Cell structure Flashcards
Where are membrane bound ribosomes found?
RER (rough endoplasmic reticulum)
What type of proteins do membrane bound ribosomes (on RER) produce?
Proteins that are mostly secreted from cell
- Protein hormones, digestive enzymes
What type of proteins do free ribosomes (cytosol) produce?
Proteins mostly used by cell
- Metbolism, structure
What are Nissl bodies?
RER in neurons
- Synthesize NTs
RERs are abundant in what type of cells?
Secretory cells
- Goblet cells (mucus)
- Plasma cells (antibodies)
- Pancreatic Beta cells (insulin)
What is the function of the golgi?
Modifies and transports proteins
- Proteins sorted/shipped by adding signal sequences
What is the functions of the smooth endoplasmic reticulum?
- Lipid/steroid synthesis
- Detoxification of drugs and toxins
Why is the smooth endoplasmic reticulum called ‘smooth’?
It is part of the endoplasmic reticulum w/o ribosomes
What does the sarcoplasmic reticulum contain?
Calcium
What is the smooth endoplastic reticulum known as in myocytes?
Sarcoplastic reticulum
What tissues have lots of SER?
- Hepatocytes (cholesterol synthesis, detoxification, CYP450)
- Adrenal glands
- Gonads
What face of the golgi do vesicles from the RER enter into?
Cis face (cis golgi network)
Where do vesicles leave the golgi from?
Trans face
What is an oligosaccharide?
Polymer (chain) of sugar molecules
How can the golgi modify oligosaccharides?
- Attach a Nitrogen (asparagine)
- Attach an Oxygen (serine/threonine)
What amino acids commonly have a sugar added in the golgi?
Serine/threonine (extra O molecule)
What molecule can be added to proteins destined for lysosomes?
Mannose-6-phosphate
- Triggers packaging in trans-golgi to lysososmes
What molecules have mannose-6-phosphate added to them to be taken to lysosomes?
N-linked oligosaccharides
What disease has an abnormal or disrupted processing in golgi where mannose-6-phosphate is not found on lysosomes?
I-cell disease
How is I-cell disease inherited?
AR
What are the clinical features of I-cell disease?
Onset in 1st year of life
- Growth failure
- Coarse facial features
- Hypotonia/ motor delay
What type of disease is I-cell (inclusion cell) disease?
Lysosomal stroage disease (mucolipidosis)
What enzyme is deficient in I-cell disease?
N-acetylglucosaminyl-1-phsophotransferase
What is the function of N-acetylglucosaminyl-1-phsophotransferase (deficient in I-cell disease)?
Adds phosphate to mannose
What enzymes are missing from the lysosomes yet can be found in the blood/urine in I-cell disease?
Hydrolases
What will the lysosomes contain in I-cell disease?
Inclusions of glycosaminoglycans and glycolipids
How are endosomes formed?
Endocytosis
- Invagination of plasma membrane to surround molecules
- Pinching of membrane to form an enclosed structure
What are the different types of endocytosis?
- Receptor mediated (cells take up specific molecules, ligands, that bind receptors)
- Pinocytosis (droplets)
- Phagocytosis
What type of enzymes are contained inside lysosomes?
Acid hydrolase enzymes
What is the pH roughly inside a lysosome?
~ 4.8
How many enzymes are thought to make up lysosomes? (acid hydrolase enzymes)
40+
What are perioxisomes?
Cellular organelles which contain oxidative enzymes (e.g. hydrogen peroxide)
What does catalse do?
Oxidizes substances with H2O2
- Detoxifies many sunstances in liver cells
- Can metabolize ethanol (alternative, minor pathway)
How can perioxisomes affect fatty acids?
Beta oxidation of fatty acids
- Preferentially oxidize longer fatty acids
Where other than the perioxisomes can beta oxidation occur?
Mitochondria (majority)
What is the function of proteosomes?
Destroy aberrant proteins (misshaped/misfolded)
- Req
What is the structure of proteasomes?
Barrel-shaped structure
- Protein complex which requires multiple protein subunits
What do proteasomes require to function?
ATP
What are proteins usually marked with before being destroyed by proteasomes?
Ubiquitin
What neurological disease is thought to have an association with reduced ubiquitin-proteasome activity?
Parkinson’s disease
- Toxic accumulation of proteins in neurons
What pulls free ribosomes to ER membrane?
Signal sequences
- Creates RER
Where are signal sequences found?
Proteins undergoing synthesis (translation)
- Short peptides
- Found on N-terminal of protein
What are signal sequences recognized by?
Signal recognition particle (SRPs)
- Found in cytosol
What is the function of Signal recognition particle (SRPs)?
Move proteins from cytosol to ER lumen
What does the SRP bind to and where?
SRP receptor on ER membrane
What are 3 well-characterized coats found on the surface of vesicles?
- Clathrin
- COPI
- COPII
What are clathrin-coated vesicles found?
- Transport between plasma membrane and golgi
- Also to/from endosomes in cytoplasm
- Extraceullar uptake (endocytosis)
What recpetors contain clathrin-coated pits?
- LDL-receptor
- GF receptor
What type of vesicle coats carry things from the golgi to ER (retrograde)?
COPI
What type of vesicle coats carry things from the ER to the golgi (anterograde)?
COPII
