Transcript Cellular Energetics

Cellular Energetics
Fermentation and Cellular
Respiration
Fermentation and Cellular
Respiration
• Both reactions are catabolic/anabolic?
• Chemical equation for respiration:
– C6H12O6 + 6O2  6CO2 + 6H2O + ATP
• Both involve redox reactions (LEO says GER):
– LEO: glucose to CO2
– GER: O2 to H2O
• Electrons = energy!
Cellular Respiration
• In respiration there are 2 e- carriers:
– NAD+ and FAD (oxidized forms)
– NADH and FADH2 (reduced forms)
• These help carry the energy from glucose
to the mitochondria where it will be
harnessed
Cellular Respiration
Cellular Respiration: 4 parts
• 1. Glycolysis (splitting of sugar)
– Takes place in cytoplasm
– Glucose (6-C sugar) is split into 2 pyruvates
(3-C molecules)
– NAD+ is reduced to NADH
– From 1 glucose: produces 2 (net) ATP, 2
NADH, 2 pyruvate
Gycolysis
Cellular Respiration: 4 parts
• 2. Shuttle Step
– Takes place in mitochondria
– Pyruvate is decarboxylated (take off a
carboxyl group) to form acetate (2-C
compound)
– CoA is attached to form Acetyl-CoA
– Produces 1 NADH and 1 CO2 (waste)
Shuttle Step
Cellular Respiration: 4 parts
• 3. Krebs Cycle
– Takes place in the mitochondrial matrix
– Produces the majority of NADH, FADH2, and
CO2 (waste)
– The 2-C fragment from acetyl-CoA is added to
oxaloacetate to make 3-C citrate (citric acid)
• Produces (x2) 3 NADH, 1 FADH2, 1 ATP
and CO2 (waste)
Krebs Cycle
Cellular Respiration: 4 parts
• 4. Electron Transport Chain and Oxidative
Phosphorylation
• ETC proteins embedded in the inner mitochondrial
membrane
• ETC membrane proteins accept e- from NADH and
FADH2
• e- are passed down the ETC via redox reactions until
they reach the final e- acceptor (O2) to form water
• No ATP is made by ETC; must be coupled to oxidative
phosphorylation via chemiosmosis (diffusion of H+
across the membrane)
Cellular Respiration: 4 parts
• 4 cont’d. Electron Transport Chain and
Oxidative Phosphorylation
• As NADH and FADH2 are oxidized, H+
inside the mitochondrial matrix is
transported to the intermembrane space.
This creates a proton-motive force and H+
moves back across the membrane thru
ATP synthase and ATP is produced
ETC
Fermentation
• What if O2 is not present?
• Objective of fermentation is to replenish
NAD+ so that glycolysis can proceed
again
• Takes place in the cytoplasm
Lactic Acid Fermentation
• Prokaryotes and humans
• Pyruvate (product of glycolysis) is
converted to lactate (lactic acid). In this
process NADH gives up its e- to form
NAD+, which can now be used again for
glycolysis
• Produces only 2 ATP and 2 NADH (better
than zero)
Alcoholic Fermentation
• Fungi (yeast)
• Pyruvate converted to acetaldehyde and
then ethanol (ethyl alcohol) producing
NAD+ which can now be used again for
glycolysis
• Produces only 2 ATP, 2 NADH, and 2 CO2
(carbonation in beer!)
Fermentation
Photosynthesis
• Used by producers (autotrophs)
• Takes place in the chloroplast
• 2 parts:
– light-dependent (the photo part- produces
NADPH, ATP, and O2 (waste)
– light-independent or Calvin Cycle (the
synthesis part- carbon fixation- produces
sugar)
Photosynthesis
Photosynthesis- the light reactions
• Occurs in thylakoids
• Chlorphyll a and b, in the photosystems, absorb photons
of light and become excited when their e- gain energy
• Photosystem 2 (P680) absorbs light and e- are excited
• e- are now boosted to a higher level and must be
replaced
• H2O is split (photolysis) and the e- are replaced (and
oxygen is produced)
• e- pass down an ETC and ATP is produced by
chemiosmosis
• e- are passed to photosystem 1
Photosynthesis- the light reactions
• e- are passed from P680 to Photosystem
1 (P700) where they are again boosted to
a higher level
• e- are passed down a 2nd ETC that
produces NADPH
Light Reactions
Calvin Cycle
• Occurs in stroma
• Uses e- from NADPH and energy from
ATP produced in the light reactions
• One molecule of G3P exits the cycle per 3
CO2 molecules fixed and is converted to
glucose
• ADP and NADP+ are returned to the light
reactions
Calvin Cycle
All together now!