Chapter 4 Cells and Energy

Cell Energy All living organisms must be able to obtain energy from the environment in which they live. Plants and other green organisms are able to trap the light energy in sunlight and store it in the bonds of certain molecules for later use. Other organisms cannot use sunlight directly. They eat green plants. In that way, they obtain the energy stored in plants.

Cell Energy Uses: Active transport, cell division, movement of flagella or cilia, and the production, transport, and storage of proteins are some examples of cell processes that require energy.

Cells use energy to do required work Such as Movement -cells can swim (flagellum) -cells can change their shape -cells crawl over one another & reach new positions in the embryo 2. To build new Molecules - most are manufactured by a series of enzyme-catalyzed chemical reactions

Energy from foods Does food, containing sugar and carbon-based molecules give you energy? Carbohydrates and Lipids are the most important energy sources in foods you eat HOWEVER… this energy is only useable after being broken down by a series of chemical reactions All cells use chemical energy carried by ATP – adenosine triphosphate.

triphosphate adenosine diphosphate tri=3 di=2

ATP Adenosine triphosphate (ATP) is a molecule that transfer energy from the breakdown of food molecules to cell processes ATP carries chemical energy that cells can use for functions like 1. building molecules 2. Moving materials by active transport

ATP  ADP The energy carried by ATP is released when a phosphate group is removed. ATP  ADP + P ATP has 3 phosphate groups – but the bond holding the 3rd group of phosphates is unstable and broken easily The removal of the 3rd energy group involves a reaction that releases energy When the phosphate is removed, energy is released and ATP becomes ADP

ADP ADP – Adenosine Diphosphate – is a lower energy molecule that can be converted into ATP by adding a Phosphate group. If another phosphate is added to ADP  it becomes ATP again and is high energy The energy that comes from breaking down food is used to convert ADP  ATP These reactions become a cycle

Energy is released when a phosphate group is removed. ATP transfers energy from the breakdown of food molecules to cell functions. Energy is released when a phosphate group is removed. ADP is changed into ATP when a phosphate group is added. phosphate removed

Carbon-based molecules to produce ATP All Cells need chemical energy  ATP carries energy The foods you eat do not contain ATP that your cells can use The food must be digested 1st Then broken down into smaller molecules like: carbohydrates, lipids, and proteins Your cells can use these to make ATP

Carbohydrates are used for ATP 1. Carbohydrates are not stored in large amounts in your body 2. They are the molecules most commonly broken down to make ATP The breakdown of the simple sugar GLUCOSE yields about 36 molecules of ATP

So how much ATP is produced anyway? The amount of ATP depends on the type of molecule broken down 1. Simple Sugar: Glucose: produces 36 molecules. Do not provide the LARGEST amounts of ATP 2. Fat: Triglycerides: produces about 146 molecules-80%. When broken down they yield the most ATP 3. Protein produces 36 molecules: same as carbohydrates:(not used for energy) instead amino acids that can be used to make ATP are used to build more proteins

Fats store the most energy. 80 percent of the energy in your body about 146 ATP from a triglyceride Proteins are least likely to be broken down to make ATP. amino acids not usually needed for energy about the same amount of energy as a carbohydrate

Chemosynthesis Chemo – means chemical Synthesis – means making something though a chemical process Chemosynthesis: is the process that some organisms use chemical energy to make energy storing carbon based molecules. Some organisms live in places that never get sunlight. Live in very hot water near cracks in the ocean floor called hydrothermal vents These vents release sulfides which serve as the energy source similar to photosynthesis uses chemical energy instead of light energy

Energy is Carried by Electrons Energy can be extracted from chemical bonds in food you eat Energy in food is actually stored in the shared electrons of carbon-to-hydrogen bonds These electrons are portable & can be transferred to new chemical bonds by Oxidation-Reduction Reactions

Oxidation-Reduction Oxidation: is the loss of electrons Reduction: is the gain of electrons In organisms, electrons usually are NOT TRANSFERRED Alone Each electron moves with a proton as part of a hydrogen atom, H The transfer of energy in organisms usually involves the REMOVAL of H atoms from one molecule and the ADDITION of H atoms to another molecule

C6H12O6 + 6O2  6CO2 + 6 H20 C6H12O6 is oxidized when it loses H atoms O2 is reduced when it gains H atoms Oxidation-Reduction always take place together because every electron that is lost by one atom or molecule is gained by another C6H12O6 + 6O2  6CO2 + 6 H20

The chemical reaction… Chemical reactions that pass electrons from one atom or molecule to another are Oxidation-Reduction Reactions

