pp Flashcards
(33 cards)
Contrasting features of adult and embryonic stem cells
Adult stem cells can only become a few different cell types / a specific cell type / are limited in their ability to differentiate WHILE embryo stem cells are totipotent / have the ability to become/differentiate into any type of cell; [1 mark]
Adult stem cells are found in specific places in the (fully developed) body / the bone marrow / the skin / the umbilical cord WHILE embryonic stem cells are found in a developing embryo; [1 mark]
The role of adult stem cells is to replace old/dead/damaged cells WHILE the role of embryonic stem cells is to allow the development of a whole organism/individual / all of the tissues/organs; [1 mark]
Scientists researching the regenerative capacity ofthe liver have identified a chemical signalling pathway inside
liver cells that prevents the liverfrom growing too large when itregenerates. This chemical signalling pathway has
been named ‘Hippo’.
A recent discovery has shown that switching off the Hippo signalling pathway reverses the differentiation process,
resulting in de-differentiated liver cells.
Suggest whatthis discovery could mean forthe development of stem celltherapies
The liver cells (once they have de-differentiated) would be able to specialise/differentiate into many different cell types / could become pluripotent/totipotent; [1 mark]
De-differentiated liver cells could be grown into new tissues/organs in the lab; [1 mark]
De-differentiated liver cells could be injected into patients to replace damaged cells / instead of an organ/liver transplant; [1 mark]
Tissues/organs grown from a patient’s own liver cells would not be rejected (by their immune system); [1 mark]
Explain how differentiation allowed the plant root hair cell to carry out its specific function.
Certain genes get switched on/activated or switched off/inactivated (during differentiation); [1 mark]
The cell produces different substances/proteins / develops different organelles / develops into a different shape; [1 mark]
Root hair cells grow extensions / root hairs to give a large surface area SO maximising water/mineral absorption; [1 mark]
They develop mitochondria to provide energy for absorption of mineral ions; [1 mark]
A large vacuole for storage of water/cell sap; [1 mark]
Root hair cells have no chloroplasts AS they do not photosynthesize; [1 mark]
why do grass roots contain startch
Plants carry out photosynthesis to produce glucose/sugars; [1 mark]
Sugars/sucrose are transported from the leaves to the roots; [1 mark]
Glucose is stored in the form of starch; [1 mark]
Why may a plants startch level in roots increase?
During the summer/autumn there are more hours of sunlight / the temperatures are higher; [1 mark]
More photosynthesis occurs in summer/autumn SO plants produce lots of glucose; [1 mark]
Plants produce more glucose than they can (immediately) use SO excess glucose is stored / used to build up starch stores / transported to roots for storage; [1 mark]
How do cells differentiate
Some genes are switched on/activated and others are switched off/deactivated; [1 mark]
The cell produces different substances/proteins/organelles (depending on which genes have been switched on/off); [1 mark]
The cell differentiates; [1 mark
What if a root hair cell is damaged?
The function of X/the root hair is to increase surface area; [1 mark]
For absorption of water (by osmosis); [1 mark]
(And) for absorption of mineral ions / named example, e.g. magnesium ions, nitrate ions; [1 mark]
Fewer/shorter root hairs would reduce absorption; [1 mark]
Water is essential for photosynthesis / maintaining pressure / as a solvent; [1 mark]
Reduced absorption could lead to mineral deficiencies / named example of mineral deficiency; [1 mark]
scaffald ensures
To ensure that the cells grow in the correct positions / in the shape of a heart OR without a scaffold the cells will just form a ball/mass; [1 mark]
To ensure that the correct cell types/tissues grow in the correct places; [1 mark
Suggestthe practical and ethical considerations that should be taken into account when developing scaffolds
from human or animal donors
There is already a shortage of human donors so the need for a donor heart does not solve this problem; [1 mark]
The oxygen/nutrients need to reach every cell / a transport system is needed inside the developing heart; [1 mark]
Any donor/animal cells not removed from the scaffold could cause rejection of the new heart OR the stem cells used to grow the new heart could cause rejection if they do not match the patient; [1 mark]
Many people may have ethical concerns about the use of animal hearts; [1 mark]
Many have concerns around the use of embryonic stem cells; [1 mark]
Describe the structure of a protein such as an enzyme.
Contains chemical elements carbon, oxygen, hydrogen, nitrogen; [1 mark]
Amino acids joined together (in chains to make protein); [1 mark]
The order of amino acids determines the shape of the protein; [1 mark]
Enzymes have an active site (where the substrate will bind); [1 mark]
Why yeats causes bread to rise
(Yeast) respires / (carries out) fermentation; [1 mark]
(Respiration of yeast cells) produces carbon dioxide; [1 mark]
(Carbon dioxide) bubbles become trapped/stuck in the dough / cause the dough to inflate; [
Suggest a problem with using the level of cloudiness ofthe solution to determine how spoiled the peas have
become.
Judgement of cloudiness is subjective / cannot be repeated (in exactly the same way) by other people / done by eye; [1 mark]
Judgement of cloudiness is qualitative / is not quantitative / cannot be accurately measured (by eye) / cannot accurately measure the difference in cloudiness / is imprecise / cannot see small differences in cloudiness; [1 mark]
Calculate the energy content (per g) =
4.2 x mass of water × temp rise ÷ (mass of crisp);
Explain why stem cells can be used to make large quantities ofred blood cells. (Lines 22 and 23)
Stem cells can divide / perform/carry out mitosis; [1 mark]
Stem cells can differentiate/specialise / become any/other cell type(s) / are undifferentiated/unspecialised; [1 mark]
Describe and explain how this process differs between fit people and unfit people.
removing lactic acid from muscles
Unfit people take longer to recover; [1 mark]
(Unfit people) lactic acid levels go down slower; [1 mark]
Heart/cardiac muscle is weaker (in unfit people); [1 mark]
(Unfit person) take more time for enough oxygen to circulate the body (to pay back oxygen debt); [1 mark]
Accept converse for all marking points e.g. fit people take less time to recover
6 ways en. from resp used
Maintaining (core) body temperature / keeping warm / thermoregulation; [1 mark]
Movement / muscle contraction / named example of muscle movement, e.g. heart beating / peristalsis; [1 mark]
Synthesis of new molecules / chemical reactions to build large molecules (e.g proteins); [1 mark]
Cell growth / division; [1 mark]
Active transport / transporting molecules across cell membranes against their concentration gradient; [1 mark]
generating/transmitting nerve impulses; [1 mark]
Root hair adapt.
They have) elongated / pointed / projections / extensions; [1 mark]
(Which) increase surface area; [1 mark]
(They have a) thin wall for short diffusion path; [1 mark]
(They contain) concentrated cell sap for osmosis; [1 mark]
(They have a ) low water potential to increase gradient for osmosis / increase water potential gradient; [1 mark]
Explain why a mouse uses more oxygen per gram than a human
y three of the following:
The mouse is smaller / less body mass; [1 mark]
It has a larger surface area to volume ratio; [1 mark]
(Therefore there will be more) heat loss / mice lose heat faster; [1 mark]
(Mice need to) maintain body temperature; [1 mark]
(Therefore more) respiration / higher metabolic rate; [1 mark]
Humans can run for long periods oftime. Frogs can only move for short periods oftime.
Explain how the structure ofthe heart of a frog means thatitis unable to move for long periods oftime.
Picture is similar to human heart but lacks septum
has only) one ventricle; [1 mark]
This means that oxygenated and deoxygenated blood mixes / blood from body mixes with blood from lung; [1 mark]
So less deoxygenated blood goes to lungs / some oxygenated blood to lungs; [1 mark]
This results in less efficient gas exchange in lungs; [1 mark]
(The frog heart has) no semi-lunar valves; [1 mark]
So there will be backflow of blood into ventricle; [1 mark]
This means less oxygenated blood to body / some deoxygenated blood to body / less oxygen (to body); [1 mark]
Therefore less respiration / more anaerobic respiration; [1 mark]
Lactic acid accumulation / less ATP made / less energy released ; [1 mark]
Give two otherfactors that affectthe volume of urine produced.
Exercise / sweating / activity; [1 mark]
The volume of fluid consumed / what they drank before the investigation; [1 mark]
Temperature; [1 mark]
The type/amount of food eaten / diet (during the investigation); [1 mark]
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Describe the series of events that would need to occur within the structures covered in part(a) in orderforthe diaphragm
to contract.
A nerve impulse arrives at the end of neurone X/the relay neurone AND this triggers the release of neurotransmitters; [1 mark]
(Neurotransmitter) diffuses across the gap between neurones / the synaptic cleft; [1 mark]
(Neurotransmitter) attaches/binds to (nicotinic acetylcholine) receptors on second/postsynaptic neurone membrane; [1 mark]
A nerve impulse is generated in the second/postsynaptic neurone AND is transmitted to the diaphragm; [1 mark]
Anatoxin is a neurotoxin thatis also known as ‘Very Fast Death Factor’ because when itis injected into mice itinduces
paralysis and death within a few minutes.
Anatoxin is similar in shape to the neurotransmitterthat usually binds to the nicotinic acetylcholine receptor.
Suggest how anatoxin can lead to death.
Anatoxin binds to (nicotinic acetylcholine) receptors and stops/blocks the neurotransmitter from binding; [1 mark]
Nerve impulses are not generated in the (second) neurone; [1 mark]
Lack of stimulation (by nerve impulses) means that muscle does not contract / is paralysed; [1 mark]
If the diaphragm does not contract then breathing stops (leading to death); [1 mark]
OR
Any three of the following:
Anatoxin binds to (nicotinic acetylcholine) receptors; [1 mark]
Anatoxin triggers an impulse in the (second) neurone; [1 mark]
Anatoxin is not broken down by the enzyme (that usually breaks down the neurotransmitter); [1 mark]
Constant stimulation (by nerve impulses) causes muscle to contract continously/without stopping; [1 mark]
If the diaphragm continually contracts then breathing stops (leading to death
Suggest an explanation forthe results shown in part(a)forthe mice on a high-fat diet.
The mice are not producing as much insulin / are not responding to the insulin that they are producing / are producing non-functioning insulin; [1 mark]
The mice are developing diabetes; [1 mark]
The glucose is remaining in the blood instead of being taken up by/into the cells; [1 mark]
More glucose enters the blood SO it takes longer for the cells to take up all the glucose / the cells do not need all of the glucose / the glucose will be removed from the body in the urine; [1
1000 µm = — mm
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