Which of the following statements about protein kinases is NOT correct?
A) The a phosphate moiety of an ATP molecule is transferred by protein kinases to proteins.
B) Phosphorylation usually results in a functional change of the target protein.
C) There are approximately 500 protein kinases in the human system.
D) Serine and threonine are the most commonly phosphorylated amino acids in eukaryotes.
E) Tyrosine residues account for only 1% of phosphorylation sites in proteins.
Which of the following statements about GTP binding proteins is true?
A) GTP binding proteins require ATP as a source of energy for activation.
B) GTP binding proteins are typically active in the GDP-bound state.
C) GTP binding proteins are regulated by so called GEFs and GAPs.
D) GTP binding proteins act as long-term cellular storage for GTP molecules.
E) GTP binding proteins are primarily involved in the synthesis of GTP.
Which of the following best describes the role of insulin and glucagon in glucose homeostasis?
A) Glucagon lowers blood glucose levels by stimulating the pancreas to uptake glucose from the bloodstream.
B) Insulin and glucagon both stimulate the liver to release glucose into the blood, increasing blood sugar levels.
C) Glycogen regulates the release of insulin from the pancreas, directly influencing blood sugar levels.
D) Glucagon raises blood glucose levels by stimulating glycogen breakdown in the liver.
E) The pancreas releases glycogen into the blood to directly lower blood glucose levels when they are too high.
Which of the following statements is NOT true?
A) Activation of GPCRs can increase or decrease intracellular cAMP levels by using different a-subunits.
B) Certain pathogens disrupt GPCR signaling by covalently modifying their a-subunits.
C) A GPCR that decreases cAMP levels is involved in photopic vision.
D) Odors are mainly perceived by GPCRs.
E) GPCRs are seven transmembrane receptors.
Which statement about this picture is NOT true?
A) The molecule shown is called calmodulin.
B) It undergoes a conformational change when it binds Ca2+.
C) It regulates certain types of kinases by binding to their hinge region.
D) It is highly expressed in neuronal tissue.
E) It can also act as a kinase itself in a so-called phosphorylation cascade.
A) Phospholipase C-V cleaves inositol phospholipid 4,5-bisphosphate (PIP2) to produce inositol 1,4,5-trisphosphate (IP3) and diacylglycerol (DAG).
B) Phospholipase C-Y acts at the inner leaflet of the plasma membrane.
C) Phospholipase C-Y is activated downstream of receptor tyrosine kinases.
D) DAG triggers Ca2+ release from the endoplasmic reticulum.
E) Activation of phospholipase C-y indirectly leads to activation of protein kinase C.
What of the following statements is NOT correct?
A) Phosphoinositides are unique among phospholipids in that they can undergo reversible phosphorylation.
B) Phosphoinositide 3-kinase (PI 3-kinase) is recruited via its SH2 domain to activated RTKs, where it is activated.
C) Active PI 3-kinase phosphorylates lipids to generate PI 3,4,5-trisphosphate (PIP3).
D) PIP3 serves as a docking site for proteins containing a PH domain.
E) PIP3 is typically found at the trans-Golgi network.
What of the following statements is correct?
A) Cytokine receptors possess intrinsic kinase activity.
B) A typical feature of cytokine receptor signaling is the phosphorylation of serine residues for subsequent signal transduction.
C) Cytokine receptors and GPCRs execute a similar signal transduction program.
D) Cytokine receptors signal through a limited set of STAT (signal transduction and activation of transcription) proteins.
E) Insulin and glucagon signal through cytokine receptors.
Which of the following statements is correct?
A) Endocrine signaling typically occurs through direct contact between cells.
B) In paracrine signaling, the signaling molecules typically have long-range effects and can diffuse across the entire organism.
C) Contact-dependent signaling operates via secreted signaling molecules.
D) In autocrine signaling, cells respond to signaling molecules that they themselves secrete.
E) Synaptic signaling is considered slow due to the distance neurotransmitters must travel.
Which of the following assignments regarding the corresponding picture is correct?
A) 1= is activated by trans-phosphorylation, 2= binds to phosphoserine residues, 3= acts as a GAP.
