Insta-Review
Unit 4
Courtesy of @APBioPenguins
4.1: Cell Communication
4.1: Cell Communication
IST-3.A.1
Cells communicate with one another through direct contact with other cells or from a distance via chemical signaling—
a. Cells communicate by cell-to-cell contact.
IST-3.B.1
Cells communicate over short distances by using local regulators that target cells in the vicinity of the signal-emitting cell—
a. Signals released by one cell type can travel long distances to target cells of another cell type
What extracellular component aids in direct cell-cell communication?
What extracellular component aids in direct cell-cell communication?
Signaling where ligand binds to nearby cell…
Signaling where ligand binds to nearby cell…
Signal that binds to the secreting cell…
Signal that binds to the secreting cell…
What type of signaling is shown?
What type of signaling is shown?
Describe the pathway of signaling molecule released from the cell.
Describe the pathway of signaling molecule released from the cell.
4.2 Introduction to Signal Transduction
4.2: Introduction to Signal Transduction
IST-3.C.1
Signal transduction pathways link signal
reception with cellular responses.
IST-3.C.2
Many signal transduction pathways include protein modification and phosphorylation cascades.
4.2: Introduction to Signal Transduction
IST-3.D.1
Signaling begins with the recognition of a
chemical messenger—a ligand—by a receptor protein in a target cell—
a. The ligand-binding domain of a receptor recognizes a specific chemical messenger,
which can be a peptide, a small chemical, or protein, in a specific one-to-one relationship.
b. G protein-coupled receptors are an example of a receptor protein in eukaryotes.
4.2: Introduction to Signal Transduction
IST-3.D.2
Signaling cascades relay signals from receptors to cell targets, often amplifying the incoming signals, resulting in the appropriate responses by the cell, which could include cell growth, secretion of molecules, or gene expression—
a. After the ligand binds, the intracellular domain of a receptor protein changes shape, initiating transduction of the signal.
b. Second messengers (such as cyclic AMP) are molecules that relay and amplify the intracellular signal.
c. Binding of ligand-to-ligand-gated channels can cause the channel to open or close
What is the first step of signal transduction?
What is the first step of signal transduction?
What occurs during the step of reception?
What occurs during the step of reception?
The signaling molecule binds to the receptor.
The receptor undergoes a conformational change (changes shape).
What is the signaling molecule called?
What is the signaling molecule called?
How does the polarity of the ligand affect the location of the receptor?
How does the polarity of the ligand affect the location of the receptor?
If the ligand is polar – the receptor will be membrane bound. Polar substances are unable to pass through the membrane.
If the ligand is nonpolar – the receptor will be intracellular. Nonpolar substances are able to pass through the membrane (so the receptor must be inside).
The ligand travels through the signal transduction path.
The ligand travels through the signal transduction path.
What is the function of transduction?
What is the function of transduction?
To bring the message to its location for response
To amplify the signal/message
To regulate the signal
All cells respond to the same ligand with the same response.
All cells respond to the same ligand with the same response.
What happens during a phosphorylation cascade?
What happens during a phosphorylation cascade?
Protein kinase will phosphorylate (add a phosphate to) a relay protein
This activated relay protein will phosphorylate the next relay until the signal reaches the response.
What happens during a phosphorylation cascade?
What happens during a phosphorylation cascade?
Identify some possible responses.
Identify some possible responses.
Cell growth
Secretion of molecules
Gene expression
Apoptosis
Which is a secondary messenger?
Which is a secondary messenger?
What happens if the receptor is a ligand gated receptor?
What happens if the receptor is a ligand gated receptor?
Conformational change opens the gate and allows for the specific ions for that channel to flow down their concentration gradient.
4.3 Signal Transduction
4.3: Introduction to Signal Transduction
IST-3.E.1
Signal transduction pathways influence how the cell responds to its environment.
IST-3.F.1
Signal transduction may result in changes in gene expression and cell function, which may alter phenotype or result in programmed cell death (apoptosis).
What are possible responses from a signal transduction pathway?
What are possible responses from a signal transduction pathway?
Describe the function of a transcription factor (& how it changes gene expression)
Describe the function of a transcription factor (& how it changes gene expression)
Transcription factors bind to the DNA to assist with the binding of RNA polymerase
If the transcription factor binds, the rate of transcription increases as RNA polymerase binds more frequently/more stable binding
What is apoptosis? What occurs?
