What is the color change that indicates a positive citrate test?

The following structure represents an L enantiomer. 

A heat engine having the maximum possible efficiency has an efficiency of 25% when operating between two heat reservoirs. If the temperature of the cold reservoir is 300 K, what is the temperature of the hot reservoir?

Essential amino acids are acquired from dietary sources.

What are these structures colored in YELLOW called?

What blood vessels are outlined in GREEN?

What is this bumpy structure colored in PINK called?

What are these blue blood vessels outlined in GREEN called?

What chamber of the heart is colored in YELLOW?

What is this blood vessel that the RED arrow is pointing to called?