Coenzymes help transport Energy High energy electrons are passed from the active site of the enzyme that is catalyzing a reaction to an organic molecule called a coenzyme The coenzyme carries the e- to another enzyme that is catalyzing a different reaction Coenzymes shuttle energy from one place to another

1 of the most important coenzymes Is Nicotinamide Adenine Dinucleotide (NAD+) When NAD+ gains a H+ atom from the active site, it becomes NADH NAD+  NADH It has been reduced Other Coenzymes: FAD+ a coenzyme that functions in the redox reaction of photosynthesis. It is reduced to FADH2

OBTAINING ENERGY Organisms can be classified according to how they get energy Organisms that use energy from sunlight are called Autotrophs or Producers Producers make their own source of chemical energy from the sun.

OBTAINING ENERGY Animals and other organisms that must get energy from food instead of directly from sunlight or inorganic substances are called heterotrophs or consumers.

Overview of photosynthesis

Photosynthetic organisms are producers. Most autotrophs use the process of photosynthesis to convert light energy from the sun into chemical energy in the form of organic compounds through a series of reactions known as biochemical pathways Photosynthesis captures energy from sunlight to make sugars for plants.

Equation of Photosynthesis 6CO2 + 6H2O light energy C6H12O6 + 6O2 C6H12O6 granum (stack of thylakoids) thylakoid sunlight 1 six-carbon sugar 6H2O 6CO2 6O2 chloroplast 1 2 4 3 energy stroma (fluid outside the thylakoids)

Photosynthesis occurs in the Chloroplast The Photosynthesis begins with the absorption of light in chloroplasts, organelles found in the cells of plants, some bacteria, and algae Chloroplast are membrane bound organelles where photosynthesis takes place in plants Most of the chloroplast in leaf cells are specialized for photosynthesis

Two main parts of the chloroplast needed for photosynthesis 1. grana (granum): stacks of Thylakoids 2. stroma: fluid outside the chloroplast stroma grana (thylakoids)

In plants, chlorophyll is found in organelles called chloroplasts. Chlorophyll is a molecule in chloroplast that absorbs some energy in visible light. In plants, chlorophyll is found in organelles called chloroplasts. Located in the membrane of the thylakoids of chloroplasts are several pigments, including chlorophylls and carotenoids. Two types of chlorophyll: 1. Chlorophyll a 2. Chlorophyll b chloroplast leaf cell leaf

Chlorophyll a & Chlorophyll b Together, Chlorophyll a & Chlorophyll b absorb mostly red and blue wavelengths of visible light Neither absorb much green light – green color of plants comes from the reflection of lights’ green wavelengths by chlorophyll Carotenoids: rich colors such as red, orange, and yellow

Overview of Photosynthesis Photosynthesis can be divided into two stages: 1. Light Dependent Reactions In the light reactions, light energy is converted to chemical energy, which is temporarily stored in ATP and the energy carrier molecule NADPH. 2. Dark Independent Reactions or the Calvin Cycle In the Calvin Cycle, organic compounds are formed using CO2 and the chemical energy stored in ATP and NADPH.

The first stage of photosynthesis captures and transfers energy. The light-dependent reactions include groups of molecules called photosystems.

Photosystems: To trap the energy in the sun’s light, the thylakoid membranes contain pigments, molecules that absorb specific wavelengths of sunlight. Although a photosystem contains several kinds of pigments, the most common is chlorophyll Chlorophyll absorbs most wavelengths of light except green

The light-dependent reactions capture energy from sunlight. take place in thylakoids water and sunlight are needed chlorophyll absorbs energy energy is transferred along thylakoid membrane then to light-independent reactions oxygen is released

Light-Dependent Reactions As sunlight strikes the chlorophyll molecules in a photosystem of the thylakoid membrane, the energy in the light is transferred to electrons. These highly energized, or excited, electrons are passed from chlorophyll to an electron transport chain, a series of proteins embedded in the thylakoid membrane. At each step along the transport chain, the electrons lose energy.

Photosystem II captures and transfers energy. chlorophyll absorbs energy from sunlight energized electrons enter electron transport chain water molecules are split oxygen is released as waste hydrogen ions are transported across thylakoid membrane

Photosystem I captures energy and produces energy-carrying molecules. chlorophyll absorbs energy from sunlight energized electrons are used to make NADPH NADPH is transferred to light-independent reactions

Converting Light Energy To Chemical Energy, continued The Light Reactions Converting Light Energy To Chemical Energy, continued Replacing Electrons in Light Reactions Electrons from photosystem II replace electrons that leave photosystem I. Replacement electrons for photosystem II are provided by the splitting of water molecules. Oxygen produced when water molecules are split diffuses out of the chloroplast and then leaves the plant.

