STEM Biology 11/12: Cell Transport Mechanisms

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Questions and Answers

What is the primary function of phagocytosis in cellular processes?

Facilitating fluid intake into the cell

Transporting sodium and potassium ions

Bringing solid particles into the cell (correct)

Excreting waste products from the cell

Which process requires energy (ATP) for the transport of substances across the cell membrane?

Facilitated diffusion

Simple diffusion

Active transport (correct)

Osmosis

What distinguishes exocytosis from endocytosis?

Endocytosis uses energy while exocytosis does not

Exocytosis releases materials from the cell (correct)

Exocytosis involves the intake of fluids

Endocytosis is a passive process

What is the main difference between phagocytosis and pinocytosis?

Phagocytosis involves solid intake, while pinocytosis involves fluid intake Signup and view all the answers

Which component is often involved in active transport mechanisms?

Carrier proteins Signup and view all the answers

What is the primary driver of diffusion?

Concentration gradient Signup and view all the answers

Which statement about facilitated diffusion is true?

It involves the movement through specific channels. Signup and view all the answers

What condition is described when the concentration of molecules is uniform throughout a solution?

Equilibrium Signup and view all the answers

In osmosis, water moves toward which type of solution?

High solute concentration Signup and view all the answers

What separates the two solutions in osmosis?

A selectively-permeable membrane Signup and view all the answers

What role do protein channels play in facilitated diffusion?

They assist in moving specific molecules. Signup and view all the answers

Which process does NOT require energy?

Both A and C Signup and view all the answers

What is osmotic pressure primarily caused by?

Hydrostatic pressure due to water movement Signup and view all the answers

What characterizes a concentrated solution?

Has a higher percentage of solute Signup and view all the answers

What happens to a red blood cell (RBC) placed in a hypertonic solution?

It shrinks and may undergo plasmolysis Signup and view all the answers

Which statement correctly describes osmotic pressure?

It increases with a higher concentration of solute Signup and view all the answers

In which environment is a plant cell considered turgid?

In a hypotonic environment Signup and view all the answers

What movement occurs when a dilute solution is introduced to a cell in a concentrated solution?

Water moves into the cell Signup and view all the answers

What is the result of osmotic pressure acting on the side of a membrane with a higher solute concentration?

Shift of water towards that side Signup and view all the answers

Which of the following best describes the effect of osmosis in living organisms?

It is a consistent process vital for water balance Signup and view all the answers

What occurs when the membrane of a cell does not permit the passage of a solute?

Only water can pass freely across the membrane Signup and view all the answers

Which type of molecule can pass through the plasma membrane without any assistance?

Small non-polar molecules Signup and view all the answers

What is the primary factor that affects the rate of diffusion?

Concentration gradient of the particles Signup and view all the answers

Which statement best describes osmosis?

Movement of water through a semi-permeable membrane Signup and view all the answers

What characterizes a semi-permeable membrane?

Permits only selected molecules to pass Signup and view all the answers

Which statement about macromolecule transport is true?

Macromolecules require energy for transport irrespective of concentration gradients. Signup and view all the answers

Which transport mechanism requires the use of energy?

Active transport Signup and view all the answers

What role does temperature play in the rate of diffusion?

Higher temperatures increase the rate of diffusion. Signup and view all the answers

What causes the movement of oxygen from alveoli to blood in lung capillaries?

Concentration of oxygen in alveoli being higher Signup and view all the answers

How does the size of a molecule affect its ability to diffuse across the plasma membrane?

Smaller molecules can cross the membrane more freely. Signup and view all the answers

Which processes are classified as passive transport mechanisms?

Facilitated diffusion and osmosis Signup and view all the answers

What defines active transport mechanisms?

They require the input of energy (ATP). Signup and view all the answers

What does Brownian motion refer to in the context of diffusion?

Random movement of molecules caused by heat energy. Signup and view all the answers

What is the primary difference between exocytosis and endocytosis?

Exocytosis is the expulsion of materials, while endocytosis is the intake. Signup and view all the answers

Why do ions and charged molecules have difficulty crossing the plasma membrane?

They cannot interact with the hydrophobic portion of the bilayer. Signup and view all the answers

In a solution, which component is typically considered the solute?

The solid part of the solution. Signup and view all the answers

What concentration gradient do molecules move along during diffusion?

From higher to lower concentration. Signup and view all the answers

Study Notes

Plasma Membrane Permeability

Plasma membrane is differentially permeable, allowing some molecules to pass while restricting others.
Lipid-soluble molecules like alcohol diffuse easily due to the lipid structure of the membrane.
Gases, such as oxygen, diffuse through the lipid bilayer, influenced by their concentration gradient.

Types of Transport Mechanisms

Passive mechanisms (require no ATP) include:
- Simple diffusion: Molecules move from areas of higher to lower concentration.
- Facilitated diffusion: Requires specific protein channels to aid movement of larger molecules like glucose, also occurs down a concentration gradient.
- Osmosis: Diffusion of water across a selectively permeable membrane, moving from areas of low solute concentration to high.
Active mechanisms (require ATP) include:
- Exocytosis: Process of expelling materials from a cell.
- Endocytosis: Process of engulfing materials into a cell; includes phagocytosis (cell eating) and pinocytosis (cell drinking).

Factors Influencing Diffusion

Temperature: Higher temperatures increase the rate of diffusion.
Concentration gradient: Greater concentration differences accelerate diffusion.
Size of molecules: Larger molecules diffuse more slowly.

Osmosis and Osmotic Pressure

Osmosis is the spontaneous movement of water towards areas of higher solute concentration, resulting in osmotic pressure on the membrane.
An example is a thistle tube demonstrating water movement from a dilute solution to a concentrated one.
Osmotic pressure can cause cells to shrink (crenation) or swell (turgidity), depending on their environment.

Water Balance in Cells

Plant cells maintain water balance through turgidity; they thrive in hypotonic environments.
Osmosis continuously occurs in living systems; for instance, in the large intestine, water is absorbed effectively.

Endocytosis and Exocytosis

Endocytosis surrounds particles or fluids with a membrane to bring them into the cell.
Exocytosis releases materials from the cell, often involving materials vacuoles merging with the membrane.
Active transport, such as the sodium-potassium pump, is energy-dependent and distinct from facilitated diffusion, which is passive.

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Description

This quiz covers Lesson 11 on the transport mechanisms within cells, including diffusion, osmosis, facilitated transport, and active transport. Additionally, it will explore the differences between exocytosis and endocytosis, providing a comprehensive understanding of cell permeability and membrane types.