Unit 1.5 Nucleic acid Flashcards
Tell me all about DNA
DNA = deoxyribonucleic acid
Which contains genetic information
Functions:
- Replication in dividing cells = the two strands of the double helix separate and these act as templates for the synthesis of two new complementary strands
- DNA contains a code for protein synthesis = the base sequence represents information carried by DNA and determines the sequence of amino acids (primary structure) in proteins
Polymer:
- Polynucleotide
Monomer and it’s structure:
- A = phosphate = circle
- B = sugar (5 carbon pentose) = pentagon
- C = organic (nitrogenous) base = rectangle
consists of 4 nitrogenous bases (adenine, thymine, guanine, cytosine)
- All connected by just a line
Nucleotide monomers join together in a condensation reaction between phosphate group of one and pentose sugar group of another, creating sugar-phosphate backbone. Bonds are covalent, called phosphodiester bonds. Builds up into very long chains of nucleotides.
4 nitrogenous bases classed as purines or pyrimidines:
- Purines = adenine & guanine
- Pyrimidines = thymine & cytosine [& uracil]
- 4 nucleotides possible for DNA
DNA structure:
- Think of it as an actual DNA diagram, just chemistry style tho
- One side the pentose and phosphate are stacked with strong covalent bonds
- Then the other side is actually turned 180°
- For when both sides connect:
Weak hydrogen bonds between A & T
Weak hydrogen bonds between C & G
- In addition, they twist to form a double helix
How is DNA suited to its functions?
- Very stable molecule and its information content passes unchanged from generation to generation
- Very large molecule and carries large amount of genetic information
- 2 strands able to separate as they are held together by hydrogen bonds that can be broken by enzymes
- Base pairs are between the double helix so the genetic information is protected within the 2 backbones
Tell me all about RNA
RNA = ribonucleic acid
Similar to DNA. 3 main types of RNA and they all use information from DNA for the construction of proteins but in slightly different ways
- Messenger RNA (mRNA)
- Transfer RNA (tRNA)
- Ribosomal RNA (rRNA)
Polymer:
- Polynucleotide
Monomer and it’s structure:
- A = phosphate = circle
- B = sugar (5 carbon pentose) = pentagon
- C = organic (nitrogenous) base = rectangle
consists of 4 nitrogenous bases (adenine, uracil, guanine, cytosine)
- All connected by just a line
Nucleotide monomers join together in a condensation reaction between phosphate group of one and pentose sugar group of another, creating sugar-phosphate backbone. Bonds are covalent, called phosphodiester bonds. Builds up into shorter, single chain of nucleotides
4 nitrogenous bases classed as purines or pyrimidines:
- Purines = adenine & guanine
- Pyrimidines = uracil & cytosine
- 4 nucleotides possible for RNA
RNA structure:
- Think of it as just half of a DNA structure with the previous diagram :v
- The pentose and phosphate are stacked with strong covalent bonds
- The bases just contain adenine, uracil, cytosine, guanine
Compare DNA and RNA
Shape:
DNA = double helix
RNA = single stranded
Length:
DNA = long
RNA = short
Sugar:
DNA = deoxyribose
RNA = ribose
Nitrogenous bases:
DNA = adenine, thymine, guanine, cytosine
RNA = adenine, uracil, guanine, cytosine
Types:
DNA = one type
RNA = 3 types, messenger RNA (mRNA), transfer RNA (tRNA), ribosomal RNA (rRNA)
Tell me all about DNA replication
- DNA copies itself before cell division
- Takes place during interphase of cell cycle
(creates genetically identical sister chromatids
Steps and visuals of DNA replication:
1. The DNA molecule unwinds.
- So it’s just the DNA untwisting, u can see the base pairs too
- The DNA unzips and the polynucleotide strands separate.
(Due to helicase enzyme)
Breaking the hydrogen bonds between the bonds.
(The bases are exposed)
- So basically the DNA is being separated from their pair
- From the helicase enzyme (looks like a helicopter) from below - Free nucleotides are activated and are attracted to the exposed bases.
