Download Slide 1

Cellular Respiration
Overview
1. Process by which cells
break down foods such as
glucose, fats, proteins to
release their stored E
2. Two types:
1. Anaerobic – NO O2
needed
2. Aerobic – O2 needed
3. Both produce E-storage
molecules: ATP or
Adenosine Triphosphate
http://www.chemistry.wustl.edu/~courses/genchem/
LabTutorials/Cytochromes/images/flowchart1.jpg
Anaerobic Respiration
• 1. No O2 required to drive this
• 2. Includes:
– a) Glycolysis – breakdown of glucose
– b) Fermentation
• Examples of anaerobes: yeast (fungus), some
bacteria (Clostridrium, Bacillus)
Glycolysis
1. Occurs in cytoplasm
2. Breaks 1 glucose into 2
pyruvic acids (3-C
structures)
3. 2 ATPs formed
4. 2 NADH E-shuttle
molecules formed
5. Pyruvic acid metabolized
during fermentation
http://www.emc.maricopa.edu/fac
ulty/farabee/BIOBK/enyld1.gif
Fermentation
• Pyruvic acid metabolized by either:
– Lactic Acid pathway
– Alcoholic Fermentation pathway
• Lactic acid pathway metabolizes pyruvic acid into lactic
acid & NAD+
– NAD+ recycled back into glycolysis
– Lactic acid build-up:
• Useful: cheese making industry
• Not beneficial: build up of lactic acid in exercising
muscles causing pain, fatigue
• Alcoholic fermentation pathway metabolizes pyruvic acid
into ethyl alcholo & NAD+
– NAD+ recycled back into glycolysis
– Ethyl alcohol build-up:
• Useful: beverage & baking industries
Efficiency of Glycolysis
• Efficiency = E needed to make ATP x 100
E released by oxid. of glucose
• Eff = (2) (12kCal) x 100 = 3.5%
•
686 kCal
• Is glycolysis very efficient in making ATP?
Aerobic Respiration
• Requires O2 ; occurs in mitochondria
• Aerobic respiration  the Kreb’s cycle &
electron transport chain
• Most organisms are aerobic
• Equation:
– 6C6H12O6 + 6O2  6CO2 + 6H2O + ATP
• Why do humans and most other organisms
breathe?
•
Mitochondria
If O2 present following glyolysis, pyruvic acid
modified & enters mitochondria of eukaryotes (or
cytosol of prokaryotes)
• In eukaryotes: pyruvic acid diffuses into
mitochrondria matrix; it reacts forming acetyl
CoA + NADH+
– Kreb’s cycle begins: acetyl CoAs break down
into CO2 + H+ + ATP (takes ~5 steps)
• Ultimately making glucose which further
breaks down into 6NADH + 2 FADH2 +
2ATP + 4 CO2
– Electron Transport Chain finishes: (lines inner
mitochondira membrane) chemiosynthesis
occurs making up to 34 ATPs!
Efficiency of Aerobic Respiration
• Efficiency = E needed to make ATP x 100
E released by oxid. of glucose
• Eff = (38) (12kCal) x 100 = 66%
•
686 kCal
• Are the Kreb’s cycle & ETC very efficient in
making ATP?
Role of O2 in Respiration
• Energy carrier, NADH, drops off e- that
enter the ETC, as e- move down chain
toward O2, ATPs formed (our E payload
molecules!)
• At the end of the ETC, O2 picks up those
fallen e- & H+ making water (H2O); which
is a by product of respiration along with CO2
Adenosine Triphosphate
1. Energy molecule of
cell
2. All cell activities
powered by ATP
3. Structure:
1. 3 phosphates
2. Ribose sugar
3. N-base
(adenine)
ATP/ADP Cycle in Cell
1. ATP is constantly used and remade within cells to
power the cell’s activities
2. E is released by breaking or stored by making
phosphate bonds
Respiration Overview
Process
Where it occurs
Anaerobic:
Cytoplasm
Glycolysis &
fermentation (LAF
& AF)
Aerobic: Kreb’s
Mitochondria
cycle & ETC
Net gain
of ATP/
glucose
2 ATPs
36 ATPs