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- Organelles: intracellular membrane-bounded compartments that house various cellular activities
- What does a SNARE stand for?: Snap Protein Receptor
- What are the 3 steps of SNARES mediating fusion between vesicles and target membranes?: 1. tethering 2.docking 3.fusion
- What does cis mean?: same 5. What is the difference free floating ribosomes vs. attached ER ribosomes?- : same ribosome just a signal tells the free ribosome to attach 6. COOH------NH2 Which end is the carboxyl and which is the amino end?: - COOH is the carboxyl end NH2 is the amino end
- Which end does protein synthesis occur?: amino end
- What does trans mean?: different
- 3 models of transport?: -cisternae maturation -gains abilities as moves -vesicular transport - moves already modified as long chain -stationary
- T/F: all endosomes are endosidic vesicles but not all endosidic vesicles are endosomes: T 11. What does endosidic vesicles depend on to be classified as endsomes?- : -contents
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-destination
- What does coated vesicles assist in?: -vesicle formation/budding -acts as tag to determine location
- T/F: all endosidic vesicles are endosomes but not all are endosomes are endosidic vesicles?: F
- What makes up the Endomembrane system?: -golgi -endoplasmic reticulum -vacuoles -lysosome -endosomes
- What is the movement of proteins and lipids between organelles known as?: trafficking
- shuttles materials (membrane lipids and membrane bound proteins and soluble materials) between various organelles: transpot vesicles
- Endoplasmic Reticulum: continuous network of flattened sacs, tubules, and associated vesicles that stretches through the cytoplasm -present in every cell -Smooth and Rough -Biosynthesis i. proteins destined into PM or into organelles ii.lipids (triacylglycerols, cholesterol) iii.synthesis of proteins destined for export from cell
- membrane bound sacs in ER: ER cisternae
- internal space enclosed by membranes of the ER: ER lumen
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via receptor proteins in the ER membrane shortly after translation initiation. ii. Newly synthesized proteins enter endomembrane system cotranslationally- en- tered through a pore complex in the ER membrane into the rER lumen as the polypeptide is synthesized by the ER-bound ribosomes
- Cotranslation: pore forming complex in the ER membrane--where newly syn- thesized proteins are inserted in the ER membrane then into the rER lumen as the polypeptide is synthesized by the ER-bound ribosomes
- ER-associatiated Degredation (ERAD): -proteins improperly modified, folded or assembled are exported from the ER for degradation by cytosolic proteosomes instead of moving to the Golgi apparatus -hypercholesterolemia is a disease due to failure of this process
- Smooth Endoplasmic Reticulum: -drug detoxification, carbohydrate metabo- lism, calcium storage, and steroid biosynthesis
- Drug Detoxification: -occurs in the smooth ER -involved enzyme-catalyzed hydroxylation i. addition of hydroxyl group makes the hydrophobic drug more soluble and easier to excrete from the body ii.cytochome P-
- Cytochrome P-450: family of heme proteins that are prevalent in the smooth ER of hepatocytes (liver) which detoxifies drugs
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-hydrolyzes hydrophobic drugs--making it more soluble and easier to excrete from the body
- Carbohydrate Metabolism: -smooth ER of hepatocytes -breakdown of glycogen i. presence of Glucose-6-Phosphatase
- Glucose-6-Phosphatase: -membrane bound enzyme that is unique to the ER -hydrolyses the phosphate group of G6P to form free glucose and inorganic phosphate i. -makes G6P for permeable to the membrane to leave the cell and enter the bloodstream -maintains levels of glucose in the body
- Calcium Storage: -smooth ER -Sacroplasmic Reticulum of muscle cells -calcium is released due to neurotransmitter signal cascade, leading to contraction in muscle fibers
- Sacroplasmic Reticulum: found in muscle cells -example of smoother ER -specializes in storage of calcium -release of calcium leads to muscle contraction
- Steroid Biosynthesis: smooth ER -cholesterol and steroid hormones (cortisol, testosterone, and estrogen) -found in adrenal gland, Leydig cells of testes, and Follicular cells of the ovary
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compartment of the Golgi stack is a stable structure, and that traffic between successive cisternae is mediated by shuttle vesicles that bud from one cisterna and fuse with another, in a cis-trans sequence in anterograde movement
- Cisternal Maturation Model: the cisternae are transient compartments that gradually change from CGN through medial cisternae to TGN cisternae in an anterogram movement
- Step by step, each cis cisterna is transformed first into an intermediate medial cisterna and then into a trans cisterna as it acquires additional enzymes.
