1. Lysosomes Structure: membrane sac of digestive enzymes
Contains hydrolytic enzymes (like an acidic environment; good ex. of cell compartmentalization)

2. Lysosomes Function: digest food digest broken cell organelles
recycle cell’s materials
programmed cell death (apoptosis)

3. digesting broken organelles
Lysosomes
lyso– = breaking things apart
–some = body
polymers digested into monomers pass to cytosol to become nutrients of cell
small food particle
lysosomes
digesting broken organelles
vacuole
digesting food

4. Lysosomes
1960 | 1974
white blood cells attack & destroy invaders = digest them in lysosomes
1974 Nobel prize: Christian de Duve
Lysosomes discovery in 1960s

5. Importance of compartmentalization
Lysosomal enzymes
Importance of compartmentalization
Lysosomal enzymes work best at pH 5
organelle creates custom pH
how?
proteins in lysosomal membrane pump H+ ions from the cytosol into lysosome
why?
enzymes are very sensitive to pH
enzymes are proteins — pH affects structure
why evolve digestive enzymes which function at pH different from cytosol?
digestive enzymes won’t function well if some leak into cytosol = don’t want to digest yourself!
lysosomes create a space where cell can digest macromolecules safely
rupturing a few lysosomes has little impact on a cell (pH of cytosol affects functionality of the lysosomal enzymes), but massive leakage from lysosomes can destroy cell
why evolve digestive enzymes which function at pH so different from cytosol?
digestive enzymes won’t function well if leak into cytosol = most times don’t want to digest yourself!
low pH = acid environment cause oxidation (removing electrons) & promotes hydrolysis

6. Diseases of lysosomes are often fatal
When things go bad…
Diseases of lysosomes are often fatal
digestive enzyme not working in lysosome
picks up biomolecules, but can’t digest one
lysosomes fill up with undigested material
grow larger & larger until disrupts cell & organ function
lysosomal storage diseases
more than 40 known diseases
example: Tay-Sachs disease build up undigested fat in brain cells

7. But sometimes cells need to die…
Lysosomes can be used to kill cells when they are supposed to be destroyed
some cells have to die for proper development in an organism
apoptosis
“auto-destruct” process
lysosomes break open & kill cell
ex: tadpole tail gets re-absorbed when it turns into a frog
ex: loss of webbing between your fingers during fetal development
Feedback mechanism
There are sensors in the cell that monitor growth. They trigger self-destruct when they sense processes.
Brown spots on leaves too.
Virus infected plant cell auto-destructs and even cells around it to wall off virus.

8. A Job for Lysosomes 6 weeks 15 weeks
Apoptosis: programmed destruction of cells in multi-cellular organisms programmed development control of cell growth
A Job for Lysosomes
6 weeks
15 weeks

9. Vacuoles Structure: Membrane-bound vesicles/sacs
Function: storage of materials (food, water, minerals, pigments, poisons)
Types:. food vacuoles, contractile vacuoles (maintain water balance in protists)
Plants: large central vacuole -- stores water, ions

10. plant cells animal cells Food & water storage food vacuole
central vacuole
animal cells
contractile vacuole

11. Vacuoles & vesicles vesicle small food particle
vacuole filled w/ digestive enzymes
vesicle
vesicle filled w/ digested nutrients

12. DNA  mRNA
Transcription
(blueprint)  (messenger)
2. mRNA exits through nuclear pores goes to ribosomes (for translation) on rough ER

13. 3. Unfinished protein packaged into vesicles  sent to Golgi
DNA  mRNA
Transcription
(blueprint)  (messenger)
2. mRNA exits through nuclear pores goes to ribosomes (for translation) on rough ER
3. Unfinished protein packaged into vesicles  sent to Golgi
4. Golgi modifies, labels, and exports proteins in vesicles

14. 3. Unfinished protein packaged into vesicles  sent to Golgi
DNA  mRNA
Transcription
(blueprint)  (messenger)
2. mRNA exits through nuclear pores goes to ribosomes (for translation) on rough ER
3. Unfinished protein packaged into vesicles  sent to Golgi
4. Golgi modifies, labels, and exports proteins in vesicle
5. Vesicles travel through cytoplasm and fuse with the cell membrane. Proteins are excreted/secreted.

