Some friends are trying to make wine in their basement. they've added yeast to a sweet grape juice mixture and have allowed the yeast to grow. after several days, they find that sugar levels in the grape juice have dropped, but there's no alcohol in the mixture. the most likely explanation is that
a. the mixture needs more sugar; yeast need a lot of energy before they can begin to produce alcohol the mixture needs less oxygen;
b. yeast only produce alcohol in the absence of oxygen the mixture needs more oxygen;
c. yeast need oxygen to break down sugar to produce alcohol the mixture needs less sugar;
d. high sugar concentrations stimulate cellular respiration, and alcohol is not a by-product of cellular respiration.

The correct answer is d. high sugar concentrations stimulate cellular respiration, and alcohol is not a by-product of cellular respiration.

Explanation:

As they added sweet grape juice mixture the amount of sugar increased in the content and it is seen that more than 6 % of sugar decreases the rate of fermentation and alcohol concentration also decreases and a moderate amount of glucose concentration in the anaerobic environment increases the fermentation results in more alcohol production.

High sugar concentration decreases fermentation but increases cellular respiration in the yeast, as a result, it uses more sugar for its growth and produce CO₂ and H₂O so alcohol is not the by-product of cellular respiration. Therefore the correct answer is d. high sugar concentrations stimulate cellular respiration, and alcohol is not a by-product of cellular respiration.

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:

one characteristic that is shared by all is a soft body. many

of these invertebrate animals also have an outer shell to protect their

body. oysters, clams, snails, and mussels are all mollusks. so are octopuses, squids, and slugs. mollusks live on land and in freshwater.