Where do animal cells get their energy? Cellular Respiration Where do animal cells get their energy?

Remember Energy used by all Cells. Organic molecule containing high-energy Phosphate bonds

How Do We Get Energy From ATP? By breaking the high- energy bonds between the last two phosphates in ATP

Cellular Respiration The process of cell catabolism in which cells turn food into usable energy in the form of ATP. In this process glucose is broken down in the presence of molecular oxygen into six molecules of carbon dioxide, and much of the energy released is preserved by turning ADP and free phosphate into ATP. Cellular respiration occurs as a series of chemical reactions catalyzed by enzymes, the first of which is glycolysis, a series of anaerobic reactions in which glucose (a 6-carbon molecule) is split into two molecules of lactate (a 3-carbon molecule), producing a net gain of two ATP molecules. In a series of aerobic reactions, lactate is converted to pyruvate, which enters the mitochondrion and combines with oxygen to form an acetyl group, releasing carbon dioxide. The acetyl group (CH 3 CO) is then combined with coenzyme A as acetyl coenzyme A, and enters the Krebs cycle. During this series of reactions, each acetyl group is oxidized to form two molecules of carbon dioxide, and the energy released is transferred to four electron carrier molecules. The electron carrier molecules then release their energy in a process that results in the pumping of protons (hydrogen ions) out across the inner membrane of the mitochondrion. The potential energy of the protons generated by one acetyl group is later released when they recross the membrane and are used to form three molecules of ATP from ADP and phosphate in the process of oxidative phosphorylation. The pyruvate from one molecule of glucose drives two turns of the Krebs cycle. Thus, during cellular respiration one molecule of glucose, as well as oxygen, ADP, and free phosphate are catabolized to yield six molecules of carbon dioxide and an increase in usable energy in the form of eight molecules of ATP.

Glycolysis: the breakdown of glucose by enzymes, releasing energy and pyruvic acid. Pyruvic Acid: organic acid that occurs as an intermediate in many metabolic processes, especially glycolysis Anaerobic Respiration: A form of cellular respiration that occurs when oxygen is absent or scarce. The process of generating energy by the oxidation of nutrients and using an external electron acceptor other than oxygen. Fermentation: enzymatically controlled anaerobic breakdown of an energy-rich compound Aerobic Respiration: A form of cellular respiration that requires oxygen in order to generate energy. The process of generating energy by the full oxidation of nutrients through Krebs cycle where oxygen is the final electron acceptor.

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

Explain: Where do our cells get energy? 6-C sugars are the MAJOR source of energy for cell What type of macromolecule are 6-C sugars? Carbohydrates Cells break down glucose a 6-C sugar to make ATP “energy”

6 Carbon Sugars: They even count the sugars for you…

Cellular Respiration (3-stages) Glycolysis Krebs Cycle (Citric Acid Cycle) Electron Transport Chain (ETC) Glucose Glycolysis Krebs Cycle Electron Transport Fermentation (without oxygen) Alcohol or lactic acid Glucose Krebs cycle Electron transport Glycolysis Fermentation (without oxygen) Alcohol or lactic acid

Overall Chemical Process C6H12O6 + 6O2  6CO2 + 6H2O + usable energy Sugar + Oxygen  Carbon dioxide + Water + ATP

Flowchart of Cellular Respiration  Carbon Dioxide (CO2) + Water (H2O) ATP Glucose (C6H1206) + Oxygen (02) Glycolysis Krebs Cycle Electron Transport Chain

Glycolysis Where Cytoplasm NO O2 required Energy Yield net gain of 2 ATP at the expense of 2 ATP 6-C glucose  TWO 3-C pyruvates Free e- and H+ combine with organic ion carriers called NAD+  NADH + H+ (nicotinamide dinucleotide)

To the electron transport chain Glycolysis: Glucose 2 Pyruvic acid To the electron transport chain

To the electron transport chain  Glycolysis step 1 Glucose 2 Pyruvic acid To the electron transport chain

To the electron transport chain Glycolysis Step 2 Glucose 2 Pyruvic acid To the electron transport chain

C.R. Reactions Glycolysis Series of reactions which break the 6- carbon glucose molecule down into two 3- carbon molecules called pyruvate Process is an ancient one-all organisms from simple bacteria to humans perform it the same way Yields 2 ATP molecules for every one glucose molecule broken down Yields 2 NADH per glucose molecule

Summary In Out Glucose (6-C) 2 pyruvate; 2(3- C) 2 ATP 2NADH a net of 2 ATP

Questions Where does glycolysis take place? ____________________________________________ It needs _______ ATP to work. It provides _______ ATP a net gain of _______. Breaks glucose into TWO ___________. It is an Aerobic or Anaerobic process?

After Glycolysis After glycolysis, about 90 percent of the energy in glucose is still unused. Oxygen is required to extract the rest of the energy (aerobic process).

Still Need a review? Click on the picture.

