Homeostasis
What term describes maintaining relatively stable internal conditions?
Homeostasis
Particles spread from higher to lower concentration. Name the process.
Diffusion
A cell has 10% solute inside and 10% outside. Classify the outside solution. How is the water moving?
Isotonic, water is moving in and out of the cell at the same time.
Which kind of transport uses cellular energy to move substances against a gradient?
Active Transport
Where does the substrate bind to the enzyme?
Active Site
A runner overheats. What response helps restore normal body temperature?
Sweating, which releases heat.
Oxygen is at 70 units on the left and 20 on the right. What direction will the particles move?
Left to Right
A cell has 8% solute inside and 3% outside. Classify the solution and predict net water movement.
Hypotonic; water enters the cell.
A substance moves from 25% to 5% without ATP. What type of transport is this?
Passive Trasnport
What energy barrier do enzymes lower to speed reactions? Double Jeopardy 2x
Activation Energy
Blood glucose rises after a meal and insulin helps lower it. Identify the feedback mechanism.
Negative feedback
At equilibrium, do particles stop moving? Explain.
No. They move randomly in both directions with no net movement.
A cell has 5% solute inside and 18% outside. Classify the solution and predict net water movement.
Hypertonic; water leaves the cell.
Which kinds of molecules can usually cross directly through the phospholipid bilayer without a transport protein?
Small, nonpolar molecules such as oxygen and carbon dioxide.
An enzyme works best at 37°C but poorly at 85°C. Explain.
Heat can denature an enzyme changing the shape, so the substrate is unable to bind.
Why is it incorrect to say that homeostasis means everything inside an organism stays exactly the same?
Homeostasis maintains internal conditions within a healthy range. Small changes occur as the body responds to its environment.
CO₂ is 12% inside a cell and 4% outside. Assuming it crosses freely, what happens?
It diffuses out of the cell.
A marine plant is moved from saltwater into freshwater. What happens to its central vacuole, and why?
The central vacuole swells as water enters by osmosis. Freshwater is hypotonic relative to the cell, increasing turgor pressure.
Why do charged ions such as sodium (Na⁺) have difficulty passing directly through the phospholipid bilayer?
The hydrophobic interior of the bilayer blocks charged particles, so ions need transport proteins.
Two test tubes contain the same substrate and equal amounts of an enzyme. Tube A produces a large amount of product, but Tube B produces none. Adding more substrate to Tube B does not help, but adding fresh enzyme causes the reaction to begin. What does this suggest happened to the original enzyme in Tube B?
The original enzyme was likely denatured or otherwise inactive. Its active site could no longer function properly, so adding more substrate did not help. Fresh enzyme restored the reaction.
A phospholipid bilayer suddenly is unable to do its function. Explain how this could disrupt homeostasis.
The cell could lose essential substances or allow too much of others to enter, disrupting internal balance and normal cell functions.
Glucose moves inward through a membrane protein from high to low concentration without ATP. Name the process. Double Jeopardy 2x
Facilitated Diffusion
A plant cell is placed in a concentrated salt solution. Under a microscope, the cell membrane pulls away from the cell wall. A student says, “The cell wall must have shrunk.” Identify the process and explain why the student’s conclusion is incorrect.
The outside solution is hypertonic, so water leaves the cell by osmosis. The central vacuole shrinks and the membrane pulls away from the rigid cell wall. The wall itself does not shrink significantly.
Oxygen enters a cell directly, glucose enters through a protein down its gradient and sodium ions are pumped out against their gradient. Identify all three transport methods and explain why they differ.
Oxygen uses simple diffusion because it is small and nonpolar. Glucose uses facilitated diffusion because it is polar and needs a transport protein. Sodium uses active transport because it is charged and moving against its concentration gradient.
Why can one enzyme catalyze many reactions? DOUBLE JEOPARDY
It is not consumed during the reaction.