How do guard cells maintain homeostasis?

Explanation:  Guard cells in the plants prevent water loss from it in cases of soil dryness or high temperature by closing themselves. If this does not happen, water will keep leaving the plant by the process of transpiration in these harsh conditions and the plant will not have the important medium for the homeostasis process to continue.

Loss of function mutations in any of the glycolytic enzyme would be fatal for  the embryo and the embryo will not survive.

Explanation:

Glycolysis is the first stage of cellular respiration and is a central metabolic pathway for energy production. Glycolysis is also the basic pathway for several other metabolic pathways. Mutation in any of the glycolytic enzymes would not allow the survival of the embryo and the embryo will die in early stages only.

Glycolysis is responsible for the large flux of carbon and is the sole source of energy for several types of cells and tissues such as the brain, sperms, RBCs, etc. Lethal mutations that affect any of the central processes do not allow survival of the organisms.