Chapter 9 Cellular Respiration

Why do we need food? Food provides living things with energy Food serves as a source of raw materials Food serves as a source of energy

Chemical Energy and Food What is a calorie? Amount of energy needed to raise the temp. of 1 gram of water 1 degree Celsius The Calorie (capital C) that is used on food labels is a kilocalorie, 1000 calories How many calories make up 1 Calorie? 1000 Cells don’t “burn” glucose, they gradually release the amount of energy inside of them (calories)

Chemical Energy and Food How do our bodies release the energy from food for us to use it? Cellular Respiration Cellular respiration begins with a pathway called glycolysis How much energy is released through glycolysis? A small amount *glycolysis can occur with or without oxygen

Overview of Cellular Respiration Glycolysis + Krebs Cycle + Electron Transport Chain = Cellular Respiration What is cellular respiration? The process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

Overview of Cellular Respiration Equations for cellular respiration: 6O2 + C6H12O6  6CO2 + 6H2O + Energy 6 oxygen + 1 glucose  6 carbon dioxide + 6 water + Energy

Overview of Cellular Respiration Cellular respiration does not take place in just one step because most of the energy would be lost as heat The cells trap small amounts of energy in ATP molecules There are 3 different stages of cellular respiration

Overview of Cellular Respiration Glycolysis – takes place in the cytoplasm The Krebs Cycle - takes place in the mitochondrion The Electron Transport Chain (ETC) – takes place in the mitochondrion

Workbook Pages 97 & 98 Numbers 1 – 10 only Individually You have 15 minutes

Glycolysis The first set of reactions in cellular respiration is glycolysis. Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid (a 3-Carbon compound)

Glycolysis Glycolysis is an energy releasing process, but the cell needs energy to get it started The cell gets glycolysis going by using 2 molecules of ATP The two molecules act as an investment – before you can begin something new, you have to start with a base

Glycolysis When glycolysis is completed, 4 ATP have been produced, but there is only a net gain of 2 ATP. Why? The cell puts in 2 ATP in the beginning The cell produces 4 ATP through glycolysis * 4 new ATP – 2 old ATP = 2 net ATP

Glycolysis Glycolysis removes 4 high energy electrons and passes them to a carrier, NAD+ NAD+ is an electron carrier that accepts a pair of high energy electrons and transfers them to another molecule NAD + 2 e- + 2 H+ = NADH

Glycolysis What is the function of NAD + in glycolysis? To pass energy from glucose to other pathways in the cell, using the ETC (electron transport chain)

Glycolysis Advantage! Glycolysis can supply chemical energy to cells when oxygen is not available The process of glycolysis does not require oxygen

Glycolysis Advantage! Glycolysis produces small amounts of energy very fast! Cells can make 1000s of ATP in milliseconds! Problem when a cell generates a large amount of ATP, all of the NAD+ molecules fill up with electrons, and ATP production stops!

Workbook Page 98 #s 11-17 Individually

Fermentation When oxygen is not present, glycolysis is followed by a different pathway. Glycolysis without oxygen Fermentation Fermentation releases energy from food molecules by producing ATP in the absence of oxygen.

Fermentation During fermentation, cells converts NADH to NAD+ by giving high-energy electrons back to pyruvic acid NADH is converted back into the electron carrier NAD+, which allows glycolysis to continue producing a steady supply of ATP.

Fermentation Fermentation does not require oxygen, so it is said to be anaerobic The two main types of fermentation are Alcoholic fermentation Lactic acid fermentation

Fermentation Alcoholic fermentation Yeasts and other microscopic organisms use this process The waste products of fermentation are ethyl alcohol and carbon dioxide The equation after glycolysis: Pyruvic acid + NADH  alcohol + CO2 + NAD+

Fermentation Alcoholic fermentation is what causes bread dough to rise When the yeast runs out of oxygen, it starts to ferment for energy – this gives off CO2 bubbles that make the air spaces in bread The small amount of alcohol also produced in the bread evaporates when the bread is baked

Fermentation Lactic Acid Fermentation Lactic acid fermentation converts glucose into lactic acid Glycolysis breaks the glucose into 2 molecules of pyruvic acid, which are converted to lactic acid Equation after glycolysis Pyruvic acid + NADH  lactic acid + NAD+

Fermentation Lactic acid is produced in your muscles during exercise when the body cannot supply enough oxygen to the tissues Without enough oxygen, your body cannot supply enough ATP Your muscle cells rapidly produce ATP by lactic acid fermentation

Fermentation How do you know when your muscle cells have gone through lactic acid fermentation? Your muscles are sore! Lactic acid buildup causes a painful, burning sensation.

Fermentation Unicellular organisms also go through lactic acid fermentation Prokaryotes (bacteria) are used in foods and drinks because they give off lactic acid as a waste product Lactic acid is a useful ingredient in Cheese, yogurt, buttermilk, sour cream, pickles, and sauerkraut

Workbook Finish section 9-1 in your workbook