Connect ATP with cellular energy demand
Explain how ATP supports active transport, movement and anabolic reactions such as DNA replication and protein synthesis.
A Level; Cambridge International Biology 9700, 2028–2030. Written practice is self-checked; practical investigations need supervised work and human subject-teacher review remains pending.
Before you begin
- ATP transfers energy for cellular work, and enzymes control metabolic reactions.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which transport process moves a substance against its gradient?
What you will learn
- Relate energy use to active transport and movement
- Explain how ATP supports anabolic reactions
Connect respiration energy with movement and transport
| Feature | Meaning |
|---|---|
| Muscle contraction | Energy for movement |
| Active transport | Energy for uptake against a gradient |
| Temperature regulation | Energy supports a constant body temperature |
Build the explanation
Cells need a usable energy supply to carry out work. ATP hydrolysis can be coupled to active transport, which moves substances against a concentration or electrochemical gradient, and to movement such as muscle contraction. ATP also supplies energy for anabolic reactions that build larger molecules, including DNA replication and protein synthesis. ATP is continually regenerated, so cells transfer energy through a cycle rather than storing all usable energy in one large ATP reserve.
Apply it carefully
Do not say ATP creates energy: energy is transferred and transformed. Link ATP hydrolysis to a process that needs energy, and distinguish active transport against a gradient from passive diffusion down a gradient. DNA replication and protein synthesis are examples of biosynthesis; ATP is not the only molecule involved in their chemistry.
Pause and explain
Name one anabolic process that requires energy from ATP coupling.
Worked example
Why does active transport need an energy supply?
Show the worked solution
- Compare the direction of movement with the gradient.
- Movement against a gradient requires energy to be coupled to transport.
Answer Active transport moves substances against a concentration or electrochemical gradient, so energy from ATP hydrolysis is coupled to the transport process.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Use active transport and protein synthesis to explain two different cellular energy demands.
Give me a hint
One moves substances; the other builds a polymer.
Compare my reasoning
- Active transport moves a substance against its gradient.
- Protein synthesis joins amino acids to form a polypeptide; ATP-coupled reactions supply energy.
Active transport needs an energy input to move substances against a gradient. Protein synthesis is anabolic: it joins amino acids to build a polypeptide, and ATP-coupled reactions supply energy for cellular steps in the process.
Look for these in your work
- Gradient direction stated
- Anabolic synthesis described
- ATP linked to both uses
A student says diffusion needs ATP because molecules are moving. Correct the explanation by distinguishing it from active transport.
Give me a hint
Compare the direction of movement, not whether particles move at all.
Compare my reasoning
- Diffusion down a gradient is passive.
- Active transport moves against a gradient and requires energy.
Movement alone does not mean ATP is needed. Diffusion down a gradient is passive, whereas active transport moves substances against a gradient and needs an energy input that is coupled to transport.
Look for these in your work
- Passive diffusion distinguished
- Active transport distinguished
- Energy claim corrected
A cell is rapidly copying DNA. Explain why a rise in ATP use is plausible without claiming ATP is the genetic material.
Give me a hint
Separate the template molecule from the energy-transfer molecule.
Compare my reasoning
- DNA is copied by anabolic reactions that build a new strand.
- ATP supplies energy for coupled cellular steps; DNA stores the genetic information.
DNA replication builds a new DNA strand using anabolic reactions, so ATP-coupled steps contribute to the energy demand. DNA is the genetic material; ATP is an energy-transfer molecule, not the information store.
Look for these in your work
- Anabolic synthesis identified
- ATP role stated
- DNA and ATP roles separated
Common mistakes
- Saying ATP creates energy
- Claiming every movement of a molecule requires ATP
- Calling ATP the genetic material
What can you explain now?
Which transport process moves a substance against its gradient?
Compare with the explanation
Active transport
Moving against a gradient requires an energy input.
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Make it stick
How does ATP support active transport and anabolic reactions?
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