34 Questions
What is the main function of the plasma membrane in cells?
Regulating the cell's molecular traffic
Which type of molecules can pass through the lipid bilayer rapidly?
Hydrophobic (nonpolar) molecules
What do channel proteins called aquaporins facilitate the passage of?
Water
How do carrier proteins assist in transporting molecules across the membrane?
By binding to molecules and changing shape to shuttle them
What type of transport moves substances against their concentration gradients?
Active transport
What is dynamic equilibrium in terms of molecule diffusion across a membrane?
As many molecules cross in one direction as in the other
Which statement is true about facilitated diffusion?
Involves movement down the concentration gradient
In diffusion, what is the tendency for molecules to do?
Spread out evenly into available space
What triggers the change in shape of carrier proteins in facilitated diffusion?
Binding and release of transport molecule
Which process allows cells to maintain concentration gradients different from their surroundings?
Active transport
What is the most abundant lipid in the plasma membrane?
Phospholipids
What is usually the form of energy required for active transport?
ATP energy
Which term describes a membrane as a fluid structure with a 'mosaic' of proteins embedded in it?
Fluid mosaic model
The sodium-potassium pump is an example of which type of transport system?
Active transport system
What type of molecules are phospholipids?
Amphipathic
Which process uses energy to move solutes against their gradients?
Active transport
What is the main function of exocytosis and endocytosis across the plasma membrane?
Bulk transport
What does lateral movement of proteins refer to in cell membranes?
Proteins moving side to side within the membrane
What happens to a cell in a hypertonic solution?
The cell loses water
How does an isotonic solution affect a cell?
The solute concentration is the same as that inside the cell
What is osmoregulation?
The control of solute concentrations and water balance
How do plant cells respond in a hypertonic environment?
They lose water and wilt
What happens to a cell in a hypotonic solution?
The cell swells until the wall opposes uptake
How does a plant cell respond in an isotonic environment?
There is no net movement of water
What is the main driving force behind cotransport?
Active transport
Which process involves the cell taking in macromolecules by forming vesicles from the plasma membrane?
Receptor-mediated endocytosis
What type of endocytosis is known as 'cellular eating'?
Phagocytosis
What do plants commonly use to drive active transport of nutrients into the cell?
Hydrogen ion gradient
Which type of molecules cross the membrane via vesicles in bulk transport?
Polysaccharides and proteins
In which process do transport vesicles migrate to the membrane, fuse with it, and release their contents to the outside of the cell?
Exocytosis
What is the main function of receptor-mediated endocytosis in human cells?
Take in cholesterol for membrane synthesis
How does pinocytosis differ from phagocytosis?
Pinocytosis is 'cellular drinking', while phagocytosis is 'cellular eating'.
What happens to low-density lipoproteins (LDLs) after binding to LDL receptors on human cells?
They enter cells by endocytosis.
What kind of transport requires energy to move large molecules across the plasma membrane?
Active transport
Learn about the water balance of cells and the concept of tonicity. Explore the effects of isotonic, hypertonic, and hypotonic solutions on cell water movement.
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