MICB 302 EXAM QUESTIONS WELL ANSWERED LATEST UPDATE 2026

MICB 302 EXAM QUESTIONS WELL ANSWERED LATEST UPDATE 2026 How does location of hematopoiesis change throughout development? - Answers Early embryo - yolk sac Fetus - fetal liver and spleen 4-5 months - shift to bone marrow What does the erythroid lineage give rise to? - Answers Blood cells and megakaryocytes What do megakaryocytes do? - Answers Produces platelets and resides permanently in the bone marrow What cells are part of the myeloid lineage? - Answers Granulocytes and monocytes/macrophages/dendritic cells and mast cells What is a neutrophil? - Answers A short lived immune system cell that has phagocytic activity What are eosinophils? - Answers Defends against parasites; contain basic substances What are basophils? - Answers They regulate the immune responses to parasites and contain acidic substances What is a monocyte? - Answers Precursor cell to macrophages that circulate the blood What is a macrophage? - Answers A mature monocyte that can phagocytose several bacteria and act as an APC Whata are immature dendritic cells? - Answers They are highly phagocytic cells that mature after ingesting a pathogen What makes dendritic cells such great APCs? - Answers They express a lot of MHC proteins and co-stimulatory molecules What are mast cells? - Answers They are cells that are involved in the innate immune responses during microbial infection and release chemicals to attrack neutrophils and monocytes What does the lymphoid lineage give rise to? - Answers Large granular lymphocytes and small lymphocytes What are natural killer cells? - Answers They target virally infected cells and secrete cytokines to impede viral replicaiton What are Cytotoxic T cells ? - Answers They kill virally infected cells and some types of cancer cells What is the role of T helper cells? - Answers Provide cytokine and co-stimulatory signals to CTLS, macrophages, and stimulate B cells What are T-regulatory cells? - Answers They inhibit T cell responses and are involved in controlling immune reactions and prevent autoimmunity What are B cells? - Answers They synthesize and secrete antibodies What are plasma cells? - Answers They are differentiated B cells that synthesize and secrete antibodies What are the key properties of hematopoeitic stem cells? - Answers Their ability of self-renewal, ability to give rise to amture cell types that have distinct morphology and specialized functions Two models that explain how HSCs can divide in to two non-identical daughter cells? - Answers Asymmetric cell division and environmental asymmetry Explain asymmetric cell division - Answers During cell division, specific cell-fate determinants are not distributed equally before the onset of division which allows one daughter cell to receive these determinants and initiate differentiation. During mitosis, cleavage plane is oriented unevenly Explain environmental asymmetry - Answers HSC undergoes symmetrical cell division but one daughter cells receives signals from the microenvironment that initiates its differentiation What in the bone marrow is important for signaling in hematopoiesis? - Answers Osteoblasts and other stromal cells provide important contact-dependent interactions through cell adhesion molecules and their ligands, as well as cytokines and chemokines to control proliferation and differentiation What is a key protein on a stem cell that determines its fate? - Answers The kit protein, when bound to a ligand seems to prevent cell from committing to differentiation Why is signaling important for the survival of the cell? - Answers The cell must receive a survival signal or else its activate apoptosis What is the interface of the bone and bone marrow called? - Answers The endosteum What is present at the endosteum? - Answers Bone-lining cells such as osteoblasts, and osteoclasts Why are arteries important in the bone marrow for hematopoiesis? - Answers It brings cytokines to act on the progenitors Where can HSCs be found in the bone marrow? - Answers in the endosteum and in contact witht he sinusoidal endothelium and bone-distance sites What cells product various cytokines to support HSCs? - Answers Stromal cells such as mesenchymal stem cells, CAR cells, and adipocytes as well as osteoblasts and SNO cells which are located near the endosteum An important chemokine for maintenance of HSCs? - Answers CXCL12, SCF, and thrombopoietin What is the role of CXCL12? - Answers Plays an important role in maintaining the quiescent HSC pool What is the role of SCF? - Answers Plays a role in HSC self-renewal, and possibly formation of HSC niche What does thrombopoietin do? - Answers Important in HSC renewal What are CAR cells? - Answers CXCL12-abundant reticular cells Why are CAR cells important? - Answers In the vascular region, they may be important in the retention of hematopoietic progenitors in the niche. In the endosteal regions, they seem to be important in maintaining HSC quiescence If HSCs are rare cells, how are we keeping up with our supply of red/white cells? - Answers CLPs and CMPs are progenitor cells that can continue to expand temporarily while differentiating What are the three sources of HSCs we can isolate from? - Answers The bone marrow, peripheral blood and umbilical cord blood About how many cells extracted from the bone marrow contain transplatable HSC? - Answers About 1 in 10^6, others include bone cells, stromal cells, and white and red cells How does extracting HSCs