How do cells obtain organic compounds for energy?
Heterotrophs: Cannot make their own food Autotrophs: Can make their own food
– Photoautotrophs: Use energy from the sun (photosynthesis) to produce organic compounds (glucose)
Plants, algae and some bacteria
– Chemoautotrophs: Use energy stored in inorganic compounds (chemosynthesis) to produce organic compounds
Some bacteria found at the hydrothermal vents of the seafloor
Photosynthesis
Method of converting light energy from the sun into chemical energy that cells can use – Divided into the light-dependent and light-independent
reactions
Photosynthesis takes place in chloroplasts– The parts of a chloroplast are as follows:
Thylakoids- disk-shaped structures that contain the pigment chlorophyll (absorbs the sunlight)
Grana- A stack of thylakoidsStroma- Liquid between grana
Overall Photosynthesis Reaction
6CO2 + 6 H2O + light energy → C6H12O6 + 6O2
•On the left of the arrow are the reactants (the components that “react” together).•On the right of the arrow are the products. •Identify how a plant obtains the reactants.
Light-dependent Reactions
Chlorophyll (in thylakoids) absorbs the light energy– Plants have 2 types: Chlorophyll A and Chlorophyll
B Water molecules are split apart producing H and
O2
Electrons flow throughout the thylakoid membrane (electron transport chain)
Energy compounds ATP and NADPH are produced
Light-independent Reactions (Dark Reactions)
Occur in the stroma ATP and NADPH from the light reactions are
used to fuel the break down of CO2 and the reassembling of the atoms to produce glucose.
This reassembling is called “carbon fixation”. Carbon fixation occurs in a series of reactions
called the Calvin Cycle.
Photosynthesis Practice
You and a partner need:– 6 orange circles = C– 12 blue triangles = H– 18 pink squares = O– 1 large green oval = thylakoid– 1 small green rectangle = ATP– 1 small green rectangle = NADPH– 1 yellow circle = sun
Getting energy out of food
Plants and animals both use glucose from photosynthesis for cell fuel.
Glucose (or other carbs), proteins, and fats are not a form of energy that our cells can use.
Cellular respiration converts glucose into a usable energy form (ATP) for cells.
Cellular Respiration Overview
The reactions of cellular respiration occur the same way in plants and animals.
Overall Reaction:
C6H12O6 + 6O2 → 6CO2 + 6H2O
How is this compared to the photosynthesis equation?
Glycolysis
Glycolysis is the first process of cellular respiration.
It occurs in the cytosol. Glucose (C6H12O6) is partially broken down to
produce 2 pyruvate (C3H3O3) compounds This process yields 2 ATP and 2 NADH for every
glucose molecule.
Aerobic Cellular Respiration
Oxygen required=aerobicAerobic respiration follows glycolysis. It occurs in the mitochondria.There are 2 main parts to aerobic
respiration:– Kreb’s Cycle– Electron Transport Chain
Kreb’s Cycle
Completes the breakdown of glucose– Takes the 2 pyruvate (C3H3O3) and completely
breaks them down.– The carbon and oxygen atoms of pyruvates
end up in CO2 and H2OThis is where the CO2 that we exhale is produced!
– 3 NADH and 1 FADH2 and 2 ATP get produced
Electron Transport Chain
Here is where most of the energy is produced! Electron flow ultimately produces 32 ATP! The oxygen that we inhale is the electron
acceptor at the end of the ETC. This acceptance of electrons is what produces the ATP.
Cellular Respiration Practice
You and a partner need:– 5 NADH (green)– 4 ATP (red)– 1 FADH2 (green)–
1 mitochondria (blue)
Anaerobic Cellular Respiration
Some organisms (some bacteria) thrive in environments with little or no oxygen
No oxygen used= anaerobic Anaerobic organisms experience anaerobic cellular
respiration after glycolysis. This produces NO ATP! Depending on the type of cell, the end products of this
are alcohol or lactic acid.
Energy Tally
Anaerobic organisms can’t be too energetic but are important for global recycling of carbon
Aerobic AnaerobicGlycolysis
Kreb’s Cycle
Electron Transport Chain
Total ATP per glucose
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