Topic 1 - Biological Molecules Flashcards
Give the structure of a DNA nucleotide
Phosphate + Penrose sugar + nitrogenous base
How are polynucleotides formed?
What type of reaction is this?
Many nucleotides join up in a condensation reaction.
Phosphodiester bond forms between deoxyribose sugar and phosphate group.
What does the chain of phosphates and sugars make ?
The Sugar-phosphate backbone
What type of bond forms between one Pentose sugar and a phosphate group?
Ester bond
What is the structure of DNA ?
- Polymer forms Double helix
-Long chain of nucleotides
What are the four types of nitrogenous bases?
-Adenine
-Thymine
-Cytosine
-Guanine
What bond joins two DNA polynucleotide strands?
Hydrogen bonds between the bases
What is complementary base pairing ?
Each base only join with a specific partner.
A with T
C with G
How many hydrogen bonds form between
A and T
C and G
2 between A and T
3 between C and G
Why are the polynucleotide strands antiparallel ?
They run in opposite directions to form a double helix
Give four ways in which the structure of DNA and RNA is different ?
-DNA has deoxyribose but RNA has ribose
- DNA has thymine but RNA has uracil
-DNA have a double polynucleotide strand but RNA forms a single polynucleotide strand.
- DNA is long but RNA is shorter strands
Why does DNA replicate before division ?
So that each new cell has the full amount of DNA
What is the meaning of semi-conservative replication?
-Half of the strands in each new DNA molecule are from the original DNA molecule.
What is the role of DNA helicase ?
-Enzyme which breaks the hydrogen bonds between bases on the two polynucleotide strands.
How does complementary base pairing work ?
-Free floating DNA nucleotides are attracted to their complementary exposed bases on each template strand.
What type of reaction joins the nucleotides of the new strand together?
Condensation reaction
What is the role of DNA Polymerase
-Joins the nucleotides by a condensation reaction.
-Hydrogen bonds form between the strands.
What is the structure of ATP ?
Adenine + Ribose sugar + 3 phosphate groups
What are the products of the hydrolysis of ATP ?
ADP and Phosphate group (+energy)
What type of bond is broken in hydrolysis of ATP ?
Phosphate bond
What enzyme catalyses the breakdown of ATP ?
ATP hydrolase
Why is a water a polar molecule ?
- shared electrons pulled towards oxygen
- oxygen atom is slightly negative
- hydrogen atom has slightly positive charge
- Creates a polar molecule
What type of bond forms between slightly positive H and slight negatively charge in another molecule ?
Hydrogen bonds
Why is water a good solvent ?
- Water is polar ( one negatively charged end and one positively charged end)
-So slightly positive changed end is attracted to slightly negative end.
-Ions get totally surrounded by water molecules so they dissolve.
What does high latent heat of vaporisation mean ?
Lots of heat is required to change it from a liquid to gas.
Why is high latent heat of vaporisation a useful property of water ? And how does it work
-Takes a lot of heat energy to break hydrogen bonds between water molecules.
-So it has a high latent of vaporisation a lot of energy is used up when water evaporates.
-This is useful because it cools down organisms as because water loss through evaporation helps them to cool down ( eg humans sweat )
Why is a buffer a good property of water ?
-Hydrogen bonds between molecules absorb lots of energy.
-water has a high specific heat capacity.
-water doesn’t experience rapid temperature changes so helps to maintain a constant internal body temperature.