• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

A level Biology: Post your doubts here!

qwertypoiu

qwertypoiu

Messages
924
Reaction score
1,096
Points
153
nehaoscar said:
View attachment 53236
why won't 3 and 4 occur?
Click to expand...
Note that it says TWICE.
During transcription:
1. DNA double helix unwinds... (bonds broken between complementary bases) [first BREAK]
2. Free ribosomal nucleotides pair with complementary bases of one DNA strand, to form mRNA (bonds form between complementary bases) [first FORM]
3. These free nucleotides are joined up by RNA polymerase... (sugar-phosphate bond formed)
4. mRNA has to leave now... so bonds between the strand of DNA and mRNA between complementary bases now have to break. [second BREAK]
5. The two strands of DNA now have to join up back together. Bonds will form between complementary bases of the two strands. [second FORM]
 
nehaoscar

nehaoscar

Messages
1,318
Reaction score
1,374
Points
173
qwertypoiu said:
Note that it says TWICE.
During transcription:
1. DNA double helix unwinds... (bonds broken between complementary bases) [first BREAK]
2. Free ribosomal nucleotides pair with complementary bases of one DNA strand, to form mRNA (bonds form between complementary bases) [first FORM]
3. These free nucleotides are joined up by RNA polymerase... (sugar-phosphate bond formed)
4. mRNA has to leave now... so bonds between the strand of DNA and mRNA between complementary bases now have to break. [second BREAK]
5. The two strands of DNA now have to join up back together. Bonds will form between complementary bases of the two strands. [second FORM]
Click to expand...
Ok i know that there isn't a option in the abcd choices but number 4
- don't the free nucleotides also pair up twice? :p
 
qwertypoiu

qwertypoiu

Messages
924
Reaction score
1,096
Points
153
nehaoscar said:
View attachment 53237
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.
 
H

hizirofaki

Messages
56
Reaction score
9
Points
8
K i got everything
BUT how did u get 4 eyepiece gracticule ?
the eyepiece graticule is thesmall scale right isit 77 something like that
 
You must log in or register to reply here.
Top