Water molecules form hydrogen bonds between adjacent molecules because of their polar covalent structure. Which property of water directly results from hydrogen bonding and allows water striders to walk across the surface of a pond?
Basic Biology And Bioenergetics
Question · Easy
Km or Vmax: an aria of rivals
Short
Enzymes are biological catalysts that speed up chemical reactions in living organisms. How do enzymes increase the rate of a biochemical reaction?
Adenosine triphosphate (ATP) serves as the primary energy currency of the cell. Which process directly yields the energy needed to power cellular work such as muscle contraction?
Which general chemical equation correctly summarizes the overall process of aerobic cellular respiration?
A student measures the rate of an enzyme-catalyzed reaction across a temperature range from 10°C to 60°C. The reaction rate rises steadily until 37°C, after which it drops sharply to zero by 55°C. What best explains the rapid decline in activity above 37°C?
Question · Medium
During the light-dependent reactions of photosynthesis, water molecules are split in a process known as photolysis. What are the essential biological products of photolysis?
In plant chloroplasts, where do the light-independent reactions (Calvin cycle) take place, and what is their primary carbon input?
Glycolysis is the first metabolic pathway of cellular respiration. Which statement accurately describes its location and net energy yield per molecule of glucose?
Cyanide inhibits cytochrome c oxidase, a protein complex in the inner mitochondrial membrane. What is the immediate biochemical consequence of cyanide poisoning on cellular respiration?
Under anaerobic conditions, human skeletal muscle cells perform lactic acid fermentation. What is the primary biological purpose of fermentation in these cells?
Large bodies of water like Lake Erie moderate local coastal temperatures in winter and summer. Which chemical property of water is primarily responsible for this thermal buffering effect?
A competitive inhibitor reduces the rate of an enzyme-catalyzed reaction. How does a competitive inhibitor interact with the enzyme?
An experiment measures oxygen consumption in isolated mitochondria supplied with pyruvate. When DNP (2,4-dinitrophenol)—a chemical that makes the inner mitochondrial membrane leaky to protons—is added, oxygen consumption continues rapidly, but ATP production stops completely. What explains this phenomenon?
Question · Hard
A scientist labels carbon-14 in CO2 supplied to a plant performing photosynthesis. In which sequence of compounds will the radioactive carbon-14 label first appear during the Calvin cycle?
Respirometers are used to measure cellular respiration in germinating pea seeds at 10°C and 25°C. At 25°C, oxygen consumption per minute is significantly higher than at 10°C. What is the biochemical explanation for this observation?
Macromolecules are large organic polymers assembled from smaller repeating monomer units. Which monomer is matched with its correct biological macromolecule?
Chemical Basis Of Life
Which reaction combines monomers into polymers by removing a molecule of water?
Which category of macromolecules is hydrophobic (insoluble in water) and primarily functions in long-term energy storage, insulation, and membrane structure?
Starch and cellulose are both carbohydrates composed of repeating glucose monomers. Why can humans digest starch for energy but cannot digest cellulose?
Nucleotides are the structural monomers of DNA and RNA. What three components make up every standard nucleotide?
Saturated fatty acids differ structurally from unsaturated fatty acids. What structural feature distinguishes a saturated fatty acid?
The primary structure of a functional protein is defined as:
Phospholipids are described as amphipathic molecules. How does this property affect their arrangement in aqueous cellular environments?
A biochemist analyzes a purified biological sample and finds it contains carbon, hydrogen, oxygen, nitrogen, and sulfur atoms, but no phosphorus. Which class of macromolecules has been purified?
Sickle cell anemia is caused by a single point mutation in the beta-globin gene that substitutes valine (a nonpolar, hydrophobic amino acid) for glutamic acid (a polar, negatively charged amino acid) at position 6. How does this specific substitution affect hemoglobin function under low oxygen conditions?
According to the fluid mosaic model, what is the principal structural component forming the matrix of the plasma membrane?
Homeostasis And Transport
Which mode of transport moves small nonpolar molecules like oxygen (O2) and carbon dioxide (CO2) directly across the plasma membrane from high to low concentration without using energy or transport proteins?
Osmosis is specifically defined as the net movement of:
What happens to a red blood cell placed into a hypertonic salt solution?
Which cellular transport process requires metabolic energy in the form of ATP?
A plant cell is placed in a pure distilled water solution (hypotonic environment). Why does the plant cell become turgid rather than bursting like an animal cell?
Facilitated diffusion and active transport both utilize membrane carrier proteins. Which characteristic distinguishes active transport from facilitated diffusion?
A white blood cell (macrophage) engulfs a bacterial pathogen by wrapping its plasma membrane around the bacterium to form a phagosome. What is this specific transport process called?
Cholesterol molecules are embedded within the phospholipid bilayer of animal plasma membranes. What is the main homeostatic function of cholesterol in animal cell membranes?
Freshwater unicellular organism Paramecium lives in a environment where solute concentration is lower than inside its cytoplasm. How does Paramecium maintain water homeostasis?
Insulin is synthesized by pancreatic beta cells and released into the bloodstream to regulate blood glucose level homeostasis. Through which transport mechanism is insulin secreted from pancreatic cells?
An experimenter measures solute concentrations inside and outside a cell. The internal glucose concentration is 5 mM and external concentration is 50 mM. After adding a metabolic poison that halts ATP synthesis, glucose continues entering the cell. What type of transport is occurring?
Cellular U-tube experiments measure osmosis across a semipermeable membrane (impermeable to sucrose, permeable to water). Side A contains a 10% sucrose solution and Side B contains a 2% sucrose solution. At equilibrium, what will be observed?
In nerve cells, the resting membrane potential is maintained by the Na+/K+ ATPase pump. What ratio of ions does this pump exchange per hydrolysed ATP molecule, and in which directions?
Plant roots absorb nitrate ions (NO3-) from soil water where nitrate concentration is very low compared to inside root cells. Proton pumps first use ATP to establish a high H+ concentration outside the root cell membrane. Nitrate ions are then imported alongside H+ ions moving down their electrochemical gradient through a symporter protein. What form of transport imports nitrate ions?
Which major cell feature is present in eukaryotic cells but absent in all prokaryotic cells (such as bacteria)?
Cell Structure And Function
Which organelle contains its own circular DNA and double membrane, functioning as the primary site of aerobic ATP production in eukaryotic cells?
What is the primary function of ribosomes in both prokaryotic and eukaryotic cells?
Pancreatic acinar cells synthesize and secrete large quantities of digestive enzymes (proteins). Which organelles would you expect to be unusually abundant or well-developed in these specialized secretory cells?
Plant cells contain chloroplasts for photosynthesis and large central vacuoles. Which additional structural organelle surrounds the plant plasma membrane and provides rigidity and structural support?
Tay-Sachs disease is a genetic disorder caused by a defect in a hydrolytic enzyme that breaks down gangliosides (lipids) in brain cells. Which organelle fails to function properly in Tay-Sachs disease?
As a spherical cell increases in size, its volume grows faster than its surface area. How does this surface area-to-volume ratio constraint affect cell survival?
Loading more…