Chap 2: Movement of substances Flashcards
What is diffusion?
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient.
What factors affect the rate of diffusion?
- Concentration gradient
- Diffusion distance
- Surface area to volume ratio
What is concentration gradient?
Concentration gradient is the difference in concentration between two regions.
How does diffusion distance affect the rate of diffusion?
The shorter the diffusion distance, the less time is needed for the substance to travel, resulting in a higher rate of diffusion.
How is surface area to volume ratio related to diffusion?
The greater the surface area to volume ratio of a cell, the higher the rate at which substances move in and out of it.
What is osmosis?
Osmosis is the net movement of water molecules down a water potential gradient, across a partially permeable membrane.
What is water potential?
Water potential is a measure of the tendency of water molecules to move from a region of higher water potential to a region of lower water potential.
How does osmosis affect plant cells in higher water potential?
- Plant cells become turgid as water molecules enter the cell through osmosis.
- The cell expands and swells.
How does osmosis affect animal cells in higher water potential?
- Animal cells swell as water molecules enter the cell through osmosis.
- The cell may burst due to the absence of a cell wall.
How does osmosis affect plant cells in lower water potential?
Plant cells become flaccid or limp as water molecules leave the cell through osmosis.
The cell decreases in size and becomes shriveled.
How does osmosis affect animal cells in lower water potential?
- Animal cells shrink and spikes may appear on the cell through osmosis.
- The cell becomes dehydrated and may eventually die.
What happens when plant cells and the solution have the same water potential?
There is no net movement of water molecules in or out of the cell.
What is active transport?
Active transport is the process that uses energy to move particles of a substance across a partially permeable membrane against its concentration gradient.
Where does active transport occur?
Active transport occurs in living things and requires a partially permeable membrane, such as the cell membrane.
What is the role of mitochondria in active transport?
Mitochondria release energy through aerobic respiration, which is required for active transport.
How does active transport work?
Active transport involves the net movement of particles from a region of lower concentration to a region of higher concentration.
Give an example of active transport.
Glucose molecules can move from a solution with a lower concentration (region of lower concentration) to a solution with a higher concentration (region of higher concentration) through active transport.
What is the relationship between the concentration gradient and the rate of diffusion?
The steeper the concentration gradient for a substance, the faster the rate of diffusion for that substance.
How can you calculate the surface area to volume ratio?
Surface area to volume ratio is calculated by finding the area of one side and multiplying it by the number of sides, then dividing it by the volume.
What is the function of microvilli in the small intestine?
Microvilli increase the surface area to volume ratio of the small intestine wall, resulting in a higher rate of diffusion.
