The yellow leaf was not exposed to the sun so it can't produce sugar.
Explanation:
The yellow region of the leaf didn't produce sugar because it wasn't exposed to sunlight. Part of the leaf was exposed to the sun, thus this leaf produced sugar, while the yellow part of the leaf did not because it was not exposed to the sunlight.
The person will likely go into ketosis after long enough. Their body will burn fat and protein. It will cause bad breath due to the ketones being released via saliva as a result of ketosis.
