Unit 4 Chemical Energy And Atp

4.1 Chemical Energy and ATP

KEY CONCEPT All cells need chemical energy.


The chemical energy used for most cell processes is carried by ATP.

• Molecules in food store chemical energy in their bonds.

Starch molecule

Glucose molecule


phosphate 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.


Organisms break down carbon-based molecules to produce ATP.

• Carbohydrates are the molecules most commonly broken down to make ATP.

– not stored in large amounts– up to 36 ATP from one

glucose molecule

triphosphateadenosine

adenosine diphosphate

tri=3

di=2


• 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


A few types of organisms do not need sunlight and photosynthesis as a source of energy.

• Some organisms live in places that never get sunlight.

• In chemosynthesis, chemical energy is used to build carbon-based molecules.– similar to photosynthesis– uses chemical energy

instead of light energy


KEY CONCEPTThe overall process of photosynthesis produces sugars that store chemical energy.


Photosynthetic organisms are producers.

• Producers make their own source of chemical energy.

• Plants use photosynthesis and are producers.

• Photosynthesis captures energy from sunlight to make sugars.


• Chlorophyll is a molecule that absorbs light energy.

chloroplast

leaf cell

leaf

• In plants, chlorophyll is found in organelles called chloroplasts.


Photosynthesis in plants occurs in chloroplasts.

• Photosynthesis takes place in two parts of chloroplasts.– grana (thylakoids)– stroma

chloroplast

stroma

grana (thylakoids)


• 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


• 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


• The equation for the overall process is:

6CO2 + 6H2O C6H12O6 + 6O2

C6H12O6

granum (stack of thylakoids)

thylakoid

sunlight

1 six-carbon sugar

6H2O

6CO2

6O2

chloroplastchloroplast1

2

43

energy

stroma (fluid outside the thylakoids)


KEY CONCEPT Photosynthesis requires a series of chemical reactions.


The first stage of photosynthesis captures and transfers energy.

• The light-dependent reactions include groups of molecules called photosystems.


• 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


• The light-dependent reactions produce ATP.

– hydrogen ions flow through a channel in the thylakoid membrane

– ATP synthase attached to the channel makes ATP


• Light-independent reactions occur in the stroma and use CO2 molecules.

The second stage of photosynthesis uses energy from the first stage to make sugars.


• 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


– two three-carbon molecules bond to form a sugar– remaining molecules stay in the cycle

• A molecule of glucose is formed as it stores some of the energy captured from sunlight.


KEY CONCEPT The overall process of cellular respiration converts sugar into ATP using oxygen.


Cellular respiration makes ATP by breaking down sugars.

• Cellular respiration is aerobic, or requires oxygen.• Aerobic stages take place in mitochondria.

mitochondrion

animal cell


• Glycolysis must take place first.

– anaerobic process (does not require oxygen)– takes place in cytoplasm– splits glucose into two three-carbon molecules– produces two ATP molecules


Cellular respiration is like a mirror image of photosynthesis.

• The Krebs cycle transfers energy to an electron transport chain.– takes place in

mitochondrial matrix– breaks down three-carbon

molecules from glycolysis– makes a small amount of

ATP– releases carbon dioxide– transfers energy-carrying

molecules

6H O2

6CO 2

6O 2

mitochondrionmitochondrion

matrix (area enclosedby inner membrane)

inner membrane

ATP

ATP

energy

energy from glycolysis

1

2

4

3

and

and

and

Krebs Cycle


6H O2

6CO 2

6O 2

mitochondrionmitochondrion

matrix (area enclosedby inner membrane)

inner membrane

ATP

ATP

energy

energy from glycolysis

1

2

4

3

and

and

and

• The electron transport chain produces a large amount of ATP.

– takes place in inner membrane

– energy transferred to electron transport chain

– oxygen enters process

– ATP produced

– water released as awaste product

Electron Transport


• The equation for the overall process is:

C6H12O6 + 6O2 6CO2 + 6H2O

• The reactants in photosynthesis are the same as the products of cellular respiration.


KEY CONCEPT Cellular respiration is an aerobic process with two main stages.


Glycolysis is needed for cellular respiration.

• The products of glycolysis enter cellular respiration when oxygen is available.– two ATP molecules are used to split glucose– four ATP molecules are produced– two molecules of NADH produced– two molecules of pyruvate 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.


– 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 Krebs cycle produces energy-carrying molecules.


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 achannel in themembrane


• The breakdown of one glucose molecule produces up to38 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 is the second main part of cellular respiration.

• The electron transport chain uses NADH and FADH2 to

make ATP.


KEY CONCEPT Fermentation allows the production of a small amount of ATP without oxygen.


Fermentation allows glycolysis to continue.

• 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.


• Fermentation allows glycolysis to continue making ATP when oxygen is unavailable.

• 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+

• NAD+ is recycled to glycolysis


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


• Fermentation is used in food production.

– yogurt

– cheese

– bread

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Unit 4 Chemical Energy And Atp