4/18 Notes: Cellular Respiration and Fermentation

Chapter 9: Cellular Respiration & Fermentation Section 1: Cellular Respiration: An Overview

As we learned last chapter, energy from the sun is transformed into different forms. In this chapter you will learn how cellular respiration transforms the energy into a form that our cells are able to use. this chapter focuses on how cells use the energy stored in food molecules to make ATP

Chemical Energy for Animals Cellular Respiration: is the process by which cells make energy for life processes. Cells take the carbon present in glucose & turn it into stable carbon dioxide & energy In simple terms, it is the process where our bodies break down foods and the cells convert stored chemical energy from the food into ATP, which is the energy the cells use ATP is the portable form of energy used inside of cells

Cellular Respiration Cellular Respiration is basically the opposite of photosynthesis. The products of photosynthesis are the reactants of respiration. In other words, plants and animals work together! “biochemical pathway”

Adenosine Tri-Phosphate ATP: is the main source of energy for cells. ATP is made of a nitrogen base, a sugar, and 3 phosphates Energy holds the 3rd phosphate to the other 2. When the 3rd phosphate is released, ATP becomes Adenosine Di-Phosphate (ADP). The “energy connector” is also released, and energy is available for cell processes.

Chapter 9: Cellular Respiration & Fermentation Section 2: The Process of Cellular Respiration

Cellular Respiration (ATP Production) Glycolysis is the first step in respiration. It yields a small amount of ATP. It then leads to 1 of 2 paths depending on the presence or absence of oxygen: Anaerobic Fermentation occurs if oxygen is absent. It yields no additional ATP. Aerobic Respiration occurs if there is oxygen present. It yields more ATP. The amount of oxygen present determines how much ATP can be produced

Glycolysis Glycolysis is complicated here’s what happens: It takes place in the cytoplasm of the cell. 1 molecule of glucose (sugar) enters. 2 molecules of pyruvic acid are made. 2 molecules of NADH are made 2 (net) molecules of ATP are made. Glycolysis Summary: the process that breaks down glucose to pyruvate, producing a small amount of ATP http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_glycolysis_works.html

Chapter 9: Cellular Respiration & Fermentation Section 3: Fermentation

Anaerobic Respiration Fermentation occurs after glycolysis if there is no oxygen (in the absence of oxygen). No ATP is produced, but NAD+ is. NAD+ is used to keep glycolysis going. Other products are lactic acid or ethyl alcohol. Summary of Fermentation: Process that recycles NAD+ in the absence of oxygen so that carbohydrates can continue to be broken down to produce ATP. Occurs to enable glycolysis to continue

Lactic Acid Fermentation Pyruvic acid (from glycolysis) is converted to lactic acid. This process occurs in muscle cells when you exercise very hard. It occurs when there is not enough oxygen. The increased acidity in the cell cytosol reduces the ability of muscles to contract. This causes muscle fatigue, pain, & cramping.

Lactic Acid Fermentation Lactic acid fermentation is used in the manufacture of yogurt and cheese.

Alcoholic Fermentation Some plants and unicellular organisms use alcoholic fermentation rather than lactic acid fermentation. Ethyl alcohol fermentation is used in making beer and wine. It is also used by yeast in bread-making. The ethyl alcohol is burned off, and the CO2 bubbles make the bread rise.

Chapter 9: Cellular Respiration & Fermentation Section 2: The Process of Cellular Respiration

Aerobic Respiration Our cells usually have oxygen available. This allows for aerobic respiration. Nearly 20 times the ATP can be produced (over glycolysis)!!!

Aerobic Respiration Remember, we started with glycolysis which gave us 2 ATPs. Since we now have oxygen available, fermentation is skipped Remember the 2 Pyruvic acid molecules from glycolysis? The pyruvic acid enters the mitochondria (in eukaryotes) It is used to make 2 acetyl CoA, 2 NADH, & 2 CO2 Your muscles don’t hurt as bad, and you can keep going longer! (Of course, you’re working at a slower rate.)

