PHOTOSYNTHESIS and

RESPIRATION

UNIT 5 CHAPTER 5

SECTION SECTION 11PhotosynthesisPhotosynthesis

Energy and Living ThingsEnergy and Living Things

PhotosynthesisPhotosynthesis is the process in is the process in which light energy is converted into which light energy is converted into chemical energy. chemical energy.

AutotrophsAutotrophs (plants and some (plants and some bacteria) use the sun’s energy to bacteria) use the sun’s energy to carry out carry out photosynthesisphotosynthesis, and are , and are therefore the foundation of all living therefore the foundation of all living systems.systems.

Breaking Down Food For EnergyBreaking Down Food For Energy

AutotrophsAutotrophs are are organisms organisms that use that use energy from energy from sunlight sunlight or from chemical bonds or from chemical bonds in inorganic substances in inorganic substances to make to make organic organic compoundscompounds..

HeterotrophsHeterotrophs are are organisms that must organisms that must consume other consume other organisms as food to get organisms as food to get their energy.their energy.

PhotosynthesisPhotosynthesis PhotosynthesisPhotosynthesis is the process by which is the process by which

plants, algae, and some bacteria use sunlight, plants, algae, and some bacteria use sunlight, carbon dioxide, and water to produce carbon dioxide, and water to produce carbohydrates and oxygen.carbohydrates and oxygen.

PhotosynthesisPhotosynthesis has has 3 stages3 stages::Stage 1Stage 1: : absorptionabsorption of light energy of light energy

Stage 2Stage 2: : conversionconversion of light energy into chemical of light energy into chemical energy, temporarily stored in energy, temporarily stored in ATPATP and and NADPHNADPH

Stage 3Stage 3: : storagestorage of chemical energy in of chemical energy in ATPATP and and

NADPH NADPH powers the powers the formationformation of organic molecules of organic molecules

PhotosynthesisPhotosynthesis PigmentsPigments are light-absorbing substances are light-absorbing substances

that absorb only certain wavelengths of light that absorb only certain wavelengths of light and reflect all others.and reflect all others.

ChlorophyllChlorophyll is the primary pigment is the primary pigment involved in photosynthesis. Chlorophyll involved in photosynthesis. Chlorophyll absorbsabsorbs mostly mostly blueblue and and redred light and light and reflectsreflects greengreen and and yellowyellow light. light.

This reflection of green and yellow light This reflection of green and yellow light makes many plants, especially their leaves, makes many plants, especially their leaves, look green.look green.

Photosynthesis Photosynthesis occurs in the occurs in the chloroplastschloroplasts and uses the and uses the pigment pigment chlorophyllchlorophyll..

PhotosynthesisPhotosynthesis The following chemical equation The following chemical equation

summarizes photosynthesis:summarizes photosynthesis:

66HH22OO + + 66COCO2 2 + + light light CC66HH1212OO66 + + 66OO22

REACTANTS: REACTANTS: water, carbon water, carbon dioxide, light energydioxide, light energy

PRODUCTS: PRODUCTS: glucose, oxygenglucose, oxygen

Stages of Photosynthesis:Stages of Photosynthesis:STAGE 1 - STAGE 1 - The Light-Dependent The Light-Dependent ReactionsReactions

STAGE 1: STAGE 1: These reactions are calledThese reactions are called the “ the “light light reactionsreactions,”,” or “or “light-dependent reactionslight-dependent reactions”” because the reactions because the reactions absorbabsorb light energy to light energy to make the organic compounds make the organic compounds glucoseglucose and and oxygenoxygen..

STAGE 1 STAGE 1 occurs in the occurs in the chloroplastschloroplasts on the on the thylakoid membrane thylakoid membrane where clusters of the where clusters of the pigment pigment chlorophyllchlorophyll are embedded. are embedded.

