Cell Energy (Photosynthesis and Respiration) Notes Energy: Energy for living things comes from food. Originally, the energy in food comes from the sun.

Organisms that use light energy from the sun to produce food—autotrophs (auto = self, troph = feed) Ex: plants and some microorganisms (some bacteria and protists)

Organisms that CANNOT use the sun’s energy to make food and must get their energy from consuming other organisms — heterotrophs Ex: animals and most microorganisms

AdenineRibose 3 Phosphate groups Cell Energy: Cells usable source of energy is called ATP ATP stands for adenosine triphosphate

BLUE = adenine (a nitrogenous base) RED = ribose (a 5-carbon sugar) GREEN = phosphate groups Adenosine Triphosphate

ADP stands for adenosine diphosphate AdenineRibose2 Phosphate groups

All energy is stored in the bonds of compounds— breaking the bond releases the energy When the cell has energy available it can store this energy by adding a phosphate group to ADP, producing ATP

ATP is converted into ADP by breaking the bond between the second and third phosphate groups and releasing energy for cellular processes.

Photosynthesis: Photosynthesis is the process by which the energy of sunlight is converted into the energy of glucose

Photosynthesis occurs in the chloroplasts of plants

Light absorbing compound is a pigment—pigments absorb some wavelengths of light and reflect others— the color our eyes see is the color that the pigment reflects

Chlorophyll is the pigment inside the chloroplast the absorbs light for photosynthesis As the chlorophyll in leaves decays in the autumn, the green color fades and is replaced by the oranges and reds of carotenoids.

General formula for photosynthesis : carbon dioxide + water + light glucose + oxygen 6CO 2 + 6H 2 O + light C 6 H 12 O 6 + 6O 2

Stages of Photosynthesis: STAGE 1 - The Light-Dependent Reactions STAGE 1: These reactions are called the “light reactions,” or “light-dependent reactions” because the reactions absorb light energy to make the organic compounds glucose and oxygen. STAGE 1: These reactions are called the “light reactions,” or “light-dependent reactions” because the reactions absorb light energy to make the organic compounds glucose and oxygen. STAGE 1 occurs in the chloroplasts on the thylakoid membrane where clusters of the pigment chlorophyll are embedded. STAGE 1 occurs in the chloroplasts on the thylakoid membrane where clusters of the pigment chlorophyll are embedded.

Photosynthesis: Where Does it Occur? Thylakoid membrane

Photosynthesis: Thylakoids Electrons in the pigments are “excited” by light, and jump from the chlorophyll molecules to other nearby molecules in the thylakoid membrane. Electrons in the pigments are “excited” by light, and jump from the chlorophyll molecules to other nearby molecules in the thylakoid membrane. The series of molecules along the thylakoid membrane that excited electrons pass through as they jump along the chlorophyll molecules is called the electron transport chain. The series of molecules along the thylakoid membrane that excited electrons pass through as they jump along the chlorophyll molecules is called the electron transport chain.

Photosynthesis: Stage 1 Absorption of Light Energy Absorption of Light Energy The excited electrons that leave chlorophyll molecules must be replaced by other electrons. The excited electrons that leave chlorophyll molecules must be replaced by other electrons. Plants get these replacement electrons from water molecules, H 2 0. Plants get these replacement electrons from water molecules, H 2 0. The water molecules are split by an enzyme inside the thylakoid. The water molecules are split by an enzyme inside the thylakoid. When water molecules are split, chlorophyll molecules take the electrons from the hydrogen atoms, H, leaving hydrogen ions, H +. When water molecules are split, chlorophyll molecules take the electrons from the hydrogen atoms, H, leaving hydrogen ions, H +. The remaining oxygen atoms, O, from the disassembled water molecules combine to form oxygen gas, O 2. The remaining oxygen atoms, O, from the disassembled water molecules combine to form oxygen gas, O 2.

Photosynthesis: Stage 2 Conversion of Light Energy by Conversion of Light Energy by Electron Transport Chains Excited electrons passing through the transport chain lose some of their energy which is used to pump the hydrogen ions into the thylakoid. Excited electrons passing through the transport chain lose some of their energy which is used to pump the hydrogen ions into the thylakoid. Hydrogen ions become more concentrated inside the thylakoid than outside, producing a concentration gradient across the thylakoid membrane. Hydrogen ions become more concentrated inside the thylakoid than outside, producing a concentration gradient across the thylakoid membrane.

