Cellular Respiration: Obtaining Energy from Food CHAPTER 6 Cellular Respiration: Obtaining Energy from Food

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How does cellular respiration relate to you? When you exercise, Muscles need energy in order to perform work. Your cells use oxygen to release energy from the sugar glucose (C6H12O6).

Metabolism Aerobic metabolism Anaerobic metabolism Occurs when enough oxygen reaches cells to support energy needs. Anaerobic metabolism Occurs when the demand for oxygen outstrips the body’s ability to deliver it.

Metabolism Anaerobic metabolism Without enough oxygen, muscle cells break down glucose to produce lactic acid. Lactic acid is associated with the “burn” associated with heavy exercise. If too much lactic acid builds up, your muscles give out.

How does cellular respiration relate to you? Physical conditioning allows your body to adapt to increased activity. The body can increase its ability to deliver oxygen to muscles. Long-distance runners wait until the final sprint to exceed their aerobic capacity.

Energy Flow and Chemical Cycling in the Biosphere Fuel molecules in food represent solar energy. Energy stored in food can be traced back to the sun. Animals depend on plants to convert solar energy to chemical energy. This chemical energy is in the form of sugars and other organic molecules.

Producers and Consumers Photosynthesis Uses light energy from the sun to power a chemical process that makes organic molecules. Occurs in the leaves of terrestrial plants.

Producers and Consumers Autotrophs Are “self-feeders”. Include plants and other organisms that make all their own organic matter from inorganic nutrients. Heterotrophs Are “other-feeders.” Include humans and other animals that cannot make organic molecules from inorganic ones.

Producers and Consumers Biologists refer to plants and other autotrophs as the producers in an ecosystem. Consumers Heterotrophs are consumers, because they eat plants or other animals.

What is Cellular Respiration? The release of chemical energy for use by cells in the form of ATP. It occurs in ALL living things. Once the energy that was in sunlight is changed into chemical energy by photosynthesis, an organism has to transform the chemical energy into a form that can be used by the organism. This process is cellular respiration.

Chemical Cycling between Photosynthesis and Cellular Respiration The ingredients for photosynthesis are carbon dioxide and water. CO2 is obtained from the air by a plant’s leaves. H2O is obtained from the damp soil by a plant’s roots. Chloroplasts rearrange the atoms of these ingredients to produce sugars (glucose) and other organic molecules. Oxygen gas is a by-product of photosynthesis. of photosynthesis .

Both plants and animals perform cellular respiration!! Cellular respiration is a chemical process that harvests energy from organic molecules. Cellular respiration occurs in mitochondria. The waste products of cellular respiration, CO2 and H2O, are used in photosynthesis. of photosynthesis .

Cellular Respiration: The Aerobic Harvest of Food Energy Is the main way that chemical energy is harvested from food and converted to ATP. Is an aerobic process—it requires oxygen.

The Relationship between Cellular Respiration and Breathing Cellular respiration and breathing are closely related but they are NOT the same! Cellular respiration requires a cell to exchange gases with its surroundings. Breathing exchanges these gases between the blood and outside air.

The Overall Equation for Cellular Respiration A common fuel molecule for cellular respiration is glucose. The overall equation for what happens to glucose during cellular respiration MEMORIZE!!

The Role of Oxygen in Cellular Respiration During cellular respiration, hydrogen and its bonding electrons change partners. Hydrogen and its electrons go from sugar to oxygen, forming water. Chemical reactions that transfer electrons from one substance to another are called oxidation-reduction reactions, or redox reactions for short.

Redox Reactions The loss of electrons during a redox reaction is called oxidation. The acceptance of electrons during a redox reaction is called reduction.

Why does electron transfer to oxygen release energy? The Release of Energy Why does electron transfer to oxygen release energy? When electrons move from glucose to oxygen, it is as though they were falling. This “fall” of electrons releases energy during cellular respiration.

NADH and Electron Transport Chains The path that electrons take on their way down from glucose to oxygen involves many steps.

NADH and Electron Transport Chains The first step is an electron acceptor called NAD+. The transfer of electrons from organic fuel to NAD+ reduces it to NADH. The rest of the path consists of an electron transport chain. This chain involves a series of redox reactions. These lead ultimately to the production of large amounts of ATP (34-36!).

The Metabolic Pathway of Cellular Respiration Cellular respiration is an example of a metabolic pathway, A series of chemical reactions in cells. All of the reactions involved in cellular respiration can be grouped into three main stages: Glycolysis The citric acid cycle (The Krebs Cycle) Electron transport

A Road Map for Cellular Respiration The path of glucose through cellular respiration

Stage 1: Glycolysis A molecule of glucose is split into two molecules of pyruvic acid. In other words glycolysis breaks a six-carbon glucose into two three-carbon molecules. These molecules then donate high energy electrons to NAD+, forming NADH.

Stage 1: Glycolysis Glycolysis makes some ATP directly when enzymes transfer phosphate groups from fuel molecules to ADP. Note that 2 ATP used to start Glycolysis so while Glycolysis produces 4 ATP only 2 are really gained.

