unit 4 energy
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Unit 4: Energy
Energy – What is it? The ability to do work Energy can not be created or destroyed
– Energy is TRANSFORMED Forms of energy
– Light, electric, chemical Chemical energy is stored in the
electrons of chemical bonds
Biochemical Energy Cells store and release energy using the
chemical ATP– Adenosine triphosphate
ATP is the “energy currency” of the cell– MANY cellular processes use ATP
Cells release energy by breaking a phosphate bond
Photosynthesis Plants convert light energy into chemical
energy Energy is stored in the bonds of
carbohydrates
Light and Pigments Light travels in waves Colors have different wavelengths
“White” light is a mixture of all colors in the visible spectrum
Red – longest wavelength, lowest energy
Light and Pigments Plant pigments absorb sunlight Chlorophyll – green pigment needed for
photosynthesis– Reflects green light– Absorbs other light
Photosynthesis Overview Reactants: CO2, H2O, light energy Products: O2, C6H12O6 (glucose) Two reactions
– Light reaction– Calvin Cycle (light-independent reaction)
Chloroplast Structure
– Light rxn
Stroma – open space – Calvin cycle
Thylakoid sacs contain chlorophyll Granum – stacks of thylakoids
Photosynthesis Overview
Electron Carriers Light energy “excites” electrons in
chlorophyll High energy electrons need special
carriers– ie: NADP+ and NAD+
Light Reaction Chlorophyll absorbs light, and electrons
become energized Water splits to produce H+ and O2
Electron loses energy to form ATP– ATP goes to Calvin Cycle
H+ and NADP forms NADPH– Carries energy to
Calvin Cycle
Light Reaction – Electron Transport
Light Reaction
CO2 is added to a 5 carbon sugar
Energy from NADPH & ATP are used to carry out reactions
Light Independent Rxn
Produces sugar (glucose)
Calvin Cycle
ATP Revisited
How do living things use ATP for energy?
Where does ATP come from?
Overview of Cellular Respiration
6O2 + C6H12O6 6CO2 + 6H2O + ATP
Overview of Cellular Respiration Energy from glucose is released
– In the presence of O2
– Energy is stored in ATP
– CO2 is a byproduct 3 Stages
– Glycolysis– Krebs Cycle– Electron Transport Chain
Glycolysis In the cytoplasm Glucose breaks into 2 molecules of pyruvic
acid (3C) Uses 2 ATP, produces 4 ATP
– Net gain of 2 ATP
2 NADH produced Pyruvic acid is used
for respiration OR fermentation
Krebs Cycle In the mitochondria Pyruvic acid breaks down Series of 9 rxns which
produce:– CO2
– FADH2 and NADH
– 2 ATP
FADH2 and NADH go on to the ETC to….– MAKE MORE ATP!!!!
Electron Transport Chain
Occurs in mitochondria Uses high energy
electrons from FADH2 and NADH to make ATP
O2 accepts the final electron forming H2O
The Totals
Electron carriers which go on the electron transport chain to generate ATP!
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Fermentation Releases energy from food in the
absence of O2
2 Types– Alcoholic – produces ethanol and CO2
• Yeast, bacteria
– Lactic Acid – produces lactic acid• Muscle cells, bacteria