Eukaryotic cell’s have a nucleus and prokaryotes don’t
        
             
        
        
        
Answer:
Choosing protein as macromolecule.
Explanation:
The given environmental changes can lead to structural changes in protein as well:
pH - Several amino acids contain sidechains with practical gatherings that can promptly pick up or lose a proton. Changes in pH would prompt an adjustment in the charge of the amino acids, prompting charge-charge attraction or repilsion between non-interfacing amino parts.  
Temperature - High temperatures can prompt protein denaturation. Warmth can upset hydrogen bonding and hydrophobic interactions.  
Reduction or oxidation Environment - Some tertiary structure of protein folding is held by disulfide linkages. Reducing agent will lead to unfolding by introducing itself to break disulfide bonds.
Effect of these change: Sequence of amino acid and structure of protein molecule form determines function, any slight change to a protein's structure may result in the protein to become dysfunctional or produce different product.
 
        
             
        
        
        
Elbow is the joint between upper and lower arm while wrist is the joint between lower arm and hands.
So below :P