Energy and ATP
- Respiration involves the gradual breakdown of energy in a number of small steps, as opposed to the rapid release of energy.
- Glucose is broken down by means of a number of enzyme controlled reactions.
- This provides the release of small quantities of energy at each stage.
- These reactions produce a molecule called ATP
- Adenosine Triphosphate
The Structure of ATP
- ATP is a neucleotide.
- Orgainc base called adnenine.
- Has a five carbon sugar, Ribose
- Sequence of three phosphate groups linked together by two high energy bonds and one low energy bond.
The Importance of ATP
- Reactions with glucose release a large amount of energy which would release a lot of heat, thus denaturing and destroying the cells.
- Living organisms use the gradual release of energy in small steps to produce ATP.
- ADP is converted to ATP by the addition of phosphate molecules
- Energy is taken up by this reaction.
- This makes it an ENDERGONIC reaction.
- 30KJmol-1 is needed to add each phosphate molecule.
- ATP can be hydrolysed to release energy as is needed.
- When ATP is broken down it forms ADP and a phosphate molecule as well as 30KJmol-1.
- This is an EXERGONIC reaction as energy is released.
- The reaction of ATP to ADP is catalysed by ATPase
When a phosphate molecule is transferred from ATP to another molecule it makes it more reactive, thus lowering the ACTIVATION ENERGY of that molecule.
ACTIVATION ENERGY- The energy needed top start a chemical reaction.
The addition of a phosphate to ADP is called PHOSPHORYLATION.
ATP is a means of transferring free energy from energy rich compunds such as glucose, to cellular reactions where energy is needed.
There are three types of PHOSPHORYLATION:
- OXIDATIVE PHOSPHORYLATION - Occurs on the membrane os the mitochondria. Involved in the process of electron transport.
- PHOTOPHOSPHORYLATION - Occurs on the membranes of the chloroplasts during photosynthesis.
- SUBSTRATE LEVEL PHOSPHORYLATION - Occurs when phosphate groups are transferred from donor molecules to ADP to make ATP.
The Advantages of using ATP as an energy source
ATP Vs. GLUCOSE
- Only one enzyme is required release energy from ATP, Glucose needs many.
- ATP releases energy in small amounts where needed. Glucose contains large amounts of energy which are not needed immediatley.
- ATP provides a common source of energy for many different chemical reactions.
THE UNIVERSAL ENERGY CURRENCY - Source of energy for many different chemical reactions
The roles of ATP
METABOLIC PROCESSES - To synthesise large, complex molecules from smaller, simpler ones e.g. DNA from neucleotides
ACTIVE TRANSPORT - To change the shape of carrier proteins in the plasma membrane
MOVEMENT - For muscle contraction
NERVE TRANSMISSION- NaK pumps activley transport NA and K ions across the plasma membrane
SECRETION - The packaging and transport of secretory products into vesicles and cells
ATP is the short term energy store of the cell.
Called THE UNIVERSAL ENERGY CURRENCY as ATP provides a common source of energy for many different chemical reactions
Conversion of ATP to ADP is a reversible reaction
ATP has unstable phosphate bonds and therefore is a good immediate energy source
FATS and CARBOHYDRATES are far ebtter long term energy sources
ATP is not sotred, it is synthesised as required
Cells do not store large quantities of ATP but maintain a supply which only lasts a few seconds