How do you know when you need to eat? How do you feel when you are hungry? Empty stomach Dizzy Weak Sensations vary from person to person but the bottom line is… We all need food!!!

Cellular respiration actually consists of more than two dozen chemical reactions. Many of the reactions take place in specialized organelles—mitochondria.

An envelope of two membranes encloses the mitochondrion. There is a space between the outer and inner membranes. The highly folded inner membrane (cristae) encloses a thick fluid called the matrix.

A Road Map for Cellular Respiration The three main stages of cellular respiration: 1. Glycolysis happens in the cell’s cytoplasm 2. the Krebs cycle happens in the matrix 3. electron transport with ATP synthase ( inner membrane) Mitochondria are the sites of 2 stages of cellular respiration.

An Overview of Cellular Respiration

Flowchart Section 9-2 Glucose (C 6 H 12 O 6 ) + Oxygen (6O 2 ) Glycolysis Krebs Cycle Electron Transport Chain Carbon Dioxide (6CO 2 ) + Water (6H 2 O) Cellular Respiration

What is ATP and ADP? Adenosine triphosphate A molecule that can give away one phosphate to help “energize” another molecule The bond that is broken (between 2 nd & 3 rd phosphate) releases energy When a phosphate is given away it becomes ADP (adenosine diphosphate) Can be regenerated when a phosphate again binds to ADP

ATP Chemical fuel of the cell Made up of 5 carbon sugar 3 phosphate groups Nitrogenous base- Adenine ATP is which type of macromolecule? Nucleic acid

AdenineRibose3 Phosphate groups ATP

What is the difference between ATP and ADP? ATP – adenosine triphosphate Has three phosphate groups ADP – adenine diphosphate Only has 2 phosphate groups

ADPATP Energy Adenosine diphosphate (ADP) + PhosphateAdenosine triphosphate (ATP) Partially charged battery Fully charged battery Section 8-1 Figure 8-3 Comparison of ADP and ATP to a Battery

ATP Function 1) Chemical Work Synthesis of macromolecules 2) Transport Active transport across cell membrane 3) Mechanical work Muscle contractions All organisms both prokaryotic and eukaryotic use ATP!!!!

So what is cellular respiration? Process that releases energy by breaking down glucose (sugars) and other food molecules in the presence of oxygen (aerobic). What organelle does this occur in? Mitochondria!!!! This process occurs in all eukaryotic cells. 6O 2 +C 6 H 12 O 6  6CO 2 + 6H 2 O + energy So glucose is broken down to produce about ATP!

Overview of cellular respiration There are three main stages! Always starts with glycolysis! From there it depends on whether oxygen is present or not!

Glucose GlycolysisKrebs cycle Electron transport Fermentation (without oxygen) Alcohol or lactic acid Chemical Pathways Section 9-1

Usually though … Cellular respiration follows the following paths because oxygen is present Glycolysis Krebs cycle Electron transport chain Because oxygen is required for cellular respiration it is known as an aerobic process.

Glucose Glycolysis Cytoplasm Pyruvic acid Electrons carried in NADH Krebs Cycle Electrons carried in NADH and FADH 2 Electron Transport Chain Mitochondrion Figure 9–2 Cellular Respiration: An Overview Mitochondrion Section 9-1

Glycolysis Happens in cytoplasm after the cell’s reserve of ATP is used up (first few seconds of exercise) Does not require oxygen Takes glucose and breaks it down into 2 three carbon molecules (pyruvic acid) Needs 2 ATP molecules Makes 4 ATP molecules and 2 NADH energy molecules Only a small amount of energy is made (2 ATP because 2 are used in the process) Occurs quickly- cells can produce thousands of ATP molecules in milliseconds!

Glycolysis So how much energy was used? 2 ATP So what was your starting molecule? Glucose What were your products? 4 ATP 2 NADH 2 pyruvic acid molecules What was your net gain of ATP? 2 ATP

Krebs Cycle Happens after glycolysis Happens in the mitochondria Oxygen has to be present! During the Krebs Cycle pyruvic acid is broken down into CO 2 (carbon dioxide) NADH, ATP and FADH 2 in a series of energy-extracting reactions.

Citric Acid Production Figure 9–6 The Krebs Cycle Section 9-2 Mitochondrion

So What is Made in the Krebs Cycle? The energy tally from 2 molecules of pyruvic acid is during cell respiration is 8 NADH 2 FADH 2 2 ATP 6 CO 2 Because 1 glucose molecule forms 2 pyruvic acid molecules.

What is NAD, NADH, FAD, andFADH 2 ? They are compounds that store energy in the form of H atoms and then pass it on. In other words, they are electron carriers! NADH 2 and FADH 2 are the energized form. We will use the energy from these two molecules later on!

Electron Transport Chain Third and final part Happens in the mitochondria on the cristae Oxygen has to be present Uses High Energy electrons (NADH, FADH 2 ) from the Krebs Cycle and glycolysis to convert ADP to ATP and to form water (H 2 O) The Electron Transport Chain is made up of a series of carrier proteins located in the inner membrane of the mitochodrion.

Overview of ETC The energy from the high energy electrons from NADH and FADH2 is used to pump H+ across the cristae membrane, creating a concentration gradient. The H+ then diffuses back across the membrane through an ATPsynthase protein molecule. This protein attaches a P to an ADP, forming ATP. At the end of the chain, the used electrons combine with 2 H ions and an O, forming H2O

Figure 9–7 Electron Transport Chain Section 9-2 Electron Transport Hydrogen Ion Movement ATP Production ATP synthase Channel Inner Membrane Matrix Intermembrane Space Mitochondrion

So what are the products of ETC? Each pair of electrons can produce about 3 molecules of ATP 12 pairs of hydrogens (and associated electrons)available 2 from glycolysis 2 from pyruvic acid 8 from krebs cycle /movie.htm /movie.htm

Totals 2 ATP from glycolysis 34 ATP from Krebs and ETC 38% of a glucose molecule gives 36 ATP and then 62% of a glucose molecule is released as heat.

What happens when oxygen is not present? Glycolysis still occurs but Krebs and ETC will not. Anaerobic respiration – respiration then occurs when no oxygen is present This is called FERMENTATION! So if fermentation occurs, Krebs will not.

Fermentation Energy is released much faster than it is with cellular respiration. Fermentation releases energy from food by producing ATP in the absence of oxygen

Fermentation 2 Types Lactic acid fermentation Occurs with strenuous activity because oxygen cannot reach the cells fast enough to meet energy demands. Leads to sore muscles In order for the lactic acid to be broken down, oxygen is needed. Alcohol fermentation Yes, occurs in the production of consumable alcohol. Yeast go through this process.

Glucose Pyruvic acid Lactic acid Figure 9–4 Lactic Acid Fermentation Section 9-1