Transport Across Cell Membrane

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Questions and Answers

What are the two main types of transport across the cell membrane?

Simple Diffusion and Facilitated Diffusion

Diffusion and Osmosis

Facilitated Diffusion and Active Transport

Passive Transport and Active Transport (correct)

What are the two types of passive transport?

Osmosis and Diffusion

Simple Diffusion and Facilitated Diffusion (correct)

Endocytosis and Exocytosis

Primary Active Transport and Secondary Active Transport

Simple diffusion requires energy.

False

Facilitated diffusion requires energy.

False Signup and view all the answers

Active transport requires a carrier protein.

True Signup and view all the answers

Active transport requires energy.

True Signup and view all the answers

Passive transport does not require energy.

True Signup and view all the answers

What does the term 'osmosis' mean and how is it different from simple diffusion?

Osmosis is the passive movement of water across a semi permeable membrane from a region of higher water concentration to a region of lower water concentration. It is different from simple diffusion as it is specifically about the movement of water across a membrane rather than other substances. Signup and view all the answers

What are the main ways ions move across the cell membrane?

Ions can move across the cell membrane through ion channels, which are specific protein pores that allow the passage of certain ions. There are several types of ion channels: leakage channels, which are always open, voltage-gated channels, which open in response to changes in membrane potential, and ligand-gated channels, which open in response to the binding of a specific molecule. Signup and view all the answers

What is the function of sodium potassium pumps?

Sodium-potassium pumps are active transporter proteins that use ATP to pump sodium ions out of the cell and potassium ions into the cell. They maintain the concentration gradients of sodium and potassium across the cell membrane, which is essential for nerve impulse conduction and maintaining cell volume. Signup and view all the answers

What is 'Transport Maximum' and what determines it?

Transport maximum is the maximum rate at which a substance can be transported across a membrane using a carrier protein. It is determined by the number of carrier proteins present in the membrane. In some cases, factors like hormones can also influence the number of carriers. Signup and view all the answers

Match the following types of transport with their descriptions:

Simple Diffusion = Movement of substances across a membrane without the use of energy, following the concentration gradient Facilitated Diffusion = Movement of substances across a membrane with the help of carrier proteins, but still without requiring energy, following the concentration gradient Active Transport = Movement of substances across a membrane against their concentration gradient, requiring energy and often involving carrier proteins Endocytosis = Process by which cells engulf particles or molecules from outside the cell, forming a vesicle Exocytosis = Process by which cells release particles or molecules from inside the cell, by fusing a vesicle containing these substances with the cell membrane Signup and view all the answers

Study Notes

Transport Across the Cell Membrane

Transport across cell membranes is either passive or active.
Passive transport does not require energy; active transport does.
Passive transport includes simple diffusion and facilitated diffusion.
Active transport can be primary or secondary.

Objectives

Differentiate between types of cellular transport.
Identify different channel and carrier types.
Explain how macromolecules cross cell membranes.
Define osmosis and osmotic pressure.

Simple Diffusion

A passive transport mechanism.
No energy required.
Movement of particles from high to low concentration.
Affected by Fick's Law of diffusion.
Rate of diffusion is influenced by permeability coefficient, concentration gradient, surface area, and membrane thickness.
Also affected by the substance's solubility and molecular weight.

Fick's Law of Diffusion

Diffusion rate is directly proportional to the:
- Permeability coefficient
- Concentration gradient
- Surface area
Diffusion rate is inversely proportional to membrane thickness.

Demonstration of Diffusion in Fluids and Effect of Temperature

Temperature increases the rate of diffusion.
Procedure includes placing methylene blue crystals in beakers of varying water temperatures (cold, room temperature, hot) and observing the time it takes for the dye to disperse.

Ion Channels

Important for ion diffusion.
Includes leakage channels, voltage-gated channels, and ligand-gated channels.
Ions move based on their electrochemical gradients.

Leakage Channels

Watery pathways through integral proteins.
Tubed shape, extending from the extracellular fluid (ECF) to the intracellular fluid (ICF).
Highly selective channels.
Examples: Na+ and K+ leakage channels.

Facilitated Diffusion

Passive transport that follows the concentration gradient.
Does not require energy.
Relies on carrier proteins.
Has a transport maximum.
Example: glucose transport.

Transport Maximum (Tm)

The maximum rate at which a particular substance can be transported.
Dependent on the number of carrier proteins available.
Influenced by hormones (e.g., insulin).
Reduced in certain conditions (e.g., diabetes).

Active Transport

Movement of substances against their concentration gradient.
Requires energy.
Uses carrier proteins.
Types include primary and secondary active transport.

Primary Active Transport

ATPase activity of the carrier protein.
Examples: Na+/K+ pump, Ca2+ pump, H+/K+ pump.

Secondary Active Transport

Depends on the sodium gradient established by the Na+/K+ pump.
Either cotransport or countertransport.

Exocytosis

Transport of substances out of the cell.
Active process that requires energy.

Endocytosis

Transport of substances into the cell.
Active process that requires energy.
Includes phagocytosis (ingestion of large particles).

Osmosis

Passive transport of water across a selectively permeable membrane.
Movement from high water concentration to low water concentration or from low solute concentration to high solute concentration.

Osmotic Pressure

Pressure needed to prevent water movement across a selectively permeable membrane.

Hypertonic Solution

Solute concentration outside the cell is higher than inside.
Water moves out of the cell.
Cell shrinks (crenation).

Hypotonic Solution

Solute concentration outside the cell is lower than inside.
Water moves into the cell.
Cell swells (lysis).

Isotonic Solution

Solute concentration inside and outside the cell is equal.
No net water movement.

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Description

This quiz covers the mechanisms of transport across cell membranes, emphasizing passive and active transport types. Learn to differentiate between simple diffusion and facilitated diffusion, as well as explore how macromolecules traverse cell membranes. Understand key concepts such as osmosis and the factors influencing diffusion rates.

Transport Across Cell Membrane

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Questions and Answers

What are the two main types of transport across the cell membrane?

What are the two types of passive transport?

Simple diffusion requires energy.

Facilitated diffusion requires energy.

Active transport requires a carrier protein.

Active transport requires energy.

Passive transport does not require energy.

What does the term 'osmosis' mean and how is it different from simple diffusion?

What are the main ways ions move across the cell membrane?

What is the function of sodium potassium pumps?

What is 'Transport Maximum' and what determines it?

Match the following types of transport with their descriptions:

Study Notes

Transport Across the Cell Membrane

Objectives

Simple Diffusion

Fick's Law of Diffusion

Demonstration of Diffusion in Fluids and Effect of Temperature

Ion Channels

Leakage Channels

Facilitated Diffusion

Transport Maximum (Tm)

Active Transport

Primary Active Transport

Secondary Active Transport

Exocytosis

Endocytosis

Osmosis

Osmotic Pressure

Hypertonic Solution

Hypotonic Solution

Isotonic Solution

Studying That Suits You

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