Osmosis & Tonicity
What substance moves during osmosis?
Water
Oxygen moves directly through the phospholipid bilayer from high → low concentration. Name the process.
Simple diffusion
What structure makes up the main barrier of the cell membrane?
Phospholipid bilayer
What type of transport was demonstrated by water moving across the egg's membrane?
Osmosis
A cell surrounds and brings a large particle INTO the cell using a vesicle. Name the process.
Endocytosis
A cell has equal effective solute concentrations inside and outside. What type of solution surrounds it?
Isotonic
A molecule moves high → low through a channel protein without using ATP. Name the process.
Facilitated diffusion
Which part of a phospholipid interacts with water: the head or the tails?
Hydrophilic head
An egg gains mass after sitting in a solution. Did water move primarily INTO or OUT OF the egg?
Into the egg
A vesicle fuses with the cell membrane and releases material OUTSIDE the cell. Name the process.
Exocytosis
There is LESS nonpenetrating solute outside a cell than inside. Is the outside solution hypertonic, hypotonic, or isotonic?
Hypotonic
Water moves across a selectively permeable membrane. What process is occurring?
Osmosis
Are the fatty-acid tails hydrophilic or hydrophobic?
Hydrophobic
An egg loses mass after sitting in a solution. Was the surrounding solution relatively hypertonic, hypotonic, or isotonic to the egg?
Hypertonic
Which process—endocytosis or exocytosis—would a cell use to engulf a large particle?
Endocytosis
There is MORE nonpenetrating solute outside a cell than inside. Predict the net movement of water.
Out of the cell
A cell uses ATP to move ions from an area of low concentration → high concentration. Name the process.
Active transport
Why are phospholipid tails positioned toward the inside of the bilayer?
They are hydrophobic/nonpolar and avoid water.
An egg's mass decreases from 72 g to 65 g. Explain what happened to the water.
There was net movement of water out of the egg by osmosis.
Which process—endocytosis or exocytosis—would a cell use to release packaged material?
Exocytosis
A cell is placed in a hypertonic solution. Identify the direction of net water movement and predict what happens to the cell's size.
Water moves out; the cell shrinks.
A molecule moves through a membrane protein from high → low concentration. Explain why this is considered passive transport.
It moves down its concentration gradient and does not require ATP.
Explain how the arrangement of phospholipids helps the membrane act as a barrier.
The hydrophobic interior restricts many charged/polar substances from crossing freely.
An egg loses mass after being placed in a solution. Explain the result using osmosis AND tonicity.
The surrounding solution was hypertonic relative to the egg, causing net water movement out of the egg across its membrane by osmosis.
A cell needs to move a substance from LOW → HIGH concentration. What transport process should it use, and what molecule provides the necessary energy?
Active transport; ATP