Energy for life’s activities Cellular Respiration Energy for life’s activities

Launch Lab Where did energy transformation occur in the lab? How do you know? The lab showed a transfer of energy in the chemical form. How does this relate to cells?

Energy and Cells What is energy? The ability to do work Light, chemical, elastic, mechanical, heat How do cells get the energy they need? Food Anything else?

Main Idea All living organisms use energy to carry out all biological processes “The City That Never Sleeps” Objectives: Laws of Thermodynamics Autotrophs and Heterotrophs ATP- what is it and how does it work? Fig. 8.1 Timeline

Transforming Energy Even though you might be sleeping, your cells are still working Breaking down substances, transporting things across a cell membrane, transmitting genetic info Cells require energy- the ability to do work Thermodynamics studies the flow and transfer of energy

Laws of Thermodynamics 1. Conservation of Energy Stored food is converted to chemical energy when you eat, but mechanical energy run or play ball 2. Entropy Energy cannot be converted without losing some of it (energy) Entropy is the measure of that energy loss Usually, the lost energy is heat Example: Food Chains

Autotrophs and Heterotrophs Autotrophs- Make their own food Heterotrophs-need to ingest food to obtain energy Fig. 8.2- almost all of animal energy originates from the sun and flows through autotrophs

Metabolism A cell’s chemical reactions = metabolism Usually, the product of one reaction is the reactant for the next reaction This is called a metabolic pathway 2 Types of M. Pathways: Catabolic: release energy by breaking down large molecules Anabolic: uses the energy released by catabolic to build large molecules from small ones Metabolism

Metabolism Photosynthesis: anabolic pathway where light is converted to chemical energy for the cell Equation: 6CO2 + 6H2O -light-> C6H12O6 + 6O2 Cellular Respiration: catabolic pathway where organic molecules are broken to release energy for the cell C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy Fig. 8.3

ATP- The Unit of Energy Adenosine triphosphate (ATP) is the most important biological molecule that provides energy What does it look like? Nucleotide made with an adenine base, ribose sugar and 3 phosphate groups Adenine Ribose P P P

ATP What does it do? Compare the function of ATP to a car battery. When the bond between the 2nd and 3rd phosphate are broken, it releases energy This forms ADP (adenosine diphosphate) and a free phosphate group Fig. 8.4 Compare the function of ATP to a car battery.

Did we accomplish our objectives? Laws of Thermodynamics Autotrophs and Heterotrophs ATP- what is it and how does it work? All living organisms use energy to carry out all biological processes

Section 8.2- Photosynthesis Main Idea: Light energy is trapped and converted into chemical energy during photosynthesis Objectives: Summarize photosynthesis What does chloroplast do for the cell? How does the electron transport chain work?

Connection to Real World? Energy is transformed all around us Can you think of any examples? How do humans benefit from photosynthesis? How do plants benefit? Photosynthesis

Photosynthesis Goal: Autotrophs make glucose by photosynthesis (sugar) Recall the equation! 6CO2 + 6H2O -light-> C6H12O6 + 6O2 Photosynthesis Two Stages: Light dependant reactions Light is absorbed and turned into energy as ATP and NADPH Light independent reactions ATP and NADPH are used to make glucose The glucose is used to make carbohydrates

Photosynthesis and Chloroplast Before we can talk about the details, we need to know more about chloroplast 2 main compartments of chloroplasts: Thylakoid: flattened sacs that are arranged in stacks called grana Stroma: fluid filled space outside the grana

Thylakoids Contain pigments Different pigments absorb different wavelengths of energy Chlorophylls are the most common type of pigments Make the plant green Carotenoids are also pigments Produce the red and orange colors As trees stop producing chlorophyll in the fall, the carotenoids become more visible

Phase One- Light Reactions Starts in the chloroplasts (which are mainly in the leaves of plants) Capture light Then, Electron Transport takes place

Electron Transport The thylaloid is key to energy efficiency How? Electron Transport It has a large surface area that provides space to hold lots of electron transport molecules and proteins called photosystems (Photosystems are proteins!!) What does ET do? Converts ADP to ATP Converts NADP+ to NADPH Overview of ET

