How many neurons are found in the brain?

Someone me with this: a mineral' is determined by its actomic structure.

Hector is back from his morning run and is feeling light-headed because his energy is depleted which food item will provide him with a quick source of carbohydrates

What molecules will be best used to compare different species with the exact same sequence of amino acids? why would two species have the same protein even if the molecules in question is different? (hint: transcription to translation to protein).