Ch. 4: How Cells Obtain Energy: Cellular Respiration
Reading
BJU Biology: Ch. 4A - "Cellular Energy"
AP Princeton Review Ch. 6 - Cellular Energetics
Topics
In this unit we learn about metabolism and cellular respiration
Ethanol Biofuels lab
The best lab for illustrating cell energetics is the ethanol biofuels lab - "Biosynthesis and distillation of ethanol". In the fermentation step, we can study cell respiration, and in the distillation and combustion steps we learn an important lab technique and see thermodynamics in action. This has been a favorite lab for several years. Lab handouts and instructions are down below, near the bottom.
BJU Biology: Ch. 4A - "Cellular Energy"
AP Princeton Review Ch. 6 - Cellular Energetics
Topics
In this unit we learn about metabolism and cellular respiration
Ethanol Biofuels lab
The best lab for illustrating cell energetics is the ethanol biofuels lab - "Biosynthesis and distillation of ethanol". In the fermentation step, we can study cell respiration, and in the distillation and combustion steps we learn an important lab technique and see thermodynamics in action. This has been a favorite lab for several years. Lab handouts and instructions are down below, near the bottom.
| cellular_respiration_-_glycolysis_krebs_cycle___electron_transport_chain |
Below: Cells require energy to run, including powering their motor proteins (left). The ATP Synthase rotary turbine in the Mitochondria is responsible for charging up ATP 'batteries'.
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What are we learning here?
At this point in the course, we are beginning to see that every cell is like a complex factory - full of nanomachines, walking motor-proteins, and spinning turbo-generators - and that's what makes Biology and Biotechnology incredibly fascinating.
Cells require energy to do all this work (that's why you eat!). Animal cells get their energy and raw-materials by breaking down glucose (blood sugar) in a process called cellular respiration (covered in this Unit), while plant cells get their energy and raw materials from sunlight and atmospheric carbon dioxide (CO2) in a process called photosynthesis (covered in the next Unit).
At this point in the course, we are beginning to see that every cell is like a complex factory - full of nanomachines, walking motor-proteins, and spinning turbo-generators - and that's what makes Biology and Biotechnology incredibly fascinating.
Cells require energy to do all this work (that's why you eat!). Animal cells get their energy and raw-materials by breaking down glucose (blood sugar) in a process called cellular respiration (covered in this Unit), while plant cells get their energy and raw materials from sunlight and atmospheric carbon dioxide (CO2) in a process called photosynthesis (covered in the next Unit).
A simple explanation of cellular respiration:
- Your food is digested and broken down into glucose. Glucose is a 6-carbon sugar. A way to think of glucose is old-fashioned corn syrup.
- The glucose molecules are transported from your small intestine into your blood stream. It is now referred to as blood sugar.
- The glucose is transported from your bloodstream across your cell membranes (active transport) so the cells can use it as fuel. The insulin produced by your pancreas tells your cells to uptake the glucose. We learned this in our Diagnosing Diabetes lab.
- Once in the cell, the 6-carbon glucose molecules are broken down into 3-carbon molecules known as pyruvate and generate 2 ATP molecules for energy use. This step is called glycolysis. ATP = adenosine triphosphate.
- Then, in the mitochondria, the pyruvate molecules are broken all the way down to CO2, in the process generating 2 more ATPs ... plus a bunch of NADH and FADH2 energy molecules. The CO2 produced in this step is the CO2 you breathe out in your breath.
- In the final step, the NADH and FADH2 molecular trucks deliver their stored-up energy to high-speed molecular turbines called ATP Synthase, also in your mitochondria. ATP Synthase is a fascinating, proton-powered, molecular-sized, turbine generator - which is assembled from dozens of protein parts. The ATP Synthase spins rapidly and generates 34 additional ATPs - a lot of energy!
