nucleotides and nucleic acids Flashcards
chap 3
2 types of ribose? What’s the difference? What are they in?
Deoxyribose (DNA)
Ribose (RNA)
Deoxy- oxygen removed (in this case from C2)
What is a 1,4 glycosidic bond? In what reaction?
The bond between C1’ and C4’ in a disaccharide
Condensation reaction
Lactose
Galactose + glucose
Maltose
Glucose + glucose
Sucrose
Fructose + glucose
2 types of nucleic acids? Difference?
Deoxyribonucleic acid (one less oxygen on C2’)
Ribonucleic acid (one more oxygen on C2’)
3 types of RNA?
tRNA, mRNA, rRNA
Nucleotide structure (3)
PO4 ^2- phosphate group
Pentose sugar monosaccharide (ribose or deoxyribose)
Nitrogenous base (A,T,G,C)
What reaction makes a polynucleotide? Bonds? Between what?
-Condensation
-Phosphate group on C5’ forms a phosphodiester bond with hydroxyl group on C’3
What is a polynucleotide?
One DNA strand
Bonds between bases? What is the rule that bonds these bases?
Hydrogen bonds
Complementary base pairing
Purine structure? Egs?
Double ring
A,G
Pyrimidine structure? Egs?
Single ring
T,C,U
Anti parallel strands means?
2 strands run in opposite directions
Why is complementary base pairing important? (2)
-allows DNA to be copied and transcribed during protein synthesis
-maintains 2nm width of DNA
True or false- RNA is single stranded, unlike DNA
True
Alternating sugar and phosphate groups called?
Sugar phosphate backbone
What is DNA replication? why must it be accurate?
making identical copies of DNA molecules
so daughter cells have exact copy of parental DNA
4 steps of DNA replication
(1st enzyme, pairing from nucleus, 2nd enzyme, result)
- helicase unwinds + unzips hydrogen bonds
- Bases (from nucleus-abundant nucleotides) bind to bases on the strands
- polymerase joins phosphodiester bonds, forming backbone
- 2 identical DNA molecules
Why is DNA replication called semi conservative?
1 strand og
1 strand new
Where does the water molecule come from during the condensation reaction to make polynucleotides?
The OH- in the phosphate group on C5’ and the H from the hydroxyl group on C3’
Genetic code- 4 adjectives + their meanings
- triplet code
- universal: genetic code applies to all organisms
- degenerate: 1 amino acid can be made from lots of combos of diff codons
- nonoverlapping: codons read ‘in frame’ (nucleotides don’t share codons)
Transcription vs translation (process + location)
Transcription- copy gene into mRNA (nucleus)
Translation- decode mRNA into protein (cytoplasm)
What is the ‘reading frame’? What is usually the start codon?
The arrangement of nucleotides into codons
ATG/AUG
What are the 2 strands of DNA in transcription called? What are their functions?
Sense strand- coding strand
Antisense strand- template strand
mRNA has the same codon sequence as which DNA strand?
sense
tRNA has the same codon sequence as which DNA strand?
antisense
What enzyme is used in TRANSCRIPTION to unwind DNA into sense and antisense strands? Which enzyme is this similar to?
RNA polymerase
(similar to DNA helicase)
List 3 similarities between transcription and replication
HINT (bonds, enzyme, nucleotide)
- both form hydrogen bonds
- both use polymerase to form phosphodiester bonds between nucleotides
- both require free nucleotides to pair bases
List 3 differences between transcription and replication
HINT (product, enzyme, nucleotide)
- transcription makes a single mRNA strand whereas replication makes 2 DNA molecules
- transcription uses RNA polymerase whereas replication uses DNA polymerase
- transcription uses A,U,G,C (ribonucleotides) whereas replication uses A,T,G,C (deoxyribonucleotides)
Is mRNA single or double stranded?
Single
What did the semi-conservative experiment prove and how?
- that one DNA strand in replicated molecules was old and one was new
- using heavy and light nitrogen to form the bases (before division: all heavy, 1st division: half heavy, 2nd division: all light, some a little bit heavy)
Explain the process of translation in protein synthesis (6)
- mRNA start codon binds to rRNA in ribosomes (in the rough ER)
- a tRNA with a complementary anticodon and an amino acid binds to mRNA start codon
- repeat with more tRNA so the first amino acid is transferred to the second amino acid via a peptide bond
- catalysed by peptidyl transferase (in ribosome)
- ribosome moves along mRNA, releasing tRNA, until a polypeptide is formed
What does ATP stand for?
Adenosine triphosphate
Adenosine Triphosphate structure vs Adenosine Diphosphate structure
TRI: 3 phosphate groups, ribose sugar, adenine
DI: 2 phosphate groups, ribose sugar, adenine
How much energy does ATP release per hydrolysis? Endo or exo? Why?
30.6 KJmol-1
Exo bc energy change is pos so more energy is taken in breaking bonds
What is the equation for ATP hydrolysis?
ATP + water–> P (inorganic) + ADP
Properties and functions of ATP? (5)
- Small- moves easily
- Releases small amounts of energy- reduces waste
- Unstable- phosphate easily removed, immediate energy source
- Regenerated easily from ADP- constant energy supply
- Water soluble- can dissolve in cytoplasm where chemical reactions occur
5 steps to DNA extraction
HINT: each step involves one thing removing one part of the cell
- Grind sample= cell wall
- Mix detergent= cell surface membrane
- Salt= hydrogen bonds (so DNA does not dissolve in water)
- Protease= histones
- Alcohol= makes DNA a precipitate
Names of strands in DNA replication vs transcription
Replication:
leading and lagging
Transcription:
sense and antisense
