AQA A Level Biology - Paper 3 (synoptic)
3 differences between DNA and RNA - correct answerRNA has uracil as its base instead of
thymine
RNA is single stranded and DNA is double stranded
RNA has a ribose sugar where as DNA has a deoxyribose sugar
3 functions of a cell membrane - correct answer1) control transport of substances in an out of
the cell as the membrane is partially permeable
2) acts as a receptor site
3) separates cell and organelles from each other
3 types of muscle - correct answerSkeletal muscle - can be voluntarily controlled and contracts
rapidly when stimulated by nerves , act as effectors , fatigues rapidly and is attached to bones
via inelastic tendons and when the muscle contracts it pulls on the skeleton causing the bone to
move.
Smooth muscle - cannot he voluntarily controlled and is found in walls of tubular organs such as
arteries and the gut. It contacts slowly and doesn't fatigue.
Cardiac muscle - doesn't fatigue and is only found in the heart
4 main differences between slow and fast fibres ? - correct answerSlow fibres have less
sarcoplasmic reticulum than fast twitch fibres so calcium ions remain in their sarcoplasm longer.
Slow twitch fibres have more mitochondria which provide ATP via aerobic respiration for
sustained contraction than fast fibres.
Slow twitch fibres have more myoglobin than fast twitch fibres which has a very high affinity for
oxygen even more than haemoglobin in the blood and so is efficient at storing oxygen from the
blood.
Slow twitch fibres are responsible for sustained muscle contraction that contract slowly such as
maintaining body posture, where as fast twitch fibres are responsible for shorter but more
powerful contractions that contract very quickly and used in locomotion.
,Abiotic factors in an ecosystem - correct answerTemperature
Water availability
Humidity
Light intensity
Oxygen and carbon dioxide concentration
Wind speed
Salinity
pH of soil
Acetylation of Histones - correct answerWhen histones are acetylated the histones are less
condensed around DNA as DNA is slightly negatively charged due to PO4- and acetylation
removes the positive charge caused DNA to be less tightly wrapped around histones. This
means transcriptional factors can attach to DNA so the genes are switched on.
When histones are deacetylated the histones are more tightly wrapped around DNA as histones
are positively charged so are highly attracted to the negative charge on DNA due to the
phosphate group. This causes chromatin to be highly condensed and transcriptional factors can
not attach to DNA so genes are switched off and transcription is inhibited.
Acquired mutations - correct answerAre caused by mutagenic agents and environmental factors
such as smoking an radiation after fertilisation. Diagnosis would happen after symptoms appear
and treatment depends on the type of cancer as if the cancer is fast growing radiation of
chemotherapy can be used , where as if a specific gene is located to be mutated a tumour
suppressor gene can make the treatment more targeted.
Actin - correct answerThin filaments are made up of the protein actin and is made up of two
helical strands of globular actin molecules twisted around each other. Actin have binding sites
called actin myosin binding sites and are blocked by a protein called tropomyosin which can be
moved when calcium ions bind to another protein called troponin.
,Active transport - correct answerRequires energy from ATP by a hydrolysis reaction converting
ATP into ADP and Pi which releases energy. Movement of molecules from a low to high
concentration against a concentration gradient using a specific carrier protein. If any process
reduces respiration , rate of active transport will be reduced as less ATP will be produced.
Adaptations produced by natural selection - correct answerBehavioural - way an organism acts
to increase survival chances
Physiological- processes inside and organisms body that increase survival chances
Anatomical- structural features that increases chances of survival
Adaptations produced by natural selection - correct answerBehavioural - way an organism acts
to increase survival chances
Physiological- processes inside and organisms body that increase survival chances
Anatomical- structural features that increases chances of survival
ADH(antidiuretic) in osmoregulation - correct answerADH increases permeability of the
collecting duct cells by increasing transcription and causes more aquaporins to be inserted into
the membrane of the cells lining the collecting duct. Aquaporins are protein water channels that
allow water to move down their water potential gradient and out into the medulla then the
vase recta increasing the amount of water reabsorbed from the filtrate. When ADH levels fall
the aquaporins are removed from the membranes and the collecting duct becomes less
permeable.
