Cell Science Exam PDF

CELL SCIENCE EXAM Long answer tasks Actin filaments provide long tracks along which vesicles are transported by myosin motor proteins: R Yes, the statement is correct. Myosin motor proteins transport vesicles along actin filaments and provides intracellular t...

CELL SCIENCE EXAM Long answer tasks Actin filaments provide long tracks along which vesicles are transported by myosin motor proteins: R Yes, the statement is correct. Myosin motor proteins transport vesicles along actin filaments and provides intracellular transport and cellular organization. If you inject Bcl-2 within a cell it will not undergo apoptosis: R Yes, the statement is correct. B-cell-lymphoma 2 is an anti-apoptotic protein that plays a key role in regulating the intrinsic mitochondrial pathway of apoptosis. Okazaki fragments are removed by a nuclease that degrades RNA Incorrect, Okazaki fragments are short and newly synthesized DNA fragments formed on the lagging R strand during DNA replication. The removal of these fragments is carried out by ligases. DNA ligase is involved in joining DNA fragments together, whereas nucleases are responsible for degradation of RNA or DNA, respectively. Microtubule polymerization, depolymerization and motor proteins are required for DNA replication. R They are not directly involved in DNA replication, but rather in cell division and other cellular processes. Developing neurons compete for limited amount of survival factors otherwise they are eliminated by necroptosis. R Partially correct, this concept is related to neuronal development and survival. Neurons will during development go through a period of competition for limited resorces, and those who fail to do so may undergo programmed cell death, also known as apoptosis – NOT necroptosis. Calmodulin regulates intracellular Ca2+ concentration R Yes, the statement is correct. Calmodulin is a calcium-bonding protein that plays a crucial role in regulating intracellular calcium levels. Nucleosome core particles are 30nm in diameter, and when lined up, form 30nm filaments. R False, filaments are going to wrap around the DNA molecules and therefore should be larger. The wrapping condenses the DNA and the beads itself add together to form the filament.  Glycolipids move between different membrane enclosed compartments during their synthesis but remain restricted to one side of lipid bilayer. False, flippase floppase activity change glycoproteins from one leaflet to another. They can more but the enclosed comp but restricted to extracellular ka List minimum 5 different variant functions of peroxisome: 1) Catalase detoxifies H2O2 R 2) 3) Catabolise very long chain of fatty acids Catabolise amino acids 4) Catabolise branched fatty acids 5) Reduces other reactive oxygen species What do you know about the origin (evolution) of the peroxisome?  Endosymbiotic theory -> evolved through engulfment of free-living bacteria by host cell.  An eukaryotic cell engulfed a bacterium capable of performing oxidative reactions.  Ended with a symbiotic relationship and the peroxisome evolved and specialized into a organelle with various metabolic processes. comes from the endomembrane system of the eukaryotic all togheter with ER “Both the GTP-bound a subunit and nucleotide-free Beta-y-complex – but not GDP bound, fully assembled G protein – can activate other molecules downstream om GPCRS” Incorrect. GTP bound alpha units acts directly on other molecules such as adenylyl cyclase. R Nucleotide free beta gamma complex does not act on other molecules. However, you can say that GDP bound G proteins are in its inactive form so they do not activate other molecules downstream of GPCR. “Transporters allows solutes to cross a membrane at much faster rate than do channels” Both transporters and channels facilitate the movement of solutes across membranes. Channels R generally allow for faster transport due to their passive nature and direct passage of solutes through a pore. Transporters often operate slower as those of active transport are in need of ATP. “A symport would function as an antiport if its orientation in the membrane were reversed” R Incorrect, they are both a distinct type of membrane transport proteins. Symporters transport two different substances in the same direction, while antiporters move substances in opposite directions. Reversing it would probably disrupt the normal transport function. What happens in rER? R  Protein synthesis on ribosomes   Polypeptide folding in rER lumen  N-glycosylation and the modification of oligosaccharide chain  Quality control  Transport of all other proteins to Golgi by vesicles Function of sER:  Synthesis of membrane lipids R   Storage of calcium ions Synthesis of steroids  Detoxification in liver -> liver performs detoxification, so they are rich in rER  Glucose metabolism Criteria of terrestrial life 1) Stable internal environment 2) Organized structure 3) Metabolism R 4) 5) Growth/development Ability to reproduce 6) Ability to adapt to environment 7) Responsiveness to environmental stimuli RNA world theory 1) RNA is a substance of inheritance 2) It catalyses its own replication R 3) 4) Its synthesis is simpler than DNA Short RNA-like molecules could be formed spontaneously 5) Those RNA molecules could become dominant which replicated faster with less errors 6) Mutations could result in many successful molecules The nuclear lamina is connected to the outer nuclear membrane Yes, this statement is correct. The nuclear envelope consists of the inner and outer nuclear membranes, and they are connected at NPC (nuclear pore complexes) that regulate the exchange of molecules between the nucleus and cytoplasm. Lamina is associated with the inner nuclear membrane List three examples of why stem cells research is so important:  Regenerative medicine: stem cells have the unique ability to differentiate into various cell R types. Researchers explore the potential of using stem cells to repair and replace damaged tissues and organs. These holds promise for treating several conditions where damaged tissue can be regenerated or replaced with healthy cells.   