1. The Cell: An Overview Ch. 5; 5.3-5.5

2. Eukaryotes: The Nucleus
Nucleus is membrane bound nuclear envelope (2x layer)
How do things move through the envelope?
Just like the plasma membrane, proteins (nucleoporins) channels allow entrance (nuclear pore complexes)
How do they know what goes in?
Short AA sequence (nuclear localization signal) acts like a zip code for the nucleus

3. Eukaryotes: The Nucleus
What do you find inside the nucleus?
nucleoplasm cytoplasm in nucleus
Chromatin DNA/Protein complex
Chromosomes condensed DNA
Nucleolus mixture of gene regions and RNA complexes

4. Eukaryotes: Ribosomes
Why do we have free floating and membrane bound ribosomes?
Different products for different environments
1) Free ribosomes produce proteins to be used in the cytosol
2) Attached ribosomes produce proteins to be embedded in membranes or secreted
Both have complex organelle path after completion

5. Eukaryotes: Endoplasmic Reticulum
Smooth ER makes lipids and digestive enzymes for drugs and toxins
Rough ER makes secreted proteins and digestive enzymes
What cells in the body would have the largest smooth and rough ER?
Liver cells (smooth)
Digestive tract (rough)

6. Eukaryotes: Golgi Complex
Rows of flatten sacs (cisternae) receive vesicles from areas of the cell (at cis face), modify the contents, and send them to their next location (at trans face)
Most proteins are embedded or secreted (exocytosis)
Some molecules drawn into the cell (endocytosis) and destroyed by fusion with lysosomes

7. Eukaryotes: Lysosomes
Digestive sacs in animals cells (over 300) that act like recycling centers
Acidic (pH ~5)
Why is it important they only work in a high pH?
Lowers risk of activity outside of lysosome; wont work in basic cytosol
Enzymes made in rough ER and then vesicle formed from Golgi complex
Roles:
Autophagy digest useless organelles
Phagocytosis digest bacteria pulled into the cell

8. Eukaryotes: Mitochondria
Site of cellular respiration
Double layered membrane with reactions between the cristae and the matrix
What about mitochondria suggest that they used to be independent organisms?
The have their own DNA and ribosomes

9. Eukaryotes: Microbodies
Large vesicles that do various tasks:
Phospholipid synthesis
Breakdown fats and proteins to make ATP
Breakdown toxins
Peroxisomes vesicles of catalase
What do they do?
Breakdown hydrogen peroxide

10. Eukaryotes: Cytoskeleton
Reinforce cell shape and allow movement around the cell
Like your organs, a cells organelles must be held in place
3 groups:
Microtubules
Intermediate Filaments
Microfilaments

11. Eukaryotes: Microtubules
Long, wide tubes (25nm) made of α and β tubulin
Charge ends, with more activity on the + end
Why do they need charged ends?
Can use ionic forces to hold them in place in the cell
Network radiates from the cell center (centrosome) and have two perpendicular barrels (centrioles)
Hold organelles in place and are tracks for vesicle movement
Motor proteins (kinesins and dyneins)

12. Eukaryotes: Microtubules
Main part of flagella and cilia
9 + 2 complex  9 double tube units around 2 single tube units
Wave and oar-like movements push cell through mediums
Flagella are found in all 3 domains, but their genes are different. What does this tell us about flagella evolution?
It was independent even though they have the same structure and function

13. Eukaryotes: Intermediate Filaments
Medium sized (8-12nm) fibers that connect microtubules/ microfilaments together; adds stability
Not found in single-cell organisms
Tissue specific have different proteins depending on the what part of the organism they are in

14. Eukaryotes: Microfilaments
Thin fibers (5-7nm) of actin units
Charged ends with more growth on the + end
Main part of muscle tissue
Myosin (motor protein) moves back and forth along microfibers causing contractions
Cytoplasmic streaming movement of the cytoplasm
Cause amoeboid movement
Divided cytoplasm during division

15. Eukaryotes: Chloroplasts
Plastid
Amyloplasts starch forming cells (potato)
Chromoplasts red and yellow pigments give color to fruits and autumn leaves
Double membrane around the stroma (inner area) which is filled with a 3rd membrane that makes the thylakoids/grana
Thylakoids have chlorophyll pigments that absorb light energy
How are chloroplast and mitochondria similar?
Both have their own DNA and ribosomes

16. Eukaryotes: Central Vacuole
Functions are giant lysosome for the cell; also a storage unit
Stores pigments that give flowers their color
Tonoplast channels that allow transportation of materials
Turgor pressure pushes against weight of cell well
What happens with plants are low on water?
The wilt; sag because turgor pressure drops

17. Eukaryotes: Cell Wall Extracellular Structure
Primary soft/flexible layer expands as cell grows
Secondary harder cellulose fibers used to strengthen wall
lignin complex alcohol structure stronger than concrete (by weight)
Polysaccharide layer (middle lamella) acts like glue to hold plant cells together
Pectin used in syrup and jams
How do cells communicate through these think walls?
Channels (plasmodesmata) allow instant communication between plant cells

18. There is too much vocabulary!
Homework
Read Ch. 6
Vocabulary for Ch. 6
“Test Your Knowledge” Multiple choice questions on p. 114 and “Interpret the Data” on p. 115
There is too much vocabulary!