BIOLOGY 111. CHAPTER 7: Vital Harvest: Deriving Energy From Food

BIOLOGY 111 CHAPTER 7: Vital Harvest: Deriving Energy From Food

Deriving Energy from Food: What is the best carbohydrate source (for energy) in our food? Glucose! Where is the energy stored in glucose? Chemical Bonds What particle is responsible for the formation of chemical bonds? Electrons!

Deriving Energy from Food: Why Do We Breathe? As we have seen, a flow of particles can provide a source of energy This is true with water, steam, ions and electrons We will see that a flow of high energy electrons is what is necessary to create energy (ATP) from food. The electrons start out in simple sugars (glucose) and end up being dumped on to very important Electron Acceptor Molecules.

Deriving Energy from Food: Why Do We Breathe? As we have seen, a flow of particles can provide a source of energy The electrons start out in simple sugars (glucose) and end up being dumped on to very important Electron Acceptor Molecules. The most important is O 2, and that is why we breathe! In our cells, electrons travel inside Hydrogen atoms. They cannot travel free (just as electrons) so this is the easiest way for them to move from molecule to molecule (in Hydrogen atoms)

Deriving Energy from Food: Tracking Electrons! We will be tracing the flow of electrons through the process of generating ATP from Glucose Molecules that ACCEPT electrons are said to be Reduced and the process is called reduction Molecules that LOSE electrons are said to be Oxidized and the process is called oxidation. As electrons flow between molecules in mitochondria, molecules will either be oxidized or reduced

Deriving Energy from Food: Tracking Electrons! When one molecule donates electrons to a target molecule, the target molecule is Reduced, and the donator is Oxidized. (there is a balance) Chemical reactions that involve Reduction and Oxidation are called Redox Reactions.

Deriving Energy from Food: Electrons need to be carried from one molecule to the other in Redox Reactions (Oxidation/Reduction Reactions) The most important electron carrying molecule is called NAD (Nicotinamide Adenine Dinucleotide) When NAD is empty, it is represented as NAD+ When NAD is full (carrying electrons) it is represented as NADH

Deriving Energy from Food: Electrons need to be carried from one molecule to the other in Redox Reactions Electrons don t travel outside of atoms, so electrons travel in Hydrogen atoms (H). Just a proton and an electron

Vital Harvest: Deriving Energy from Food 7.1 Energizing ATP 7.2 The Three Stages of Cellular Respiration 7.3 First Stage of Respiration: Glycolysis 7.4 Second Stage of Respiration: The Krebs Cycle 7.5 Third Stage of Respiration: The Electron Transport Chain 7.6 Other Foods, Other Respiratory Pathways

Deriving Energy from Food: Why Do We Breathe? We need oxygen to maintain a flow of electrons! Electrons are stripped out of glucose and transported to oxygen

Deriving Energy from Food: Why Do We Breathe? Electron Acceptors are molecules that readily accept electrons. The most important of all electron acceptors to plants and animals is OXYGEN. This is why we breathe. We need to have oxygen available to complete the cycle of generating ATP from the food we eat. Oxygen keeps the flow of electrons going in our cells!

What is required to recharge ADP to the higher energy form ATP? ENERGY! The 1 st Law of Thermodynamics requires that for a low energy ADP to become a high energy ATP, energy must be added!

Energizing ATP: We need energy (and oxygen) to make ATP from ADP The energy comes from electrons in glucose, and the oxygen comes from photosynthesis

Vital Harvest: The Three Stages of Cellular Respiration GLYCOLYSIS KREB S CYCLE ELECTRON TRANSPORT CHAIN

Vital Harvest: The Three Stages of Cellular Respiration GLYCOLYSIS = 2 ATP KREB S CYCLE = 2 ATP ELECTRON TRANSPORT = 32 ATP What would happen if there wasn t any oxygen at the end?

Vital Harvest: The First Stage of Respiration: Glycolysis Glycolysis = The breaking apart of glucose (glycol lysis) Glucose cant get inside the mitochondria, so glycolysis breaks glucose into Pyruvic Acid Pyruvic Acid can get inside mitochondria! Most of the high energy electrons from glucose are now in the 2 Pyruvic Acid

Vital Harvest: The First Stage of Respiration: Glycolysis Glycolysis accomplishes 3 important things: Generates 2 ATP molecules Produces 2 energized molecules of NADH (carrying electrons) Breaks glucose (C6) into 2 molecules of Pyruvic Acid (C3).

