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
is energy required for diffusion to occur?
no. no energy is required
is a membrane necessary for diffusion to occur?
no. diffusion occurs with or without a membrane
what are the factors that affect the rate of diffusion?
- steeper concentration gradient=increased rate of diffusion
-larger surface area to volume ratio=increased rate of diffusion
-higher temperature=increased rate of diffusion
-larger mass=decreased rate of diffusion
greater barrier thickness=decreased rate of diffusion
can water pass through a partially permeable membrane?
yes
can salts(ions) pass through a partially permeable membrane?
yes
can iodine pass through a partially permeable membrane?
yes
can ink/dye molecules pass through a partially permeable membrane?
yes
can gases (eg, co2, o2) pass through a partially permeable membrane?
yes
can glucose pass through a partially permeable membrane?
yes
can amino acids pass through a partially permeable membrane?
yes
can sucrose pass through a partially permeable membrane?
no
can starch pass through a partially permeable membrane?
no
can proteins pass through a partially permeable membrane?
no
how does diffusion occur in the nutrient uptake in plants?
plants mostly absorb mineral salts from the surrounding salt solution through diffusion,
how does diffusion occur in the gaseous exchange in plants?
for photosynthesis to occur, plants take in carbon dioxide from the surrounding air and release oxygen as a by-product. the movement of gases between the plant and the surrounding air occurs through diffusion.
how does diffusion in the nutrient uptake in humans occur?
in the small intestine, nutrients like glucose and amino acids are absorbed through the intestinal epithelial cells and into the bloodstream through diffusion.
how does the diffusion in the gaseous exchange in humans occur?
in the lungs, deoxygenated blood in the alveolar capillaries absorb oxygen and remove carbon dioxide through diffusion.
what is osmosis?
osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential, down a water potential gradient.
is energy required for osmosis?
similarly to diffusion, no energy is required.
where can osmosis occur?
it can only occur through a partially permeable membrane.
what are some factors that affect the rate of osmosis?
the stepper the water potential gradient=the higher the rate of osmosis
the larger the surface area=the higher the rate of osmosis
the higher the temperature=the higher the rate of osmosis
the greater the barrier of thickness-the slower the rate of osmosis
what are the similarities between diffusion and osmosis?
-both are passive processes (no energy required)
-particles move down a gradient
what are the differences between diffusion and osmosis?
diffusion does not require a partially permeable membrane however, osmosis does.
diffusion involves the movement of all particles (molecules, ions, etc.) however osmosis involves the movement of water particles only.
what is water potential?
the ratio of water molecules to solute molecules (glucose, salt, etc.)
what is concentration?
how much solute is dissolved in a volume of a solvent (usually water)
what is the water potential of a concentrated solution?
very low
what is the water potential of a dilute solution?
very high
what is isotonic?
iso=same, tonic=strength
same concentration of solutes and solvent
what is hypertonic?
hyper=more, tonic=strength
more solutes and less solvent
what is hypotonic?
hype=less, tonic=strength
fewer solutes, more solvent
what happens when a plant cell is placed inside a isotonic solution?
the cell cytoplasm and the surrounding solution have the same water potential, and there will be no net movement of water molecules between the cell and the surrounding solution due to the absence of a water potential gradient. water molecules will randomly enter and exit the cell, but there is no net change in water potential between the two regions. there is no observable change in the shape or size of the cell.
what happens when a plant is placed in a hypertonic cell?
when place in a hypertonic solution, the cell cytoplasm has a higher water potential than the surrounding solution, causing water molecules to move down a water potential gradient out of the cell via osmosis. the excess water leaving the cell causes the cell to plasmolyse.
the large central vacuole shrinks in size
cell membrane pull away from the cell wall
what happens when a plant is placed in a hypotonic solution?
when placed in a hypotonic solution, the cell cytoplasm has a lower water potential than the surrounding solution, causing water molecules to move down a water potential gradient into the cell via osmosis. the excess water entering the cell causes the cell to become more turgid.
the large central vacuole swells and becomes larger
overall cell increases in volume
why do animals cells act differently from plant cell when placed in solutions of differing water potentials?
due to their lack of a cell wall
what happens when a rbc is placed in an isotonic solution? (human cell)
when placed in an isotonic solution, the cell cytoplasm and the surrounding solution have the same water potential, and there will be no net movement of water molecules between the cell and the surrounding solution due to the absence of a water potential gradient. water molecules will randomly enter and exit the cell, but there is no net change in water potential between the two regions.
there is no observable change in the shape or size of the cell
rbc remains circular and biconcave
what happens when a rbc is placed in a hypertonic solution?
when placed in a hypertonic solution, the cell cytoplasm has a higher water potential than the surrounding solution, causing the water molecules to move down a water potential gradient out of the cell via osmosis. the excess water leaving the cell causes the cell to shrivel and crenate.
no cell wall to maintain its regular shape
rbc lose their circular and biconcave shape
cell membrane adopts a spiky texture
what happens when a rbc is placed in a hypotonic solution?
when placed in a hypotonic solution, the cell membrane has a lower water potential than the surrounding solution, hence the water molecules move down a water potential gradient into the cell, via osmosis. the excess water entering the cell causes the cell to swell and eventually burst.
no cell wall to maintain regular shape and prevent bursting.