B) 1= harbors kinase activity, 2= acts as an adapter protein, 3= acts as a protein kinase.
C) 1= functions as a dimer, 2= binds to phosphoserine residues, 3= acts as a GEF.
D) 1= is activated by trans-phosphorylation, 2= binds to phosphoserine residues, 3= acts as a GAP.
E) 1= harbors kinase activity, 2= acts as an adapter protein, 3= acts as a GEF.
Which of the following statements accurately describes the role of cytochrome c in intrinsic apoptosis?
A) Cytochrome c is released from the mitochondria upon direct activation by caspase-9.
B) After its release, cytochrome c degrades APAF1, preventing the formation of the apoptosome.
C) Cytochrome c release is prevented by the action of initiator proteins such as Bid and Bim.
D) Bax/Bak-induced MOMP leads to the release of cytochrome c, initiating the formation of the apoptosome with APAF1.
E) Cytochrome c directly activates caspase-3 and caspase-7.
What is the role of the Bcl2 family proteins in regulating intrinsic apoptosis?
A) Bcl2 family proteins, such as Bcl2 and BcIXL, directly cleave caspase-3 and caspase-7, initiating apoptosis.
B) Bcl2 family proteins promote the release of cytochrome c by activating Bax/Bak.
C) The Bcl2 family proteins function as guardians against apoptosis by inhibiting the activation of Bax/Bak.
D) Initiator proteins like Bid and Bim are a subset of the Bcl2 family that promote apoptosis by cleaving APAF1.
E) Bcl2 family proteins are part of the apoptosome complex and assist in the recruitment of caspase-9.
Which of the following is a characteristic feature of apoptosis?
A) By definition, apoptosis relies on the transcriptional up-regulation of pro-apoptotic transcripts.
B) Apoptosis is characterized by extensive inflammation due to the cells bursting.
C) Apoptotic caspases, once activated, induce inflammation and immune response by damaging neighboring cells.
D) Apoptosis is a form of programmed cell death that includes DNA fragmentation and membrane blebbing.
E) Apoptotic cells swell and eventually burst, releasing their contents into the surrounding tissue.
Which statement is correct in the context of the structural basis of Cdk activation?
A) In the inactive state, the active site of Cdk is blocked by ATP.
B) In the inactive state, the active site of Cdk is blocked by a phosphate group.
C) In the partially active state, the T-loop moves away due to cyclin binding of the complex.
D) In the partially active state, the T-loop moves into the active site due to cyclin binding of the complex.
E) In the fully active state, Cdk activating kinase (CAK) phosphorylates a site on the cyclin.
Which of the following statements regarding intermediate filaments (IFs) is NOT correct?
A) IFs are found as structural components of the nuclear lamina.
B) IFs give strength in particular to epithelial cells.
C) IFs are formed through structural assembly of proteins bearing "coiled-coil" structures.
D) IFs are formed through assembly of ATP binding proteins.
E) Keratins in hair and nail are further strengthened through disulfide bonds.
Which method can NOT be used to determine specific cell cycle stages of eukaryotic cells?
A) DNA staining followed by fluorescence-activated cell sorting (FACS).
B) Microscopic determination of cell shape in budding yeast.
C) Western blotting against markers of DNA damage.
D) Incorporation and microscopic visualization of artificial thymidine analogues.
E) Fluorescent ubiquitination-based cell-cycle indicator (FUCCI system).
Which of the following statements is correct for the process of semiconservative DNA replication?
A) The lagging strand shows continuous DNA synthesis.
B) The leading strand shows discontinuous DNA synthesis.
C) The leading strand shows continuous DNA synthesis.
D) The leading strand relies on Okazaki fragment synthesis.
E) The lagging strand but not the leading strand requires a sliding clamp.
Our cells sense/detect the presence of damaged DNA by an intracellular signal transduction pathway. Which of the following kinases is NOT part of this DNA damage response pathway?
A) Effector kinase Chk1
B) Sensor kinase Wee1
C) Sensor kinase ATR
D) Effector kinase Chk2
E) Sensor kinase ATM
Which of the following statements regarding microtubuli is NOT correct?
A) Microtubuli are composed of alpha and beta-tubulin building blocks.
B) Microtubuli are important tracks for vesicle and other cargo transport through Myosin I and II.
C) A variety of different motor proteins such as kinesins and dynein can travel along microtubuli.
D) Microtubuli are the major structural component of centrioles.
E) GTP hydrolysis to GDP in plus end caps causes stress that can lead to rapid depolymerization.
Mitogens stimulate cell division by a signal transduction pathway. Which CDK complex is shown in the picture (arrow)?
A) active G1/S-Cdk.
B) active S-Cdk.
C) active G1-Cdk.
D) active M-Cdk.
E) APC complex
Which mechanism does NOT contribute to the separation of sister chromatids during mitosis?
A) Cdc20-APC/C degrades Securin.
B) Separase cleaves Cohesin to release sister chromatids.
C) Cdc20 gene transcription increases in M-phase.
D) Securin binds and degrades a protease named Separase.
E) Activation of APC/C by M-Cdk.
Which cell contact enables the establishment of a polarized epithelium by preventing the mixing of membrane proteins between apical and lateral membrane domains?
A) Desmosomes.
B) Cadherin-containing adherens junctions.
C) Hemidesmosomes.
D) Gap junctions.
E) Tight junctions.
How does an adherens junction differ from a desmosome? Mark the correct answer.
A) An adherens junction links a cell to the neighboring cell and a desmosome links a cell to the extracellular matrix.
B) An adherens junction links cells by means of connexin proteins and a desmosome links cells by means of cadherin proteins.
C) While adherens junctions and desmosomes connect cells via cadherin proteins, only an adherens junction connects to the cytoskeleton.
D) While adherens junctions and desmosomes connect cells via cadherin proteins, adherens junctions connect to the cytoskeleton and desmosomes connect to intermediate filaments.
E) These two types of cell contacts differ only in the "band-like" versus "button-like" architecture in the cell membrane.
Cadherins form only weak interactions with their ligands, but can still mediate strong cell adhesion. How can this best be explained? Mark the correct answer.
A) Through the formation of homophilic interactions with integrins.
B) Cadherins bind the extracellular matrix protein fibronectin under mechanical stress.
C) They increase their avidity by clustering.
D) By preventing the degradation of the ligands.
E) By transcriptional upregulation of cadherin expression.
Which cell adhesion structure is marked with "D" in the picture?
A) Desmosome
B) Tight junction
C) Adherens junction
D) Hemidesmosome
E) Gap junction
Which cell adhesion molecules are necessary for leukocyte extravasation?
A) Selectins and cadherins
B) Selectins and integrins
C) Integrins and connexins
D) Immunoglobulins and connexins
E) Cadherins and claudins
Which of the following statements best describes the extracellular matrix?
A) It is physiologically inert and only serves to separate the cells of a tissue from each other.
B) It provides structural and biochemical support and regulates the physiological functions of a tissue.
C) It always contains equal amounts of collagen, fibrin, keratin and calcium.
D) It provides a waterproof barrier between cells.
E) It is recognized by cells that express cell adhesion molecules of the cadherin family.
Which enzymes do cancer cells use to digest through the extracellular matrix to allow migration and metastatic growth?
A) Matrix metalloproteases
B) Glycolipases
C) Extracellular lipases
D) Exonucleases
E) Kinases
Which of the following statements regarding actin filaments is correct?
A) Prokaryotes do not contain actin homologs.
B) Actin binds but does not hydrolyse ATP in the filament.
C) Actin filaments are predominantly assembled from ADP-actin in the cell.
D) Actin filaments typically have ATP-actin at the plus end and ADP-actin at the minus end.
E) Actin filaments typically have GTP-actin at the plus end and GDP-actin at the minus end.
Which statement describes actin filament "tread-milling" best?
A) The filament is static and no subunit exchange occurs.
B) The plus end oscillates through growth and shrinkage around an average length.
C) The minus end oscillates through growth and shrinkage around an average length.
D) The plus end shrinks at the same rate as the minus end grows.
E) The plus end grows at the same rate as the minus end shrinks.
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