BCOR 103:Cytoplasm
110 Cards in this Set
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Cytoskeleton function
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1. scaffolding
2. organelle positioning
3. support for organizing machinery of macromolecular metabolism
4. movement of materials and organelles
5. locomotion
5. transduction of extracellular signals
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The "cell skeleton" is made up of __.
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- architectural nucleus proteins
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The cytoskeleton is made up of: (2)
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1. cytoplasmic filaments and their associated proteins/factors
2. material that remains between the nuclear envelope and plasma membrane after cell lysing and washing
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primary set of cytoskeleton filaments (4)
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1. microtubules
2. intermediate filaments
3. microfilaments
4. thick filaments
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microtubules
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-hollow tubulin tubes
-used in division and intracellular support
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intermediate filaments are __ that ___.
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- rope like fibers
- resist mechanical stress
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Microfilaments are made up of __ and involved in ___.
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-globular chains of actin protein
-involved in cellular elasticity and motility
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thick filaments are made up of __ and are used in ___.
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-rough, bipolar aggregates of myosin protein
-contractile activities of cells
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Isoforms
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-different distinct functional versions of the cytoskeleton
-easily broken down and rebuilt
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general areas of eukaryotic cytoplasm (2)
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1. cortical cytoplasm
2. subcortical cytoplasm/endoplasm
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Cortical cytoplasm structure/location
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- Mostly microfilaments
-thin, gel like area beneath the plasma membrane
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cortical cytoplasm function
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- exclude other organelles from the region
- maintain cell shape
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Subcortical cytoplasm/endoplasm
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-syrup like
-most organelles found here
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nuclear lamins
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-subgroup of intermediate filaments present in all eukaryotic nuclei
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Cyotplasmic IFs are found in __ but not in __.
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-mammalian animal cells
- plant cells
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Subtypes of IFs (5)
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1&2. keratins
3. Desmin, vimentin, GFAP
4. (neurons) 3 neurofilament proteins combined as a homo/heterodimer
5. copolymers of nuclear lamins A,B,C
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IF protein structure
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-N and C terminal globular domains
-central rod domain
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Essentially all of the differences in the 5 IF subtypes exist in the ____.
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globular domains
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Globular domain function
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- controls the assembly of proteins
- connects intermediate filaments with non-IFs
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central rod structure
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-alpha helical heptad repeat sequence
-six steps in assembly
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6 steps of central rod structure assembly
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1. formation of coiled-coil dimer
2. anti-parallel and half staggered dimer association into a tetramer
3. end to end association of tetramers into "protofilament"
4. pairs of protofilaments associate laterally into an "eight chain"protofibril
5. four protofilaments wrap around each o…
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tonofibrils
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- hemidesmosomes attach to intermediate filaments of cytosketon
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IF network regulation
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-"pool"of ready dimers/tetramers to make IFs
-Assembled/disassembled quickly in cycles through phosphorylation/dephosphorylation
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IF function
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-increase efficency and provide protection
-greatest resistance to stress
-position organelles
-organize sarcomeres
-support membrane
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microtubules are comprised of ___ subunits.
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tubulin
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Tubulin is made of ___ and ____ ____.
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Alpha
beta subunits
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Tubulin subunits are __ ___ proteins.
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guanine binding
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When alpha and beta tubulin subunits associate, they form a
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protofilament
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___ are formed when __ tubulin protofilaments bind to form a hollow cylinder
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Microtubule
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Microtubule associated proteins (MAPs)
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- specifically bound materials on the surface of microtubules/alpha beta subunits
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MAP subgroups (3)
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1. Structural
2. Specialized
3. Microtubule based motors
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Structural MAP function
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Enhance properties of their microtubule
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Specialized MAP function
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Proteins that are unique to a distinct MT function of a specialized cell type
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Microtubule based motor function
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Use microtubules as "tracks" for cellular motility
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3 stages of MT formation
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1. Lag
2. Elongation
3. Steady state
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Lag phase
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- dependent on MAP proteins
- ring of tubulins form
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Elongation phase
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addition of the alpha/beta dimers to the ends of the protofilaments elongating the MT
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steady state phase
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-Length of microtubule (MT) is in "equilibrium" with the amount of unpolimerized alpha/beta subunits
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Critical concentration
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The concentration of free tubulin (a/b subunits) at the steady state of MT formation
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If the free tube concentration goes down, the MT length __
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goes down
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Microtubule organizing center (MTOCs)
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distinct areas where MTs originate
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Important properties of MTOCs
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1. synthesize new MTs, even when free tubulin is below critical concentration
2. hold the slower growing (-) end of MTs, allowing more growth at the faster end (+)
3. MTOC synthesis is saturable and regulatable
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MTOC types/examples (3)
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1. Basal bodies (cilia/flagella anchor)
2. spindle pore body (organize mitotic spindle in yeast)
3. centrosome
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centrosome structure
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-Pair of centrioles
-pericentriolar material
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MTs originate from ___ in centrosomes
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-pericentriolar material
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What is dynamic instability
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- polymerized and free tubulin are in balance
- some MTs grow while others shrink
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What do MTOCs do during interphase
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send out MTs in all directions
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MTs can grow outside of the ___ ___.
