Midterm #4 Flashcards
(124 cards)
1
Q
where does glycolysis occur?
A
the cytoplasm
2
Q
pyruvate is made in both ____ and ____
A
glycolysis; fatty acid metabolism
3
Q
what is the net gain in glycolysis?
A
- 2 ATP
- 2 NADH
4
Q
the citric acid/krebs cycle uses ____ and transforms it into ____
A
pyruvate; acetyl-coA
5
Q
where does the citric acid/Krebs cycle occur?
A
the matrix of the mitochondria
6
Q
what is the net gain from the citric acid/Krebs cycle?
A
- 2 ATP
- 8 NADH
- 2 FADH2
7
Q
oxidative phosphorylation generates about ____ molecules of ATP
A
32
8
Q
the outer membrane of the mitochondria is ____ versus the inner membrane which is ______
A
permeable; impermeable
9
Q
where is the mitochondria genome located?
A
matrix of the mitochondria
10
Q
what is cardiolipin?
A
a mitochondrial lipid exclusive to the inner membrane
11
Q
what are the functions of cardiolipin?
A
- plays a role in electron transport chain efficiency
- essential for the curvature of the inner membrane
- facilitates protein import into the mitochondria
- involved in apoptosis
12
Q
what is mitochondrial fusion?
A
the process where two mitochondria merge into a single organelle
13
Q
why is mitochondria fusion significant?
A
it promotes healthy mitochondria by compensating for damaged components
14
Q
which proteins help regulate mitochondrial fusion?
A
Mfn1 and OPA1
15
Q
what is mitochondrial fission?
A
the process where a single mitochondrion divides into two serperate organelles
16
Q
what is the significance of mitochondrial fission?
A
- facilitates cellular distribution of mitochondria during cell division
- allows for isolation and removal of damaged mitochondrial segments
17
Q
which proteins regulate mitochondrial fission?
A
DRP1
18
Q
explain the steps of oxidative phosphorylation using NADH
A
- NADH is converted into NAD+, releasing 1 electron - these e- change the shape of compex I
- protons are pumped across the membrane at the same time
- Coenzyme Q (ubiquinone) gets reduced which allows it to transfer the e- to complex III
- same process occurs at complex III
- cytochrome C transfers the e- to complex IV which pumps more protons across the membrane
- cytochrome C also uses the energy from e- to facilitate rxn between molecular oxygen and hydrogen to create water
19
Q
explain the steps of oxidative phosphorylation using FADH2
A
- FADH2 is converted into FAD, releasing 2 electrons - these e- change the shape of compex II
- Protons are pumped across the membrane at the same time
- Coenzyme Q (ubiquinone) gets reduced which allows it to transfer the e- to complex III
- same process occurs at complex III
- cytochrome C transfers the e- to complex IV which pumps more protons across the membrane
- cytochrome C also uses the energy from e- to facilitate rxn between molecular oxygen and hydrogen to create water
20
Q
what are the overall steps of oxidative phosphorylation?
A
- establish an electrochemical gradient across the inner membrane
- electron transport through the complexes
- ATP synthesis (complex V)
21
Q
What is ATP synthase?
A
an enzyme that couples the flow of protons down their chemical gradient to the synthesis of ATP
22
Q
how many proteins are coded by the mitochondrial proteome?
A
1000-1500
23
Q
what is the purpose of the mitochondrial replacement theory?
A
to prevent transmission of mitchondrial diseases from mother to offspring
24
Q
what is the method of the mitochondrial replacement theory?
A
- combine nuclear DNA from mothers egg with healthy mitochondria from donor egg
- resulting egg has nucelar DNA from mother and mitochondrial DNA from donor
25
what are the techniques for mitochondrial replacement theory?
