Cell Biology Exam 2 Flashcards
General functions of the Golgi Apparatus
finish any post-translation modifications
package these proteins into vesicles
ship vesicles to either the plasma membrane or other organelles
-not generally seen in the Light microscope
-in EM’s seen as series of 5-7 flattened membranes sacules
4 functional divisions
“cis” compartment - vesicles budding side of golgi faces ER, newly synthesized proteins and lipids are modified
“medial” compartment - receives vesicles that have pinched off the edges of the cis sac, further modifications
“trans” compartment - concave side of golgi faces away from ER, vesicles contain stuff released to surroundings
“trans golgi network” - of vesicles having budded from trans, waiting to be shipped
Protein golgi is known to be rich in
Glycosyltransferase - embedded in the golgi membrane and faces the cisternal side of the sacs, add or modify sugar chains to create glycoproteins, also present are a variety of other receptors and sorting proteins
3 Major functions of Golgi apparatus
Lysosome formation
Secretory vesicle formation
Plasma Membrane renewal
Lysosome formation
membrane bound organelles that contain an array of digestive enzymes of class known as hydrolase, these enzymes are sorted by golgi -process is mannose ogliosaccaride on hydrolyses, shuttled to the golgi cis-compartment, in cis compartment the mannose flag is phosphorylated by enzyme glucosamine phosphotransferase, the hydrolyses are gathered by golgi membrane by receptors called mannose-6-phosphate receptors
Secretory Vesicle Function
these are products separated from hydrolyses
shipped to membrane and released
Plasma Membrane Renewal
secretory vesicles merge with plasma membrane thereby duming interior contents
adding new phospholipids to the surface
add membrane bound proteins
Two forms of Exocytosis from the Golgi
constitutive- the default path of such vesicles and their contents, movement to the surface conducted by cytoskeleton
regulated - vesicle binds to the cytoskeleton and is only regulated when the cell is stimulated
Lysosomes
dissolution body
size and number vary greatly but common in all cells
rich in digestive enzymes called hydrolyses
newly formed lysosomes are called primary lysosomes
when primary lysosomes merge with an endosome they are called secondary
3 Major Functions of Lysosomes
autophagy
heterophagy
external operations
Autophagy
self digestion
part of normal turn over of organelles
down regulation of receptors on plasma membrane
Heterophagy
digestion of foreign materials
phagocytic digestion of other cells/tissues
External Operations
an uncommon use of lysosomes for extracellular digestion:
- osteoclasts; normal bone recycling
- special neutrophilic attack - vigorous defence seen in chronic inflammatory, autoimmune diseases and seen in some aggressive infections
Summary of Lysosomes
-have many subtypes of hydraulic enzymes
all are needed to adequately digest any potential substrate
if any enzyme is missing it will not be able to fully digest material leading to disease, storage of residual body
know as lysosome storage diseases
Mitochondrion
means thread granules, size and number vary greatly
they appear as a cylindrical organelle
possess 2 enclosing membranes
constantly moving
Outer Mitochondrial Membrane
isolates organelle from the rest of the cytoplasm and is rich in IMP called porin which allows for significant free-passage
Inner Mitochondrian membrane
is thrown into shelf like folds called cristae that crosses the interior
- number of cristae is directly related to ability to produce ATP
- contains proteins of the electron transport system ATP synthesis and the F1-particle and various transporters related to oxidative phosphorylation
- also a high concentration of phospholipid called cardiolipin which decreases the permeability of the membrane
Inner Membrane Space
separates the IMM and the OMM
it is an H+ accumulation area and many molecules found in transit in and out
Matrix
filles the interior of the organelle
contains enzymes of the Krebs cycle
also contin nucleic acid machinery, includes looped DNA ribosomes and tRNAs
The organelle does the following functions
ADP+p, Carbs and Fat, O2 - IN
ATP, heat, H20 and CO2 - OUT
- oxygen is burned with metabolic food to produce carbon dioxide and water and heat
-the ultimate purpose is to convert ADP to ATP
Oxidative Phosphorylation
refers to the oxidation/reduction reactions that utilize oxygen as an acceptor of electrons with the associated phosphorylation of ADP
the broad theory for how mitochondrion pulls electrons off is often terms the chemiosmotic coupling hypothesis
the 3 major components of this process are:
glycolysis
krebs cycle
electron transport system
Glycolysis
