Biological Molecules - Section 2 Flashcards
What is the role of DNA in living organisms
Copies genetic information
What is the role of RNA in living organisms
Transfer genetic code
What are ribosomes formed from?
Formed by mRNA from DNA into ribosomes.
What are the organic bases of DNA?
Cytosine, thymine, adenine, guanine
What are the organic bases in RNA ?
Adenine, cytosine, guanine, uracil
What is the difference in organic bases between DNA and RNA?
DNA has a thymine base whereas RNA has uracil.
What reaction joins two nucleotides and what bond is formed>
Phosphodiester bonds in condensation reactions
How many bases make up a codon?
Three
Why could a change in the sequence of bases result in a non functional enzyme?
If there is a mutation in a gene for an enzyme, its secondary and tertiary structure (so its active site) could change. It therefore wouldn’t be able to bind to the enzyme.
What reaction joins the organic bases in dna ?
Condensation.
Desirable the overall structure of DNA?
DNA has a phosphate group, a nitrogen containing base and deoxyribose. It is a long polymer and is double stranded.
Compare the structure of RNA to DNA?
RNA is a short polymer, single stranded
DNA is a long and double stranded
Describe the stages of semi- conservative replication of dna ?
A section of DNA needs to be replicated
DNA helicase unwinds the two strands of dna by breaking bonds between the bases
Free nucleotides are activated and bind to their complimentary bases
The nucleotides are joined by DNA polymerase which forms phosphodiester bonds
All of the nucleotides are joined to form a complete polynucleotide chain, two identical strands of DNA are formed.
What is the role of DNA helicase in semi-conservative replication?
Unwinds the dna by breaking the hydrogen bonds
What is the role of DNA polymerase in semi-conservative replication?
DNA polymerase joins nucleotides by forming phosphodiester bonds
Why is it called semi-conservative replication ?
Contains one new strand and one old strand
In which direction are nucleotides added to a dna strand, and why can it only happen in this direction?
Can only be added in the 5’ to 3’ direction because the nucleotides shapes and alignments are different and DNA polymerases’ active site has a specific shape with the nucleotide only being complimentary at the 3’ end.
Describe the experiment used the method of dNA replication was semi-conservative.
They began by growing E. coli in medium, or nutrient broth, containing a “heavy” isotope of nitrogen, 15N
Then, the bacteria were switched to medium containing a “light”
14N. isotope and allowed to grow for several generations.
method separates molecules such as DNA into bands by spinning them at high speeds in the presence of another molecule, such as cesium chloride, that forms a density gradient from the top to the bottom of the spinning tube.
Found that after the first replication the DNA bond was intermediate so contained heavy and light nitrogen
Then after the second replication either a mixture of two new strands or one of each.
How is energy released from ATP?
The energy in atp is stored in High energy bonds between the phosphate groups. ATP can be hydrolysed to break one of these phosphate groups
What is hydrolysis?
Chemical reaction by the addition of water.
Which enzyme catalysed the hydrolysis of ATP?
ATP hydrolyse
What is formed when ATP is hydrolysed ?
ADP + Pi
What is the phosphate released during the hydrolysis of ATP used for?
Inorganic phosphate can be used to phosphorylation to other compounds
Why is ATP a more useful energy source than glucose?
ATP is broken down in a single reaction so energy is released rapidly.
How is ATP reformed?
In a condensation reaction :
Photophosphorylation
Oxidative phosphorylation
Substrate level phosphorylation
What enzyme catalyses the reaction when ATP is reformed ?
ATP synthase
Describe the structure of water
Contains slight positive and slightly negative electrons
Polar molecule
Why is water considered a polar molecule ?
It has a positive end and negative end
Describe how waters structure and properties links to its metabolite in many metabolic reactions
Useful in breaking down complex molecules by hydrolysis, condensation reactions, chemical reactions, photosynthesis.
Water: important solvent in which metabolic reactions occur
Water is polar and readily dissolves in gases, wastes, inorganic ions and enzymes.
Water: relatively high heat capacity
=the amount of thermal energy required to rise the temperature of 1kg of substance by 1%
Due to the hydrogen bonds, water specific heat capacity is high. This means water acts as a buffer to sudden temerpature variation because water can absorb a lot of thermal energy.
Water: large latent heat vaporisation
Takes a lot of energy to break hydrogen bonds between molecules.
Maintains body temperature on living organisms e.g sweating.
Body heat is used to evaporate water there fore large amounts of thermal energy are lost, leading to a fall in body temperature.
Water: strong cohesion between water molecules
=tendency of water molecules to stick together
Hydrogen bonds give water a large cohesive forces
Allow water to be pulled up through a tube e.g xylem, transpiration
How do the properties of water allow living organisms to maintain their optimum temperature?
It’s large latent heat evaporation it’s high specific heat capacity maintains its optimum temperature. The hydrogen bonds are difficult to break.
Where are the inorganic ions found in living organisms?
Found in the cytoplasm and body fluids
Give four examples of ions, and their specific roles linking to their properties
Hydrogen ions= react with proteins. ( changes tertiary structure, enzyme denatured, no enzyme- substrate complex formed.
Iron ions= important in haemoglobin . Iron binds to and carries oxygen.
Sodium ions= important in helping other molecules move across membranes (co-transport), movement of sodium ions helps move other molecules across (glucose e.g)
Phosphate ions= essential compound of nuclei chemical acids (enable the formation of phosphodiester bonds)
