1.2 Nucleic acids Flashcards
what does DNA stand for?
deoxyribonucleic acid
what does RNA stand for?
ribonucleic acid
what monomers make up DNA and RNA?
nucleotides
what three components make up a nucleotide?
phosphate group, pentose sugar and nitrogenous organic base
what nitrogenous organic bases are components of DNA nucleotides?
adenine, thymine, guanine, cytosine
what nitrogenous organic bases are components of RNA nucleotides?
adenine, uracil, guanine, cytosine
name the pentose sugar found in DNA nucleotides
deoxyribose sugar
name the pentose sugar found in RNA nucleotides
ribose sugar
what bond is formed when two nucleotides join together?
phosphodiester bond
describe how two nucleotides join together in a DNA molecule [3]
- phosphodiester bond
- between deoxyribose sugar and phosphate group
- condensation reaction
- catalysed by DNA polymerase
describe the structure of DNA [5]
- polymer of nucleotide monomers
- nucleotides made of a phosphate group, deoxyribose sugar and nitrogenous organic base
- phosphodiester bonds between nucleotides form sugar-phosphate backbone
- antiparallel strands coil into double helix shape held by hydrogen bonds
- hydrogen bonds between complimentary base pairs: adenine and thymine, guanine and cytosine
describe the structure of RNA [5]
- polymer of nucleotide monomers
- nucleotides made of a phosphate group, ribose sugar and nitrogenous organic base
- phosphodiester bonds between nucleotides form sugar-phosphate backbone
- short, single-stranded chain
- exposed nitrogenous organic base pairs: adenine and uracil, guanine and cytosine
state four differences between the structures of DNA and RNA
- in DNA, adenine pairs with thymine, but in RNA it pairs with uracil
- DNA has two strands coiled into a double helix, whereas RNA is single-stranded
- RNA is much shorter than DNA
- pentose sugar is deoxyribose in DNA, but ribose in RNA
how many hydrogen bonds form between adenine and thymine?
two
how many hydrogen bonds form between guanine and cytosine?
three
how many hydrogen bonds form between adenine and uracil?
two
when was DNA first observed?
1800s
when was the double helix structure of DNA discovered?
1953
who discovered the double helix structure of DNA?
Watson and Crick
do strands of DNA run in the same direction?
no, they are antiparallel
in what direction do the two strand run in a DNA molecule?
they are antiparallel
one runs in 5’ to 3’ direction
other runs in 3’ to 5’ direction
describe and explain how DNA is a stable molecule [3-4]
- sugar-phosphate backbone protects chemically reactive organic base inside double helix
- hydrogen bonds between complimentary base pairs form bridges between DNA strands
how does the proportion of G-C pairings affect the stability of a DNA molecule?
G-C pairings have three hydrogen bonds between them, whilst A-T pairs have two, meaning the higher the proportion of G-C pairings, the more stable the DNA molecule will be.
what is the function of DNA?
to store genetic information and pass it between cells and down generations
what is the main function of RNA?
to transfer genetic information from DNA to ribosomes
what are ribosomes made of?
RNA and proteins
how is the structure of DNA suited to its functions? [4-6]
- two strands joined by hydrogen bonds allows them to separate during DNA replication and protein synthesis
- sugar-phosphate backbone and helical shape protect base pairs and genetic information from outside chemical and physical forces
- complimentary base pairing allow DNA to replicate and transfer information as mRNA
why does DNA replicate before cell division?
so that each new cell has the full amount of DNA
by what process does DNA replicate?
semi-conservative replication
name for requirements for DNA replication to take place
- presence of free nucleotides with either adenine, thymine, guanine or cytosine as their organic base
- both DNA strands act as templates for free nucleotides to attach to
- presence of DNA polymerase enzyme
- a source of chemical energy
describe the process of semi-conservative replication [5-6]
- enzyme DNA helicase breaks hydrogen bonds between complimentary base pairs
- double helix separates and unwinds to form two single strands
- each exposed strand acts as a template for a new strand
- free nucleotides bind to complimentary base pairs on template strands with hydrogen bonds
- DNA polymerase joins new nucleotides together to form the new sugar-phosphae backbone
- two new strands are identical and contain half of the original DNA material
what does ATP stand for?
adenosine triphosphate
why is energy important?
plant and animal cells need energy for biological processes to occur
what components make up ATP?
adenine, ribose, three phosphate groups
where is energy stored in ATP?
phosphate bonds between the phosphate groups
how is energy released from ATP?
ATP is broken down into ADP
bonds between phosphate groups break
hydrolysis reaction
catalysed by ATP hydrolase
hydrolysis of phosphate bonds releases energy
what molecule is released when ATP breaks down to ADP?
inorganic phosphate
how can ADP be converted back to ATP
add an inorganic phosphate molecule
condensation reaction
catalysed by ATP synthase
what type of reaction converts ATP to ADP
reversible reaction
how can the inorganic phosphate lost from the conversion of ATP to ADP be used?
phosphorylation
it can be added to another compound to make it more reactive
give two reasons why ATP is a better immediate energy source than glucose
- ATP releases smaller amounts of energy than glucose, meaning its much more manageable
- hydrolysis of ATP to ADP is a single reaction, so releases energy immediately, whilst breakdown of glucose is multiple reactions so takes longer
name the two products of ATP hydrolysis
ADP and an inorganic phosphate
give two ways in which the hydrolysis of ATP is used in cells
- to provide energy for other reactions
- to add phosphate to other substances and make them more reactive
name the process of adding phosphate to a substance to increase its reactivity
phosphorylation
describe the atomic structure of water
two hydrogen atoms covalently bonded to one oxygen atom
describe/explain the polarity of water
- dipolar molecule
- no overall charge
- oxygen atom slightly negatively charged
- hydrogen atoms slightly positively charged
how are multiple water molecules bonded together?
- water is dipolar
- opposite poles attract
- positive oxygen on one molecule attracts negative hydrogens of another and vice versa
- attractive forces are hydrogen bonds
explain five properties that make water important for organisms [5]
- metabolite in condensation and hydrolysis reactions
- good solvent to transport substances
- high specific heat capacity to buffer temperature change
- high latent heat of vaporisation to provide cooling effect through evaporation
- cohesion between water molecules to support continuous column of water in plants
what is a metabolite?
substance involved in a metabolic reaction