Vital Harvest: The First Stage of Respiration: Glycolysis Where does Glycolysis Occur? In Cytosol (not in Mitochondria) The other 2 Steps of Cellular Respiration occur in Mitochondria

Vital Harvest: The First Stage of Respiration: Glycolysis Glycolysis accomplishes 3 important things: Actually Glycolysis produces 4 ATP, but it uses up 2 ATP in the process Final Yield 2 ATP 2 NADH 2 Pyruvic Acid (C3)

Vital Harvest: The Second Stage of Respiration: Krebs Cycle Krebs Cycle Starts with 2 Pyruvic Acids This stage occurs in the Mitochondria

Vital Harvest: The Second Stage of Respiration: Krebs Cycle Starts with 2 Pyruvic Acids Makes 2 ATP Produces lots of NADH! (don t worry about FADH 2 ) o o NADH carries high energy electrons and is needed for the production of ATP! High energy electrons went from glucose, to NADH, and now are in NADH

Vital Harvest: The Second Stage of Respiration: Krebs Cycle When glucose is destroyed (to get its electrons) its carbon atoms are removed as CO 2 Final Results of Krebs Cycle: Lots of NADH 2 ATP 6 CO 2

Vital Harvest: The Third Sage of Respiration: The Electron Transport Chain Quick Review: The electrons derived from food are transferred to the later stages of energy harvesting by molecules known as, the most important of which is one called in its "empty" form and in its "loaded or reduced form.

Vital Harvest: The Third Sage of Respiration: The Electron Transport Chain Quick Review: The electrons derived from food are transferred to the later stages of energy harvesting by molecules known as Electron Acceptors, the most important of which is one called in its "empty" form and in its "loaded or reduced form.

Vital Harvest: The Third Sage of Respiration: The Electron Transport Chain Quick Review: The electrons derived from food are transferred to the later stages of energy harvesting by molecules known as Electron Acceptors, the most important of which is one called NAD+ in its "empty" form and in its "loaded or reduced form.

Vital Harvest: The Third Sage of Respiration: The Electron Transport Chain Quick Review: The electrons derived from food are transferred to the later stages of energy harvesting by molecules known as Electron Acceptors, the most important of which is one called NAD+ in its "empty" form and NADH in its "loaded or reduced form.

Vital Harvest: The Three Stages of Cellular Respiration GLYCOLYSIS = 2 ATP KREB S CYCLE = 2 ATP ELECTRON TRANSPORT = 32 ATP! This is where most of the ATP is generated in cellular respiration This is accomplished through 2 energy transformations

Vital Harvest: The Third Sage of Respiration: The Electron Transport Chain What does the Electron Transport Chain accomplish? This is where the energy transformations take place! 1. The energy from electrons in NADH is transformed into the energy of a diffusion gradient 2. Then the energy from the diffusion gradient is transformed into ATP!

Vital Harvest: The Third Sage of Respiration: The Electron Transport Chain What does the Electron Transport Chain accomplish? This is where the energy transformations take place! The enzyme, ATP Synthase is responsible for the production of ATP. It uses high energy electrons to make ATP

Vital Harvest: The Third Sage of Respiration: The Electron Transport Chain What does the Electron Transport Chain accomplish? This is where the energy transformations take place! ENERGY TRANSFORMATIONS IN CELLULAR RESPIRATION e - in Glucose e - in NADH Diffusion Gradient ATP Work

Electron Transport Chain The flow of electrons pushes H+ ions to the outer compartment of Mitochondria This creates a huge concentration gradient! Videos: Proton Gradient

Vital Harvest: The Third Sage of Respiration: The Electron Transport Chain What does the Electron Transport Chain accomplish? Creates a Proton Gradient that powers the enzyme ATP Synthase (enzyme that makes ATP) Protons (H+) are Hydrogen atoms (H) that have lost their electrons

Electron Transport Chain NADH provides enough electrons to produce 32 ATP from each glucose molecule! Glycolysis = 2 ATP Krebs Cycle = 2 ATP Glucose 36 ATP

Vital Harvest: The Three Stages of Cellular Respiration GLYCOLYSIS = 2 ATP KREB S CYCLE = 2 ATP ELECTRON TRANSPORT = 32 ATP All this ATP (except glycolysis) is only produced if there is a flow of electrons from Glucose to Oxygen!

Deriving Energy from Food: Why Do We Breathe? We breathe to maintain a flow of electrons inside mitochondria. If we can do this, we can produce lots of ATP. Electrons start in Glucose and are carried away in H 2 O after they are finally dumped onto Oxygen. So without Oxygen, there is no flow and the electrons pile up as NADH and everything stops (except glycolysis)

Deriving Energy from Food: Can you trace the path of ELECTRONS through Cellular Respiration? Can you trace the path of ENERGY through Cellular Respiration? They are the same path until we reach energy transformations in the ETC