How Do Cells Get Energy

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enotechris | College Teacher | (Level 2) Senior Educator

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The mitochondria are organelles within an animal cell that provide energy for the rest of the cell's functions through the creation of the energy molecule ATP by the chemical reactions occuring in the Krebs Cycle.  In plant cells, which do not contain mitochondria, the energy for cellular functions is created by the chloroplasts, which, like a mini solar cell, convert sunlight into useful energy by the creation of sugar molecules through the process of Photosynthesis. 

See a more detailed description of the molecular chemistry involved in both these energy producing processes by watching the video below:

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hannaberry | Teacher | (Level 1) eNoter

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In cells, energy is stored in the form of ATP.   ATP = Adenosine Triphosphate

How does ATP give cells energy?

ATP breaks apart and releases its energy.

When ATP breaks apart, it releases energy and loses a phosphate group. That means that it is now ADP.

Plant cells get energy by a process called photosynthesis. Plants use energy from sunlight to grow and make their own energy. So when a plant combines the energy from sunlight with water and carbon dioxide from the air, it gets energy. A chemical reaction must occur everytime. The equation is as followed: 6H2O + 6CO2 (+ light energy (the sun)  = C6H12O6 + 6O2 Inside each plant cell is an organelle called chloroplast. Chloroplast is where the photosynthesis reaction takes place.



Cellular respiration is a chemical process in which glucose molecules are broken down to release energy (ATP) for cellular functions.

Animals get energy by eating food. When humans eat food the following happens:

1. We break our food down into small molecules

2. We use the energy stored in the bonds in our food to make ATP

3. A small amount of the food becomes waste

Like photosynthesis, cellular respiration has a specific chemical reaction that happens every time.

The cellular respiration equation is as followed: O2 + C6H12O6 = CO2 + H2O + Energy (ATP)



Cellular respiration can be divided into 2main parts.

1.Anaerobic respiration -

Does NOT need oxygen!

Happens in the cytoplasm of a cell

2.Aerobic respiration 
Requires oxygen

Happens in the mitochondria of a cell


1. Glycolysis (anaerobic respiration process)

2. Depends on the conditions of the cell

During aerobic respiration, 2 processes take place in the mitochondria.

1.Kreb’s Cycle
2.Electron Transport Chain
Anarobic Respiration- Releasing energy from food molecules by producing ATP WITHOUT oxygen


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heavenworld678 | Student, Grade 9 | (Level 1) eNoter

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Cells need a source of energy, they get this energy by breaking down food molecules to release, the stored chemical energy.This process is called 'cellular respiration'. The process is happens in all the cells in our body. Oxygen is used to oxidize food, main oxidized food is sugar(glucose). Carbon dioxide and Water are released as waste products. Respiration releases some heat energy, but most are trapped as energy in other chemicals. Chemical energy can be used for the contraction of muscle movements, active transport of molecules and ions, building proteins, cell division etc. The reaction is; C6H12O6 + 6O2= 6CO2 + 6H2O + energy. (glucose+ oxygen=carbon dioxide + water + energy). This is called aerobic respiration, because of the presence of oxygen. But in anaerobic respiration, the oxygen is not present so the glusose isnt broken down completely, and less energy is released. So, the summary is that the cells get energy by the oxidation of food/by cellular respiration!

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pettry | Student, Undergraduate | eNotes Newbie

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A cell gets energy through cell metabolism. Metabolism involves anabolism and catabolism.Metabolism occurs in the cell cytosol as well as in mitochondria. Energy is released in packages.This is through ATP,cells' energy currency.Hydrolysis of ATP involves breakdown of bonds,and bond breakdown releases energy.Why ATP? ATP is highy negatively charged hence has high energy potential.