Aerobic Cellular Respiration Oxygen required=aerobic 2 more sets of reactions which occur in a specialized structure within the cell called the mitochondria 1. Kreb’s Cycle 2. Electron Transport Chain

Krebs Cycle aka Citric Acid Cycle

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

 The Krebs Cycle Citric Acid Production Mitochondrion

Kreb’s Cycle Completes the breakdown of glucose Takes the pyruvate (3-carbons) and breaks it down, the carbon and oxygen atoms end up in CO2 and H2O Hydrogens and electrons are stripped and loaded onto NAD+ and FAD to produce NADH and FADH2 Production of only 2 more ATP but loads up the coenzymes with H+ and electrons which move to the 3rd stage

Krebs Cycle 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

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

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

First Step: Krebs Cycle/Citric Acid Cycle Breakdown of Pyruvic Acid Where mitochondria matrix Pyruvate (3-C)  Acetic acid (2-C) 3rd C forms CO2 Acetic acid combines with Coenzyme A to form ACETYL-CoA

What is releasing Energy with O2? Summary In Pyruvate NAD CoA Out CO2 (as waste) NADH Acetyl-CoA What is releasing Energy with O2? Aerobic respiration Where In the cells mitochondria

Second Step: Krebs Cycle or Citric Acid Cycle Where Mitochondrial matrix Energy Yield 2 ATP and more e- Acetyl-CoA (2-C) combines with 4-C to form 6-C CITRIC ACID Citric Acid (6-C) changed to 5-C then to a 4-C Gives off a CO2 molecule NAD+ and FAD pick up the released e- FAD becomes FADH2 NAD+ becomes NADH + H+ Cycle ALWAYS reforming a 4-C molecule

Krebs Cycle

Still Need a review? Click on the picture. Citric Acid Production Mitochondrion

Electron Transport Chain Aka ETC

Electron Transport Chain Electron carriers loaded with electrons and protons from the Kreb’s cycle move to this chain-like a series of steps (staircase). As electrons drop down stairs, energy released to form a total of 34 ATP Oxygen waits at bottom of staircase, picks up electrons and protons and in doing so becomes water

ETC Where inner membrane of mitochondria Energy Yield Total of 34 ATP O2 combines with 2 H+ to form H2O Exhale (waste product) - CO2, H2O comes from cellular respiration

Electron Transport Chain Mitochondrion Hydrogen Ion Movement Channel Intermembrane Space ATP synthase Inner Membrane Matrix ATP Production

Other ETC videos http://www.science.smith.edu/departments/Biology/Bio231/etc.html

So where did all the ATP come from again…

Total ENERGY Yield Glycolysis 2 ATP Krebs Cycle 2 ATP ETC  34 ATP Total 38 ATP

What happens if no O2? Cellular respiration process STOPS… but life needs to go on …

Anaerobic respiration

Fermentation Anaerobic respiration (requires no oxygen) Only 2 ATP are made in anaerobic respiration so it is not as good as aerobic respiration (34 ATP) Both begin with glycolysis (remember this process was anaerobic.) No Krebs (citric acid) cycle or electron transport chain

Two Types of Fermentation Alcoholic Fermentation Used by yeasts and a few other micro-organisms with ethyl alcohol and carbon dioxide as waste products. Causes bread to rise.

Lactic Acid Fermentation Lactic acid is produced from pyruvic acid. Produced in muscles during rapid exercise when enough oxygen is not present. Unicellular organisms also produce lactic acid as a waste product. Prokaryotes are used in the production of cheese, yogurt, buttermilk, sour cream, pickles, sauerkraut, and kimchi.

Anaerobic Respiration Only 2 ATP are made in anaerobic respiration so it is not as good as aerobic respiration (38 ATP). Glycolysis Glucose Pyruvate + 2 ATP Followed by one of these 2 processes. Alcoholic Fermentation Pyruvate ethyl alcohol + CO2 Lactic Acid Fermentation Pyruvate Lactic Acid Carried out by yeast & some bacteria. -Used in brewing beer & making cakes. Carried out by your muscle cells when you are exercising hard (need ATP) -Causes muscle cramps & soreness.

Aerobic vs. Anaerobic ATP Aerobic DOES requires oxygen It… Anaerobic DOES NOT require oxygen. It is … Simple fast produces smaller amounts of energy Aerobic DOES requires oxygen It… Yields large amounts of energy But is not simple, fast or efficient What is the energy molecule that is created? ATP

Releasing Energy with out Oxygen Anaerobic Respiration NO Additional ATP is Formed No Oxygen leads to Fermentation Two Types Lactic Acid Fermentation Alcoholic Fermentation

What are the 2 chemical equations? Alcoholic fermentation pyruvic acid + NADH → alcohol + CO₂ + NAD⁺ Lactic acid fermentation pyruvic acid + NADH → lactic acid + NAD⁺ What are the differences?

Review Time…

Energizes 2 electron carriers.(NAD+ NADH) Step 1 Glycolysis occurs in the cytoplasm. Glucose is broken in half to form two pyruvate molecules. A small amount of energy (ATP) is also produced. ATP Glycolysis Glucose Pyruvate Pyruvate ATP Energizes 2 electron carriers.(NAD+ NADH)

Step 2: Kreb’s Cycle (Citric Acid Cycle) occurs inside the mitochondria. ATP ATP Kreb’s Cycle Citric Acid Pyruvic Acid e- e- NADH e- CO2

Kreb’s Cycle/ Citric Acid Cycle cont… 3 Products from Kreb’s Cycle… 1. Carbon Dioxide released (like in your breath). 2. ATP provides energy for cellular activities. 3. High-energy electron (carried by electron carriers) that can be used to generate large amounts of ATP.

Step 3: Electron transport chain occurs in the mitochondria. Electrons move down the electron transport chain. Electrons are caught by oxygen to make water. 34 ATP are also made. NADH e- e- 34ATP e- Oxygen we breathe We use for energy Water

Electron Transport Chain Uses the high-energy electrons from the Kreb’s cycle to convert ADP to ATP. Electrons are passed from one carrier protein to the next and finally combine with hydrogen ions & oxygen to form water.