L2. Cells Flashcards
What is cell theory?
- cell is the basic unit of life
- cells have the same chemical component
- cells can metabolize
- all cells come from pre-existing cells
- cells contain hereditary information
- total activity of the organism depends on the total activity of independent cells
What is the protoplasm?
All the contents of the cell
What is cytoplasm??
everything but what’s inside the nucleus
What is the cytosol?
Fluid suspension within the cytoplasm
What is the cytoskeleton?
tubules and filaments within the cell
What are organelles?
Membrane bound structures that are metabolically active
What is nucleoplasm?
Substance forming the contents of the nucleus, contains DNA, chromatin, nucleolus.
What is the major phospholipid in lipid bilayer?
PC: phosphatidylcholine (amphiphatic)
What are the functions of the lipid bilayer?
- acts as a barrier
- allows selective transport
- allows cell-cell communication/recognition
- transduces extracellular signals
What are the 4 membrane protein types?
- integral membrane protein
- peripheral membrane
- protein linked with a fatty acid tail
- linked to a specialized P-lipid
Name a p-lipid membrane protein
GPI ( glycophosphatidylinnositol)
Name a membrane protein linked with a fatty acid tail
palmitoylation
What are the 2 forms of transport?
- passive transport (no ATP, moves with a concentration gradient,voltage gated channel)
- active transport: needs energy, against a concentration gradient (eg. Na+/K+ pump)
What is the pathway for cell signalling?
signals->transducers->amplifiers->messengers
messengers effect sensors and effectors
Name 3 cell-signalling pathways
GPCR-cAMP
GPCR-InsP3
Kinase
Describe the GPCR-cAMP reaction
- signals bind to ligand, ligand undergoes conformational change
- causes alpha subunit of G-protein to exchange GDP for GTP. The alpha-subunit dissociates
- binds to adenyl cyclase, when activated cAMP is formed
- cAMP binds and activates the regulatory subunit of PKA
- PKA phosphorylates protein targets and alters their activity and expression
Describe the GPCR-InsP3 reaction
- GPCR (metabotropic glutamate receptor) binds to the ligad undergoes conformational change.
- transducer: G protein alpha subunit exchanges GDP for GTP dissociates and binds to PLC (phospholipase C) which creates the messengers: disacylglycerol and InsP3
- diacylglycerol converts to PKC and induces protein phosphorylation
- InsP3 regulates calcium signalling
Draw the cell signalling pathway for GPCR-InsP3 and GPCR-cAMP
L2. pg 16b
Describe the ER
- largest organelle in the cell, contains tubules,sheets and 3 way junctions
- RER: protein synthesis/folding/glycosylation and disulfide bond
- RER studded with ribosome
- SER:lipid synthesis and Ca2+ storage
- biosynthesis of other organelles
- function in quality control
- dynamic organelle: undergoes fusion, fission reactions
Describe protein synthesis on the RER
- protein is translated by ribosome in cytoplasm, signal sequence is translated
- SRP binds to signal sequence and brings it to the SRP receptor on the ER,
- ribosome continues to translate sequence
- once signal sequence is within the ER it is cleaved by signal peptidase
- completed protein is folded by chaperone proteins
What happens when proteins are misfolded in the RER
- build up of misfolded protein-ER stress
2. induces the release of UPR ( unfolded protein response)
What are the consequences of UPR activation?
- apoptosis
- transport of the misfolded protein out of the ER for degradation
- protein refolding: induces chaperone and lipid synthesis to help proteins fold
What causes cystic fibrosis
lack of cl- channels on the membrane, accumulated ER stress. depress UPR signal to have misfolded protein transported onto membrane
Describe the golgi structure?
- curved flattened cisternae
- multiple stacks making up ribbons
- numerous small vesicles
- polarized with a cis face receives vesicles from the ER and a trans face that releases mature vesicles
What are the activities of the golgi?
- protein and lipid glycosylation
- sphingolipid synthesis
- proteolysis of transcription factors
- protein sorting
- different activities occur in different cisternae
Describe the cisternae maturation model
- cisternae moves with cargo
- mature through stack
- golgi enzymes are recycled back to compartments
- problem: golgi enzymes are not seen in golgi vesicles
Describe the vesicular transport model
membrane stack is stationary
cargo moves between the cisternae
enzyme remains in compartments
there are cargo lager than the vesicles
