Unit 1.5 - Nucleic acids Flashcards
Nucleotide
Monomer of nuclei acid compromising a pentose sugar, nitrogenous base and a phosphate group.
Pyrimidine bases
Class of nitrogenous bases including thymine, cytosine and uracil.
Purine bases
Class of nitrogenous bases including adenine and guanine.
What does a nucleotide consist of?
Phosphate group, ribose in RNA/ deoxyribose in DNA, nitrogenous base.
Chemoautotrophic
Organism that uses chemical energy to make complex organic molecules.
Photoautotrophic
Organism that uses light energy to make complex organic molecules, its food.
Adenosine triphosphate (ATP)
Nucleotide in all living cells; hydrolysis makes energy available and its formed when chemical reactions release energy.
State an example of chemoautotrophic organisms.
Some bacteria and Archaea use energy derived from oxidation of electron donors e.g. H2, Fe 2+.
State an example of photoautotrophic organisms.
Green plants use light energy in photosynthesis.
State an example of heterotrophic organisms.
Animals derive their chemical energy from food.
1) When is ATP synthesised?
2) When is it broken down?
1) Energy is made available such as in mitochondria.
2) By ADP when energy is needed such as muscle contraction.
What is ATP called? Explain why.
Universal energy currency because it’s involved in all cells in all living organisms.
1) What does adenosine contain?
2) What does ATP contain?
1) Adenine + Ribose
2) Adenine + Ribose + 3 phosphate groups
1) What happens when ATP is needed?
2) How does ADP form?
1) Enzyme ATPase hydrolyses bond between 2nd and 3rd phosphate group, removing 3rd group.
2) ATP molecule hydrolyses into adenosine diphosphate and an inorganic phosphate ion.
1) Define exergonic reaction.
2) How much energy is released in breakdown of ATP?
3) What is the word equation for the breakdown of ATP?
1) Releases energy (ATP hydrolysis).
2) Endergonic 30.6kJ, Exergonic -30.6kJ.
3) ATP + Water > hydrolysis (muscles) > ADP + P
Opposite for condensation (mitochondria).
1) Define endergonic reaction.
2) How do organisms release energy?
3) Define phosphorylation.
1) Requires energy input.
2) Respiration producing ATP.
3) Addition of a phosphate group (e.g. to ADP).
State an advantage of the following over glucose:
1) Hydrolysis of ATP to ADP
2) Enzymes
1) Hydrolysis of ATP to ADP single reaction, releases energy immediately however breakdown of glucose involves intermediates and takes longer for energy release.
2) Only one enzyme needed to release energy from ATP but many are needed from glucose.
State 2 advantages of ATP over glucose.
1) ATP releases energy small amounts, where and when needed (less waste) but glucose has large amounts and releases all at once.
2) ATP common source of energy for different chemical reactions, increasing efficiency and control by cell.
1) What happens when a phosphate group is transferred from ATP to another molecule?
2) What effect does this have on the activation energy?
1) Recipient molecule more reactive.
2) Lowering activation energy of a reaction.
State 5 roles of ATP.
Metabolic processes, active transport, movement, nerve transmission and secretion.
State the role of ATP in:
1) Metabolic processes
2) Active transport
1) Build large complex molecules from small simple molecules e.g. DNA synthesis from nucleotides, proteins from amino acids.
2) Change shape of carrier proteins in membranes allow molecules or ions to be moved against a concentration gradient.
State the role of ATP in:
1) Movement
2) Nerve transmission
3) Secretion
1) Muscle contraction, cytokinesis.
2) Sodium-potassium pumps actively transport sodium and potassium ions across the axon membrane.
3) Packaging and transport of secretory products into vesicles in cells.
1) What is DNA composed of?
2) What forms the ‘backbone’?
1) 2 complementary polynucleotide strands in a double helix held together by hydrogen bonds. (4 organic bases).
2) Deoxyribose sugar and phosphate groups are on outside of DNA molecule.
1) Why do the base strands face inwards?
2) State number of hydrogen bonds in adenine and thymine.
3) State number of hydrogen bonds in cytosine and guanine.
1) Due to the rings.
2) Joined by 2 H bonds.
3) Joined by 3 H bonds.
1) How big is the double helix?
2) How are the nucleotides arranged in the strands?
1) 2nm in diameter
2) Antiparallel; running parallel but facing in opposite directions.
1) State the function of the sugar phosphate.
2) Why are 2 strands of DNA able to separate?
1) Base pairs on inside of double helix, within deoxyribose phosphate backbones, genetic information is protected.
2) Held together by hydrogen bonds.
State 2 advantages of DNA.
1) Very stable, information content passes essentially unchanged from generation to generation.
2) Large molecule so carries large amount of genetic information.
Genetic code
DNA & mRNA base sequences determine the amino acid sequences in an organism’s proteins.