AP Biology
Mr. Elliott
Cellular Respiration
• The consumption of oxygen to produce carbon
dioxide and energy to fuel cellular processes.
Cellular Respiration:
3 Processes
• Glycolysis
• Krebs
• Oxidative phosphorylation via the
Electron Transport Chain
Glycolysis
Glucose + 2 ADP + 2 NAD+  2 Pyruvate + 2 ATP
+ 2 (NADH + H+)
Cytosol
Preparatory and payoff phases
Oxidative
Phosphorylation
• Involves the oxidation of NADH and FADH₂ to NAD⁺
and FAD while 0₂ is reduced to H₂0 through a series
of electron transfers.
• The free energy from the electron transfer is used to
synthesize ATP from ADP and Pi (phosphorylation).
• Oxidation is COUPLED to phosphorylation.
• Oxidative phosphorylation accounts for the great
bulk of ATP you produce, and for the great bulk of
oxygen you consume.
Oxidative Phosphorylation
Site of Oxidative
Phosphorylation
Requires an intact membrane.
(an important clue to its mode
of operation!)
Mitochondria “Tid-bits”
• Cristae (convolutions) of the inner membrane
provide a large surface area.
• The inner membrane of single liver mitochondrion
may contain more than 10, 000 respiratory chains
and ATP synthase proteins.
• The mitochondria of plants, invertebrates and
eukaryotes are very similar. They only differ in size,
shape and degree of convolution.
The Electron Transport
Chain
The Electron Transport
Chain
The Chemiosmotic
Theory
Proposed by Peter Mitchell in 1961
“The free energy of electron transport is conserved by
pumping H⁺ from the mitochondrial matrix into the
intermembrane space.”
Pumping of protons creates an electrochemical
gradient across the inner mitochondrial membrane.
This gradient is then harnessed to synthesize ATP as H⁺
flow back through a proton pore associated with the
ATP synthase enzyme.
The Electron Transport
Chain
Three Possible Fates of Pyruvate
Fermentation
• The breakdown of glucose to yield energy to an
organism without the consumption of oxygen.
o i.e. Anaerobic glycolysis
• Two types:
o Alcohol fermentation
o Lactic acid fermentation
Alcohol Fermentation
Glucose + 2Pi2- + 2ADP3-  2 ethanol + 2CO₂ + 2ATP⁴⁻
Lactic Acid Fermentation
Glucose + 2Pi2- + 2ADP3-  2 Lactate + 2ATP⁴⁻
Anaerobic Glycolysis:
Feeling that Burn
i) Anaerobic glycolysis:
Glucose + 2Pi2- + 2ADP3- 2
Lactate⁻ + 2ATP⁴⁻
ii) ATP utilization:
2ATP⁴⁻ + 2H₂0  2Pi2- + 2ADP3- +
2H⁺
Sum of i +ii :
Glucose + 2H₂0  2 Lactate⁻ + 2H⁺
Fermentation vs.
Cellular Respiration
Similarities:
Both oxidize glucose via glycolysis.
Both pathways use NAD+ as the oxidizing agent.
Differences:
The way in which NADH is converted back to NAD to
sustain glycolysis.
The final electron acceptor (pyruvate vs. oxygen)
Yield of ATP (2 ATP vs. 36 ATP)
Products produced
Photosynthesis
6 𝐶𝑂2 + 6 𝐻2 𝑂 → 𝐶6 𝐻12 𝑂6 + 6 𝑂2
The mechanism by which organisms produce glucose
from sunlight.
Highly endergonic
Choroplasts:
The Site of Photosynthesis
Thylakoid Space
Photosynthetic Pigments
• Chlorophyll A – primary pigment which participates
directly in the light reaction stage
• Chlorophyll B – absorbs wavelengths not picked-up
by chlorophyll A
• Carotenoids – accessory pigments (yellow/orange),
absorbs light missed by chlorophylls
Photosynthetic Pigments
• Energy absorbed by chlorophyll B and carotenoids
is passed along to chlorophyll A
• Excessive light intensity can cause damage to
chorophyll
• Photoprotection – the absorbance of excess energy
by carotenoids to protect chlorophyll by light
damage
Photosystems
• Chlorophyll A is the main pigment used to absorb
light energy, present bountifully in the lightharvesting complexes of the thylakoid membranes.
• Chlorophyll B and carotenoids act as an
“antennae complex”
• Altogether, these molecules work with proteins to
form light-harvesting complexes
• Energy is forwarded to a pair of chlorophyll A
molecules, a. k. a. the reaction center chlorophyll
Photosystems
Photosystems I and II
𝐿𝑖𝑔ℎ𝑡 𝑒𝑛𝑒𝑟𝑔𝑦 + 𝑁𝐴𝐷𝑃+ + 𝐴𝐷𝑃 + 𝑃𝑖 → 𝑁𝐴𝐷𝑃𝐻 + 𝐴𝑇𝑃
Light-dependent reaction
Photosynthesis:
2 Processes
The Cal
The Calvin Cycle
• 3 𝐶𝑂2 + 9 𝐴𝑇𝑃 + 6 𝑁𝐴𝐷𝑃𝐻 →
𝐺𝑙𝑦𝑐𝑒𝑟𝑎𝑙𝑑𝑒ℎ𝑦𝑑𝑒 3𝑃ℎ𝑜𝑠𝑝ℎ𝑎𝑡𝑒 + 9 𝐴𝐷𝑃 + 9 𝑃𝑖 + 6 𝑁𝐴𝐷𝑃+
• Light-independent
• Makes 3 turns to create one molecule of glucose
The Calvin Cycle
The Calvin Cycle
Fate of G3P