Bio Exam 4
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| Location of Translation | Ribosomes
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| Translation | Informational transfer from mRNA to protein.
Also called protein synthesis.
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| tRNA in translation | tRNA brings amino acids to the ribosomes
forms loops and stems
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| anticodon | binds to codon on mRNA on the opposite end of the site of the amino acid
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| "E" site in large ribosomal subunit | holds a tRNA that will exit
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| "P" site in large ribosomal subunit | holds the tRNA with growing polypeptide attached
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| "A" site in large ribosomal subunit | holds an aminoacyl tRNA
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| translation - initiation | mRNA binds to small subunit.
tRNA binds to AUG codon.
Large subunit binds to complete assembly.
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| translation - elongation | Second tRNA binds to "A" site.
Peptide bond forms between 1st and 2nd amino acids.
tRNA that was in "P" site no longer has an attached amino acid and enters "E" (exit) site.
New tRNA moves into "A" site.
Repeats until reaches stop codon (termination).
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| translation - termination | tRNA with release factor binds to "A" site.
Protein is released.
Ribosome subunits separate.
mRNA is released.
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| Tumor | Cells whose cell division is unregulated, creating a mass of cells.
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| Proto-Oncogenes | Determines if the cell signal was received for it to go through the cell cycle, if it has been then it pushes the cell forward.
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| Tumor Suppressors | Look for DNA damage and stop the cell cycle if it is present.
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| MPF | Mitosis promoting factor
Activates all the proteins required for S phase for DNA replication.
Caused by cyclin binding in cdk and removing the phosphate group, activating it.
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| Growth factors | Are peptide hormones received by cell by binding to receptor on cell surface (Signal Transduction via Enzyme-Linked receptors)
Causes a phosphorylation cascade.
Cyclin will bind in cdk and remove the phosphate group, activating it, which is MPF.
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| 2 proteins needed for E. coli bacteria to utilize lactose | A transporter protein to take lactose into cells.
An enzyme to break lactose into 2 monomers.
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| lac genes | produce the proteins needed for bacteria to utilize lactose (A transporter protein and an enzyme)
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| When lactose is absent, what is bound to the lac operon? | A repressor binds to DNA and transcription is blocked. Binds to the regulatory sequence of DNA (operator)
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| When lactose is present, how is transcription of the lac genes activated? | Lactose (the inducer) binds to repressor.
Repressor releases from DNA and transcription occurs.
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| What happens to expression of the lac genes when glucose levels are high? Why? | Transcription of lac operon is drastically reduced.
Glucose inhibits the lactose transport activity of galactoside permease.
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| operons | Gene clusters that contains genes that produce proteins that function together.
All genes in the cluster are controlled by the same promoter.
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| lac I gene | A gene that has its own promoter and is always active.
Produces a repressor protein.
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| operator | Binds to regulatory sequence of DNA.
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| In chromatin structure, each nucleosome is: | a DNA double helix wrapped twice around a package of histone proteins.
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| HDAC | Histone Deacetylase
Removes acetyl group from histone when DNA gets packed
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| HAT | Histone Acetyl Transferase
Adds acetyl group to histone when DNA gets loosened
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| Epigenetic changes | when the bases of DNA are not changed but chemical modifications are added (methyl groups or acetyl groups) that alter gene expression
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| Epigenetic inheritance | Patterns of Histone modifications can be inherited by daughter cells during cell division.
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| Regulatory transcription factors | proteins that bind
to regulatory sequences on the DNA.
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| Communication via extracellular signals involves 6 steps: | 1. Synthesis of signal
2. Release of signaling molecule outside the cell
3. Transport of signaling molecule to target cells
4. Detection of signal by receptor protein
5. Signal Processing & Cellular response to signal
6. Deactivation of signal
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| Endocrine signaling | signals (hormones) act on target cells distant from site of synthesis
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| Paracrine signaling | signals act on target cells in close proximity
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| Autocrine signaling | signals act on the cells that synthesized the signal
Ex. Growth factors
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| What else besides chemicals can act as signals? | Light
Touch
Sound
Temp
Vibrations
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| Signal reception | The presence of a protein receptor for a particular signal determines which cells will respond to a particular signal.
Ex: responds to estrogen only if it has estrogen receptor.
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| Receptors | Proteins that are dynamic
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| Lipid-soluble signals | type of signal can easily enter a cell and bind to its receptor within the cell
processed directly
ex. steroids
The receptor is also the regulatory transcription factor.
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| Lipid-insoluble | signals that must interact with its receptors at the cell surface
Require transduction
Ex: growth factors
The receptor does not act as the regulatory transcription factor but activates or produces intracellular signaling molecules.
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| Transduction | conversion of a extracellular signal to an intracellular signal
Uses G proteins and Enzyme-linked receptors
In process, signal gets amplified.
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| For cell-surface receptors, what are the two pathways by which the information transduced within the cell? | Signal transduction via G protein coupled receptors
Signal transduction via Enzyme-Linked proteins
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| Signal transduction via G protein coupled receptors | B4 signal binds to receptor, it’s in the “off” state, GDP is bound to 1 of 3 G proteins.
