Transcript Photosynthesis and Cellular Respiration

Photosynthesis and
Cellular Respiration
Photosynthesis
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Method of converting sun energy into chemical
energy usable by cells
Only PLANTS engage in photosynthesis
Photosynthesis takes place in specialized
structures inside plant cells called chloroplasts
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Light absorbing pigment molecules e.g. chlorophyll
Photosynthesis
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Plants capture energy by absorbing light and
using it to form strong (covalent) chemical
bonds between the atoms of carboncontaining (organic) molecules.
These molecules can be used to assemble
larger molecules.
Photosynthesis Formula:
REACTANTS
6CO2 + 6 H2O +
light energy
PRODUCTS
C6H12O6 + 6O2+ 6H2O
Reactants= Carbon Dioxide and Water
Products= Glucose and Oxygen gas.
Photosynthesis
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Plants and animals will use the “glucose”
produced during photosynthesis for cellular
respiration.
Cellular Respiration
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Cellular respiration is a fundamental process in
every organism, in which cells break down
organic compounds to produce energy.
Transformation of chemical energy in food into
chemical energy that cells can use, in the form of
ATP.
Cellular Respiration
REACTANTS
C6H12O6 + 6O2
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PRODUCTS
Enzymes
6CO2 + 6H2O + ATP
Reactants = glucose (carbohydrate) and oxygen
Products = carbon dioxide, water, and energy
BOTH plants and animals engage in cellular
respiration.
Cellular Respiration Process
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Begins with Glycolysis:
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Glycolyis takes place in the cytocol of cells.
One glucose molecule is oxidized to form two pyruvic
acid molecules.
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This results with a net production of 2 ATP molecules and 2
NADH molecules.
If oxygen is NOT present….
If oxygen IS present….
Glycolysis will lead to
ANAEROBIC RESPIRATION
Glycolysis will lead to
AEROBIC RESPIRATION
Anaerobic Cellular Respiration
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Some organisms thrive in environments with little or no
oxygen
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Marshes, bogs, gut of animals, sewage treatment ponds
No oxygen used= ‘an’aerobic
Also called Fermentation
Results in no more ATP, final steps in these pathways
serve ONLY to regenerate NAD+ so it can return to pick
up more electrons and hydrogens in glycolysis.
Examples of Anaerobic Respiration
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Lactic acid fermentation in muscle cells:
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An enzyme converts pyruvic acid into lactic acid
Alcoholic fermentation in yeast (beer/bread):
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Other enzymes convert pyruvic acid into ethyl alcohol
and carbon dioxide.
Aerobic Cellular Respiration
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Oxygen required=aerobic
Occurs inside the Mitochondria of the cell.
2 more sets of reactions occur within the
mitochondria:
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1. Kreb’s Cycle
2. Electron Transport Chain
Kreb’s Cycle
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The pyruvic acid produced during glycolysis is converted to acetyl
CoA. The acetyl CoA enters the Kreb Cycle…
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Kreb Cycle:
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Completes the breakdown of glucose
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Takes the pyruvate (3-carbons) and breaks it down, the
carbon and oxygen atoms end up in CO2 and H2O
Hydrogens and electrons are stripped and loaded onto NAD+
and FAD to produce NADH and FADH2
NADH and FADH2 donate their electrons to the electron
transport chain in the inner mitochondrial matrix.
Each turn of Krebs cycle generates 3 NADH, 1
FADH2, 1 ATP, and 2 CO2
Electron Transport Chain
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Electron carriers loaded with electrons and protons from
the Kreb’s cycle move to this chain-like a series of steps
(staircase).
As electrons drop down stairs, energy released to form a
total of 32 ATP
During aerobic respiration, oxygen accpts both protons
and electrons from the electron transport chain.
Oxygen waits at bottom of staircase, picks up electrons
and protons and in doing so becomes water.
Energy Tally
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Cellular respiration can produce up to 38 ATP
from one single molecule of glucose:
36 ATP for aerobic vs. 2 ATP for anaerobic
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Glycolysis
2 ATP
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Kreb’s
2 ATP
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Electron Transport
32 ATP
36 ATP
Anaerobic organisms can’t be too energetic but
are important for global recycling of carbon