Cellular Respiration. Chapter 9 in the textbook

Transcription

1 Cellular Respiration Chapter 9 in the textbook

2 Chemical Energy and Food The equation for cellular respiration is catabolic. Catabolic Reactions: a chemical reaction that breaks down larger molecules into smaller units. Catabolic reactions are exergonic: energy is released. Anabolic reaction: an endergonic reaction that builds molecules from smaller units. Photosynthesis is an anabolic reaction.

3 Chemical Energy and Food Oxidation: Glucose loses electrons (and hydrogens) Reduction: Oxygen gains electrons (and hydrogens) Cellular Respiration is an oxidation/reduction reaction Oxidation: The loss of electrons Reduction: The gain of electrons In cellular respiration glucose is oxidize and oxygen is reduced Hydrogen is a source of electrons

4 Chemical Energy and Food Heterotrophic organisms get the glucose from the food they consume. Calorie: a unit to measure the amount of energy in food. 1 Calorie = the amount of energy needed to raise the temperature of kilogram (or liter) of water 1 o C 1 calorie = the amount of energy needed to raise the temperature of gram (or milliliter) of water 1 o C 1 Calorie = 1,000 calories Unit for measuring energy in food = Calorie

5 Chemical Energy and Food Carbohydrates, lipids and proteins can all be broken down to release energy. 1 Gram of Carbohydrates = 4 Calories The bodies primary source of energy Only a small amount of carbohydrates can be stored in the body. Glycogen is a polysaccharide that is created to store glucose Amylase: An enzyme that breaks down polysaccharides like glycogen and starch into glucose to begin cellular respiration.

6 Chemical Energy and Food 1 Gram of Lipids = 9 Calories The bodies secondary source of energy Carbohydrates can be converted to lipids for storage. Can body can store an unlimited amount of lipids. 1 Gram of Proteins = 4 Calories Lipids and Proteins are broken down with processes other than cellular respiration. Proteins in food are broken down into amino acids which are used as building material. The body can break down proteins into energy as a last resort.

7 An Overall of Cellular Respiration Cellular respiration occurs at the mitochondria: Parts of the Mitochondria Outer Membrane: contains many pore proteins to allow materials in and out of the mitochondria. Inner Membrane: contains enzymes essential for cell respiration. Cristae: the folded sections of the inner membrane. Inner membrane is about 5 times larger than the outer membrane (increases surface area and rate of respiration) The inner membrane must be folded to fit inside

8 An Overall of Cellular Respiration Intermembrane Space: space between the inner and outer membrane of the mitochondria. Matrix: the area inside of the inner membrane. Contains proteins, cytosol, and mitochondrial DNA.

9 An Overall of Cellular Respiration Cellular respiration happens slowly and in many steps. If all the energy was release in one step... Most would be lost as light and heat. Three steps of cellular respiration 1. Glycolysis 2. Krebs Cycle 3. Electron Transport Chain

10 Step 1: Glycolysis Location: In the cytosol just outside the mitochondria Purpose: Splits glucose into two molecules of pyruvic acid. To begin glycolysis the cell needs to invest two ATP Glycolysis produces 4 ATP and 2 NADH (NADH is similar to NADPH in photosynthesis)

11 Location: The mitochondrial matrix Pyruvic acid from glycolysis enters the mitochondria. Purpose: To break down the pyruvic acid into CO2. Every turn of the Krebs Cycle produces: 3 CO2 1 ATP 1 FADH2 (similar to NADH) 4 NADH Step 2: Krebs Cycle

12 Step 2: Krebs Cycle What happens to the products of the Krebs cycle? Carbon dioxide is lost to the atmosphere ATP can be used directly to supply energy for the cell High energy electron carriers move into the electron transport chain.

13 Step 3: Electron Transport Chain Location: The inner membrane of the mitochondria Purpose: Use the energy from NADH and FADH 2 to convert ADP into ATP. NADH and FADH 2 were produced during glycolysis and the Kred s cycle. NADH 3 ATP s FADH 2 2 ATP s

14 Step 3: Electron Transport Chain The Process 1. NADH and FADH2 give high energy elections to protein pumps in the inner mitochondria membrane. 2. Energy from the electrons is used to pump H+ ions from to matrix to the intermembrane space. 3. There is now a higher concentration of H+ in the intermembrane space compared to the matrix. 4. Chemiosmosis: H+ ions flow back to the matrix through an enzyme called ATP Synthase 5. ATP Synthase: using the kinetic energy from H+ moving down a concentration gradient to convert ADP into ATP

15 Step 3: Electron Transport Chain

16 Cell Respiration Summary The totals: 1 glucose = 36 ATP Importance of Oxygen: Oxygen is the final electron acceptor after the electron transport chain. Oxygen combines with electrons and H+ to form H 2 O

17 Fermentation Fermentation: an anaerobic process that produces ATP from glucose. Anaerobic: it occurs in the absence of oxygen. Cell Respiration is an aerobic process (it requires) oxygen. Glycolysis occurs with or without oxygen. Krebs Cycle and Electron Transport Chain do not occur in the absence of oxygen.

18 Fermentation Location: In the cytosol Purpose: Converts NADH back into NAD+ so that glycolysis can continue. During fermentation all of the ATP is produced during glycolysis. Glycolysis would not be able to occur if there was no NAD+

19 Fermentation There are two different types of fermentation: 1. Lactic Acid Fermentation 2. Alcoholic Fermentation

20 Lactic Acid Fermentation Happens in muscle cells during exercise when body can t get oxygen to tissues fast enough. Lactic acid builds up in muscles causing soreness. Bacteria use lactic acid fermentation to several foods: yogurt, cheese, sour cream, pickles, sauerkraut, kimchi.

21 Alcoholic Fermentation Occurs in yeast cells Yeast is added to bread recipes because the CO2 produced by fermentation make the bread rise. Alcohol is toxic to cells, if too much fermentation occurs and the alcohol is allow to build up it will kill the yeast cells.

22 Comparing Respiration and Fermentation Advantages Disadvantages Efficiency Fermentation Fastest way to produce ATP Occurs without oxygen Only provides enough energy for a few seconds of activity. Produces Lactic acid 2 ATP per Glucose Cellular Respiration Can generate enough ATP for long periods of activity Releases energy more slowly Needs oxygen 36 ATP per Glucose