gut fermentation

Behind every fart is an army of gut bacteria undergoing some crazy biochemistry. These bacteria break down the remains of digested food through fermentation, creating gas in the process. Learn what these bacteria have in common with beer brewing at http://youtu.be/R1kxajH629A?list=PLzMhsCgGKd1hoofiKuifwy6qRXZs7NG6a . Click image to the left or use the URL below. URL:


Sometimes cells need to obtain energy from sugar, but there is no oxygen present to complete cellular respiration. In this situation, cellular respiration can be anaerobic, occurring in the absence of oxygen. In this process, called fermentation, only the first step of respiration, glycolysis, occurs, producing two ATP; no additional ATP is produced. Therefore, the organism only obtains the two ATP molecules per glucose molecule from glycolysis. Compared to the 36-38 ATP produced under aerobic conditions, anaerobic respiration is not a very efficient process. Fermentation allows the first step of cellular respiration to continue and produce some ATP, even without oxygen. Yeast (single-celled eukaryotic organisms) perform alcoholic fermentation in the absence of oxygen. The products of alcoholic fermentation are ethyl alcohol (drinking alcohol) and carbon dioxide gas. This process is used to make common food and drinks. For example, alcoholic fermentation is used to bake bread. The carbon dioxide bubbles allow the bread to rise and become fluffy. Meanwhile, the alcohol evaporates. In wine making, the sugars of grapes are fermented to produce wine. The sugars are the starting materials for glycolysis. Animals and some bacteria and fungi carry out lactic acid fermentation. Lactic acid is a waste product of this process. Our muscles perform lactic acid fermentation during strenuous exercise, since oxygen cannot be delivered to the muscles quickly enough. The buildup of lactic acid is believed to make your muscles sore after exercise. Bacteria that produce lactic acid are used to make cheese and yogurt. The lactic acid causes the proteins in milk to thicken. Lactic acid also causes tooth decay, because bacteria use the sugars in your mouth for energy. Pictured below are some products of fermentation ( Figure 1.1). Products of fermentation include cheese (lactic acid fermentation) and wine (alco- holic fermentation).


instructional diagrams

No diagram descriptions associated with this lesson


anaerobic respiration is less effective than aerobic respiration.

-->  a. true

b. false

in the absence of oxygen, yeast make alcohol.

-->  a. true

b. false

how many times more effective is aerobic respiration compared to anaerobic respiration?

a) 2x

b) 9x

-->  c) 18x

d) 36x

what is the main goal of fermentation?

a) to produce two atp

-->  b) to allow glycolysis to occur

c) to make alcohol

d) to produce lactic acid

what organisms perform lactic acid fermentation under anaerobic conditions?

a) plants

b) animals

c) fungi

-->  d) both (b) and (c)

lactic acid fermentation is used to make which of the following products?

a) drinking alcohol

b) bread

-->  c) yogurt

d) all of the above

what process allows bread to rise?

a) aerobic respiration

b) lactic acid fermentation

-->  c) alcoholic fermentation

d) photosynthesis

diagram questions

No diagram questions associated with this lesson