What is apoptosis? What occurs?
Programmed cell death
This is a process of the cell digesting from the inside out. There is a major error in the cell or the cell is infected so to protect the organism the cells go through the process to rid of themselves. Also, this could occur due to development. The spaces between our fingers results from apoptosis.
What is apoptosis? What occurs?
4.4 Changes in Signal Transduction Pathways
4.4 Changes in Signal Transduction Pathways
IST-3.G.1
Changes in signal transduction pathways can alter cellular response—
a. Mutations in any domain of the receptor
protein or in any component of the signaling pathway may affect the downstream components by altering the subsequent transduction of the signal.
IST-3.G.2
Chemicals that interfere with any component of the signaling pathway may activate or inhibit the pathway.
If there is a mutation in the receptor protein, predict what will happen to cell?
If there is a mutation in the receptor protein, predict what will happen to cell?
Three possible answer (and this could happen on an FRQ)
If they want you to give a specific answer, they would give you a diagram, information, or graph that could interpret to state more conclusively which one it would be.
Inhibitor that binds to the active site inhibiting substrate
Inhibitor that binds to the active site inhibiting substrate
How do you overcome a competitive inhibitor?
How do you overcome a competitive inhibitor?
Increase the substrate concentration
The process is about which molecule is more likely to bind to the active site. If you have twice as many substrates as inhibitors, there is a higher probability that the substrate will bind to the active site.
How does a noncompetitive inhibitor inhibit substrate binding?
How does a noncompetitive inhibitor inhibit substrate binding?
Binds to a separate location on the enzyme (allosteric site) which leads to a shape change. This shape change inhibits the ability for the substrate to bind to the active site.
Which cells will respond to a signaling molecule?
Which cells will respond to a signaling molecule?
Cells with a receptor to bind to signaling molecule
If it has a receptor that will bind with the signaling molecule, then it will be able to have a response. If the signaling molecule does not bind, there will be no response from the cell.
4.5 Feedback
4.5 Feedback
ENE-3.A.1
Organisms use feedback mechanisms to maintain their internal environments and respond to internal and external environmental changes.
ENE-3.B.1
Negative feedback mechanisms maintain homeostasis for a particular condition by
regulating physiological processes. If a system is perturbed, negative feedback mechanisms return the system back to its target set point. These processes operate at the molecular and cellular levels.
4.5 Feedback
ENE-3.C.1
Positive feedback mechanisms amplify responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial set point. Amplification occurs when the stimulus is further activated, which, in turn, initiates an additional response that produces system change.
Why is negative feedback essential for cell?
Why is negative feedback essential for cell?
Oxytocin is released to initiate contractions, the force of the baby on the cervix leads to release of oxytocin, which causes more contractions. What type of feedback is described?
Oxytocin is released to initiate contractions, the force of the baby on the cervix leads to release of oxytocin, which causes more contractions. What type of feedback is described?
Describe positive feedback
Describe positive feedback
The product is used to amplify the response.
In the previous example, the product (oxytocin) leads to an increase in contractions which pushes the babies’ head harder on the cervix so more oxytocin is released.
Most feedback is…
Most feedback is…
Blood glucose level is high, pancreas releases insulin. The insulin causes the cells to take up blood sugar so the sugar level decreases. Which type of feedback is described above?
Blood glucose level is high, pancreas releases insulin. The insulin causes the cells to take up blood sugar so the sugar level decreases. Which type of feedback is described above?
Trp operon only makes tryptophan when trp is absent from the environment. Which type of feedback is described?
Trp operon only makes tryptophan when trp is absent from the environment. Which type of feedback is described?
Big Picture:
Negative feedback brings you back to homeostasis or decreases wasting energy/materials
Positive feedback is an amplification to cause a response
Lac operon is only synthesized the materials to break down lactose in the presence of lactose. What type of feedback is described?
Lac operon is only synthesized the materials to break down lactose in the presence of lactose. What type of feedback is described?
When a fruit ripens it releases ethylene. Ethylene causes fruit to ripen so more ethylene is released. What type of feedback is described?
When a fruit ripens it releases ethylene. Ethylene causes fruit to ripen so more ethylene is released. What type of feedback is described?
4.6 Cell Cycle
4.6 Cell Cycle
IST-1.B.1
In eukaryotes, cells divide and transmit genetic information via two highly regulated processes.
