Energy Metabolism Energy for life processes Energy is

Energy & Metabolism

Energy for life processes ■ ■ ■ Energy is the ability to cause matter to move or to change The ability to do work ■ Work for a cell includes ■ Growth & repair ■ Active transport ■ Reproduction ■ Synthesis of molecules ■ Lots of other stuff!!! Carbohydrates and lipids are the most important energy sources in foods you eat.

ATP ■ ATP: is a molecule that transfers energy from the breakdown of food molecules to cell processes

ATP/ADP cycle ■ ■ ■ Energy is released when phosphate bond is broken and a phosphate group is removed. The bond holding the third phosphate is unstable and easily broken. ATP ADP + Phosphate + Energy Adenosine triphosphate --- adensosine diphosphate Tri= 3; Di= dos= 2 Remember: Energy is in the bonds between phosphates, so if we break a bond we must get Energy as a product and ATP becomes ADP + Phosphate

ATP/ADP Cycle 3 3 2 1

ATP/ADP Cycle - Chemical bonds broken from food add P to ADP ATP; -when you work, ATP ADP + E (to do the work, chemical E in food regenerates ATP (That is why it is referred to as a cycle. )

- Foods that you eat do not contain ATP that your cells can use. - First, the food must be digested - The number of ATP molecules produced depends on the type of molecule that is broken down-carbohydrate, protein, or lipid. - Lipids store the most energy- fats store about 80% of the energy in your body 7

- Plant cells also need ATP - Plants do not eat their food, they make their own! - This is done through the process Photosynthesis- plants absorb energy from sunlight and make sugars. 8

Photosynthesis ■ ■ ■ Captures energy from sunlight to make sugars that store chemical energy. Therefore, directly or indirectly, the energy for almost all organisms begins as sunlight! Plants absorb visible light for photosynthesis-light that we see that appears white but is made up of several colors, or wavelengths, of light.

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■ ■ Chloroplasts –the membrane-bound organelles where photosynthesis takes place in plants. Contain pigments – pigments absorb light Energy ■ Chlorophyll (green pigment) is a catalyst for photosynthesis-it absorbs red and blue light; it reflects green light ■ it transfers light Energy into chemical energy

■ Chloroplast Has 2 major parts: 1. Thylakoid membrane 2. Grana 3. Stroma

3 Major Parts of a chloroplast ■ Grana (singular) ■ Stack of coin-shaped, membrane-enclosed compartments called thylakoids. ■ ■ Thylakoid membrane: contain chlorophyll, other lightabsorbing molecules, and proteins. Site where light-dependent reactions occur Stroma: the fluid that surrounds the grana inside a chloroplast. Site where light-independent reactions

■ ■ ■ Photosynthesis Chemical Reaction for photosynthesis: Reactants Products Water + Carbon dioxide Glucose + Oxygen 6 H 2 O + 6 CO 2 C 6 H 12 O 6 + 6 O 2

■ ■ ■ Photosynthesis - Overview Photo = light; synthesis = to make Uses 1% of solar E to convert to chemical E Occurs in 2 steps Step 1 Light-Dependent Reactions (Light Reactions): ■ I. II. III. Occurs within and across the thylakoid membrane Captures energy from sunlight (pigments absorb light) Water (H 2 O) taken into chloroplast & split Oxygen (O 2) which is released (this is what we breathe-it comes from the water that gets broken down) Energy carried along thylakoid membrane is transferred to molecules that carry energy, such as ATP -

Light Independent Rxn & Calvin Cycle Step 2: Calvin Cycle or Dark Reaction or Light Independent Reaction ■Occurs I. III. IV. in stroma uses energy from the light-dependent reactions to make ______. Carbon dioxide (CO 2) is taken in USED energy creates high-energy sugars (glucose) Glucose ( C 6 H 12 O 6) stores some of the energy captured.