Osmoreceptors in hypothalamus detect decrease in the water potential which stimulates
pituitary gland to release more ADH into the blood and makes the cells of the collecting duct
more permeable to water. This means when filtrate travels down collecting duct the low water
potential of the medulla causes water to move by osmosis from the filtrate to the medulla and
then into the blood so more water is reabsorbed, so a small volume of highly concentrated
urine is produced which helps the body to conserve water.
Osmoreceptors in hypothalamus detect an increase in the water potential which stimulates
pituitary gland to release less ADH into the blood and makes the cells of the collecting duct less
permeable to water. This means when filtrate travels down collecting duct far less water is
, reabsorbed by osmosis into the blood, so a large volume of dilute urine is produced which helps
the body to excrete excess water.
Adult stem cells - correct answerMultipotent or unipotent obtained from the body tissues of an
adult e.g. in bone marrow and can be removed in a simple operation with little risk. However
they can only specialise into a limited range of body cells.
Advantage of increasing heart rate during exercise to an athlete? - correct answerCardiac output
will increase
Increased blood flow to muscles
More glucose and oxygen to muscle cells
Allows for increased rates of aerobic respiration
So more ATP for muscle contraction
All or nothing principle - correct answerIf the threshold is reached then action potentials will be
generated at a constant size and speed down as the all of nothing principle. A larger stimulus
will increase the frequency of action potentials instead of making them larger.
Allele - correct answerDifferent form of a gene
Allopatric Speciation - correct answerParts of the population become geographically isolated
due to climate change or a physical barrier such as river or mountain range. No interbreeding
occurs between the two populations so there is no gene flow. The two populations experience
different selection pressures as they experience different environmental conditions. There will
be increased variation due to mutations which results in beneficial alleles which could be an
advantage in each environment so natural selection occurs in each population where organisms
with advantageous alleles will be more likely to survive and reproduce to pass on these
advantageous alleles to their offspring. This increases the frequency of the advantageous alleles
and can lead to to two different gene pools so the two populations can no longer successfully
interbreed to produce a fertile offspring. The new populations are now classes as different
species.
3 differences between DNA and RNA - correct answerRNA has uracil as its base instead of
thymine
RNA is single stranded and DNA is double stranded
RNA has a ribose sugar where as DNA has a deoxyribose sugar
3 functions of a cell membrane - correct answer1) control transport of substances in an out of
the cell as the membrane is partially permeable
2) acts as a receptor site
3) separates cell and organelles from each other
3 types of muscle - correct answerSkeletal muscle - can be voluntarily controlled and contracts
rapidly when stimulated by nerves , act as effectors , fatigues rapidly and is attached to bones
via inelastic tendons and when the muscle contracts it pulls on the skeleton causing the bone to
move.
Smooth muscle - cannot he voluntarily controlled and is found in walls of tubular organs such as
arteries and the gut. It contacts slowly and doesn't fatigue.
Cardiac muscle - doesn't fatigue and is only found in the heart
4 main differences between slow and fast fibres ? - correct answerSlow fibres have less
sarcoplasmic reticulum than fast twitch fibres so calcium ions remain in their sarcoplasm longer.
Slow twitch fibres have more mitochondria which provide ATP via aerobic respiration for
sustained contraction than fast fibres.
Slow twitch fibres have more myoglobin than fast twitch fibres which has a very high affinity for
oxygen even more than haemoglobin in the blood and so is efficient at storing oxygen from the
blood.
Slow twitch fibres are responsible for sustained muscle contraction that contract slowly such as
maintaining body posture, where as fast twitch fibres are responsible for shorter but more
powerful contractions that contract very quickly and used in locomotion.
,Abiotic factors in an ecosystem - correct answerTemperature
Water availability
Humidity
Light intensity
Oxygen and carbon dioxide concentration
Wind speed
Salinity
pH of soil
Acetylation of Histones - correct answerWhen histones are acetylated the histones are less
condensed around DNA as DNA is slightly negatively charged due to PO4- and acetylation
removes the positive charge caused DNA to be less tightly wrapped around histones. This
means transcriptional factors can attach to DNA so the genes are switched on.