Photosynthesis: Stage 2 As H+ diffuse through the channel portion of the protein, the protein catalyzes a reaction in which a phosphate group is added to ADP molecules to form ATP (ADP + P = ATP). As H+ diffuse through the channel portion of the protein, the protein catalyzes a reaction in which a phosphate group is added to ADP molecules to form ATP (ADP + P = ATP). Thus, the movement of hydrogen ions across the thylakoid membranes through proton pumps provide the energy to produce ATP molecules. Thus, the movement of hydrogen ions across the thylakoid membranes through proton pumps provide the energy to produce ATP molecules. inner thylakoid membrane outer thylakoid membrane

Two Electron Transport Chains The first electron transport chain is used to form ATP. The first electron transport chain is used to form ATP. In this second electron transport chain excited electrons combine with hydrogen ions (H + ) and an electron acceptor called NADP + to form NADPH. In this second electron transport chain excited electrons combine with hydrogen ions (H + ) and an electron acceptor called NADP + to form NADPH. NADPH is an electron carrier and is important in photosynthesis because it carries high energy electrons needed to produce organic molecules. NADPH is an electron carrier and is important in photosynthesis because it carries high energy electrons needed to produce organic molecules.

Photosynthesis: Stage 3 The Light-Independent Reactions The Storage of Chemical Energy  Stage 3 of photosynthesis is known as the Calvin cycle. The Calvin cycle creates complex carbohydrates that store energy. The Calvin cycle creates complex carbohydrates that store energy. Stage 3 of photosynthesis is also known as the “ light-independent reactions ” or “ dark reactions ” because these series of reactions do not need light to occur. Stage 3 of photosynthesis is also known as the “ light-independent reactions ” or “ dark reactions ” because these series of reactions do not need light to occur.

Photosynthesis: The Light-Independent Reactions Stage 3 of photosynthesis is sometimes called carbon dioxide fixation because in a series of enzyme-assisted chemical reactions within the chloroplasts, CO 2 molecules adhere to existing carbon compounds to form sugars for long-term energy storage. Stage 3 of photosynthesis is sometimes called carbon dioxide fixation because in a series of enzyme-assisted chemical reactions within the chloroplasts, CO 2 molecules adhere to existing carbon compounds to form sugars for long-term energy storage. The energy used in the Calvin cycle is supplied by ATP and NADPH that was made during Stage 2. The energy used in the Calvin cycle is supplied by ATP and NADPH that was made during Stage 2. In a series of enzyme-assisted chemical reactions within the chloroplast called carbon dioxide fixation, CO 2 molecules adhere to existing carbon compounds to form sugars for long-term energy storage. In a series of enzyme-assisted chemical reactions within the chloroplast called carbon dioxide fixation, CO 2 molecules adhere to existing carbon compounds to form sugars for long-term energy storage. This process called the Calvin Cycle uses the energy made in the 2 nd stage of photosynthesis, and is often referred to as dark reactions, or light independent reactions. This process called the Calvin Cycle uses the energy made in the 2 nd stage of photosynthesis, and is often referred to as dark reactions, or light independent reactions.

Three Factors That Affect Photosynthesis 1.) amount of light – The rate of photosynthesis increases as light intensity increases until all the pigments are being used. At this saturation point, the reactions of the Calvin cycle cannot proceed any faster. 1.) amount of light – The rate of photosynthesis increases as light intensity increases until all the pigments are being used. At this saturation point, the reactions of the Calvin cycle cannot proceed any faster. 2.) concentration of carbon dioxide – Once a certain concentration of carbon dioxide is present, photosynthesis cannot proceed any faster. 2.) concentration of carbon dioxide – Once a certain concentration of carbon dioxide is present, photosynthesis cannot proceed any faster. 3.) range of temperature – Like all metabolic processes, photosynthesis involves many enzyme- assisted chemical reactions. Unfavorable temperatures may inactivate certain enzymes. 3.) range of temperature – Like all metabolic processes, photosynthesis involves many enzyme- assisted chemical reactions. Unfavorable temperatures may inactivate certain enzymes.

