This document discusses the building blocks of DNA. It explains that nitrogenous bases attach to sugars to form nucleosides, and that nucleosides become nucleotides when a phosphate group attaches to the nucleoside. Specifically, it provides the examples of adenosine, guanosine, cytosine, and thymidine becoming nucleotides. The document also notes that adding more phosphate groups to a nucleotide, such as one, two, or three phosphates, produces adenosine monophosphate, diphosphate, and triphosphate respectively, with the latter being an energy-rich compound known as ATP.

1. DNA
part 2
Prep by : MOHAMED ABDUKADIR
KALIF
MPHIL in optometry

2. nucleosides
• When nitrogenous bases are attached with
sugar then it is called nucleosides.

4. When nitrogenous base of adenine
binds with sugar it becomes adenosine

5. When nitrogenous base of guanine is
fused with sugar it becomes guanosine

6. When nitrogenous base of cytosine is
fused with sugar it becomes cytadine

7. When nitrogenous base of thymine is
fused with sugar it becomes thymidine

8. nucleotides
• To make DNA we need to change the
nucleoside into nucleotide
• When nucleoside is attached with phosphate
then it is called nucleotides .
• The phosphate is attached in carbon position
number 5

10. • Phosphates are energy molecules , when more
phosphate is attached in a molecule it
energizes the molecule

11. So this is a chain of nucleotides

12. When Adenosine is having one
phosphate , then it is called Adenosine
monophosphate

13. When Adenosine is having two
phosphates , then it is called
Adenosine diphosphate

14. When Adenosine is having three
phosphates , then it is called
Adenosine triphosphate , and this
molecule is also called ATP
(ADENOSINE TRIPHOSPHATE), this
molecule is energy rich compound

15. • When guanine is attached with three
phosphates it becomes G.T.P , cytosine
becomes C.T.P , and thymine becomes T.T.P
• So we can say nucleotide may be
monophosphate , diphosphate , or
triphosphate .

16. • To be continued