Cellular Respiration: Harvesting Chemical Energy

Food=chemical energy Cellular Respiration All living things need energy Energy in the form of… Food=chemical energy

Living things get most of the energy they need from glucose. Autotrophs make glucose using photosynthesis Heterotrophs get glucose from food they eat

Cellular Respiration is the process of extracting stored energy from glucose and storing it in the high energy bonds of ATP.

What Is ATP? Energy used by all Cells Adenosine Triphosphate Organic molecule containing high-energy Phosphate bonds 5

Chemical Structure of ATP 6

What Does ATP Do for You? It supplies YOU with ENERGY! 7

Why ATP? An analogy to money… Glucose in our food is a great source of energy! ($100 bill) However, individual cell processes may only require a small amount of energy ($1 bill)

Analogy: most vending machines do not accept $100 bills Analogy: most vending machines do not accept $100 bills! We need a smaller form of “currency” for these processes. ATP is this important cellular “currency” for life. ATP releases more appropriate amounts of energy for the individual cellular processes than does glucose

How Do We Get Energy From ATP? By breaking the high- energy bonds between the last two phosphates in ATP 10

Results in ADP -Adenosine Diphosphate (only 2 phosphates)

How efficient is cell respiration? Energy released from glucose (as heat and light) Energy released from glucose banked in ATP Gasoline energy converted to movement 100% About 40% 25% Burning glucose in an experiment “Burning” glucose in cellular respiration Burning gasoline in an auto engine

ATP is broken down into ADP + P and then remade again with the help of enzymes in the ATP/ADP cycle

Respiration There are two types of Respiration: Anaerobic Respiration and Aerobic Respiration Anaerobic Respiration – without oxygen (referred to as Fermentation) Aerobic Respiration – with oxygen (referred to as Cellular Respiration)

The First Stage for both types of respiration, is called Glycolysis

Glycolysis glyco means “glucose/sugar”, and lysis means “to split”. Therefore, glycolysis means “to split glucose” C-C-C-C-C-C C-C-C

Glycolysis Occurs in the cytoplasm just outside of mitochondria. Needs no oxygen and makes 2 ATP Process in which 1 glucose in broken in half, producing 2 molecules of pyruvic acid C-C-C-C-C-C C-C-C

Anaerobic Respiration/Fermentation (Fermentation does NOT use oxygen) After Glycolysis, the respiration process stops with 2 ATP made. The pyruvate is then changed into one of several types of molecules, depending on the type of organism doing the fermentation

Anaerobic Respiration Anaerobic respiration is involved at some stage in the preparation of these foodstuffs

1. Alcoholic Fermentation, and 2. Lactic Acid Fermentation The 2 most common forms of Anaerobic Respiration are: 1. Alcoholic Fermentation, and 2. Lactic Acid Fermentation

Alcoholic Fermentation is carried out by yeast, a kind of fungus.

Alcoholic Fermentation Uses only Glycolysis. Produces ATP when O2 is not available.

Alcoholic Fermentation C6H12O6 2 C2H5OH + 2 CO2 (Ethyl Alcohol or Ethanol) As a result of Alcoholic Fermentation, Glucose is converted into 2 molecules of Ethyl Alcohol and 2 Molecules of Carbon Dioxide.

Wine making Grapes are crushed and the sugar they contain is fermented by yeasts to produce alcohol and carbon dioxide. The carbon dioxide usually escapes but if the wine is bottled before fermentation is complete, the carbon dioxide dissolves and escapes as bubble when the bottle is opened This is the case with ‘sparkling’ wines such as Champagne

Brewing In brewing beer, a sugary product (malt) is dissolved out of germinating barley Yeast is added to this solution and fermentation begins, producing alcohol and carbon dioxide Some of the carbon dioxide escapes but the rest dissolves in the beer when it is bottled or put into casks When the bottles or casks are opened, the dissolved CO2 escapes as bubbles

