You are growing yeast cells in a culture. after a few days of consistent growth, you notice that cell growth has slowed considerably. after some testing you note gas bubbles in the culture fluid along with the presence of ethanol. what is the most likely cause of the decrease in cell growth?

The possible reason for the decrease in the cell growth would be the lack of glucose (food) in the culture.

Yeast is a eukaryotic unicellular organism capable of respiring aerobically as well as anaerobically.

In anaerobic respiration, one molecule of glucose produces a net gain of 2 ATP (glycolysis) only as compared to 36-38 ATP produced in aerobic respiration.

In addition, the pyruvate produced  during glycolysis is converted into ethanol and CO₂ in order to produce the lost NAD⁺.

Hence, by observation like production of ethanol and gas bubbles (caused by release of carbon dioxide) we can conclude that yeast were respiring anaerobically.

This increased the consumption rate of glucose or food by the yeast which resulted in the depletion of sugar in the culture.

Lastly, it caused considerable delay in the cell growth of the culture.

a fossil fuel is a fuel formed by natural processes, such as anaerobic decomposition of buried dead organisms, containing energy originating in ancient photosynthesis.[1] the age of the organisms and their resulting fossil fuels is typically millions of years, and sometimes exceeds 650 million years.[2] fossil fuels contain high percentages of carbon and include petroleum, coal, and natural gas.[3] other commonly used derivatives include kerosene and propane. fossil fuels range from volatile materials with low carbon to hydrogen ratios like methane, to liquids like petroleum, to nonvolatile materials composed of almost pure carbon, like anthracite coal. methane can be found in hydrocarbon fields either alone, associated with oil, or in the form of methane clathrates.

the theory that fossil fuels formed from the fossilized remains of dead plants by exposure to heat and pressure in the earth's crust over millions of years was first introduced by andreas libavius "in his 1597 alchemia [alchymia]" and later by mikhail lomonosov "as early as 1757 and certainly by 1763".[4] the first use of the term "fossil fuel" was by the german chemist caspar neumann, in english translation in 1759.[5]

in 2017 the world's primary energy sources consisted of petroleum (34%), coal (28%), natural gas (23%), amounting to an 85% share for fossil fuels in primary energy consumption in the world.[6] non-fossil sources in 2006 included nuclear (8.5%), hydroelectric (6.3%), and others (geothermal, solar, tidal, wind, wood, waste) amounting to 0.9%.[7] world energy consumption was growing at about 2.3% per year. in 2015 about 18% of worldwide consumption was from renewable sources.[8]

nucleic acid molecules are incredibly complex, containing the code that guarantees the four different nucleotide units comprise dna, the nucleic acid of interest to the genealogist. and one of four nitrogen-containing molecules called nucleotides