Converting Light Energy To Chemical Energy, continued The Light Reactions Converting Light Energy To Chemical Energy, continued Making ATP in Light Reactions An important part of the light reactions is the synthesis of ATP. During chemiosmosis, the movement of protons through ATP synthase into the stroma releases energy, which is used to produce ATP.

The Light Reactions

The Calvin Cycle The light-independent reactions make sugars. take place in stroma needs carbon dioxide from atmosphere use energy to build a sugar in a cycle of chemical reactions

Carbon Fixation The ATP and NADPH produced in the light reactions drive the second stage of photosynthesis, the Calvin cycle. In the Calvin cycle, CO2 is incorporated into organic compounds, a process called carbon fixation.

How it works! Most of the three-carbon sugars (G3P) generated in the Calvin cycle are converted to a five-carbon sugar (RuBP) to keep the Calvin cycle operating. But some of the three-carbon sugars leave the Calvin cycle and are used to make organic compounds, in which energy is stored for later use.

The Calvin Cycle Video Clip

A molecule of glucose is formed as it stores some of the energy captured from sunlight. carbon dioxide molecules enter the Calvin cycle energy is added and carbon molecules are rearranged a high-energy three-carbon molecule leaves the cycle

Total Three turns of the Calvin cycle use 9 molecules of ATP & 6 molecules of NADPH

Cellular Respiration

Cycle between Photosynthesis and Cellular Respiration The oxygen (O2) and some of the organic compounds produced by photosynthesis are used by cells in cellular respiration.

Cellular respiration makes ATP by breaking down sugars. Cellular respiration is aerobic, or requires oxygen. Aerobic stages take place in mitochondria. mitochondrion animal cell

Cellular Respiration The process by which mitochondria break down food molecules to produce ATP is called cellular respiration. There are three stages of cellular respiration: 1. glycolysis 2. the citric acid cycle or Kreb Cycle 3. the electron transport chain.

Cellular Respiration The first stage, glycolysis, is anaerobic—no oxygen is required. The last two stages are aerobic and require oxygen to be completed.

The equation for the overall process is: C6H12O6 + 6O2  6CO2 + 6H2O The reactants in photosynthesis are the same as the products of cellular respiration.

Glycolysis Glycolysis is a series of chemical reactions in the cytoplasm of a cell that break down glucose, a six-carbon compound, into two molecules of pyruvic acid, a three-carbon compound. 4ATP 2ADP 2 Pyruvic acid 2ATP 4ADP + 4P Glucose 2PGAL 2NAD+ 2NADH + 2H+

anaerobic process (does not require oxygen) takes place in cytoplasm Glycolysis must take place first. Inserts 2 ATP to Start Reaction anaerobic process (does not require oxygen) takes place in cytoplasm

Glycolysis is needed for cellular respiration. The products of glycolysis enter cellular respiration when oxygen is available. 2 ATP molecules are used to split glucose (used) 4 ATP molecules are produced 2 molecules of NADH produced 2 molecules of pyruvate produced

Glycolysis 4ATP 2ADP 2 Pyruvic acid 2ATP 4ADP + 4P Glucose 2PGAL 2NAD+ 2NADH + 2H+

Glycolysis Before citric acid cycle and electron transport chain can begin, pyruvic acid undergoes a series of reactions in which it gives off a molecule of CO2 and combines with a molecule called coenzyme A to form acetyl-CoA. Mitochondrial membrane CO2 Outside the mitochondrion Inside the mitochondrion Coenzyme A - CoA Pyruvic acid Pyruvic acid Intermediate by-product Acetyl-CoA NAD+ NADH + H+

The citric acid cycle The citric acid cycle, also called the Krebs cycle, is a series of chemical reactions similar to the Calvin cycle in that the molecule used in the first reaction is also one of the end products. For every turn of the cycle, 1 molecule of ATP and 2 molecules of carbon dioxide are produced.

The Krebs cycle is the first main part of cellular respiration. Pyruvate is broken down before the Krebs cycle. carbon dioxide released NADH produced coenzyme A (CoA) bonds to two-carbon molecule

The Krebs cycle produces energy-carrying molecules.

