Unit 4: BIOENERGETICS Part 2: Cellular Respiration Mrs. Howland Biology 10 Rev. Oct 2015

Energy and Life How do cells and living organisms maintain life? REMEMBER: Energy is the ability to do work AUTOTROPHS make their own food HETEROTROPHS Eat plants Eat other plant-eating animals Absorb nutrients from decomposing organisms (fungi, such as mushrooms)

Biochemical Pathways Photosynthesis and cellular respiration are biochemical pathways Biochemical pathways are a series of chemical reactions. The products of one reaction become the reactants of the next

HARVESTING ENERGY How does energy enter the food chain? How do organisms use that energy to fuel their systems?

Cellular Respiration Releasing energy from the products of photosynthesis Oxygen burns glucose to release carbon dioxide, water, and ENERGY ENERGY is released in the form of ATP

AMOUNT of Energy The CALORIE CALORIES are the UNITS used to express how much energy is in food CALORIE ~ amount of energy needed to raise the temperature of 1 gram of water by 1 °C Food labels use kilocalories 1 kilocalorie = 1000 calories

CALORIES per GRAM Macromolecules Different macromolecules have different amounts of energy Depends on their chemical structure and bonding

The MITOCHONDRIA 2 of the 3 stages of CELLULAR RESPIRATION occur in the Mitochondria

Parts of the MITOCHONDRIA Identify the parts of the mitochondria

Parts of the MITOCHONDRIA Identify the parts of the mitochondria

3 MAIN STAGES of Cellular Respiration Glycolysis Krebs cycle Electron transport chain The molecule we will use in our examples is: GLUCOSE The simple sugar!

STAGES of Cellular Respiration How it all begins Heterotrophs must take in energy from outside sources When heterotrophs take in (eat/consume) food sources (glucose or other molecules such as carbohydrates, proteins, and fats)-the foods don ’ t already available in a form that can be used right away! Heterotrophs must convert the food into usable energy

OVERVIEW of Cellular Respiration Cellular Respiration is the transformation of chemical energy in food into chemical energy cells can use: ATP The reactions proceed the same way for both plants and animals. (Animals use consumed foods, plants use self-made and stored food) Overall Reaction: C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O

OXYGEN “Respiration” means “breathing” THE CONNECTION ~ Most of the biochemical pathways that release energy from foods need oxygen Breakdown of glucose begins in the cell’s cytoplasm Then splits into one of TWO (2) PATHWAYS: AEROBIC Cellular respiration ANAEROBIC Cellular respiration

AEROBIC RESPIRATION AEROBIC Respiration ~ requires OXYGEN Krebs Cycle Electron transport chain Electron transport chain directly requires oxygen Krebs cycle NEEDS electron transport chain to function

ANAEROBIC RESPIRATION Anaerobic Respiration ~ does not REQUIRE oxygen Glycolysis Its final products are used as reactants for the AEROBIC respiration steps

STAGES OF CELLULAR RESPIRATION

WHERE Cellular Respiration Occurs GLYCOLYSIS ~ Cytoplasm KREBS CYCLE ~ Mitochondria ELECTRON TRANSPORT CHAIN ~ Mitochondria

GLYCOLYSIS Glycolysis is the first stage of cellular respiration Glucose is broken down into TWO (2) molecules of pyruvic acid (a 3-carbon molecule) Pyruvic acid is a REACTANT in the Krebs cycle. ATP and NADH are produced (NADH is passed on to Electron Transport Chain)

GYCOLYSIS ~ STAGE 1

What’s so great about GLYCOLYSIS? Produces ATP very fast Helpful when the cell has increased energy demands Does not require oxygen

KREBS CYCLE ~ STAGE 2 Occurs in mitochondria WITH OXYGEN present, PYRUVIC ACID from glycolysis is passed on to KREBS CYCLE Pyruvic acid is broken down into carbon dioxide (CO 2 ) in series of reactions The series of reactions release energy Also known as ‘citric acid cycle’

The Krebs Cycle Krebs cycle is the 2nd stage of cellular respiration Reactants: Pyruvic Acid (produced by glycolysis) Products: ATP and CO 2 (Citric acid is first compound formed in series of reactions)

Energy Extraction during Krebs Cycle During the series of reactions, ENERGY is released by the breaking and rearranging of carbon bonds Energy is captured in the forms of ATP, NADH, and FADH 2.

