Biology Test 3

What are the four main components of the cell membrane?

Phospholipids, proteins, cholesterol, and carbohydrates.

What is the function of phospholipids?

Form the bilayer that separates the inside of the cell from its surroundings.

Example: What do phospholipids form?

A double layer called the phospholipid bilayer.

What is the function of membrane proteins?

Help transport substances across the membrane and receive signals.

Example: What can membrane proteins do?

Transport substances through channels or carriers.

What is the function of cholesterol?

Maintains membrane stability and controls flexibility and fluidity.

What is the function of carbohydrates in the membrane?

Help cells recognize each other and communicate.

What are glycoproteins?

Proteins with attached carbohydrates that help with cell recognition and communication.

Example: What is a glycoprotein made of?

A protein with an attached carbohydrate chain.

What are glycolipids?

Lipids with attached carbohydrates that help cells recognize and interact with each other.

Example: What is a glycolipid made of?

A lipid with an attached carbohydrate chain.

What are the two parts of a phospholipid?

A hydrophilic phosphate head and two hydrophobic fatty acid tails.

What does hydrophilic mean?

Water-loving; attracted to water.

What does hydrophobic mean?

Water-fearing; repelled by water.

How are phospholipids arranged in the bilayer?

Heads face watery environments; tails face inward toward each other.

What is diffusion?

Movement of molecules from high concentration to low concentration.

What happens when the concentration gradient increases?

Diffusion happens faster because there is a greater difference in concentration.

How does molecule mass affect diffusion?

Smaller, lighter molecules generally diffuse faster than larger, heavier molecules.

How does temperature affect diffusion?

Higher temperatures make molecules move faster, increasing diffusion rates.

How does solvent density affect diffusion?

Higher cytoplasm density slows diffusion. Dehydration can increase density.

How does solubility affect diffusion?

More nonpolar, lipid-soluble substances diffuse through the membrane faster.

How does surface area affect diffusion?

Greater surface area increases diffusion rates.

How does distance traveled affect diffusion?

Greater distance slows diffusion. It also helps determine the upper limit of cell size.

How does pressure affect diffusion?

Pressure can force solutions through membranes, increasing movement.

Example: How does blood pressure affect kidney cells?

Blood pressure helps force solutions through membranes, speeding up movement.

What is osmosis?

Movement of water across a selectively permeable membrane from high water concentration to low water concentration.

Why does water move during osmosis?

To balance water concentration; water moves toward the side with higher solute concentration.

What is passive transport?

Movement of substances from high to low concentration without requiring ATP.

What is active transport?

Movement of substances that requires energy, usually against their concentration gradient.

Example: What is an example of passive transport?

Simple diffusion, facilitated diffusion, and osmosis.

What are the three types of passive transport?

Simple diffusion, facilitated diffusion, and osmosis.

Does passive transport require ATP?

No, passive transport does not require energy.

Does active transport require energy?

Yes, active transport requires energy, usually ATP.

What is ATP?

Adenosine triphosphate; the main energy-carrying molecule in cells.

How do cells get energy for active transport?

From ATP, which is produced mainly through cellular respiration.

What is facilitated diffusion?

Movement from high to low concentration through membrane proteins.

Does facilitated diffusion require ATP?

No, it is passive transport and does not require ATP.

What is simple diffusion?

Movement directly through the membrane from high to low concentration.

What is a concentration gradient?

A difference in the concentration of a substance between two areas.

What is an electrical gradient?

A difference in electrical charge between two areas.

What is an electrochemical gradient?

The combination of a concentration gradient and an electrical gradient.

Which direction do positive ions move electrically?

Toward areas with a more negative charge.

What is a hypertonic solution?

A solution with a higher solute concentration than the cell.

What happens to a cell in a hypertonic solution?

Water leaves the cell, causing it to shrink.

Example: What happens to a cell's mass in a hypertonic solution?

Its mass decreases because water leaves the cell.

What is an isotonic solution?

A solution with the same solute concentration as the cell.

What happens to a cell in an isotonic solution?

It stays about the same size because water enters and leaves equally.

Example: What happens to a cell's mass in an isotonic solution?

Its mass stays about the same.

What is a hypotonic solution?

A solution with a lower solute concentration than the cell.

What happens to a cell in a hypotonic solution?

Water enters the cell, causing it to swell.

Example: What happens to a cell's mass in a hypotonic solution?

Its mass increases because water enters the cell.

What may happen to an animal cell in a very hypotonic solution?

It may swell and burst.

What is the difference between hypertonic and hypotonic?

Hypertonic: water leaves. Hypotonic: water enters.

What is the difference between isotonic and hypotonic?

Isotonic: no net water movement. Hypotonic: water enters the cell.

What is endocytosis?

The process of bringing materials into a cell using vesicles.

Does endocytosis require energy?

Yes, endocytosis requires ATP.

How does endocytosis work?

The cell membrane folds inward and forms a vesicle around material.

What is exocytosis?

The process of releasing materials outside the cell using vesicles.

Does exocytosis require energy?

Yes, exocytosis requires ATP.

How does exocytosis work?

A vesicle fuses with the cell membrane and releases its contents outside.

What is pinocytosis?

Cell drinking; taking in liquids and dissolved substances.

Example: What does pinocytosis take into the cell?

Liquids and dissolved substances in small vesicles.

What is phagocytosis?

Cell eating; engulfing large solid particles.

Example: What can a cell engulf through phagocytosis?

Bacteria or other large particles.

What is the difference between pinocytosis and phagocytosis?

Pinocytosis takes in liquids; phagocytosis takes in large solid particles.

What is primary active transport?

Transport that uses ATP directly to move substances against their gradient.

Example: What is the sodium-potassium pump?

A protein pump that uses ATP to move sodium out and potassium into the cell.

How many sodium ions does the sodium-potassium pump move out?

Three sodium ions (3 Na+).

How many potassium ions does the sodium-potassium pump move in?

Two potassium ions (2 K+).

What is secondary active transport?

Transport that uses energy stored in an ion gradient.

Example: What does the sodium-glucose cotransporter do?

Uses sodium moving down its gradient to bring glucose into the cell.

What is a uniporter?

A transport protein that moves one type of substance in one direction.

Example: What is a uniporter?

The GLUT glucose transporter.

What is a symporter?

A transport protein that moves two or more substances in the same direction.

Example: What is a symporter?

The sodium-glucose cotransporter.

What is an antiporter?

A transport protein that moves two substances in opposite directions.

Example: What is an antiporter?

The sodium-potassium pump.

What is the difference between a uniporter and a symporter?

Uniporter moves one substance; symporter moves multiple substances in the same direction.

What is the difference between a symporter and an antiporter?

Symporter moves substances together; antiporter moves them in opposite directions.

What is the difference between primary and secondary active transport?

Primary uses ATP directly; secondary uses energy stored in an ion gradient.

What type of transport moves substances against their concentration gradient?

Active transport.

What type of transport moves substances down their concentration gradient?

Passive transport.

What is a selectively permeable membrane?

A membrane that allows certain substances to pass through but blocks others.

What is a vesicle?

A small membrane-bound sac that transports or stores materials in a cell.