15. Parts of plant & animal cell p 108-109

16. Plant Cell

17. Mitochondria In BOTH plants and animals Structure: 2 membranes
smooth outer membrane
highly folded inner membrane called Cristae
internal fluid-filled space called the mitochondrial matrix
DNA, ribosomes & enzymes
Why 2 membranes?
increase surface area for membrane-bound enzymes that synthesize ATP
In BOTH plants and animals

18. ATP Function Mitochondria cellular respiration
generate ATP
from breakdown of sugars, fats & other fuels
in the presence of oxygen
break down larger molecules into smaller to generate energy = catabolism
generate energy in presence of O2 = aerobic respiration

19. Chloroplasts are plant organelles
class of plant structures = plastids
amyloplasts
store starch in roots & tubers
chromoplasts
store pigments for fruits & flowers
chloroplasts
store chlorophyll & function in photosynthesis
in leaves, other green structures of plants & in eukaryotic algae

20. stroma = internal fluid-filled space containing:
Chloroplasts
Structure:
2 membranes
stroma = internal fluid-filled space containing:
DNA, ribosomes & enzymes
thylakoids = membranous sacs where ATP is made
grana = stacks of thylakoids
Why internal sac membranes?
increase surface area for membrane-bound enzymes that synthesize ATP

21. Function Semi-autonomous Chloroplasts photosynthesis
generate ATP & synthesize sugars
transform solar energy into chemical energy
produce sugars from CO2 & H2O
Semi-autonomous
moving, changing shape & dividing
can reproduce by pinching in two
Who else divides like that?
bacteria!

22. Chloroplasts
Why are chloroplasts green?

23. Mitochondria & chloroplasts are different
Organelles not part of endomembrane system
Grow & reproduce
semi-autonomous organelles
Proteins primarily from free ribosomes in cytosol & a few from their own ribosomes
Own circular chromosome
directs synthesis of proteins produced by own internal ribosomes
ribosomes like bacterial ribosomes
Who else has a circular chromosome not bound within a nucleus?
bacteria

24. Endosymbiont theory Mitochondria & chloroplasts share similar origin
Prokaryotic cells engulfed by ancestors of eukaryotic cells
Endosymbiont =cell that lives within another cell (host)

25. 1981 | ?? Endosymbiosis theory
Mitochondria & chloroplasts were once free living bacteria
engulfed by ancestral eukaryote
Endosymbiont
cell that lives within another cell (host)
as a partnership
evolutionary advantage for both
one supplies energy
the other supplies raw materials & protection
Lynn Margulis
From hypothesis to theory!
Paradigm shifting ideas in evolutionary biology.
Lynn Margulis
U of M, Amherst

26. Endosymbiosis theory
Evolution of eukaryotes

27. Another good example of cell compartmentalization!
Peroxisomes
Functions: break down fatty acids (and send to mitochondria for fuel); detox alcohol
Involves production of hydrogen peroxide (H2O2)
Another good example of cell compartmentalization!

28. Cytoskeleton: network of protein fibers
Function: support, motility, regulate biochemical activities

29. 3 Types of Cytoskeleton Fibers:
Microtubules
Microfilaments
Intermediate Filaments

30. 3 Types of Cytoskeleton Fibers:
Microtubules
Microfilaments
Intermediate Filaments
Protein = tubulin
Largest fibers
Shape/support cell
Track for organelle movement
Forms spindle for mitosis/meiosis
Component of cilia/flagella
Protein = actin
Smallest fibers
Support cell on smaller scale
Cell movement
Eg. ameboid movement, cytoplasmic streaming, muscle cell contraction
Intermediate size
Permanent fixtures
Maintain shape of cell
Fix position of organelles

32. Centrosomes: region from which microtubules grow
Also called microtubule organizing center
Animal cells contain centrioles (not in plants)

33. Centrioles Structure Function one pair in each cell
help coordinate cell division
only in animal cells

34. Cilia & Flagella Flagella: long and few; propel through water
Cilia: short and numerous; locomotion or move fluids
Have “9+2 pattern” of microtubules

35. Extracellular Matrix (ECM)
Structure:
Outside plasma membrane
Composed of glycoproteins (ex. collagen)
Function: Strengthens tissues and transmits external signals to cell

36. Intercellular Junctions (Animal cells)
Tight junctions: 2 cells are fused to form watertight seal
Desmosomes: “rivets” that fasten cells into strong sheets
Gap junctions: channels through which ions, sugar, small molecules can pass

37. Intercellular Junctions: Plant Cells
Cell wall: protect plant, maintain shape
Composed of cellulose
Plasmodesmata: channels between cells to allow passage of molecules

38. Plant Cells Only
Animals Cells Only
Central vacuoles
Lysosomes
Chloroplasts
Centrioles
Cell wall of cellulose
Flagella, cilia
Plasmodesmata
Desmosomes, tight and gap junctions
Extracellular matrix (ECM)