Krebs Cycle uses Electron Carriers Electron carriers NAD + and FAD each accept pairs of high-energy electrons Form NADH and FADH 2 NADH and FADH 2 are used in the electron transport chain to generate ATP

Overview ~ Krebs Cycle

Electron Transport and ATP Synthesis Q: How does the electron transport chain use high-energy electrons from glycolysis and the Krebs cycle? A: The electron transport chain uses the high- energy electrons from glycolysis and the Krebs cycle to convert ADP into ATP.

Electron Transport 1)NADH and FADH 2 pass their high-energy electrons to electron carrier proteins in the electron transport chain 2)At the end of the electron transport chain, the electrons combine with H + ions and oxygen to form water 3)Energy generated by the electron transport chain is used to move H+ ions against a concentration gradient across the inner mitochondrial membrane and into the intermembrane space 4)H+ ions pass back across the mitochondrial membrane through the ATP synthase, causing the ATP synthase molecule to spin 5)With each rotation, the ATP synthase attaches a phosphate to ADP to produce ATP.

Overview ~ Electron Transport Chain

Cellular Respiration ~ TOTAL ENERGY PRODUCTION~ The complete breakdown of glucose results in 36 molecules of ATP Glycolysis, Krebs Cycle, and Electron Transport Chain all work together as the THREE (3) Stages ANY food molecules can be broken down, including proteins and lipids

OXYGEN ~ Can we get on without it? What happens if oxygen is not available to help us extract energy from food molecules? Can our cells use another pathway? In the absence of oxygen, fermentation releases energy from food molecules by producing ATP

FERMENTATION When conditions are ANAEROBIC, fermentation becomes the next step after glycolysis Fermentation converts NADH back into NAD + NAD + cycles back to glycolysis, which continues to produce ENERGY

TYPES OF FERMENTATION Alcoholic Fermentation Lactic Acid Fermentation

ALCOHOLIC Fermentation Used by yeasts and other microorganisms Produces ethyl alcohol and carbon dioxide (CO 2 ) What makes BREAD rise! Also makes alcoholic beverages.

Alcoholic Fermentation Chemical equation: Pyruvic acid + NADH  Alcohol + CO 2 + NAD +

LACTIC ACID FERMENTATION Used by most organisms Converts pyruvic acid into NAD + NAD + cycles back to glycolysis, which continues to produce ENERGY Chemical equation: Pyruvic acid + NADH  Lactic acid + NAD +

Energy and Exercise How does the body produce ATP during different stages of exercise? For short, quick bursts of energy, the body uses ATP already in muscles as well as ATP made by lactic acid fermentation. For exercise longer than about 90 seconds, cellular respiration is the only way to continue generating a supply of ATP!

Quick Energy Cells normally contain small amounts of ATP produced during cellular respiration Enough for a few seconds of intense activity! Lactic acid fermentation can supply enough ATP to last about 90 seconds Extra oxygen is required to get rid of the lactic acid produced. Following intense exercise, a person will huff and puff for several minutes in order to pay back the built-up “oxygen debt” and clear the lactic acid from the body! Phew!!!

Long-Term Energy INTENSE exercise lasting longer than 90 seconds: cellular respiration is required to continue production of ATP Cellular respiration releases energy more slowly than fermentation The body stores energy in the form of the carbohydrate glycogen. These glycogen stores are enough to last for 15 to 20 minutes of activity. After that, the body begins to break down other stored molecules, including fats, for energy.

Long-Term Energy Hibernating animals like this brown bear rely on stored fat for energy when they sleep through the winter.

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