Theme - Energy Transformations Flashcards
What is ATP and what is it used for?
ATP (adenosine triphosphate) is a molecule used by higher organisms as an immediate energy store.
Energy is held in the bond that binds the third phosphate group to the molecule.
What is formed when ATP loses the third phosphorous molecule?
ADP + P + energy
What is the advantage of using carbohydrate as an intermediate step in storing energy?
It can be stored for longer and released when required, whereas only small levels of ATP can be stored safely in cells
What is PGA and when is it created?
Phospho-glyceric acid is a 3-carbon molecule. It is the first carbon molecule formed during photosynthesis, and forms the building blocks for more complex ones.
What does a light reaction do?
It used light energy to immediately create ATP, giving off oxygen as a by-product and storing hydrogen for later use.
What does a dark reaction do?
Following on from the light reaction, the ATP and hydrogen atoms convert carbon dioxide to PGA.
Which scientist deciphered carbon fixation
Melvin Calvin
What is the Calvin cycle also known as?
C3 cycle (as the first thing produced is a three carbon molecule (PGA)) Dark reactions
What happens in the C3/Calvin cycle?
An enzyme (RuBP - ribulose bi-phosphate) undergoes a carboxylase reaction with carbon dioxide to produce two molecules of PGA
What is Rubisco?
The enzyme that catalyses the reaction between RuBP and CO2 to give two PGA molecules
What happens to PGA when it is created in the rubisco reaction?
Half is converted back to RuBP to stay in the cycle, and half is used by cells for metabolism, structure and storage
Why are there so many Rubisco proteins in a plant?
The carboxylation process is inefficient and can limit the rate of photosynthesis, so having lots of the enzymes is a mitigation for this
What is the C2 cycle?
Formerly known as photorespiration, it uses Rubisco in an oxygenase cycle to release carbon
Approximately how much of carbon fixed in the C3 cycle is lost in the C2 cycle?
Approximately a quarter
What does the C2 cycle protection against?
Photoinhibition -if CO2 cannot be accessed quickly enough to carry out the reaction, oxygen is used instead. This removes ATP and hydrogen that could otherwise damage cells.
