AP Biology Unit 4 Review
What is the expected percent change in the DNA content of a typical eukaryotic cell as it progresses through the cell cycle from the start of the G1 phase to the end of the G2 phase?
%100+
if a cell has 8 chromosomes how many chromosomes will each of its daughter cells have after cytokineses?
8
Which of the following is an example of a negative feedback mechanism?
A brown bat eats a grape, raising the glucose levels in its blood. As a result, enzymes and hormones are released to help break down the glucose levels back to a normal range.
Which of the following steps in a signaling pathway typically occurs first once a chemical messenger reaches a target cell?
A ligand binds to a receptor.
What is a G protein?
A protein on the cytoplasmic side of a membrane that becomes activated by a receptor protein.
Which of the following best describes a negative feedback mechanism?
A response in which the disruption is counteracted by the organism to return to homeostasis
What is the G0 phase?
A resting or non dividing phase where cells go. A cell can reenter division with appropriate signals. Non dividing cells may exit the cell cycle or be held in a particular stage.
What is a ligand?
A signaling molecule that binds to a receptor.
During which phase of mitosis do sister chromatids separate from each other?
Anaphase
Why is it necessary for organisms to use feedback systems to maintain homeostasis?
Because the internal and external environments that organisms are exposed to are constantly changing and they need a way to respond.
What is an example of negative feedback?
Body temperature or pH level of your blood.
How do organisms maintain a stable internal environment?
By using homeostasis or a target set point.
What does the blood calcium homeostatic loop do?
Calcitonin is secreted by the thyroid and it goes to the kidney and bones. The parathyroid secretes PTH hormones when it is too low.
What justifies the claim that differences in components of cell signaling pathways explain the different responses to epinephrine?
Cell signaling depends on the ability to detect a signal molecule. Not all cells have receptors for epinephrine. Only cells with such receptors are capable of responding.
What is cytokinesis?
Cell splits completely into 2 daughter cells each containing identical genomes.
Glycogen synthetase kinase 3 beta is a protein kinase that has been implicated in many types of cancer. Depending on the cell type, the gene for glycogen synthetase kinase 3 beta (GSK3β) can act either as an oncogene or as a tumor suppressor. Which of the following best predicts how GSK3β mutations can lead to the development of cancer?
Cells with inactive GSK3β fail to trigger apoptosis.
What is anaphase?
Chromatids pull apart with the help of centrioles or fibers separate double chromosomes into single chromosomes (chromatids), (chromosomes are separated at the centromere), single chromosomes (chromatids) migrate to opposite sides of the cell.
What is metaphase?
Chromosomes align at the middle of the cell or the fibers align double chromosomes across the center of the cell.
What is the S phase of mitosis?
Chromosomes duplicate (copies of DNA are made)
Which of the following presents a correct interpretation of the changes in chromosome number depicted in Figure 1 ?
Chromosomes enter metaphase containing two chromatids attached by a centromere. During anaphase, the chromatids are separated, each becoming a chromosome. Cytokinesis distributes the chromosomes into two separate cells.
What is telephase?
Chromosomes pulled to opposite sides of the cell. Cell begins to divide into 2 daughter cells. The nuclear envelope reappears and establishes two separate nuclei, each contains a complete genome, chromosomes will begin to uncoil.
Notch is a receptor protein displayed on the surface of certain cells in developing fruit fly embryos. Notch's ligand is a membrane-bound protein called Delta that is displayed on the surface of adjacent cells. When Notch is activated by its ligand, the intracellular tail of the Notch protein becomes separated from the rest of the protein. This allows the intracellular tail to move to the cell's nucleus and alter the expression of specific genes. Which of the following statements best explains Delta's role in regulating cell communication through the Notch signaling pathway?
Delta restricts cell communication to short distances within a developing embryo.
What does cytokinesis ensure?
Equal distribution of cytoplasm to both daughter cells.
Blood clots are formed by a positive feedback loop. Two pathways exist, the extrinsic and intrinsic pathways, which converge during clot formation. There are many clotting factors involved, most of which are proteins. Vitamin K is required for the formation of the active form of several of the clotting factors, including Factor X. Warfarin is a drug used to treat certain blood clots. Warfarin blocks the formation of the active form of vitamin K-dependent clotting factors. Based on the model, which of the following best predicts the effects of warfarin on a patient?
Factor X will not be activated, which will prevent thrombin from forming.
What does the maintaining temperature homeostatic loop do?
Hypothalamus (the thermostat of our bodies) measures the temperature of our blood. If the temp goes above 37 degrees, we send a message to the capillaries and sweat glands. If it goes below 37 degrees, we send a message to the muscles, capillaries, and skin.
A person's blood glucose level fluctuates during the day, as represented in Figure 1. Two hormones, insulin and glucagon, are directly involved in regulating the blood glucose level to maintain a healthy level. Insulin acts to lower the blood glucose level, and glucagon acts to increase the blood glucose level. Which of the following best predicts what will happen to the blood glucose level if the person has another meal at 5 p.m.?
Immediately after the meal, the blood glucose level will increase, and then insulin will be secreted to counter the increase.