Other pigments used are Other pigments used are carotenoidscarotenoids that produce that produce yellowyellow and and orangeorange fall leaf colors, as well as the fall leaf colors, as well as the colors of many fruits, vegetables, and flowers.colors of many fruits, vegetables, and flowers.

Photosynthesis: Photosynthesis: Where Does it Occur?Where Does it Occur?

Thylakoid membrane

Photosynthesis: Photosynthesis: ThylakoidsThylakoids

ThylakoidsThylakoids are disk-shaped structures found in are disk-shaped structures found in the the chloroplastschloroplasts of leaf cells that contain of leaf cells that contain clusters of embedded pigments.clusters of embedded pigments.

These pigment molecules in the thylakoids of These pigment molecules in the thylakoids of chloroplasts absorb light energy.chloroplasts absorb light energy.

Electrons in the pigments are “excited” by Electrons in the pigments are “excited” by light, and jump from the chlorophyll molecules light, and jump from the chlorophyll molecules to other nearby molecules in the thylakoid to other nearby molecules in the thylakoid membrane. membrane.

The series of molecules along the thylakoid The series of molecules along the thylakoid membrane that excited electrons pass through membrane that excited electrons pass through as they jump along the chlorophyll molecules is as they jump along the chlorophyll molecules is called the called the electron transport chainelectron transport chain..

Photosynthesis: Photosynthesis: Stage 1Stage 1 Absorption Absorption of of Light EnergyLight Energy

The excited electrons that leave chlorophyll molecules The excited electrons that leave chlorophyll molecules must be replaced by other electrons. must be replaced by other electrons.

Plants get these replacement electrons from Plants get these replacement electrons from water water moleculesmolecules, H, H220.0.

The water molecules are split by an The water molecules are split by an enzymeenzyme inside the inside the thylakoid.thylakoid.

When water molecules are split, chlorophyll molecules When water molecules are split, chlorophyll molecules take the electrons from the hydrogen atoms, take the electrons from the hydrogen atoms, HH, , leaving hydrogen ions, leaving hydrogen ions, HH++..

The remaining oxygen atoms, The remaining oxygen atoms, OO, from the , from the disassembled water molecules combine to form disassembled water molecules combine to form oxygen gas, oxygen gas, OO22..

Photosynthesis: Photosynthesis: Stage 2Stage 2 ConversionConversion of of Light Energy Light Energy by by

Electron Transport ChainsElectron Transport Chains

Excited electrons lose some of their energy as Excited electrons lose some of their energy as they pass through these proteins. The energy they pass through these proteins. The energy lost is used to pump hydrogen ions into the lost is used to pump hydrogen ions into the thylakoid.thylakoid.

As the process continues, hydrogen ions become As the process continues, hydrogen ions become more concentrated inside the thylakoid than more concentrated inside the thylakoid than outside, producing a concentration gradient outside, producing a concentration gradient across the thylakoid membrane. across the thylakoid membrane.

The hydrogen ions will diffuse back out of the The hydrogen ions will diffuse back out of the thylakoid down their concentration gradient thylakoid down their concentration gradient through specialized carrier proteins, or through specialized carrier proteins, or proton proton pumpspumps..

Photosynthesis: Photosynthesis: Stage 2Stage 2 These proteins act as both These proteins act as both ion ion

channelschannels as well as as well as enzymesenzymes. .

As H+ pass through the As H+ pass through the channel portion of the protein, channel portion of the protein, the protein catalyzes a reaction the protein catalyzes a reaction in which a phosphate group is in which a phosphate group is added to added to ADPADP molecules to molecules to form form ATP ATP (ADP + P = ATP)(ADP + P = ATP)..

Thus, the movement of Thus, the movement of hydrogen ions across the hydrogen ions across the thylakoid membranes through thylakoid membranes through proton pumps provide the proton pumps provide the energy to produce ATP energy to produce ATP molecules. molecules.

inner thylakoid membrane

outer thylakoid membrane

Two Electron Transport Two Electron Transport ChainsChains

The The first electron transport chain first electron transport chain lies between two lies between two large clusters of pigment molecules and is used to large clusters of pigment molecules and is used to formform ATPATP..

