Means of Transport (Diffusion, Facilitated Diffusion, Active Transport)
Explores passive (simple diffusion, facilitated diffusion) and active transport mechanisms across cell membranes in plants.
What is Means of Transport (Diffusion, Facilitated Diffusion, Active Transport)?
The net movement of any substance from a region of higher concentration to a region of lower concentration.
Key points
- Differentiate between passive and active transport.
- Explain the mechanisms of simple diffusion, facilitated diffusion, and active transport.
- Identify the role of membrane proteins in transport.
- Understand the energy requirements for each transport mechanism.
Common exam trap
Confusing passive and active transport regarding energy requirement.
Definitions
- Term
Diffusion
- Meaning
The net movement of any substance from a region of higher concentration to a region of lower concentration.
- Term
Facilitated Diffusion
- Meaning
The passive movement of molecules across a cell membrane via a transmembrane intermediary, such as a membrane protein.
- Term
Active Transport
- Meaning
The movement of molecules across a cell membrane against their concentration gradient, requiring energy and specific transport proteins (pumps).
- Term
Concentration Gradient
- Meaning
The gradual difference in the concentration of solutes in a solution between the two sides of a semipermeable membrane.
- Term
Selectively Permeable Membrane
- Meaning
A membrane that allows certain molecules or ions to pass through it by means of diffusion or active transport.
Learning objectives
Differentiate between passive and active transport.
Explain the mechanisms of simple diffusion, facilitated diffusion, and active transport.
Identify the role of membrane proteins in transport.
Understand the energy requirements for each transport mechanism.
Recognize examples of each transport type in biological systems.
Prerequisites
Cell structure and function (plasma membrane composition).
Concentration gradients.
Basic understanding of energy (ATP).
Common mistakes
Confusing passive and active transport regarding energy requirement.
Assuming all membrane transport is simple diffusion.
Not understanding the role of proteins in facilitated diffusion and active transport.
Forgetting that facilitated diffusion can be saturated.
Practice preview
The movement of water across a semipermeable membrane from a region of higher water concentration to a region of lower water concentration is called:…
easy
A cell is placed in a solution where the solute concentration outside the cell is higher than inside. If the cell membrane is permeable to water but impermeable to the solute, what will happen to the cell?…
medium
The rate of diffusion is affected by several factors. Which of the following factors would DECREASE the rate of diffusion across a membrane?…
medium