Ms. Luaces, Honors Biology Cellular Reactions Ms. Luaces, Honors Biology

Photosynthesis What happens during the process of photosynthesis? Why is ATP useful to cells? What role do pigments & electron carriers play in photosynthesis? What are the reactants and products of photosynthesis? What factors affect photosynthesis?

8.1 Energy & Life Energy is the ability to do work Have to be able to obtain and use energy in many forms (light, heat, electricity, or chemical compounds) One of the most important compounds that cells use to store and release energy is called adenosine triphosphate (ATP)

8.1 Chemical Energy & ATP ATP is made up of: 1. Adenine 2. A 5-carbon sugar called ribose 3. 3 phosphate groups Sometimes seen as ADP (has 2 phosphates instead of 3, and can store small amounts of energy)

8.1 Chemical Energy & ATP ATP can easily release energy (by breaking chemical bonds) or store energy (by adding chemical bonds) between its phosphate groups to supply a basic energy source for all cells ADP will store energy when you add a phosphate ATP will release energy when you take away a phosphate

8.1 Chemical Energy & ATP How do we use the energy provided by ATP? Carry out active transport by pumping Na+ ions out of cells and pumping in K+ ions Contract muscles Build proteins & respond to signals Breathe

8.1 Chemical Energy & ATP ATP is NOT a good long-term storage molecule. Sugar molecules, like glucose, store 90 times the energy ATP does Heterotrophs (?) & Autotrophs (?) therefore are always looking to take in/make sugar or carbs to power their cells

8.2 Photosynthesis: An Overview Energy from the sun travels to Earth in the form of light. Plants gather it in light-absorbing molecules called pigments Plants principal pigment is chlorophyll Chlorophyll a & b are present, and capture blue-violet and red regions of the color spectrum

8.2 Photosynthesis: An Overview Photosynthesis takes place inside organelles called chloroplasts, which contain many thylakoids arranged in stacks Chlorophyll are found inside the thylakoid membranes The fluid portion of the chloroplast is known as the stroma

8.2 Photosynthesis: An Overview When chlorophyll absorbs light, a large fraction of that light energy is transferred directly to electrons in the chlorophyll molecule An electron-carrier accepts the electrons and transfers them, along with the energy, to another molecule Photosynthesis electron-carrier is known as NADP+

8.2 Photosynthesis: An Overview Photosynthesis uses the energy of sunlight to convert water and carbon dioxide (reactants) into high-energy sugars and oxygen (products) 6CO2 + 6H2O  C6H12O6 + 6O2 (light)

8.2 Photosynthesis: An Overview Photosynthesis involves 2 kinds of reactions: Light-dependent reaction Requires light and water (for electrons & hydrogen ions) Occurs in the thylakoids Oxygen is released as a byproduct Light-independent reaction Doesn’t require light Requires carbon dioxide, ATP & NADPH Occurs in the stroma Creates sugars and carbs

Let’s Get Funky! Create a song / rap / act / drawing showing the process of Photosynthesis. Your creative imagination should include: Light Leaf Chloroplast Thylakoid Chlorophyll Excited Electron NADP+ Sugar *** If you are doing an act, you MUST have a narrator!!

9.1 Cellular Respiration: Overview Organisms get the energy they need from food How much energy depends on the kind of food Energy is measured in calories: the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius Fats: 9 calories per gram Carbs & Proteins: 4 calories per gram

9.1 Chemical Energy & Food Food must be broken down gradually to control the release of energy and create compounds such as ATP to directly power the cell If we broke down food all at once, most of the energy would burn away in the form of heat

9.1 Cellular Respiration: Overview Cellular respiration is the process that releases energy from food in the presence of oxygen 6O2 + C6H12O6  6CO2 + 6H2O + Energy Notice anything??

9.1 Cellular Respiration: Overview Cellular respiration has 3 main stages: 1. Glycolysis: creates very little energy 2. Krebs cycle: creates a little more energy 3. Electron transport chain (ETC): creates the majority of the energy ; directly involves the world’s most powerful electron acceptor - Oxygen

9.1 Cellular Respiration: Overview Aerobic Anaerobic Requires oxygen Ex: Electron Transport Chain Doesn’t require oxygen Ex: Fermentation ** Glycolysis & Krebs don’t DIRECTLY use oxygen, but are involved with products/reactants of oxygen

9.1Where Do These Processes Occur? Cytoplasm Mitochondria Glycolysis Krebs Cycle Electron Transport Chain (ETC)

9.1 Cellular Respiration: Overview Cellular respiration is balanced by photosynthesis: the equations are reverse of each other One processes gives the reactants of the other

9.2 Glycolysis The first set of reactions in cellular respiration is Glycolysis (sugar-breaking). During glycolysis: 1 molecule of glucose (6 carbon molecule)  2 molecules of pyruvic acid (3 carbon molecule) Uses NAD+ as an electron acceptor to become NADH Remember, Glycolysis doesn’t require oxygen!

9.2 Glycolysis What does glycolysis produce? 2 ATP molecules NADH 2 pyruvic acid molecules

9.2 Krebs Cycle During Krebs, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions Also known as the citric acid cycle Pyruvic acid is converted into acetyl-coA and then into citric acid One molecule of glucose = 2 turns of the cycle Uses NAD+ & FAD as electron acceptors  NADH and FADH2

9.2 Krebs Cycle What are the products of Krebs cycle? 2 ATP molecules NADH & FADH2 Carbon dioxide

9.2 ETC The electron transport chain uses high-energy electrons from glycolysis & Krebs cycle to convert ADP & ATP NADH & FADH2 release their electrons, and as they pass down the line, they generate energy to spin something known as ATP synthase With each rotation, the enzyme grabs an ADP molecule and attaches a phosphate group, producing ATP Oxygen is directly involved here

9.2 ETC What are the products of ETC? 36 ATP (on average) Water

Let’s Visualize Create a table that lists the 3 steps of cellular respiration and include: Where does it take place? Directly requires oxygen? What are the reactants? What are the products? Glycolysis Krebs Cycle ETC

9.2 Cellular Respiration All together, cellular respiration produces about 36 ATP, water, and carbon dioxide. The rest of the energy is lost in the form of heat

9.3 Fermentation In the absence of oxygen, fermentation releases energy from food molecules by producing ATP Cells convert NADH to NAD+ by passing high-energy electrons back to pyruvic acid in the cytoplasm 2 types: Alcoholic and Lactic Acid Fermentation

9.3 Fermentation Alcoholic Lactic Acid Used by yeasts & microorganisms Causes bread dough to rise Pyruvic acid + NADH  Alcohol + CO2 + NAD+ Used by bacteria & humans (when?) Creates cheese, yogurt, buttermilk Pyruvic acid + NADH  Lactic acid + NAD+

9.3 Fermentation 3 main sources of ATP: ATP already in the muscles: few seconds of intense activity ATP made by lactic acid fermentation: short quick bursts of energy ATP made by cellular respiration: exercise longer than 90 seconds

Let’s Practice! Study Workbook A – Pg. 97-99 Work with a buddy, answers only, one sheet of paper