MGS 2022 Flashcards
Due to the difference in the concentration of salt inside the cell and the surrounding freshwater, the Stentor absorbs water from its surrounding, then discharges it by regular contractions of the contractile vacuole.
Explain the process of how water enters the Stentor. [2]
- Water molecules enter the cell through osmosis by passing through the partially permeable membrane of the cell membrane;
- The surrounding freshwater has a higher water potential than the water potential of the contractile vacuole / cytoplasm inside the cell;
Due to the difference in the concentration of salt inside the cell and the surrounding freshwater, the Stentor absorbs water from its surrounding, then discharges it by regular contractions of the contractile vacuole.
Explain the importance of controlling the water potential of the Stentor living in a
freshwater environment. [2]
- If water potential of freshwater env. is too high, water molecules will enter
the Stentor; - Stentor would expand/ swell and eventually burst;
Many used terms such as flaccid/
plasmolysed/turgid to describe the Stentor but it is not a plant cell.
The Stentor was taken from its freshwater habitat and placed in a saltwater
aquarium.
Explain what will happen to the Stentor in the saltwater aquarium after 2 days. [2]
- Water molecules will move out of the cytoplasm of the Stentor into the saltwater + by osmosis;
- It would shrink / crenated (eventually dying).
Certain fruits contain biological molecules that prevent the solidification of a protein-
based jelly when it is cooled. Protein-based jelly exits in liquid state at high temperature but becomes solid when it is cooled.
An experiment was conducted to investigate the presence of these biological molecules
in fruits.
Bowl 1 is the control setup. Explain the purpose of Bowl 1.
Bowl 1 is a control set up to show that the fruits contains a biological molecule / enzyme that prevented the jelly from solidifying.
Certain fruits contain biological molecules that prevent the solidification of a protein-
based jelly when it is cooled. Protein-based jelly exits in liquid state at high temperature but becomes solid when it is cooled.
An experiment was conducted to investigate the presence of these biological molecules
in fruits.
Bowl 2 contains a pineapple slice while bowl 4 contains crushed pineapple.
Explain the observation for the different textures of jelly between Bowls 2 and 4. [2]
- Crushing the pineapple increased the surface area to volume ratio / More exposed surface area between the crushed pineapple and jelly ;
- This increased the rate of diffusion of the biological molecule out of the
fruit ;
The rate of photosynthesis is affected by the colour of light. The colour of light is
a limiting factor.
Using the colour of light, explain the term limiting factor.
The rate of photosynthesis will increase or decrease when there is a change in the colour of light used.;
OR
A specific coloured light / (wavelength of the light) will either increase or decrease the rate of photosynthesis;
Discuss the advantage of using 5% sodium hydrogen carbonate solution instead of distilled water in an experiment investigating the effect of different colours of light on the rate of photosynthesis. [2]
- The amount of dissolved carbon dioxide will be higher than in distilled water ;
- So that the concentration of carbon dioxide is not a limiting factor in this set up ;
Describe how urea in the blood enters the nephrons and is removed through the
renal pelvis. [3]
- The diameter of the lumen of the afferent arteriole is larger than the efferent arteriole. + This generate a high hydrostatic pressure at the
glomerulus. ; - Urea is forced through the glomerulus wall and basement membrane by ultra-filtration ;
- and are collected in the bowman’s capsule and collecting duct. ;
Adam’s response to the fire alarm is NOT a reflex action.
Give one reason for this statement. [1]1
Adam can choose (use of conscious will) to remain in the classroom or to sprint to the car park.thus it is a voluntary action
mostly correct by saying it is a voluntary action / it is a decision etc
Thalassemia is an inherited blood disorder that occurs when there is a defect in the haemoglobin protein molecule in red blood cells. It is inherited as a recessive allele and results in an abnormal form of haemoglobin.
Suggest how this defect may have come about and explain how this results in an abnormal form of haemoglobin. [2]
- This defect could have been brought about by (random) gene mutations ;
- This mutation results in a change in the DNA nucleotide sequence, leading to + change in the polypeptide chain affecting the haemoglobin
molecule formed.
Name processes H (respiration), I (Photosynthesis) and J (Combustion of fossil fuels) and explain how each one affects the concentration of carbon dioxide in the atmosphere.
In your answers, identify two carbon sinks and use the information in Fig. 11.1 to support your answer. [5]
- H: respiration of living organisms (producers and consumers) releases carbon dioxide into the air and + increases the carbon dioxide concentration into the atmosphere.
- I: Photosynthesis removes carbon dioxide from the air and hence + reduced carbon dioxide concentration in the air.
- J: Combustion of fossil fuels releases carbon dioxide into the air and hence + increase the concentration of carbon dioxide in the atmosphere.
- Carbon sinks: Fossil fuels (coal/oil/natural gas) buried deep underground
- Plants and trees in forests store carbon in the form of cellulose in cell walls and starch in leaves are rich sources of carbon sink.
Describe the process of fertilisation and outline the early development of the
embryo into a fetus. [6]
- Fertilisation is the fusion of the nucleic of the egg and the sperm to form the zygote.
- Zygote then undergoes a series of mitotic cell division / cell division to form a ball of cells known as the embryo.
- Implantation of embryo into the uterine lining with the formation of embryonic villi
- Formation of placenta for exchange of nutrients and oxygen into the fetus
- And removal of urea and carbon dioxide from the fetus to the maternal blood stream
- Formation of amniotic sac and amniotic fluid to protect the fetus from mechanical shock
- Presence of umbilical blood vessels (umbilical artery to remove carbon dioxide and urea to maternal blood stream) / umbilical veins to transport oxygen and nutrients to the fetus.
Discuss ways to create a balance between timber production and conservation
of the ecosystem. [5]
- Governments can also institute and enforce laws disallowing trees below a certain height from being cut down.
- Reforestation efforts can be made to replant and replenish trees that have been cut down for timber.
- Alternating areas of forests that can be cut down so there is sufficient time for parts of the forest to regrow naturally.
- Designating certain parts of the forest as conservation areas / national parks where the trees cannot be cut down for any commercial purposes.
- Planting of fast growing plants for use of timber Eg: pine tree
- Having alternative source of timber, Eg: rubber wood.
