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Cell Energy- ATP Photosynthesis and Cellular Respiration
Chapter 10 Cell Energy- ATP Photosynthesis and Cellular Respiration
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Cool “Fires” Attract Mates and Meals
Fireflies use light, instead of chemical signals, to send signals to potential mates Females can also use light flashes to attract males of other firefly species — as meals, not mates
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The light comes from a set of chemical reactions, the luciferin-luciferase system
Fireflies make light energy from chemical energy Life is dependent on energy conversions
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ENERGY AND THE CELL Living cells are compartmentalized by membranes
Membranes are sites where chemical reactions can occur in an orderly manner Living cells process energy by means of enzyme-controlled chemical reactions
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Energy is the capacity to perform work
Energy is defined as the capacity to do work All organisms require energy to stay alive Energy makes change possible
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Chemical reactions either store or release energy
Cells carry out thousands of chemical reactions The sum of these reactions constitutes cellular metabolism
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ATP shuttles chemical energy within the cell
In cellular respiration, some energy is stored in ATP molecules ATP powers nearly all forms of cellular work ATP molecules are the key to energy coupling
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Adenosine triphosphate Adenosine diphosphate (ADP)
When the bond joining a phosphate group to the rest of an ATP molecule is broken by hydrolysis, the reaction supplies energy for cellular work Adenine Phosphate groups Hydrolysis Energy Ribose Adenosine triphosphate Adenosine diphosphate (ADP)
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Potential energy of molecules
How ATP powers cellular work Reactants Products Potential energy of molecules Protein Work
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Dehydration synthesis
The ATP cycle Hydrolysis Dehydration synthesis Energy from exergonic reactions Energy for endergonic reactions
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Life in the Sun Light is central to the life of a plant
Photosynthesis is the most important chemical process on Earth It provides food for virtually all organisms Plant cells convert light into chemical signals that affect a plant’s life cycle
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Light can influence the architecture of a plant
Plants that get adequate light are often bushy, with deep green leaves Without enough light, plants become tall and spindly with small pale leaves Too much sunlight can damage a plant Chloroplasts and carotenoids help to prevent such damage
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AN OVERVIEW OF PHOTOSYNTHESIS
Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water Carbon dioxide Water Glucose Oxygen gas PHOTOSYNTHESIS
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Autotrophs are the producers of the biosphere
Plants, some protists, and some bacteria are photosynthetic autotrophs They are the ultimate producers of food consumed by virtually all organisms
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On land, plants such as oak trees and cacti are the predominant producers
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In aquatic environments, algae and photosynthetic bacteria are the main food producers
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Photosynthesis occurs in chloroplasts
In most plants, photosynthesis occurs primarily in the leaves, in the chloroplasts A chloroplast contains: stroma, a fluid grana, stacks of thylakoids The thylakoids contain chlorophyll Chlorophyll is the green pigment that captures light for photosynthesis
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The location and structure of chloroplasts
LEAF CROSS SECTION MESOPHYLL CELL LEAF Mesophyll CHLOROPLAST Intermembrane space Outer membrane Granum Inner membrane Grana Stroma Thylakoid compartment Stroma Thylakoid
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Plants produce O2 gas by splitting water
The O2 liberated by photosynthesis is made from the oxygen in water
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Overview: Photosynthesis occurs in two stages linked by ATP and NADPH
The complete process of photosynthesis consists of two linked sets of reactions: the light reactions and the Calvin cycle The light reactions convert light energy to chemical energy and produce O2 The Calvin cycle assembles sugar molecules from CO2 using the energy-carrying products of the light reactions
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LIGHT REACTIONS (in grana) CALVIN CYCLE (in stroma)
An overview of photosynthesis H2O CO2 Chloroplast Light NADP+ ADP + P LIGHT REACTIONS (in grana) CALVIN CYCLE (in stroma) ATP Electrons NADPH O2 Sugar
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THE LIGHT REACTIONS: CONVERTING SOLAR ENERGY TO CHEMICAL ENERGY
Certain wavelengths of visible light drive the light reactions of photosynthesis Gamma rays Micro- waves Radio waves X-rays UV Infrared Visible light Wavelength (nm)
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Reflected light Light Chloroplast Absorbed light Transmitted light
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Photosystems capture solar power
Each of the many light-harvesting photosystems consists of: an “antenna” of chlorophyll and other pigment molecules that absorb light a primary electron acceptor that receives excited electrons from the reaction-center chlorophyll
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Primary electron acceptor
PHOTOSYSTEM Photon Reaction center Pigment molecules of antenna
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Fluorescence of isolated chlorophyll in solution
Heat Photon (fluorescence) Photon Chlorophyll molecule
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Primary electron acceptor
Excitation of chlorophyll in a chloroplast Primary electron acceptor Other compounds Photon Chlorophyll molecule
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In the light reactions, electron transport chains generate ATP, NADPH, and O2