Photosynthesis Stage 1 and 2 Stage 3

The First Stage of Photosynthesis Captures and Transfers Energy. - Photo- Light-Dependent Reactions - Main function: Capture and transfer energy - Water broken down —> H, electrons, and O 2 - Energy carriers- ATP and NADPH 20

Photosystem II and Electron Transport 1. ) ENERGY ABSORBED FROM SUNLIGHT - Chlorophyll and other light- absorbing molecules in the thylakoid membrane absorb energy from sunlight. - Energy then transferred to electrons. - High-Energy electrons leave the chlorophyll and enter an electron transport chain, a series of proteins in the membrane of the thylakoid. 21

Photosystem II and Electron Transport 2. ) WATER MOLECULES SPLIT - Enzymes break down water molecules - Hydrogen, Oxygen, and electrons are separated from each other. - Oxygen released as waste. 22

Photosystem II and Electron Transport 3. ) HYDROGEN IONS TRANSPORTED - Electrons move from protein to protein in the electron transport chain. - Their energy is used to pump H+ ions inside thylakoid against a concentration gradient. - H+ builds up inside thylakoid - Electrons move on to photosystem I. 23

Photosystem I and Energy-Carrying Molecules 4. ) ENERGY ABSORBED FROM SUNLIGHT - As in photosystem II, Chlorophyll and other light-absorbing molecules inside thylakoid membrane and absorb energy from sunlight. - Electrons are energized and leave the molecules. 24

Photosystem I and Energy-Carrying Molecules 5. ) NADPH PRODUCED - The energized electrons are added to a molecule called NADP+, forming a molecule called NADPH. - NADP+ - functions like ADP - NADPH- functions like ATP - NADPH- goes to light- independent reactions. 25

Photosystem I and Energy-Carrying Molecules 6. ) HYDROGEN ION DIFFUSION - Hydrogen ions flow through a protein channel in the thylakoid membrane. - Concentration of H+ ions are higher inside thylakoid than it is outside. - The difference in H+ ion is called a chemiosmotic gradient, which stores potential energy. 26

Photosystem I and Energy-Carrying Molecules 7. ) ATP PRODUCED - As the H+ ions flow through the protein channel , ATP synthase makes ATP by adding a phosphate group to ADP. 27

Summary of Light-Dependent Reactions - Energy is captured from sunlight and transferred to electrons that enter an electron transport chain. - Water are broken down into H+ ions, electrons, and oxygen. H+ ions and electrons are used in light-dependent reactions. - Energized electrons have two functions 1. ) Provide energy for H+ ion transport 2. ) Added to NADP+ to form NADPH - The flow of H+ ions through ATP synthase makes ATP. - PRODUCTS: Oxygen, NADPH, ATP. 28

Light-Independent Reactions ( Calvin Cycle) - They do not need sunlight. These reactions can take place anytime that energy is available. - Have to have NADPH and ATP from light reactions. - Calvin cycle uses carbon dioxide (CO 2) gas from the atmosphere and the energy carried by NADPH and ATP to make sugars. - synthesis= builds sugar molecules 29

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Light-Independent Reactions ( Calvin Cycle) 1. ) CARBON DIOXIDE ADDED - CO 2 molecules are added to 5 -carbon sugars already in the cycle. 6 -carbon molecules are formed. 2. ) THREE-CARBON MOLECULES FORMED - ATP and NADPH are used by enzymes to split the 6 -carbon molecules. 3 -carbon molecules are formed and rearranged. 31

Light-Independent Reactions ( Calvin Cycle) 3. ) THREE CARBON MOLECULES EXIT - Most of the 3 -carbon molecules stay in the Calvin Cycle, but one high-energy 3 carbon molecule leaves the cycle. - After two 3 -carbon molecules have left the cycle , they are bonded together to build a 6 -carbon sugar molecule such as glucose. 4. ) THREE-CARBON MOLECULES RECYCLED - ATP molecules are used to change the 3 -carbon molecules back to 5 - carbon molecules. - There added to new CO 2 molecules that enter the system. 32

Summary of the Light-Independent Reactions - Carbon dioxide enters the Calvin Cycle - ATP and NADPH from the light reactions transfer energy to the Calvin cycle - One high-energy three-carbon molecule is made for every three molecules of CO 2 that enter the cycle. - Two high-energy three-carbon molecules are bonded together to make a sugar. ( 6 CO 2 to make one 6 -carbon sugar). - PRODUCTS: six-carbon sugar ( such as glucose), NADP+, and ADP. 33