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Cellular Respiration. Chemical Energy and Food. Food is the energy source for cells. The energy in food is measured in calories. A calorie is the amount of energy needed to raise the temperature of 1 gram of water 1 degree Celsius. There are 3811 calories in one gram of sugar glucose. - PowerPoint PPT Presentation
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Cellular Respiration
Chemical Energy and Food• Food is the energy source for cells. The energy in food is
measured in calories.• A calorie is the amount of energy needed to raise the
temperature of 1 gram of water 1 degree Celsius. There are 3811 calories in one gram of sugar glucose.
• The cell doesn’t burn glucose directly but converts into an energy source, ATP, through a process that begins with the pathway called glycolysis.
Glycolysis• Glycolysis is the process in which one molecule of glucose is
broken in half, producing two molecules of pyruvic acid, a three carbon compound.
• Glycolysis takes place in the cytoplasm of a cell.• In the process of breaking glucose in half two molecules of ATP
are needed but four molecules of ATP are produced creating a net gain of two molecules of ATP
• 4 high energy electrons are also removed and added to NAD+ (nicotinamide adenine dinucleotide) creating NADH, which helps pass energy from glucose to other pathways in the cell.
Glucose
To the electron transport chain
Glycolysis
2 Pyruvic acid
Glucose
Glycolysis Krebs cycle
Electrontransport
Fermentation (without oxygen)
Alcohol or lactic acid
Chemical Pathways After Glycolysis
Fermentation• When oxygen is not present, fermentation follows glycolysis• ● Fermentation releases energy from food molecules by producing ATP in
the absence of oxygen, this is an anaerobic process.• ● There are two main types of fermentation: 1) Alcoholic fermentation2) Lactic acid fermentation• ● Alcoholic fermentation example is yeast which causes carbon dioxide to
form and make bread rise.• ● pyruvic acid + NADH alcohol + CO2 + NAD+
Fermentation
• ● Lactic acid fermentation:• Pyruvic acid + NADH lactic acid + NAD+• ● Lactic acid is produced in your muscles during rapid exercise
when the body cannot supply enough oxygen to the tissues.• ● “FEEL THE BURN” is actually the result of a build up of lactic
acid in the muscles and can become painful and lead to cramps.
Glucose Pyruvic acidLactic acid
Lactic Acid Fermentation
Overview of Cellular Respiration
• If oxygen is present, The Krebs Cycle and electron transport chain follow glycolysis
• Glycolysis, the Krebs Cycle, and the electron transport chain make up the process called cellular respiration.
• Cellular respiration is the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen (an aerobic process).
Cellular Respiration Chemical Equation
GlucoseGlycolysis
Cytoplasm
Pyruvic acid
Electrons carried in NADH
Krebs Cycle
Electrons carried in NADH
and FADH2
Electron Transport Chain
Mitochondrion
Cellular Respiration: An Overview
Mitochondrion
The Krebs Cycle (Citric Acid Cycle)• The Krebs cycle is the 2nd stage of cellular respiration.
(glycolysis is the 1st stage)• During the Krebs cycle, pyruvic acid is broken down into
carbon dioxide in a series of energy-extracting reactions.• The Krebs cycle is also known as the citric acid cycle, because
citric acid is one of its 1st products.
Stages Of The Krebs Cycle1. The Krebs cycle starts when pyruvic acid formed by glycolysis enters the
mitochondrion.2. The pyruvic acid is broken down into carbon dioxide and a 2-carbon acetyl
group.3. The 2 carbons of the acetyl group join a 4-carbon compound to produce
citric acid. The Krebs cycle continues in a series of reactions. In these reactions, two energy carriers accept high-energy electrons. NAD+ is changed to NADH, and FAD is changed to FADH2. These molecules carry high energy electrons to the electron transport chain. The carbon dioxide is released as a waste product.
Citric Acid Production
The Krebs Cycle
Mitochondrion
The Electron Transport Chain (ETC)• The ETC is the 3rd and final stage of cellular respiration.• The ETC uses the high energy electrons to change ADP into ATP.• In the ETC, high energy electrons move from one carrier protein to the
next.• At the end of the chain, oxygen pulls electrons from the final carrier
molecule. These electrons join with hydrogen ions, forming water.• Each transfer along the chain releases a small amount of energy. ATP
synthase uses the energy to produce ATP.
Electron Transport Chain
Electron TransportHydrogen Ion Movement
ATP Production
ATP synthase
Channel
Inner Membrane
Matrix
Intermembrane Space
Mitochondrion
Cellular Respiration Overview
Glucose(C6H1206)
+Oxygen
(02)
Glycolysis KrebsCycle
ElectronTransport
Chain
Carbon Dioxide
(CO2)+
Water(H2O)
ATP Totals For Cellular Respiration• ● The totals for the cellular respiration cycle are as follows:• -Glycolysis: +4 ATP – 2 ATP = Net gain 2 ATP• -Krebs Cycle and ETC: +32 ATP • -Net gain for entire cycle is 34 ATP• Note: remember there are 2 ATP used in glycolysis, therefore
only 34 ATP are realized for the cell’s further needs. • -The total number of ATP molecules formed during cellular
respiration is 36
The Partnership Between Photosynthesis And Cellular Respiration
• The energy flows in photosynthesis and cellular respiration occur in opposite directions.
• On a global level, photosynthesis removes carbon dioxide from the atmosphere and puts back oxygen.
• Cellular respiration removes oxygen from the atmosphere and puts back carbon dioxide.