IST-1.B.2
The cell cycle is a highly regulated series of events for the growth and reproduction of cells—
a. The cell cycle consists of sequential stages of interphase (G1, S, G2), mitosis, and cytokinesis.
b. A cell can enter a stage (G0) where it no longer divides, but it can reenter the cell cycle in response to appropriate cues. Nondividing cells may exit the cell cycle or be held at a particular stage in the cell cycle.
4.6 Cell Cycle
IST-1.C.1
Mitosis is a process that ensures the transfer of a complete genome from a parent cell to two genetically identical daughter cells—
a. Mitosis plays a role in growth, tissue repair, and asexual reproduction.
b. Mitosis alternates with interphase in the cell cycle.
c. Mitosis occurs in a sequential series of steps
(prophase, metaphase, anaphase, telophase)
What are the three phases of the cell cycle?
What are the three phases of the cell cycle?
Interphase
Mitosis
Cytokinesis
Note:
Interphase is BEFORE mitosis and cytokinesis is AFTER mitosis
Which phase of interphase does the cell grow?
Which phase of interphase does the cell grow?
Which phase of interphase does DNA replication occur?
Which phase of interphase does DNA replication occur?
Mitosis divides…
Mitosis divides…
Cytokinesis divides…
Cytokinesis divides…
A cell can undergo mitosis and not cytokinesis
A cell can undergo mitosis and not cytokinesis
What is the result of mitosis without cytokinesis? Example.
What is the result of mitosis without cytokinesis? Example.
The cell will be multinucleated (so the cell will have multiple nuclei)
Ex: muscle cells
If the cell doesn’t get the go ahead at G1 checkpoint what happens?
If the cell doesn’t get the go ahead at G1 checkpoint what happens?
The cell enters a non-dividing state called G0.
Identify an example of a cell in G0.
Identify an example of a cell in G0.
Neurons
Muscles
Liver
Which phase involves sister chromatids on middle plate?
Which phase involves sister chromatids on middle plate?
Which phase involves sister chromatids pairing?
Which phase involves sister chromatids pairing?
Which phase involves single chromatids moving to poles?
Which phase involves single chromatids moving to poles?
Which phase involves nuclear envelope forming?
Which phase involves nuclear envelope forming?
Cancer treatment involves chemotherapy with drugs that inhibit microtubules from depolymerizing. Which phase would the cell be stopped in?
Cancer treatment involves chemotherapy with drugs that inhibit microtubules from depolymerizing. Which phase would the cell be stopped in?
How does the parent and daughter cell compare in mitosis?
How does the parent and daughter cell compare in mitosis?
Parent cell AND daughter cells are diploid (2N)
Parent cell AND daughter cells are genetically identical
How many rounds of replication of DNA before mitosis?
How many rounds of replication of DNA before mitosis?
How many rounds of division in mitosis?
How many rounds of division in mitosis?
Independent Assortment?
Independent Assortment?
Crossing Over?
Crossing Over?
4.7 Regulation of Cell Cycle
4.7 Regulation of Cell Cycle
IST-1.D.1
A number of internal controls or checkpoints regulate progression through the cycle.
IST-1.D.2
Interactions between cyclins and cyclin-dependent kinases control the cell cycle.
IST-1.E.1
Disruptions to the cell cycle may result in cancer and/or programmed cell death (apoptosis).
Which checkpoint determines whether the cell will divide?
Which checkpoint determines whether the cell will divide?
Which checkpoint inhibits nondisjunction?
Which checkpoint inhibits nondisjunction?
Which checkpoint verifies DNA has “no errors” and replicated?
Which checkpoint verifies DNA has “no errors” and replicated?
What is the function of a kinase?
What is the function of a kinase?
Kinase is an enzyme that adds phosphate
Protein kinase is responsible for the phosphorylation cascade in transduction
Cyclin dependent kinase will phosphorylate proteins needs for cell division
Describe the association between cyclin and CdK.
Describe the association between cyclin and CdK.
Cyclin is produced during interphase. CdK is maintained at high levels in the cell. When the cyclin level reaches a certain amount, it will activate the CdK and allow for the progression into the M phase. This specific CdK is called MPF. Maturation Promoting Factor
(but let’s just call it mitosis promoting factor since you need it to enter mitosis)
Question
What happens if the cell incorrectly bypasses a checkpoint?
What happens if the cell incorrectly bypasses a checkpoint?
Cancer
Apoptosis