Nucleic Acids, DNA Replication, and ATP

Flashcards covering the roles and structures of DNA, mRNA, tRNA, rRNA, semiconservative DNA replication, the Meselson-Stahl experiment, and ATP synthesis/hydrolysis.

Role of DNA in Living Cells

The base sequence of genes codes for functional RNA and the amino acid sequence of polypeptides, determining inherited characteristics and influencing the structure and function of organisms.

Messenger RNA (mRNA)

A single-stranded, linear ribose polynucleotide containing uracil instead of thymine, with a codon sequence complementary to exons of $1$ gene from $1$ DNA strand that can be translated into a specific polypeptide by ribosomes.

Ribosomal RNA (rRNA)

A structural component of ribosomes that functions along with proteins.

Transfer RNA (tRNA)

A single strand of about $80$ nucleotides folded into a clover shape with paired bases, featuring an anticodon on one end that binds to a complementary mRNA codon and an amino acid binding site on the other.

Structure of DNA

A double helix composed of $2$ polynucleotide strands (deoxyribose) joined by hydrogen bonds between complementary purine and pyrimidine base pairs on opposite strands.

Purine Bases

$2$-ring nitrogenous bases, which include adenine (A) and guanine (G).

Pyrimidine Bases

$1$-ring nitrogenous bases, which include thymine (T), cytosine (C), and uracil (U).

Complementary Base Pairs in DNA

Specific base pairing formed by $2$ hydrogen bonds between adenine (A) and thymine (T), and $3$ hydrogen bonds between guanine (G) and cytosine (C).

Complementary Base Pairs in RNA

Specific base pairing formed by $2$ hydrogen bonds between adenine (A) and uracil (U), and $3$ hydrogen bonds between guanine (G) and cytosine (C).

DNA Structural Adaptations

Structural characteristics including a sugar-phosphate backbone and many H-bonds for stability, long length for information storage, compact helix for nucleus storage, triplet coding, double-stranded design for semi-conservative replication, and weak H-bonds that easily break for strand separation.

Semiconservative DNA Replication

The mechanism of DNA replication where original strands act as templates, producing new DNA molecules containing $1$ old strand and $1$ new strand.

DNA Helicase

An enzyme that breaks hydrogen bonds between complementary base pairs, unwinding and separating the two strands of DNA during replication.

DNA Polymerase

An enzyme that catalyses condensation reactions to join adjacent nucleotides on the new strand during DNA replication.

Meselson-Stahl Experiment

An experiment proving semiconservative replication by growing bacteria in heavy isotope $^{15}\text{N}$ medium, transferring them to light isotope $^{14}\text{N}$ medium, and using centrifugation to observe DNA density pellets after $1$ and $2$ replication cycles.

ATP Hydrolase

An enzyme that catalyses the hydrolysis of ATP ($\text{ATP} \rightarrow \text{ADP} + \text{P}_i$), releasing energy coupled to metabolic reactions and phosphorylating compounds to increase reactivity.

ATP Synthase

An enzyme that catalyses the condensation reaction between ADP and $\text{P}_i$ to resynthesise ATP during photosynthesis and respiration.

ATP as Cellular Energy Currency

Properties making ATP suitable for energy transfer, including high-energy phosphate bonds, releasing small amounts of energy at a time to minimise heat loss, single-step hydrolysis for rapid energy availability, and being readily resynthesised.