The epidermal growth factor receptor EGFR is a cell surface receptor. When a growth factor binds to EGFR, the receptor is activated. The activated EGFR triggers a signal transduction pathway, which leads to increased frequency of cell division. Which of the following best predicts the effect of a mutation that causes EGFR to be active in the absence of a growth factor?
Increased cell division will lead to the formation of a tumor.
What are signal transduction pathways used for?
Influencing cellular responses when the environment changes.
The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. Which of the following statements best describes the role of adenylyl cyclase in the epinephrine signaling pathway?
It accelerates the production of a second messenger.
Which of the following statements best describes the role of adenylyl cyclase in the epinephrine signaling pathway?
It accelerates the production of a second messenger.
In a certain signal transduction pathway, the binding of an extracellular molecule to a cell-surface protein results in a rapid increase in the concentration of cyclic AMP inside the cell. The cyclic AMP binds to and activates cytosolic enzymes that then activate other enzymes in the cell.
It acts as a second messenger that helps relay and amplify the signal within the cell.
In a certain signal transduction pathway, the binding of an extracellular molecule to a cell-surface protein results in a rapid increase in the concentration of cyclic AMP inside the cell. The cyclic AMP binds to and activates cytosolic enzymes that then activate other enzymes in the cell. Which of the following statements best describes the role of cyclic AMP in the signal transduction pathway?
It acts as a second messenger that helps relay and amplify the signal within the cell.
The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. Which of the following statements best describes the epinephrine signaling pathway?
It involves enzymes activating other enzymes.
Phosphofructokinase (PFK)is a key enzyme in glycolysis. ATPis one of the two substrates for the reaction catalyzed by PFK. ATP is also an allosteric regulator of PFK. Figure 1 shows the enzyme-substrate interactions of PFK. A researcher found a mutation that resulted in the PFK enzyme being unable to bind ATP to the allosteric site. Which of the following best predicts the effect of the mutation?
Negative feedback regulation does not occur, so the enzyme will be active when glycolysis is not needed.
What is prophase?
Nuclear membrane disappears and centrioles attach to chromosomes at the centromeres. DNA also coils into visible chromosomes and the fibers begin to move double chromosomes toward the center of the cell.
The beta-2 adrenergic receptor is a membrane-bound protein that regulates several cellular processes, including the synthesis and breakdown of glycogen. The receptor binds specifically to the hormone epinephrine. The binding of epinephrine to the beta-2 adrenergic receptor triggers a signal transduction cascade that controls glycogen synthesis and breakdown in the cell. Which of the following outcomes will most likely result from the inactivation of the beta-2 adrenergic receptor?
Protein Kinase A will not be activated, therefore unable to inhibit Glycogen Synthase.
What is the best description of the difference between "Receptors" and "Effectors", as described in Homeostatic Loops?
Receptors sense stimuli, while effectors respond to it.
What is an example of positive feedback?
Ripening fruit. An apple ripens and produces ethylene gas. It is detected by nearby apples and those apples begin to ripen and release the gas. The process repeats and amplifies.
In flowering plants, plasmodesmata are narrow channels through cell walls that connect the cytoplasms of adjacent cells. An explanation of how plant cells communicate across cell walls will most likely refer to the diffusion through plasmodesmata of which of the following?
Small, water-soluble molecules.
Which of the following best describes how the amount of DNA in the cell changes during M phase?
The amount of DNA is halved as the cell divides into two daughter cells.
What is the G1 phase of mitosis?
The cell grows.
What is the G2 phase of mitosis?
The cytoplasmic components are doubled in preparation for division.
Cancer cells behave differently than normal body cells. For example, they ignore signals that tell them to stop dividing. Which of the following conditions will most likely cause a normal body cell to become a cancer cell?
The environment contains mutagens that induce mutations that affect cell-cycle regulator proteins.
Glucocorticoids are steroid hormones that control cellular responses through several different signaling pathways. One of the signaling pathways involves the glucocorticoid receptor, an intracellular protein that is activated by binding to a glucocorticoid molecule. Which of the following statements best predicts the effect of a mutation that results in a loss of the glucocorticoid receptor's ligand binding function?
The glucocorticoid receptor will remain associated with the accessory proteins.
A hydrophilic peptide hormone is produced in the anterior pituitary gland located at the base of the brain. The hormone targets specific cells in many parts of the body. Which of the following best explains a possible mechanism that would enable the hormone to efficiently reach all of the target cells in the body?
The hormone is released into the bloodstream where it can be transported to all cells with the correct receptors.
What does the blood glucose homeostatic loop do?
The insulin makes a signal transduction pathway that opens up a protein (a glut) that is a glucose transport. It allows the glucose to go into the cell. the liver turns glucose into glycogen. These lower the blood glucose. If its lower, the pancreas makes glycogen and the liver converts glycogen back into glucose.
The epinephrine signaling pathway plays a role in regulating glucose homeostasis in muscle cells. The signaling pathway is activated by the binding of epinephrine to the beta-2 adrenergic receptor. Which of the following outcomes will most likely result from the irreversible binding of GDP to the G protein?
The intracellular concentration of glycogen will increase.
