Which of the following is the primary nutrient used in metabolism?
1) sugar
2) lipids
3)proteins
4) genetic material

The answer is: 1) sugar.

Balanced chemical reaction of cellular respiration:  

C₆H₁₂O₆(glucose) + 6O₂ → 6CO₂ + 6H₂O + energy.  

This reaction represent cellular respiration where organic matter is transformed into carbon dioxide and energy is released.

Glucose (sugar) and oxygen are reactants and carbon dioxide, water and energy are products of this chemical reaction; cellular respiration creates an energy molecule when glucose is broken down.

Glycogen is the main storage form of glucose in the body.

Another sugar, sucrose or table sugar (C₁₂O₂₂O₁₁) composed of two monosaccharides. Monosaccharides glucose and fructose are linked with an ether bond between C1 on the glucosyl subunit and C2 on the fructosyl unit.

Main component of bread is flour and main component of flour is starch.

Starch is a polymeric carbohydrate consisting of a large number of glucose units bonded by glycosidic bond. Starch is a white, tasteless and odorless powder that is insoluble in cold water or alcohol.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.