Lecture 4 - Nucleic Acids (DNA & RNA)

* has the canvas quiz in here

What is the difference between ribose and deoxyribose sugars?

Ribose has a 2'-OH group; deoxyribose does not.

Which type of bond connects nucleotides in a DNA or RNA strand?

Phosphodiester bonds

Which nitrogenous bases are classified as purines(double rings)?

Adenine and guanine (A and G)

What feature of DNA’s structure provides its stability?

The lack of a 2'-OH group

What is the significance of the antiparallel arrangement of DNA strands?

it stabilizes the helical structure through hydrogen bonds.

It helps in the replication process.

 It allows for the complementary base pairing.

In RNA, what type of bond forms the secondary structure, such as hairpins?

Hydrogen bonds

Which statements accurately describe the differences between DNA and RNA?

RNA contains ribose sugar; DNA contains deoxyribose sugar.

DNA uses thymine; RNA uses uracil.

What are the Nucleic Acids?

Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)

(polymers)

What are the three different Nucleotides?

Phosphate group

Five-carbon sugar

Nitrogeneous base

What does a purine Nitrogenous base contain?

Adenine, Guanine

What does a pyrimidine (single-ring) Nitrogenous base contain?

Cytosine, Thymine (DNA), Uracil (RNA)

What does DNA lack in it’s five-carbon sugars?

Lack of -OH in space 2 (2’)

What do RNA and DNA five-carbon sugars share?

-OH in space 3 (3’)

What does a condensation reaction require/produce?

requires energy

Produces H2O

What are the bonds the backbone of an DNA/RNA called?

Sugar-phosphate bond, bonds of Phosphodiester

What is the kind of bond that the hairpins/ladders within an RNA/DNA are held together with?

Hydrogen Bond

Polymerization of Nucleic acids

• synthesis that requires energy and enzyme catalysis

• Phosphorylation → transfer of one more phosphate group to a substrate molecule (raises PE)

• Two phosphates are transferred to the nucleotide

• creates a nucleoside triphosphate (NTP)

What are other eneergy carrieres that are NOT ATP?

CTP, GTP, TTP, UTP

Erwin Chargaff’s Rules

1) # of Purines = # pyrimidines

2) Total A = Total T Total C = Total G

What did Watson and Crick establish?

1) Structure is a double helix

2) DNA strands are antiparallel

• hydrophilic sugar phosphate backbone (the strings)

• Nitrogenous bases face the interior as pairs (ladder)

• stabilized by hydrogen bonds (inside)

  3) Purines always pair with pyrimidines due to the space inside the sugar phosphate backbone

• (Guanine - Cysteine) (Adenine, Thymine)

  4) DNA has a major groove and a minor groove

Which complementary base pair has three hydrogen bonds?

Guanine - Cysteine

Which complementary base pair has two hydrogen bonds?

A - T

Complementary

- provides a simple mechanism for DNA replication​

- each strand can serve as a template for the synthesis of anew complementary strand

DNA replication

Step 1 - separation of the double helix​

​

Step 2 - free deoxyribonucleotide forms hydrogen bondswith complementary base on the original strand​

- original strand is termed template strand​

- new strand is termed complementary strand​

​

Step 3 - polymerization of new subunits to growing strand(through phosphodiester bonds)​

What is the Structure of DNA?

1) two antiparallel strands twisted in a double helix​

​

2) stabilized by:​

​

a) hydrogen bonding between base pairs​

i) A-T (two bonds)​

ii) C-G (three bonds)​

​

b) interactions between hydrophobic bases in core​

​

3) further stabilized due to lack of 2′-OH group on nucleotides (more resistant to cleavage)

What is the structure of RNA? When is its Tertiary structure formed?

- contains sugar-phosphate backbone​

- formed by phosphodiester linkages​

- four nitrogenous bases extend from backbone​

​

RNA tertiary structure:​

- forms when secondary structure folds into more complex shapes

What is the difference between RNA structure and DNA structure?

RNA uses Uracil instead of Thymine

RNA has ribose, not deoxyribose

What are the Types of RNA? What are their roles?

a) messenger RNA (mRNA)​

- protein-encoding transcripts​

- sent to ribosomes to be translated into protein​

​

b) ribosomal RNA (rRNA)​

- complex with proteins to form subunits of the ribosome​

​

c) transfer RNA (tRNA)​

- carriers of amino acids during protein synthesis​