Biology: ATP and Cellular Energy Currency
How cells store, transfer, and use energy
Biology: ATP and Cellular Energy Currency
How cells store, transfer, and use energy
Biology - Grade 9-12
- 1
ATP is often called the energy currency of the cell. Explain what this phrase means in terms of how cells use ATP.
Think about money being exchanged for goods and services.
ATP is called the energy currency of the cell because it stores usable energy in its phosphate bonds and can quickly transfer that energy to power cellular work. - 2
Name the three main parts of an ATP molecule.
An ATP molecule is made of adenine, ribose sugar, and three phosphate groups. - 3
Write the general equation for ATP hydrolysis and explain what happens to the energy.
Hydrolysis means breaking a bond using water.
The general equation is ATP plus water becomes ADP plus inorganic phosphate plus energy. The released energy can be used to power cellular processes such as transport, movement, and chemical reactions. - 4
What is phosphorylation, and how can it help a cell do work?
Phosphorylation is the addition of a phosphate group to a molecule. It can help a cell do work by changing the shape, energy, or activity of the molecule that receives the phosphate. - 5
A cell uses ATP to pump sodium ions out of the cell against their concentration gradient. Explain why ATP is needed for this process.
Moving against a gradient is like pushing an object uphill.
ATP is needed because moving sodium ions against their concentration gradient requires energy. ATP provides energy for the protein pump to change shape and move the ions. - 6
Compare ATP and ADP in terms of phosphate groups and stored energy.
ATP has three phosphate groups and contains more usable stored energy. ADP has two phosphate groups and contains less usable stored energy than ATP. - 7
During cellular respiration, glucose is broken down and ATP is produced. Explain why cells do not release all of glucose's energy at once.
Controlled energy release is safer and more efficient than a single burst.
Cells do not release all of glucose's energy at once because a sudden release would waste much of the energy as heat. Cellular respiration releases energy in controlled steps so more of it can be captured in ATP. - 8
Glycolysis uses 2 ATP molecules at the beginning and produces 4 ATP molecules by the end. What is the net gain of ATP from glycolysis?
Net gain equals ATP produced minus ATP used.
The net gain from glycolysis is 2 ATP molecules because 4 ATP are produced and 2 ATP are used. - 9
Explain how ATP helps connect exergonic reactions and endergonic reactions in a cell.
ATP helps connect exergonic and endergonic reactions through energy coupling. Energy released by ATP hydrolysis can be used to drive endergonic reactions that require energy. - 10
A muscle cell needs ATP during contraction. Describe one way ATP is involved in muscle movement.
Muscle contraction depends on repeated protein movement.
ATP is involved in muscle movement because it allows myosin proteins to detach from actin and reset for another contraction cycle. - 11
Why is ATP not a good molecule for long-term energy storage compared with fats or starches?
ATP is not good for long-term energy storage because it is used quickly and is unstable for storing large amounts of energy. Fats and starches store much more energy in a more stable form. - 12
In aerobic respiration, most ATP is made during oxidative phosphorylation. Identify the cell structure where this process occurs in eukaryotic cells.
This organelle is often described as the powerhouse of the cell.
In eukaryotic cells, oxidative phosphorylation occurs in the mitochondria, mainly across the inner mitochondrial membrane. - 13
Explain why fermentation allows glycolysis to continue when oxygen is not available.
Glycolysis needs NAD plus to accept electrons.
Fermentation allows glycolysis to continue by regenerating NAD plus from NADH. This lets glycolysis keep producing a small amount of ATP without oxygen. - 14
A diagram shows ATP changing into ADP plus phosphate, then ADP plus phosphate changing back into ATP. Describe what is happening in this cycle.
The diagram shows the ATP cycle. ATP releases energy when it becomes ADP and phosphate, and energy from food or sunlight can be used to rebuild ATP from ADP and phosphate. - 15
Compare the roles of ATP and NADH in cellular respiration.
One molecule is used directly, and the other helps produce more of it.
ATP directly provides energy for cellular work, while NADH carries high-energy electrons to the electron transport chain. NADH helps cells make more ATP, but it is not usually the direct energy source for most cellular work.