Nucleotides and Nucleic Acids

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Questions and Answers

What are the three parts of a nucleotide?

Sugar, protein, phosphate backbone

Sugar, lipid, base

Sugar, base, phosphate backbone (correct)

Base, lipid, phosphate backbone

What makes up a nucleoside?

Phosphate and lipid

Sugar and base (correct)

Base and phosphate

Sugar and phosphate

Which of the following functions is NOT associated with nucleotides?

Energy for metabolism

Enzyme cofactors

Transmission of genetic information (correct)

Signal transduction

Which type of bond links nucleotide subunits together?

Phosphodiester bonds Signup and view all the answers

Which base pairs with adenine in DNA?

Thymine Signup and view all the answers

What forms the sugar-phosphate backbones of DNA strands?

Sugars and phosphates Signup and view all the answers

What is the function of the PolyA tail on mRNA?

Stabilises mRNA Signup and view all the answers

Which type of RNA has the greatest relative amount in cells involved in protein synthesis?

Ribosomal RNA (rRNA) Signup and view all the answers

Which component is part of the 50S subunit of the bacterial ribosome?

23S rRNA Signup and view all the answers

What is the molecular weight (Mr) of the eukaryotic 40S ribosomal subunit?

1.4 x 10^6 Signup and view all the answers

Which RNA type adapts amino acids to the codons in mRNA?

Transfer RNA (tRNA) Signup and view all the answers

Which structural form does RNA adopt when it forms a helix?

A-form Signup and view all the answers

Which statement is correct about ribosomes?

They are the 'protein factories' of the cell. Signup and view all the answers

What is the role of transfer RNA (tRNA) in the cell?

Acts as a translator between nucleic acid and protein worlds Signup and view all the answers

Which of the following RNAs is not directly involved in protein synthesis?

Small interfering RNA (siRNA) Signup and view all the answers

What are the components of a eukaryotic mRNA molecule?

Cap structure, poly(A) tail, coding region Signup and view all the answers

Which of the following is part of tRNA structure?

Acceptor stem Signup and view all the answers

Which of the following is NOT a characteristic of RNA structure?

Forms B-form helix Signup and view all the answers

Study Notes

Nucleotides

A nucleotide consists of three parts: sugar, base, and phosphate backbone.
Nucleosides are nucleotides without a phosphate group.

Nucleic Acids

DNA and RNA are polymers of nucleotides.
DNA and RNA have different functions:
- Storage of genetic information (DNA)
- Transmission of genetic information (mRNA)
- Processing of genetic information (ribozymes)
- Protein synthesis (tRNA and rRNA)
- Regulation of expression (siRNA and miRNA)

Functions of Nucleotides and Nucleic Acids

Nucleotides have various functions:
- Energy for metabolism (ATP)
- Enzyme cofactors (NAD+)
- Signal transduction (cAMP)
Nucleic acids have various functions:
- Storage of genetic information (DNA)
- Transmission of genetic information (mRNA)
- Processing of genetic information (ribozymes)
- Protein synthesis (tRNA and rRNA)
- Regulation of expression (siRNA and miRNA)

Helical Structure of DNA

DNA consists of two chains of nucleotides coiled around each other in a right-handed double helix.
Sugar-phosphate backbones of the two strands spiral around the outside of the helix.
Nitrogenous bases extend into the centre at right angles to the axes of the helix.

Nucleotide Linkage

Nucleotide subunits are linked together by phosphodiester bonds.

Hydrogen Bonding Between Base Pairs

Hydrogen bonding is a non-covalent attraction that aids in maintaining the double helix structure.
Adenine forms 2 H bonds with thymine (A=T).
Cytosine forms 3 H bonds with guanine (G=C).
This H bonding pattern is called base pairing.

RNA Types Involved in Protein Synthesis

Ribosomal RNA (rRNA): 80%, range: 120-5070 nucleotides.
Transfer RNA (tRNA): 15%, 75 nucleotides.
Messenger RNA (mRNA): varies, varies.

RNA Structure

RNA is intrinsically single-stranded.
RNA cannot form a B-form helix due to a bulky 2'-OH.
When helical, RNA adopts an A-form geometry.
RNA has a deep and narrow major groove and a wide minor groove.
Secondary structure is observed in rRNA and tRNA, and assumed to be in mRNA.

Messenger RNA (mRNA)

mRNA carries the instructions for building a protein.

Types of RNA Molecules

Messenger RNAs (mRNAs): intermediates that carry genetic information from DNA to the ribosomes.
Transfer RNAs (tRNAs): adaptors between amino acids and the codons in mRNA.
Ribosomal RNAs (rRNAs): structural and catalytic components of ribosomes.
Small interfering RNAs (siRNA): RNA interference (RNAi).
Long non-coding RNAs (long ncRNAs): transcription.
MicroRNAs (miRNAs): RNA interference (RNAi).
Ribozymes: RNA enzymes.

Eukaryotic mRNA

Eukaryotic mRNA is capped at the 5' end.
The 3' end is polyadenylated.
PolyA tail is not coding.
It is added after transcription.
It stabilizes mRNA.
Removal of polyA degrades RNA and inhibits translation.

Ribosomes

Bacterial ribosome: Mr 2.7 x 106, 50S and 30S subunits.
Eukaryotic ribosome: Mr 4.2 x 106, 60S and 40S subunits.

Ribosomal RNA (rRNA)

rRNA is complex and makes up the ribosomes.
Ribosomes are the "protein factories" and are composed of many proteins and rRNA molecules.

Transfer RNA (tRNA)

tRNA acts as a translator between the nucleic acid and protein worlds.
tRNA structure includes:
- Acceptor stem
- Anticodon stem
- 5' end
- 3' end
- Anticodon
- Amino acid

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Description

Understanding the structure and functions of nucleotides and nucleic acids, including DNA and RNA. Learn about the components of nucleotides, nucleosides, and their roles in metabolism and genetic information.