Nucleotides and RNA Structure

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Questions and Answers

How are nucleotides in DNA joined together?

Through hydrolysis reactions breaking phosphodiester bonds

By removing a hydrogen atom from the 3′ carbon of one nucleotide

By removing a hydroxyl group from the 5′ carbon of another nucleotide

Through dehydration synthesis reactions forming phosphodiester bonds (correct)

Who worked together to determine the structure of DNA in the 1950s?

Rosalind Franklin and Francis Crick

Linus Pauling and Maurice Wilkins

James Watson and Linus Pauling

Francis Crick and James Watson (correct)

Which technique did Rosalind Franklin use to understand the structure of DNA?

Crystallography

Nuclear magnetic resonance imaging

Electron microscopy

X-ray diffraction methods (correct)

Why were Nobel Prizes not awarded posthumously to individuals like Rosalind Franklin?

Because the rules of the Nobel Prize do not allow it Signup and view all the answers

Which of the following scientists discovered the secondary structure of proteins using X-ray crystallography?

Linus Pauling Signup and view all the answers

What did Watson and Crick base their understanding of DNA structure on?

Franklin’s X-ray diffraction data Signup and view all the answers

What is the main function of mRNA in the cell?

Directing protein synthesis Signup and view all the answers

Which nucleotide is found in RNA but not in DNA?

Uracil (U) Signup and view all the answers

What type of bond links nucleotides in RNA?

Phosphodiester bond Signup and view all the answers

In RNA, what replaces deoxyribose sugar found in DNA?

Ribose sugar Signup and view all the answers

What is the function of microRNA (miRNA) in the cell?

Regulating gene expression by silencing specific mRNAs Signup and view all the answers

What happens if a cell requires a certain protein to be synthesized?

The gene is turned on and complementary mRNA is synthesized Signup and view all the answers

What type of carbon-nitrogen ring do cytosine, thymine, and uracil have?

A single carbon-nitrogen ring Signup and view all the answers

What is attached to the 1' carbon of each nucleotide?

Nitrogenous base Signup and view all the answers

What type of sugar is found in RNA?

Ribose Signup and view all the answers

What is the function of phosphodiester linkages in nucleic acids?

Forming covalent bonds between adjacent nucleotides Signup and view all the answers

What is the directionality of nucleic acids?

They are added to the 3' end Signup and view all the answers

What is the missing atom in deoxyribose sugar that gives DNA its name?

Oxygen Signup and view all the answers

What are the macromolecular components of most enzymes made of?

Protein Signup and view all the answers

Which type of enzymes catalyze reactions in their own bonds or among other RNAs?

Ribozymes Signup and view all the answers

What happens to an enzyme's structure upon heating?

It denatures and loses activity Signup and view all the answers

What is the primary function of enzymes in the circulatory system?

Regulating blood clotting Signup and view all the answers

What is the typical size of enzymes compared to their substrates?

Larger Signup and view all the answers

Which part of the enzyme structure is involved in catalysis?

A small section next to the binding sites Signup and view all the answers

What is the term for the temperature at which an enzyme shows its maximum activity?

Optimum temperature Signup and view all the answers

What happens to enzymes when exposed to temperatures beyond their optimum?

They lose their 3D shape Signup and view all the answers

What is the term for the point at which all enzymes added are occupied by substrate molecules?

Substrate saturation Signup and view all the answers

What is the term for a chemical that binds to the active site of an enzyme and inhibits its activity?

Inhibitor Signup and view all the answers

What is the typical optimum pH range for enzymes?

5-7 Signup and view all the answers

What happens to enzyme activity when the temperature drops below its optimum?

It decreases Signup and view all the answers

Study Notes

Nucleic Acids

Dehydration synthesis reactions form nucleic acids by removing a hydroxyl group from the 3′ carbon of one nucleotide and a hydrogen atom from the hydroxyl group attached to the 5′ carbon of another nucleotide, producing water and a phosphodiester bond.

Structure of DNA

James Watson and Francis Crick determined the structure of DNA in the 1950s using X-ray diffraction data from Rosalind Franklin.
DNA is a double helix structure consisting of nucleotides linked by phosphodiester bonds.

RNA

Ribonucleic acid (RNA) is involved in protein synthesis and is composed of nucleotides linked by phosphodiester bonds.
RNA contains ribose sugar instead of deoxyribose and uracil (U) instead of thymine (T).
RNA is usually single-stranded, but internal base pairing creates a 3D structure essential for function.

Types of RNA

messenger RNA (mRNA) carries genetic code from DNA.
ribosomal RNA (rRNA) is involved in protein synthesis.
transfer RNA (tRNA) brings amino acids to the ribosome.
microRNA (miRNA) regulates gene expression.

Structure of Nucleotides

Nucleotides consist of a pentose sugar, a nitrogenous base, and a phosphate group.
The carbon atoms of the pentose sugar are numbered as 1′, 2′, 3′, 4′, and 5′.
In RNA, the pentose sugar is ribose, which has a hydroxyl group attached to the 2′ carbon.
In DNA, the pentose sugar is deoxyribose, which has a hydrogen atom attached to the 2′ carbon.

Phosphodiester Linkages

Phosphodiester linkages are covalent bonds between the 3′ carbon of one nucleotide and the 5′ phosphate group of another.
Nucleic acids have directionality, with the first nucleotide having a free phosphate group at the 5′ end and the last nucleotide having a free 3′ hydroxy group.

Enzymes

Enzymes are proteins that catalyze reactions in metabolic pathways.
Enzymes are found in all tissues and fluids of the body.
Enzymes have a specific structure, which determines their catalytic activity.
Enzymes require an optimum temperature and pH for their action.
The sequence of amino acids in an enzyme specifies its structure and function.

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Description

Explore the structure of nucleotides and RNA, including the classification of bases as purines and pyrimidines, the numbering of carbon atoms in pentose sugar, and the differences between DNA and RNA sugars. Test your knowledge on the components of nucleotides in this quiz!