Disease modelling and drug development: Induced pluripotent stem cells (iPSC) can be reprogrammed to mimic different cell types affected by diseases. Researchers can create disease models in the lab, providing insight into disease mechanism and progression. Stem cells also serve as a platform for drug testing and development without using animal or human testing subjects.  Understanding development and differentiation: stem cells contribute to our understanding of development and differentiation processes in the human body. Research give insight in normal development and the molecular organism that govern cell fate decisions. Stem cells, what they are and function Undifferentiated cells that have the unique ability to differentiate into specialized cell types and self- renew. They play a crucial role in development, tissue homeostasis and repair.  Embryonic stem cells: derived from embryos at blastocyst stage, pluripotent and has the R  potential to become any cell type in the body. Adult stem cells: Found in various tissue, can differentiate into a limited range of cell types within a specific tissue or organ. Responsible for tissue repair and regeneration. They are of significant interest in medical research and potential therapeutic applications, including regenerative medicine. The use of Embryonic stem cells raises ethical considerations, as their derivation typically involves the destruction of embryos. IPSCs are a type of stem cell generated by reprograming adult cells to have embryonic stem-cell properties, which provides an alternative without the ethical concerns. What is essential for cell culturing?  Physical parameters: temperature, O2/CO2, humidity, osmolarity, pH R   Aseptic conditions: cell density, co-culture, feeder cell layer Chemical parameters: defined medium, serum (growth factors + hormones) What is calmodulin? R Calmodulin is a Ca2+ binding protein that modifies many target proteins based on the Ca2+ concentration. Give at least five cell morphological changes induced by the pro-apoptotic factors 1) Cell shrinkage 2) Nuclear condensation and fragmentation R 3) Membrane blebbing 4) Loss of plasma membrane integrity  5) Cellular fragmentation into apoptotic bodies. Match the pairs Chemotaxis: the vectorial locomotion is directed by a concentration gradient of a molecule in the fluid phase. Necro taxis: this is a vectorial cellular movement induced by the injured cells releasing necrotic factors. Chemokinesis: the random movement pattern of a cell is changed by the concentration gradient of a molecule in fluid phase. Haptotaxis: the ameboid like migration when the cell release proteolytic enzymes to cleave the ECM components. Mesenchymal Migration: the vectorial movement of a cell is induced by the concentration gradient of a surface bound molecule. KINASES 1) Phosphorylates amino acids 2) Enzymes that result in conformational change in target proteins that alter activity, localization and interactions with other molecules. 3) CAMP, Ca2+, DAG 4) Important in cellular processes: cell cycle regulation + signal transduction “GTP is hydrolysed by tubulin to cause bending of the flagella” R Not correct, the hydrolysis of ATP not GTP, by dynein is a key energy source for the movement of microtubules and consequently the bending of flagella. “The drug Taxol, extracted from the bark of Yew Trees, has the opposite effect on the drug Colchicine, an alkaloid form of autumn crocus” R Correct, colchicine inhibits microtubule assembly while Taxol promotes and stabilizes microtubule assembly. “Does GTP hydrolysation cause de-polymerization of tubulin?” R  Correct, it is a key factor in regulation of microtubule dynamics and is associated with depolymerization of tubulin. “Microtubule polymerization, depolymerization and motor proteins are required for DNA replication” R Partially correct, they are more related to cell division and not required for DNA replication itself, as that involves specific enzymes. Characteristics of Mitochondria  Inner membrane that folds -> larger surface area  Has its own DNA R  ATP is synthesized by them  Has their own ribosomes  Prokaryotic origin CYTOSKELETON  Provides structure, is dynamic  Aids in movement and intracellular transport Microtubules  25nm, made up by tubulin with alpha tubulin and beta tubulin to form dimers (13 of this form a microtubule)  Helps with structure, organize the position of organelles  Direct intracellular transport Intermediate filaments  10nm, primary filament in cytoskeleton  Rope like fibres found along the inner surface of nuclear envelope  Builds a cable network connecting cells of epithelia sheets  Provides mechanical strength and structural integrity Micro/Actin Filaments  7nm, made of actin protein, long strands of globular proteins twisting like a double helix  Concentrated beneath plasma membrane  Controls outer shape of cell  Help in contraction of muscle cells What is common in microfilaments, microtubules and intermediate filaments R They are all dynamic structures and act as both muscle and skeleton for movement and stability. Intermediate filaments are linkers between microtubular and microfilament systems.