Enzymes
This molecule binds to an enzyme's active site and is changed by the reaction.
What is a substrate?
This organelle modifies, sorts, and packages proteins for secretion.
What is the Golgi apparatus?
This model describes the plasma membrane as a fluid phospholipid bilayer with proteins that move laterally.
What is the fluid mosaic model?
The diffusion of water across a selectively permeable membrane.
What is osmosis?
Above the optimum temperature, enzyme activity drops sharply because the enzyme's shape changes and the substrate no longer fits. What is this process called?
What is denaturation?
Name two pieces of evidence that mitochondria evolved from free-living bacteria.
Own circular DNA, own ribosomes similar to bacterial ribosomes, double membrane, divides by binary fission (any two).
Contrast facilitated diffusion and active transport in terms of concentration gradient direction and energy use.
Facilitated diffusion: down the gradient, no ATP, via a protein; Active transport: against the gradient, requires ATP.
A plant cell with water potential -8 bars is placed in pure water (0 bars). Which way does water move, and what happens to pressure potential?
Water moves into the cell; pressure potential (turgor) rises.
In a metabolic pathway, the end product binds to the first enzyme and slows its own production. Name this type of regulation and state one advantage of it.
What is feedback inhibition? It prevents overproduction and waste / maintains balance.
A liver cell has abundant smooth ER, while a pancreatic cell has abundant rough ER. Explain what each cell is specialized for.
Liver smooth ER: lipid synthesis and detoxification; pancreatic rough ER: making and secreting proteins (digestive enzymes).
The sodium-potassium pump moves 3 Na+ out and 2 K+ in per ATP. Explain why it is called electrogenic, and predict what happens if ATP production is blocked.
It creates a net charge difference (membrane potential) because more positive ions leave than enter; without ATP the pump stops and the Na+/K+ gradients run down (Na+ builds up inside).
Calculate the solute potential of a 0.3 M sucrose solution at 27°C. Use Ψs = -iCRT, R = 0.0831. Show your setup.
Ψs = -(1)(0.3)(0.0831)(300) = -7.48 bars.
After an enzyme reaction slows, adding more substrate speeds it up again, but not to the original rate. This factor is now limiting the reaction.
What is the amount of enzyme (enzyme concentration)?
A cube-shaped cell with side 4 cm has a surface area of 96 cm² and a volume of 64 cm³. Its surface-area-to-volume ratio is this.
What is 1.5 per cm?
In mice given glucose, blood glucose rises more slowly when this gut transporter is blocked, showing that glucose uptake depends in part on it.
What is the sodium-glucose cotransporter?
Calculate the solute potential of a 0.5 M glucose solution at 25°C. Use Ψs = -iCRT, R = 0.0831. Show your setup.
What is -12.38 bars? Ψs = -(1)(0.5)(0.0831)(298) = -12.38 bars.
Of two versions of the same enzyme, one from an animal living at 10°C and one from an animal living at 40°C, this version keeps working at 40°C, because enzymes are adapted to the conditions where the organism lives.
What is the 40°C version?
A 1 cm cube has a surface-area-to-volume ratio of 6.0, and a 3 cm cube has a ratio of 2.0. This cube's center receives nutrients faster.
What is the 1 cm cube?
This property of the phospholipid bilayer's interior blocks charged and large polar molecules, while small nonpolar molecules can pass, contributing to selective permeability.
What is hydrophobicity (the hydrophobic interior)?
A cell with solute potential -14 bars and pressure potential 0 bars is placed in a solution with water potential -8 bars. Water moves into the cell. At equilibrium, the cell's pressure potential is this.
What is 6 bars? At equilibrium the cell's water potential equals -8 bars, so pressure potential = -8 - (-14) = 6 bars.