Membrane Permeability - AP Biology

Identify a type of passive transport.

Diffusion. Movement down concentration gradients without energy input.
What kind of molecules require facilitated diffusion?

Large or polar molecules. Size or polarity prevents direct passage through the lipid bilayer.
Why do ions require transport proteins to cross membranes?

Ions are charged and cannot pass the lipid bilayer. Hydrophobic lipid bilayer repels charged particles like ions.
What is the effect of hypotonic solution on animal cells?

Cells may swell and burst. Water enters cells causing them to expand beyond capacity.
What is the role of cholesterol in the cell membrane?

Maintain fluidity and stability of the membrane. Cholesterol modulates fluidity - reduces at high temps, increases at low temps.
Identify the effect of a hypertonic solution on animal cells.

Cells may shrink and crenate. Water leaves cells causing them to lose volume and wrinkle.
What is the effect of high cholesterol levels on membrane fluidity?

Decrease fluidity at high temperatures. Cholesterol prevents excessive fluidity by restricting lipid movement.
Identify an example of active transport.

Sodium-potassium pump. Uses ATP to maintain electrochemical gradients across membranes.
Identify the effect of isotonic solution on cell volume.

No change in cell volume. Equal solute concentrations inside and outside maintain equilibrium.
What is the primary function of receptor proteins in membranes?

Receive and transmit signals. Detect and respond to chemical signals from environment.
What is exocytosis?

Release of substances from a cell via vesicles. Vesicles fuse with membrane to release contents outside cell.
Which component forms the bilayer of cell membranes?

Phospholipids. Phospholipids arrange with hydrophobic tails inward, hydrophilic heads outward.
Identify the primary driving force of diffusion.

Concentration gradient. Difference in concentration provides the energy for molecular movement.
What is the function of membrane proteins?

Transport, signaling, attachment, and enzymatic activity. Membrane proteins perform diverse roles essential for cell function.
What type of transport requires energy from ATP?

Active transport. Moving substances against their concentration gradient requires energy input.
Which term describes the movement of water across a membrane?

Osmosis. Water moves down its concentration gradient across semipermeable membranes.
What is the effect of a hypertonic solution on plant cells?

Cells may plasmolyze. Water leaves cells causing them to shrink away from cell walls.
Describe how endocytosis occurs.

Cell membrane engulfs material forming a vesicle. Membrane surrounds and internalizes external material.
What is pinocytosis?

Cell drinking; uptake of liquid into vesicles. Nonspecific uptake of extracellular fluid and dissolved substances.
Which protein is involved in active transport?

Pump protein. These proteins use ATP to move substances against gradients.
Which molecules are typically involved in cell signaling?

Proteins and lipids. These molecules form signaling pathways for cellular communication.
What is the role of glycoproteins in the cell membrane?

Cell recognition and signaling. Carbohydrate-protein complexes function as cellular identification tags.
How do temperature changes affect phospholipid movement in membranes?

Higher temperatures increase movement. Kinetic energy increases with temperature, enhancing molecular motion.
What is facilitated diffusion?

Passive transport via specific proteins. Uses channel or carrier proteins but no energy input required.
What is the main role of transport proteins in cell membranes?

Facilitate movement of substances across membranes. Enable passage of substances that cannot cross lipid bilayer alone.
Identify a factor that increases membrane permeability.

Higher temperatures. Heat increases molecular motion and membrane fluidity.
How do carrier proteins function in facilitated diffusion?

Bind and transport specific molecules across membranes. Change shape to move specific molecules across the membrane.
What is the primary function of the cell membrane?

Regulate the movement of substances in and out of the cell. The membrane acts as a selective barrier controlling what enters and exits.
Identify an example of passive transport.

Osmosis. Water movement is a classic example of passive transport.
State the fluid mosaic model of the cell membrane.

Describes the membrane as a fluid structure with proteins embedded. Explains membrane structure as dynamic with mobile protein components.
Identify the direction of solute movement in passive transport.

From high to low concentration. Passive transport follows concentration gradients without energy.
What is the role of carbohydrates on the cell membrane?

Cell recognition and communication. Sugar chains on proteins and lipids serve as identification markers.
What is the main function of aquaporins?

Facilitate water transport across membranes. Channel proteins specifically designed for rapid water movement.
How does temperature affect membrane permeability?

Higher temperatures increase permeability. Heat increases molecular motion, making membranes more permeable.
Which type of transport uses vesicles to move substances?

Endocytosis and exocytosis. Membrane-bound vesicles transport large or bulk materials.
What is the function of anchor proteins in the membrane?

Stabilize cell structure by linking to cytoskeleton. Connect membrane to internal cellular framework for structural support.
What is the effect of unsaturated fatty acids on membrane fluidity?

Increase fluidity. Double bonds create kinks that prevent tight packing of lipids.
Which molecules easily pass through the cell membrane?

Small nonpolar molecules like O $_2$ and CO $_2$ . Their small size and nonpolar nature allow direct passage through lipids.
What distinguishes simple diffusion from facilitated diffusion?

Facilitated diffusion involves transport proteins. Simple diffusion occurs directly through lipids without proteins.
Identify the main components of the cell membrane.

Phospholipids, proteins, cholesterol, and carbohydrates. These four components work together to form the membrane structure.

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