A good way to remember cellular respiration
Step 1: Glycolysis ("Gimme a Break")
Step 1: Glycolysis ("Gimme a Break")
- Glucose enters the cell's cytoplasm, where the 6-carbon molecule is broken down into two, 3-carbon molecules called pyruvate. This generates 2 ATP's for energy use.
- ATP is called the 'battery' or 'energy currency' of the cell. If one molecule of glucose represents a $10 bill, then a molecule of ATP represents 25 cents. The cell can't burn a molecule of glucose all at once - it's too big; that's why it needs a smaller unit such as ATP.
- The 3-carbon pyruvate molecules are then broken down all the way to CO2 molecules in the Krebs Cycle (also called Citric Acid Cycle).
- This occurs in the mitochondria, the "power plant" of the cell
- 2 more ATP's are made available, but more importantly the electron carriers NADH and FADH2 are loaded with electrons and ready to enter the 'electron transport chain'.
- The loaded electron trucks NADH and FADH2 then transfer their electron cargo to the Electron Transport Chain
- The energy from the electrons is used to run high-speed turbines called ATP-Synthase. The turbines are mounted in the inner membrane of the mitochondria. (refer to video clip)
- The turbines spin very fast (7,000 RPM) and are connected by a driveshaft to a generator which very quickly charges up new ATP 'batteries'
- In this manner, ADP (discharged batteries) are transformed to ATP (newly charged batteries). About 34 additional ATP's are produced in this step. This is highly productive!
Below: 'ATP Synthase' is a molecular rotary turbine which recharges ATP in your cells. It is literally a proton-powered turbine-generator. These amazing nanomachines are in the mitochondria within your cells, and within chloroplasts in plants.
Watch the videos below. They will give you a mental picture of what is going on.
Below: Cellular Respiration explained really well (4 min).... watch this one
Below: The Electron Transport Chain explained in some detail (7 min). I would highly recommend watching this...
Below: ATP Synthase rotary turbine in all its Glory (4 min). This is a detailed look at its structure.
Homework
Homework is posted in Canvas. Some of the necessary handouts are below.
Homework is posted in Canvas. Some of the necessary handouts are below.
| cellular_respiration_video_questions.docx |
| bugs_with_gears_assignment_.docx |
Ethanol Biofuels lab: "Biosynthesis and distillation of ethanol"
| 5._ethanol_biofuel_lab_lecture_notes_2023___.docx |
| 5._biofuels_video_project.docx |
| biofuels_lab_report_part_2_student_examples DO YOUR OWN WORK.pdf |
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In this lab, we will make ethanol using fermentation, concentrate it using distillation, and demonstrate its capability as a fuel by running a Sterling Engine. This project is an excellent platform for learning about 1) cellular respiration and 2) modern biotechnology.
Learning objectives:
- (optional if time allows) Break-down carbohydrates into sugars using amylase enzyme. This is called "conversion".
- (optional if time allows) Detect sugars and carbohydrates using the Benedicts Reagent test and the Iodine test.
- (to save time, we may start here) Fermentation of sucrose to ethanol
- Prove that fermentation produces CO2 as a waste byproduct. Bubble CO2 through lime water to create Calcium Carbonate precipitate, and observe the accompanying pH reduction.
- Concentrate the ethanol from 10% up to 90%+ using distillation
- Use the ethanol biofuel to run a Sterling Engine
Learning objectives:
- Fermentation is an anaerobic (without oxygen) process which converts glucose into energy for the cells.
- Yeast (and your muscle cells) can use fermentation to generate energy quickly in the absence of oxygen.
- Fermentation represents only the first stage of Respiration. Your body's cells will normally go further to Kreb's Cycle and to Oxidative Phosphorylation - yielding much more energy.
- Fermentation starts with Glucose (6-carbon molecule) and ends at Pyruvate (3-carbon molecule). Complete cellular respiration, by comparison, converts the Glucose (6-carbons) all the way to Carbon Dioxide and water.
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