10/27/2015 CHAPTER 6 BIOCHEMICAL PATHWAYS

10/27/2015 BIOCHEMICAL REACTIONS Organisms obtain energy through enzyme- controlled biochemical reactions Organisms obtain energy through enzyme- controlled biochemical reactions Release energy stored in chemical bonds Release energy stored in chemical bonds The ultimate source of all energy is the sun The ultimate source of all energy is the sun Converted to chemical energy through photosynthesis Converted to chemical energy through photosynthesis Organisms convert this chemical energy (food) into usable energy through cellular respiration Organisms convert this chemical energy (food) into usable energy through cellular respiration Controlled release Controlled release Large organic molecules are broken down Large organic molecules are broken down Photosynthetic organisms produce food for their own use and for others Photosynthetic organisms produce food for their own use and for others

10/27/2015 BIOCHEMICAL REACTIONS All organisms carry out cellular respiration which may be: All organisms carry out cellular respiration which may be: Aerobic – uses oxygen Aerobic – uses oxygen Anaerobic – does not use oxygen Anaerobic – does not use oxygen Organisms can be classified based on how they obtain nutrients: Organisms can be classified based on how they obtain nutrients: Autotrophs – make their own food (green plants, algae) Autotrophs – make their own food (green plants, algae) Heterotrophs – obtain food from their surroundings (all animals, fungi) Heterotrophs – obtain food from their surroundings (all animals, fungi)

10/27/2015 BIOCHEMICAL REACTIONS Some bacterial cells can produce food through chemosynthesis (chemical reactions) Some bacterial cells can produce food through chemosynthesis (chemical reactions) Occur within the cytoplasm Occur within the cytoplasm In eukaryotic cells, these reactions are carried out in specific organelles In eukaryotic cells, these reactions are carried out in specific organelles Photosynthesis – chloroplasts Photosynthesis – chloroplasts Cellular respiration – mitochondria Cellular respiration – mitochondria

10/27/2015 BIOCHEMICAL PATHWAYS Can be classified two ways: Can be classified two ways: Catabolic reactions - breakdown of organic molecules; releases energy Catabolic reactions - breakdown of organic molecules; releases energy Anabolic reactions - synthesis of new organic molecules; requires energy Anabolic reactions - synthesis of new organic molecules; requires energy Energy for these reactions is supplied by adenosine triphosphate (ATP) Energy for these reactions is supplied by adenosine triphosphate (ATP) Energy is released when ATP is broken down into ADP Energy is released when ATP is broken down into ADP Reformed when a phosphate group is added to ADP (phosphorylation reaction) Reformed when a phosphate group is added to ADP (phosphorylation reaction)

10/27/2015 “Like charging a battery”

10/27/2015 The “actual” process AMP ADP ATP

10/27/2015 AEROBIC CELLULAR RESPIRATION The breakdown of glucose molecules in the presence of oxygen The breakdown of glucose molecules in the presence of oxygen Carbon dioxide and water are produced Carbon dioxide and water are produced C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy (ATP + heat) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy (ATP + heat) glucose + oxygen → carbon dioxide + water + energy glucose + oxygen → carbon dioxide + water + energy

10/27/2015 AEROBIC CELLULAR RESPIRATION Begins in the cytoplasm and is completed in the mitochondria. Begins in the cytoplasm and is completed in the mitochondria. Series of enzyme-controlled reactions that are divided into three pathways: Series of enzyme-controlled reactions that are divided into three pathways: Glycolysis Glycolysis Krebs cycle (citric acid cycle) Krebs cycle (citric acid cycle) Electron transport system Electron transport system

10/27/2015 GLYCOLYSIS Glycolysis – the breakdown of glucose; occurs in the cytoplasm Glycolysis – the breakdown of glucose; occurs in the cytoplasm Glucose (6-carbon atoms) is broken into two 3-carbon molecules called pyruvate (pyruvic acid). Glucose (6-carbon atoms) is broken into two 3-carbon molecules called pyruvate (pyruvic acid). 2 ATP molecules are produced 2 ATP molecules are produced Electrons released from these reactions are transferred to the electron transport chain. Electrons released from these reactions are transferred to the electron transport chain. Will be attached to oxygen atoms Will be attached to oxygen atoms

10/27/2015 GLYCOLYSIS

KREBS CYCLE The pyruvate produced in the cytoplasm moves into the mitochondria, releasing The pyruvate produced in the cytoplasm moves into the mitochondria, releasing Carbon dioxide (remnants of pyruvate) Carbon dioxide (remnants of pyruvate) Electrons Electrons 2 ATP molecules 2 ATP molecules The electrons are transferred to NADH and FADH2 (electron carriers), which take them to the electron transport system. The electrons are transferred to NADH and FADH2 (electron carriers), which take them to the electron transport system.