from the blood work? - Answers First we use G-CSF to cause cells in the myeloid lineage to secrete enzymes that breakdown cell adhesion molecules between HSC and stromal cells which result in HSC emigration. Then we use apheresis to isolate leukocytes and use CD34 antibodies to select for HSCs What is the purpose of erythropoietin? - Answers To stimulate the production of more erythrocytes What is the colony forming unit assay used for and how is it done? - Answers - Used to enumerate multi-potential or lineage-committed hematopoietic progenitor cells from bone marrow - Cells placed on media with various growth factors then observe the colonies differ in size, morphology, and cell composition What are colony-stimulated factors? - Answers Glycoproteins that bind to specific cell-surface receptors to stimulate colony growth What has CSF demonstrated in vitro? - Answers Control rate of cell division, # of time a progenitor cell undergoes replication before differentiating, act early to influence commitment, act late to facilitate differentiation What are two markers in leukocytes that can be used to identify its lineage and subsets? - Answers Cluster of Differentiation (CD) and Lineage markers (Lin) What kind of markers do HSCs are known to have? - Answers HSCs are known to be Lin- and CD34+ as well as CD38 How can we use markers to isolate HSCs? - Answers We can use Lin antibodies to negatively select for HSCs How does FACS work? - Answers Sample is incubated to an antibody attached with a fluorochrome. FAC machines then inspect each cell individually and divide them depending on what fluorochrome is detected. Can detect multiple antibodies. For what processes are signaling pathways important in the immune system? - Answers Hematopoiesis, recognition of a pathogen, activation of adaptive immune responses by B/T cells, and communication between different cell types Three types of signaling that are important in the immune system - Answers 1 .Autocrine - responding to self-produced molecules. 2. Juxtacrine - responding by cell contact 3. Paracrine - responding to molecules produced from neighbouring cells What is an example of autocrine signalling? - Answers When T-helper cells produce IL2 cytokines that stimulate itself What is an example of juxtacrine signaling? - Answers Stromal cells and HSC in the bone marrow Example of paracrine signalling? - Answers T helper cells activating B cells What are the properties of a good signaling/detection system? - Answers 1. High sensitivity and amplification of the signal 2. Reversibility, Proteins are used as switches, often phosphoproteins and GTP-binding proteins, also addition of ubiquitin for degradation 4 main classes of intracellular signlaing proteins? - Answers Protein kinases, G proteins, Scaffold/adaptor proteins, and Ubiquitin How do protein kinases work? - Answers They act as molecular switches by catalyzing additions of a phosphate group from ATP to protein to either activate or disable it. The signal is then transmitted downstream to various other pathways What amino acids can be phosporylated? - Answers Tyrosine, Serine, and Threonine. Mainly tyrosine kinases How do receptor protein kinases work? - Answers When the ligand binds, it causes dimerization of individual receptors resulting in the cytoplasmic kinase domain to become active and phosphorylate each other How do non-receptor protein kinases work? - Answers The receptors are associated with intracellular tyrosine kinases when the ligand binds which activates it What removes phosphate groups? and why are they important? - Answers Phosphatases, they can regulate signlaing proteins by resetting them How do G proteins work? - Answers G proteins are proteins that contain a GDP group. A GTP can replace the GDP which can activate or deactivate the protein What are the two kinds of G proteins? - Answers Heterotrimeric receptor-associated G proteins and small G proteins What does the heterotrimeric receptor-associated G proteins contain? - Answers a, B, and gamma subunits What are small G proteins? - Answers Proteins that act downstream of many transmembrane signaling events such as Ras and Raf How do GPCRs work? - Answers 1. In resting cells, the G protein is not associated with a receptor and GDP is bound to the a unit 2. When a ligand binds to a receptor, it causes a conformational change that allows it to bind to the G protein 3. GDP is then displaced and GTP is allowed to bind to the a subunit which causes activation 4. The a subunit then dissociates from the BY complex, and each can activate other proteins 5. Signal is ended with GTP is hydrolyzed and the subunits reorganize What is the function of guanine exchange factors (GEFs) and GTPase-activating proteins (GAPs)? - Answers - GEFs convert GTPase into an active form by releasing GDP and binding the more abundant GTP. - GAPS accelerate the conversion of GTP to GDP to end the signal What are scaffold and adaptor proteins? - Answers They are proteins used to join other proteins together in a signal cascade via interaction domains. What is the difference between scaffold and adaptor proteins? - Answers Adaptor proteins are just smaller proteins that bring two different proteins together What does the addition of ubiquitin affect? - Answers It affects the location, activity, structure, and ability to interact with other proteins How does ubiquination work? - Answers Ub is covalently attached to a lys residue on target protein which is faciliated