3.1.6 ATP Flashcards
ATP Struct (draw struct)
The ATP molecule (Figure 1) is a phosphorylated macromolecule.
It has three parts:
- adenine - a nitrogen-containing orga nic base
- ribose - a sugar molecule with a 5-carbon ring structu re (pentose sugar) that acts as the backbone to which the other parts are attached
- phosphates - a chain of three phosphate groups.
How does ATP store energy? and equation
Adenosine triphosphate (ATP) is a nucleotide and as the name suggests, has three phosphate groups.
These arc the key to how ATP stores energy.
The bonds between these phosphate groups are unstable and so have a low activat ion energy, which means they are easily broken.
When they do break they release a considerable amount of energy.
Usually in living cells it is only the terminal phosphate that is removed, according to the equation:
ATP ⇔ ADP + Pi
What enzyme is used in hydrolysis of ATP, what is this product of hydrolysis used for, name of process
Water is used in a reaction catalysed by ATP hydrolase (ATPase) to break the bond between the second and third Pi group – releasing energy
The Pi group is transferred to other molecules to make them more reactive so that they have the activation energy to take part in another reaction – this is called phosphorylation
Draw and recall ATP + ADP cycle
ATP hydrolysed into ADP by ATP hydrolase
Energy released for cellular work- Pi for phosphorylation
ATP synthase condenses ADP and Pi into ATP
Condensation into ATP three ways
As quickly as ATP is used up, it is resynthesized by condensing together molecules of ADP and inorganic phosphate groups (Pi) using ATP synthase
This requires energy from carbohydrate or lipid molecule hydrolysis during respiration to resynthesize ATP
Photophosphorylation – occurs in the chlorophyll during photosynthesis (thylakoid membranes in the chloroplasts in PLANTS only)
Oxidative phosphorylation – occurs in the mitochondria during aerobic respiration, involves the electron transport chain (part of respiration)
(plant and animal cells during respiration)
Substrate-level phosphorylation – when phosphate groups are transferred from donor molecules to ADP e.g in glycolysis
ATP cannot be stored so has to be continuously made within mitochondria and the cells that need it
Advantages of ATP (an one small disadvantage- better alternatives for this)
Only one enzyme needed to release immediate energy from ATP (ATPase). It is a single reaction. Glucose is a long series of reactions and the energy release takes longer.
ATP released energy in smaller, more manageable amounts when and where needed. It is an immediate energy source whereas glucose contains large amounts we don’t need straight away
ATP is a common source of energy for a multitude of chemical reactions, increasing the efficiency of the cells in the body. (International energy currency)
Dis: The same feature that makes ATP a good energy donor, namely the instability of its phosphate bonds, is also a reason why it is not a good long-term energy store. Fats, and carbohydrates such as glycogen, serve this purpose far better
ATP uses
Metabolic Processes – Building large complex molecules from smaller, simpler molecules. For example ATP is required in DNA and Protein synthesis
Active Transport – ATP can change the shape of carrier proteins in plasma membranes to allow molecules/ions to be moved against the concentration gradient.
Movement – Provides the energy for muscle contraction
Secretion – The packaging and transport of secretory products into vesicles in cells
Activation of molecules – Pi can be used to phosphorylate other compounds to make them more reactive, lowering their activation energy. Eg. In glycolysis
Give two ways in which the properties of ATP make it a suitable source of energy in biological processes
- Energy released in small / suitable amounts;
- Soluble;
- Involves a single / simple reaction;
- In context of release, not storage. Ignore producing energy / manageable amounts. 2. Reject “broken down easily / readily”. Reject “quickly / easily resynthesised”.
