Physics, Chemistry and Biology: Post your doubts here!

[Awesome12]

yeah i'm aware of that, but still i think that the reason should be related to endo and exo reactions. if not plz expand on ur point of view.

The endo and exo things are not even given. We can't assume that. And not every reaction has a forward reaction that is endo, and the backward reaction being exo. It can be the vice versa as well

 

[Heba A.Moety]

The endo and exo things are not even given. We can't assume that. And not every reaction has a forward reaction that is endo, and the backward reaction being exo. It can be the vice versa as well

yeah it is true i just assumed based on the case. which year is this let me check the marking scheme?

 

[Heba A.Moety]

Q2 part c
this should do for part c(i)
in c(ii)the answer should be that both contain a double bond. this is because a double bond characterize unsaturated alkenes as it can be broken to single bonds and more hydrogen atoms can be attached.


for ques 5 i think u hsould measure the distence between base line and spot(X) and then divide this by distance moved by solvent (solvent front) from base line.check i think u should get the answer.

 

[Phoenix Blood]

Why does the xylem die, when initially it was a living tissue?

 

[Phoenix Blood]

Ofcourse, phloem transports amino acids and sucrose up to down (leaf to roots and growing and storage organs) , but sometimes, why does it transport food substances upwards, apart from tubers sending up their foodstore?

 

[Phoenix Blood]

Why are stomata mostly located on the underside of the leaf, as in most dicots?

 

[Phoenix Blood]

Where does respiration in a plant cell actually occur- chloroplasts or miochondria? How are they related?

 

[Phoenix Blood]

Briefly just please explain what's plasmolysis.

 

[Karim Nabil]

Phoenix Blood >>well i finished bio ol and currently AS student but i can help you though

1. xylem dies and its protoplasm(cell content) disintegrates to decrease resistance to water and minerals conducted, its also has cell wall made of lignin which provides support for the xylem tissue because water moved with strong forces such as transpiration pull and cohesion forces
2. phloem sieve tubes unload sucrose from source to sink , sugars(sucrose) made by photosynthesis and then transported to the sink cells whether it is upward or downward depending on the concentration gradient
3. stomata mostly located on the underside of the leaf beacuse plants under direct sunlight would constantly have their stomata open and would thus lose much water and the plant dies.
   
4. respiration occurs in mitochondria where glucose provided by photosynthesis from chloroplasts is oxidised/respired to produce energy(in the form of ATP)
5. plasmolysis is the pulling away of cytoplasm from the cell wall, this occur if plant cell is placed in a higher concentrated solution, as a result cell became flaccid

 

[ZohaKhan]

gt it

 

[ManalMansoor]

Please help me with Organic chemistry guys, I need it.
Any notes, or tips would do please!

 

[Awesome12]

Please help me with Organic chemistry guys, I need it.
Any notes, or tips would do please!

Specifically what?

 

[Heba A.Moety]

Why are stomata mostly located on the underside of the leaf, as in most dicots?

1) The number of stomata (not stomatas) on the upper surface is drastically reduced as the upper leaf surface receives more intense and direct sunlight and tends to lose more water from that surface.

2) This is compensated by increasing the stomata quantity on the lower surface

3) The internal leaf structure is accordingly adapted for more photosynthesis (Palisade nearer the upper surface for efficient photosynthesis and loosely arranged spongy parenchyma for good gaseous exchange.

4) In drought prone areas the stomata are entirely absent from the upper surface and the epidermis is thickly circularized to reduce transpiration.( Eucalyptus and Cycas )

5) In extreme desert condition, the leaves are totally dispensed and the stem is a phylloclade (See Cacti.)
Source:
Botanist

 

[Phoenix Blood]

1) The number of stomata (not stomatas) on the upper surface is drastically reduced as the upper leaf surface receives more intense and direct sunlight and tends to lose more water from that surface.

2) This is compensated by increasing the stomata quantity on the lower surface

3) The internal leaf structure is accordingly adapted for more photosynthesis (Palisade nearer the upper surface for efficient photosynthesis and loosely arranged spongy parenchyma for good gaseous exchange.

4) In drought prone areas the stomata are entirely absent from the upper surface and the epidermis is thickly circularized to reduce transpiration.( Eucalyptus and Cycas )

5) In extreme desert condition, the leaves are totally dispensed and the stem is a phylloclade (See Cacti.)
Source:
Botanist

Phoenix Blood >>well i finished bio ol and currently AS student but i can help you though

1. xylem dies and its protoplasm(cell content) disintegrates to decrease resistance to water and minerals conducted, its also has cell wall made of lignin which provides support for the xylem tissue because water moved with strong forces such as transpiration pull and cohesion forces
2. phloem sieve tubes unload sucrose from source to sink , sugars(sucrose) made by photosynthesis and then transported to the sink cells whether it is upward or downward depending on the concentration gradient
3. stomata mostly located on the underside of the leaf beacuse plants under direct sunlight would constantly have their stomata open and would thus lose much water and the plant dies.
   
4. respiration occurs in mitochondria where glucose provided by photosynthesis from chloroplasts is oxidised/respired to produce energy(in the form of ATP)
5. plasmolysis is the pulling away of cytoplasm from the cell wall, this occur if plant cell is placed in a higher concentrated solution, as a result cell became flaccid

Thank you!!

 

[Phoenix Blood]

What's a receptacle?

 

[Phoenix Blood]

The embryo turns into a seed or a fruit? Pertaining to this, what are the endosperm and the cotyledon? Cotyledon is the food store or leaf?

 

[Awesome12]

What's a receptacle?

The part below the sepals. The cells in this region reproduce mitotically (usally comes in MCQs)

 

[Phoenix Blood]

What's the difference between a vegetarian and a vegan?

 

[Awesome12]

The embryo turns into a seed or a fruit? Pertaining to this, what are the endosperm and the cotyledon? Cotyledon is the food store or leaf?

None. The ovary becomes the seed. The ovary wall becomes the fruit. The endosperm is formed from the endosperm nucleus. Cotyledon is the food store

 

[Phoenix Blood]

What happens when the
(a) atria
(b) ventricles

contract and relax?