A A second electron transport chain second electron transport chain lies next to the lies next to the sight of the first electron transport chain. sight of the first electron transport chain.

In this second chain, excited electrons combine with In this second chain, excited electrons combine with hydrogen ions (hydrogen ions (HH++) and an electron acceptor called ) and an electron acceptor called NADPNADP++ to form to form NADPHNADPH..

NADPHNADPH is an electron carrier and is important in is an electron carrier and is important in photosynthesis because it carries high energy photosynthesis because it carries high energy electrons needed to produce organic molecules.electrons needed to produce organic molecules.

Photosynthesis: Stage 3Photosynthesis: Stage 3The Light-Independent The Light-Independent

Reactions Reactions The Storage of Chemical EnergyThe Storage of Chemical Energy

Stage 3 Stage 3 of photosynthesis is known as of photosynthesis is known as thethe Calvin cycleCalvin cycle..

The Calvin cycle creates complex The Calvin cycle creates complex carbohydrates that store energy.carbohydrates that store energy.

Stage 3 of photosynthesis is also known as the Stage 3 of photosynthesis is also known as the ““light-independent reactionslight-independent reactions”” or “or “dark dark reactionsreactions” because these series of reactions do ” because these series of reactions do not need light to occur.not need light to occur.

Photosynthesis: Photosynthesis: The Light-Independent The Light-Independent

Reactions Reactions Stage 3 of photosynthesis is sometimes called Stage 3 of photosynthesis is sometimes called carbon dioxide fixation carbon dioxide fixation because ibecause in a series of enzyme-n a series of enzyme-

assisted chemical reactions within the chloroplastsassisted chemical reactions within the chloroplasts ,, CO CO2 2 molecules adhere to existing carbon compounds to molecules adhere to existing carbon compounds to form sugars for long-term energy storage. form sugars for long-term energy storage.

The energy used in the The energy used in the Calvin cycle is Calvin cycle is supplied by supplied by ATPATP and and NADPHNADPH that was made during Stage 2. that was made during Stage 2.

In a series of enzyme-assisted chemical reactions within the chloroplast called In a series of enzyme-assisted chemical reactions within the chloroplast called carbon dioxide fixationcarbon dioxide fixation,, CO CO2 2 molecules adhere to existing carbon compounds to form sugars for long-term energy storage. molecules adhere to existing carbon compounds to form sugars for long-term energy storage.

This process called the This process called the Calvin CycleCalvin Cycle uses the energy made in the 2uses the energy made in the 2ndnd stage of photosynthesis, and is often referred to as stage of photosynthesis, and is often referred to as dark reactionsdark reactions,, or or light independentlight independent reactions. reactions.

Three Factors That Affect Three Factors That Affect PhotosynthesisPhotosynthesis

1.) amount of light 1.) amount of light – – The rate of photosynthesis The rate of photosynthesis increases as light intensity increases until all the increases as light intensity increases until all the pigments are being used. At this saturation point, pigments are being used. At this saturation point, the reactions of the Calvin cycle cannot proceed the reactions of the Calvin cycle cannot proceed any faster.any faster.

2.) concentration of carbon dioxide 2.) concentration of carbon dioxide – – Once a Once a certain concentration of carbon dioxide is present, certain concentration of carbon dioxide is present, photosynthesis cannot proceed any faster.photosynthesis cannot proceed any faster.

3.) range of temperature 3.) range of temperature – – Like all metabolic Like all metabolic processes, photosynthesis involves many enzyme-processes, photosynthesis involves many enzyme-assisted chemical reactions. Unfavorable assisted chemical reactions. Unfavorable temperatures may inactivate certain enzymes.temperatures may inactivate certain enzymes.

