AQA AS level Biology Exam Questions and Answers |Complete Solutions Graded A+ |100%
Correct
why do adults not keep fetal haemoglobin? too high affinity, oxygen will not disassociate at
respiring cells as easily. less respiration occurs.
affinity of organisms in low oxygen environment high affinity at a lower partial pressure
curve to the left
readily associate
affinity of organisms that are active low affinity because don't need as much oxygen
oxygen disassociate at respiring cells easier so more respiration occurs
meets demand
affinity of small organisms high sa to volume ratio so they lose a lot of heat so need to
generate more heat energy through respiration
low affinity so oxygen disassociates more easily at respiring cells so more energy is produced
jobs of the roots? absorb water and minerals
has a low water potential when it absorbs minerals so water moves into root cells by osmosis
plants need water and minerals for photosynthesis/turgidity/hydration/making amino acids and
ATP
structure of xylem? long continuous hollow tube
narrow lumen
wall made of lignin-strong,waterproof,adhesive
wall contains pits and pores so minerals can leave
how does water move up xylem? loss of water at leaves transpiration
,water moves from top of xylem to leaf by osmosis
applies TENSION to water column
water molecules are cohesive because of hydrogen bonds-transpirational pull
cohesion tension theory
roots absorb water so high hydrostatic pressure, pushes water up down con gradient
why does the diameter of a tree decrease during the day? more light and higher temp
increased transpiration rate so increased transpirational pull
walls of xylem are pulled in bc water molecules stick to xylem wall
water pulled up xylem by cohesion tension.
leaf structure upper epidermis with waxy cuticle
palisade cells
spongy mesophyll
air spaces
lower epidermis
guard cells and stomata
adaptation of palisade cells for photosynthesis? near top so close to light
large size and surface area
thin cell wall so short diffusion difference for co2
many chloroplasts
large vacuole pushes chloroplasts
structure of chloroplast double membrane
thykaloid disks stacked to make granum. contain chlorophyll
surrounded by stroma
,how does exchange in leaf occur? when turgid, guard cells open forming stomata opening
day- ps and respiration so co2 moves in and o2 moves out
night- respiration so co2 moves out and o2 moves in
how does transpiration occur? moist spongy mesophyll cell lining evaporates forming water
vapour
builds up in air spaces
if con is high enough, water vapour diffuses out
h2o molecules are polar so form hydrogen bonds- transpiration stream
factors increasing transpiration rate more light more stomata open increase s/a for
transpiration
higher temp mote evaporation so increased vapour concentration and more kinetic energy
wind maintains concentration gradient- blows vapour away
less humidity less water vapour in surrounding air so increased concentration gradient
principle of a potometer as transpiration in leaf occurs, plant will pull up more water from
potometer by cohesion tension causing bubble to move towards plant
more water loss, more water taken up, further bubble moved
measuring rate of transpiration volume of transpiration/time
volume- distance bubble moved x cross section tube area
setting up a potometer? choose healthy leaf and shoot
cut shoot underwater and connect potometer jnderwater to prevent air bubbles blocking xylem
or entering
ensure air tight and water tight so no air bubbles form
, what does a potometer measure? rate of water uptake as a result of water loss from plant
(due to photosynthesis, turgid it, transpiration)
xerophyte adaptations? c shaped curved/ needle like leaf reduces surface area
waterproof thick waxy cuticle
spongy mesophyll are densely packed so less air space for water vapour to build up in for
transpiration
sunken stomata/ hairs/curled leaf traps moist layer of air to reduce con gradient
what is RNA? ribonucleic acid
MRNA and TRNA
single stranded
shorter
AU CG
what are biological molecules? molecules made and used by living organisms eg. lipids,
carbs, DNA, AT, water, inorganic ions
what are the functions of carbohydrates? -energy source (respiration)
-energy store (starch and glycogen)
-structure (cellulose)
ATP structure? 1 adenosine 3 phosphates
ADP and energy= ATP
condensation reaction using ATP synthase
carries energy in bonds
hydrolysis breaks down into ADP and energy using ATP hydrolase
Correct
why do adults not keep fetal haemoglobin? too high affinity, oxygen will not disassociate at
respiring cells as easily. less respiration occurs.
