Biological molecules 2 Flashcards
What does DNA stand for?
Deoxyribonucleic acid
What does a DNA nucleotide consist of?
Phosphate, nitrogen base, deoxyribose sugar
What does an RNA nucleotide consist of?
Phosphate, nitrogen base, ribose sugar
What does RNA stand for?
Ribonucleic acid
What bases can a DNA nucleotide have?
Adenine, cytosine, guanine, thymine
What bases can an RNA nucleotide have?
Adenine, cytosine, guanine, uracil
What molecule is usually longer, DNA or RNA?
DNA
What is the function of RNA?
To transfer genetic information from DNA to the ribosomes which read the RNA to make polypeptides
Why is DNA such a stable molecule?
It has multiple hydrogen bonds between bases and the ladder is held together by sugar-phosphate backbones
How many hydrogen bonds do cytosine and guanine form?
3
How many hydrogen bonds does adenine and thymine form?
2
What bond forms between the phosphates and sugars in the DNA ladder?
Phosphodiester bond
What is the process of DNA replication in the semiconservative method?
- DNA helicase separates the strand by breaking the hydrogen bonds
- DNA polymerase binds the complimentary nucleotides to the strands
- The leading strand is formed first, continuously from 5’ to 3’
- The lagging strand is formed from 5’ to 3’ but because the strands are antiparallel, this creates okazaki fragments
Who came up with the idea of semi-conservative replication?
Watson and Crick
Who proved the theory of semiconservative replication?
Meselson and Stahl
What was the process of the experiment that proved semi-conservative replication?
- Two samples of bacteria were grown, one in a nutrient broth of light nitrogen and the other of heavy nitrogen
- A sample of DNA was taken from each bacteria and spun in a centrifuge; the DNA from the heavy nitrogen settled lower down the tube
- The bacteria grown in heavy nitrogen were taken out and put in a broth containing only light nitrogen
- After one round of DNA replication, another DNA sample was taken out and spun in the centrifuge
- Because DNA replication is semi-conservative, the new bacterial molecules contained one strand of heavy nitrogen DNA and one strand of light nitrogen DNA and therefore settled out somewhere between where the light nitrogen DNA and heavy nitrogen DNA settled out
What does ATP stand for?
Adenosine triphosphate
What is ATP made up of?
Adenine, ribose sugar and a chain of three phosphate groups (it’s therefore considered a nucleotide)
Why does ATP have low activation energy?
Because it contains unstable bonds
What is the purpose of ATP?
To release lots of energy when broken
How does ATP release energy?
By losing a phosphate molecule
What is the equation for the breakdown of ATP?
ATP + H2O –> ADP + Pi + E
One phosphate is lost (Pi) which releases energy (E) and leaves adenosine diphosphate (ADP)
What kind of reaction is the breakdown of ATP?
A hydrolysis reaction
What is phosphorylation?
When a phosphate is added
What enzyme catalyses the reaction of the breakdown of ATP?
ATP hydrolase
What enzyme catalyses the reaction for phosphorylation?
ATP synthase
What kind of reaction is phosphorylation?
A condensation reaction
What is an inorganic phosphate?
A phosphate that isn’t attached to another carbon containing molecule
What is the main role of the iron ion?
It forms part of the structure of haemoglobin which carries oxygen around the body
What is the main role of the hydrogen ion?
It determines the pH of a solution which in turn affects enzymes
What is the main role of the phosphate ion?
It forms part of ATP and nucleotides and is also involved in phosphorylation
What is the main role of the sodium ion?
It’s involved in co-transport of glucose and amino acids
Why is water described as a dipolar molecule?
Because oxygen has a slight negative charge and hydrogen has a slight positive charge, causing hydrogen bonds to form between the water molecules
What is the definition of specific heat capacity?
The amount of energy required to increase 1kg of a substance by 1°C
What is latent heat vaporisation?
The amount of energy required to evaporate 1kg of a substance
What is cohesion?
The tendency of water molecules to stick together
What is a solvent?
A liquid that other substances dissolve in
Why is water a good solvent?
The positive region of water will be attracted to negative ions and the negative region of water will be attracted to positive ions, causing water to completely surround and dissolve ions
What gives water a high specific heat capacity and when is this useful?
Hydrogen bonds give water a high specific heat capacity which is important for marine ecosystems, as it buffers changes in temperature, keeping them stable
Why does water have a high latent heat of vaporisation and when is this useful?
Because a lot of energy is required to overcome the hydrogen bonds
This means that organisms can use evaporation from sweating to cool down without losing too much water
Why is water cohesive and when is this useful?
Because water is dipolar, the molecules tend to stick together which makes it easier got transporting substances in organisms (e.g. xylem)
It also creates surface tension, which creates habitats for insects like pond skaters
