ATP
Laura Armstrong
Teacher
Contents
Recall Questions
This topic requires prior knowledge of RNA structure. You can test your knowledge on this below.
When is ATP produced?
During respiration (and some during photosynthesis in plants).
How is ATP similar to an RNA nucleotide?
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They both contain ribose sugar.
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They both contain a nitrogenous base.
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They both contain a phosphate group.
How is ATP different to an RNA nucleotide?
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ATP always has the base adenine whereas RNA nucleotides can contain adenine, cytosine, guanine or uracil.
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ATP has 3 phosphate groups whereas RNA nucleotides have 1 phosphate group.
Topic Explainer Videos
Check out this @LauraDoesBiology video that explains ATP or read the full notes below. Once you've gone through the whole note, try out the practice questions!
Structure of ATP
- ATP is a nucleotide derivative composed of:
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Adenine – nitrogenous base.
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Ribose – a pentose sugar.
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Three phosphate groups – key to energy storage and release.
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How ATP is Synthesised & Hydrolysed
How ATP is Synthesised
- ATP is synthesised from ADP (adenosine diphosphate) and Pi (inorganic phosphate) during:
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Photosynthesis in the chloroplasts of plants.
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Aerobic respiration in mitochondria.
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Anaerobic respiration in the cytoplasm.
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- You will learn more about how ATP is made during these processes in year 13, module 5.
- The synthesis of ATP from ADP and Pi is another example of a condensation reaction which involves the removal of water.
- The enzyme ATP synthase catalyses this reaction.
ADP + Pi ---> ATP (+ water)
How ATP is Hydrolysed
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ATP is hydrolysed into ADP + Pi via a hydrolysis reaction using the addition of water.
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ATP hydrolase catalyses this reaction, releasing energy for biological processes.
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ATP hydrolysis releases energy.
ATP (+ water) ---> ADP + Pi
Advantages and Disadvantages of ATP
Advantages:
- Immediate energy source – hydrolysis occurs in a single-step reaction.
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Energy-efficient – releases energy in small, manageable amounts.
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Easily synthesised – continuously regenerated in cells from ADP and Pi.
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Facilitates metabolic reactions – Pi released from ATP hydrolysis can phosphorylate other molecules, making them more reactive / less stable.
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ATP is used in active transport, muscle contraction, and biosynthesis, such as protein synthesis – essential for cell functions.
ATP has some disadvantages despite being an efficient energy source:
- ATP cannot be stored in large quantities because it is unstable and breaks down quickly.
- ATP cannot be transported between cells so all cells must continuously resynthesise ATP.
- Cells must produce ATP where it is needed, meaning they require many mitochondria to generate ATP efficiently.
Key Terms
- ATP (Adenosine Triphosphate): A nucleotide derivative that transfers energy in cells.
- Phosphorylation: Addition of a phosphate group to a molecule.
- ATP Synthase: Enzyme that catalyses ATP production.
- ATP Hydrolase: Enzyme that catalyses ATP hydrolysis.
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Exam Tip
Always link ATP’s role to specific processes in cells, such as muscle contraction, active transport, and phosphorylation of molecules.
Make sure you can compare and contrast a molecule of ATP with an RNA nucleotide.
No answer provided.
ATP is used in many biological processes. Explain how the properties of ATP make it a suitable energy source for cells. (4 marks)
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ATP releases energy in small, manageable amounts, preventing energy waste.
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ATP hydrolysis is a single-step reaction, making energy release immediate.
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ATP can be rapidly resynthesised from ADP and Pi.
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ATP phosphorylates other molecules, making them more reactive.
Practice Question
Try to answer the practice question from the TikTok on your own, then watch the video to see how well you did!