METABOLISM
What is metabolism? METABOLISM Total of all chemical reactions occurring within the body Categories of metabolic reactions Catabolic reactions Degradation pathways Anabolic reactions Synthesis pathways 2
METABOLISM 3
What is energy? ENERGY No mass; does not take up space Has the capacity to do work (potential energy) or to put matter into motion (kinetic energy) Can be converted into different forms but is not created or destroyed 4
ENERGY What types of energy are there? Chemical Energy stored in chemical bonds Electrical Involves movement of charged particles Mechanical Involves movement of matter Electromagnetic (radiant) Energy traveling in waves 5
Quick Quiz: Potential energy can be stored in all of the following forms except A) Electromagnetic energy B) Electrical energy C) Mechanical energy D) Chemical energy 6
ENERGY Where does our energy for metabolism come from? Chemical energy Nutrients (food) Electromagnetic energy Heat (thermal) Sun or geothermal sources Visible light 7
ENERGY Energy for cellular metabolism must be refined, or converted to useful types of energy Photosynthesis Electromagnetic energy (sunlight) chemical energy Aerobic respiration Chemical energy (chemical bonds of certain molecules) chemical energy (more usable form for cells) 8
ATP (adenosine triphosphate) 9
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Quick Quiz: ATP is an example of which of the following energy forms? A) Electromagnetic energy B) Thermal energy C) Mechanical energy D) Chemical energy 11
Energy Flow & Nutrient Cycling in Biological Systems Energy 1-way flow Ultimately lost as heat Nutrients Cycled 12
Nutrients What are nutrients? Chemical substances needed for normal metabolism & growth O C H N Ca P K S Na Cl Mg I Fe Organic vs. inorganic nutrients Macronutrients Proteins Carbohydrates Lipids Nucleic acids 13
Quick Quiz: Which of the following is NOT recycled in an ecosystem? A) Carbon B) Electromagnetic energy C) Water D) Nitrogen 14
Chemical reactions ENZYMES Reactants are converted into products Atoms become combined in new forms O 2 + 2 H 2 2 H 2 O 15
Reaction rates ENZYMES Typically too slow to sustain life Need help to speed up Enzymes are biological catalysts Catalysts speed up reactions They do not make a reaction happen that wouldn t have happened otherwise Enzymes are usually made out of protein 16
Reaction rates ENZYMES Typically too slow to sustain life Need help to speed up Enzymes are biological catalysts Catalysts speed up reactions They do not make a reaction happen that wouldn t have happened otherwise Enzymes are usually made out of protein 17
ENZYMES In order to react, molecules go through awkward transitions Unstable, high-energy states: Transition states Enzymes help to speed up reactions by stabilizing transition states 18
Free energy ENZYMES Reactants: 2H 2 O 2 Activation energy Difference between free energy of reactants and products Products: 2H 2 O Time
Quick Quiz: True or false: An enzyme makes a reaction that wouldn t have happened A) True B) False 20
Quick Quiz: The difference between the amount of energy in reactants and the maximal amount of energy in the transition state is called A) Activation energy B) Free energy C) Catalyst D) Potential energy 21
Photosynthesis C 6 H 12 O 6 22
Occurs in chloroplasts Outer membranes (2) Photosynthesis Thylakoid membrane system Stroma 23
Two distinct events Photosynthesis Light-dependent reactions (light reactions) Occurs in thylakoids of chloroplasts Energy from sunlight used to generate ATP & NADPH Splits H 2 O, releasing O 2 as a byproduct Light-independent reactions (dark reactions) Occurs in stroma of chloroplasts Uses CO 2, ATP & NADPH to synthesize glucose 24
Process summary Photosynthesis 25
Photosynthesis How is light energy actually captured and converted into chemical energy? Photopigments capture photons of light Chlorophylls (a, b) Accessory pigments (carotenoids, phycobilins) Electron carriers transfer energy to form ATP & NADPH Calvin-Benson cycle uses the ATP & NADPH to fix CO 2 into sugars (glucose) 26
Quick Quiz: Which stage of photosynthesis requires carbon dioxide? A) Light-dependent reactions B) Light-independent reactions 27
Quick Quiz: True or false: the goal of photosynthesis is to produce oxygen. A) True B) False 28
Light-Dependent Reactions Photopigments & the Electromagnetic Spectrum 29
Photopigments & the Electromagnetic Spectrum 30
Englemann s Experiment 31
Light Capture & Energy Transport Two photosystems for capturing light energy 32
Quick Quiz: In a plant cell, which of the following is NOT where you would find chlorophyll? A) Photosystem I B) Photosystem II C) ATP synthase D) Thylakoid membrane 33
Quick Quiz: What is the final product of the light reactions? A) glucose B) starch C) ATP D) NADPH E) C and D only F) All of the above 34
Light-Independent Reactions Calvin-Benson cycle Occurs in stroma of chloroplast Use ATP & NADPH generated during light-dependent reactions Carbon fixation 6 CO 2 + 6 RuBP 1 glucose Rubisco (enzyme) RuBP = ribulose bisphosphate 35