affinity of organisms in low oxygen environment high affinity at a lower partial pressure
curve to the left
readily associate
affinity of organisms that are active low affinity because don't need as much oxygen
oxygen disassociate at respiring cells easier so more respiration occurs
meets demand
affinity of small organisms high sa to volume ratio so they lose a lot of heat so need to
generate more heat energy through respiration
low affinity so oxygen disassociates more easily at respiring cells so more energy is produced
jobs of the roots? absorb water and minerals
has a low water potential when it absorbs minerals so water moves into root cells by osmosis
plants need water and minerals for photosynthesis/turgidity/hydration/making amino acids and
ATP
structure of xylem? long continuous hollow tube
narrow lumen
wall made of lignin-strong,waterproof,adhesive
wall contains pits and pores so minerals can leave
how does water move up xylem? loss of water at leaves transpiration
,water moves from top of xylem to leaf by osmosis
applies TENSION to water column
water molecules are cohesive because of hydrogen bonds-transpirational pull
cohesion tension theory
roots absorb water so high hydrostatic pressure, pushes water up down con gradient
why does the diameter of a tree decrease during the day? more light and higher temp
increased transpiration rate so increased transpirational pull
walls of xylem are pulled in bc water molecules stick to xylem wall
water pulled up xylem by cohesion tension.
leaf structure upper epidermis with waxy cuticle
palisade cells
spongy mesophyll
air spaces
lower epidermis
guard cells and stomata
adaptation of palisade cells for photosynthesis? near top so close to light
large size and surface area
thin cell wall so short diffusion difference for co2
many chloroplasts
large vacuole pushes chloroplasts
structure of chloroplast double membrane
thykaloid disks stacked to make granum. contain chlorophyll
surrounded by stroma
,how does exchange in leaf occur? when turgid, guard cells open forming stomata opening
day- ps and respiration so co2 moves in and o2 moves out
night- respiration so co2 moves out and o2 moves in
how does transpiration occur? moist spongy mesophyll cell lining evaporates forming water
vapour
builds up in air spaces
if con is high enough, water vapour diffuses out
h2o molecules are polar so form hydrogen bonds- transpiration stream
factors increasing transpiration rate more light more stomata open increase s/a for
transpiration
higher temp mote evaporation so increased vapour concentration and more kinetic energy
wind maintains concentration gradient- blows vapour away
less humidity less water vapour in surrounding air so increased concentration gradient
principle of a potometer as transpiration in leaf occurs, plant will pull up more water from
potometer by cohesion tension causing bubble to move towards plant
more water loss, more water taken up, further bubble moved
measuring rate of transpiration volume of transpiration/time
volume- distance bubble moved x cross section tube area
setting up a potometer? choose healthy leaf and shoot
cut shoot underwater and connect potometer jnderwater to prevent air bubbles blocking xylem
or entering
ensure air tight and water tight so no air bubbles form
, what does a potometer measure? rate of water uptake as a result of water loss from plant
(due to photosynthesis, turgid it, transpiration)
xerophyte adaptations? c shaped curved/ needle like leaf reduces surface area
waterproof thick waxy cuticle
spongy mesophyll are densely packed so less air space for water vapour to build up in for
transpiration
sunken stomata/ hairs/curled leaf traps moist layer of air to reduce con gradient
what is RNA? ribonucleic acid
MRNA and TRNA
single stranded
shorter
AU CG
what are biological molecules? molecules made and used by living organisms eg. lipids,
carbs, DNA, AT, water, inorganic ions
what are the functions of carbohydrates? -energy source (respiration)
-energy store (starch and glycogen)
-structure (cellulose)
ATP structure? 1 adenosine 3 phosphates
ADP and energy= ATP
condensation reaction using ATP synthase
carries energy in bonds
hydrolysis breaks down into ADP and energy using ATP hydrolase
