Nucleic acids and their functions Flashcards
- Draw simple labelled diagram to show the structure of a nucleotide.
Phosphate group
Pentose sugar
Nitrogenous base
- What are the components of ATP?
Adenine
Ribose
3 Phosphate ions
- What is the difference between and endergonic and exergonic reaction?
Endergonic takes in more energy than in releases.
Exergonic reaction releases more energy than it takes in
- How much energy is released from one mole of ATP when it is hydrolysed to ADP and Pi?
30.6KJ of energy is liberated per mole of ATP
- What does “universal energy currency” mean?
All speicies of organisms use ATP to provide energy
- List 3 advantages of using ATP to provide energy in cells.
- It releases smaller amounts of energy, so it is more manageable.
- ATP to ADP is a one-step reaction, whereas glucose is many steps.
- ATP can be transported across organelle membranes easily.
- What is the sugar in DNA?
- Deoxyribose (pentose sugar)
- Which bases are in the nucleotides of DNA?
Adenine
Thymine
Guanine
Cytosine
- What is the sugar in RNA?
Ribose
- What are the bases in RNA?
Adenine
Uracil
Cytosine
Guanine
- How does the structure of ATP differ from that of DNA?
ATP has ribose sugar instead of deoxyribose
ATP has 3 phosphate groups attached rather than 1 in DNA
ATP only has adenine bases whereas DNA has adenine, thymine, guanine and cytosine.
- How does the structure of ATP differ from that of RNA?
ATP has 3 phosphate groups attached rather than 1 in RNA
ATP only has adenine bases, whereas DNA has adenine, uracil, guanine and cytosine.
- What does DNA stand for?
Deoxyribonucleic acid
- What does RNA stand for?
Ribonucleic acid
- What are the two functions of DNA?
Protein Synthesis and Replication
- What are the three types of RNA?
messenger RNA (mRNA)
transfer RNA (tRNA)
ribosomal RNA (rRNA)
- Which is longer DNA or RNA.
DNA
- Which bases are pyrimidines and which are purines?
As Pure as Gold
Purine: Adenine and Guanine (hex + pent rings)
Pyrimidine: Cystosine, Thymind, Uracil (single hex ring)
- Which are the complementary base pairs in DNA and RNA?
DNA:
Adenine = Thymine
Guanine ≡ Cytosine
RNA:
Adenine = Uracil
Guanine ≡ Cytosine
- Complementary bases are linked by bonds what type of bonds are these?
Hydrogen bonds
- What does antiparallel mean?
One strand of DNA runs in the 5’ to 3’ direction, whilst the other strand runs antiparallel 3’ to 5’.
- What is the shape of DNA?
Double Helix
- Why does DNA replication need to happen?
So that daughter cells contain identical genetic material as the parent cell—inheritance to next generation.
- During which part of the cell cycle does DNA replication take place?
Growth phase
- What is the accepted model of DNA replication called?
Semi-conservative replication
- What does semi-conservative replication mean?
One strand of the parental DNA acts as a template strand during replication, so that only half of the old DNA is conserved.
- What is the enzyme that catalyses DNA replication?
DNA polymerase
- Which two scientists undertook the experiment that showed how DNA replication happens?
Meselson and Stahl
- Which part of the DNA molecule was labelled in the experiment?
Nitrogenous bases
- What were they labelled with?
Heavy Nitrogen isotope (15N)
- Draw the results for generation 0 1 and 2 labelling the lines on the tubes.
Generation 0 is only a light band.
Gen 1: 100% intermediate band
Gen 2: no light band, 50% intermediate band, 50% heavy band
- How do these results show that conservative and dispersive replication do not happen?
If it were conservative there would be a constant light band and only a heavy band, no intermediate band.
If it were dispersive gen 2 would not have a heavy band it would always be an intermediate band.
- What are the main steps in DNA replication?
1) DNA helicase unwinds the DNA by breaking the hydrogen bonds between the bases.
2) Free nucleotides activate using ATP and pair up with the exposed bases of the DNA.