The Electron Transport Process Light excites electrons in Photosystem II (a protein in the thylakoid) The light also causes a H2O to split and release an electron into the ET system, and a proton into the thylakoid Excited electrons move from photosystem II to an electron carrier in the thylakoid and then along the chain to photosytem I Photosystem I transfers the electrons to a protein called ferrodoxin The electrons lost by photosystem I are replaced by the electrons shuttled from photosystem II Ferrodoxin transfers the electrons to the new carrier, NADP+, which forms NADPH What’s NADPH? Energy storing molecule ETC Animation

At the Same Time… Chemiosmosis also produces ATP The H+ left over from the break down of water drives ATP synthesis The H+ accumulate in the thylakoid space Low H+ in the stroma causes the H+ from the thylakoid to flow to the stroma and ATP is formed here by adding a phosphate to ADP Fig. 8.8 Overview of ET Burning Fossil Fuels How does this impact us?

Phase Two of Photosynthesis- Calvin Cycle In Phase One- ATP and NADPH were made and both provide energy for the cell, but not for long periods of time. So, the cell has to rely on another phase of photosynthesis to help create energy- the Calvin Cycle Phase two is AKA Light Independent reactions Dark Reactions The Calvin Cycle helps store energy as glucose Fig. 8.9 The Calvin Cycle spins many time to produce glucose (6)

Calvin Cycle Carbon Fixation: 6 CO2 molecules combine with 6 5-C molecules (RuBP) to form 12 3-C molecules called 3-Phospoglycerate (3-PGA) The energy stored in ATP and NADPH is transferred to the 3-PGA to form G3P – a sugar (glyceradldehyde 3-phosphates) which are high energy molecules ATP is now ADP and NADPH is now NADP+ 2 G3P molecules leave the cycle to be used for making glucose outside of the chloroplast Rubisco (enzyme) converts the rest of the 10 G3P molecules into 5-C molecules (RuBP) RuBP combine with new CO2 molecules to continue the process Calvin Cycle

Alternatives to Photosynthesis? What if water or CO2 weren’t available? C4 Pathway: corn and sugar cane CAM Pathway: desert plants and salty environment plants Both help plants deal with a lack of water but still take in CO2

Review Photosynthesis What’s the goal? When is this accomplished? What’s the chemical equation? Section 8.2: Main Idea- Light energy is trapped and converted into chemical energy during photosynthesis Objectives: Summarize photosynthesis What does chloroplast do for the cell? How does the electron transport chain work?

Section 3- Cellular Respiration Main Idea: Living Organisms obtain energy by breaking down organic molecules during cellular respiration Objectives: Summarize the stages of Cellular Respiration ID the role of electron carriers Compare alcoholic fermentation and lactic acid fermentation

Connection How to birds and butterflies that fly south for the winter find the energy to continue in flight? They are constantly feeding to maintain energy Humans need reliable food sources, too Video

Overview of Cellular Respiration Organisms gain energy from cellular respiration Function: harvest electrons from glucose and use the energy to make ATP Equation? C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy Two Phases: Glycolysis is anaerobic (no oxygen) Aerobic process: Requires oxygen Involves the Krebs Cycle Involved Electron Transport

Cellular Respiration Compound Glycolysis ATP No oxygen Oxygen Fermentation Aerobic Process ATP

Glycolysis Yields a small amount of ATP Starts with glucose and yields pyruvate Occurs in the cytoplasm Requires no oxygen 2 ATP and 2 NADPH are formed for each glucose that is broken down

Step One Two phosphate groups attach to glucose (6 carbon chain) Supplied by 2 ATP converted into 2 ADP P P Glucose ADP ADP

Step Two 6-carbon chain splits in half (because of an enzyme) So, there are 2 new molecules made P P

Step Three NAD+ collects an electron and a hydrogen to form NADH NADH moves to the mitochondria At the same time, another phosphate is added to each of the two groups by the NADH NADH NADH P P P P

Step Four The phosphates that were just added get broken off and picked up by ADP to make ATP Enzymes rearrange the 3 Carbon molecule, producing 2 molecules of pyruvate Four molecules of ATP are formed (2 net) Movie Animation ADP P P Pyruvate Pyruvate ADP

After Glycolysis? Glycolysis yields 2 ATP, 2 NADH and 2 pyruvate Most of the energy is in the pyruvate When oxygen is present, pyruvate is carried to the mitochondria (where it will be converted to CO2) Aerobic Respiration Krebs Cycle (AKA Citric Acid Cycle) Electron Transport