When histones are deacetylated the histones are more tightly wrapped around DNA as histones
are positively charged so are highly attracted to the negative charge on DNA due to the
phosphate group. This causes chromatin to be highly condensed and transcriptional factors can
not attach to DNA so genes are switched off and transcription is inhibited.
Acquired mutations - correct answerAre caused by mutagenic agents and environmental factors
such as smoking an radiation after fertilisation. Diagnosis would happen after symptoms appear
and treatment depends on the type of cancer as if the cancer is fast growing radiation of
chemotherapy can be used , where as if a specific gene is located to be mutated a tumour
suppressor gene can make the treatment more targeted.
Actin - correct answerThin filaments are made up of the protein actin and is made up of two
helical strands of globular actin molecules twisted around each other. Actin have binding sites
called actin myosin binding sites and are blocked by a protein called tropomyosin which can be
moved when calcium ions bind to another protein called troponin.
,Active transport - correct answerRequires energy from ATP by a hydrolysis reaction converting
ATP into ADP and Pi which releases energy. Movement of molecules from a low to high
concentration against a concentration gradient using a specific carrier protein. If any process
reduces respiration , rate of active transport will be reduced as less ATP will be produced.
Adaptations produced by natural selection - correct answerBehavioural - way an organism acts
to increase survival chances
Physiological- processes inside and organisms body that increase survival chances
Anatomical- structural features that increases chances of survival
Adaptations produced by natural selection - correct answerBehavioural - way an organism acts
to increase survival chances
Physiological- processes inside and organisms body that increase survival chances
Anatomical- structural features that increases chances of survival
ADH(antidiuretic) in osmoregulation - correct answerADH increases permeability of the
collecting duct cells by increasing transcription and causes more aquaporins to be inserted into
the membrane of the cells lining the collecting duct. Aquaporins are protein water channels that
allow water to move down their water potential gradient and out into the medulla then the
vase recta increasing the amount of water reabsorbed from the filtrate. When ADH levels fall
the aquaporins are removed from the membranes and the collecting duct becomes less
permeable.
Osmoreceptors in hypothalamus detect decrease in the water potential which stimulates
pituitary gland to release more ADH into the blood and makes the cells of the collecting duct
more permeable to water. This means when filtrate travels down collecting duct the low water
potential of the medulla causes water to move by osmosis from the filtrate to the medulla and
then into the blood so more water is reabsorbed, so a small volume of highly concentrated
urine is produced which helps the body to conserve water.
Osmoreceptors in hypothalamus detect an increase in the water potential which stimulates
pituitary gland to release less ADH into the blood and makes the cells of the collecting duct less
permeable to water. This means when filtrate travels down collecting duct far less water is
, reabsorbed by osmosis into the blood, so a large volume of dilute urine is produced which helps
the body to excrete excess water.
Adult stem cells - correct answerMultipotent or unipotent obtained from the body tissues of an
adult e.g. in bone marrow and can be removed in a simple operation with little risk. However
they can only specialise into a limited range of body cells.
Advantage of increasing heart rate during exercise to an athlete? - correct answerCardiac output
will increase
Increased blood flow to muscles
More glucose and oxygen to muscle cells
Allows for increased rates of aerobic respiration
So more ATP for muscle contraction
All or nothing principle - correct answerIf the threshold is reached then action potentials will be
generated at a constant size and speed down as the all of nothing principle. A larger stimulus
will increase the frequency of action potentials instead of making them larger.
Allele - correct answerDifferent form of a gene
Allopatric Speciation - correct answerParts of the population become geographically isolated
due to climate change or a physical barrier such as river or mountain range. No interbreeding
occurs between the two populations so there is no gene flow. The two populations experience
different selection pressures as they experience different environmental conditions. There will
be increased variation due to mutations which results in beneficial alleles which could be an
advantage in each environment so natural selection occurs in each population where organisms
with advantageous alleles will be more likely to survive and reproduce to pass on these
advantageous alleles to their offspring. This increases the frequency of the advantageous alleles
and can lead to to two different gene pools so the two populations can no longer successfully
interbreed to produce a fertile offspring. The new populations are now classes as different
species.
