Saturated fats have long straight tails of fatty acids and can pack or clump tightly together in cells and animal bodies. Unsaturated fats have kinks in their tails due to double bonds, which prevents them from packing together as tightly. Animals that are ectothermic (their body temperature fluctuates with the environment) need to keep their membranes fluid at cooler temperatures and thus use in their membranes. Think about needing fats to be liquid.

mostly unsaturated fats

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: