Lecture Exam 4 Flashcards
What are the four phases of the cell cycle and what are the main events of each?
-G1 Phase: Is the environment favorable to enter the S phase?
-S Phase: DNA replication
-G2 Phase: Is all DNA replicated and any damage repaired? Can we enter mitosis?
-M Phase: Mitosis (nuclear division) and Cytokinesis (cytoplasmic division)
What is a cyclin and what is cyclin-dependent kinase and how do these complexes regulate cell cycle progression?
-Cyclin: regulatory protein whose concentration rises and falls at specific times during the eukaryotic cell cycle; help to control progression from one stage of the cell cycle to another by binding to a Cdk
-Cyclin-Dependent Kinase: what the cyclin binds to to control progression of the cell cycle to another
What roles do the S-cyclin and M-cyclin play? (what phases do they promote?)
-S-Cyclin: regulatory protein that helps to launch the S phase of the cell cycle
-M-Cyclin: regulatory protein that binds to mitotic Cdk to form M-Cdk, triggers the M phase of the cell cycle
How is ubiquitination used to regulate cyclins?
-Ubiquitination adds a ubiquitin chain to the cyclin which helps the cyclin be destroyed in the proteasome
How is phosphorylation used to regulate CDK activity?
-The CDK is phosphorylated by 2 inhibitory phosphates to activate it
How are inactivator proteins like p27 used to regulate cyclin-Cdk complexes?
-p27 binds to an activated cyclin-Cdk complex. Its attachment prevents the Cdk from phosphorylating target proteins required for progress through G1 into S phase
What does it mean for a replication origin to be “licensed” and when does this occur in the cell cycle? When does origin firing take place?
-“Licensing” of the replication origin means that all chromosomal DNA has been replicated precisely before cell division occurs; this occurs during G1 phase
-Origin Firing occurs during S phase after the replication origin has been formed
Define apical and basal surfaces of an epithelial tissue.
-Apical Surface: free and exposed to the air or to a bodily fluid
-Basal Surface: attached to a sheet of connective tissue called the basal lamina
Describe types of mutations that can lead to the loss of a tumor suppressor gene. Name an example of a tumor suppressor gene.
-Recessive Mutation (loss of function): mutation inactivates one copy of tumor suppressor gene; second mutation inactivates the second gene copy; results in complete loss of tumor suppressor gene
-Example: p53
Describe types of mutations that could activate an oncogene. Name an example of a proto-oncogene.
-Dominant Mutation (gain of function): mutation in one copy of proto-oncogene creates a hyperactive oncogene
-mutation in coding sequence→hyperactive mutant protein made in normal amounts
-gene amplification→normal protein overproduced
-Chromosome rearrangement (one of two)
-nearby regulatory DNA sequence causes normal protein to overproduce
-fusion with actively transcribed gene produces hyperactive fusion protein
-Something is happening to turn these on that increases activity
-point mutation, duplication/amplification, truncation (regulatory part is missing)
-Example: EGFR
Stem Cell
relatively undifferentiated, self-renewing cell that produces daughter cells that can either differentiate into more specialized cell types or can retain the developmental potential of the parent cell
Totipotent
can form all the cell types in a body (even embryonic)
Pluripotent
capable of giving rise to any type of cell or tissue
Multipotent
can develop into more than one cell type, but are more limited than pluripotent
In general, do cancers form from a single mutation or multiple mutations? Why?
-Cancers generally form multiple mutations. The body is easily able to fix a single mutation, but it is harder to fix multiple mutations
What are some cancer treatment options?
-Surgery: removal of tumor (best case/ideal)
-Radiation: induces DNA damage and apoptosis
-can be alone or in combination with chemo
-Antineoplastic Chemo:
-Primary Induction: if surgery is not an option
-Neoadjuvant Chemo: surgery is done/added benefit
-Adjuvant Chemo: make sure nothing comes back
Why are cancer drugs combined together?
-Provides a maximal cell kill within range of toxicity
-Broader range of the interaction between drugs and tumor
-May prevent or reduce the rate of drug resistance development
-Avoiding hypersensitivity reactions by treating at lower doses
What are some common side effects of chemo?
-Constantly proliferating cells are the most affected
-Depression of bone marrow and blood cell levels
-Hair loss
-Cells of the digestive tract (nausea, vomiting, diarrhea)
-Neurotoxicity (headaches, nausea, vomiting, tremors)
-Liver and kidney are negatively affected during metabolism/excretion
Why is it critical to detect a tumor when it is smaller?
-Bigger tumors require more treatment
-The larger the tumor, the fewer healthy cells that are growing and dividing
-As tumor size increases, growth factor decrease (growing and dividing)
What are examples of typical targets of classic cancer drugs?
-Nucleotide Production
-Replication
-Transcription
-Cell Production
-Enzymes
(Hallmarks of Cancer Paper)
What is the difference between schedule-dependent and dose-dependent chemotherapy?
-Schedule-Dependent: effectiveness is cell-cycle phase-specific
-Dose-Dependent: effectiveness is not cell-cycle phase-specific
What are some examples of newer cancer drug targets?
-Senescent Cells, unlocking phenotypic plasticity, nonmutual epigenetic reprogramming, polymorphic microbiomes
-New Hallmarks of Cancer Paper
Receptor
a protein that recognizes and responds to a specific signal molecule
Ligand
general term for a small molecule that binds to a specific site on a macromolecule
Agonist
binds to the receptor and produces a similar response as the natural ligand
Agonist
binds to the receptor and produces a similar response as the natural ligand
Antagonist
binds to the receptor and blocks the natural ligand from binding
Signal Reception
detection of a signaling molecule from the outside of the cell
Signal Transduction
conversion of an impulse or stiumlus from one physical or chemical form to another; the process by which a cell responds to an extracellular signal
Endocrine Signaling
the most “public” style of cell-cell communication that involves broadcasting the signal throughout the whole body by using hormones; uses the bloodstream to broadcast
Paracrine Signaling
signal molecules diffuse locally through extracellular fluid to act as local mediators on the cells nearby
Neuronal Signaling
signal is transmitted electrically to synapse where neurotransmitter is released
Contact-Dependent Signaling
cells must be in direct membrane-membrane contact
Distinguish endocrine from synaptic signaling
-Endocrine: secreted hormones bind, circulate, and bind to specific receptors
-Neuronal delivers messages over long distances but to a specific target
Describe how the same signal can result in diverse responses
-The same signal can have a different response depending on what receptor it binds to
-Acetylcholine can decrease rate of firing in heart pacemaker, secrete in salivary glands, and contract muscle cells
Describe how multiple signals can integrate to cause a response
What are the three main classes of cell surface receptors?
-Ion-channel-linkedreceptors
-G-protein coupled receptors
-Enzyme-linked receptors
How do ion channel receptors work?
-Signal binds→ Confromational change of receptor→ion channel opens/closes→change in voltage across plasma membrane→effect
What is a signaling cascade?
-used by GPCRs and Enzyme Linked receptors
-Signal is first relayed, then amplified, then integrated, then distributed throughout the body
-is controlled by molecular switches
How do molecular switches work?
-When they receive a signal they are switched from an inactive state to an active
-They continue to stay in the active state until they are switched off
What is a GPCR and how does it work? What is a G protein?
-GPCR: cell surface receptor that associates with an intracellular trimeric GTP-binding protein after activation by an extracellular ligand; embedded in the membrane
-GPCRs work when a signal binds to the receptor which activates the G protein to phosphorylate GDP to GTP
-G protein: a membrane bound GTP binding protein involved in intracellular signaling; composed of 3 subunits, activated by the binding of a ligand to the receptor
What is a second messenger? Examples?
Second messengers: molecules that rapidly diffuse away from their source which amplifies and spreads the intracellular signal
-Examples: cAMP, IP3,DAG, Ca2+, and cGMP
How is cAMP made? How is it degraded?
-cAMP is formed from adenylate cyclase
-cAMP is degraded by cyclic AMP phophodiesterase
What is the difference between fast and slow responses to extracellular signals?
-Fast Response:
-occurs in seconds to minutes
-uses intracellular signaling pathway to alter protein function, then alters cytoplasmic machinery, then alters cell behavior
-Slow Response:
-occurs in minutes to hours
-Alters protein synthesis in the nucleus, then alters cytoplasmic machinery, then alters cell behavior
What is phospholipase C? What are some mediated responses?
-Phospholipase C: enzyme associated with the plasma membrane that generates two small messenger molecules in response to activation
-Responses: glycogen breakdown, amylase secretion, contraction, aggregation
What is PIP2 and how are IP3 and DAG formed from it? What is a downstream effect of these molecules?
What are enzyme linked receptors?
-Enzyme linked receptors: transmembrane proteins with their ligand-binding domain on the outer surface of the plasma membrane; either has intrinsic kinase activity or associates with a kinase; each subunit only has one transmembrane alpha helix
How does the insulin receptor work?
-Receptor Tyrosine Kinase
-Insulin receptor exsists in the membrane→Beta subunits transphosphorylate each other when insulin binds→Activated IR binds to insulin receptor substrate which mediates signaling
How are signals terminated?
-Signal termination takes place at several levels:
messenger degradation and diffusion, receptor downregulation(internalization) or desensitization, intracellular enzymes turn off signaling enzymes or degrade second messengers
How are receptors desensitized?
-Receptor Desensitation:
-receptor sequestration, receptor down regulation, receptor inactivation, inactivation of signaling protein, production of inhibitory proteins
Name 3 examples of integral (transmembrane) proteins and briefly describe what they do.
-Na+ pump: actively pumps Na+ out of cells and K+ into cells
-Integrins: link intracellular actin filaments to extracellular matrix proteins
-Adnelyly Cyclase: catalyzes the production of the small intracellular signaling molecule cAMP in response to extracellular signals
How would the amino acid composition of a single alpha helix that crosses the membrane differ from a series of alpha helices that form a pore together to cross the membrane?
What do tight junctions do for cells in a tissue layer?
Block proteins from passing in or out
What role to selectins and integrins play in recruiting immune cells to a site of infection? Where are these proteins found?
What is the relationship between the nuclear double membrane and the ER? What other organelle has a double membrane?
-Nucleus has a double lipid bilayer
-ER is out next to it and there is actually a connection between the outer nuclear membrane and the ER\
-Mitochondria has a double membrane
What is the most abundant organelle in a hepatocyte?
Mitochondria
What is a peptide signal sequence and how do signal sequences help send a protein to a particular destination?
-Peptide signal sequences are like zip codes for proteins
-It helps show them where to go based on the type of amino acid that is present in that signal sequence
What is the name of the pores that control entry and exit into the nucleus? What role do importins (nuclear import receptors) and exportins play in trafficking proteins?
How do mitochondrial proteins get into the matrix?
-They bind to import receptors which are located on protein translocators on the outer membrane
-It then lines up with the protein translocator on the inner membrane which will translocate the protein into the matrix
How do ER signal sequences and stop transfer sequences enable the production of transmembrane proteins?
-A hydrophobic start transfer sequence and a hydrophobic stop-transfer sequence are both located on one protein
-As the protein is moving through the protein translocator it is passing through the membrane, but once the stop sequence enters the translocator it stops
-This leaves part of the protein outside of the membrane, in the membrane, and inside of the membrane
What is the path of a vesicle from the ER to the release from the cell membrane during exocytosis?
Vesicle leaves the ER and goes through the Golgi, then transport vesicles take it through the cytosol and out of the membrane
What does clathrin do?
-Clathrin: protein that makes up the coat of a type of transport vesicle that buds from either the golgi or from the plasma membrane
What do T-snares and V-snares do?
-T-snares and V-snares help with endocytosis by helping to “dock” the transport vesicle to the lipid bilayer where it can fuse
What do lysosomes do? How does the environment in a lysosome facilitate what it does?
-Lysosome: membrane enclosed organelle that breaks down worn out proteins and organelles and other waste. Contains digestive enzymes that are typically most active at an acidic pH that is found inside these organelles
Family I of G Proteins
-Family I:
-Example: Gs
-action is mediated by alpha subunit
-Effect: activates adenyly cyclase; acttivates Ca2+ channels
Family II of G Proteins
-Family II:
-Example: Gi
-Action is mediated by: alpha subunit
-inhibits adneylyl cyclase
-Action is mediated by: beta and gamma subunits
-Effect: activates K+ channels
-Example: G0
-action is mediated by beta and gamma subunits
-Effect: activates K+ channels; inactivates Ca2+ channels
Family III of G Proteins
-Family III:
-Example: Gq
-Action is mediated by alpha subunit
-Effect: activates phospholipase C beta
