Yeast is a fungus and needs a supply of energy for its living and growth. Sugar supplies this energy. (Your body also gets much of its energy from sugar and other carbohydrates.). Yeast can use oxygen to release the energy from sugar (like you can) in the process called respiration. So, the more sugar there is, the more active the yeast will be and the faster its growth (up to a certain point-even yeast cannot grow in very strong sugar-such as honey).
Molecules are held together by either covalent bonding or ionic bonding. Several types of non-metal elements exist only as molecules in the environment. For example, hydrogen only exists as hydrogen molecule. A molecule of a compound is made out of two or more elements.
The forces that hold MOLECULES together are ionic bonds in which one atom gives up electrons to another in order to complete their respective outer shells, covalent bonds in which the two or sometimes three atoms share electrons to satisfy their outer shells, and Van Der Waals forces which are kind of tricky to explain but in short kind of act like ...