Free nucleotides align with complementary bases
A-T, C-G
- So they bases are exposed right?
- Now they are kinda just rebuilding themselves to other complementary bases
(btw, we actually have no idea where these complementary bases come from, they just spawn ig)
- In addition, phosphate molecules activate the free nucleotides - DNA polymerase join the nucleotides together.
To form new strands.
Forging covalent phosphodiester bonds
- Basically the end game of the previous step
- Ig state about the polymerase enzyme helping in the joining - 2 new identical DNA molecules are formed
- DNA winds up into a double helix
- In addition, the DNA polymerase works in a 5’-3’ direction down the new strand, continuous process
- However, DNA = anti-parallel, therefore the enzyme only works in small sections on the other molecule, leaving gaps
- Another enzyme , DNA ligase, joins up the small sections to complete the process
Visuals: a ladder at the bottom connected to 2 incomplete ladders to the top. DNA polymerase connecting n shi but some gaps left soo ligase there to join em up.
Tell me all about ATP
ATP = Adenosine triphosphate
- The main energy currency of all cells
- A nucleotide
- Small water-soluble molecule
Structure:
- A = adenine = Hexagon connected to pentagon
- B = ribose = pentagon
- C = phosphate = 3 circles connected but not touching (lines)
- All connected by lines, just like DNA/RNA
How ATP stores/releases energy:
- 3 phosphate groups = negatively charged ∴ repel each other
- Makes covalent bond linking them unstable (like a coiled spring)
- Each phosphate straining to break away from each other
- Bonds easily broken and release 30.6kJmol^-1 of energy
Visuals for that:
- When ATP goes through hydrolysis, releases the energy (30.6kJmol^-1)
- and turns into ADP + Pi (1 phosphate removed ig
- However the ADP can go through phosphorylation (the addition of phosphate to ADP) and turns into ATP again
- ^ and that’s cuz of organic substrate (glucose) during respiration in mitochondria (endergonic reaction), ig it has its 30.6kJmol^-1 back
- This can be a reversible reaction
Advantages of ATP as a supplier of energy:
1. Hydrolysis of ATP to ADP = single reaction
Compare that to glucose, as that one involves many reactions & takes longer
2. Only 1 molecule needed to transfer energy to chemical reactions
3. Different types of energy can be transferred into a common form
4. Only 1 enzyme, ATPase, needed to release energy from ATP; many are needed for energy release from glucose
5. ATP releases energy in small manageable amounts that will not damage the cell and will not be wasted. Glucose contains large amounts of energy, which would be released all at once
6. ATP easily transported
Role of ATP:
1. Active transport = movement of substances against their conc. gradient
2. Muscle contraction (for movement)
3. Secretion = packaging and transport of secretory products into vesicles in cells; exported by exocytosis
4. Endocytosis = bulk movement of large molecules into cells
5. Anabolic reactions e.g. synthesis of large molecules (proteins) from smaller ones (amino acids), protein synthesis or cellulose from β-glucose
6. DNA replication
7. Nerve transmission
8. Cell division
Suggest why ATP is called the universal energy currency
Used by all organisms/species to provide energy for most biochemical reactions
Tell me all about protein synthesis
Consists of 2 stages:
Transcription - occurs in nucleus and involves DNA and mRNA
DNA strand is transcribed into mRNA
Translation - involves mRNA, tRNA and ribosomes
The process of amino acids being assembled together forming a polypeptide chain/protein
Transcription:
A molecule of mRNA is made in nucleus:
1. Hydrogen bonds between complementary bases break and DNA uncoils, separating the 2 strands
- Just like that one time in DNA replication
2. One of the DNA strands is used as a template to make the mRNA molecule
- The template is called the antisense strand
3. Free nucleotides line up by complementary base pairing and adjacent nucleotides are joined by phosphodiester bonds thus forming a molecule of mRNA
- Ig it rlly just be like DNA replication
4. the mRNA moves out of the nucleus through a pore and attaches to a ribosome in the cytoplasm which the next stage occurs (translation)