by E1, E2, and E3 proteins. There are a variety of polyUb chains available because a ubiquitin can bind with a K residue or an M1 residue of another Ub What is the function of ubiquitin? - Answers 1. Proteosome when linked to K48 2. K63/M1 linked are involved in signalling 3. Some Ub chains function as adaptors to link components also What is an example of a protein interaction domain? - Answers pY residues are binding sites for a number of protein-interaction domains (SH2). SH2 domains bind to a specific sequence recognizing pY and the 4th AA from there What is a phospholipid that is important in signaling pathways? - Answers Phosphatidylinositol (PIs). It is concentrated in the cytosolic monoclayer of the plasma membrane How is phosphatidylinositol used in signaling? - Answers The inositol ring of PI is phosphorylated by various kinases that turn it into PIP2 why act as a binding site for other proteins What is PIP3 and its function? - Answers PIP3 is formed from PIP2 via PI3-Kinase. It serves as a docking site for signaling proteins with PH domains How is PI3-K activated? - Answers By GPCRs and it is recruited via the SH2 domain and binds to pY in the tyrosine kinase receptor What is the purpose of PIP2? - Answers To be a precursor to PIP3 as well as be cleaved by PLC-y to produce two secondary messengers What is the purpose of secondary messengers? - Answers To activate the next stage of the pathway as well as amplify its signal What cleaves PIP2 and what is it cleaved into? - Answers PLC-y and it is cleaved into IP3 and DAG which act as secondary messengers What does IP3 do? - Answers IP3 diffuses into the IR and binds the IP3 receptor which causes Ca2+ to flow into the cytosol which can then bind to other proteins and activate them What does DAG do? - Answers DAG is a lipid-soluble molecule that diffuses into the plane of the membrane and recruits other proteins to the membrane and activates them such as PKC What does PKC do? - Answers PKC phosphorylates various protesin at their S and T residue What are the two ways the initial signal can be amplified? - Answers Kinase cascade and secondary messengers How does the kinase cascade work? - Answers Activated Raf activates several Mek proteins which then more Erk proteins that can enter the nucleus and act as a transcription factor How are signals terminated? - Answers 1. Ligand binding can be reversed or degraded by enzymes 2. Phosphatases can remove P groups from activated proteins 3. G proteins have intrinsic GTPase activity and GAPs can increase the activity 4. De-Ub enzymes can remove Ub 5. Ca2+ is taken back into the ER How does activation of the same receptor cause two different outcomes? - Answers Depends on which combination of signals or presence of signals from other pathways to tell what the response is Explain how engagement of a receptor can result in two different outcomes in B cells? - Answers When in the bone marrow, if the BCR is engaged it is fated to apoptosis but when it is engaged in the spleen/lymph node it is encouraged to proliferate and differentiate Receptors in the innate immune response use what to recognize pathogens? - Answers Pathogen Associated Molecular Patterns (PAMPs) What kind of receptors recognize PAMPs? - Answers Pattern Recognition Receptors (PRRs) The 4 groups of PRRs? - Answers 1. Membrane bound phagocytic receptors 2. Membrane bound signaling receptors 3. Cytoplasmic signaling receptors 4. Soluble proteins in the serum What are 4 examples of membrane bound phagocytic receptors? - Answers 1. Lectins - which recognize carbohydrates (mannose receptor) 2. Scavenger Receptors - recognize negatively charged microbial ligands 3. MARCO recognizes bacteria 4. Complement receptors CR4 and CR3 recognize iC3b What is an example of a membrane-bound signaling receptor? - Answers Toll-like receptors (TLRs) Explain the structure of TLRs - Answers TLRs have a leucine rich extracellular domain, and a singla pass transmembrane with an intracellular TIR domain for signaling Explain the mechanism of TLRs - Answers 1. TLRs are activated when a binding of a ligand induces formation of a dimer 2. Start a signaling pathway to activate a variety of transcription factors such as NF-kB, as well as possibly inflammatory cytokines, chemotactic factors, and such What are DAMPs? - Answers Damage associated molecular patterns. Can activate TLRs and DAMPs can mount an immune response What are the three examples of cytoplasmic signaling receptors? - Answers 1. NOD-like receptors (NLRs) 2. RIG-I-like receptors 3. cGAS-STING Structure and function of NLRs? - Answers 1. NLRs contain a nucleotide-binding oligomerization domain (NOD), CARD domain and a LRR 2 They detect bacterial infection What does NOD1 and NOD2 sense? - Answers They both sense proteins on the peptidoglycan Mechanism of NLRs - Answers When NODs are activated, they dimerize and phosphorylate TAK1 and IKK to activate transcription factor IkB that induces inflammatory responses What do RIG-I-like receptors (RLRs) do? - Answers They detect viral RNAs in the cytoplasm How do RLRs recognize viral RNA? - Answers They have an RHA helicase like domain with two CARD domains that interact with MAVS Mechanism of RLRs? - Answers RLRs recognizes uncapped RNA and results in a signaling cascade that results in the production of type I interferons by activating IRF3 and NFkB What does cGAS-sting pathway do? - Answers They detect dsDNA in the cytoplasm from viral DNA and possibly bacterial DNA