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Bioenergetic Reactions

Photosynthesis & Respiration

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Bioenergetic Reactions

• Bioenergetic reactions that occur in living things and involve the storing or the releasing of energy.

• The source of energy for all living things is the sun.

• However, most living things cannot use energy in this form.

• Bioenergetic reactions create and use energy in the form of ATP.

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What is ATP and ADP?• The principal chemical

compound that cells use to store and release energy is adenosine triphosphate, ATP.

• ATP consists of a 5-carbon sugar called ribose, and three phosphate groups.

• Those three phosphate groups are the key to ATP’s ability to store and release energy.

• ADP is a compound that is very similar to ATP, except it has two phosphate groups instead of three.

• ADP is constantly in search of a third phosphate to convert it to ATP.

• ADP does not contain as much energy as ATP.– ADP is like a half charged

battery and ATP is like a fully charged battery.

Releasing

• When the chemical bond is broken between the 2nd and 3rd phosphate group in ATP, a tremendous amount of energy is released.

• ATP has enough energy to power a variety of cellular activities.– active transport across cell

membranes – protein synthesis – muscle contraction

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Using Biochemical Energy

• One way that cells use the energy provided by ATP is to carry out active transport.

• ATP is also used for the synthesis of proteins and nucleic acids and responses to chemical signals at the cell surface.

• ATP is a useful source of energy, but cells only have a small amount of ATP.– It is not a good molecule for storing

large amounts of energy over the long term.

– Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose.

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Photosynthetic Organisms

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Photosynthesis• 6CO2 + 6H2O → C6H12O6 + 6O2

• Photosynthesis uses the energy of sunlight to convert H2O and CO2 into high energy sugars and oxygen.

The Process

• Photosynthesis takes place in the chloroplast of the plant.

• The reactions of photosynthesis occurs in two parts: light dependent and light-independent (Calvin Cycle) reactions. 8

Light Dependent Reaction

• Light is required for these reactions to occur.• This segment occurs within the thylakoid

membrane of the chloroplast.• In Photosystem II, the energy from light is

absorbed by the chlorophyll and transferred to the electron to energize it.

• These high-energy electrons are passed on to the ETC.

• The energy in these electrons are used to break up water molecules into energized electrons, hydrogen ions, and oxygen.– The oxygen is given to the atmosphere.– This process is called hydrolysishydrolysis.

• In Photosystem I, pigments use energy from light to reenergize the electrons. NADPH is formed.

• ATP is also formed at the end of this reaction.9

Light-Independent Reaction• The light-independent reaction is

also known as the Calvin cycle.• This reaction occurs in the

stroma of the chloroplast, which is the region outside the thylakoid membrane, and does not require light.

• The ATP and NADPH from the light dependent reaction are used to produce high-energy sugars.

• This phase works steadily to remove CO2 from the atmosphere and turn out energy rich sugars.

• The plant uses the sugars to meet its energy needs and to build more complex macromolecules such as cellulose.

Chemical Energy and Food

• There is quite a bit of energy contained in the food that we eat.

• The process of releasing the energy contained in the foods that we eat begins with a process called glycolysis.

• Glycolysis releases only a small amount of energy.

• If oxygen is present, glycolysis leads to two other pathways that release a great deal of energy.

• If oxygen is not present, however, glycolysis is followed by a different pathway.

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Glycolysis

• For glycolysis to begin, 2 ATP’s must be borrowed and repayed at the end.

• Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound.

• The energy yield from glycolysis is small: 2 ATP’s, but the process itself is quite fast.

• Glycolysis does not require oxygen, so energy can still be supplied when oxygen is not available.

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Fermentation (No oxygen = Anaerobic)Occurs outside the mitochondria

There are two types of fermentation.http://www.5min.com/Video/How-Fermentation-Works-83226972

• Alcoholic Fermentation– Used by yeast and a few

other microorganisms– Produces ethyl alcohol and

carbon dioxide as wastes.– Pyruvic acid + NADH →

alcohol + CO2 + NAD+

– This process is used by the beer & wine industries for the production of their products.

• Lactic Acid Fermentation– Used by multicellular organisms and

some unicellular organisms.– Lactic acid is produced in your muscles

during rapid exercise when the body cannot supply enough oxygen to the tissues.

• The buildup of lactic acid in your muscles will make them sore!!

– Prokaryotes are used in the production of a wide variety of foods and beverages such as cheese, yogurt, buttermilk, and sour cream.

– Pyruvic acid + NADH → lactic acid + NAD+

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Organisms that do aerobic cellular respiration

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Aerobic Cellular Respiration

• This reaction releases energy from the chemical bonds of carbohydrates.

• This is an aerobic process which means it requires oxygen.

• This reaction takes place in an organelle called the mitochondria.

• Equation:

6O2 + C6H12O6 6H20 + 6CO2 + 36ATP36ATP

The Kreb’s Cycle

• When oxygen is present at the end of glycolysis, the pyruvic acid passes to the 2nd stage of cellular respiration which is referred to as aerobic respiration.

• This takes place inside the mitochondria.

• Pyruvic acid enters the mitochondria and is broken down into CO2, NADH, ATP, & FADH2.

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Electron Transport Chain & Products of Krebs and ETC

• Electron Transport Chain– The electrons from NADH

and FADH2 are passed on to ETC.

– The electrons convert ADP to ATP.

– This mechanism creates the needed energy supply.

• Products of Kreb’s & ETC– The Kreb’s Cycle and

ETC generate 34 ATP’s.

– Remember 2 molecules of ATP were produced by glycolysis.

– Cellular respiration creates 36 ATP’s for every 1 sugar molecule that is processed.

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Photosynthesis & Respiration Comparison

• Used by plants and some bacteria.

• Photosynthesis captures energy.

• Reaction occurs in the chloroplast.

• Reactants are CO2 + H2O.

• Products are C6H12O6 + O2.

• Equation: 6CO2 + 6H2O → C6H12O6 + 6O2

• Used by all organisms.• Respiration releases energy.• Reaction occurs in the

mitochondria.

• Reactants are C6H12O6 + 6O2.

• Products are ATP + CO2 + H2O

• Equation:

C6H12O6 + 6O2 → 6CO2 + 6H2O