Amino acid requirements

Dependence on animal meat

Plants are a poor source of protein. Seeds are the best, but still not great--and their distribution of the various amino acids is not uniform. Yet, we require amino acids that are present in small quantities in some seeds. For strict herbivores, it's even worse--normal plant cells have rather little protein overall. We can get a clue about this problem from cows, which normally eat grass. They swallow their food into their rumen, the first of their stomachs, where methanogenic bacteria break down the cellulose. Cows regurgitate this material as "cud" and chew it further, before swallowing it into the traditional intestinal system. Their intestinal system is very long; there is plenty of opportunity to break down the plant material and extract every bit of nutrition in it.

But, whatever protein is in their food at the outset, most of it is digested and consumed by the ruminal bacteria! As it turns out, the lengthy intestine of a cow is a very good factory for growing more of these bacteria--many of which die and are digested by the cow itself. To a large extent, it is from these digested bacteria that cows obtain most of their amino acids.

DNA sequence data from numerous genomes indicate that animals, in general, lack the enzymes to build the essential amino acids. Herbivores, such as cows, obtain them from their gut bacteria--much as they obtain vitamin B12. Carnivores like wolves, and hunters like humans have too short a digestive system to extract either vitamin B12 or amino acids from the intestinal bacteria. Therefore, they must eat protein, the best source of which is animal meat. Note that the development of hunting parallels the shift from a wide abdomen (e.g. in Lucy) to a narrow one (e.g the Nariokotome boy), as the herbivore's large digestive tract diminished to an omnivore's shorter one. This was advantageous for running long distances (something humans excel at), but had the unselected disadvantage of making us dependent on a good source of protein in our diet, as well as unable to absorb sufficient vitamin B12.

ОТкуда пошли сами понятия "вопрос" и "ответ" ?

как заставить Speed Fan при включении компьютера работать кулер на камне на мин оборотах ??

вопрос-то сгорит-не сгорит? (моторчик кетайский)

Это тебе у Задорнова нужно спросить, он горазд выдумывать происхождения разных слов

который выступает там

вопрос-то сгорит-не сгорит?

Кто такие хипстеры?

Duke1 так это тоже что и хиппи?

Это тебе у Задорнова нужно спросить, он горазд выдумывать происхождения разных слов

Только спросить нужно у Задорнова, который выступает там, а не у того, который здесь.

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