BOT3015 EXAM 3 Marking Scheme 2024/2025
Brownian movement - Answer-molecules /ions in constant random motion
/.Diffusion - Answer-movement of molecules or ions from region of higher concentration
to region of lower concentration
/.Molecules that are moving from a region of higher concentration to a region of lower
concentration are said to be moving ______________________________ - Answer-
Along a diffusion gradient
/.molecules moving from regions of low to high concentration are said to be moving
______________________ - Answer-against a diffusion gradient
/.Equilibrium - Answer-When the molecules, through their random movement, have
become distributed throughout the space available
/.Rate of diffusion depends on several factors such as - Answer-pressure, temperature,
and density
/.Solvents - Answer-Are liquids in which substances dissolve
Water (a solvent) moves freely from cell to cell
/.semipermeable membrane - Answer-membranes through which different substances
diffuse at different rates
/.Osmosis - Answer-the diffusion of water through a semipermeable membrane from a
region where the water is more concentrated to a region where it is less concentrated
osmosis ceases if concentration of water on both sides of membrane becomes equal
/.osmotic pressure - Answer-pressure that must be applied to prevent osmotic
movement across a selectively permeable membrane
/.osmotic potential - Answer-a measure of the potential of water to move from one cell to
another as influenced by solute concentration
/.Water gained by osmosis may keep a cell firm or ___________ - Answer-Turgid
/.turgor pressure - Answer-pressure within a cell resulting from the uptake of water
,/.pressure potential (ΨP) - Answer-turgor pressure that develops against walls as a
result of water entering the vacuole of the cell
/.water potential - Answer-osmotic potential and pressure potential combined
/.___________ is primary means through which water enters plant from their
surrounding environment - Answer-Omosis
/.Osmosis steps - Answer-1. Water from soil enters the cell walls and intracellular
spaces of the epidermis and root hairs and travels along walls until it reaches
endothermis
2. here it crosses differentially permeable mebranes and cytoplasm of the endodermal
cells on its's way to xylem
3. Water flows from the xylem to the leaves, evaporates within the leaf air spaces, and
diffuses out through stomata into the atmosphere
4. The movement of water takes place because there is a water potentil gradient from
relatively high soil water potential to so succesively lower water potentials in roots,
stems, leaves and the atmosphere
/.Plasmolysis - Answer-the loss of water through osmosis, which is accompanied by the
shrinkage of protoplasm away form the cell wall
If plasmolyzed cells are placed in freshwater before permanent damage is done, water
reenters cells through osmosis and cells become turgid
/.Colloidal materials - Answer-materials that contain a permanent suspension of fine
particles
/.Imbition - Answer-absorption of water and subsequent swelling of organic materials
because of the adhesion of the water molecules to the internal surfaces
is the initial step in the germination of seeds
/.Transport molecules believed to occur in two forms - Answer-1. one facilitating the
transport of specific ions to the outside of the cell
2. the other facilitating the transport of specific ions into the cell
/.Active Transport - Answer-the expenditure of energy by a cell in moving a substance
across a plasma membrane against a diffusion gradient
/.proton pump - Answer-An electrogenic pump that works largely with H+ ions.
, pump helps regulate which ions pass through the cell membrane and this is often
accompanied by expenditure of energy rich ATP MOLECULES
/.Mangroves, saltbush, and certain algae - Answer-thrive in areas where the water or
soil contains salt to kill most vegetation
they accumulate organic solutes such as the carbohydrate mannitiol and the amino acid
proline
/.More than 90% of water entering plant passes through and evaporates into _________
and then through stomata into the atmosphere - Answer-leaf air spaces
/.Transpiration - Answer-the process of vapor loss from the internal leaf atmosphere
/.Why do living plants require so much water? - Answer-exposed mesophyll surfaces of
the leaf have to be moist at all times
also needed for cell turgor, which gives
/.root pressure - Answer-The upward push of water within the stele of vascular plants,
caused by active pumping of minerals into the xylem by root cells
/.polar molecule - Answer-slightly positive charge on one end slightly negative charge
on other end
/.cohesion-tension theory - Answer-water molecules are electrically neutral but they're
asymmetrical in shape resulting in polar molecules
/.Weak hydrogen bonds - Answer-when the negatively charged end of one water
molecule comes close to the positively charged end of another water molecule
/.Stomata - Answer-A microscopic pore surrounded by guard cells in the epidermis of
leaves and stems that allows gas exchange between the environment and the interior of
the plant.
