Tuesday, October 21, 2008

Nucleic Acids-Informational Polymers

-The last group of important biological molecules we'll discuss is the nucleic acids. The two nucleic acids are DNA(deoxyribonucleic acid) and RNA(ribonucleic acid).

- DNA is the moecule of heredity. It is what is inherited from cell to cell, parent organism to offspring. DNA moleculesare very long; thay are polymers of nucleotide monomers. Nucleotides are made up of three parts: a nitrogenous base,a five carbon sugar called a pentose, and a phosphate group.

-There are two types of nitrogenous bases, purines, and pyrimidines. The purines are adenine(A), and guanine(G) and the pyrimidines are cytosine(C), Thymine(T), Uracil(U).

-Thymine is found ONLY in DNA, and uracil is found ONLY in RNA. In DNA, adenine always pairs with thymine, and cytosine always pairs with guanine.

*All Girls are Pure (A & G are Purines)*

*Hook-ups: A & T, C & G*

-4 groups of Amino Acids:
  • Polar- they can dissolve in water (-OH, O, SH)

  • Nonpolar- they do not dissociate (HC)

  • Acidic-(COO-)

  • Basic- Amine group with + charge

-In DNA,, the pentose sugar is deoxyribose, and in RNA, the pentose sugar is ribose. Deoxyribose has one less oxygen than ribose.

-In DNA and RNA, the nucleotides are joined by phosphodiester bonds. In DNA, two polynucleotide chains wrap around each other. In a helical shape, whereas RNA is a single polynucleotide.

-Size of the carbon skeleton varies from 3 to 7 carbons.

  • Trimose= 3

  • Pentose=5

  • Hexose=6


1. Each chromosome contains one long DNA molecule that usually carries how many genes?

A) One hundred

B) One Thousand

C) Several

2. When a cell reproduces itself by dividing, its DNA molecules are:

A)attached on to others

B) Copied & passed along

C)newly rebuilt into something different

3. What carries protein-coding instructions from DNA to protein-synthesizing machinery?


B) RNAC) Both

D) Neither

*Answers: 1. c, 2. b, 3. b

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