Baking In baking, yeast is added to a mixture of flour and water, made into the form of a dough The yeast first changes the flour starch into sugar and then ferments the sugar into alcohol and CO2 The CO2 forms bubbles in the dough which cause it to expand (‘rise’) When the dough is baked, the heat evaporates the alcohol but makes the trapped bubbles expand giving the bread a ‘light’ texture

Dough rising 36 The yeast is mixed with the dough After 1 hour in a warm place the dough has risen as a result of the carbon dioxide produced by the yeast

37 The ‘holes’ in the bread are made by the carbon dioxide bubbles. This gives the bread a ‘light’ texture

Lactic Acid Fermentation Uses only Glycolysis. Does NOT use O2 Produces ATP when O2 is not available.

Lactic Acid Fermentation Performed by bacteria Results in yogurt, pickles, sauerkraut and kimchi

Lactic Acid Fermentation Carried out by human muscle cells under oxygen debt. Lactic Acid is a toxin and causes fatigue, soreness and stiffness in muscles.

Fermentation - Summary Releases 2 ATP from the breakdown of a glucose molecule Provides ATP to a cell even when O2 is absent.

Aerobic Respiration requires oxygen!

There are three phases to Aerobic Respiration ... they are: 1. Glycolysis (same as the glycolysis of anaerobic respiration) 2. Krebs cycle (AKA - Citric Acid cycle) 3. Oxidative Phosphorylation and The Electron Transport Chain

Aerobic Respiration takes place in both the cytoplasm (Glycolysis) and in the mitochondria of a cell

Comparing Aerobic and Anaerobic Respiration requires a mitochondrion and oxygen is a three phase process Anaerobic – does not require oxygen consists of one phase only-Glycolysis

Mitochondria Organelle where cellular respiration takes place.

Cellular Respiration C6H12O6 + 6O2  6CO2 + 6H2O + 36 ATP An exergonic, oxygen (O2) requiring process that uses energy extracted from organic molecules (glucose) to produce energy (ATP) and water (H2O). C6H12O6 + 6O2  6CO2 + 6H2O + 36 ATP Glucose oxygen Carbon water dioxide ENERGY

Breakdown of Cellular Respiration Three main parts (stages). 1. Glycolysis (splitting of sugar) 2. Krebs Cycle (Citric Acid Cycle) 3. Electron Transport Chain (ETC) and Oxidative Phosphorylation

1. Glycolysis Occurs in the cytoplasm just outside of mitochondria. Needs no oxygen and makes 2 ATP Process in which 1 glucose in broken in half, producing 2 molecules of pyruvic acid C-C-C-C-C-C C-C-C

2. Krebs Cycle (Citric Acid Cycle) Occurs in the mitochondria Makes 2 ATP Pyruvic acid is broken down into CO2 in a series of energy-extracting reactions Citric Acid is created in this cycle thus giving it the nickname Citric Acid Cycle.

3. Electron Transport Chain (ETC) Location: mitochondria Makes 32 ATP Uses high-energy e- from Krebs Cycle to make ATP

ATP TOTAL ATP YIELD The ETC makes the most ATP In total cellular respiration makes 36 ATP ATP

Krebs Cycle and ETC require oxygen to work!

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

One example of respiration in ourselves 15 One example of respiration in ourselves 2. The lungs absorb oxygen from the air 1. Air taken in 1.Food taken in 2.The stomach and intestine digest food. One of the products is glucose 3.The blood stream carries glucose and oxygen to the muscles The water produced as a waste product of respiration is picked up by the blood stream and may be lost in sweat, water vapour from the lungs or in urine Glucose and oxygen react to produce energy for muscle contraction 4 RESPIRATION 5 Carbon dioxide is carried to the lungs by the blood

Fermentation (without oxygen) Respiration - Summary Glucose Krebs cycle Electron transport Glycolysis Fermentation (without oxygen) Alcohol or Lactic Acid