1. Structure & Function of eukaryotic organelle2

2. Golgi complex, GC
It is made up of several vesicles and a stack of flattened cisternae.
structure of GC

3. Polarity structure of GC
cis/forming face: the side face to the ER

4. flattened cisternae is main part of GC

5. Polarity structure of GC
trans/mature face: face towards the cell membrane

6. Protein modification in GC
Glycosylation-- GC add carbohydrate groups to a glycoprotein.
Those secretory proteins and membrane integral proteins should be glycosylated.
o-linked glycosylation : linkage with oxygen of hydroxyl group of serine/threonine, occurs in GC
Glycosylation in ER
N-linked

7. Protein modified in GC
In the GC, oligosaccharides unit are modified, creating a diversity of carbohydrate structures on the proteins.

8. The retrograde transport from GC to ER can transport resident ER proteins back to ER’s lumen (sequence KDEL at C terminus)/membrane (sequence KKXX at C terminus)
KDEL(Lys-Asp-Glu-Leu)
KDXX(Lys-Lys-X-X)

9. Proteins sorting and distributing to next stop.
After proteins have been modified in GC, the vesicles package and transport them to the final destination.
The secretion allows cells to release proteins to the external environment, delivers proteins and lipids to the cell membrane, like those go to intracellular organelles.

10. Proteins can be secreted out of cell by
The constitutive pathway：vesicles constantly leave GC and fuse with cell membrane.
The regulated secretory pathway： secretion requires a stimulus to trigger.

11. GC → lysosome
Synthesized in RER, the lysosomal hydrolases are tagged with a phosphorylated carbohydrates group (mannose 6-phosphate, M6-P) in GC.
The group works as a sorting signal and binds MPRs at the TGN.

12. GC → lysosome
The binding is regulated by PH (strong at neutral PH and weak at acidic PH) .
After then they are packaged into clathrin-coated vesicles.
Without M6-P, suffer I-cell disease.

13. GC → lysosome
A clathrin protein is a triskelion (3 legs). Each leg is made of a heavy chain and a light chain.
The triskelion can polymerize to form a polygonal cage surrounding the vesicles.

14. GC → lysosome
Adapter protein 1 (AP1) bind clathrin and receptors as adapter protein. Arf-1s work as GTPase.
Clathrin will dissociate after vesicle release.

15. GC → lysosome Vesicle fused with late endosome
The pH of the early endosome is neutral, while in the late endosome is lower, cause dissociation of M6P and MPR.
M6P is removed at last.

16. lysosome Lysosomes contain lots of acid hydrolytic enzymes.
All the enzymes are optimally active in the acidic conditions ( PH = 5 ) maintained within lysosomes.

17. structure of Lysosome
The membrane keeps stable because there is a protective polysaccharide layer which coat the lumen side of lysosome membrane.

18. function of lysosome
Digest macromolecules/old organelles within the cell and thus allow them to be replaced with fresher, more effective ones.
Defense from microorganisms/bacteria via phagocytosis.

19. Receptor-Mediated Endocytosis of LDL
function of lysosome
Digest macromolecules intake to cell by endocytosis and provide nutrients for cell.
clathrin
LDL
Receptor-Mediated Endocytosis of LDL

21. Mitochondrion
The main function of mitochondria is to generate ATP for biological activities.
metabolism of carbohydrate / fatty acid / amino acid.
Ca2+ storage

22. structure outer membrane encloses the entire organelle
inner membrane encloses a fluid-filled matrix
There is intermembrane space between membranes

23. The outer membrane
It contains many integral proteins (porins) that form channels through which small molecules and ions move in and out of the mitochondrion freely.

24. The inner membrane
It is much more impermeable than the outer membrane and few molecules can pass through it freely.
highly convoluted so that a large number of infoldings called cristae are formed, which expand maximum surface for chemical reactions to occur within the mitochondria.

25. Cristae are studded with proteins
Proteins include:
that perform the redox reactions of oxidative phosphorylation (the electron transport chain)
ATP synthase, which generates ATP in the matrix
Specific transport proteins that regulate metabolite passage into and out of the matrix

26. The Matrix
The matrix contains enzymes that catalyze the oxidation of pyruvic acid and other small organic molecules include DNA , RNA and ribosomes.
Encode 13 proteins, 2 rRNAs, 22tRNAs

27. Cellular Respiration and Energy Conversion
Cellular respiration is the process of oxidizing energy molecules (glucose) to CO2 and H2O.
The energy released is trapped in the form of ATP for use by all the energy-consuming activities of the cell.
ATP
ADP
phosph.
A-P～P～P A-P～P + Pi KJ
dephosph.

28. Cellular Respiration and Energy Conversion
Energy Conversion includes 3 steps:
glycolysis
tricarboxylic acid cycle, TAC
oxidative phosphorylation

29. Glycolysis
converts glucose into pyruvate. The free energy released in this process is used to form the ATP and NADH (reduced nicotinamide adenine dinucleotide) + H+.

30. Tricarboxylic/Citric acid cycle, TAC
Product:
NADH + H+
FADH2
ATP、CO2

31. oxidative phosphorylation
The electrons of NADH and FADH2 are transferred to molecular oxygen, via respiratory chain, with energy released.

32. respiratory chain / electron transport chain
The energy released can be used to pump protons (H+) from the matrix to the intermembrane space, against their concentration gradient.
Energy will be used to generate ATP
1 NADH → 2.5 ATP 1 FADH2 → 1.5 ATP

33. Theory of chemiosmotic coupling
The electron transport chain perform the electron transfer and the release of energy and pump protons (H+) into the intermembrane space.
As the proton concentration increases in the intermembrane space, a strong electrochemical gradient is established across the inner membrane.

34. Theory of chemiosmotic coupling
The protons can return to the matrix through the ATP synthase complex, and their potential energy is used to synthesize ATP by ADP and inorganic phosphate (Pi) binding.

35. ATP synthesis
ATP synthase can catalyses the synthesis of ATP. The process is driven by the proton motive force across the inner mitochondrial membrane.
Elementary particle
/ATP synthase complex

36. ATP synthesis
consists of two subunits : The catalytic subunit (F1) and a hydrophobic proton channel subunit (F0).

37. The transport of mito. proteins.
Most mitochondrial proteins are encoded by nuclear genes, necessitating a mechanism to target and import those proteins into mitochondria.
Similar to ER proteins importing, mito. proteins contain a cleavable signal sequence that targets mitochondria.
post-translationally import

38. Mito. proteins should be kept unfolded in the cytosol by chaperones(hsp70s).

39. There are two sets of translocators on mito
There are two sets of translocators on mito. outer/inner membrane that allow passage of proteins.
Targeting the matrix, signal sequence usually resides at the N-terminus.

40. In the matrix, chaperones (mthsp70) “pull” the protein across the inner membrane, with ATP hydrolysis.
The proteins fold inside the matrix with sequence cleavage.
Proteins targeted to the outer membrane are translocated into the intermembrane space , then imported into the outer membrane by the SAM translocator.

41. some proteins contain a second or stop transfer sequence to target the inner membrane, recognized by the TIM complex. 41

42. The end