- Anterograde Transport: movement of material from the ER through the golgi apparatus towards the plasma membrane
- Retrograde transport: -the flow of vesicles from the golgi cisternae back to- wards the ER
- Glycosylation: -addition of carbohydrates to amino acids residues of proteins, forming glycoproteins, usually beginning in the lumen of the ER and completed in the Golgi -N-linked Glycosylation -O-linked Glycosylation
- N-linked Glycosylation: involves the addition of a specific oligosaccharide unit to the nitrogen atom on the terminal amino group of certain asparagine residues
- O-linked Glycosylation: involves addition of an oligosaccharide to the oxygen atom on the hydroxyl group of certain serine or threonine
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residues
- Inititial steps of N-glycosylation take place : cytosolic surface of the ER membrane and later steps occur in the lumen
- Cis-Golgi Network: -attachment of N-acetylgalactosamine -phosphorylation of lysosomal proteins
- Medial Cisternae: -removal of mannose -attachment of N-acetylglucosamine -addition of galactose -addition of sialic acid
- Trans-Golgi Network: -attachment of sulfate to tyrosine
- Steps of N-linked Glycosylation of proteins in the ER: 1. Dolichol phosphate- in ER acts as a carrier for oligosaccharide units 2.Core Oligosaccharide Synthesis begins in cytosol: i. N-acetylglucosamine and monnose units are added to the dolichol phosphate 3.translocation of the oligosaccharide from the cytosol to the ER lumen: by flippase 4.Completion of the core oligosaccharide occurs in ER lumen -- more mannose and glucose units are added 5.oligosaccharyl transferase transfers complete core to aspargine residue of recip- ient protein 6.Final processing involves the removal of certain glucose and mannose units in the ER before transfer of the glycoprotein to the golgi
- ERp157: catalyzes disulfide bond formation
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4a. At the TGN, some vesicles form secretory vesicles, releasing contents at plasma membrane by exocytosis 4b. other vesicles bud from the TGN to form endosomes to make lysosomes.
- at the same time, proteins and other materials can be take into the cell by endocytosis, forming vesicles that fuse with early endosomes
- early endosomes containing materials for digestion mature to form late endo- somes and then lysosomes 3.retrograde traffic returns compartment-specific proteins to earlier compartments
- Retrieval Tags: Specific amino acid sequence by retrograde flow from CGN to ER -binds to specific transmembrane receptors facing the golgi apparatus lumen -short C-terminal amino acids (KDEL or KKXX -receptor undergoes a confirmational change and the receptor ligand complex is packaged into a transport vesicle for return to the ER
- Targeting of proteins to cellular compartments: requires" zip code" tag on protein or lipid -specific AA -specific carbohydrate pattern
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- Mannose-6-Phosphate: directs traffic from ER to lysosome -mannose residues on the carbohydrate side chain of lysosomal enzymes are phosphorylated -this tag distingusishes soluble lysosomal proteins from other glycoproteins and ensures their delivery to lysosomes
- Retention Tags: -preventing proteins from escaping tripeptide sequence ex: RXR -another: N-methyl D-Asparate (NMDA receptor)
- Co-translational Import: -entering the endomembrane -pore complex in the ER membrane into rER lumen as the polypeptide is synthesized by the ER-Bound ribosomes
- Golgi apparatus proteins may be sorted according to length (explain): golgi specific proteins that have one or more hydrophobic membrane spanning domains anchoring them to the golgi -lengnth of hydrophobic domains may determine into which cisternae of the golgi apparatus each membrane bound protein is incorporated as it moves through the organelle -increase in lengths of hydrophobic membrane-spanning domains going from CGN to TGN. -such proteins move from compartment to compartment until the thickness of the membrane exceeds the length of their membrane spanning domains--blocking further migration
- How do differences in the structure and arrangement of rough versus smooth ER reflect their different functions?: Rough ER
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Protein quality control is mediated by ER associated degradation (ERAD).
- Why is the rough ER attached to the nucleus?: The proximity of the rough ER to the cell nucleus gives the ER unique control over protein processing. The rough ER is able to rapidly send signals to the nucleus when problems in protein synthesis and folding occur and thereby influences the overall rate of protein translation.
- What are the functions of the smooth ER?: Mostly involved in processing or storing nonprotein molecules within the cell. -drug detoxification -carbohydrate metabolism -calcium storage -steroid biosynthesis
- What are the two types of ER?: Rough ER: is characterized by ribosomes on the cytosolic side of the membrane. -Transitional elements (TEs) are subdomains of the rough ER. And are important in the formation of transition vesicles. They shuttle proteins and lipids from ER to Golgi. Smooth ER: lacks ribosomes and are extensively found in cells producing steroid hormones.
