Turning complex molecules into simple ones through the digestion allows us to survive and thrive, but how does this work? What happens when we eat something, and how does our body transform what we eat into actual “energy” that can be used by cells to sustain their functions?
The first steps of mechanical digestion
Chemical digestion: chewed, tore, ground into small pieces, mixed with saliva and acidified and pressed by the stomach until it turns into a liquid paste called chyme
- The bolus keeps being pushed towards the intestines thanks to a series of contraction and relaxation of the digestive apparatus’ muscles: a process called peristalsis
- Inside the intestine, the Chyme keeps being processed by numerous enzymes and other substances, that will eventually break it down into chyle
Fats and proteins: storing energy and using it for building
While glucose is the main “fuel” used to produce energy, fats are mostly packed into small units called lipoproteins and then transported into various tissues (mostly the adipose one, or the body fat), where they are stored for later use.
- Proteins, on the other hand, are broken into elementary units called amino acids that are used as “bricks” to build new proteins, enzymes or even tissues such as the muscular one.
Biochemistry for dummies: let’s get to the point
To explain all this process through a metaphor, try imagining ATP like actual electric energy.
- If you got electricity, you can light your lamps or turn on your fridge or television.
- In your body, the “lamp” is a metabolic reaction, and the “fridge and television” could be a muscular contraction or cell producing a new enzyme.
The energy inside the human body: Adenosine Triphosphate and the Krebs Cycle
To keep our health, we need energy, and this energy is obtained through various pathways called metabolism.
- The most common currency used to exchange energy between cells is ATP, a small coenzyme used by cells as an energy source in almost all their processes.
- ATP needs to be “produced” by the body through a series of biochemical reactions.
- During these reactions, the energy stored within Acetyl-CoA is “liberated” to generate ATP.
REFERENCES
Kim E. Barrett, Fayez K. Ghishan, Juanita L. Merchant, Hamid M. Said, Jackie D. Wood.
How nutrients are transformed into energy after absorption
The three basic units in which all foods we eat are broken into are carbohydrates, fats and proteins, and together they constitute the macronutrients.
- Some of these molecules are still large and complex ones, and thus they need to be further broken into simpler units that will be then used to produce Acetyl-CoA through three different metabolic pathways: Glycolysis (for carbohydrates), Beta-oxidation (for fats), and the Transamination (for proteins).
- Most commonly used by almost all cells, glucose is the “fuel” used by most cells.
