The purine ring system is shown below. What is the source of the C-6 atom during de novo biosynthesis of purines? 
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Expression
Expression involves the process of making one's thoughts, feelings, or ideas known through speech, writing, or artistic forms.
Interactional Listening
The process of actively engaging with and understanding messages conveyed in an interaction, emphasizing both verbal and non-verbal communication.
Selective Perception
The process by which individuals perceive what they want in media messages while ignoring opposing viewpoints.
Filtering
The process of screening or removing unnecessary information or data to focus on relevant or important details.
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