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cell membrane
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If MTs remain stable long enough, they:
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are chemically modified with MAPs
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When do MTOCs/centrosome duplicate?
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at the beginning of mitosis
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Aster MTs
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- MT generated in a cell with to MTOCs
- shorter
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Chromsomes act as a __ on MTs
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Cap
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Microtubule motors
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- couple vesicles to an MT and move them faster than diffusion
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Classes of microtubule motors (2)
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1. kinesin class
2. dynein class
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Kinesin class motors
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- Two heavy chains that house two globular ATPase motor heads
- Two light chains that form the cargo-carrying tail.
- "walk"down the MTs with the cargo
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Dynein class motors
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- Active proteins in the movement of cilia and flagella
- this class moves toward the - end of MTs
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Primary protein subunit of microfilaments is
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Actin
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Describe actin structure
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- Globular protein
- Bi-lobed protein which binds ATP in the cleft
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- Globular protein
- Bi-lobed protein which binds ATP in the cleft
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- double helix
- polymerized actin monomers
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microfilaments are __ in diameter
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6 nm
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T/F microfilaments are the longest structural subunits
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False; shortest
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similarities between MTs and microfilaments
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- both have a + growing end and a - slow growing end
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Describe treadmilling
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-found in microtubules
- subunits are taken from - end and added to + end
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microfilaments alone don't strongly associate with anything. In order to perform their function they need __ and __ __ __.
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- microfilament
- actin associated proteins
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Families of microfilament associated proteins (4)
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1. monopolar binders
2. capping proteins
3. linking proteins
4. motor proteins
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Monomer binder function
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- only bind to free actin
- regulates microfilament formation
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3 jobs of capping proteins
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1. cap one end of microfilament (usually + end, confining growth to - end)
2. sever the microfilament by binding to the side of it
3. nucleation creates a new filament growth protein
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Linking protein subclasses (3)
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1. bundlers hold microfilaments side by side for additional strength (myosin, microvilli)
2. cross linkers put microfilaments across one another, forming a gel
3. membrane linkers connect microfilaments to the membrane by their end or side
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Motor proteins are also known as:
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myosins
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Two groups of motor proteins
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1. Myosin I
2. Myosin II
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Describe Myosin II
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-Myosin in muscle
- Made of 2 heavy chains, 2 light chains, and 2 regulatory light chains
- 2 globular heads and a tail
- view figures for how chains move
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Describe Myosin I
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- 1 motor head
- no tail
- end of these molecules has binding sites for either a filament or membrane lipids
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Myosin I function
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Myosin I function
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4 stages of locomotion
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1. polarity determination
2. leading edge protrusion
3. substrate adhesion
4. traction/cell body positional change
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Describe polarity determination
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- occurs in response to an orientated signal
- dependent upon the capture and orientating of the microtubule network
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Describe protrusion
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Microspikes that probe foreward
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Microspikes
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a thin tube of cytoplasm supported by a bundle of actin filaments or lamellipodia
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lamellipodia
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a broad thin band of cortical cytoplasm packed with a meshwork of actin filaments
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3 proposed mechanisms for the generation of the protrusive force that is required to extend the protrusions forward?
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1. Actin polymerization: rapid growth of filaments pushes membrane outward
2. actin/myosin/membrane interaction: myosin I propels actin rods against membrane
3. Gel osmotic forces: concentration of particles below membrane brings in water and expands membrane
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Describe substrate adhesion
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when protusions encounter an adhesive region of the substratum it will adhere, stabilizing foreward expansion
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Describe traction/body movement that shifts cell towards protrusion
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1. stress fiber contraction (rear of the cells contract due to sarcomere-like stress fibers, pulling cell foreward)
2. Motor protein induced cytoplasmic flow (fluid is "rowed" forward by minimyosins)
3. general cortical tension (cytoplasm pushed foreward)
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IF subtypes I and II and both __ which exist as __ and are only expressed in __ _.