Diagram Reactants Products Light H2OH2OCO 2 O2O2 C 6 H 12 O 6 Glucose Chloroplast Light Dependent Reaction Calvin Cycle NADP+ ADP + P ATP NADPH

Summary: Light Dependent Reaction—H 2 O is broken down and light energy is stored temporarily in inorganic energy carriers, ATP and NADPH Calvin Cycle—energy is transferred from ATP and NADPH to the organic compound glucose

ATP FYI: ATP FYI: The human body uses about 1 million molecules of ATP per second per cell. The human body uses about 1 million molecules of ATP per second per cell. There are more than 100 trillion cells in the human body. There are more than 100 trillion cells in the human body. That is about 1 X 10 20, or 100,000,000,000,000,000,000 ATP molecules used in the body each second. That is about 1 X 10 20, or 100,000,000,000,000,000,000 ATP molecules used in the body each second.

Cellular respiration can be aerobic respiration (with oxygen) or anaerobic respiration (without oxygen). Cellular respiration can be aerobic respiration (with oxygen) or anaerobic respiration (without oxygen). Cellular respiration begins in the cytoplasm, and ends in the mitochondria. Cellular respiration begins in the cytoplasm, and ends in the mitochondria. Cellular respiration takes place in the two stages of glycolysis, then aerobic respiration. Cellular respiration takes place in the two stages of glycolysis, then aerobic respiration.

Cellular Respiration The chemical formula for cellular respiration is: C 6 H 12 O 6 + 6O 2 + ADP + P  6CO 2 + 6H 2 O + ATP REACTANTS: glucose, oxygen, ADP, extra phosphate REACTANTS: glucose, oxygen, ADP, extra phosphate PRODUCTS: carbon dioxide, water, ATP PRODUCTS: carbon dioxide, water, ATP

Cellular Respiration: Stage 1 Glycolysis Stage 1 of cellular respiration is called glycolysis. Stage 1 of cellular respiration is called glycolysis. Glycolysis is the stage of cellular respiration where one glucose molecule is split into 2 pyruvate molecules, and produces 2 ATP and NADPH. Glycolysis is the stage of cellular respiration where one glucose molecule is split into 2 pyruvate molecules, and produces 2 ATP and NADPH. Glycolysis – uses 2 ATP, but produces 4 ATP – net gain = 2 ATP Glycolysis – uses 2 ATP, but produces 4 ATP – net gain = 2 ATP

Cellular Respiration: Stage 2 The Krebs Cycle Stage 2 of cellular respiration is known as the Krebs cycle and is also called aerobic respiration. Stage 2 of cellular respiration is known as the Krebs cycle and is also called aerobic respiration. C 6 H 12 O 6 + 6O 2 + ADP + P  6CO 2 + 6H 2 O + ATP C 6 H 12 O 6 + 6O 2 + ADP + P  6CO 2 + 6H 2 O + ATP

Cellular Respiration: Stage 2 The Krebs Cycle Pyruvic acid produced during glycolysis enters the mitochondria and is converted into carbon dioxide and water. Pyruvic acid produced during glycolysis enters the mitochondria and is converted into carbon dioxide and water. ATP and NADPH are produced. ATP and NADPH are produced. The Krebs cycle produces 2 ATP for each molecule of glucose broken down. The Krebs cycle produces 2 ATP for each molecule of glucose broken down.

Cellular Respiration: The Electron Transport Chain If enough O 2 is present, up to 34 ATP molecules can be formed from a single glucose molecule! If enough O 2 is present, up to 34 ATP molecules can be formed from a single glucose molecule! At the end of the electron transport chain, oxygen (O 2 ) acts as the final electron acceptor and combines with H + ions to form water molecules (H 2 O). At the end of the electron transport chain, oxygen (O 2 ) acts as the final electron acceptor and combines with H + ions to form water molecules (H 2 O).

Fermentation: Occurs in the Absence of Oxygen If oxygen (O 2 ) is not present in sufficient amounts, the electron transport chain in the mitochondrial membrane cannot function. If oxygen (O 2 ) is not present in sufficient amounts, the electron transport chain in the mitochondrial membrane cannot function. So, what does the cell do to continue to break down organic compounds and release energy if not enough oxygen is present? So, what does the cell do to continue to break down organic compounds and release energy if not enough oxygen is present?

