Cellular Respiration (An Overview)

Objectives SWBAT describe the process of cellular respiration. SWBAT compare cellular respiration to photosynthesis.

Vocabulary Cellular respiration Aerobic Anaerobic Glycolysis Krebs cycle Mitochondria (review) ATP and Electron Transport Chain from Sec. 4.1

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.

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.

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.

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.

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).

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.

Cellular Respiration Cellular respiration is almost a mirror image of photosynthesis. Photosynthesis chemical equation Cellular respiration chemical equation

Cellular Respiration Mitochondria and chloroplasts are similar in structure. A mitochondrion is surrounded by a membrane. It has 2 parts that are involved in cellular respiration: the matrix and the inner mitochondrial membrane.

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.

Krebs Cycle (also known as citric acid 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. 6H O 2 6CO 6O mitochondrion matrix (area enclosed by inner membrane) inner membrane ATP energy energy from glycolysis 1 4 3 and Krebs cycle

energy from glycolysis Krebs Cycle 6H O 2 6CO 6O mitochondrion matrix (area enclosed by inner membrane) inner membrane ATP energy energy from glycolysis 1 4 3 and In the Krebs cycle Three-carbon molecules from glycolysis are broken down in a cycle of chemical reactions producing: Small amount of ATP is made. Other types of energy-carrying molecules are made. Carbon dioxide is released as waste product. Energy transfer to the second stage of cellular respiration. Krebs cycle

Energy Transport Chain The energy carrying molecules from the Krebs cycle along with oxygen are used to make lots of ATP. 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. Electron Transport