Signal binds to receptor, GDP leaves, GTP binds to G protein, activating it/on.
Activating an enzyme that generates second messengers, activating transc. factors.
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| Signal transduction via Enzyme-Linked proteins | Receptor is separated
When signal binds to the receptor, the receptor comes together.
Receptor Self-phosphorylates (adding a phosphate group)
Phosphorylation = ATP group goes unused.
Now the receptor is highly active. This actives a protein called Ras
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| Ras | Ras kicks out GDP and binds to GTP
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| Often called the molecular on switch | GTP
It activate G proteins that activate the enzyme that generates second messengers that active transcription factors.
It turns on signaling pathways
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| Second messengers | a small molecule produced in a large amount by an enzyme being activated by the GTP bound subunit binding and activating it.
(Signal transduction via G protein coupled receptors)
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| What is a phosphorylation cascade? What type of signaling pathway is it associated with? | Ras phospholylates a protein, then another, +
protein is phosphorylated = it’s adding a phosphate group, and its being activated.
Basically turning on a bunch of proteins, Amplifying it.
Ultimately, at the end, a transcription factor is activated.
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| What is the master tumor suppressor protein? What is its main job (what does it activate)? | p53
Oversees all the little things that can stop the cell cycle.
Main job is to scan DNA and determine if it has any damage
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| p53, if DNA is in good shape (intact) | the break will go off (gas is pushed), and it will allow the cells to go into the S phase.
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| p53, if DNA is in bad shape (damaged) | it will assess whether the DNA damage can be repaired.
If it is repairable, it will stop the cell cycle, and hold it in G1, and active all the proteins to repair the DNA.
If not repairable, the cell kills itself; Apoptosis.
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| Apoptosis | Cell killing itself when p53 sees that it is damaged and not repairable.
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| mutation | One mechanism where cell cycle proteins can become defective
change in base sequence (shape)
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| When does mutation occur? | During DNA replication; making a mistake in base pairing.
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| What fixes mutations? | DNA polymerase can fix it, but can miss the mistakes
p53/ other tumor suppressors are able to remove the wrong bases and insert the correct bases
DNA repair enzymes are constantly scanning DNA and repairing errors and damage (many are activated by p53)
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| Carcinogens | Chemicals that cause high rates of DNA mutations affect cell cycle control genes.
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| Cell differentiation | There are hundreds of different types of cells in your body
They look different because certain cells are turned on and turned off
If pattern of which cells need to be turned on and off gets messed up, they theres a problem with cell differentiation.
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| Benign tumors | defects are only in cell division (unregulated)
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| Malignant tumors | defects are in cell division and cell differentiation
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| Targeted cancer therapy | identifies defective cellular pathways and targets. Especially effective for tumors resulting from high mitogens (breast).
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| Chemotherapy | targets all rapidly dividing cells in body
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| Radiation | ionizing radiation that damages DNA - thought that tumor cells are more susceptible.
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| Cell signaling | 1. reception of a signaling molecule
2. transduction of the signal
3. response to the signal
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| LEARNING CATALYTICS In what environmental conditions would you expect to measure high levels of gene expression of the lac operon in E.coli? | low levels of glucose and high levels of lactose
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| LEARNING CATALYTICS What would you measure to determine if the lac operon is active? | Levels of beta galactosidase and permease
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| LEARNING CATALYTICS Which of the following is an epigenetic change? | DNA methylation
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| LEARNING CATALYTICS Which of the following is true of cell signaling? | It integrates information about the environment
It activates transcription factors
It requires receptor proteins
It alters gene expression
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| LEARNING CATALYTICS What protein modification activates intercellular signaling proteins? | Phosphorylation
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| LEARNING CATALYTICS What type of signaling molecule can bind intercellular receptors that then act as transcription factors? | lipid hormones
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| LEARNING CATALYTICS What relays the information from an activated cell surface receptor and intercellular proteins that act as transcription factors? | second messengers
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| A(n) _____ is an example of a signal molecule that can bind to an intracellular receptor and thereby cause a gene to be turned on or off. | steroid
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| Which of these extracellular signal molecules could diffuse through a plasma membrane and bind to an intracellular receptor? | estrogen
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| Regulatory proteins bind to _____. | the operator
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| In the presence of a regulatory protein the lac operon is _____. | not transcribed
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| A(n) _______ is a stretch of DNA consisting of an operator, a promoter, and genes for a related set of proteins, usually making up an entire metabolic pathway. | operon
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| The ________ is/are arranged sequentially after the promoter. | genes of an operon
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| A(n) ________ is a specific nucleotide sequence in DNA that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place. | promoter
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| A(n) ________ codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes. | regulatory gene
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| Regulatory proteins often bind to the ______ to control expression of the operon. | operator
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| A(n) ________ is a protein that inhibits gene transcription. In bacteria, this protein binds to the DNA in or near the promoter. | repressor
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| A(n) ______ is a specific small molecule that binds to a bacterial repressor protein and changes its shape so that it cannot bind to an operator, thus switching an operon on. | inducer
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