L4. The cell 3 Flashcards
Describe LTPs in ERJS
- we can have LTP attached to both donor and acceptor membrane of the cell
- LTPs don’t diffuse between the membrane
- there is a flexible hinge enables LTP to move lipids by wining them between membranes
- highly efficient non-vesicular transport
Describe the mitochondria (functions)
- up to 10 um in length
- up to 1000/cell
- generates ATP by cellular respiration
- regulates cell death by apoptosis
- synthesizes phospholipids - cardiolipin
What are the mitochondrial compartments?
-outer membrane: porous allows passage of small molecules
intermembrane space: similar to cytosol
-inner membrane: folds called cristae; ATP Synthase complex;ETC complexes, ATP is generated through oxidative phosphorylation
-matrix: ~50% proteins, visocous contains cDNA, mitochondria rivosomes =, tRNA and mRNA
How many genes does mitochondrial cDNA have?
37 genes, others are imported from the nucleus
How are proteins encoded by the nucleus transported to the mitochondria?
- chaperone protein binds to the polypeptide and transports it to the mitochondria
- sequence in polypeptide directs to TOM complex
(TOM complex drives outer membrane insertion of the polypeptide) - small TIM complex binds the polypeptide and drives it towards the inner membrane
- large TIM complex inserts the polypeptide into the inner mitochondria membrane
- polypeptide is released into the membrane and folds into its structure
What is MELAS ( mitochondrial encephalopathy lactic acidosis and stroke like episodes)
- when you have cristae with no folds
- mutations in the mitochondria tRNA
- cannot produce energy
- weak posture
What are peroxisomes?
- beta oxidation
- self-replicating
- contains enzymes>40
- 1um
- proteins are obtained from
a. peroximal targeting signal sequence
b. vesicle fusion
What is Zellweger Syndrome?
defect in peroxisomal protein import
What are the functions for cytoskeletons?
- 3D protein filaments
- cell morphology
- intracellular motion
- whole cell migration
What are centrioles?
pairs of specialized micro-tubular structures within the centrosome, generate spindles
What makes thin filaments?
actin
What makes intermediate filaments?
nuclear lamins
What makes microtubules?
tubulin
Describe actin (filaments)
- F actin composed of 2 chains of G actin monomers
- Faster growing + end and a slower growing - end
- Capping proteins regulate length and speed of growth
- Different f actin bundles have different functions
- bundles are maintained by different actin binding /stabilizing proteins
- myosin motor proteins move cargo
What are focal adhesions
- where actin cytoskeleton comes into contact with ECM
- cells exerts tensile force on ECM
- needed for wound healing
- contractile bundles connect to ECM via integrins
- stabilized by Vanculin and Talin
Draw the focal adhesion complex
pg 67
Describe microtubules
- hollow tube consists of 13 parallel protofilaments of alpha beta tubulin heterdimer
- dynamic structure
- originates from centrosome from gamma tubulin ring complex
- plus end: addition of dimers
- minus end: shrinkage
What are the functions of microtubules
- chromosome segregation
- cillary and flagellar motion
- movement of organelles
What are the motor proteins for microtubules?
kinesins: + end directed motors
dyneins: - end directed motors
What is heterochromatin
Wound DNA, e- dense
What is euchromatin
unwound DNA
How large is a nuclear pore
9-11nm wide
What do the number of nuclear pores correlate to?
The amt of metabolic activity within the cell
What are the functions of the nuclear pore
- connected to each other by lamins
2. regulates the substances that enter and exit the nucleus
Where is RAN GEF located
Nucleus
Where is RAN GAP located
in the cytosol
Describe nuclear import
- Protein that is synthesized has the NLS (KKK_ which binds to importin heterodimer
- importin-protein complex carries the protein into the nucleus
- RAN-GTP complex binds to any of the importin subunits or proteins with the nuclear export signal (leucines) for export
Describe nuclear export
- RAN-GTP binds to the protein to be exported, leaves the nucleus through the nuclear pore
- RAN-GTP-protein complex dissociates due to RAN-GAP which causes the hydrolysis of GTP and dissociation of protein from RAN
- RAN-GDP diffuses back to the nucleus
- RAN-GEF exchanges the RAN-GDP complex to RAN-GTP complex.
Draw the nuclear import/export process (identify importins RAN GAP and RAN GEF
pg 73
Explain ribosome biogenesis
- transcription of rRNA
- import of proteins from the cytosol to the nucleus: immature ribosomes are made
- the immature ribosomes are released through nuclear export ( RAN-GTP)
- subunits combine on mRNA to become functional ribosomes
Name the sequence of the cell cycle
G1: cell prepares to copy genome
S: DNA duplication occurs
G2: mitosis preparation occurs (make tubulin)
M: mitosis
Describe what happens when there is UV damage with DNA
- DNA damage with UV p53 is released
- presence of p53 releases p21
- p21 blocks the release of CDK
What are cyclins?
cyclins and CDK drive cell through cell cycle
What are checkpoints in the cell cycel
ensure each stage is completed correctly by detecting damage/problems and arresting cell cycle
What is apoptosis?
programmed cell death
controls cell proliferation in development
responds to cellular damage by clearing damaged cells
2 pathways: extrinsic death receptor pathway
intrinsic mitochondrial receptor pathway
Compare apoptosis and nercosis
nercosis ( cell lysis). apoptosis has less inflammation
What is the difference between extrinsic death receptor pathway and intrinsic mitochondrial pathway
extrinsic death receptor pathway: responds to extracellular signals
intrinsic mitochondria pathway: responds to cellular signals /stress
Describe the extrinsic death receptor pathway
- death ligand binds to receptor
- activated receptor activates caspase 8
- caspase 8 activates other executioner caspases (3,6,7)
- executioner caspases induce :
- proteolysis of cytoskeleton
- cell blebbing
- digestion of chromosomes
- proteolysis of cytoskeleton
How is the extrinsic pathway related to the intrinsic pathway
Capsase 8 from the extrinsic death pathway stimulates the BID, which stimulates the BAX and BAK which induces mitochondria
How is the intrinsic mitochondrial pathway
- UV induces DNA damage
- DNA damage activates p53
- p53 activates BAX and BAK
- BAX and BAK induces cytochrome C releases from the mitochondria
- cytochrome C activates apoptosome (APAF1)
- apoptosome cleaves and activates caspase 9
- caspase 9 cleaves and activates executioner caspases
