Cellular Respiration This is the process by which animals process food to obtain the calories needed for energy to do the cellular processes necessary for life. Watch this: http://youtu.be/Gh2P5CmCC0M Or this: https://www.youtube.com/watch?v=-Gb2EzF_XqA

Photosynthesis vs Cellular Respiration There is an energy trail: producers (photosynthesizers) consumers (animals) decomposers (bacteria) A cow eating grass is an example of a consumer eating a producer Photosynthesis is carried out by plants inside of chloroplasts (organelle)

Plants vs Animals Cellular respiration is carried out in the mitochondria in animals and plants Plants carry out photosynthesis and therefore have chloroplasts and mitochondria Besides photosynthesis, they also must break down their products to make ATP for cellular processes

Food The ultimate source of energy in food is “the sun”

Cellular Respiration Includes pathways that require oxygen Glucose directly provides energy for cellular work through cellular respiration! Glucose is oxidized and O2 is reduced Glucose breakdown is therefore an oxidation-reduction reaction (redox) Breakdown of one glucose results in 36 to 38 ATP molecules THE GOAL IS TO MAKE ATP TO RUN THE PROCESSES OF OUR CELLS.

Cell Respiration Overview Glucose: Stores energy in the molecule Cell respiration: Breaks down the molecules Extracts the contained energy Transfers electrons (from glucose) To electron carriers (e.g., NADH, FADH) to make ATP Giving off waste products (CO2 & H2O) 1st stage: 2nd & 3rd stage: Cytoplasm Mitochondria

Overall Equation for Cellular Respiration C6H12O6 + 6O2 YIELDS 6CO2 + 6H20 + 36-38ATP’s

What Type of Process is Cellular Respiration? An Oxidation-Reduction Process or REDOX Reaction Oxidation of GLUCOSE --> CO2 + H2O (e- removed from C6H12O6) Reduction  O2  to  H2O (e- passed (added) to O2) Electrons are lost from one substance and added to another substance!

Other Cellular Respiration Facts Metabolic Pathway that breaks down carbohydrates Process is Exergonic as High-energy Glucose is broken into CO2 and H2O Process is also Catabolic because larger Glucose breaks into smaller molecules

What are the Stages of Cellular Respiration? 1. Glycolysis 2. The Krebs Cycle 3. The Electron Transport Chain (ETC) REMEMBER THESE STEPS!

What this process needs to do is to strip the electrons off of glucose and eventually use them in the electron transport chain to create a proton gradient which, when turned on, allows them to flow through an enzyme (protein) which attaches a high energy phosphate to ADP to form ATP. So steps 1 and 2 are just electron collecting processes. It does take some work.

Cellular Respiration Glycolysis Krebs cycle Electron transport

Where Does Cellular Respiration Take Place? It actually takes place in two parts of the cell: Glycolysis occurs in the Cytoplasm Krebs Cycle & ETC Take place in the Mitochondria

Review of Mitochondria Structure Smooth outer Membrane Folded inner membrane Folds called Cristae Space inside cristae called the Matrix Copyright Cmassengale

In A Nutshell…

Copyright Cmassengale Diagram of the Process Occurs across Cristae Occurs in Cytoplasm Occurs in Matrix Copyright Cmassengale

1st stage: 2nd stage: 3rd stage: Glycolysis Krebs cycle (or citric acid) Electron transport

Electrons are the stars! If we track the transfer of hydrogen from sugar to oxygen, we also follow the transfer of electrons. During cellular respiration, hydrogen and its bonding electrons change partners from sugar to oxygen, forming water as a product. Energy is also released.

Glycolysis, occurs in the cytoplasm Series of steps (but 2 phases) 1. Glucose 2 pyruvic acid molecules As bonds in glucose are broken Electrons (and H+ ions) NAD+ 2. NADH Glucose Is oxidized NAD+ Is reduced Net output is 2 ATP for each glucose molecule But, most of the released energy carried by NADH

Steps of Glycolysis 1. glucose (6 carbon sugar) is broken into two 3 carbon molecules which requires 2 ATP 2. The 3 carbon molecules donate high energy electrons to NAD+ forming NADH (reduction) 3. 4 ATP are produced. Net, 2 ATP The two 3 carbon molecules are pyruvate and still hold a lot of energy which will be harvested in step 2. the Kreb’s cycle (citric acid cycle)

With or Without Oxygen aerobic means with oxygen

Glucose 2 pyruvic acids Phase one 3 carbon 6 carbon 3 carbon

Glycolysis, phase 1 Some ATP is used to start the ‘breakdown’ of glucose Mitochondria Cytoplasm

Glycolysis, phase 2 High energy electrons are donated To NAD+ Forming NADH

Glycolysis, phase 2 And, phosphate groups are transferred ATP is made

Overall Review of Glycolysis Notice that two ATPs are used and Four are yielded, resulting in net 2 ATPs produced.