10/27/2015 KREBS CYCLE

10/27/2015 ELECTRON TRANSPORT CHAIN When electrons receive additional energy they move to a higher energy level. When electrons receive additional energy they move to a higher energy level. When the electrons fall back to their original position they give up that energy. When the electrons fall back to their original position they give up that energy. Special molecules (NADH, NADPH, FADH2) capture these excited electrons and transfer them to other chemical reactions Special molecules (NADH, NADPH, FADH2) capture these excited electrons and transfer them to other chemical reactions Tied to the formation of ATP Tied to the formation of ATP Oxidation-reduction reactions Oxidation-reduction reactions Electrons usually come from hydrogen creating H+ (hydrogen nucleus) Electrons usually come from hydrogen creating H+ (hydrogen nucleus)

10/27/2015 ELECTRON TRANSPORT SYSTEM Electrons are transferred through a series of reactions until they are accepted by oxygen Electrons are transferred through a series of reactions until they are accepted by oxygen Oxygen combines with hydrogen ions to make water. Oxygen combines with hydrogen ions to make water. This process generates large amounts of ATP This process generates large amounts of ATP 32 ATP total 32 ATP total

10/27/2015 Electron Transport System

10/27/2015 FERMENTATION (Anaerobic Respiration) Two main types of fermentation: Two main types of fermentation: Alcoholic fermentation Alcoholic fermentation Lactic acid fermentation Lactic acid fermentation Alcoholic fermentation – used by yeast cells in the absence of oxygen Alcoholic fermentation – used by yeast cells in the absence of oxygen Pyruvate from glycolysis is converted to ethanol and carbon dioxide Pyruvate from glycolysis is converted to ethanol and carbon dioxide The yeast cells gain 2 ATP The yeast cells gain 2 ATP

10/27/2015 FERMENTATION Lactic acid fermentation – pyruvate from glycolysis is converted to lactic acid Lactic acid fermentation – pyruvate from glycolysis is converted to lactic acid 2 ATP molecules are produced 2 ATP molecules are produced In bacteria, the build up of lactic acid interferes with metabolic functions and they die. In bacteria, the build up of lactic acid interferes with metabolic functions and they die. Humans use lactic acid waste products from these types of bacteria to make yogurt, cultured sour cream, cheeses, and other fermented dairy products. Humans use lactic acid waste products from these types of bacteria to make yogurt, cultured sour cream, cheeses, and other fermented dairy products.

10/27/2015 ANAEROBIC RESPIRATION In humans, red blood cells produce energy through lactic acid fermentation In humans, red blood cells produce energy through lactic acid fermentation They don’t have mitochondria They don’t have mitochondria Muscle cells can use aerobic and anaerobic respiration. Muscle cells can use aerobic and anaerobic respiration. For anaerobic respiration, lactic acid accumulates resulting in fatigue, cramping, and pain. For anaerobic respiration, lactic acid accumulates resulting in fatigue, cramping, and pain. Must stop the activity or muscles will die Must stop the activity or muscles will die When enough oxygen is available, lactic acid is converted to pyruvic acid Krebs cycle will proceed. When enough oxygen is available, lactic acid is converted to pyruvic acid Krebs cycle will proceed.

10/27/2015 ANAEROBIC RESPIRATION

10/27/2015 RESPIRATION

FAT RESPIRATION Fats and proteins can also be used as a source of energy. Fats and proteins can also be used as a source of energy. Fats are digested to fatty acids and glycerol Fats are digested to fatty acids and glycerol Proteins are digested to amino acids Proteins are digested to amino acids Requires several more complex steps. Requires several more complex steps. In fats, fatty acids and glycerol are broken down through the Krebs cycle in the mitochondria. In fats, fatty acids and glycerol are broken down through the Krebs cycle in the mitochondria. Can produce more ATP than carbohydrates Can produce more ATP than carbohydrates Serve as long term energy storage Serve as long term energy storage Twice as much energy per gram of fat than gram of carbohydrate Twice as much energy per gram of fat than gram of carbohydrate

10/27/2015 PROTEIN RESPIRATION After proteins are broken down to amino acids, the amino group is removed. After proteins are broken down to amino acids, the amino group is removed. The carbon skeleton enters the respiratory cycle as acetyl, pyruvic acid, or other molecules found in the Krebs cycle. The carbon skeleton enters the respiratory cycle as acetyl, pyruvic acid, or other molecules found in the Krebs cycle. The removed amino group is converted to ammonia. The removed amino group is converted to ammonia. Excreted as ammonia, uric acid, or urea (very toxic; must be eliminated) Excreted as ammonia, uric acid, or urea (very toxic; must be eliminated) Proteins cannot be stored, so they are converted to fat or carbohydrates. Proteins cannot be stored, so they are converted to fat or carbohydrates.

10/27/2015 PHOTOSYNTHESIS Process in which energy from sunlight is converted to chemical energy. Process in which energy from sunlight is converted to chemical energy. Anabolic process Anabolic process Used by plants, algae, and some bacteria Used by plants, algae, and some bacteria The green pigment chlorophyll absorbs sunlight. The green pigment chlorophyll absorbs sunlight. Takes place in chloroplasts, which have 2 regions: Takes place in chloroplasts, which have 2 regions: Granum – stacks of membranous sacs (thylakoids) that contain chlorophyll Granum – stacks of membranous sacs (thylakoids) that contain chlorophyll Stroma - the space between the membranes Stroma - the space between the membranes

10/27/2015 PHOTOSYNTHESIS Can be summarized by the following equation: Can be summarized by the following equation: Light energy + 6 CO2 + 6 H2O → C6H12O6 + 6 O2 Light energy + 6 CO2 + 6 H2O → C6H12O6 + 6 O2 carbon dioxide + water → glucose + oxygen carbon dioxide + water → glucose + oxygen Opposite of cellular respiration! Opposite of cellular respiration!

10/27/2015 PHOTOSYNTHESIS

10/27/2015 PHOTOSYNTHESIS Three separate events: Three separate events: Light-capturing events Light-capturing events Light-dependent reactions Light-dependent reactions Light-independent reactions Light-independent reactions Visible light is a combination of different wavelengths of light seen as different colors. Visible light is a combination of different wavelengths of light seen as different colors. Chlorophyll absorbs red and blue light, reflects green Chlorophyll absorbs red and blue light, reflects green Pigments called carotenoids (yellow, orange, red) also capture light, produce excited electrons – visible in the fall Pigments called carotenoids (yellow, orange, red) also capture light, produce excited electrons – visible in the fall

10/27/2015 PHOTOSYNTHESIS Light-capturing events Light-capturing events Pigments capture light energy which causes some electrons to become “excited” Pigments capture light energy which causes some electrons to become “excited” Pigments are arranged into clusters called photosystems – helps concentrate energy Pigments are arranged into clusters called photosystems – helps concentrate energy Light-dependent reactions Light-dependent reactions Take place in the thylakoid membranes of the grana Take place in the thylakoid membranes of the grana Excited electrons are passed through an electron transport system, producing ATP and NADPH (electron carrier) Excited electrons are passed through an electron transport system, producing ATP and NADPH (electron carrier) Some electrons split water producing oxygen gas, hydrogen ions, and additional electrons Some electrons split water producing oxygen gas, hydrogen ions, and additional electrons

10/27/2015 PHOTOSYNTHESIS Light-independent reactions Light-independent reactions Occur in the stroma Occur in the stroma Energy from excited electrons is used to make glucose, lipids, phospholipids, steroids, and other organic molecules from carbon dioxide Energy from excited electrons is used to make glucose, lipids, phospholipids, steroids, and other organic molecules from carbon dioxide Some of these molecules may also be used to produce DNA, RNA, or ATP Some of these molecules may also be used to produce DNA, RNA, or ATP

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OTHER ASPECTS OF PLANT METABOLISM Plants produce carbohydrates, fats, proteins, and nucleic acids from the products of photosynthesis Plants produce carbohydrates, fats, proteins, and nucleic acids from the products of photosynthesis Can produce some toxins and organic molecules that are used as medicines Can produce some toxins and organic molecules that are used as medicines May also produce vitamins for themselves and other organisms May also produce vitamins for themselves and other organisms Produce oxygen in photosynthesis which is used for cellular respiration by all living things Produce oxygen in photosynthesis which is used for cellular respiration by all living things

10/27/2015 AUTOTROPHS AND HETEROTROPHS All living things need oxygen for cellular respiration All living things need oxygen for cellular respiration Green plants produce oxygen in photosynthesis, but they also use it in cellular respiration Green plants produce oxygen in photosynthesis, but they also use it in cellular respiration Produce more than enough and release the rest Produce more than enough and release the rest Animals are dependent on plants not only for oxygen, but also for essential nutrients to maintain metabolism and construct tissues Animals are dependent on plants not only for oxygen, but also for essential nutrients to maintain metabolism and construct tissues Animals supply materials needed by plants and vice versa. Animals supply materials needed by plants and vice versa. Essential to life on Earth Essential to life on Earth

10/27/2015 Need to Know What is cellular respiration? What is cellular respiration? What are the 3 steps? What are the 3 steps? How much ATP is formed at each step? How much ATP is formed at each step? Where in the cell do these occur? Where in the cell do these occur? What is ATP? What is ATP? What is photosynthesis? What is photosynthesis? What are the 3 steps? What are the 3 steps? Where do these processes occur in a cell? Where do these processes occur in a cell?

10/27/2015 CHAPTER 6 BIOCHEMICAL PATHWAYS

10/27/2015

AMP ADP ATP

PHOTOSYNTHESIS

10/27/2015

CHAPTER 6 BIOCHEMICAL PATHWAYS

10/27/2015

AMP ADP ATP

PHOTOSYNTHESIS

10/27/2015