Two connected photosystems collect photons of light and transfer the energy to chlorophyll electrons The excited electrons are passed from the primary electron acceptor to electron transport chains Their energy ends up in ATP and NADPH
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Photosystem II regains electrons by splitting water, leaving O2 gas as a by-product
Primary electron acceptor Electron transport Primary electron acceptor Electron transport chain Photons Energy for synthesis of PHOTOSYSTEM I PHOTOSYSTEM II by chemiosmosis
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ELECTRON TRANSPORT CHAIN
The production of ATP by chemiosmosis in photosynthesis Thylakoid compartment (high H+) Light Light Thylakoid membrane Antenna molecules Stroma (low H+) ELECTRON TRANSPORT CHAIN PHOTOSYSTEM II PHOTOSYSTEM I ATP SYNTHASE
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THE CALVIN CYCLE: CONVERTING CO2 TO SUGARS
ATP and NADPH power sugar synthesis in the Calvin cycle The Calvin cycle occurs in the chloroplast’s stroma This is where carbon fixation takes place and sugar is manufactured CALVIN CYCLE OUTPUT:
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Details of the Calvin cycle
INPUT: 3 In a reaction catalyzed by rubisco, 3 molecules of CO2 are fixed. CO2 Step Carbon fixation. 1 1 3 P P 6 P RuBP 3-PGA 6 ATP 3 ADP Step Energy consumption and redox. 2 6 ADP + P 3 ATP CALVIN CYCLE 2 6 4 NADPH 6 NADP+ Step Release of one molecule of G3P. 3 5 P 6 P G3P G3P 3 Step Regeneration of RuBP. 4 Glucose and other compounds OUTPUT: 1 P G3P
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Photosystem II Electron transport chains Photosystem I
PHOTOSYNTHESIS REVIEWED AND EXTENDED Review: Photosynthesis uses light energy to make food molecules Chloroplast Light A summary of the chemical processes of photo-synthesis Photosystem II Electron transport chains Photosystem I CALVIN CYCLE Stroma Electrons Cellular respiration Cellulose Starch Other organic compounds LIGHT REACTIONS CALVIN CYCLE
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Many plants make more sugar than they need
The excess is stored in roots, tuber, and fruits These are a major source of food for animals
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STAGES OF CELLULAR RESPIRATION AND FERMENTATION
Overview: Respiration occurs in three main stages Cellular respiration oxidizes sugar and produces ATP in three main stages Glycolysis occurs in the cytoplasm The Krebs cycle and the electron transport chain occur in the mitochondria
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An overview of cellular respiration
High-energy electrons carried by NADH GLYCOLYSIS ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS KREBS CYCLE Glucose Pyruvic acid Cytoplasmic fluid Mitochondrion
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Glycolysis harvests chemical energy by oxidizing glucose to pyruvic acid
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The Krebs cycle completes the oxidation of organic fuel
Acetyl CoA The Krebs cycle is a series of reactions in which enzymes strip away electrons and H+ from each acetyl group 2 KREBS CYCLE CO2
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Alpha-ketoglutaric acid
2 carbons enter cycle Oxaloacetic acid 1 Citric acid CO2 leaves cycle 5 KREBS CYCLE 2 Malic acid 4 Alpha-ketoglutaric acid 3 CO2 leaves cycle Succinic acid Step Acetyl CoA stokes the furnace Steps and NADH, ATP, and CO2 are generated during redox reactions. Steps and Redox reactions generate FADH2 and NADH. 1 2 3 4 5
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ELECTRON TRANSPORT CHAIN
Chemiosmosis in the mitochondrion Protein complex Intermembrane space Electron carrier Inner mitochondrial membrane Electron flow Mitochondrial matrix ELECTRON TRANSPORT CHAIN ATP SYNTHASE
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Cyanide, carbon monoxide ELECTRON TRANSPORT CHAIN
Connection:Certain Poisons can interrupt the “chain” Rotenone Cyanide, carbon monoxide Oligomycin ELECTRON TRANSPORT CHAIN ATP SYNTHASE
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ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS
For each glucose molecule that enters cellular respiration, chemiosmosis produces up to 38 ATP molecules Cytoplasmic fluid Mitochondrion Electron shuttle across membranes KREBS CYCLE GLYCOLYSIS 2 Acetyl CoA 2 Pyruvic acid KREBS CYCLE ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS Glucose by substrate-level phosphorylation used for shuttling electrons from NADH made in glycolysis by substrate-level phosphorylation by chemiosmotic phosphorylation Maximum per glucose:
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Fermentation is an anaerobic alternative to aerobic respiration
Under anaerobic conditions, many kinds of cells can use glycolysis alone to produce small amounts of ATP But a cell must have a way of replenishing NAD+
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In alcoholic fermentation, pyruvic acid is converted to CO2 and ethanol
This recycles NAD+ to keep glycolysis working released GLYCOLYSIS 2 Pyruvic acid 2 Ethanol Glucose
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In lactic acid fermentation, pyruvic acid is converted to lactic acid
As in alcoholic fermentation, NAD+ is recycled Lactic acid fermentation is used to make cheese and yogurt GLYCOLYSIS 2 Pyruvic acid 2 Lactic acid Glucose
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Food molecules provide raw materials for biosynthesis
In addition to energy, cells need raw materials for growth and repair Some are obtained directly from food Others are made from intermediates in glycolysis and the Krebs cycle Biosynthesis consumes ATP
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ATP needed to drive biosynthesis Cells, tissues, organisms
Biosynthesis of macromolecules from intermediates in cellular respiration ATP needed to drive biosynthesis GLUCOSE SYNTHESIS KREBS CYCLE Acetyl CoA Pyruvic acid G3P Glucose Amino groups Amino acids Fatty acids Glycerol Sugars Proteins Fats Polyscaccharides Cells, tissues, organisms
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The fuel for respiration ultimately comes from photosynthesis
All organisms have the ability to harvest energy from organic molecules Plants, but not animals, can also make these molecules from inorganic sources by the process of photosynthesis
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