6.13-6.16 Flashcards
Why does fermentation occur?
Anaerobic; when oxygen is scare. Is able to keep muscle contractions for a short period of time.
How does fermentation begin?
Starts with glycolysis and uses its yield of two ATP (also has pyruvate and reduces NAD+ to NADH).
What is the issue with oxidizing NADH back to NAD+ for fermentation.
Because glycolysis requires NAD+, it must be recycled. However, it is only recycled through the ETC, which only occurs in aerobic environments. Therefore, fermentation must find a different way to oxidize NADH.
What is lactic acid fermentation and how does it work?
The NADH molecule is oxidized by donating its electrons to the two pyruvate molecules, making them lactate (ionized form of lactic acid). The lactate is carried by blood to the liver, where it is converted back to pyruvate and eventually finish cellular respiration.
When does fermentation happen?
when the demand for ATP outpaces the oxygen influx to cells in facultative anaerobes.
What is alcohol fermentation and how does it happen?
Occurs in yeasts. Again, NADH donates its “H” (electrons) to pyruvate, but it is broken down into CO2 and, hence the name, ethanol. The bubbles in beer, champagne and bread come from the CO2. Fun fact: the production of ethanol actually kills the yeast (@ 14% concentration), though they have ways of processing it out.
What is lactic acid fermentation used for?
Making yogurt, soy sauce, sauerkraut.
What are obligate anaerobes?
Prokaryotes that live in deep soil and stagnant ponds that must preserve themselves through anaerobic respiration. Oxygen poisons them.
What is a facultative anaerobe?
can make ATP by fermentation or by oxidative phosphorylation (depends O2). Human muscles cells are facultative anaerobes.
Why are wine and beer stored it vats.
To keep oxygen from getting to yeast, which is a facultative anaerobe.
A glucose-fed yeast cell is moved from an aerobic environment to an anaerobic one. For the cell to continue generating ATP at the same rate, how would its rate of glucose consumption change?
The cell would have to consume glucose at a rate about 16 times the consumption rate in the aerobic environment (2*16=32).
What metabolic process is found in all living organisms.
Glycolysis.
How old is glycolysis?
Ancient. The first forms of life on earth used it to make ATP. Bacterial fossils from 3.5 billion years ago resemble some types of bacteria today. Note that it occurs without any help from organelles, citing its antiquity.
How did O2 build up in the atmosphere?
By-product of bacterial photosynthesis. (2.7 billion years ago). Glycolysis, then, was the main ATP generator for a very long time.
List the characteristics that make glycolysis ancient metabolic pathway.
Occurs universally (in fermentation and respiration), does not require oxygen, and does not occur in a membrane-enclosed organelle.
6.15&6.17
