Exam 2: Microbial Metabolism- Fermentation & Other forms of Catabolism Flashcards
Can the electron transport pathway function in the absence of terminal electron acceptors? Explain.
No, it cannot function. oxidative phosphorylation cannot occur.
Is the Krebs cycle useful in the absence of terminal electron acceptors? Explain.
No, because there’s not electron transport pathway to convert NADH and FADH into the more usable ATP.
In the absence of terminal electron acceptors, what is the only ATP-generating catabolic process?
Glycolysis is the only process yielding ATP. Oxidative phosphorylation and krebs cycle no longer occur. NADH no longer valuable as it cannot be transformed into ATP.
During fermentation, what is the purpose of the chemical reactions that modify pyruvate into another molecule such as lactic acid or ethanol?
To convert NADH to NAD+, those other products are the receptacle of the electrons, they are the trash cans.
What are the products of fermentation in a human skeletal muscle cell?
Lactic acid
Do you think all human cells can perform fermentation? Explain.
No, just the cells who find themselves in environments where oxygen might be lacking and or not in higher enough concentration to keep up with the cells energy needs.
What are the products of fermentation in the yeast Saccharomyces cerevisiae?
Ethanol and CO2
Why do you think different organisms produce different end products through fermentation? Shouldn’t life be standardized and simple? Explain.
Evolution, different products depending on the organism to reach the same goal.
How much ATP is produced from a single glucose molecule during fermentation?
2 ATP
List at least six products useful to humans that can be produced by microorganisms through fermentation.
- wine and beer thanks to yeast producing alcohol
- lactic acid producing bacteria
ferments milk to make cheeses and yogurt. - Swiss cheese has a specific lactic acid that causes its distinct flavor.
- Hydrogen gas producing microorganisms can be used as renewable energy sources.
- Rubbing alcohol and acetone produced by some microorganisms
Main focus of fermentation.
Fermentation focuses on replenishing NAD+ more than producing ATP. During aerobic cellular respiration NADH delivers electrons gain to the electron transport chain to be oxidized to NAD+. But no chain in fermentation so NAD+ needs to be regenerated for future glycolysis. Essential fermentation keeps feeding glycolysis in a loop. Pyruvate is converted into an electron acceptor that can take on the H form NADH converting it to NAD+. Or pyruvate can accept electrons itself.
Compare the energy yields of aerobic respiration, anaerobic respiration, and fermentation.
Aerobic 36 eukaryotes and 38 prokaryotes ATP, anaerobic 2-36 ATP, and fermentation 2 ATP
Might it be of benefit for an organism to have the ability to undergo all three of these energy-yielding processes? Explain.
To have the greatest yield of ATP possible when oxygen is and is not available.
Catabolism of Proteins
Metabolized as a last resort only when carbon sources such as glucose and fats are unavailable. Normally broken down into amino acids and absorb amino acids to produce our own proteins.
Prokaryotes secrete protease to digest proteins into amino acids. Occurs outside the cell as proteins are generally too large to cross cytoplasmic membranes unless hydrolyzed first. Amino acids then are transported into the cell. Amino groups are removed via deamination. Resulting molecules are converted into precursor metabolites that are metabolized further into the krebs cycle.
Many microbes normally catalyze proteins, food spoilage, pathogenic bacteria, fungi. Important source of energy and metabolism.
Catabolism of Starch
extracellular enzymes break down starch to simple sugar and transport them into the cell. They are either glucose or similar to glucose that can be converted to glucose or fructose. Then proceed along the normal pathway.