* maternal spindle transfer (MST) = transfer mothers nuclear DNA into donor eggs w/ health mitochondria
* pronuclear transfer (PNT) = transfer nuclear DNA of fertilized mothers egg into fertilized donor egg w/ healthy mitochondria
26
what are presequences?
positively charged, helical structures that direct proteins to the mitochondria
27
what is the translocase of the outer membrane (TOM) complex?
main entry gate for nuclear encoded proteins that recognizes presequences and faciliates protein import
28
what is the translocase of the inner membrane (TIM) complex?
entry gate that transports proteins from the intermembrane space into the matrix
29
what is the import mechanism for mitochondrial proteins with presequences?
1. presequence binds to receptor site on TOM complex
2. protein is threaded through the TOM channel
3. presequence interacts with TIM 23 complex
4. protein is translocated into the matrix and the presequence is cleaved by the matrix processing protease (MPP)
30
what is the function of the TIM9-TIM10 complex?
acts as a chaperone protein that binds and stabilizes hydrophobic proteins after passing through the TOM complex
31
where is the TIM9-TIM10 complex located?
in the innermembrane space
32
what is the function of the TIM22 complex?
specializes in the insertion of carrier proteins into the innermembrane
33
what is the function of the OXA1 translocase?
integration of proteins synthesizes by mitochondrial ribosomes and importation of some nuclear-encoded protiens into the innermembrane
34
what is the import mechanism for presequence independent protein targeting to the mitochondrial inner membrane?
1. hydrophobic proteins enter the TOM complex
2. proteins are then transiently bound to by the TIM9-TIM10 complex
3. transferred to TIM22 for insertion into the inner membrane
4. some proteins further inegrated by OXA1
35
what are single transmembrane domain proteins?
proteins who destination is the outer membrane
36
what is the function of Mim1?
inserts single transmembrane domain proteins into the outer membrane
37
what are β barrel proteins?
protein that is inserted into the outer membrane
38
what is the sorting and assembly machinery (SAM) complex?
complex that inserts β barrel proteins into the outer membrane
39
what is the process for β barrel protein insertion?
1. transfered through the TOM complex
2. bound by TIM9-TIM10 chaperone proteins in innermembrane space
3. directed to the SAM complex
4. inserted into the outer membrane
40
what is the function of phospholipid transfer proteins?
extract and transport phospholipids
41
where is the transfer site for phospholipid transfer proteins?
occur at regions of close contact between the ER and the mitochondria
42
what is the significance of the phospholipid transfer protein?
* ensures proper lipid composition of membranes
* facilitates lipid exchange between organelles
43
what are peroxisomes?
small membrane bound organelles present in nearly all eukaryotic cells
44
what is a plasmalogen?
a specialized phospholipid
45
what are the functions of plasmalogens?
* contribute to structual integrity of cell membranes
* acts as antioxidants protecting cells from oxidative stress
46
what is the process of assembly of peroxisomes?
V1 and V2 vesicles fuse together
*these vesicles have distinct membrane proteins
47
what is the process of importing peroxisomal matrix proteins?
* protein that contains PTS1 targeting signal is recognized by Pex5
* this complex binds to the docking complex on the peroxisomal membrane
* Pex5 and Pex14 form a membrane pore
* cargo protein is translocated into the peroxisome
* Pex5 is recycled back to cytosol after translocation
48
what are the two ways a peroxisome can be formed?
* de novo formation - fusing of vesicles from ER
* alternative formation - growth and divison of already existing peroxisomes
49
what is the signficance of globular actin?
have binding sites that that mediate head to tail interaction
50
what is the significance of filamentous actin?
can grow at both ends and has polarity
51
actin is _ when bound to ATP and _ when bound to ADP
more stable; less stable and more likely to fall apart
52
what is treadmilling?
when ATP actin is added at the barbed end while ADP-actin dissociates from the pointed end
53
what is the function of formin in actin filament formation?
formin dimers bind to ATP-actin initiating the polymerization of long unbranched actin filaments
54
what is the function of profilin in actin filament formation?
binds to actin monomers and stimulates the exchange of bound ADP for ATP, increasing the local concentration of ATP actin
55
what is the function of Arp2/3 in actin formation?
makes the actin branches
56
what is the function of tropomyosin?
stabilizes the actin filaments by binding lengthwise along the growth of the filament
57
what is the function of capping proteins?
stabilize actin by binding to the barbed or pointed ends
58
actin bundles are supported by _
crosslinking proteins
59
actin networks are connected by _
large, flexible proteins that crosslink orthogonally (90°)
60
actin bundles give rigidity and shape to cell protrusions for _ versus actin networks offer mechanical support and are involved in cellular activities such as _
interactions w/ the environment; mobility and shape changes
61
what is the function of spectrin?
associates with actin contributing to the elasticity and mechanical stability of the plasma membrane
62
what is the composition of spectrin?
tetramertic stucture with 2α and 2β domains
63
where are the actin binding domains located on spectrin?
on the amino (N) terminus
64
what is the function of ankyrin?
severs as a link between the spectrin and actin network and the plasma membrane by binding to the spectrin and band 3 (transmembrane protein)
65
what is the role of protein 4.1 in erythrocyte cytoskeletons?
reinforces the cytoskeleton membrane linkage by associating with spectrin/actin juntions and connecting to glycophorins
66
what are actin stress fibers?
bundles of actin filaments that provide structural integrity
67
what are focal adhesions?
points that indicate contact with the extracellular matrix
68
what is the function of viniculin?
a protein that helps anchor the actin filaments to the cell membrane
69
what is the role of viniculin
plays a role in cell adhesion and and signal transduction
70
what is the compostion of focal adhesions?
comprised of integrins binding to the extracellular matrix (ECM)
71
what is the role of stress fibers?
provide tensile strength and are crucial for contractability
72
what is the function of talins with focal adhesions?
links integrins to viniculin and actin
73
what are cadherins?
transmembrane proteins that mediate cell-cell contacts at adherens junctions
74
what are the protein interactions in adherens junctions?
* β-catenin links caherins to α-catenin
* α-catenin interacts with actin filaments and viniculin anchoring junction to the cytoskeleton
75
actin filaments with microvilli and crosslinked by _
villin, fimbrin, and epsin
76
how are microvilli attached to the plasma membrane?
* myosin I attaches actin filaments to the plasma membrane along their length
* myosin VI is responsible for the attachment at the base of the actin bundle
77
what are the stages of cell migration?
* extension of the leading edge - the cell projects forward through the formation of lumellipodia or filopodia
* attachment of the leading edge - newly extended protrusions ashere to the substratum via focal adhesions
* retraction of the rear - the cells rear contracts and attches, pulling the trailing end forward into the cell body
78
actin polymerization is used for _ , integrin-mediated adhesion for _ , and actomyosin contraction for _ in cell movement
protrusion; attachment; retraction
79
why is actin filament remodelling significant?
crucial for cell movement, especially at the leading edge during migration
80
what are Rho family GTPases?
a family of small GTP binding proteins primarily associated with the regulation of the actin cytoskeleton and cell mobility
81
what is profilins role in actin filament remodelling?
facilitates the ADP to ATP exchange on actin monomers, promoting actin filament extension
82
what is cofilins role in actin filament remodelling?
slices existing actin filaments, generating new (+) ends for further filament growth
83
what is a sarcomere?
an individual unit of muscle fiber
84
what is the composition of the sarcomere?
thick filaments of myosin and thin filaments of actin
85
what are the ends of the sarcomere called?
z-discs
86
what is the middle of the sarcomere called?
the m-line
87
_ filaments are anchored to the m-line and project out in both directions
myosin
88
what is the sliding filament model?
contraction entails the sliding of actin and myosin filaments past each other
89
what is the function of myosin II?
drives filament sliding
90
describe the steps of muscle contraction in terms of the filaments
1. ATP binds to myosin, causing the myosin head to undergo a shape change causing it to dissociate
2. the myosin head binds to a new position on actin
3. when ADP is bound to the myosin head returns to its original position
91
when there is low [Ca2+] _
the tropomyosin-tropinin complex masks the myosin binding site on actin preventing it from binding
92
when there is high [Ca2+] _
Ca2+ binds to troponin which shifts the tropomyosin/troponin complex and the myosin binding site is unmasked which means it can bind to actin
93
what are the differences between muscle and non-muscle contraction?
