Cell Biology: Chapters 15 + 16

COP I-coated vesicles

retrograde transport within Golgi and from Golgi back to ER

COP II-coated vesicles

ER to Golgi

Clathrin-coated vesicles

Golgi to endosome (sorting) Plasma membrane to endosome (endocytosis)

Soluble proteins

• proteins secreted continuously (constitutively)

• proteins subject to regulated secretion

• proteins resident in the rough ER lumen

• Proteins resident in the cis, medial, or trans Golgi compartments

• Lysosomal proteins

membrane proteins

• proteins resident in the rough ER membrane

• Proteins resident in the cis medial, or trans Golgi membranes

• Lysosomal membrane proteins

• Plasma membrane proteins

vesicle transport involves

• formation of vesicle from “donor” organelle

• fusion of that vesicle with “acceptor” organelle

assembly of protein coat

vesicle budding driven by

distinctive protein coat on cytosolic surface

• termed “coated vesicles”

vesicles budding from membranes contain

to allow vesicle to fuse to next compartment

coats are lost after vesicle budding

which organelle vesicles arise from

coats differ depending on

Rab GTPases

lipoproteins specific to each vesicle type

• interact with tethering protein on target membrane

  • initial recognition reaction

V-SNARE

vesicle targeting protein

T-SNARE

target recognition protein

• integral membrane proteins

• docking specificity

docking

• snares interact forming coiled coil

• pulls vesicle to membrane

• vesicle with wrong V-snare does not dock

T-SNARE and V-SNARE interact allowing

Vesicle Fusion

• Fusion proteins bring docked vesicle and acceptor membrane together

• assemble fusion proteins

• RAB GTP hydrolysis control fusion

• neurons

• muscle cells

• endocrine cells

• egg cells

electrically excitable cells include

voltage-gated cation channels

• these channels generate action potentials

• action potential is generated by a depolarization of the plasma membrane i.e. a shift in the membrane potential to a less negative value

Electrically excitable cells include

depolarizing the presynaptic membrane

1. AP arrives

2. Voltage gated Ca++ channels open.

3. Increase concentration of an intracellular Ca++ causes exocytosis of transmitter into the synaptic cleft

action potential arrives at the synapse,

Golgi Network

signaling occurs in the trans

sorts

• Vesicle membrane and integral membrane protein part of plasma membrane

• No targeting signal

• Default pathway

Golgi ___ proteins for the plasma membrane

vesicles in the trans Golgi network

proteins are packaged in

plasma membrane and protein released

vesicles fuse with

• peripheral membrane proteins

• secreted to environment

aggregate

proteins ___ in Golgi and packaged in secretory vesicle

accumulate

vesicles ___ near plasma membrane

signal

• neurotransmitter

• insulin release in response to blood glucose

fusion controlled by external

exocytosis

• glucose facilitated transporter in response to insulin

• H+/K+ ATPase of stomach in response to histamine

regulated ___ of integral membrane proteins

basket-like coat on surface of trans-Golgi membrane; promotes vesicle formation

Clathrin

adaptins

Clathrin coat also contains

clathrin-coated vesicles

In Golgi, proteins containing mannose-6-PO4 get packaged into

Dynamin

a GTP-binding protein; assembles around neck of budding vesicle

three

patheways to degredation in lysosomes

lysosomes

multiple pathways deliver materials (derived from different sources) to

vesicles to early endosomes to late endosomes to lysosomes

endocytosed vesicles mature from

digestion

lysosome is a major site of cellular

phosphate

mannose 6 phosphate tag: ___ is added in the golgi

fusion

transport of newly synthesized lysosomal hydrolases to the lysosome

plant vacuole

major space in center of plant cell

digestive compartment

plant vacuole is a

ions, sugars, amino acids, toxic waste

plant vacuole acts as storage for

cell rigidity

plant vacuole maintains

ion rich

• energy pumps in

• water enters providing rigidity

plant vacuole is a(n) ___ ___ environment

constitutive and regulated

two types of secretory activities

constituitive secretory activity

transported from site of synthesis and secreted continuously

regulated secretory activity

• materials to be secreted are stored in large, densely packed, membrane-bound secretory granules

• discharged following specific stimulus

  • examples: endocrine cells, acinar cells, nerve cells

multisubunit protein complexes that function as translocators

protein translocation across the mitochondrial membranes is mediated by

TOM complex

functions across the outer membrane

TIM complexes

• TIM 23

• TIM 22

Function across the inner membrane

rid the body of toxic substances like hydrogen peroxide, or other metabolites.

perxisomes function to

• self assembling, 1 day lifespan

• arose due to oxygenation

• self replicating

peroxisome

50 different enzymes

Lipid metabolism:

ß-oxidation of Very Long Chain Fatty Acids (VLCFA)

-provides the cell with a major source of metabolic energy

Hydrogen peroxide breakdown: catalase

Lipid biosynthesis (cholesterol)

Amine and bile acid synthesis

Purine catabolism by urate oxidase

peroxisome function

translocation

active transport