Energy and Life Energy the ability to do
Energy and Life
Energy = the ability to do work – Life on earth depends on a flow of energy – Cells need energy constantly to continue functioning.
• Energy comes in many forms – Examples: • Light • Heat • Energy stored in chemical compounds (like glucose)
Most cellular processes require the input of energy. Like what?
Examples: – Synthesis of new molecules • proteins, enzymes, DNA etc. – Breakdown of molecules • chemical digestion – Build new structures • membranes, organelles, etc. – Maintain Homeostasis • eliminate wastes, maintain body temp. , active transport, cell movement etc.
• Where do cells get this energy? – From food we eat – We measure the energy content of food in calories. – Certain reactions break down these molecules to release energy.
• Energy released from a Gummy Bear • http: //www. youtube. com/watch? v=uj 9 D 3 m c 7 t. Vg&feature=related&safe=active
– Can’t use energy directly from food – Need to store it and release it gradually. – Store it in molecules of ATP.
ATP (Adenosine Triphosphate) – Source of cellular energy – Stores energy as food is broken down so that it can be released slowly to cell when needed rather than all at once. – A type of energy “currency”, that can be “paid out” as the cell needs it.
Structure of ATP (Adenosine triphosphate) – 1 adenine (type of nitrogenous base) – 1 ribose sugar (5 carbon ring) – 3 phosphate groups
How is ATP Formed? – Energy is stored in high energy phosphate bonds
– Cells bond a third phosphate group to ADP – ADP • (adenosine “di”phosphate)
– To release this energy again, the cell breaks off the 3 rd phosphate group and energy is released. – Can happen over and over again. – Like recharging a battery!
IMPORTANT TO KNOW!! • How does ADP and ATP differ? • How is this related to energy?
Storing Energy Add a phosphate to ADP + phosphate + energy → ATP
Releasing Energy Remove a phosphate from ATP → ADP + phosphate + energy Note: The enzyme that catalyzes this reaction is called ATPase.
• Cells can regenerate ATP from ADP as needed by using the energy in foods like glucose.
ATP/ADP Cycle
How do organisms obtain food to make ATP?
• They eat it… – Heterotrophs: obtain food from consuming other living things. • Ex: – – Animals: herbivores, carnivores and omnivores Fungi Some protists Some bacteria
• They make it themselves… – Autotrophs: use light energy from the sun to make their own food through photosynthesis. • Ex: – Plants – Algae – Some bacteria
Photosynthesis • Process by which light energy is converted into the chemical energy of organic compounds (glucose).
• Occurs in the chloroplasts of plant cells (as wells as some single celled organisms, that can carry out photosynthesis. )
Chloroplast Structure • Stroma: protein containing fluid • Grana: stacked membranes containing enzymes and chlorophyll.
Chlorophyll: – green pigment necessary for photosynthesis. – Absorbs red and blue wavelengths of light and reflects green light. (that’s why most plants look green)
• Note: – Other photosynthetic pigments exist besides chlorophyll, but it is the main one used by autotrophs • Ex: Carotenoids (orange/red colored pigment)
Equation for Photosynthesis
Photosynthesis Overview • Plants Take In: – Carbon Dioxide Gas – Water – Sunlight (energy) • Plants Produce: – Glucose (form of stored energy) – Oxygen Gas
The Process of Photosynthesis • How Does the Chloroplast Work? – Light Dependant Reactions (Photochemical) – Light Independent Reactions (Carbon Fixation)
Light Reactions Light Dependant Reactions (Photochemical) – Happen in the thylakoid membranes of grana – Directly involve chlorophyll and sunlight – Produces oxygen – Converts ADP to ATP – Converts NADP+ to NADPH
• Chlorophyll absorbs sunlight – Creates high energy electrons – Electrons enter the electron transport chain – Eventually produce some ATP
• Photolysis – Water gets split inside grana • Breaks into: – One oxygen atom – Two H+ ions – 2 electrons
• The Oxygen produced by splitting water gets released into the air – Source of nearly all the oxygen in Earth’s atomosphere! Thank you plants!!! You make our lives possible.
• The H+ ions and electrons – Join up with NADP+ an “electron carrier” – It becomes NADPH
Making ATP • H+ ions build up and cross the thylakoid membrane causing ATP to form as ATP synthase (an enzyme) turns ADP into ATP
Dark Reactions Light Independent Reactions (Calvin Cycle) – Does not require light – Happens in stroma – Carbon Fixation: • Carbon gets “Fixed” from a simple 1 carbon molecule (CO 2) to a complex 6 carbon one that holds stored energy (glucose/C 6 H 12 O 6)
• Carbon Dioxide Molecules: (CO 2) – enters from atmosphere (through stomata) – Combine to make PGAL a 3 -carbon molecule – 2 PGAL combine to produce a 6 -carbon glucose – Energy for these reactions to take place is provided by ATP and NADPH (from light reactions)
Photosynthesis Summary
Light vs. Dark Reactions
• Video Overview of Photosynthesis (5 min) • http: //www. youtube. com/watch? v=m. Yb. MP wmwx 88&safe=active
• Factors Affecting Photosynthesis – Temperature – Light Intensity – Water and Carbon Dioxide Availability Tutor Vista: http: //www. youtube. com/watch? v=vmm. Wi. J 3 g 9 Cg&safe= active
• Temperature: – Enzymes are needed for photosynthesis – Function best between 0°C and 35°C. – Too hot or too cold and photosynthesis stops
• Intensity of Light: – More intensity = more photosynthesis – Remember blue and red wavelengths are most useful for photosynthesis
• Availability of Water and CO 2: – One of the raw materials for photosynthesis – Split during photolysis reaction – Water loss can kill plants – They have evolved strategies • Waxy coatings on leaves
• Stomata: – small openings in plant leaves that normally admit carbon dioxide – Water can also escape through opening • Guard Cells: – Can open or close stomata to help prevent excess water loss from plant
Stomata and Guard Cells Video: http: //www. youtube. com /watch? v=c. FX 4 Jrs. Pa. Us &safe=active
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