Unit 5: Cellular Respiration
How a cell burns the sugar built by photosynthesis to generate the ATP it actually runs on.
6 topics · 19 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
Why Cells Break Down Glucose
- How it worksHow does cellular respiration release glucose's energy in small controlled steps instead of all at once?
- Common mistakeWhy doesn't cellular respiration happen only in animal cells and not in plant cells too?
- Ties togetherHow does the glucose a plant builds by photosynthesis end up powering your own cells after you eat it?
Your turn1 of 2
Burning wood in a fire releases all its stored chemical energy at once, as heat and light. Why can't your cells release glucose's energy the same explosive way?Glycolysis
- How it worksWalk me through how glycolysis splits one glucose molecule into two molecules of pyruvate.
- Worked exampleFind the net number of ATP molecules produced directly by glycolysis from one glucose molecule.
- Common mistakeWhy doesn't glycolysis require any oxygen to run?
Your turn1 of 2
Glycolysis splits one glucose molecule and yields a net gain of 2 ATP molecules per glucose processed. If a muscle cell runs glycolysis on 2801 molecules of glucose, how many net ATP does glycolysis alone produce?The Krebs Cycle
- How it worksHow does the Krebs cycle strip electrons off carbon compounds and load them onto NADH and FADH2?
- Going furtherWhat happens to the Krebs cycle the moment a cell runs out of oxygen?
- Common mistakeWhy doesn't the Krebs cycle directly use oxygen even though it can't run without oxygen downstream?
Your turn1 of 2
Glycolysis alone yields only 2 net ATP per glucose, yet the cell doesn't stop there. Why does pyruvate get broken down further through the Krebs cycle instead of the process ending right after glycolysis?The Electron Transport Chain and ATP Synthase
- How it worksHow does the electron transport chain use electrons from NADH to pump protons across a membrane?
- How it worksWalk me through how ATP synthase spins protons flowing back across the membrane into ATP.
- Worked exampleFind the approximate total ATP yield from one glucose molecule across glycolysis, the Krebs cycle, and the electron transport chain.
- Common mistakeWhy isn't oxygen used to make ATP directly instead of just accepting electrons at the end of the chain?
Your turn1 of 2
Cellular respiration yields approximately 30 ATP molecules per glucose molecule once glycolysis, the Krebs cycle, and the electron transport chain are all combined. If a liver cell fully oxidizes 2095 glucose molecules, approximately how many total ATP does it produce?Fermentation
- How it worksHow does lactic acid fermentation regenerate the NAD+ that glycolysis needs to keep running?
- Common mistakeWhy doesn't fermentation produce anywhere near as much ATP as full cellular respiration does?
- Ties togetherHow does yeast fermentation producing carbon dioxide explain why bread dough rises?
Your turn1 of 2
Full aerobic respiration yields about 31 ATP per glucose molecule, while fermentation nets only 2 ATP per glucose molecule. How many times more ATP does full respiration produce per glucose than fermentation does?Comparing Photosynthesis and Cellular Respiration
- How it worksHow does carbon cycle between the atmosphere, a plant's chloroplasts, and its mitochondria?
- Common mistakeWhy doesn't a plant stop doing cellular respiration just because it's also doing photosynthesis in daylight?
- Ties togetherHow do the inputs and outputs of photosynthesis and cellular respiration mirror each other in reverse?
Your turn1 of 2
Daylight brings enough sunlight for a plant to run photosynthesis at full speed. Why doesn't the plant simply stop cellular respiration during the day since it's already making its own glucose?