- Why is it necessary for material flowing through the Golgi to move in both the anterograde and the retrograde directions?: A vesicle is necessary
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for material to flow through the Golgi
**72. What features of membrane lipids and proteins contribute to their proper trafficking and targeting in cells?:
- How would an inhibitor of membrane fusion differentially affect exocytosis versus endocytosis?:**
- What are the basic features of ALL cells?: -Plasma membrane -Nucleoid region (nucleus) -Semifluid substance called cytosol or cytoplasm -Chromosomes (carry genes) -Ribosomes (make proteins)
- Compare and Contrast the basic components of a prokaryotic and eukary- otic cell: FIX -Plasma membrane -Nucleoid region (nucleus) -Semifluid substance called cytosol or cytoplasm -Chromosomes (carry genes) -Ribosomes (make proteins)
- cytosol vs. cytoplasm: -cytosol is the fluid itself therefore different composition, different functions, less diversity -cytoplasm is everything within the plasma membrane except the nucleus therefore different composition, different functions, more diversity
- T/F: Eukaryotic Cells are highly Compartmentalized: T
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nuclear envelope +separates the contents of the nucleus from the cytoplasm and provides the structural framework of the nucleus, pores allow material transfer, connection to ER allows for protein regulation -endoplasmic reticulum (ER) +The RER modifies proteins and synthesizes phospholipids used in cell mem- branes. +The SER synthesizes carbohydrates, lipids, and steroid hormones; engages in the detoxification of medications and poisons; and stores calcium ions. -Golgi apparatus +Sorting, tagging, packaging, and distribution of lipids and proteins take place in the Golgi apparatus. -lysosomes +Lysosomes are created by the budding of the membranes of the RER and Golgi. Lysosomes digest macromolecules, recycle worn-out organelles, and destroy pathogens -vacuoles (vesicles) +transport materials around the cell
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-plasma membrane +forms the membrane of some vesicles, allows exo/endocytosis
- What is the function of the Golgi apparatus?: modifies lipids and proteins from the ER; sorts them and packages them into vesicles 83. Which of the following correctly matches an organelle with its function? central vacuole ... storage nucleus ... cellular respiration ribosome ... manufacture of lipids mitochondrion ... photosynthesis lysosome ... movement: central vacuole ... storage
- Cell size is limited by .: -Surface to volume ratios -The rates at which molecules can diffuse -The need to maintain adequate local concentration of substances required for necessary cellular functions 85. Which of the following is a major difference between prokaryotic cells and eukaryotic cells? Prokaryotes are generally larger than eukaryotes. Prokaryotes are not able to carry out aerobic respiration, relying instead on anaerobic metabolism. Prokaryotes have cells while eukaryotes do not. Eukaryotic cells have more intracellular organelles than prokaryotes.: Eukaryotic cells have more intracellu- lar organelles than prokaryotes.
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cy- toplasm
- The soluble portion of the cytoplasm, which includes molecules and small particles, such as ribosomes, but not the organelles covered with mem- branes.: cytosol
- The substance in which animal tissue cells are embedded, consisting of protein and polysaccharides.: extracellular matrix
- Found inside the nucleus and produces ribosomes: nucleolus
- An extensive membranous network in eukaryotic cells, continuous with the outer nuclear membrane and composed of ribosome-studded (rough) and ribosome-free (smooth) regions: Endoplasmic reticulum
- A system of membranes that modifies and packages proteins for export by the cell: golgi
- Small membrane-bound sac that functions in moving products into, out of, and within a cell.: vesicle
- Cell organelle that stores materials such as water, salts, proteins, and carbohydrates: Vacuole
- cell organelle filled with enzymes needed to break down certain materials in the cell: lysosome
- an organelle containing enzymes that transfer hydrogen atoms from various substrates to oxygen, producing and then degrading hydrogen per- oxide: peroxisome
- regulates protein traffic and performs metabolic functions in the cell: en- domembrane system
- What is the difference between exocytosis and endocytosis?:
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Both are methods of transport for materials across the plasma membrane. Exocytosis is secretory vesicles the release their contents outside the cell. Endocytosis is cells internalize external materials.
- What does the word lumen mean?: space
- cisternae: flattened stacked membrane folds
- COPI: COPI is a coatomer, a protein complex that coats vesicles transporting proteins from the cis end of the Golgi complex back to the rough endoplasmic reticu- lum (ER), where they were originally synthesized, and between Golgi compartments 106.............................................................................................. COP II: COPII is a coatomer, a type of vesicle coat protein that transports proteins from the rough endoplasmic reticulum to the Golgi apparatus....................................................................................This process is termed anterograde transport, in contrast to the retrograde transport associated with the COPI protein.
- What does COP stand for?: coat protein complex
- SNARE proteins: mediate fusion between vesicles + target membrane -how vesicle knows that it has reached its destination -not a protein coat
- What are the coat proteins of Clathrin-coated vesicles?: Clathrin