What is the signal transduction order?
The ligand fits into the active site of the receptor. G-protein cleaves off an alpha-subunit. Alpha-subunit travels to Adenylyl Cyclase. Adenylyl cyclase creates cAMP from ATP. cAMP binds to the regulatory portion of Kinase. Catalytic portions of Kinase are phosphorylated by ATP. Catalytic portions of Kinase activate Phosphorolase. Phosphorylase cuts up glycogen, releasing glucose.
Figure 1 shows a model of a signal transduction cascade, initiated by the binding of a ligand to the transmembrane receptor protein A. A DNA mutation changes the shape of the extracellular domain of transmembrane receptor protein A produced by the cell. Which of the following predictions is the most likely consequence of the mutation?
The molecule that normally binds to protein A will no longer attach, deactivating the cellular response.
The insulin receptor is a transmembrane protein that plays a role in the regulation of glucose homeostasis. The receptor's extracellular domain binds specifically to the peptide hormone insulin. The receptor's intracellular domain interacts with cellular factors. The binding of insulin to the receptor stimulates a signal transduction pathway that results in the subcellular translocation of GLUT4, a glucose transport protein that is stored in vesicles inside the cell. Which of the following statements best predicts the effect of a loss of function of the insulin receptor's intracellular domain?
The number of GLUT4 molecules in the plasma membrane will increase.
Vertebrate immune responses involve communication over short and long distances. Which of the following statements best helps explain how cell surface proteins, such as MHC proteins and T cell receptors, mediate cell communication over short distances?
The proteins interact directly with proteins on the surfaces of other cells.
The coagulation cascade controls blood clot formation in response to blood vessel injury. Thrombin is an enzyme that plays a key role in regulating the coagulation cascade. Argatroban is a competitive inhibitor of thrombin. Which of the following effects on the coagulation cascade is most likely to result from inhibiting thrombin activity with argatroban?
The rate of fibrin formation will decrease.
What does mitosis ensure?
The transfer of a complete genome from a parent cell to two genetically identical daughter cells.
Researchers studying cell cycle regulation in budding yeast have observed that a mutation in the CDC15 gene causes cell cycle arrest in telophase when the yeast cells are incubated at an elevated temperature. Which of the following statements best predicts the effect of the cell cycle arrest on proliferating yeast cells?
The yeast cells will replicate their chromosomes but will fail to complete cytokinesis.
Which statement best predicts why a cell's progression through the cell cycle might be halted at the G1/S checkpoint?
There are not enough nucleotides available to construct new DNA .
Adjacent plant cells have narrow channels called plasmodesmata that pass through the cell walls of the connected cells and allow a cytoplasmic connection between the cells. Which of the following statements best describes a primary function of plasmodesmata?
They allow the movement of molecules from one cell to another, enabling communication between cells.
What is positive feedback and what does it do?
They amplify responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial set point, disrupting homeostasis.
What are kinases?
They are enzymes that add a phosphate to other proteins to activate or inhibit their function-process called phosphorylation. They are always present in the cell but they become activated when bound to other proteins called cyclins.
What is true of the homeostatic loops presented in the video?
They are negative feedback loops
What are feedback mechanisms?
They are processes used to maintain homeostasis by increasing or decreasing a cellular response to an event.
What can transduction pathways do?
They can regulate gene expression in response to changes in the environment or lead to apoptosis.
What are mutated tumor suppressor genes?
They cause a loss of inhibitation which is similar to acceleration in cell division.
What is negative feedback and what does it do?
They maintain homeostasis for a particular condition by regulating physiological processes. If a system is disrupted, negative feedback mechanisms return the system back to its target set point.
What does osmolarity (concentration of the blood) homeostatic loop do?
When osmolarity goes up, a human is dehydrated (more solutes per solution). Hypthalamus senses it and sends a message to the pituitary glands. Pituitary releases a chemical called ADH which tells the kidney to hold onto more water (makes yellower pee). If osmolarity goes down, we send less ADH to the pituitary.
G-proteins are a family of receptor proteins that are involved in transmitting signals from outside a cell to inside a cell. When a signaling molecule binds to a G-protein, the G-protein is activated. The G-protein then activates an enzyme that produces a second messenger called cAMP. Which of the following describes a critical role of cAMP during the transduction stage of a G-protein signal transduction pathway?
cAMP results in the activation of an enzyme that amplifies the signal by acting on many substrate molecules.
What is differentiation?
cells stop dividing to specialize in structure and function.
What are the most important cell cycle regulators?
cyclin-dependent kinases (CDKs)
DNA replication occurs?
during the S phase of the cell cycle.
What are tumor suppressor genes?
genes that normally prevent cell division.
which of the following is true of mitosis?
it maintains the same chromosome number in the daughter cells as in the parent cell.
What are cell cycle regulators?
molecular signals that may stimulate or halt cell division, instruct cells to differentiate, or initiate cell death.
What are oncogenes?
mutated proto-oncogenes that accelerate and increase stimulation, causing cancer.
What are proto-oncogenes?
normal versions of oncogenes. They encode for proteins that stimulate normal cell growth & division.
