriented so the carbohydrate part always faces out.

4. Note regarding fluidity (viscosity) of cell membranes
2 different cells may fuse to form a heterokaryon (=different nucleus)
Complete mixing of proteins shows the fluid nature of the membrane

5. Cell Parts and Functions
Nucleus
Bound by nuclear membrane/envelope; has pores for RNA and nuclear proteins to pass
Contains genetic material; chromatin (DNA & proteins)
Nucleolus: make ribosomes

8. Cell Parts and Functions
Ribosomes
Protein synthesis  specific step is known as translation
Made of rRNA (ribosomal RNA); has 2 subunits
Ribosomes are labeled in the TEM image as red dots

9. Cell Parts and Functions
Mitochondria
Make ATP (energy) in process of respiration
Folds provide more surface area for work to be done
Contain own DNA, RNA, and ribosomes so they can self-replicate by fission
Endosymbiotic theory

10. Cell Parts and Functions
Cell Wall
Found in plants AND bacteria
In plant cell walls: rigid cellulose surrounded by lignin, which strengthens and waterproofs the wall

11. Cell Parts and Functions
Cell Wall
Found in plants AND bacteria
In plant cell walls: rigid cellulose surrounded by lignin, which strengthens and waterproofs the wall 11

12. Cell Parts and Functions
Cell Wall
Found in plants AND bacteria
In bacteria: primary structure of cell wall is made of peptidoglycan; structurally similar to chitin found in the exoskeleton of some arthropods

14. Cell Parts and Functions
Plastids
Contain DNA, RNA, ribosomes; self-replication by fission
Chloroplasts: photosynthesis; contain chlorophyll
Chromoplasts: give color to fruit and flowers
Carotene
Carotenoids
Leucoplasts: colorless; store starch
amyloplasts

16. Cell Parts and Functions
Vacuoles
Fluid-filled space surrounded by tonoplast (plants)
Functions as storage
Size changes depending on osmosis; provides turgor for plants

18. Cell Parts and Functions
Endoplasmic Reticulum (ER)
Tunnels through cytoplasm- transports proteins throughout the cell
Rough ER contains many ribosomes
Smooth ER makes lipids
Vesicles released from here are called peroxisomes

21. Cell Parts and Functions
Peroxisomes (eukaryotic cells only)
contain hydrolytic (oxidative) enzymes like catalase
Help digest fatty acids (and ethanol by using hydrogen peroxide)
Bud off from ER
Abundant in liver and kidney cells

22. Catalase reaction
H2O2 + H2R → 2H2O + R