Stage 2: The Citric Acid Cycle (Krebs Cycle) The citric acid cycle completes the breakdown of sugar. In the citric acid cycle, pyruvic acid from glycolysis is first “prepped” into a usable form, Acetyl CoA. of photosynthesis .

Stage 2: The Citric Acid Cycle (Krebs Cycle) The citric acid cycle extracts the energy of sugar by breaking the acetic acid molecules all the way down to CO2. The cycle uses some of this energy to make ATP. 2 ATP are produced. The cycle also forms NADH and FADH2.

Stage 2: The Citric Acid Cycle (Krebs Cycle) of photosynthesis .

Stage 3: Electron Transport Electron transport releases the energy your cells need to make most of their ATP. The molecules of electron transport chains are built into the inner membranes of mitochondria, called cristae. The chain functions as a chemical machine that uses energy released by the “fall” of electrons to pump hydrogen ions across the inner mitochondrial membrane. These ions store potential energy.

Stage 3: Electron Transport When the hydrogen ions flow back through the membrane, they release energy. The ions flow through ATP synthase (an enzyme). ATP synthase takes the energy from this flow, and synthesizes ATP. (32-34!) of photosynthesis .

The Versatility of Cellular Respiration Cellular respiration can “burn” other kinds of molecules besides glucose: Diverse types of carbohydrates Fats Proteins

Cellular Respiration Overview

Adding Up the ATP from Cellular Respiration A summary of ATP yield during cellular respiration of photosynthesis .

Respiration of photosynthesis . CYTOPLASM GLYCOLOSIS HAPPENS HERE! PROTEINS CARBO’S (SUGARS) FATS (LIPIDS) GLUCOSE C6H12O6 AMINO ACIDS MAKES 2 ATPS GLYCOLOSIS IN CYTOPLASM NO OXYGEN! ATP TOTALS GLYCOLOSIS=2 RESPIRATION=36 BOTH=38! PYRUVIC ACID CO2 IS RELEASED ACETYL-CoA O2 ENTERS HERE of photosynthesis . KREBS CYCLE AND ELECTRON TANSPORT MAKES 34 ATPS MITOCHONDRIA RESPIRATION HAPPENS IN THIS ORGANELLE!

Fermentation: Anaerobic Harvest of Food Energy Some of your cells can actually work for short periods without oxygen. A process that does not use oxygen is called anaerobic. Fermentation Is the anaerobic harvest of food energy.

Fermentation in Human Muscle Cells After functioning anaerobically for about 15 seconds, Muscle cells will begin to generate ATP by the process of fermentation. Fermentation relies on glycolysis to produce ATP.

Fermentation in Human Muscle Cells Glycolysis is the metabolic pathway that provides ATP during fermentation. Pyruvic acid is reduced by NADH, producing NAD+, which keeps glycolysis going. In human muscle cells, lactic acid is a by-product. This is known as lactic acid fermentation. Fermentation Overview

Fermentation in Microorganisms Various types of microorganisms perform fermentation. Yeast cells carry out a slightly different type of fermentation pathway. This pathway produces CO2 and ethyl alcohol. This is known as alcoholic fermentation.

A Comparison of Fermentation Types

A Comparison of Fermentation to Respiration 2 ATP 2 ATP 36-38 ATP

Fermentation in Industry The food industry uses yeast to produce various food products. We will be making root beer! mmmmmmMMMmmmm!

Evolution Connection: Life on an Anaerobic Earth Ancient bacteria probably used glycolysis to make ATP long before oxygen was present in Earth’s atmosphere. Glycolysis is a metabolic heirloom from the earliest cells that continues to function today in the harvest of food energy.

Photosynthesis: Using Light to Make Food CHAPTER 7 Photosynthesis: Using Light to Make Food

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Overview of Photosynthesis and Respiration SUN RADIANT ENERGY CELL ACTIVITIES PHOTOSYNTHESIS RESPIRATION GLUCOSE ATP (ENERGY)

What is Photosynthesis? The process of photosynthesis is a chemical reaction. It is the most important chemical reaction on our planet. Tell me… WHY?

Biology and Society: Plant Power for Power Plants On a global scale the productivity of photosynthesis is astounding. All of the food consumed by humans can be traced back to photosynthetic organisms. An “energy plantation” Is a renewable energy source.

The Basics of Photosynthesis Almost all plants are photosynthetic autotrophs, as are some bacteria and protists. They generate their own organic matter through photosynthesis. Cyanobacteria (Oscillatoria)

Chloroplasts: Sites of Photosynthesis Occurs in chloroplasts. Chloroplasts Are found in the interior cells of leaves. Contain stroma, a thick fluid. Contain thylakoids, membranous sacs.

Chloroplasts: Sites of Photosynthesis Figure 7.3

The Overall Equation for Photosynthesis The reactants and products of the reaction MEMORIZE!!

