Diffusion and osmosis

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Questions and Answers

What is the direction of net movement of molecules in osmosis?

From a region of low solute concentration to a region of high solute concentration

Along a concentration gradient

From a region of high solute concentration to a region of low solute concentration (correct)

Against a concentration gradient

What is the primary reason for the movement of molecules in osmosis?

Kinetic energy of random motion (correct)

Electrostatic attraction

Difference in pressure

Difference in temperature

What determines the direction of diffusion in osmosis?

Temperature difference

Relative solute concentrations (correct)

Pressure difference

Electrostatic charge

What is tonicity?

The relative solute concentrations of two solutions Signup and view all the answers

What is a hypertonic solution?

A solution with a high solute concentration Signup and view all the answers

What happens to the free water concentration when the solute concentration increases?

It decreases Signup and view all the answers

What is homeostasis?

A self-regulatory process by which biological systems tend to maintain stability Signup and view all the answers

Why is movement regulated in cellular membranes?

Because cellular membranes are selectively permeable Signup and view all the answers

What is the purpose of the dialysis bag in the lab?

To act as a selectively permeable membrane Signup and view all the answers

Why do NH3 molecules diffuse faster than HCl molecules?

Because they are lighter Signup and view all the answers

What is the main function of aquaporins?

To allow water to pass through the membrane Signup and view all the answers

How do larger molecules, such as carbohydrates, pass through the membrane?

By transport proteins via active or passive transport Signup and view all the answers

What happens when gaseous NH3 and HCl collide?

They form a white precipitate Signup and view all the answers

Why do plant cells not burst in a hypotonic solution?

Because they have a cell wall Signup and view all the answers

What is the difference between active and passive transport?

Active transport requires energy, while passive transport does not Signup and view all the answers

What is the function of the cell wall in plant cells?

To provide structural support Signup and view all the answers

What is diffusion?

The movement of molecules with a concentration gradient Signup and view all the answers

What is osmosis?

The movement of water through a phospholipid bilayer Signup and view all the answers

What happens to a protoplast in a hypotonic solution?

It expands Signup and view all the answers

Why is it necessary for cells to move materials through plasma membranes?

To maintain homeostasis Signup and view all the answers

What is the purpose of the fume cupboard or fume hood?

To provide a safe environment for gas diffusion Signup and view all the answers

What is the difference between a plant cell and a protoplast?

The presence of a cell wall Signup and view all the answers

What is the characteristic of a hypertonic solution?

More free water out of the cell than in the cell Signup and view all the answers

What happens to an animal cell in a hypertonic solution?

It becomes shriveled or crenated Signup and view all the answers

What is an example of an isotonic solution?

Normal saline Signup and view all the answers

What is the effect of temperature on the rate of diffusion?

It increases the rate of diffusion Signup and view all the answers

What is the characteristic of a hypotonic solution?

More free water in the cell than out of the cell Signup and view all the answers

What happens to a plant cell in a hypertonic solution?

It becomes plasmolyzed Signup and view all the answers

What is the effect of mass of particle on the rate of diffusion?

It decreases the rate of diffusion Signup and view all the answers

What is the characteristic of an isotonic solution?

Equal free water and solutes in and out of the cell Signup and view all the answers

Study Notes

Homeostasis and Cell Membranes

Homeostasis is a self-regulatory process that maintains stability in biological systems while adjusting to optimal conditions for survival.
Cells maintain homeostasis by moving materials through plasma membranes into and out of the cytoplasm.
Cellular membranes are selectively permeable, consisting of phospholipid bilayers with embedded proteins.
Phospholipid fatty acids are hydrophobic, limiting the movement of water.

Water and Molecule Transport

Water can pass through the membrane by: • Freely by osmosis (small amount) • Selectively by aquaporins (large amount)
Molecules can pass through the membrane by: • Most ions moving through protein channels • Larger molecules carried by transport proteins via active or passive transport

Active and Passive Transport

Active transport requires transport proteins, energy output, and moves against a concentration gradient.
Passive transport does not require energy and moves along the concentration gradient, including diffusion and osmosis.