2.3 Energy and ATP Flashcards
What is ATP (adenosine triphosphate)
Adenosine triphosphate (ATP) is the energy-carrying molecule that provides the energy to drive many processes inside living cells
Photosynthesis turns water and carbon dioxide into complex molecules.
Plants and animals then oxidise these organic molecules to make ATP which is the main energy source to carry out processes in cells
Describe the structure of ATP
. It has 3 parts as it is a phosphorylated macromolecule
. Adenine: a nitrogen storing organic base
. Ribose: A sugar molecule with a five carbon ring structure (pentose sugar) that acts as a backbone to which the other parts are attached
. Phosphates: A chain of three phosphate groups
How does ATP store energy
. Adenosine triphosphate is a nucleotide and has three phosphate groups
. The bonds between these phosphate groups are unstable so have a low activation energy which means they are easily broken
. When they break they release lots of energy
Usually in living cells only the terminal phosphate is removed which makes it ADP adenosine diphosphate
What is the reaction for ATP to ADP
What enzyme catalyses the reaction
A hydrolysis reaction
ATP + H20 –> ADP + Pi + E
the pi is inorganic phosphate and E is energy
The enzyme ATP hydrolase catalyses the reaction
How can ATP be reformed after the reaction forming ADP
What type of reaction is it
What enzyme is used in this reaction
It’s a reversible reaction so energy can be used to add an inorganic phosphate to ADP to reform ATP
It’s a condensation reaction so a molecule of water is removed
The enzyme ATP synthase is used to catalyse the reaction
The synthesis of ATP from ADP involves the addition of a phosphate molecule to ADP
When does this occur
(3 ways)
Photophosphorylation
Oxidative phosphorylation
substrate level phosphorylation
. Photophosphorylation
In chlorophyll containing plant cells during photosynthesis
. Oxidative phosphorylation
In plant and animal cells during respiration
. Substrate-level phosphorylation:
In animal and plant cells when phosphate groups are transferred from donor molecules to ADP
Why is ATP not a good long term energy store
Its phosphate bonds are very unstable so can be broken easily
How much ATP do cells need to store
It’s the immediate energy source of a cell so cells only need to maintain a few seconds supply
Why is the structure of ATP similar to that of nucleotides
It’s another type of nucleic acid:
It’s a phosphorylated nucleotide
So it is very structurally similar to the nucleotides that make up RNA and DNA
It contains a sugar, phosphates, and a base
Why is ATP a better immediate energy source than glucose?
4 reasons, and one that ATP and glucose have in common
. Each ATP molecule releases less energy than each glucose molecule, so the energy for reactions is released in smaller quantities which are more manageable than great amounts released by glucose.
This means less energy is wasted, and no cells overheat from the wasted energy
. The hydrolysis of ATP to ADP is a single reaction (only one bond has to be hydrolysed) that releases immediate energy whilst the breakdown of glucose is a long series of reactions so takes longer
. Atp can enable phosphorylation to make other compounds more reactive, glucose can’t do this
. ATP is too big to leave the cell so the. cell always has an immediate source of energy, all cells have their own constant supply
. Both are small and soluble so can be easily transported around a cell in the cytoplasm, providing energy for chemical reactions.
How is ATP used in metabolic processes?
. It provides the energy needed to build up macromolecules from their basic units, eg making starch from glucose
How is ATP used for movement?
ATP provides the energy needed for muscle contraction, it provides the energy for the filaments of muscle to slide past each other and therefore shorten the overall length of a muscle fiber
How is ATP used for active transport?
. It provides the energy to change the shape of carrier proteins in plasma membranes
. This allows molecules or ions to be moved against a concentration gradient
How is ATP used in secretion?
. It forms the lysosomes necessary for the secretion of cell products
How is ATP used for the activation of molecules
. The inorganic phosphate released during the hydrolysis of ATP can be used to phosphorylate other compounds to make them more reactive.
. Thus lowering the activation energy in enzyme catalyzed reactions.
Eg the addition of phosphate to glucose molecules at the start of glycolysis