Photosynthesis and Electrons In photosynthesis, Energized electrons are added to carbon dioxide to make sugar. Sunlight provides the energy. Note that not all electrons contain the same amount of energy. Some are low energy and some are high energy (energized). The ability of electrons to gain or lose energy is needed for all living things to survive!

Photosynthesis and Electrons The electron gains energy by absorbing photons. Once it gains enough it will leaves the chlorophyll molecule. The electron is now described as a “high-energy electron” and can provide energy for the formation of molecules of ATP. Remember: If an electron gains energy it moves to an outer shell; if the electron gains enough energy, the electron may be driven out of the atom. If an electron loses energy it moves to an inner shell (i.e., closer to the nucleus of the atom).

A Photosynthesis Road Map Photosynthesis is composed of two processes: The light reactions convert solar energy to chemical energy. The dark reactions, also known as the light independent reactions or The Calvin Cycle, make sugar from carbon dioxide.

Converting Solar Energy to Chemical Energy The Light Reactions: Converting Solar Energy to Chemical Energy Chloroplasts are chemical factories powered by the sun That convert solar energy into chemical energy. Produces two high energy molecules NADP-H ATP

Sunlight is a type of energy called radiation The Nature of Sunlight Sunlight is a type of energy called radiation Or electromagnetic energy. Packets of light energy are called photons. The full range of radiation is called the electro-magnetic spectrum. Shorter wavelengths have more energy than longer wavelengths. When you see color, you are seeing the reflection of that wavelength.

The Nature of Sunlight Figure 7.5

Sunlight and Photosynthesis Chloroplasts absorb select wavelengths of light that drive photosynthesis. Light and Pigments

Chloroplasts contain several pigments: Chloroplast Pigments Chloroplasts contain several pigments: Chlorophyll a Chlorophyll b Carotenoids

Summary of How Photosystems Harvest Light Energy Light behaves as photons, discrete packets of energy. Chlorophyll molecules absorb photons. Electrons in the pigment gain energy. The energy is released and used.

How Photosystems Harvest Light Energy Details! A photosystem: Is an organized group of chlorophyll and other molecules that are used as a light-gathering antenna. When chlorphyll absorbs light electrons gain energy. The two photosystems: Photosystem I - High energy electrons contained here are used to manufacture molecules of NADP-H. Photosystem II - High energy electrons here are used to manufacture molecules of ATP.

How Photosystems Harvest Light Energy Figure 7.10

How the Light Reactions Generate ATP and NADPH The light reactions of photosynthesis

Photosystems I & II Two types of photosystems cooperate in the light reactions.

An electron transport chain Photosystems I & II An electron transport chain Connects the two photosystems. Releases energy that the chloroplast uses to make ATP.

The light reactions in the thylakoid membrane Photosystems I & II The light reactions in the thylakoid membrane Light Reactions

The Calvin Cycle (dark reactions) Making Sugar from Carbon Dioxide The Calvin cycle Functions like a sugar factory within the stroma of a chloroplast. Regenerates the starting material with each turn.

The Calvin Cycle (dark reactions) The Calvin cycle requires the input of carbon dioxide (as a source of carbon for building carbohydrates) The availability of ATP and NADP-H to provide energy to reduce the carbon dioxides and construct high-energy carbohydrates such as sugar.

The Calvin Cycle (dark reactions) A 3-carbon product of the Calvin cycle is phosphoglyceraldehyde (which is also called glyceraldehyde phosphate) and is commonly symbolized as PGAL or G3P in your text. Two of these will form glucose, the others will be recycled to use again in this cycle. Note: For each carbon atom that is released from the Calvin cycle in a high-energy carbohydrate molecule, one low energy carbon dioxide molecule must enter the cycle. Calvin Cycle

Water-Saving Adaptations Three types of photosynthesis: C3, C4 and CAM photosynthesis C3 plants Use CO2 directly from the air. Are very common and widely distributed.

Water-Saving Adaptations C4 plants Close their stomata to save water during hot and dry weather. Can still carry out photosynthesis. CAM plants Open their stomata only at night to conserve water.

The Environmental Impact of Photosynthesis A review of photosynthesis Photosynthesis has an enormous impact on the atmosphere. It swaps O2 for CO2.

How Photosynthesis Moderates Climate Change Greenhouses used to grow plant indoors Trap sunlight that warms the air inside.

How Photosynthesis Moderates Climate Change A similar process, the greenhouse effect, Warms the atmosphere. Is caused by greenhouse gases such as atmospheric CO2, methane and others.

How Photosynthesis Moderates Climate Change Greenhouse gases are the most likely cause of global warming, a slow but steady rise in the Earth’s surface temperature. Destruction of forests may be increasing this effect.

Evolution Connection:The Oxygen Revolution The atmospheric oxygen we breathe is a by-product of photosynthesis. Cyanobacteria were the first organisms to carry out photosynthesis. The production of oxygen changed the Earth forever. The “oxygen revolution” was a major episode in the history of life on Earth.

Compare and Contrast Photosynthesis & Cellular Respiration

Photosynthesis & Cellular Respiration are Interconnected

The End