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2024 AQA AS LEVEL BIOLOGY EXAM WITH CORRECT ANSWERS
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2024 AQA AS LEVEL BIOLOGY EXAM WITH CORRECT ANSWERS
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2024 AQA AS LEVEL BIOLOGYEXAM WITH CORRECT ANSWERS
what is RNA? - CORRECT-ANSWERSribonucleic acid
MRNA and TRNA
single stranded
shorter
AU CG
what are biological molecules? - CORRECT-ANSWERSmolecules made and
used by living organisms eg. lipids, carbs, DNA, AT, water, inorganic ions
function of capillaries? - CORRECT-ANSWERSexchange site
alveoli
micro villi
near all cells
contents of blood? - CORRECT-ANSWERSblood plasma
proteins and other solutes
cells
how does exchange occur between capillaries and all cells? - CORRECT-
ANSWERSmass flow
fluid moves out of blood with nutrients
fluid moves into blood with waste
how is tissue fluid formed? - CORRECT-ANSWERSat start of capillary
ARTERIAL END buildup of hydrostatic pressure
pushes fluid out of the capillary and around cells
called tissue fluid
at end of capillary fluid moves back in by osmosis
capillary has low w/p due to proteins that can't leave capillaries too large
excess tissue fluid picked up by lymph system deposited to vena cava
why does high blood pressure cause accumulation of tissue fluid? -
CORRECT-ANSWERShigh bp= high hydrostatic pressure
more tissue fluid is formed as more fluid is pushed out of capillaries
less returns
,why do low protein diets cause tissue fluid accumulation? - CORRECT-
ANSWERSwater potential in capillary not as low as normal so less fluid
returns back into capillary as less osmosis occurs (smaller w/p gradient)
blood pressure changes in circulatory system? - CORRECT-ANSWERSarteries-
directly connected to heart so pressure fluctuates more. causes elastic tissue
to stretch and recoil
arterioles- large decrease in pressure due to increase in cross section surface
area (so pressure is not to high to damage capillaries)
capillaries- hydrostatic pressure decrease due to fluid loss
veins- under low pressure going back to heart
o2 partial pressure and affinity of haemoglobin relationship - CORRECT-
ANSWERSpositive correlation
ASSOCIATION occurs at exchange surfaces alveoli
co2 and affinity relationship? - CORRECT-ANSWERSnegative correlation
co2 is acidic so lowers ph
as co2 pp increases, haemoglobin changes shape so a lower affinity for
oxygen
DISASSOCIATION occurs at respiring cells with high con of co2
benefit as oxygen easily disassociate in cells for respiration
how does a fetus receive oxygen? - CORRECT-ANSWERSoxygen disassociate
from mothers haemoglobin and associated with fetal haemoglobin in
placenta (which has low po2)
fetal have a higher affinity at a lower partial pressure in placenta so
association with occurs more easily. baby gets enough oxygen for its needs
why do adults not keep fetal haemoglobin? - CORRECT-ANSWERStoo high
affinity, oxygen will not disassociate at respiring cells as easily. less
respiration occurs.
affinity of organisms in low oxygen environment - CORRECT-ANSWERShigh
affinity at a lower partial pressure
curve to the left
readily associate
affinity of organisms that are active - CORRECT-ANSWERSlow affinity
because don't need as much oxygen
oxygen disassociate at respiring cells easier so more respiration occurs
meets demand
affinity of small organisms - CORRECT-ANSWERShigh 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? - CORRECT-ANSWERSabsorb 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? - CORRECT-ANSWERSlong 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? - CORRECT-ANSWERSloss 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? - CORRECT-
ANSWERSmore 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 - CORRECT-ANSWERSupper epidermis with waxy cuticle
palisade cells
spongy mesophyll
air spaces
lower epidermis
guard cells and stomata
adaptation of palisade cells for photosynthesis? - CORRECT-ANSWERSnear
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 - CORRECT-ANSWERSdouble membrane
thykaloid disks stacked to make granum. contain chlorophyll
surrounded by stroma
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