Respiration
Biochemistry, not breathing!
Raven Ch. 5 and 6
Kinds of Energy
•	Kinetic energy, or energy of motion
•	Potential energy, or stored energy

•	Forms of energy convert:
–	Food (P.E.) becomes motion in animals
–	Motion (K.E.) in a turbine becomes stored energy in electricity
Laws of Thermodynamics
•	Conservation of energy
•	The universe tends toward disorder (lowest potential energy)
So why does life persist if the universe tends toward disorder?
Inputs of energy from the the sun forestall disorder.
Living things harvest energy, store it, and release it in a controlled way.

Storage is important!
•	Energy is not always available
•	Plants experience a “food crises” every night.

Photosynthesis: 24 hour day
Respiration: 24 hour day
Combined: 24 hour day
Combined: 24 hour day
Biochemical Reactions are Largely Driven by Enzymes
•	Organic catalysts
•	Polypeptides (proteins)
•	Another group of polypeptides, structural proteins, make up tissues
•	Under genetic control, so gene changes have potentially large effects
Enzymes reduce activation energy.
...and facilitate reactions
Strong geometric component in enzyme function.
Respiration is a series of redox reactions.
•	Oxidation--loss of electrons
•	Reduction--addition of electrons
•	Energy is ultimately made available as ATP
–	ADP + Pi ---> ATP
Principle players in terms of location:
•	Cytoplasm 
–	conversion of 6-C glucose to 3-C pyruvate, intermediates, and ATP
•	Mitochondrion 
–	conversion of pyruvate to CO2
–	make more intermediates, ATP
–	conversion of intermediates to ATP
Processes
•	Glycolysis
–	Conversion of sugar (C6) to pyruvate (C3)
–	Capture of some energy as ATP, NADH
•	Krebs Cycle
–	Conversion of pyruvate to CO2
–	Capture of some energy as NADH, FADH2, ATP

•	Electron transport
–	Conversion of stored energy in NADH and FADH2 to more ATP

Important Idea:
Bookkeeping for C and E
•	Fate of carbon-based compounds, ultimately becoming CO2
•	Fate of energy stored in C-based compounds and transferred to other molecules, ultimately becoming ATP

Glycolysis
•	Occurs in cytoplasm
•	Requires no oxygen
CYTOPLASM
Glycolysis Overview
Glycolysis:
Two Phases

A turning point:
•	If there is oxygen, proceeds to Krebs cycle
•	If oxygen is absent, proceeds to fermentation
Krebs (Citric Acid) Cycle
•	Occurs in mitochondrion
•	Breakdown of pyruvate (C3) into a complex (Acetyl-CoA) containing 2 of pyruvate carbons
•	Acetyl-CoA attaches to carrier
•	C is removed as CO2
•	Make NADH, FADH2, ATP

Electron Transport Chain
•	In mitochondrion, across interior membrane
•	Energy from NADH and FADH2 used to pump protons into intermembrane space
•	ATP synthase uses flux of H+ to power ATP synthesis
•	Each NADH makes 3 ATP, FADH2 makes 2 ATP
Electron Transport Chain
•	Electron carriers in inner membrane of mitochondrion

If O2 is absent, something very entertaining happens.
Fermentation is a not very efficient way to extract energy
•	It breaks down any NADH in the system
•	ATP production is limited to a net of two from glycolysis
•	Cells energy demands are reduced under low O2, making this a viable solution from energy standpoint
•	Alcohol is often toxic

•	Wine:  more complex sugars to simple sugar to alcohol
•	Beer:  starch to sugar to alcohol
–		Malt is ingredient that transforms starch to sugar