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Cellular Respiration(An Overview)

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Objectives

• SWBAT describe the process of cellular respiration.

• SWBAT compare cellular respiration to photosynthesis.

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Vocabulary

• Cellular respiration• Aerobic• Anaerobic • Glycolysis• Krebs cycle• Mitochondria (review)• ATP and Electron Transport Chain from Sec.

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Cellular Respiration• While plants make their own food, we animals

have to eat other organisms (namely plants – directly or indirectly).

• Animals and plants, through cellular respiration, make ATP by breaking down glucose.

• Cellular respiration releases chemical energy from sugars and other carbon-based molecules to make ATP when oxygen is present.

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Cellular Respiration

• Cellular respiration is an aerobic process, which takes place in the mitochondria (your cells power plants).– Aerobic processes require oxygen to take place.– Mitochondria make most of your cell’s ATP.

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Glycolysis• The mitochondria cannot directly make ATP

from food. – Foods are broken down into smaller molecules

such as glucose.• Glycolysis is the process that breaks down

glucose (thus the name).– Glycolysis occurs in the cell’s cytoplasm and does

not need oxygen.– This means glycolysis is an anaerobic process.

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Glycolysis• Glycolysis splits glucose into two three-

carbon and makes 2 molecules of ATP.

The products of glycolysis are then broken down in the mitochondria

to make ATP.

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Glycolysis (an aside)• Glycolysis was among the first biochemical

processes to evolve. • Early forms of life produced ATP from

glycolysis.– Why? Because glycolysis takes place in the

cytoplasm (this is before eukaryotes)– and does not require oxygen to take place.• Earth did not always have as much oxygen as it does

today (in fact, 2.5 billion years ago, it would have had no free oxygen).

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Endosymbiosis theory (an aside)

• Mitochondria were once prokaryotes that were engulfed by other prokaryotes. – This process may have led to the evolution of

eukaryotes and cellular respiration. – It would have taken place after photosynthesizers

had added significant oxygen to Earth’s atmosphere.

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Cellular Respiration• Cellular respiration is almost a mirror image of

photosynthesis.Photosynthesis

chemical equation

Cellular respiration chemical equation

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Cellular Respiration

• Mitochondria and chloroplasts are similar in structure.

1. A mitochondrion is surrounded by a membrane.

2. It has 2 parts that are involved in cellular respiration: the matrix and the inner mitochondrial membrane.

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Cellular Respiration

• Part 1: the matrix where the Krebs cycle takes place.

• Part 2: the inner mitochondrial membrane where the electron transport chain takes place.

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Krebs Cycle (also known as citric acid 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

Krebs cycle

• The Krebs cycle produces molecules that carry energy to the second part of cellular respiration – the electron transport chain.– takes place in

mitochondrial matrix– breaks down three-carbon

molecules from glycolysis– makes small amount of ATP– Releases carbon dioxide– Transfers energy-carrying

molecules to electron transport chain.

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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

Krebs cycle

In the Krebs cycle1. Three-carbon molecules from

glycolysis are broken down in a cycle of chemical reactions producing: a) Small amount of ATP is made.b) Other types of energy-

carrying molecules are made.c) Carbon dioxide is released as

waste product.2. Energy transfer to the second

stage of cellular respiration.

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Energy Transport Chain• The energy carrying molecules from the Krebs cycle along

with oxygen are used to make lots of ATP.

Electron Transport

• takes place in inner membrane

• energy transferred to electron transport chain

• oxygen enters process• ATP produced (up to 38

molecules)• water is released as a

waste product.