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Chapter 8 Photosynthesis Autotrophs vs. Heterotrophs Autotrophs are organisms that can make their own food ◦ Use light energy from the sun to produce ◦ Plants are an example Heterotrophs cannot use the sun’s energy directly ◦ Obtain energy from the foods they eat ◦ Animals and mushrooms are examples Autotrophs vs. Heterotrophs Energy ATP – Adenosine triphosphate – is the molecule cells use to store and release energy. Be able to draw it. Energy is released when the bond is broken between the last two phosphates. Adenosine ADP – Adenosine diphosphate AMP – Adenosine monophosphate Energy Energy Adding a phosphate group to ADP allows the organism to store energy ◦ ATP is like a fully charged battery ◦ ADP is like a partially charged battery Energy Energy is used for: 1. Active transport: Na+ is pumped out and K+ into the cell 2. Motor proteins that move organelles 3. Synthesis of proteins, nucleic acids, lipids… 4. Produce light (firefly) 5. Cell reproduction and more Energy Glucose is better for long term storage than ATP A single molecule of glucose stores 90 times the chemical energy of a molecule of ATP Most cells only have a small amount of ATP, only enough to last for a few seconds of activity What is Photosynthesis? Photosynthesis is the process in which light, water, and carbon dioxide (CO2) is made into sugar and oxygen (O2) Carbon dioxide + water 6CO2 + 6H2O sugar + oxygen C6H12O6 + 6O2 Photosynthesis Chlorophyll a and Chlorophyll b are pigments in the chloroplast that absorb light of the visible spectrum, except for green light. They reflect green, thus the leaf looks green. Photosynthesis Photosynthesis takes place in the chloroplasts ◦ Chloroplasts have stacks of thylakoids (saclike photosynthetic membranes) ◦ Proteins in thylakoids organize chlorophyll and other pigments into photosystems, which are the light-collecting units Light-dependent reactions Take place in the thylakoid membranes Convert light energy to ATP and NADPH Split H2O and release O2 Electron transport chain connects the two photosystems to make an H+ gradient across the thylakoid membrane (ATP synthase uses this force to make ATP). Uses a proton (H+) pump. Light-dependent reactions Calvin cycle reactions Take place in the stroma Use ATP and NADPH to convert CO2 to sugar Return ADP, inorganic phosphate, and NADP+ to the light reactions Calvin cycle reactions Photosynthesis Factors affecting photosynthesis Water (required raw material) ◦ Plants in dry climates have a waxy coating to prevent water loss CO2 concentration (required raw material) Temperature: enzymes function best between 0o C and 35o C Light intensity ◦ Plants can reach a maximum rate of photosynthesis with light intensity (varies between plant type) Chapter 9 Cellular Respiration Chemical Energy How much energy is in food? ◦ One molecule of glucose contains 3811 calories of heat energy ◦ A calorie is the amount of energy needed to raise the temperature of one gram of water one degree Celsius ◦ The Calorie (food labels) is actually 1000 calories Chemical Energy The beginning of turning food into energy is glycolysis (produces small amount of energy) If oxygen is present 2 other pathways occur to produce more energy If oxygen is not present, 1 different pathway occurs Energy Pathways Aerobic – requires oxygen ◦ Also called cellular respiration Anaerobic – does not need oxygen ◦ Fermentation – name for anaerobic pathway following glycolysis (if oxygen is not present). (The term fermentation includes glycolysis). What is Cellular Respiration? Cellular Respiration (video) Cellular respiration - the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen. Glucose + oxygen carbon dioxide + water + energy C6H12O6 + 6O2 6CO2 + 6H2O + ATP What is Cellular Respiration? Oxygen Carbon dioxide Carbon dioxide Water Cellular Respiration Steps of cellular respiration: 1. Glycolysis – one glucose is broken in half to make 2 pyruvic acids. Anaerobic. Occurs in cytoplasm. 2. Krebs cycle – pyruvic acid is broken down into CO2 and energy. Aerobic. Occurs in mitochondrion. Also called citric acid cycle. 3. Electron transport chain – using a series of proteins, the electrons from the Krebs Cycle and glycolysis to convert ADP to ATP. Glycolysis NADH passes energy from glucose to the electron transport chain Energy Pathways Aerobic – requires oxygen ◦ Also called cellular respiration Anaerobic – does not need oxygen ◦ Fermentation – name for anaerobic pathway following glycolysis (if oxygen is not present). (The term fermentation includes glycolysis). Fermentation Two types of fermentation: Alcoholic fermentation: yeasts and some bacteria Pyruvic acid + NADH alcohol + CO2 + NAD+ Lactic acid fermentation: most organisms including us and many bacteria Pyruvic acid + NADH lactic acid + NAD+ Both processes regenerate NAD+ Lactic Acid Fermentation Kreb’s Cycle and ETC During the Kreb’s cycle pyruvic acid is broken down into carbon dioxide ◦ Occurs in the mitochondrion ◦ NADH and ATP is produced In the electron transport chain (ETC) high energy electrons (NADH, FADH2) is converted into ATP ◦ Hydrogen ions are pumped across membrane ◦ ATP synthase – enzyme (protein) that makes ATP using H+ gradient Cellular Respiration 1 glucose results in the production of 36 ATP net ◦ 34 more ATP than anaerobic processes ◦ 38% of the total energy in glucose, the other 62% is “lost” through heat ◦ More efficient than an automobile (25%-30%) 70-75% is lost to heat Energy Pathway Glycolysis No Oxygen Anaerobic respiration Fermentation 2 ATP, lactate or alcohol, and CO2 Oxygen Aerobic respiration Cellular respiration 36 ATP Cellular Respiration Cellular Respiration Energy Pathway Comparing photosynthesis, cellular respiration, & fermentation: Photosynthesis Cellular Fermentation Respiration Function Energy storage Energy release Energy release Location Chloroplasts Mitochondria Cytoplasm Reactants CO2 and H2O Glucose and O2 Glucose & NAD Products CO2 and H2O & ATP Alcohol & CO2 & ATP or Lactic acid & ATP Glucose and O2