B2- Nucleic Acid, ATP, Water and Inorganic Ions Flashcards
What is the function of DNA?
Function: hold or store genetic information; contains all the instructions for the growth and development of all organisms
What is the structure of RNA?
Function: transfer the genetic code in DNA out of the nucleus → carry it to the ribosomes in the cytoplasm
What is the structure of a nucleotide?
Each nucleotide is formed from:
-A pentose sugar (a sugar with 5 carbon atoms)
-A nitrogen-containing organic base
-A phosphate group
What are the difference between RNA and DNA nucleotides?
DNA contains a deoxyribose
RNA contain ribose
DNA contains thymine
RNA contains uracil
What is the structure of DNA?
Both antiparallel strands are held together by hydrogen bonding between complementary DNA base pairs
The purine adenine (A) always pairs with the pyrimidine thymine (T) – two hydrogen bonds
The purine guanine (G) always pairs with the pyrimidine cytosine (C) – three hydrogen bonds
What is the structure of RNA?
Made up of one polynucleotide strand
Much shorter compared to DNA
Examples include:
Messenger RNA (mRNA) - the transcript copy of a gene that encodes a specific polypeptide
Transfer RNA (tRNA)
Ribosomal RNA (rRNA)
What is semi-conservative replication?
1)DNA Helicase catalyses the unwinding of the double helix, by breaking the hydrogen bonds between complementary base pairs → strands separate
2)Free nucleotides are attracted to the exposed bases on each strand by base pairing
3)Nucleotides are then joined together by DNA Polymerase - catalyses the formation of phosphodiester bonds between adjacent nucleotides
4)Original & new strands are joined together through hydrogen bonding between base pairs
How does DNA Polymerase work during semi-conservative replication?
DNA polymerase cleaves (breaks off) the two extra phosphates and uses the energy released to create the phosphodiester bonds (between adjacent nucleotides)
BUT… Polymerase can only build the new strand in one direction (5’ to 3’ direction)
What are leading and lagging strands in semi-conservative replication?
The template strand that the DNA polymerase attaches to is known as the leading strand
The strand where DNA polymerase can synthesise the new strand continuously
The other template strand created is known as the lagging strand
DNA polymerase moves in the opposite direction
This strand is synthesised in short fragments (Okazaki fragments)
How does DNA ligase work during semi conservative replication?
Then joins these lagging strand segments together (phosphodiester bond formation) → forms a continuous strand
Validating the Watson-Crick model of DNA replication
1) Bacteria with DNA containing heavier nitrogen
2)DNA settles at bottom of centrifuge tube
3)Bacteria with DNA containing only heavier nitrogen allowed to replicate in broth inside light nitrogen.
4)DNA settles in the middle as a mixture of both
What is ATP?
Adenosine triphosphate (ATP) is a phosphorylated nucleotide (just like the monomers of DNA/RNA)
In all known forms of life, ATP from respiration is used to transfer energy in all energy-requiring processes in cells - it is the universal energy currency of life
What is the structure of ATP?
Adenosine (a nucleoside) can be combined with one, two or three phosphate groups
One phosphate group = adenosine monophosphate (AMP)
Two phosphate groups = adenosine diphosphate (ADP)
Three phosphate groups = adenosine triphosphate (ATP)
How does ATP hydrolysis work?
Hydrolysis of ATP to adenosine diphosphate (ADP) and an inorganic phosphate group (Pi) is catalysed by the enzyme ATP hydrolase sometimes called ‘ATPase’
How does ATP synthesis work?
ATP is formed when ADP is combined with an inorganic phosphate (Pi) group by the enzyme ATP synthase
What are the benefits of ATP?
Can be recycled
Hydrolysis is quick and easy
Soluble and moves easily in cells
Forms phosphorylated intermediates
What is the structure of water?
The sharing of the electrons is uneven between the oxygen and hydrogen atoms → forms a dipole or polar molecule
This is what allows hydrogen bonds to form between water molecules
How and why does water act as a solvent?
Many ions (e.g., sodium chloride / NaCl) and covalently bonded polar substances (e.g., glucose) will dissolve in water
Allows chemical reactions to occur (as molecules become more reactive)
Allows efficient transport of metabolites
How does and why does water have a high specific heat capacity?
Why? Hydrogen bonds! - a lot of energy is required to break these bonds → temperature of water doesn’t change greatly
Advantage?
Provides a suitable habitat for organisms
Maintains optimal temperatures for enzyme activity and heat transfer in the blood plasma
How and why does water act as a high latent heat of vaporisation?
Large amounts of energy is required to break the many hydrogen bonds in water & change its state
Advantage?
Cooling effect - Organisms can lose a great amount of heat, without loosing too much water
E.g., transpiration from leaves, evaporation of water in sweat on the kin
How does water help with cohesion and adhesion?
Hydrogen bonds between water molecules allows for strong cohesion between water molecules
Advantage? - Allows column of water to move through the xylem of plants & through blood vessels in animals
Water is also able to hydrogen bond to other molecules, such as cellulose, which is known as adhesion
Advantage? - This also enables water to move up the xylem due to transpiration
How are H+ ions useful?
Also called protons
Concentration of H+ in a solution determines the pH (inversely proportional)
The more H+ ions present, the lower the pH (the more acidic the solution)
The fewer H+ ions present, the higher the pH (the more alkaline the solution)
How are Fe2+ ions useful?
Essential for transporting oxygen around the body
Fe2+ in Haemoglobin binds to oxygen → forms oxyhaemoglobin
Myoglobin (in muscles) is a similar protein, but is only made up of one polypeptide chain
Iron is also necessary for electron transport in respiration/photosynthesis
Iron ions are an essential component of cytochromes (that are themselves a component of electron transport chains)
How are sodium ions useful?
Required for the transport of glucose and amino acids across cell-surface membranes (e.g., in the small intestine)
Glucose and amino acid molecules can only enter cells (through carrier proteins) alongside Na+ - this is known as co-transport
Na+ is also required for the transmission of nerve impulses