SECTION SECTION 22Cellular Cellular

RespirationRespiration

Cellular RespirationCellular Respiration Before energy from food can be utilized, it Before energy from food can be utilized, it

must be transferred to must be transferred to ATPATP in a process called in a process called cellular respirationcellular respiration..

Cellular respiration Cellular respiration is the set of metabolic is the set of metabolic reactions and processes that take place in the reactions and processes that take place in the cells of organisms to convert biochemical cells of organisms to convert biochemical energy from nutrients into adenosine energy from nutrients into adenosine triphosphate (ATP), and then release waste triphosphate (ATP), and then release waste products.products.

To put it simply, To put it simply, cellular respiration cellular respiration is the is the process where cells produce energy from process where cells produce energy from carbohydrates.carbohydrates.

Cellular RespirationCellular Respiration Cellular respiration is the opposite of photosynthesis.Cellular respiration is the opposite of photosynthesis.

The reactants of photosynthesis – carbon dioxide The reactants of photosynthesis – carbon dioxide and water – are the products of cellular respiration.and water – are the products of cellular respiration.

The products of photosynthesis – glucose and The products of photosynthesis – glucose and oxygen – are the reactants of cellular respiration. oxygen – are the reactants of cellular respiration.

Cellular respiration releases much of the energy in Cellular respiration releases much of the energy in food to make food to make ATPATP. .

ATP provides cells with energy they need to carry ATP provides cells with energy they need to carry out the activities of life.out the activities of life.

Cells Transfer Energy Cells Transfer Energy From Food To ATPFrom Food To ATP

When cells break down food molecules, some When cells break down food molecules, some of the energy is released into the atmosphere of the energy is released into the atmosphere as as heatheat, while the rest is stored temporarily , while the rest is stored temporarily in molecules of in molecules of ATPATP..

Adenosine triphosphate Adenosine triphosphate ((ATPATP) is a ) is a nucleotidenucleotide with two extra energy-storing with two extra energy-storing phosphate groups. phosphate groups.

ATPATP molecules are often called the “ molecules are often called the “energy energy currencycurrency”” of a cell. of a cell.

REDRED = = riboseribose (a 5-carbon sugar) (a 5-carbon sugar)BLUEBLUE = = adenineadenine (a nitrogenous base) (a nitrogenous base)

GREEN = phosphate groupsGREEN = phosphate groups

Adenosine TriphosphateAdenosine Triphosphate

ATP Stores and ATP Stores and Releases EnergyReleases Energy

The energy from The energy from ATPATP is released when the is released when the bonds that hold the phosphate groups bonds that hold the phosphate groups together are broken.together are broken.

The removal of a phosphate group from The removal of a phosphate group from ATPATP (3 phosphates) produces (3 phosphates) produces ADPADP (adenosine (adenosine diphosphate -- 2 phosphates), which releases diphosphate -- 2 phosphates), which releases energy in a way that enables cells to use the energy in a way that enables cells to use the energy. energy.

Cells use energy released by this reaction to Cells use energy released by this reaction to power metabolism.power metabolism.

ATP FYI:ATP FYI:

The human body uses about 1 million The human body uses about 1 million molecules of ATP per second per cell.molecules of ATP per second per cell.

There are more than 100 trillion cells in There are more than 100 trillion cells in the human body.the human body.

That is about 1 X 10That is about 1 X 102020, or , or 100,000,000,000,000,000,000 ATP 100,000,000,000,000,000,000 ATP molecules used in the body each second.molecules used in the body each second.

Cellular respiration can be Cellular respiration can be aerobicaerobic respirationrespiration (with (with oxygen) or oxygen) or anaerobic anaerobic respiration respiration (without (without oxygen).oxygen).

Cellular respiration Cellular respiration begins begins in the in the cytoplasmcytoplasm, and ends , and ends in the in the mitochondriamitochondria..

Cellular respiration takes Cellular respiration takes place in the two stages of place in the two stages of glycolysisglycolysis, then , then aerobic aerobic respirationrespiration..