The Krebs cycle produces energy-carrying molecules. NADH and FADH2 are made intermediate molecule with CoA enters Krebs cycle citric acid (six-carbon molecule) is formed citric acid is broken down, carbon dioxide is released, and NADH is made five-carbon molecule is broken down, carbon dioxide is released, NADH and ATP are made four-carbon molecule is rearranged

The Citric Acid/ Kreb Cycle Video

energy from glycolysis The Krebs cycle transfers energy to an Electron Transport Chain. Kreb Cycle takes place in mitochondrial matrix breaks down three-carbon molecules from glycolysis 6H O 2 6CO 6O mitochondrion matrix (area enclosed by inner membrane) inner membrane ATP energy energy from glycolysis 1 4 3 and Krebs Cycle makes a small amount of ATP releases carbon dioxide transfers energy-carrying molecules

energy from glycolysis ELECTRON TRANSPORT CHAIN takes place inner membrane energy transferred to electron transport chain oxygen enters process ATP produced 6H O 2 6CO 6O mitochondrion matrix (area enclosed by inner membrane) inner membrane ATP energy energy from glycolysis 1 4 3 and Electron Transport water released as a waste product

The electron transport chain In the electron transport chain, the carrier molecules NADH and FADH2 gives up electrons that pass through a series of reactions. Oxygen is the final electron acceptor. Overall, the electron transport chain adds 32 ATP molecules to the four already produced. For every NADH released – 3 ATP For every FADH2 released – 2 ATP

The electron transport chain is the second main part of cellular respiration. The electron transport chain uses NADH and FADH2 to make ATP. high-energy electrons enter electron transport chain energy is used to transport hydrogen ions across the inner membrane hydrogen ions flow through a channel in the membrane

The electron transport chain is the second main part of cellular respiration. The electron transport chain uses NADH and FADH2 to make ATP. The breakdown of one glucose molecule produces up to 38 molecules of ATP. ATP synthase produces ATP oxygen picks up electrons and hydrogen ions water is released as a waste product

The electron transport chain Video

Fermentation During heavy exercise, when your cells are without oxygen for a short period of time, an anaerobic process called fermentation follows glycolysis and provides a means to continue producing ATP until oxygen is available again.

Fermentation allows glycolysis to continue. Fermentation allows glycolysis to continue making ATP when oxygen is unavailable. Fermentation is an anaerobic process. occurs when oxygen is not available for cellular respiration does not produce ATP

Fermentation allows glycolysis to continue making ATP when oxygen is unavailable. NAD+ is recycled to glycolysis Lactic acid fermentation occurs in muscle cells. glycolysis splits glucose into two pyruvate molecules pyruvate and NADH enter fermentation energy from NADH converts pyruvate into lactic acid NADH is changed back into NAD+

Glucose 2 ATP 2 ATP Glycolysis 2 NADH Pyruvate 6 ATP 2 NADH 6 ATP Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Glucose 2 ATP 2 ATP Glycolysis 2 NADH Pyruvate 6 ATP 2 NADH 6 ATP Acetyl-CoA 2 ATP Krebs cycle 6 NADH 18 ATP 2 FADH2 4 ATP Total net ATP yield = 38 ATP

Fermentation is used in food production. yogurt cheese bread

Lactic acid fermentation Lactic acid fermentation is one of the processes that supplies energy when oxygen is scarce. In this process, the reactions that produced pyruvic acid are reversed. Two molecules of pyruvic acid use NADH to form two molecules of lactic acid.

Lactic acid fermentation This releases NAD+ to be used in glycolysis, allowing two ATP molecules to be formed for each glucose molecule. The lactic acid is transferred from muscle cells, to the liver that converts it back to pyruvic acid.

Alcoholic fermentation Another type of fermentation, alcoholic fermentation, is used by yeast cells and some bacteria to produce CO2 and ethyl alcohol.

Fermentation and its products are important in several ways. Alcoholic fermentation is similar to lactic acid fermentation. glycolysis splits glucose and the products enter fermentation energy from NADH is used to split pyruvate into an alcohol and carbon dioxide NADH is changed back into NAD+ NAD+ is recycled to glycolysis

Comparing Photosynthesis and Cellular Respiration Table 9.1 Comparison of Photosynthesis and Cellular Respiration Photosynthesis Cellular Respiration Food synthesized Food broken down Energy from sun stored in glucose Energy of glucose released Carbon dioxide taken in Carbon dioxide given off Oxygen given off Oxygen taken in Produces sugars from PGAL Produces CO2 and H2O Requires light Does not require light Occurs only in presence of chlorophyll Occurs in all living cells