Glycolysis Diagram

Glycolysis Summary Also produces 2 NADH and 4 ATP Pyruvate is oxidized to Acetyl CoA and CO2 is removed

In-between glycolysis & Krebs Just before (or as) they enter the mitochondria 1. Pyruvic acid molecules are modified. It loses one carbon And CO2 is released The altered molecule is acetic acid (…vinegar!) Acetic acid is attached to a carrier molecule Called coenzyme A one NADH is produced And forms acetyl CoA To the mitochondrion

Prep for Citric Acid Cycle

Krebs cycle, in the mitochondria Series of reactions Continues to break down the sugar Present as acetic acid Captures more energy As NADH & FADH2 And more CO2 is released – the first electron acceptor of cellular respiration is NAD+ Net output is 2 ATP for each glucose molecule But again, most of the released energy carried by NADH

A Little Krebs Cycle History Discovered by Hans Krebs in 1937 He received the Nobel Prize in physiology or medicine in 1953 for his discovery Forced to leave Germany prior to WWII because he was Jewish

Krebs Cycle Summary Requires Oxygen (Aerobic) Cyclical series of oxidation reactions that give off CO2 and produce one ATP per cycle Turns twice per glucose molecule Produces two ATP Takes place in matrix of mitochondria

Krebs Cycle Summary Each turn of the Krebs Cycle also produces 3NADH, 1FADH2, and 2CO2 Therefore, For each Glucose molecule, the Krebs Cycle produces 6NADH, 2FADH2, 4CO2, and 2ATP

Krebs Cycle ATP NETS: 3NADH, 1ATP, 1FADH2, & 2CO2

What Carries the Electrons? NAD+ (nicotinadenine dinucleotide) acts as the energy carrier NAD+ is a coenzyme It’s Reduced to NADH when it picks up two electrons and one hydrogen ion

Are There Any Other Electron Carriers? YES! Another Coenzyme! FAD+ (Flavin adenine dinucleotide) Reduced to FADH2

Electron Transport, in the mitochondria Most of the ATP is produced in the ETC And, NADH & FADH donate their electrons to the ETC At the end of the chain of steps O2 exerts a strong pull on electrons And combines electrons & H+ ions to form H2O The ‘downhill’ flow of electrons powers an enzyme ATP synthase Which produces ~ 34 ATP

Electron Transport An array of molecules (…proteins) In the inner membrane of the mitochondrion

Electrons move from one member to the next The energy given up pumps H+ to inner space Matrix Oxygen captures electrons Hydrogens are added, water forms

The buildup of H+ ions give up energy When they diffuse through a special protein ATP synthase Matrix ATP synthase captures their energy To make ATP

ATP Synthase

ATP Synthase – actual protein

Electron Transport Chain Summary 34 ATP Produced H2O Produced Occurs Across Inner Mitochondrial membrane Uses coenzymes NAD+ and FAD+ to accept e- from glucose NADH = 3 ATP’s FADH2 = 2 ATP’s Oxygen is eventually reduced by the electrons to form water!

What would happen to the flow of electrons if oxygen were not present? The flow of electrons would continue but at a slower rate. The flow would cease and ATP production would stop. The presence of oxygen would have no effect.

Cyanide binds strongly with the last electron carrier in the chain. How would this affect the flow of electrons? The flow of electrons would continue but at a slower rate. The flow would cease and ATP production would stop. The presence of cyanide would have no effect.

Learning check Of the 3 stages of cell respiration, which produces the most ATP per glucose? In glycolysis, _______ is oxidized and _______ is reduced. The final electron acceptor of the electron transport chains in mitochondria is _______.

Learning check Cells can harvest the most chemical energy from which of the following? An NADH molecule A glucose molecule Six carbon dioxide molecules Two pyruvic acid molecules

Fermentation Occurs when O2 NOT present (anaerobic) Called Lactic Acid fermentation in muscle cells (makes muscles tired) Called Alcoholic fermentation in yeast (produces ethanol) Nets only 2 ATP

Learning check This figure represents an overview of the different processes of cellular respiration. Which of the following correctly identifies the different processes? 1. Glycolysis; 2. Electron transport chain; 3. Krebs cycle 1. Glycolysis; 2. Krebs cycle; 3. Electron transport chain 1. Krebs cycle; 2. Electron transport chain; 3. Glycolysis 1. Electron transport chain; 2. Glycolysis; 3. Krebs cycle