Cells use blank to get energy only when carbohydrates are not available

The correct answer would be lipids.

Explanation:

Glucose degradation release energy in the cell in the form of ATP. however, when carbohydrates are not available cells initiates degradation of lipids allows cells to get the necessary energy for their survival.

Degradation of lipids takes place in the mitochondria, according to a set of chemical reactions grouped under the beta-oxidation of fatty acids. Lipid degradation release energy twice of the carbohydrate degradation by almost 9 calories.

Thus, the correct answer would be lipids.

fertilization, pictured in figure 24.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. the egg and sperm each contain one set of chromosomes. to ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. in mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. when a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. in placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma membrane to fuse with the egg plasma membrane, as illustrated in figure 24.23b. the fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum. the nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.

explanation: