Cell Biology: Diffusion Process

Questions and Answers

It can only occur for small molecules.

It involves random motion of molecules. (correct)

It moves molecules from low to high concentration.

It requires energy input from the cell.

Amino acids

Glucose

Oxygen (correct)

Proteins

Osmosis cannot occur across a semipermeable membrane.

Osmosis involves the movement of solute molecules.

Osmosis specifically involves the movement of water. (correct)

Osmosis requires energy to occur.

They selectively allow larger molecules to pass through. Signup and view all the answers

To assist in the movement of water across cell membranes. Signup and view all the answers

It moves substances from low to high concentration. Signup and view all the answers

It stabilizes the cell's internal environment. Signup and view all the answers

The membrane regulates the passage of specific molecules. Signup and view all the answers

Study Notes

Molecules move from high concentration areas to low concentration areas without energy input.
Essential for gas exchange, nutrient transport, and waste removal in cells.
Molecules capable of simple diffusion include water, oxygen, carbon dioxide, ethanol, and urea.
These molecules pass through the cell membrane along the concentration gradient.

Defined as the movement of water molecules across a semipermeable membrane from lower solute concentration to higher solute concentration.
Critical for maintaining cell hydration and regulating osmotic pressure.
Affects cell volume by altering water content.

Requires energy to move ions or molecules against their concentration gradient.
Vital for functions such as nerve signaling, muscle contraction, and nutrient uptake.

Specific molecules move across the cell membrane with the help of transport proteins.
Used for larger molecules that cannot easily penetrate the lipid bilayer.
Maintains selective permeability of the cell membrane for controlled molecule movement.
Protein channels facilitate rapid transport and exhibit selectivity based on size.

Aquaporin proteins discovered by Peter Agre in 1992, awarded the Nobel Prize in Chemistry in 2003.
These proteins significantly enhance the transport of water across cell membranes.