Cellular RespirationCellular Respiration

The chemical formula for The chemical formula for cellular respiration cellular respiration is:is:

CC66HH1212OO66 + 6 + 6OO22 + + ADPADP + + P P 6 6COCO22 + 6 + 6HH22OO + ATP + ATP

REACTANTS: REACTANTS: glucose glucose, , oxygen, oxygen, ADPADP,, extra phosphateextra phosphate

PRODUCTS: PRODUCTS: carbon dioxide, carbon dioxide, waterwater, , ATPATP

The process summarized by the equation begins in The process summarized by the equation begins in the the cytoplasm cytoplasm of a cell and ends in the of a cell and ends in the mitochondriamitochondria..

Cellular Respiration: Cellular Respiration: Stage Stage 1 1

GlycolysisGlycolysis Stage 1 Stage 1 of cellular respiration isof cellular respiration is called called

glycolysisglycolysis..

GlycolysisGlycolysis is the stage of cellular is the stage of cellular respiration where glucose is broken down respiration where glucose is broken down in the in the cytoplasmcytoplasm, converted to pyruvate, , converted to pyruvate, and produces a small amount of and produces a small amount of ATPATP and and NADPHNADPH..

GlycolysisGlycolysis – uses – uses 2 ATP2 ATP,, but produces but produces 4 4 ATPATP – net gain = – net gain = 2 ATP2 ATP

Cellular Respiration: Cellular Respiration: Stage Stage 22

The Krebs CycleThe Krebs Cycle Stage 2 Stage 2 of cellular respiration isof cellular respiration is known as known as

the the Krebs cycle Krebs cycle and is also called and is also called aerobic aerobic respirationrespiration..

Cellular respiration is called an aerobic Cellular respiration is called an aerobic process because it requires oxygen.process because it requires oxygen.

CC66HH1212OO66 + 6 + 6OO22 + + ADPADP + + P P 6 6COCO22 + 6 + 6HH22OO + ATP + ATP

A two-carbon molecule combines with a four-A two-carbon molecule combines with a four-carbon molecule during the Krebs cycle.carbon molecule during the Krebs cycle.

Cellular Respiration: Cellular Respiration: Stage Stage 22

The Krebs CycleThe Krebs Cycle Pyruvic acid produced during Pyruvic acid produced during

glycolysis enters the mitochondria and glycolysis enters the mitochondria and is converted into carbon dioxide and is converted into carbon dioxide and water.water.

ATP ATP andand NADPHNADPH are produced.are produced.

The The Krebs cycle Krebs cycle producesproduces 22 ATPATP for for each molecule ofeach molecule of glucoseglucose broken down.broken down.

Cellular Respiration: Cellular Respiration: The Electron Transport Chain The Electron Transport Chain

If enough If enough OO22 is present, up to is present, up to 3434 ATPATP molecules can be formed molecules can be formed from a single glucose molecule! from a single glucose molecule!

At the end of the electron At the end of the electron transport chain, oxygen (transport chain, oxygen (OO22) acts ) acts as the final electron acceptor as the final electron acceptor and combines with and combines with HH++ ions to ions to form water molecules (form water molecules (HH22OO).).

Fermentation:Fermentation:Occurs in the Absence of Occurs in the Absence of

OxygenOxygen

If oxygen (If oxygen (OO22) is not present in sufficient ) is not present in sufficient amounts, the amounts, the electron transport chainelectron transport chain in the in the mitochondrial membrane cannot function. mitochondrial membrane cannot function.

Energy molecules (Energy molecules (ATPATP and and NADHNADH) cannot be ) cannot be created in abundance.created in abundance.

So, what does the cell do to continue to break So, what does the cell do to continue to break down organic compounds and release energy if down organic compounds and release energy if not enough oxygen is present?not enough oxygen is present?