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Process summary Photosynthesis ATP + NADPH C 6 H 12 O 6 37
Quick Quiz: How many carbon atoms does RuBP have? (Just press the number on your keypad that corresponds with your answer.) 38
Quick Quiz: Which of these is a product of the Calvin-Benson cycle (aka the dark-reactions or lightindependent reactions ) A) ATP B) glucose C) NADPH D) CO 2 39
Variations to Photosynthetic Systems in Plants Differences in environments (light intensity, temperature, rainfall, soil conditions, etc) can affect how photosynthesis proceeds in plants How to deal with hot, dry conditions 40
Stomata Allow gas exchange through leaves (O 2, CO 2, H 2 O) Close in hot dry weather to prevent excess water loss Causes increase in O 2 levels; decrease in CO 2 levels Triggers photorespiration (bad news!) 41
C3 Plants E.g., evergreen trees (temperate zones) With stomata closed Rubisco fixes O 2 when CO 2 levels drop Efficiency reduced by 1/2 42
C4 Plants E.g., grasses, corn, tropical plants Two carbon fixation steps Each fixed in different types of cells Maintain higher internal CO 2 levels in the cells that make sugar than C3 s Lose less water, make more glucose than C3 plants during hot/dry conditions 43
CAM Plants E.g., cactus, desert plants Stomata close during the day and open at night Carbon fixation occurs at night Most efficient under hot/dry conditions 44
Quick Quiz: Which of the following plants uses a 4-carbon molecule in the Calvin cycle? A) Corn B) Douglas fir C) Saguaro cactus D) A and B E) A and C 45
The Circle of Life 46
The Circle of Life 36 ATP 47
Aerobic Respiration C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + 36 ATP glucose oxygen carbon dioxide water 48
Aerobic Respiration Involves 3 linked processes Glycolysis Citric acid cycle TCA (tricarboxylic acid cycle) / Krebs cycle Oxidative phosphorylation Respiratory transport chain / electron transport chain ATP synthase 49
Aerobic Respiration 50
Glycolysis Sugar splitting Occurs in cytoplasm Net reaction: 1 glucose 2 pyruvate + 2 ATP + 2 NADH C 6 H 12 O 6 C 3 H 3 O 3 51
Glycolysis (part 1) 52
Glycolysis (part 2) 53
Glycolysis Bottom line 1 glucose 2 pyruvate + 2 ATP + 2 NADH Glucose (6 C) split into 2 molecules of pyruvate (3C) To TCA cycle 54
Glycolysis Bottom line 1 glucose 2 pyruvate + 2 ATP + 2 NADH Glucose (6 C) split into 2 molecules of pyruvate (3C) Uses 2 ATP, produces 4 ATP net yield of 2 ATP Available for immediate energy needs 55
Glycolysis Bottom line 1 glucose 2 pyruvate + 2 ATP + 2 NADH Glucose (6 C) split into 2 molecules of pyruvate (3C) Uses 2 ATP, produces 4 ATP net 2 ATP Produce reducing potential (NADH) To electron transport (oxidative phosphorylation) 56
Quick Quiz: The end result of glycolysis is 2 molecules of. A) Carbon dioxide B) Oxygen C) Glucose D) Pyruvate 57
Quick Quiz: True or false: Plant cells have mitochondria. A) True B) False 58
TCA Cycle Occurs in mitochondria Matrix (inner compartment) Net reaction: 2 pyruvate 6 CO 2 + 2 ATP + 8 NADH + 2 FADH 2 59
60 TCA Cycle
TCA Cycle Bottom line 2 pyruvate 6 CO 2 + 2 ATP + 8 NADH + 2 FADH 2 Glucose now completely oxidized to CO 2 Diffuses from cell Generates lots of reducing potential (NADH, FADH 2 ) To electron transport chain (ETC) 61
Quick Quiz: Which of the following is NOT a product (or byproduct) of the TCA cycle? A) NADH B) FADH 2 C) ATP D) Pyruvate E) CO 2 62
Oxidative Phosphorylation Occurs in mitochondria (inner membrane) Most efficient system for ATP generation Net reaction: 10 NADH + 2 FADH 2 + 6 O 2 32 ATP + 6 H 2 O 63
Oxidative Phosphorylation 64
Oxidative Phosphorylation ATP ADP + P i INNER COMPARTMENT 65
Oxidative Phosphorylation 66
Bottom line Oxidative Phosphorylation 10 NADH & 2 FADH 2 + 6 O 2 32 ATP + 6 H 2 O Use energy carriers (NADH, FADH 2 ) from glycolysis and TCA cycle to generate ATP O 2 is the terminal acceptor for the transferred electrons Involves ATP synthase Uses H + concentration gradient 67
Aerobic Respiration 68
Quick Quiz: Where is the electron transport chain located? A) Cytoplasm B) Mitochondrial matrix C) Outer mitochondrial membrane D) Inner mitochondrial membrane E) Intermembrane space (outer compartment) 69
Quick Quiz: What would happen to oxidative phosphorylation if oxygen were not available? A) Oxidative phosphorylation would cease B) Oxidative phosphorylation would increase C) Oxidative phosphorylation would occur at the same rate 70
Anaerobic Respiration ATP generation in the absence of O 2 Involve terminal electron acceptors other than oxygen E.g., O-containing salts (nitrates, nitrites, sulfates, sulfites) Anaerobic bacteria 71
Anaerobic Respiration ATP generation in the absence of O 2 ATP produced through glycolysis with lactic acid and/or ethanol and CO 2 as end products Fermentation Lactic fermentation Alcoholic fermentation Decreased efficiency; have to deal with by-products 72
Lactic Fermentation 73
Alcoholic Fermentation 74
Alternate Energy Sources & Biosynthesis 75
Quick Quiz: True or False The TCA cycle can only be used to oxidize (process) pyruvate. A) True B) False 76