Membrane Structure
O₂ crosses a membrane directly, while a charged ion cannot easily cross the hydrophobic interior. This fundamental property allows the membrane to regulate what enters and leaves.
What is selective permeability?
A cell is placed into a solution containing fewer nonpenetrating solutes than the cell. Water moves in this direction.
What is into the cell?
An enzyme speeds up a reaction by providing a pathway with a lower energy barrier. This barrier is called this.
What is activation energy?
A molecule loses electrons during a redox reaction. This process has occurred.
What is oxidation?
This 6-carbon molecule is split into two 3-carbon molecules during glycolysis.
What is glucose?
A solute moves from an area of high concentration to low concentration through a membrane protein, with no direct ATP use.
What is facilitated diffusion?
A cell contains 2 M nonpenetrating solute, while the surrounding solution contains 3 M nonpenetrating solute. The external solution is ___ to the cell, and water moves ___.
What are hypertonic; out of the cell?
An enzyme can dramatically increase the reaction rate but does not change the overall free-energy difference between reactants and products.
What is an enzyme catalyst?
NAD⁺ accepts electrons and H⁺ during cellular respiration and becomes this reduced electron carrier.
What is NADH?
Glycolysis converts one glucose molecule into two molecules of this 3-carbon product.
What is pyruvate?
A membrane protein binds a specific solute, changes its conformation, and releases the solute on the opposite side of the membrane.
What is carrier-mediated transport?
Two solutions have the same amount of solute, but one solute can cross the membrane and the other cannot. The solute that matters when determining tonicity is called this.
What is the nonpenetrating solute?
A reaction has a negative ΔG value but proceeds very slowly. This is possible because ΔG determines thermodynamic favorability, whereas this determines how difficult it is for the reaction to get started.
What is activation energy?
During oxidative phosphorylation, electron-transfer energy is used to establish a high concentration of H⁺ in this mitochondrial compartment.
What is the intermembrane space?
During pyruvate oxidation, each pyruvate loses one carbon as this molecule before its remaining 2-carbon acetyl group enters the citric acid cycle.
What is CO₂?
A membrane protein is embedded in the bilayer and creates a hydrophilic passageway through which ions can move. Unlike a carrier, it does not need to bind and flip the solute across the membrane.
What is a channel protein?
A plant cell enters a hypotonic solution. Water enters, but the cell normally does not burst because the cell wall allows pressure to build against it. This pressure is called this.
What is turgor pressure?
An inhibitor resembles the normal substrate and competes for the enzyme's active site. Increasing substrate concentration can reduce the inhibitor's effect.
What is competitive inhibition?
H⁺ flows through this enzyme from the intermembrane space toward the mitochondrial matrix, and that flow drives ATP production.
What is ATP synthase?
NADH and FADH₂ deliver high-energy electrons to this system, where electron transfer ultimately leads to the formation of an H⁺ gradient used for ATP production.
What is the electron transport chain?
A transporter moves glucose against its concentration gradient by coupling glucose movement to Na⁺ moving down a gradient established by another membrane protein. Identify both the transport mechanism and the transporter arrangement.
What are secondary active transport and symport?
A plant cell is moved into a strongly hypertonic solution. Water leaves the cell, causing the plasma membrane to pull away from the cell wall.
What is plasmolysis?
An amino acid accumulates in a cell and binds to an enzyme involved in the pathway that produces more isoleucine. The binding occurs at a site other than the active site and shifts the enzyme toward a low-affinity state.
What is allosteric feedback inhibition?
A mutation prevents ATP synthase from using the H⁺ gradient. The ETC can still transfer electrons, but ATP production by oxidative phosphorylation is severely disrupted. Identify the failed mechanism.
What is ATP synthesis in chemiosmosis?
A cell has no O₂, so NADH builds up. How does fermentation help?
What is regenerating NAD⁺ from NADH so glycolysis can continue?