Aerobic Respiration Aerobic Respiration has 2 major stages: Krebs Cycle NAD+ is changed to NADH. FAD+ is changed to FADH2 In prokaryotes, this occurs in the cytosol. In eukaryotes, this occurs in the mitochondria. Electron Transport Chain NADH and FADH2 is used to make ATP. 1 NADH makes 3 ATP 1 FADH2 makes 2 ATP

Krebs Cycle Pyruvic Acid (from glycolysis) is converted into Acetyl CoA to start the Krebs Cycle CO2, Hydrogen, and ATP are produced. Along with NADH and FADH2

Krebs Cycle 1 molecule of glucose makes 2 molecules of pyruvic acid, which makes 2 Acetyl CoA – Therefore, the Krebs cycle must turn twice. Only 2 ATPs are produced (the same as glycolysis). 6 NADH molecules and 2 FADH2 molecules are made. They drive the rest of aerobic respiration. Krebs Cycle Summary: a series of chemical reactions that break down Acetyl CoA, producing ATP & electron carriers that enter an ETC http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter25/animation__how_the_krebs_cycle_works__quiz_1_.html

Krebs Cycle

Electron Transport Chain The ETC is the final stage of aerobic respiration. Up to 34 (net) ATPs are produced (this is the stage of aerobic respiration that produces the most ATP) The NADH & FADH2 produced previously during glycolysis, the conversion of pyruvic acid, & the Krebs Cycle are converted into ATP during this process Remember: 1 NADH = 3 ATP 1 FADH2 = 2 ATP

Electron Transport Chain The electrons grab Hydrogen ions and throw them out of the mitochondrial matrix. The Hydrogen naturally wants to leak back in (by diffusion). This “leaking” helps turn ADP back into ATP. Oxygen is the final electron acceptor.

ETC

Amount of Energy Produced The efficiency of aerobic respiration is roughly 66%. That may not seem like much, but your car is only about 25% efficient!!!

Amount of Energy Produced Glycolysis is extremely inefficient!!! It is only about 3.5% efficient. It is enough to provide energy for some unicellular and very small multi-cellular organisms, though. Most of the energy is contained in pyruvic acid, not the 2 ATPs produced.

Summarizing Cellular Respiration Reactants: glucose and oxygen Products: carbon dioxide, water, and energy C6H12O6 + 6O2  6CO2 + 6H2O + energy (Glucose + Oxygen  Carbon Dioxide + Water + Energy)

Cellular Respiration cellular respiration - the process by which cells make ATP by breaking down glucose or other food molecules as you can see, the equations for photosynthesis and respiration have similar pieces photosynthesis produces glucose and cellular respiration uses it photosynthesis removes CO2 from the atmosphere and respiration puts it back photosynthesis releases O2 into the atmosphere, and cellular respiration uses it

2 ATP & 2 NADH Pyruvic acid Organic Compounds (Glucose) Glycolysis Oxygen Oxygen absent present Fermentation Aerobic Respiration The Krebs Cycle Electron Transport Chain ATP

What is the difference between cellular respiration & photosynthesis? They are backwards in chemical equation of each other Cellular respiration produces ATP as an end product while photosynthesis produces glucose(sugar) as an end product H2O CO2 O2 Glucose Energy (but different types) What do they have in common?

There are 3 main steps in glycolysis There are 3 main steps in glycolysis. What are the starting & ending products for each step? In the first step, glucose is the starting product and two three-carbon sugars are the end products. In the second step the three-carbon sugars are the starting products and NADH are the ending products. In the third step, the modified three-carbon sugar from the second step is converted to pyruvate; four molecules of ATP are produced.

What happens during the Krebs cycle as electrons pass down the electron transport chain? Where does this step take place? Energy is transferred into each molecule through which the electrons pass. The electrons are transported in the inner membranes of mitochondria.

How does the ETC during the Krebs cycle affect the hydrogen ion concentration in a mitochondria? Hydrogen ions are pumped out of the inner chamber of the mitochondria, setting up a concentration gradient for hydrogen ions across the membrane.

What is the role of ATP synthase in the Krebs cycle? Hydrogen ions diffuse through this enzyme, providing energy for ATP production.

How is water formed as a by-product of the Krebs cycle? Oxygen combines with hydrogen ions and spent electrons to form water. If oxygen is not present, the electron transport chain stops and the Krebs cycle also stops.

glycolysis produces a net of 2 ATP molecules Which is most efficient in producing ATP: glycolysis, fermentation, or the Krebs cycle? Why? The Krebs cycle(aerobic respiration) because it includes the electron transport chain, which produces up to 34 molecules of ATP, which are added to the 2 ATP molecules produced by the Krebs cycle glycolysis produces a net of 2 ATP molecules fermentation produces NO ATP molecules. The total amount of ATP produced through aerobic respiration is 38

Cellular Respiration

Glycolysis

Fermentation: w/o O2 after glycolysis

Production of Acetyl CoA: w/O2 after glycolysis

Krebs Cycle

ETC

Total ATP Production