Fermentation:Fermentation:Occurs in the Absence of OxygenOccurs in the Absence of Oxygen

FermentationFermentation is the is the anaerobic process anaerobic process that that continues the breakdown of carbohydrates when continues the breakdown of carbohydrates when there is not enough oxygen for aerobic respiration. there is not enough oxygen for aerobic respiration.

There are two types of fermentation:There are two types of fermentation:

1.) 1.) lactic acid fermentation lactic acid fermentation and and 2.) 2.) alcoholic fermentationalcoholic fermentation..

Lactic acid Lactic acid and/or and/or ethanolethanol (alcohol) are the by- (alcohol) are the by-products of fermentation when the breakdown of products of fermentation when the breakdown of carbohydrates occurs without oxygen.carbohydrates occurs without oxygen.

Lactic Acid FermentationLactic Acid Fermentation Glycolysis occurs without oxygen. However, Glycolysis occurs without oxygen. However,

the Krebs cycle requires oxygen. In the Krebs cycle requires oxygen. In lactic acid lactic acid fermentationfermentation, , NADNAD++, an electron acceptor, is , an electron acceptor, is recycled and glycolysis can continue to produce recycled and glycolysis can continue to produce ATP.ATP.

Fermentation enables glycolysis to continue Fermentation enables glycolysis to continue producing ATP as long as the glucose supply producing ATP as long as the glucose supply lasts. lasts.

LactateLactate, an ion of lactic acid, can build up in , an ion of lactic acid, can build up in muscle cells if not removed quickly enough and muscle cells if not removed quickly enough and can cause “muscle burn” or muscle fatigue. can cause “muscle burn” or muscle fatigue.

Alcoholic FermentationAlcoholic Fermentation

Carbon dioxide is released during Carbon dioxide is released during alcoholic fermentation by yeast. alcoholic fermentation by yeast.

Carbon dioxide gas released by the Carbon dioxide gas released by the yeast is what causes the rising of yeast is what causes the rising of bread dough and the carbonation of bread dough and the carbonation of some alcoholic beverages.some alcoholic beverages.

Alcoholic FermentationAlcoholic Fermentation Alcoholic fermentation is a two-step process: First, Alcoholic fermentation is a two-step process: First,

pyruvate is converted, releasing carbon dioxide. pyruvate is converted, releasing carbon dioxide. Second, electrons are transferred from a molecule of Second, electrons are transferred from a molecule of NADH to the two-carbon compound, producing NADH to the two-carbon compound, producing ethanol.ethanol.

Alcoholic fermentation by yeast can be used to Alcoholic fermentation by yeast can be used to produce food and beverages such as yogurt, cheese, produce food and beverages such as yogurt, cheese, beer, and wine.beer, and wine.

Production of ATPProduction of ATP The total amount of The total amount of ATPATP a cell is able to a cell is able to

harvest from each glucose molecule that harvest from each glucose molecule that enters enters glycolysis glycolysis depends on the depends on the presence or presence or absence of oxygenabsence of oxygen..

When oxygen is present, When oxygen is present, aerobic aerobic respiration respiration occurs.occurs.

When oxygen is not present, When oxygen is not present, anaerobic anaerobic respirationrespiration, or , or fermentationfermentation,, occurs occurs instead.instead.

Production of ATPProduction of ATP Most Most ATPATP is made during aerobic respiration. is made during aerobic respiration.

GlycolysisGlycolysis (Stage 1 of cellular respiration) can (Stage 1 of cellular respiration) can occur with or without oxygen, and produces a occur with or without oxygen, and produces a net gain of net gain of 2 ATP 2 ATP molecules.molecules.

The The Krebs cycle Krebs cycle (Stage 2 of cellular (Stage 2 of cellular respiration) respiration) produces produces 22 ATPATP molecules for molecules for each glucose molecule broken down. each glucose molecule broken down.

The The electron transport chain electron transport chain can produce up can produce up to to 3434 ATPATP molecules from a single glucose molecules from a single glucose molecule.molecule.