Membrane Strcuture
What is the main structural component of the plasma membrane?
Phospholipids
What is the movement of molecules from an area of high concentration to an area of low concentration called?
Diffusion
What is the diffusion of water across a selectively permeable membrane called?
Osmosis
What type of membrane protein allows specific ions or molecules to cross the membrane through a hydrophilic passageway?
Channel protein
O₂ moves directly through the phospholipid bilayer from an area of high concentration to low concentration. What type of transport is this?
Simple diffusion
Which part of the phospholipid interacts with water, and what part avoids water?
hydrophilic phosphate head interacts with water
hydrophobic fatty acid tails avoid water
A molecule moves across the plasma membrane from an area of high concentration to an area of low concentration without using ATP. What general type of transport is occurring?
Passive transport
A cell is placed into a hypertonic solution. Which direction will water move?
Out of the cell
What type of membrane protein changes shape to move a substance across the membrane?
Carrier protein
A protein binds glucose on one side of the membrane, changes shape, and releases glucose on the other side. What type of protein is this?
Carrier protein
Why do phospholipids spontaneously arrange themselves into a bilayer in water?
Hydrophilic heads interact with water while hydrophobic tails avoid water.
What type of transport moves substances against their concentration gradient and requires energy?
Active transport
A cell is placed into a solution that has a higher solute concentration than the cell. Is the solution hypertonic, hypotonic, or isotonic?
Hypertonic
What type of membrane protein can receive a chemical signal from outside the cell?
Receptor protein / Glycoprotein
A cell has a high concentration of Na⁺ outside and a low concentration inside. Na⁺ moves into the cell through a membrane protein without ATP. What type of transport is occurring?
Facilitated diffusion.
Na⁺ is moving down its electrochemical gradient through a membrane protein without direct ATP use.
The plasma membrane is described as "selectively permeable." What does this mean?
It allows some substances to cross more easily than others.
Glucose moves across a membrane through a membrane protein without directly using ATP. What type of transport is this?
Facilitated diffusion
A red blood cell is placed into a hypotonic solution. What will happen to water movement and the cell?
Water will move into the cell, causing it to swell and potentially lyse.
What is the major difference between a channel protein and a carrier protein?
A channel provides a passageway through the membrane, while a carrier binds a substance and changes shape to move it across.
A molecule is too large and polar to cross the phospholipid bilayer directly. It moves through a membrane protein from high concentration to low concentration. Identify the transport mechanism and explain whether ATP is required.
Facilitated diffusion; ATP is not required.
A membrane becomes less fluid because its phospholipid tails are more tightly packed. What characterisctic of the tails could cause this?
More saturated fatty acid-tails
A cell uses ATP to move Na+ from an area of lower concentration to an area of higher concentration. Is this passive or active transport, and why?
Active transport because energy is being used to love substances against the concentration gradient.
A cell contains 10% solute. It is placed in a solution containing 2% solute. Predict the direction of water movement.
Water moves into the cell because the surrounding solution has a lower solute concentration.
What is the primary function of an ion pump?
To actively transport ions across the membrane using energy.
A cell is placed in a solution containing a higher concentration of solutes than the cell. Predict the direction of water movement, the tonicity of the solution, what happens to the cell, and whether ATP is required.
Water moves out of the cell → solution is hypertonic → cell shrinks → no ATP is required because osmosis is passive transport.