Chapter 6 Cellular Respiration Student

Introduction  In eukaryotes, cellular respiration harvests energy from food, yields large amounts of ATP, – Used for?  What is the original source of energy? © 2012 Pearson Education, Inc.

6.1 The relationship between C.R. and Photosynthesis How are these processes related? What is misleading about the following statement? “Plant cells perform photosynthesis, and animal cells perform cellular respiration”

6.2 Breathing supplies O 2 for use in cellular respiration and removes CO 2 How is your breathing (respiration) related to cellular respiration? © 2012 Pearson Education, Inc.

6.3 Cellular respiration banks energy in ATP molecules Cellular respiration is an exergonic process that transfers energy from the bonds in glucose to form ATP – Energy is gradually released Not like the marshmallow!  Other foods (organic molecules) can also be used as a source of energy. © 2012 Pearson Education, Inc.

Figure 6.3 Glucose OxygenWater Carbon dioxide C 6 H 12 O 6 O2O2 H2OH2O ATP6 6 6  Heat CO 2 Why are sweating and other body-cooling Mechanisms necessary during vigorous exercise? Why do you experience heavy breathing during vigorous exercise? Where do you see evidence of entropy?

6.4 CONNECTION: The human body uses energy from ATP for all its activities The average adult human needs about 2,200 kcal of energy per day. – About 75% of these calories are used to maintain a healthy body. Your brain utilizes 120 g or ¼ lb of glucose/day and approx. 15% of total O2 – Other activities ? © 2012 Pearson Education, Inc.

6.4 CONNECTION: The human body uses energy from ATP for all its activities A kilocalorie (kcal) is – the quantity of heat required to raise the temperature of 1 kilogram (kg) of water by 1 o C, – the same as a food Calorie © 2012 Pearson Education, Inc.

Figure 6.4 Activity kcal consumed per hour by a 67.5-kg (150-lb) person* Running (8–9 mph) Dancing (fast) Bicycling (10 mph) Swimming (2 mph) Walking (4 mph) Walking (3 mph) Dancing (slow) Driving a car Sitting (writing) *Not including kcal needed for body maintenance

6.5 Cells tap energy from electrons “falling” from organic fuels to oxygen The energy necessary for life is contained in the arrangement of electrons in chemical bonds in organic molecules. An important question is how do cells extract this energy? © 2012 Pearson Education, Inc.

6.5 Cells tap energy from electrons “falling” from organic fuels to oxygen When the carbon-hydrogen bonds of glucose are broken, electrons are transferred to oxygen. – Oxygen has a strong tendency to attract electrons. An “electron acceptor” – An electron loses potential energy when it “falls” to oxygen. © 2012 Pearson Education, Inc.

6.5 Cells tap energy from electrons “falling” from organic fuels to oxygen The movement of electrons from one molecule to another is an oxidation-reduction reaction, or redox reaction. In a redox reaction, – the loss of electrons from one substance is called oxidation, – the addition of electrons to another substance is called reduction, – a molecule is oxidized when it loses one or more electrons, and – reduced when it gains one or more electrons. Oxidation and reduction always happen together. © 2012 Pearson Education, Inc.

6.5 Cells tap energy from electrons “falling” from organic fuels to oxygen A cellular respiration equation is helpful to show the changes in hydrogen atom distribution. Glucose – loses its hydrogen atoms and (consists of 1 proton and 1 electron) – becomes oxidized to CO 2. Oxygen – gains hydrogen atoms and – becomes reduced to H 2 O. © 2012 Pearson Education, Inc.

Figure 6.5A Glucose  Heat C 6 H 12 O 6 O2O2 CO 2 H2OH2O ATP Loss of hydrogen atoms (becomes oxidized) Gain of hydrogen atoms (becomes reduced)

6.5 Cells tap energy from electrons “falling” from organic fuels to oxygen Enzymes are necessary to oxidize glucose and other foods. NAD + (Nicotinamide adenine dinucleotide) – is an important enzyme in oxidizing glucose, – accepts electrons, and – becomes reduced to NADH. © 2012 Pearson Education, Inc.

Figure 6.5B Becomes oxidized Becomes reduced 2H NAD  NADH HH HH 2 2 (carries 2 electrons)

6.5 Cells tap energy from electrons “falling” from organic fuels to oxygen There are other electron “carrier” molecules that function like NAD +. – They form a staircase where the electrons pass from one to the next down the staircase. – These electron carriers collectively are called the electron transport chain. – As electrons are transported down the chain, ATP is generated. © 2012 Pearson Education, Inc.

Figure 6.5C Controlled release of energy for synthesis of ATP NADH NAD  HH HH O2O2 H2OH2O ATP Electron transport chain 2 1

STAGES OF CELLULAR RESPIRATION © 2012 Pearson Education, Inc.

6.6 Overview: Cellular respiration occurs in three main stages Cellular respiration consists of a sequence of steps that can be divided into three stages. – Stage 1 – Glycolysis – Stage 2 – Pyruvate oxidation and citric acid cycle – Stage 3 – Oxidative phosphorylation © 2012 Pearson Education, Inc.

6.6 Overview: Cellular respiration occurs in three main stages Stage 1: Glycolysis – occurs in the cytoplasm, – begins cellular respiration, and – breaks down glucose into two molecules of a three- carbon compound called pyruvate. © 2012 Pearson Education, Inc.

6.6 Overview: Cellular respiration occurs in three main stages Stage 2: The citric acid cycle – takes place in mitochondria, – oxidizes pyruvate to a two-carbon compound, and – supplies the third stage with electrons. © 2012 Pearson Education, Inc.

6.6 Overview: Cellular respiration occurs in three main stages Stage 3: Oxidative phosphorylation – involves electrons carried by NADH and FADH 2, – shuttles these electrons to the electron transport chain embedded in the inner mitochondrial membrane, – involves chemiosmosis, and – generates ATP through oxidative phosphorylation associated with chemiosmosis. © 2012 Pearson Education, Inc.

Figure 6.6 NADH FADH 2 ATP CYTOPLASM Glycolysis Electrons carried by NADH Glucose Pyruvate Pyruvate Oxidation Citric Acid Cycle Oxidative Phosphorylation (electron transport and chemiosmosis) Mitochondrion Substrate-level phosphorylation Oxidative phosphorylation