* muscle cells have highly organized microfibrils w/ repeating sarcomeres
* non muscle cells have less organization
* muscle cell contraction is often synchronous and rapid
* non-muscle cell contraction can be asynchronous and varied in pace
94
what is cyokinesis?
division of the cell after mitosis
95
how is myosin II activated?
through phosphorylation
96
what is calciums role in activation of myosin II?
calcium ions binds to calmodulin, initiating the activation process
97
what happens to calmodulin when it binds with Ca2+?
it undergoes a conformational change
98
what is the MLCK?
the myosin light chain kinase
99
what are unconventional myosins?
myosins that do not form filaments
100
what is the structure of microtubules?
composed of dimers of α-tubulin and β-tubulin that polymerize w/ 13 protofilaments each
101
what is the process of polymerization of microtubules?
1. tubulin dimers w/ GTP bound tubulin asscoate with the growing (+) end while in a flat sheet
2. the flat sheet then zips up into the mature MT just behind the region of growth
3. the GTP bound β tubulin is the hydrolyzed to GDP tubulin which are less stable and lead to dissociation at the (-)
102
what is dyanmic instability?
microtubule shrinkage due to insufficient GTP-tubulin
103
what are the functions of microtubule associated proteins (MAPs) in dynamic instabilty?
regulation of the dynamic behavior of microtubules by binding to their (+) ends
104
what are the functions of microtubule polyermerases?
* accelerate growth of microtubules
* increase the incorporation of GTP-bound tubulin into the microtubule
105
what are the functions of microtubule depolymerase?
* induce microtubule shrinkage or catastrophe
* dissociation of GTP bound tubulin from (+) end
106
what are clasp proteins?
proteins that stop disassembly and promote the restart of microtubule growth
107
the (-) ends of MT are anchored to the _ in mitosis
centrosome
108
dendrites contain microtubules that are oriented in which direction?
they are oriented in both directions with the (+) end pointing away from the body
109
in which direction are the microtubules in axons oriented?
uniformily oriented with the (+) end pointed towards the axon tip
110
which MAPs cap dendrites?
* MAP2
* Tau
111
what are kinesin and dyneins?
molecular motors that move along MT and are powered by ATP hydrolysis
112
most kinesins move towards the _ end which is also considered _ transport
(+); anterograde
113
most dyneins move towards the _ end which is also considered _ transport
(-); retrograde
114
what are kinetchore microtubules?
MT that attach to kinetechores on condensed chromosomes
115
what are interpolar microtubules?
MT that overlap at the cell center, helping stabilize the spindle
116
what are astral microtubules?
MT that extend from chromosomes to the cell periphery, aiding in spindle orientation
117
What causes chromosome movement in Anaphase A?
the kinesin motor proteins help depolarize the MT which shortens them
| depolarization causes degredation of MT
118
what are the two movements for spindle seperation in Anaphase B?
* (+) end directed motor proteins
* (-) end directed motor proteins
119
describe what happens during the movement of (+) end directed motor proteins?
* push the spindle poles apart to elongate the cell
* drive the sliding of interpolar microtubules
120
describe what happens during the movement of (-) end directed motor proteins?
* facilitate the pulling of astral microtubules
* are anchored to the cell cortex for traction
121
what is the function of intermediate filaments?
provide tensile strength to cells preventing them from being torn apart under tension
122
what is a desmosome?
molecular complexes of cell adhesion proteins and linking proteins that attach the cell surface adhesion proteins to intracellular keratin intermediate filaments
123
what is a hemidesmosome?
molecular complexes that link intermediate filaments to the extracellular matrix through plectin and integrins
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