To Start Aerobic Respiration: Pyruvate (3 carbons) enters mitochondria to form acetyl CoA (acetyl CoA is a 2 carbon molecule) As a result, the extra carbon is released as CO2 This also turns NAD+ into NADH to be released This results in 2 CO2 and 2 NADHs (from 2 pyruvate molecules) Onto the Krebs Cycle NADH CO2 Acetyl CoA

Krebs Cycle- Step 1 Acetyl CoA combines with a 4 C compound to form a 6 C compound called citric acid Citric Acid

Step 2 Citric acid is broken down, releasing 2 CO2s and making 1 ATP, 3 NADH and 1 FADH2 NADH NADH FADH2 NADH CO2 ATP CO2

Step 3 Acetyl CoA and citric acid are made from those compounds in step 2 and the cycle continues Krebs Cycle Movie NADH FADH2 http://www.cliffsnotes.com/study_guide/Krebs-Cycle.topicArticleId-8741,articleId-8603.html to show how you yield 6 CO2s CO2 NADH Acetyl CoA ATP CO2 NADH

Adding It All Up 2 molecules of pyruvate were made in glycolysis This means the Krebs turns 1 time for each molecule of pyruvate (so it turns twice) Krebs net yield is 6 CO2, 2 ATP, 8 NADH and 2 FADH2 The NADH and FADH2 are used in the next stage of aerobic respiration Not very efficient! http://www.cliffsnotes.com/study_guide/Krebs-Cycle.topicArticleId-8741,articleId-8603.html to show how you yield 6 CO2s

Electron Transport – Supplies the Bulk of Energy E’ in H from NADH and FADH2 are passed along a conveyer belt of molecules The conveyer belt mvmt removes some of the energy from the e’ This energy is used to pump protons (from H) from outside of the mitochondria to the inside This creates a concentration gradient of protons (high p+ concentration inside the mitochondria) Concentration gradient of p+ drives the synthesis of ATP from ADP Another Video

Role of Oxygen in ETC ATP can be made only if electrons continue to move on the conveyer belt Molecules must “unload” the electrons to continue the process Oxygen serves as the final acceptor of e’ so they can be unloaded Oxygen also accepts p+ (from the H) supplied by NADH and FADH2 to make water O2 + 4 e- + 4 H+ 2H2O

ET Counting It Up ET produces: Prokaryotes 24 ATP In eukaryotes, one molecule of glucose produces 36 ATP total after Cellular Resp. Prokaryotes Don’t have mitochondria So, they go through cellular respiration in the cell membrane As a result, they gain 38 ATP

Energy Yield in Cellular Resp. Aerobic respiration makes ATP: 4 from glycolysis 2 from Krebs cycle + 32 from ETC 38 ATP - 2 ATP used in Glycolysis 36 ATP Net Animation

Summarizing Cellular Respiration Equation: Opposite of Photosynthesis What happens when? First glycolysis, then Cell Respiration Cell. Resp = Krebs Cycle + ETC C6H12O6 + 602 6CO2 + 6H2O + energy

Cellular Respiration Fat Video Glycolysis 4 ATP Pyruvate 2 ATP Krebs Cycle FADH2 NADH Electron Transport 32 ATP

Fermentation Some cells can function a short time without oxygen; some cells don’t need it at all (bacteria) These cells can rely on glycolysis to make ATP, but when they run out of NAD+ is isn’t replenished Fermentation: Occurs in cytoplasm Regenerates NAD+ and produces a small amount of ATP through glycolysis Two types: Lactic acid alcoholic

Lactic Acid Fermentation Enzyme converts pyruvate into lactic acid (3-carbon chain) Producing lactic acid means transferring electrons and protons from NADH to NAD+ NADH loses H to form NAD+ This is used in glycolysis Then it’s turned to NADH (cyclical) Lactic acid is used when the body can’t supply enough oxygen (such as strenuous exercise)

Lactic Acid Fermentation Essential in manufacture of foods Yogurt, sour cream and cheese Muscles collect it if they work too hard Makes your muscles sore

Alcoholic Fermentation Converts pyruvate into ethyl alcohol and CO2 NADH donates electrons and NAD+ is made, which is needed in glycolysis Wine and beer bread