nucleic acids Flashcards
what structures are made from DNA?
chromosomes
what type of protein is contained in chromosomes?
histones
describe the structure of DNA?
- made from 2 polynucleotide molecules
- arranged in a double helix
what are the monomers of DNA and RNA?
nucleotides
what molecules are DNA and RNA made from?
- phosphate group
- (deoxy)ribose sugar
- nitrogenous bases
what reaction joins the components of a nucleotide together?
condensation
what are the four nitrogenous bases is DNA?
- adenine
- cytosine
- guanine
- thymine
what are the four nitrogenous bases in RNA?
- adenine
- uracil
- guanine
- cytosine
which nitrogenous bases are base pairs?
- adenine and thymine
- adenine and uracil
- guanine and cytosine
what is the bond between two nucleotides called?
phosphodiester bond
how is the double helix constructed in DNA?
- phosphate group in one nucleotide bonds with the pentose sugar from another via condensation reaction to form the backbone
- complimentary bases form the middle (ladder) via hydrogen bonds
how many hydrogen bonds form between base pairs?
- adenine + thymine/uracil : 2
- guanine + cytosine : 3
DNA is an antiparallel molecule. what does this mean?
the 2 polynucleotide strands are arranged in different directions
how does the structure of DNA make it a stable molecule?
- held together by phosphodiester bonds which are extremely strong, covalent bonds which arent easily broken
- thousands of hydrogen bonds between bases
how does the size of DNA help its function?
- DNA is a huge molecule
- this means it can carry the immense amount of genetic material it needs to
how does the structure of DNA ensure that the genetic material inside is protected?
- coiled into a double helix
- sugar-phosphate backbone
- means genetic information inside is protected from chemical and physical forces
what are the two main stages of cell division?
- nuclear divisions (mitosis or meiosis)
- cell division
describe the method of DNA replication
- DNA double helix is unwound partially by DNA helicase
- DNA exposed nucleotides are attached to new “free” complimentary nucleotides, using energy from the hydrolysis of ATP
- DNA polymerase attaches the new copy strand of DNA together with deoxyribose-phosphate bonds
what conditions must be met for DNA replication to take place?
- pool of “free” nucleotides containing all four types must be present
- both strands of DNA act as a template
- DNA helicase and polymerase must be present
- ATP must be present
what is semi-conservative DNA replicaion?
where there is one original strand of DNA that is being used as a template to create a new polynucleotide strand
describe the process of DNA replication in detail
- DNA helicase unwinds the double helix by breaking the hydrogen bonds between base pairs, exposing the nitrogenous bases
- hydrolysis of ATP activates free nucleotides
- activated nucleotides then attach themselves to their complimentary bases on the original DNA molecule
- new DNA molecule is built up
- DNA polymerase catalyses the condensation reactions between adjacent nucleotides, forming backbone
- “proof-reading” enzyme checks the new strand for mutations, then “winding” enzymes winds up the new copied polynucleotide chains to form a double helix
- genetically identical chains
summarise Meselson and Stahl’s experiment that provides proof for semi-conservative DNA replication
- grow bacteria in nitrogen 15 (heavier isotope); when centrifuged leaves “heavy DNA”
- transfer the cells into nitrogen 14 (lighter isotope) to grow for one gen; when centrifuged leaves a hybrid of heavy and light DNA
- leave to grow for a second gen, which when centrifuged leaves light and hybrid DNA
how does Meselson and Stahl’s experiment prove that DNA replication is semi-conservative?
- the new DNA has one strand of the old DNA and one strand of the new
- as more gens are produced, the DNA created is never purely one type (light or heavy) and there is always a mixture
what is ATP made up of?
- 3 phosphates
- adenine
- ribose
how is an ATP molecule similar to a DNA nucleotide?
- both contain phosphate
- both have a base/bases
- both contain pentose sugar
how is an ATP molecule different to a DNA nucleotide?
- the base in ATP is always adenine, whereas there are 4 different nitrogenous bases that a DNA nucleotide could have
- ATP has 3 phosphates, DNA nucleotide has 1
- sugar in ATP is ribose, not deoxyribose
what is the name of the enzyme which;
a) catalyses the reaction that converts ATP to ADP + Pi?
b) catalyses the reaction that converts ADP and Pi to ATP?
a) ATP hydrolase
b) ATP synthase
what are the two organelles where ATP is synthesised?
- Chloroplasts
- mitochondria
what are the 5 main biological functions that ATP provides energy for?
- activation of molecules
- metabolic processes
- active transport
- movement
- secretions
what role does ATP have in the activation of molecules?
inorganic phosphate released in the hydrolysis of ATP can phosphorylate other compounds to make them more reactive and lower their activation energy
what role does ATP have in metabolic processes?
provides the energy that helps to build macronutrients such as starch and polypeptides
what role does ATP have in the active transport of molecules?
ATP changes the shape of the carrier proteins in the plasma membranes, which allows the movement of molecules against their concentration gradient
what are two reasons that ATP is a better source of immediate energy than glucose is?
- ATP doesnt have many steps needed to do in order for the energy to be released, whereas glucose does
- ATP releases small amounts of energy when it is needed, so energy is not wasted, glucose does not
what is an organic ion?
an atom or group of atoms that have gained a net charge by gaining or losing electrons
give two examples of an inorganic ion
- sodium ions
- potassium ions
- chloride ions
- nitrate ions
