Chap 8- Photosynthesis Energy- the ability to do work All living organisms must obtain and use energy to survive Autotrophs: obtain energy from nonliving sources Plants and some other types of organisms able to use light energy from the sun to produce food

Chap 8- Photosynthesis Heterotrophs- must obtain energy from an outside source (cannot make own) All organisms must release energy stored chemically by autotrophs Energy stored in bonds formed between atoms When bonds are broken (or new ones formed), energy released

Chap 8- Photosynthesis Adenosine Triphosphate (ATP)- source of energy for the cell To store energy: Adds a phosphate onto ADP (diphosphate) Forms ATP To release energy: Breaks high-energy bond to form ADP

Chap 8- Photosynthesis Not a good long-term storage molecule Only keep a small amount in the cell Single molecule of glucose stores 90x the energy found in ATP Cell regenerates ATP from ADP as needed Uses energy stored in food to do this

Chap 8- Photosynthesis In the presence of light, plants transform carbon dioxide and water into carbohydrates Release oxygen in the process General equation: 6CO2 + 6H2O  C6H12O6 + 6O2 Carbon dioxide + water light sugars + oxygen

Chap 8- Photosynthesis Plant cells contain light-absorbing chemicals, called pigments, that absorb certain wavelengths of visible light Principle pigment is chlorophyll (a & b) Absorb light in the blue/violet and red/orange wavelengths Accessory pigments absorb additional wavelengths and pass onto chlorophyll

Chap 8- Photosynthesis Light-absorbing pigments found in closed sacs called thylakoids Pigments are embedded in the thylakoid membrane Also embedded: proteins and enzymes necessary for photosynthesis Proteins, pigments, and enzymes together make up photosystems

STROMA GRANA

Chap 8- Photosynthesis Process of photosynthesis involves three energy conversions: Absorption of light energy Conversion of light energy into chemical energy Storage of chemical energy in the form of sugars

Chap 8- Photosynthesis Light-dependant reactions: pigment molecules absorb light energy and convert it to ATP (light energy  chemical energy) -Takes place on thylakoid membrane Chemical energy (ATP) used to make 6-carbon sugars from CO2 – reaction known as the Calvin cycle -Takes place in stroma (space surrounding thylakoids inside chloroplasts)

Chap 8- Photosynthesis Electron Carriers When sunlight excites electrons in chlorophyll, electrons gain great amount of energy High-energy electrons require special carrier molecules These molecules transfer electrons (and their energy) to another molecule

Chap 8- Photosynthesis Process called electron transport Group of carriers known as the electron transport chain NADP+ : primary carrier molecule Accepts 2 high-energy electrons and a H+ ion to form NADPH One way of converting light energy into chemical energy

Chap 8- Photosynthesis Light-Dependant Reactions Use energy from sunlight to produce energy carriers ATP and NADPH (from ADP and NADP+) Oxygen gas is a by-product of these reactions (created by breaking water) Two reaction centers: Photosystem I Photosystem II

Chap 8- Photosynthesis Electrons passed along series of proteins/enzymes called electron transport chain; taken at end by NADP+  NADPH Hydrogen ions pumped outside membrane; conc. gradient used to produce ATP ATP synthase: enzyme in chain that produces ATP from ADP

Chap 8- Photosynthesis The Calvin Cycle Light-independent reactions Plants use energy in ATP and NADPH to form long-term energy storage molecules ATP & NADPH  high-energy sugars

Chap 8- Photosynthesis 1. 6 CO2 molecules enter cycle Combine with 6 5-carbon molecules Result = 12 3-carbon molecules 2. 12 3-carbon molecules converted into higher-energy forms Energy for conversion comes from ATP & NADPH

Chap 8- Photosynthesis 3. Two of the twelve 3-carbon molecule are removed from cycle Used to make sugars and other molecules 4. Remaining ten 3-carbon molecules converted back into six 5-carbon molecules to start cycle again Sugars used as building blocks & for energy by plants

Chap 8- Photosynthesis Rate (activity per unit of time) of photosynthesis affected by: Concentrations of O2 and CO2 Temperature Light intensity Availability of Water

Chapter 8 Review Ques. Pg. 217: B- plants A- sugars and O2 B- ATP B- van Helmont D- H2O & CO2 C- Reflects green A- sugars and O2 D- chloroplasts A- light absorption B- NADPH A- Calvin cycle

