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A level Biology: Post your doubts here!

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Studydayandnight

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Guys! Explain this one please!

Correct answer is D.
 

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qwertypoiu

qwertypoiu

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Studydayandnight said:
Guys! Explain this one please!

Correct answer is D.
Click to expand...
When oxygen diffuses from the lung to the blood it passes through 5 membranes.

Once oxygen enters the air space inside alveolus, it:
  • Enters into squamous epithelium of alveolus.
  • Exits from the squamous epithelium of alveolus.
  • Enters into endothelial cells of capillaries.
  • Exits endothelial cell of capillary, to enter the lumen of capillary. (here is blood plasma)
  • Enter the red blood cell, to bind with one of the 200,000,000 haemoglobin molecules inside.
So that's five for oxygen. It is similar for carbon dioxide, except that it may travel by three modes. Some of it travels by actually binding with haemoglobin amine terminal (10%), others simply dissolve in blood plasma (5%), and most of them as HCO3- ions, dissolved in blood plasma (85%).
So depending on which situation arises, a CO2 molecule may or may not have to enter the red blood cell.
Therefore, for CO2, we say it may travel through 4 or 5 membranes.
 
qwertypoiu

qwertypoiu

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Studydayandnight said:
This one as well! Correct answer is D.
Click to expand...
For this question you simply have to identify energy that was converted into chemical energy in the form of glucose from the plant photosynthesising. All energy in glucose came from the sun originally after all.
So, the first three all do not fit into this category, because they remain as light or heat energy, and so were never used for photosynthesis.

Used for growth: yes, this fits, because for growth the energy first was turned into chemical energy in the form of glucose, then this glucose was used as an energy source. (perhaps first ATP was made before energy was used)

Used for other life processes: yep. Because all life processes that require energy happen in cells, and the source of this energy is always glucose.

Respiratory heat losses: one might think that this energy did not undergo photosynthesis, but you have to be careful! For a plant to lose energy through heat losses, it must have gained chemical energy, done respiration using this chemical energy, then lost some of THIS energy in heat. So this counts as well.

In other words we just look for energy that entered the plant and stayed, because the only way to stay as energy inside the plant is as chemical energy, by undergoing photosynthesis.

Adding those three energy quantities should get you D.
 
Jeezan

Jeezan

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Which type of cell will contain the highest proportion of single membrane bound structures ?
A - ciliated epithelial cell
B- goblet cell
C- RBC
D-smooth muscle cell

The answer is B
May i know the reason ?
 
qwertypoiu

qwertypoiu

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Jeezan said:
Which type of cell will contain the highest proportion of single membrane bound structures ?
A - ciliated epithelial cell
B- goblet cell
C- RBC
D-smooth muscle cell

The answer is B
May i know the reason ?
Click to expand...
Goblet cells produce a lot of mucus.
Mucus has glycoproteins in it, so to produce glycoprotein, the goblet cell needs endoplasmic reticulum.
To secrete the mucus produced, Golgi vesicles are involved to perform exocytosis.
ER, and Golgi apparatus are both single membrane bound structures, and is found in high proportion in goblet cells.
 
Jeezan

Jeezan

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qwertypoiu said:
Goblet cells produce a lot of mucus.
Mucus has glycoproteins in it, so to produce glycoprotein, the goblet cell needs endoplasmic reticulum.
To secrete the mucus produced, Golgi vesicles are involved to perform exocytosis.
ER, and Golgi apparatus are both single membrane bound structures, and is found in high proportion in goblet cells.
Click to expand...
Thank you :)
 
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