Fermentation: Occurs in the Absence of Oxygen Fermentation is the anaerobic process that continues the breakdown of carbohydrates when there is not enough oxygen for aerobic respiration. Fermentation is the anaerobic process that continues the breakdown of carbohydrates when there is not enough oxygen for aerobic respiration. There are two types of fermentation: There are two types of fermentation: 1.) lactic acid fermentation and 1.) lactic acid fermentation and 2.) alcoholic fermentation. 2.) alcoholic fermentation. Lactic acid and/or ethanol (alcohol) are the by- products of fermentation when the breakdown of carbohydrates occurs without oxygen. Lactic acid and/or ethanol (alcohol) are the by- products of fermentation when the breakdown of carbohydrates occurs without oxygen.

Lactic Acid Fermentation  Glycolysis occurs without oxygen. In lactic acid fermentation, NAD +, an electron acceptor, is recycled and glycolysis can continue to produce ATP.  Fermentation enables glycolysis to continue producing ATP as long as the glucose supply lasts.  Lactate, an ion of lactic acid, can build up in muscle cells if not removed quickly enough and can cause “muscle burn” or muscle fatigue.

Alcoholic Fermentation  Alcoholic fermentation is a two-step process: First, pyruvate is converted, releasing carbon dioxide. Second, electrons are transferred from a molecule of NADH to the two-carbon compound, producing ethanol.  Alcoholic fermentation by yeast can be used to produce food and beverages such as yogurt, cheese, beer, and wine.

Production of ATP Most ATP is made during aerobic respiration. Most ATP is made during aerobic respiration. Glycolysis (Stage 1 of cellular respiration) can occur with or without oxygen, and produces a net gain of 2 ATP molecules. Glycolysis (Stage 1 of cellular respiration) can occur with or without oxygen, and produces a net gain of 2 ATP molecules. The Krebs cycle (Stage 2 of cellular respiration) produces 2 ATP molecules for each glucose molecule broken down. The Krebs cycle (Stage 2 of cellular respiration) produces 2 ATP molecules for each glucose molecule broken down. The electron transport chain can produce up to 34 ATP molecules from a single glucose molecule. The electron transport chain can produce up to 34 ATP molecules from a single glucose molecule.

Cellular Respiration: (2 kinds—Aerobic and Anaerobic) Cellular respiration is the process by which the energy of glucose is released in the cell to be used for life processes (movement, breathing, blood circulation, etc…)

Cells require a constant source of energy for life processes but keep only a small amount of ATP on hand. Cells can regenerate ATP as needed by using the energy stored in foods like glucose. The energy stored in glucose by photosynthesis is released by cellular respiration and repackaged into the energy of ATP.

Respiration occurs in ALL cells and can take place either with or without oxygen present.

Aerobic Respiration: requires oxygen Occurs in the mitochondria of the cell Total of 36 ATP molecules produced General formula for aerobic respiration: C 6 H 12 O 6 + 6O 2 6 CO 2 + 6H 2 O + 36 ATP glucose + oxygen carbon dioxide + water + energy Human cells contain a specialized structure – the mitochondrion – that generates energy.

Diagram Glucose Glycolysis Electron Transport Chain 2 Krebs Cycle Mitochondria In Cytoplasm 232 Electrons carried in NADH Electrons carried in NADH and FADH 2

Summary: 3 steps: 1 st glycolysis 2 nd Krebs cycle 3 rd Electron Transport Chain (ETC)

Anaerobic Respiration: occurs when no oxygen is available to the cell (2 kinds: Alcoholic and Lactic Acid) Also called fermentation Much less ATP produced than in aerobic respiration

Alcoholic fermentation—occurs in bacteria and yeast Process used in the baking and brewing industry—yeast produces CO 2 gas during fermentation to make dough rise and give bread its holes glucose ethyl alcohol + carbon dioxide + 2 ATP

Lactic acid fermentation—occurs in muscle cells Lactic acid is produced in the muscles during rapid exercise when the body cannot supply enough oxygen to the tissues—causes burning sensation in muscles glucose lactic acid + carbon dioxide + 2 ATP

glycolysis Anaerobic Respiration Alcoholic fermentation Bacteria, Yeast 2 ATP Lactic acid fermentation Muscle cells 2 ATP Aerobic Respiration 36 ATP ETC Mitochondria Krebs Cycle Cytoplasm First step in anaerobic respiration is also glycolysis Diagram C 6 H 12 O 6 glucose