Translation:
Amino acids join together to form a polypeptide chain:
1. mRNA attaches to a ribosome and tRNA collects amino acids from the cytoplasm and carries them to the ribosome. tRNA is a single stranded molecule with a binding site at one end ∴ can only carry one type of amino acid, and a triplet of bases at the other
- We don’t know how it collects amino acids, but it just does type shi
2. tRNA attaches itself to mRNA by complementary base pairing; two molecules attach to mRNA at a time
3. The amino acids attached to 2 tRNA molecules are joined by a peptide bond, then tRNA molecules detach themselves from amino acids, leaving them behind
- Seems like first person amino acid connecting thingy
4. Process is repeated leading to a formation of a polypeptide chain until a stop codon is reached on mRNA, which ends the process of protein synthesis
Tell me all about genetic code and one additional thing ,’:|
(fully copied by rhys D:)
- DNA codes for the structure of proteins/polypeptides
- DNA contains genes and a gene is a sequence of DNA nucleotides that codes for a protein
- Proteins made from the monomers called amino acids
- Order of the bases in a gene determines the order of amino acids and so determines which proteins are made
- Protein synthesis requires ATP (err what)
The triplet code
- Each triplet code codes for one amino acid
Visualise this:
T T T, G G A, C G C, C C C
Lysine, proline, alanine, glycine
- Each one is one polynucleotide strand from DNA molecule
- Some of the extra codes aren’t used to code for amino acids
- But are used as ‘punctuation marks’
E.g. VAG is a ‘full stop’ codon and AUG is a start codon
Gene mutations
- Mutations are changes in the base sequence of an organisms DNA
- If the base sequence in a gene changes, the sequence of amino acids in a protein [what] the gene codes for also changes
- This may affect how the proteins fold up and so its overall tertiary structure
- Therefore a non-functional protein could be produced
Genes and Polypeptides:
- A gene is a section of DNA on a chromosome which codes for a specific polypeptide
- Polypeptides made in the ribosomes move through the cytoplasm to the golgi
- There the primary structure of the polypeptide is folded into the secondary tertiary and quaternary structure of proteins
- It may also be chemically modified here
This is called post-translational modification
- Polypeptides can be chemically modified by combining non-proteins to them such as:
1. Adding haem group to make haemoglobin
2. Adding carbohydrates to make glycoproteins
3. Adding lipids to make lipoproteins
Tell me about exons and introns
(fully copied by rhys too D:)
- In eukaryotes, the initial RNA version of the code is much longer than the final RNA
- This means some base sequences have been removed
- The initial RNA is called **pre-messenger RNA2 and the sequences that are removed are called introns
- The introns are cut out of the pre-messenger RNA by ribonuclease enzymes
- The sequences that are left, called exons, are joined back together by ligase enzymes
- (Introns don’t carry information to build a protein)
- Introns are a segment of DNA
Visualise this: - U have the gene (double helix thingamabob)
arrow going down - a pre-messenger RNA which is some rectangle
- Not coloured blocks = exon
- Coloured blocks = intron
arrow going down (zoom into exon part???) - Just a rectangle labelled “mRNA” [what???]
Tell me all about semi-conservative replication evidence
I’ll keep it brief, ik I could’ve just did more in-depth research for this but, am sorry, huge ass gamble, take it or leave it.
- Matthew Meselsohn and Franklin Stahl
- Frankie believes DNA replicates semi-conservatively:
1. Both parents strands split
2. Each are copied
3. Then an original and new strand of DNA pair up each time - Matthew believes DNA replicates conservatively:
1. Both parent strands split and copy
2. The 2 parent strands pair up
3. The 2 new strands pair up to make a DNA copy - And then there was some experiment where they spun 15N and 14N and it was definitely something to do with their positions, the heaviness based on the amount of spins, and there was def more than what am saying. GG
