Eli5: How does a microscopic sperm after fertilization can form so many complex Organs and chemicals, as atoms can’t be created nor destroyed? Also if neurons can’t divide, how did it came into existence in the first place?
In: Biology
The sperm cell carries information and basically nothing else. The information in the sperm and the egg combine to form the instructions for building an organism, and then the developing organism takes in nutrients which it uses to grow and develop.
Atoms can be created and destroyed, but fortunately high-energy nuclear physics isn’t happening in your mom.
The atoms in you are instead scavenged from food and repurposed.
The sperm and egg cells contain what’s essentially an instruction manual for how to build a human. The fertilized egg cell then begins to follow that manual, procedurally generating a human from the instructions using materials the mother gets from her meals.
The finished adult nerve cells are highly specialized and do not divide or repair themselves easily or often, but during the early stages of development more generic “stem” cells build the nervous system. Once the system is closer to completion, they divide one final time and create the finalized less malleable neurons.
Atoms can’t be created or destroyed, but they can be converted from food into body parts. Before birth, the mother processes food into components for the baby to use. After birth, well humans eat all the time.
Stem cells can differentiate themselves into many types of cells, including neurons.
How can it form so many different things?
DNA is like an instruction manual on how to form all those things.
How can it grow if atoms can’t be created or destroyed?
Because after the sperm fertilizes the egg, that zygote (the combination of the two) implants itself into the wall of the mothers uterus, there it absorbs nutrients from the mother and uses that to grow.
Neurons dividing?
You’re right (most) neurons can not divide. Instead there are other special cells in charge of making neurons. Kind of like a factory pumping out new neurons to grow.
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