1.4 nucleic acids Flashcards
give the name of the monomer from which DNA and RNA are composed.
mononucleotides.
give the three components which make up individual nucleotides.
- a pentose sugar (ribose in RNA, deoxyribose in DNA)
- a phosphate group
- a nitrogen-containing organic base (guanine, cytosine, adenine, thymine or uracil)
mononucleotides join together via condensation reactions to form dinucleotides. describe which component of one nucleotide joins with the component of another nucleotide, including the bond which is formed between the two mononucleotides.
- two mononucleotides may join as a result of a condensation reaction between the pentose sugar of one nucleotide and the phosphate group of another.
- a phosphodiester bond forms between the two mononucleotides, forming a dinucleotide.
the continued linking of dinucleotides via condensation reactions forms a long chain known as a what?
polynucleotide.
DNA forms a double helix structure, composed of two polynucleotide strands. give the type of bond which forms between these strands.
hydrogen bonds.
give the three components which make up adenosine triphosphate (ATP)
- adenine - a nitrogen-containing organic base.
- ribose - a 5-carbon pentose sugar.
- phosphate - a chain of three phosphate groups.
describe how ATP stores energy, and give an example of how this energy is used in cells once released.
- ATP is a nucleotide with three phosphate groups.
- the phosphoanhydride bonds between these phosphate groups are unstable and have a low activation energy, meaning that they can be easily broken.
- when these bonds break, a considerable amount of energy is released, which can then be used to initiate metabolic reactions within cells.
give the equation of the hydrolysis reaction which converts ATP into adenosine diphosphate (ADP) and inorganic phosphate (Pi)
ATP + H₂O → ADP + Pi + E (energy)
give the enzyme which catalyses the reaction of ATP hydrolysis.
ATP hydrolase.
give the enzyme which catalyses the condensation of ADP and Pi to reform ATP.
ATP synthase.
the synthesis of ATP from ADP involves the addition of a Pi molecule to ADP. describe the three ways in which this occurs in living organisms.
- photophosphorylation - occurs in chlorophyll-containing plant cells during photosynthesis.
- oxidative phosphorylation - occurs in eukaryotic cells during aerobic respiration.
- substrate-level phosphorylation - occurs in eukaryotic cells when phosphate molecules are transferred from donor molecules to ADP.
give two reasons why ATP is a better immediate energy source in cells than glucose.
- each ATP molecule releases less energy than each glucose molecule, therefore the energy for reactions powered by ATP is released in smaller, more manageable quantities than those powered by glucose.
- the hydrolysis of ATP to ADP is a single reaction that releases immediate energy, whereas the breakdown of glucose is a longer series of reactions, which therefore delays energy release.
describe three energy-requiring processes which occur in cells that are driven by ATP.
- metabolic processes - ATP provides the energy required to synthesise macromolecules, such as glucose or proteins, from their basic units.
- movement - ATP provides the energy for muscle contraction, by providing the energy for the filaments of muscle to slide past one another.
- active transport - ATP provides the energy required to change the shape of carrier proteins in plasma membranes, therefore allowing ions to move against a concentration gradient.
explain why water is described as a ‘dipolar’ molecule.
- although water molecules have no overall charge, the oxygen atom found within water has a partial negative charge, whilst the hydrogen atoms have partial positive charges.
- this means that water molecules have both positive and negative poles, and are therefore described as ‘dipolar’.
state the type of bonding found within water.
hydrogen bonding.
