March Mock Quick Revision Flashcards
What is the test for starch?
Few drops of iodine solution
What is the test for reducing sugars (glucose)?
- add equal volume of Benedict’s solution and mix
- heat in a 95˚C water bath for few minutes
What is the test for proteins?
Biuret Test
- add equal volume of 0.1mol/dm^3 potassium hydroxide solution and mix
- add few drops of 0.01mol/dm^3 copper sulfate solution and mix
What is the test for fats/ lipids?
- add equal volume of ethanol, and shake thoroughly
- add water
What is a positive test for starch (iodine solution)?
Yellow/ orange —> blue/ black
What is a positive test for reducing sugars (glucose) (Benedict’s test)?
Blue —> green —> orange —> red (depending on how much sugar present)
What is a positive test for protein (biuret test)?
Pale blue —> pale purple
What is a positive test for fats (lipids) (ethanol emulsion test)?
Clear —> cloudy
What is Fick’s Law?
Rate of diffusion ∝ (surface area x concentration difference) / thickness of membrane
What is transpiration?
The movement of water through and out of the plant (xylem)
What is translocation?
The movement of sugars and other chemicals/ sap (amino acids, sucrose, water) - (assimilates) made by the plant cells along the phloem (direction depends on time of year)
Which direction does translocation occur (dependent on time of year)
Down in summer
Up in spring
What is the main assimilate in translocation?
Sucrose - plant makes glucose but turns it into sucrose
What waterproofs the xylem?
Lignin
What is in between the phloem cells?
Sieve tube elements - porous cell walls so nutrients (cell sap) can flow between them
What is a source and sink?
Sugars (in phloem tubes) move from a source to a sink.
Source - where sucrose is released into the phloem (where it is made)
Sink - where sucrose is removed / used up from the phloem (where it is used)
How are companion cells adapted to their function (in phloem)?
Lots of mitochondria
What can be used to measure transpiration?
Potometer (rate is the speed the bubble moves across the tube)
How does water get from the soil to the roots?
Through osmosis (root hair cells —> enlarge SA + cellulose in cell walls help absorb water)
What is significant about the spongy mesophyll layer?
It has lots of gaps so carbon dioxide can easily diffuse through
Where are the stomata?
In the lower epidermis layer
Where does most photosynthesis occur?
Palisade mesophyll - palisade cells contain lots of chloroplasts
What is significant about the upper epidermis?
The epidermal tissue is almost transparent to let light in for photosynthesis
How does a leaf reduce water loss?
- waxy cuticle on top (thin layer of lipids)
- keep stomata open for as little time possible (guard cells)