3a) Continuous: DNA polymerase moves up the molecule in the LEADING 5’ to 3’ direction of the new strand, joining the nucleotides by a condensation reaction with the phosphate groups and sugars of adjacent nucleotides (phosphodiester bonds).
3b) Discontinuous: Replication occurs at multiple sites, known as replication forks. The lagging strand is polymerised antiparallel to the direction of the DNA helicase. DNA polymerase works in short sections as the DNA helicase goes up the molecule. The Okazaki fragments are then joined together by DNA ligase.
4) DNA rewinds into a helix
- What does DNA polymerase do?
It bonds the phosphate group and sugar of adjacent nucleotides to form a phosphodiester bond.
- What does the base sequence in DNA code for?
The base sequence determines the order of amino acids.
- How many bases code for each amino acid?
3 (a Codon)
- What is the process called by which the code is copied from DNA to mRNA?
Transcription
- What is the relationship between DNA and mRNA?
DNA and mRNA are complementary to each other’s codons.
- Which enzyme controls transcription?
DNA polymerase
- What is an exon and what is an intron?
Exons are coding sections of the DNA, and introns are non-coding sections
Describe the process of Transcription
1) DNA helicase unzips a section (gene) of the DNA by breaking hydrogen bonds between complementary base pairs.
2) RNA polymerase links to the template strand of the DNA and mRNA nucleotides attach to complementary base pairs.
3) The copying stops at a stop codon and the new pre-mRNA detaches from the DNA.
4) Post-transcriptional modification takes place and mature mRNA leaves the nucleus via nuclear pores into the cytoplasm to be translated into protein.
- What is meant by post-transcriptional modification?
pre-mRNA contains both introns and exons, so the modification removes the introns leaving only coding regions. The exons are spliced together to form mature mRNA.
- Where are proteins synthesised?
Ribosomes
- How does mRNA leave the nucleus?
mRNA leaves the nucleus through nuclear pores
- Write down two structural differences between DNA and RNA.
DNA is a long polynucleotide chain, whereas RNA is a shorter polynucleotide chain
DNA is a double-stranded helix, whereas RNA is a single-stranded helix
- What is amino acid activation?
The process of attaching an amino acid to the tRNA using ATP.
- What determines which amino acid is attached to a molecule of tRNA?
the codon the tRNA is attaching to (complementary to)
- What is an anticodon?
The triplet base code on tRNA
- What is the relationship between the bases on a codon and anticodon?
The bases are complementary and can form base pairs.
- How many codons can a ribosome accommodate at one time?
2 codons
- How are codons and anticodons joined on the ribosome?
Codons and anti codons join by forming hydrogen bonds between complementary base pairs.
- Describe how the DNA base sequence determines the amino acid sequence in the primary structure of a protein.
The DNA base sequence determines the order and number of amino acids. Each exon triplet code in the DNA sequence codes for an amino acid; the number of these codons determines the number of amino acids. They are non-overlapping codes, only read once.
- What type of bond links two amino acids together?
Peptide bonds
- What type of codon terminates the synthesis of a protein?
Stop codons (UGA, UAG, UAA)
Describe the process of translation
1) mRNA is a linear chain of 3 base codons which are complementary to anti codons on the tRNA.
2) mRNA attaches to the small subunit of the ribosome and the large subunit has 2 attachment sites for tRNA.
3) The tRNA hold their speicifc amino acids in position to form peptide bonds and create a polypeptide chain.
4) The ribosomes move along the mRNA strand holding the tRNA in place until the amino acid is bonded. Then the tRNA leaves, the ribosome moves along, and the next tRNA attaches to the next mRNA codon.
mRNA translated from a gene carries the code for the formation of a polypeptide with amino acids in a certain order.
One gene = one polypeptide
- What is meant by post-translational modification?
The modification of the polypeptide chain at the RER. They are coiled or folded into secondary structures, further folded into a tertiary structure and bonded to other chains to form a quaternary structure.
They can be modified further at the Golgi body with prosthetic parts to form glycoproteins, phospho-proteins and lipoproteins.