/.Control of water transpiration is strongly influenced by ______________ - Answer-
water evaporation of the atmosphere
/.Guard cells - Answer-guard cells bordering each stoma have relatively elastic walls
with radially oriented microfibrils
/.stoma is closed when - Answer-turgor pressure is low
/.stoma is opened when - Answer-turgor pressure is high
Brownian movement - Answer-molecules /ions in constant random motion
/.Diffusion - Answer-movement of molecules or ions from region of higher concentration
to region of lower concentration
/.Molecules that are moving from a region of higher concentration to a region of lower
concentration are said to be moving ______________________________ - Answer-
Along a diffusion gradient
/.molecules moving from regions of low to high concentration are said to be moving
______________________ - Answer-against a diffusion gradient
/.Equilibrium - Answer-When the molecules, through their random movement, have
become distributed throughout the space available
/.Rate of diffusion depends on several factors such as - Answer-pressure, temperature,
and density
/.Solvents - Answer-Are liquids in which substances dissolve
Water (a solvent) moves freely from cell to cell
/.semipermeable membrane - Answer-membranes through which different substances
diffuse at different rates
/.Osmosis - Answer-the diffusion of water through a semipermeable membrane from a
region where the water is more concentrated to a region where it is less concentrated
osmosis ceases if concentration of water on both sides of membrane becomes equal
/.osmotic pressure - Answer-pressure that must be applied to prevent osmotic
movement across a selectively permeable membrane
/.osmotic potential - Answer-a measure of the potential of water to move from one cell to
another as influenced by solute concentration
/.Water gained by osmosis may keep a cell firm or ___________ - Answer-Turgid
/.turgor pressure - Answer-pressure within a cell resulting from the uptake of water
,/.pressure potential (ΨP) - Answer-turgor pressure that develops against walls as a
result of water entering the vacuole of the cell
/.water potential - Answer-osmotic potential and pressure potential combined
/.___________ is primary means through which water enters plant from their
surrounding environment - Answer-Omosis
/.Osmosis steps - Answer-1. Water from soil enters the cell walls and intracellular
spaces of the epidermis and root hairs and travels along walls until it reaches
endothermis
2. here it crosses differentially permeable mebranes and cytoplasm of the endodermal
cells on its's way to xylem
3. Water flows from the xylem to the leaves, evaporates within the leaf air spaces, and
diffuses out through stomata into the atmosphere
4. The movement of water takes place because there is a water potentil gradient from
relatively high soil water potential to so succesively lower water potentials in roots,
stems, leaves and the atmosphere
/.Plasmolysis - Answer-the loss of water through osmosis, which is accompanied by the
shrinkage of protoplasm away form the cell wall
If plasmolyzed cells are placed in freshwater before permanent damage is done, water
reenters cells through osmosis and cells become turgid
/.Colloidal materials - Answer-materials that contain a permanent suspension of fine
particles
/.Imbition - Answer-absorption of water and subsequent swelling of organic materials
because of the adhesion of the water molecules to the internal surfaces
is the initial step in the germination of seeds
/.Transport molecules believed to occur in two forms - Answer-1. one facilitating the
transport of specific ions to the outside of the cell
2. the other facilitating the transport of specific ions into the cell
/.Active Transport - Answer-the expenditure of energy by a cell in moving a substance
across a plasma membrane against a diffusion gradient
/.proton pump - Answer-An electrogenic pump that works largely with H+ ions.
, pump helps regulate which ions pass through the cell membrane and this is often
accompanied by expenditure of energy rich ATP MOLECULES
/.Mangroves, saltbush, and certain algae - Answer-thrive in areas where the water or
soil contains salt to kill most vegetation
they accumulate organic solutes such as the carbohydrate mannitiol and the amino acid
proline
/.More than 90% of water entering plant passes through and evaporates into _________
and then through stomata into the atmosphere - Answer-leaf air spaces
/.Transpiration - Answer-the process of vapor loss from the internal leaf atmosphere
/.Why do living plants require so much water? - Answer-exposed mesophyll surfaces of
the leaf have to be moist at all times
also needed for cell turgor, which gives
/.root pressure - Answer-The upward push of water within the stele of vascular plants,
caused by active pumping of minerals into the xylem by root cells
/.polar molecule - Answer-slightly positive charge on one end slightly negative charge
on other end
/.cohesion-tension theory - Answer-water molecules are electrically neutral but they're
asymmetrical in shape resulting in polar molecules
/.Weak hydrogen bonds - Answer-when the negatively charged end of one water
molecule comes close to the positively charged end of another water molecule
/.Stomata - Answer-A microscopic pore surrounded by guard cells in the epidermis of
leaves and stems that allows gas exchange between the environment and the interior of
the plant.
/.Control of water transpiration is strongly influenced by ______________ - Answer-
water evaporation of the atmosphere
/.Guard cells - Answer-guard cells bordering each stoma have relatively elastic walls
with radially oriented microfibrils
/.stoma is closed when - Answer-turgor pressure is low
/.stoma is opened when - Answer-turgor pressure is high
