Exam Questions Flashcards
Describe the structure of DNA.
Polymer of nucleotides.
Each nucleotide is formed by a deoxyribose, phosphate group and nitrogenous base. Phosphodiester bonds form between nucleotides. The two strands are held by hydrogen bonds.
Describe the role of DNA polymerase in the semi-conservative replication of DNA.
Joins adjacent nucleotides and catalyses a condensation reaction. Phosphodiester bonds form between the adjacent nucleotides.
What is the role of single stranded DNA fragments?
Act as a template and determines the order of bases.
What is the role of DNA nucleotides?
Forms complementary base pairs.
What are two features of DNA that are important for semi-conservative replication?
Weak hydrogen bonds between bases allow for the two strands to easily unzip.
Complementary base pairing allows for accurate replication.
Describe how an ATP molecule is formed from its component molecules.
ATP is made from a condensation reaction between adenine, ribose and three phosphate groups. ATP can be resynthesised in a condensation reaction between ADP and Pi catalysed by ATP synthase.
What are the two products of ATP hydrolysis?
ADP and Pi.
Give two ways in which ATP is a suitable energy source for cells to use.
Releases small amounts of energy. Doesn’t leave the cell.
Describe how ATP is resynthesised in cells.
It is resynthesised by ADP and Pi by ATP synthase during respiration.
Give two ways in which the hydrolysis of ATP is used in cells.
Provides energy for reactions.
Adds phosphate to other substances to make them more reactive.
State and explain the property of water that helps to prevent temperature
increase in a cell.
High Specific Heat Capacity. Buffers changes in temperature.
State and explain the property of water that can help to buffer changes in
temperature.
High Specific Heat Capacity. Takes a lot of energy to change temperature.
Give two properties of water that are important in the cytoplasm of cells.
For each property of water, explain its importance in the cytoplasm.
Polar molecule - acts as a solvent.
Solvent - reactions occur faster in solutions.
Why are the DNA strands pointing in opposite directions?
DNA has antiparallel strands. The nucleotides are arranged differently. Enzymes have active sites with specific shapes. Only the substrate with a complementary shape such as the 3’ end can bind with the active site.
Why can nucleotides only be added in a 5’ to 3’ direction?
The shapes of the 3’ end and 5’ end are different. DNA polymerase attaches the nucleotides to the strand and so it is only complementary to the 5’ end to the strand.
Humans synthesise more than their body mass of ATP each day. Explain why it is
necessary for them to synthesise such a large amount of ATP.
ATP is an immediate energy source. ATP only releases a small amount of energy at a time.
When glucose is respired what happens to the energy which is not incorporated into ATP?
It is released as heat.
