Active transport is the movement of molecules from a low concentration to a high concentration, against the concentration gradient. This process requires energy. An example of a substance that moves by active transport is starch (or any other large molecule).
Active Transport Example in Plants
Water would move from a high water concentration inside the leaf cell to a low water concentration outside the leaf cell, causing the leaf cell to become plasmolysed.
When placed in a low water concentration solution, a leaf cell would become plasmolysed.
Active Transport Example in the Human Body
When placed in a high water concentration solution, a red blood cell would burst. Water would move from a high concentration in the solution outside the cell to a low water concentration inside the cell, causing the red blood cell to burst.
The function of the cell membrane is to control the entry and exit of molecules into and out of the cell.
Osmosis, Plasmolysis, and Turgor
Osmosis is the passive movement of water molecules from a high water concentration to a low water concentration down a water concentration gradient. Plasmolysed refers to a plant cell that has become shrunken due to water loss, and turgid is a plant cell that has become swollen due to water gain. Labeling a diagram to show the two chemical components of a cell membrane.
Diffusion and Facilitated Diffusion
Diffusion is the passive movement of molecules from a high concentration to a low concentration down a concentration gradient. Four substances that move by diffusion are oxygen, carbon dioxide, glucose, amino acids, and urea. Facilitated diffusion is the passive movement of molecules from a high concentration to a low concentration down a concentration gradient, but it requires the assistance of transport proteins.
Explain why glucose sugar can move across the cell membrane, but not starch. The cell membrane is selectively permeable, meaning only small, soluble molecules can pass through. Glucose and sugar are both small molecules so can move across the cell membrane, whereas starch is a larger molecule so can't.