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- keratins
- heterodimers
- epitheilal cells
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Mitochondria can _ _ causing elongated organelle networks
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fuse together
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4 structures of mitochondria
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1. Outer membrane
2. intermembrane space
3. inner membrane
4. the mitochondrial matrix
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1. Outer membrane
2. intermembrane space
3. inner membrane
4. the mitochondrial matrix
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-high concentration of mitochondrial porin (form beta barrels)
- 5000MW substances or smaller can pass through
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intermembrane space
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-between outer and inner membranes
- metabolic content roughly matches cytosol, but with different proteins (and fewer)
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primary protein found in intermembrane space
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-electron transporter cytochrome-c
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general description of inner membrane
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-Folded into cristae to increase surface area, with more cristae for greater energy needs.
- Not smooth, has many projections.
-Very impermeable.
-High protein content (transporters, electron carriers, enzymes)
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Two regions of inner membrane
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1. inner boundary membrane
2. cristae proper
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inner boundary membrane
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directly opposes the outer membrane, rich in metabolite transporters and protein translocators
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Cristae proper
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Rich in electron transport chain compoents and ATP-synthase
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cristae junctions
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specialized membrane constrictions that attach the cristae proper to the inner boundary membrane
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mitochodrial matrix
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- fluid component of the mitochondria
-densely packed with proteins and other particles
-Contains enzymes and metabolites of the citric acid cycle and beta-oxidation.
-Also contains the DNA and ribosomes that make the mitochondria semi-autonomous.
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The electron transport chain uses __ from __ __ of __ to produce __ which is subsequently used to produce __.
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-electrons
-oxidative reactions
-catabolism
- electrochemical, energy storing gradient
-ATP
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What does the electron transport chain do with the electrons
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What does the electron transport chain do with the electrons
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steps using complex 1 of the electron transport chain
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- over 20 subunit proteins embedded in inner membrane
-Receives an electron from NADH, creating NAD- and releasing H+ into the matrix. Electrons pass one-at-a-time to a molecule of Coenzyme Q (CoQ). Movement of electrons releases energy that allows the complex to pump 4 H+ from the matri…
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steps using complex 2 of the electron transport chain
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Succinate is oxidized and its electrons/hydrogens are transfered to FAD producing FADH2. Complex 2 releases H+ into the matrix, and transferers electrons to CoQ, but lacks the energy to transport H+ across the membrane.
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Steps using complex 3 of the electron transport chain
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Complex 3 has a large binding pocket for CoQH2, which binds and releases its H+ to the intermembrane space. The complex then transfers one electron to Cytochrome-c and one to a different CoQ molecule. This happens twice, providing a second electron to the second CoQ molecule and allowing …
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What is the name of the cycle that complex 3 is involved in?
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Q-cycle
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The Q cycle allows CoQ to shuttle how many hydrogens to the intermembrane space per pair of electrons transported along the chain?
4 H+ per electron
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4 H+ per electron
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Steps using Complex 4 of the electron transport chain
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The electrons from cytochrome-c (a mobile electron carrier) are transported from complex 3 to 4. Subunit is used for binding molecular oxygen, transferring electrons to the oxygen creating reactive oxygen species, absorbing H+ from the matrix and uniting them with reactive oxygen to form …
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primary function of the electron transport chain is to
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Move H+ from the matrix to the intermembrane space
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When an electron pair from NADH is inserted into electron transport chain, how many H+ are transferred from which complexes
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-4 are transported by complex 1
-4 are transported by the Q-cycle (complex 3)
-2 are transported by complex 4
- 10 in total
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when an electron pair is transferred from FADH2, how many H+ are transported from which complexes?
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- 6 H+ are isolated from complex 2, which are not transferred to the intermembrane space until complex 4
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Proton-motive force
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- The name for dual concentration and electrical gradient across the inner membrane
- utilized to create ATP
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FoF1 synthase is a __ type pump used in to produce _ using the __ __.
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- F
- inner membrane
- ATP
- H+ gradient
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3 steps for the production of ATP using FoF1 ATP synthase
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1. H+ is transferred from the intermembrane space to the matrix through the pore in synthase. This causes the c-ring of the protein to rotate.
2. As this part rotates, it causes a rotor unit to rotate as well. The rotation of the rotor causes a conformational change in the beta subunits …
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How many ATP molecules can be produced from one glucose molecule?
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How many ATP molecules can be produced from one glucose molecule?
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How many ATP molecules are released per rotation of the rotor in FoF1 ATP synthase?
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How many ATP molecules are released per rotation of the rotor in FoF1 ATP synthase?
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What are the 3 conformations of the beta subunits in FoF1 ATP synthase
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1. Loose (allows the binding of ATP and Pi
2. Tight (combines two previous substrates into ATP)
3. Open (release ATP)
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BCOR 103:Cytoplasm