movement of substances
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What is diffusion?
The net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient May or may not be through a partially permeable membrane.
What are natural and man-made examples of partially permeable membranes (ppms)?
• Natural ppms: cell surface membrane (glucose and oxygen can pass through, maltose cannot) • Man-made ppms: Visking tubing / dialysis tubing (oxygen, glucose, and maltose can pass through, starch and sucrose cannot) These membranes allow selective passage of certain molecules.
List the factors that affect the rate of diffusion.
• Diffusion distance • Surface area to volume ratio Shorter diffusion distance and higher surface area to volume ratio increase the rate of diffusion.
What is osmosis?
The net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane This process is crucial for maintaining cell turgidity.
What does the NDPEE answering technique stand for?
• N: name of molecule • D: direction of movement • P: state the process • E: explanation • E: effect that it has on the cell This technique helps structure responses regarding molecular movement.
What are the factors that affect the rate of osmosis?
• Water potential gradient • Distance • Surface area to volume ratio Similar to diffusion, these factors influence the efficiency of osmosis.
What happens to an animal cell placed in a solution with higher water potential than inside the cell?
Water molecules enter the cell by osmosis, causing the cell to burst This occurs because there is no cellulose cell wall to protect the cell.
What happens to an animal cell placed in a solution with lower water potential than inside the cell?
Water molecules move from inside the cell to the solution, causing the cell to shrink and crenate This results from the loss of water due to osmosis.
What happens to a plant cell placed in a solution with higher water potential than inside the cell?
Water molecules enter the cell, the vacuole increases in size, and the cell becomes turgid The cellulose cell wall prevents the cell from bursting.
What is turgor pressure?
The pressure exerted by the water molecules in the large central vacuole against the cellulose cell wall It helps maintain the shape of soft tissues in the plant.
What happens to a plant cell placed in a solution with lower water potential than inside the cell?
Water molecules move from inside the vacuole to the solution, causing the cell to plasmolyse and become flaccid If further water loss occurs, the cell decreases in size and becomes flaccid.
What is active transport?
Process by which energy is used to move particles across a membrane from a region of lower concentration to a region of higher concentration against its concentration gradient This process only occurs in living cells as it requires energy.
Why do cells that perform active transport often have an abundance of mitochondria?
To release more energy for faster absorption For example, root hair cells (RHC) use active transport to take in mineral salts and ions.