- conversion of glucose to pyruvate in the cytoplasm
- pyruvate enters the matrix and is converted to Acetyl CoA
Krebs Cycle
acetyl CoA enters a series of reactions
results in production of CO2 and electrons and protons
electrons and protons received by reducing agent mostly NAD
Electron Transport System
NADH+ oxidation leads to the release of H+ and electrons
H+ pump pulled across the IMM to the inter membrane space
electrons pulled along and thru the IMM by way of many IMPs
the separation of these charges creates a potential energy
cariolipin tends to keep the protons out thus creating a battery
IMM potential is about -160mV and the matrix pH is about 8
Proton Motive Force
the real action that happes on/in the IMM as it is fed with raw materials fromt he matrix and this actiond creates a powerful electrochemical gradient
it is maintained by the insulation of the phospholipids called cariolipin
the discharge of this force is done in a controlled fasion
ATP Synthetase
special re-entry protein and enzyme of the IMM
it is otherwise called the F1 particle, it allows for H+ to re-enter the matrix as it converts an ADP to an ATP
The transporting proteins of the IMM involved in the energy producing process
there is an antiporter of Pi and OH- and another one for ADP and ATP
O2 and CO2 are able to move thru the membrane with notmuch resistance
5 major complexes within the IMM that make up the ETS
Complex 1 often called NADH dehydrogenase
Complex 2 often called fumerate reductase
Complex 3 often called cytochrome b-c
Complex 4 often called cytochrome c oxidase
Complex 5 is ATP synthetase
Iron is nested in these complexes and there are non-protein ubiquinones in the IMM too that are used to shuttle electrons
Brown fat cells
they have mitochondrion with leaky IMMs
these produce little ATP but a lot of heat and is seen in animals that hibernate.
Endosimbyotic Theory
they are semi-autonomous organelles that have many of the same propertiese as bacteria: same size, independant loops of DNA, transcription and translantion, can generate ATP, can reproduce, can regulate their pH, are contained in a second membrane
the idea is that two organisms joined in a symbiotic relationship eons ago such that: bacteria prvided ATP and gained protection, the eukaryotic parent cell provided nutrients and protection and gained valuable energy, the symbiotic combination allowed for massive explosion of oxygen-dependant multi-cellular organisms
decendants of ancient organelles because of the suggested common lineage
Functions of the Cytoskeleton
maintain cellular morphology respinsible for cellular motility contraction of a cell transport vesiucles through the cytoplasm organize the cytoplasm external movements
Basic Component families of Proteins in cytoplasm
microfilaments- solid rod of varying thickness
microtubules - hollow tube-like rods
protein-motors - small associated golbular proteins that work with these microfilaments and microtubules
other associated proteins - of variable size, shape and number
Microfilaments
thin, intermediate and thick
just classified by thickness of the protein
Thin - Actin
made of small bead-like sub-unit called G-actine monomers that are assembled into a helical polymer called F-actin
can have a + growing end and a - shrinking end
major component of contractile apparatus in muscle cells representing about 10% of total protein in those cells
other proteins associated with actin are troponin and tropomyosin, critial in muscle contraction
comes in several iso-forms; there are 6 actin genes in the human cell
tropomin is a Ca2+ regulated protein and it influences rope like tropomyosin to make available binding sites of G-actine collectively this is the thin filament in muscle
Thick - Myosin
a unique enzyme that can be assembles with other myosin to form interesting myosin structures, their head region has the capacity to walk on actin by hydrolizing ATP-thus they are considered protein motors
a major component of contractile apparatus in muscle cells, but, like actin present in nearly all cells
other proteins often associated with myosin (chaperones)
actin and myosin work together in muscle cells - sliding filament theory.
head is the key element in motor movement
regulation of all this is governed by cytosolic Ca2+ concentration therefor tropomyosin in the on and off regulator of this myosin movement
Sliding Filament Theory
- ATP used to change the conformation ->changing association with G-actin
- ATP is also used to setup a POWER STROKE->bound to nearby g-actin and ADP is removed
- the only way it can bind is in the presence of Ca2+ to land on troponin attachment site -RIGOR COMPLEX
- hydrolysis of ATP and subsequent release of ADP creates the power stroke
