Energy and Life • What is energy? Energy is the ability to do work! • Sunlight is the main energy source for life on Earth. 1. Cells use chemical energy in the form of a chemical compound called ATP, or adenosine triphosphate. a. ATP contains: i. ____________________________________________ ii. ____________________________________________ iii. ___________________________________________ b. The bonds between the _____________________________________________ store and release energy • ATP transfers energy from the breakdown of food molecules to cell functions. • Energy is released when a phosphate group is_________________ • ADP is changed into ATP when a phosphate group is added _________________ is the basic energy source of all cells • Organisms break down carbon-based molecules to produce ATP. • ________________________________are the molecules most commonly broken down to make ATP. • not stored in large amounts • up to _____________________________ from one glucose molecule Storing Energy • Energy is stored in ATP, ADP, adenosine diphosphate, is similar to ATP but has _______________ phosphate groups instead of three. When a cell has energy available, it can store small amounts by adding a ______________________________________ to ADP making ATP 1. When a chemical bond between the 2nd and 3rd phosphates of ATP is broken, _________________________________ 2. ATP has enough energy to power a variety of cellular activities A. active transport across the selectively permeable cell membrane B. protein synthesis 4. ATP is a good short term energy storage that is recycled between ADP and ATP. Cells have only a small amount of ATP. a. It is more efficient for cells to store energy as glucose. b. When cells need energy they make ATP from ADP using energy from glucose. • ____________________________________ store the most energy. – 80 percent of the energy in your body – about 146 ATP from a triglyceride • ____________________________ are least likely to be broken down to make ATP. amino acids not usually needed for energy about the same amount of energy as a carbohydrate • • • • • • • What is photosynthesis? The process in which plants use the energy of the sun to convert ________________________________________________________________into high-energy carbohydrates (sugars and starches) and oxygen (a waste product). ______________________ is a molecule that absorbs light energy. In plants, chlorophyll is found in organelles called ______________________________________ Photosynthesis takes place in two parts of chloroplasts. – ________________________ – ________________________ The light-dependent reactions capture energy from sunlight. – take place in_________________________________________ – water and sunlight are needed – chlorophyll absorbs energy – energy is transferred along thylakoid membrane then to light-independent reactions – ____________________________ is released The light-independent reactions make ____________________________________. – take place in stroma – needs ________________________________________ from atmosphere – use energy to build a sugar in a cycle of chemical reactions The equation for the overall process is: 6CO2 + 6H2O C6H12O6 + 6O2 Light and Pigments • Photosynthesis requires: – _______________________________,_____________________________ and ____________________ – chlorophyll (a pigment molecule in chloroplasts; two types) • chlorophyll a • chlorophyll b Factors affecting photosynthesis _____________________________, _________________________________, _____________________ Inside a Chloroplast • Photosynthesis takes place inside ________________________________ • Chloroplasts contain: – ______________________________ saclike photosynthetic membranes containing pigments – ______________________________ (singular: granum): stacks of thylakoids – _____________________________: region of chloroplasts outside of the thylakoid membranes – inner membrane – outer membrane Photosystem II captures and transfers energy. • _________________________ absorbs energy from sunlight • __________________________________ enter electron transport chain • ___________________________ molecules are split • ____________________________ is released as waste • hydrogen ions are transported across _______________________________________ Electron Carriers • Sunlight excites electrons in chlorophyll, causing them to gain energy. • An excited electron is like a hot coal, and cannot be easily carried from one place to another- a protein called an ___________________________________________ is required to transport excited electrons. Electron transport: An electron carrier molecule can accept a pair of high-energy electrons and transfer them to another molecule. – Electron transport chain: Series of electron carriers – Example: NADP+ (nicotinamide adenine dinucleotide phosphate) NADP+ + 2 electrons + H + NADPH __________________________ can carry high-energy electrons to other chemical reactions in the cell that need energy • • • • Photosystem I captures energy and produces energy-carrying molecules. chlorophyll absorbs energy from sunlight energized electrons are used to make ________________________ NADPH is transferred to ___________________________________ reactions Light Dependent Reactions • The light-dependent reaction ___________________, produce ________________________ gas as waste, and converts ADP and NADP+ into ______________________ and _______________________. • The second stage of photosynthesis uses energy from the first stage to make __________________________. • Light-independent reactions occur in the ________________________ and use _______________ molecules. • A molecule of glucose is formed as it stores some of the energy captured from sunlight. • carbon dioxide molecules enter the _________________________________ • energy is added and carbon molecules are rearranged • a high-energy three-carbon molecule leaves the cycle • two three-carbon molecules bond to form a _____________________________ • remaining molecules stay in the cycle Light Dependent Reactions 1. Light hits Photosystem II in the thylakoid membranes. Two electrons are excited and these excited electrons are passed onto the electron transport chain a. To replace the lost electrons, the thylakoid membrane obtains low-energy electrons by splitting water 2H2O 4H+ + O2 + 2 e• The O2 is released as waste • The hydrogen ions (4H+) are released inside the thylakoid membrane 2. Electron transport chain (ETC) a. Electrons are passed from Photosystem II to Photosystem I from one electron carrier to the next until they reach Photosystem I b. Energy from the electrons is used by the electron carriers in the ETC to force H+ ions from the stroma into the inner thylakoid space- buildup of H+ will be used to drive ATP synthase 3. Light hits Photosystem I a. Pigments in Photosystem I use energy from light to energize two electrons, making them high-energy b. They are passed to NADP+ Reductase which catalyzes the reaction of NADP+ take combining with the high-energy electrons and hydrogen ions (H+) to become NADPH 4. Hydrogen Ion Movement – The inside of the thylakoid membrane fills up with positively charged hydrogen ions (H+) as electrons are passed from Photosystem II to I – ATP synthesis • The thylakoid membrane contains a protein called ATP synthase that spans the membrane and allows H+ ions to pass through it • As H+ ions pass through ATP synthase, the protein rotates and binds ADP and a phosphate group to produce ATP. Light-independent reactions (The Calvin Cycle) • During the Calvin cycle, plants use ATP and NADPH from the lightdependent reactions to produce high-energy sugars for long-term storage. • The Calvin cycle does NOT require light. • The Calvin Cycle: (4 Steps) 1. CO2 enters the cycle – Six carbon dioxide molecules enter and combine with six 5-Carbon molecules. – Result: 12 3-carbon molecules • Energy input – The 12 3-carbon molecules are converted into high energy forms using ATP and NADPH • During this process, 12 ATP 12 ADP • During this process, 12 NADPH 12 NADP+ • 6-carbon sugar produced from two 3-carbon molecules removed to produce sugar • 5-carbon molecules regenerated – 10 remaining 3-carbon molecules converted into six 5-carbon molecules – This requires 6 ATP 6 ADP – These 5-carbon molecules can be reused in step A.