Chapter 8 Review Ques. Pg. 219: A- chlorophyll D- yellow-green B- sugars A C- green E- absorption of light energy C- oxygen D- yellow-green B- contain several pigments D- chloroplasts

Chap 9- Cellular Respiration Chemical Energy & Food 1g of glucose = 3811 calories of heat energy Food energy not released all at once: released gradually Process begins with chemical pathway called glycolysis (small amount of energy) If oxygen present: leads to one pathway If no oxygen present: leads to different pathway

Chap 9- Cellular Respiration Overview of Cellular Respiration When oxygen is present: -glycolysis  -Krebs cycle  -electron transport chain Three pathways make up process called cellular respiration

Chap 9- Cellular Respiration Releases energy from glucose and other food molecules in the presence of oxygen General equation: C6H12O6 + 6O2  6CO2 + 6H2O + E glucose + oxygen  carbon dioxide + water + energy Cell releases energy in little bits Captures the energy in ATP

Chap 9- Cellular Respiration Glycolysis Process which breaks a molecule of glucose in half Produces two molecules of pyruvic acid Cell uses 2 ATP to produce 4 ATP 2 NADH (electron carrier molecule) produced from NAD+

Chap 9- Cellular Respiration Fermentation Anaerobic process (occurs without oxygen) Two types: Alcoholic fermentation- yeast cells and some bacteria Pyruvic acid + NADH  alcohol + CO2 + NAD+

Alcoholic Fermentation

Chap 9- Cellular Respiration Lactic acid fermentation- in muscles during heavy exercise; unicellular organisms Pyruvic acid + NADH  lactic acid + NAD+ Microorganisms used to make variety of food products

Lactic Acid Fermentation

Chap 9- Cellular Respiration Aerobic pathways: Krebs cycle and electron transport chain MUST have oxygen to occur Oxygen acts as the final electron acceptor in process

Chap 9- Cellular Respiration Krebs Cycle Pyruvic acid broken down into carbon dioxide in series of energy-extracting steps 1. Begins when pyruvic acid enters the mitochondrion One carbon atom from pyruvic acid becomes CO2 Other two form acetyl-CoA (acetyl = 2 carbon atoms)

Chap 9- Cellular Respiration Acetyl group added to a 4-carbon molecule to form citric acid (6-carbon molecule) 2. Cycle continues… Citric acid broken down into a 4-carbon molecule (cycle starts again) In process: 2 CO2 molecules released 4 NADH produced 1 ATP produced 1FADH2 produced !!**per molecule of pyruvic acid**!!

Chap 9- Cellular Respiration Tally so far… Glycolysis: 2 ATP 2 NADH Krebs Cycle: 2 ATP 8 NADH 2 FADH2 Total: 4 ATP 10 NADH 2 FADH2

Chap 9- Cellular Respiration Electron Transport ETC (electron transport chain) uses the high-energy electrons from the Krebs cycle to convert ADP into ATP 1. ETC located on inner mitochondrion membrane Electrons passed along series of proteins Oxygen accepts electrons (and two H+) and forms H2O at end of chain

Chap 9- Cellular Respiration 2. With every two electrons, H+ ions are pumped across membrane Builds up concentration gradient across membrane 3. ATP synthase allows H+ ions across membrane Uses energy of gradient to convert ADP to ATP (3 ATP for each pair of H+ ions)

Chap 9- Cellular Respiration Final Tally Glycolysis: 2 ATP 2 NADH Krebs Cycle: 2 ATP 8 NADH 2 FADH2 ETC: 32 ATP (from NADH & FADH2) Total: 36 ATP from one molecule of glucose

Chap 9- Cellular Respiration 38% efficiency of extracting energy from glucose Gas engine- 6%-8% efficiency Rest is lost as heat energy

Chap 9- Cellular Respiration Comparison of Photosynthesis & Cellular Respiration Photosynthesis “deposits” energy Cellular respiration “withdraws” energy Photosynthesis removes carbon dioxide from atmosphere, adds oxygen Cellular respiration removes oxygen from atmosphere, adds carbon dioxide

Chap 9- Cellular Respiration General equation for Photosynthesis: 6CO2 + 6H2O  C6H12O6 + 6O2 General equation for Cellular Respiration: C6H12O6 + 6O2  6CO2 + 6H2O

Chapter 9 Review Ques. Pg. 2:

Chapter 9 Review Ques. Pg. 2: