Biology Review Flashcards
(49 cards)
Why does rainwater have low salinity when the large bodies of water on Earth, such as seas and oceans, are very saline?
Most of the salt in the precipitates remains in the oceans
Intracellular changes are necessary to initiate embryonic stem cell differentiation. In certain cell types, reduced activity of the Na+–H+ exchanger (which normally brings Na+ in and H+ out of a cell) plays a major role in creating the proper intracellular conditions for differentiation.
Based on this information, what intracellular change is needed to initiate differentiation in these cells?
Decreased intracellular pH
What makes RNA less stable and more reactive than DNA?
RNA contains an extra hydroxyl group
Carbon is an important element that serves as a backbone for all life. Which part of our bodies contains the lowest percentage of carbon?
Vitreous humor
Trace evidence retrieved in a crime scene revealed 2 distinct monosaccharides upon infrared spectroscopic analysis. The victim was a scientist who was working with an enzyme that cleaves disaccharides. The spectroscopic analysis from the crime lab exactly matched the last entry on the victim’s electronic notebook. During their investigation, the forensics team analyzed carbohydrate samples from 4 suspects who had entered the crime scene in the past 24 hours. Each of the suspects had a unique carbohydrate sample that they needed to analyze.
Based on this evidence, which of the following carbohydrates did the most likely suspect possess?
Sucrose
A research associate wants to radioactively label thymine bases in a sample of DNA, using tritium (H3). The researcher was given this sample by a colleague who designed primers intending to amplify a product of 500 base pairs (bp) by polymerase chain reaction (PCR). This colleague faced significant difficulty amplifying the product, however, and sent the sample for sequencing. The sequencing laboratory reveals that the guanine base content in the sample is 40%.
Based on the sequencing results, what is the thymine base content of this sample?
10%
What are the main constituents of triglycerides?
Glycerol and fatty acid
A graduate student received organellar fractions from 4 different sources. The student was asked to extract DNA from each and was surprised to find 1 sample devoid of any genetic material.
Given that the student was careful and there were no mistakes in the extraction procedure, what source would be devoid of genetic material?
Red blood cells
You have isolated a group of cells containing the Na+/K+ pump in their cell membranes.
If you added a non-hydrolyzable analog of ATP to the solution outside the cell membrane, what effect would you expect to observe?
Na would accumulate outside the cell and K would accumulate inside the cell
Two cells in the body are touching, but they are separated by plasma membranes that only allow water to flow between the cells. Cell 1 has an osmolarity of 1.6 osm/L. Cell 2 has an osmolarity of 1.9 osm/L.
What will happen?
Water will flow from cell 1 to cell 2 until equilibrium is reached
Pinocytosis and phagocytosis are two important forms of endocytosis, in which cells ingest extracellular substances by surrounding and transporting the substances using vesicles. What is the most critical organelle for aiding to digest the ingested substances in vesicles?
Lysosome
Mature erythrocytes do not perform cellular respiration in the same way as other somatic cells. What metabolic difference exists between erythrocytes and other somatic cells?
ATP production is substantially lower in erythrocytes
The enzyme dihydrofolate reductase breaks folic acid into a precursor to thymine. The chemotherapy drug methotrexate binds to the same site on the enzyme as folic acid. What is true about methotrexate?
Methotrexate has a similar chemical structure to folic acid
Suppose that the reactant and product in a solution are in balance. Which of the following conditions will occur if an enzyme is poured into the solution?
Reaction stays at equilibrium
Adenosine triphosphate (ATP) is a nucleotide that plays a major role in many bioenergetic reactions by being consumed or produced. What is the accurate relationship between a bioenergetic reaction and ATP?
Mobilization of triacylglycerols from adipose tissue requires ATP
Kearns-Sayre Syndrome is a rare mitochondrial disorder first discovered as a condition of muscular weakness affecting the eyes and the heart. It affects an average of 2 in 100,000 individuals. It is a maternally inherited condition caused by large deletions (up to 2-10 kilobases) of mitochondrial DNA (mtDNA) that remove ~12 genes crucial for oxidative phosphorylation and ATP generation, resulting in defective mitochondrial output. The eyes and heart are typically affected most due to their high dependence on mitochondria for energy.
At present, there are no disease-modifying therapies available. The condition is generally managed by supportive care and regular cardiological and ophthalmological monitoring. With the advent of Crispr-assisted gene therapy, scientists believe that one day they will be able to find a way to inhibit mutant mtDNA replication and/or promote healthy mtDNA replication instead. Until then, however, KSS patients do not have any reliable treatments at hand.
Given the above information, what drug could be the most relevant treatment for managing Kearns-Sayre Syndrome?
Coenzyme Q10 (CoQ10), a fat-soluble cofactor that mediates electron transfer
Desulfurobacterium indicum is a bacterium that uses a process similar to eukaryotic cellular respiration. Instead of using oxygen as the final electron acceptor in the electron transport chain, however, this bacterium uses sulfur (S).
Assuming that sulfur behaves the same way as molecular oxygen (O2) in the electron transport chain, what do you predict as one of the products of the electron transport chain?
H2S
In eukaryotes, a defect in a certain biochemical system leads to an impairment of oxidative phosphorylation. This caused symptoms such as pigmenturia, exercise-induced myalgia, and elevated serum creatine kinase. During glycolysis, this biochemical system failed to translocate which of the following across the mitochondrial membrane?
Electrons
Suppose someone is deficient in pyruvate dehydrogenase, an enzyme that plays a crucial role in glycolysis. What would you expect to happen to ATP production in the cells of this individual?
Decrease
People with pyruvate dehydrogenase complex deficiency (PDCD) have an inherited lack of a key enzyme in cellular respiration. Patients with PDCD are usually placed on a ketogenic diet, which has very low amounts of sugars and other carbohydrates but is high in protein and fat.
By eating few sugars but more fat, the ketogenic diet prescribed to PDCD patients avoids what stage of cellular respiration?
Glycolysis
At puberty, human growth hormone (HGH or GH) is produced in the pituitary gland and released into the bloodstream. The growth hormone receptor (GHR) is located on the surface of a number of cells throughout the body, including cells in the liver. When bound to HGH, liver GHRs form dimers that are phosphorylated by the protein JAK2. This phosphorylation causes GHR to phosphorylate proteins called STATs. The STATs go to the nucleus, acting as transcription factors and causing proteins to be transcribed. This results in the liver cells producing the hormone IGF-2, which causes bone growth.
What type of signaling does HGH send to the liver cells?
Endocrine
A molecular biology graduate student is studying a new signaling molecule: annokine. The student discovers that if they add it to cells, those cells start to divide rapidly. When they first treat these cells with a pan-G-protein-coupled receptor (GPCR) inhibitor, however, annokine treatment does not provoke a response from the cells.
What conclusions can be drawn from this result?
GTPase activity is necessary for annokine’s cell division-inducing effect
Testosterone is a male hormone that is considered to be a fat-soluble signaling molecule. Which of the following pieces of information most appropriately explains why testosterone can cross all cell membranes but only selects the target cells?
Target cells have intracellular receptors
Chronic myeloid leukemia (CML) is a myeloproliferative disorder that occurs because of a chromosome translocation that results in the formation of BCR-ABL1 gene. This gene encodes the BCR-ABL1 fusion protein, a mutant tyrosine kinase that is constitutively active. Imatinib is a drug used to treat CML and results in long-term control of the disease in most patients.
What is the most likely mechanism of imatinib?
Inhibition of phosphorylation
