ASU Cell BIO 353 Exam 3 SA Practice Questions and Answers

ASU Cell BIO 353 Exam 3 SA Practice Questions and Answers How do mitochondria get their lipids? Give a detailed answer. - Ans:-a. Lipids synthesized in ER b. transported to mitochondria c. switch of lipid takes place between ER and mitochondria & between mitochondrial membranes d. Membrane-tethering & lipid transfer proteins in mitochondria provides FIRST insight into mechanisms and transport processes e. Mitochondria DO NOT participate in vesicle trafficking, obtain lipids from ER through mitochondrial- associated ER membranes List the chaperones in the order that they are used in the long path of getting a protein into the mitochondrial matrix. (Note you should start in the cytoplasm.) - Ans:-a. cytoHSP70- in cytoplasm, chaperone that coats mRNA b. mitoHSP70- in between inner&outer mitochondrial membranes ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 2/16 c. mitoHSP60- mitochondrial matrix, enables whole protein to come in w/ COOH end, uses ATP for chaperone Describe evolution of endomembrane system -include why it is important. Contrast this with the evolution of the endosymbiotic origin of mitochondria and chloroplasts. - Ans:-a. endomembrane system is involved in a comprehensive communication system between cells. b. Components of endomembrane system are central to eukaryotic cell life c. Endosymbiosis. Analyze the signal sequence, and related characteristics that suggest that mitochondria and chloroplasts did not originate as part of the evolution of the endomembrane system - Ans:-a. Components of endomembrane system are central to eukaryotic cell life b. Endosymbiosis- improved fitness of the cell c. Mitochondria can make their own protein from circular DNA, now most has been outsourced to nucleus with genes transcribed in cytoplasm d. Signal sequence recruits HSP70 and coats growing protein Explain how cells take in water and general food at the periphery of the cells. - Ans:-a. Food- phagocytosis - plasma membrane is pushed out around food, creating two lamellipodia and fuse together to form vesicle around food ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 3/16 b. Water- pinocytosis - invagination forms around water, taken into cytoplasm through membrane channels to avoid damaging cell if vesicle explodes- membrane "Straw" used to "sip" water Explain how general food and food taken in by receptor mediated endocytosis merge with elements of the endomembrane system to digest and absorb those nutrients (including cholesterol). - Ans:-a. When a ligand binds to a receptor, receptor undergoes a conformational change. b. Exposes binding site for adaptor protein AP-2 c. Capping occurs when same type of receptors bind to their ligands all over surface of cell come together over small area; looks like baseball cap without the brim. d. Adapter protein recruits triskelon to form clathrin coat e. Receptor and ligand move using molecular motors f. Amino acid subunits pumped into cytoplasm & indigestible components removed by exocytosis Explain how membrane flow participates with membranes that are part of the endomembrane system, but also part of the plasma membrane. - Ans:-a. Vesicular transport moves newly synthesized lipids, transmembrane proteins, and luminal proteins within the endomembrane system. b. Forms spherical vesicle c. Vesicle is transported on microtubule pathway from ER to cis-face GA then move to cell periphery, transfer to actin filament, and move to PM ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 4/16 Distinguish between communication between cells and communication within cells - Ans:-a. 1. Autocrine communication- cell talks to self- endomembrane system synthesizes ligands that bund to receptors b. 2. Paracrine communication- ligand siffuses from site of exocytosis through isosmotic fluid c. Endocrine communication- exocytosed ligands enter circulatory system & carry to distant parts of organism, where ligand contacts receptors in other cells to cause change in cell behavior d. Juxtacrine communication- 2 or more cells are in physical contact & tug/push on neighboring cells e. For cell to receive signal receiving cell must have receptor or cell wont detect ligand f. Target cell= cell with receptor for specific ligand Distinguish between and categorize between Nuclear and Cytoplasmic signaling - Ans:-a. NUCLEAR- takes longer, maturation steps like splicing and adding adenosine-rich tail, must leave nucleus through nuclear pore, lag until mRNAs encounter signal recognition @ RER, but still have nothing- require thousands of copies of new protein to change cell b. CYTOPLASMIC- faster than nuclear, accompanied by amplification of signal, rapid responses happen in minutes-hours, kinase takes theta phosphate off of an ATP & covalently links to substrate to make phosphorylated product. Kinase can carry out 100 reactions in 1 second (100 fold amplification) ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 5/16 Note the differences in cytoplasmic and cell membrane receptors in all of the following: the ligands they use, time required to change cellular behavior after the ligand reaches the cell, and how long these changes in behavior persist - Ans:-a. TMP receptors have large ligands, many hydrophilic side groups b. Polar ligands cannot pass PM c. PM receptor transduces signal across PM, occurs when ligand binds to receptor, conformational change and turns cell on or off d. PM receptors made on membrane-bound polyribosomes as part of endomembrane system e. Cytoplasmic ligands diffuse into PM and enter cytoplasm NONPOLAR LIGAND f. Cytoplasmic receptors are synthesized off free polyribosomes NOT part of endomembrane system g. Cytoplasmic receptors bind to chaperone which hides nuclear localization signal of receptor h. When nonpolar ligand binds to cytoplasmic receptor, receptor undergoes a shape change- releases chaperone and exposes the nuclear localization signal, turns gene on or off Explain how subcellular localization of related components conserved ATP and increased the fitness of cells - Ans:-a. STAR geometry of membrane anchors refers to placement of specialized proteins b. Job specialization!!! c. Certain things happen @ PM while different things happen in cytoplasm, other things happen in ER ©GRACEAMELIA 2024/2025 ACADEMIC YEAR. ALL RIGHTS RESERVED FIRST PUBLISH OCTOBER 2024 Page 6/16 Explain the role and geography of monomeric vs heterotrimeric GTP binding proteins and how they initiate and terminate their function - Ans:-a. heterotrimeric GTP-binding protein i. composed of 3 different proteins 1. α, β, and γ subunits 2. The α and γ subunit are tethered to PM with membrane anchor 3. β subunit is tightly adhering to the γ subunit. ii. Movement is restricted due to anchoring/tethering b. monomeric GTP-binding proteins i. float freely in cell, not tethered to PM ii. names like Ras, Rab, and Ran iii. active when bound to GTP iv. after GTP is hydrolyzed to GDP, proteins are inactive Explain why it is a neat "evolutionary trick" to use calcium as a central part of cytoplasmic signaling and how this conserves energy and likely increased the fitness of cells - Ans:-a. Using calcium ions as a means of cytoplasmic signaling