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Respiration
Chapter 6
Cellular Respiration - Basics
• releases energy from glucose
• released energy is chemical energy
• occurs in cell
cytoplasm
mitochondria
• works better with oxygen (aerobic)
than without oxygen (anaerobic)
Cellular Respiration - Process
glucose
+ oxygen
C6H12O6
+
O2
carbon
dioxide
CO2
+ water + energy
+
H2O
+ ATP
Aerobic Respiration
aerobic = with oxygen
C6H12O6 + O2 -----> CO2 + H2O + ATP
Three process occur in aerobic respiration
1. Glycolysis
glucose
C
C C
C C
C
PEP
2 pyruvic acid
C
C
C
C
C
C
occurs in the cytoplasm
oxygen is not required
electron acceptor is nicotinamide adenine dinucleotide
NAD --> NADH
Aerobic Respiration cont’d
2. Krebs Cycle (citric acid cycle)
C
C
C
C
pyruvic acid
(3C)
(in cytoplasm)
C
C
CO2
acetyl-coenzymeA
(2C)
(in mitochondron)
occurs in:
mitochondria
FADH2
electron acceptors are
NAD and FADH2
CO2
Krebs
Cycle
ATP
CO2
C
C
NADH
Kreb’s Cycle
Aerobic Respiration cont’d
3. Electron transport
• electrons transferred
from NADH, FADH2 to
oxygen and water is
formed
• oxidative phosphorylation
• ATP synthase complex
• protons pumped across
membrane
• occurs in mitochondria
• conversion equivalents:
NADH = 3 ATP
FADH2 = 2 ATP
Aerobic Respiration cont’d
• Energy from aerobic respiration
• Glycolysis
• net gain of 6 ATP
• pyruvic acid --> acetyl-CoA
• 2 NADH = 6 ATP
• Krebs Cycle
• 2 ATP
• Electron Transport
•Total = 36 ATP / glucose
• 6 NADH = 18 ATP
•39% of energy available
• 2 FADH2 = 4 ATP
• oxidative phosphorylation •61% of energy is lost as heat
Anaerobic Respiration
(without oxygen)
1. ethanol fermentation
glucose ---> pyruvic acid ---> ethyl alcohol + CO2 + ATP
C6H12O6 ----> 2C2H5OH + 2CO2 + 3ATP
• 25% of energy of aerobic respiration
• occurs in some plants and microorganisms
including yeasts
Alcohol Fermentation
• Ancient Eqyptian wall painting: historical record of wine-making
• ~ 5000 yrs ago, perhaps earlier
• Grapes were picked, crushed by foot, juice collected in jugs,
then fermented producing wine.
Anaerobic Respiration cont’d
2. lactic acid fermentation
glucose ---> pyruvic acid ---> lactic acid + ATP
C6H12O6 ----> 2C3H6O3 + 2ATP
• 22% of energy of aerobic respiration
• mammalian muscle and some microorganisms
Organic Macromolecules
• four groups
Carbohydrates
built from monosaccharides
Protein
built from amino acids
Lipids
built from glycerol & fatty acids
Nucleic acids
built from nucleotides
Carbohydrates
monosaccharides
polysaccharide
disaccharides
Lipids
Protein
Biochemical Pathways
• note catabolic and anabolic
pathways
• note production and use of:
• proteins
• lipids
besides carbohydrates
Biochemical Pathways
• note catabolic and anabolic
pathways
• note production and use of:
• proteins
• lipids
besides carbohydrates
Biochemical Pathways
• note catabolic and anabolic
pathways
• note production and use of:
• proteins
• lipids
besides carbohydrates
Biochemical Pathways
• note catabolic and anabolic
pathways
• note production and use of:
• proteins
• lipids
besides carbohydrates
Biochemical Pathways
• note catabolic and anabolic
pathways
• note production and use of:
• proteins
• lipids
besides carbohydrates
What is the
connection
between
respiration and
photosynthesis?
Carbon
Cycle
Numbers = approximate
carbon exchange (Gt/year)
• Is atmospheric CO2 in “equilibrium”?
• Absorption by plants and the oceans
• Accumulating in the atmosphere as carbon dioxide
• CO2 emission into the atmosphere by fossil fuel
combustion dramatically changed “equilibrium”
CARBON (oil, coal, natural gas, etc) + OXYGEN + COMBUSTION -> CO2 + heat
Changes in CO2 concentration post industrialization
410
390
370
CO2 (ppm)
350
330
310
290
Conclusion: carbon released
from the burning of fossil
fuels has increased
exponentially over the last
century!
Air samples at Mauna Loa, Hawaii are
collected continuously from air intakes
at the top of four 7-m towers and one
27-m tower. Four air samples are
collected each hour for the purpose of
determining the CO2 concentration
270
250
230
1840
1860
1880
1900
1920
1940
1960
1980
2000
2020
Changes in global temperature over time
80
60
temperature (C)
40
20
0
1860
-20
-40
-60
1880
1900
1920
1940
1960
1980
2000
2020
Relationship between atmospheric CO2 and global
temperature
80
60
R² = 0.8672
termperature (C)
40
20
0
-20
-40
0
50
100
150
200
250
CO2 (ppm)
300
350
400
450
Global Warming Contributors
Consequences of CO2 increase
•
CO2 as a Greenhouse Gas
•
•
•
•
third most abundant gas in atmosphere
absorbs heat energy reflected by earth
acts as a blanket around earth
produces the greenhouse effect
• This is normal, and good!
• Excessive greenhouse gas
accumulation?
• increase GH gas; increase heat
absorption
• increased heat of earth
• Global Warming
CO2 in atmosphere
key component of nature’s thermostat
If carbon cycle
removes excessive
CO2
earth
cools
If carbon cycle
generates excessive
CO2
earth
warms
Carbon Flow: Living Systems
• Life is carbon based
• All organisms use carbon compounds for
• Energy:
• Glucose primarily, is converted to ATP in cells
• Structural components:
• Cell membrane & wall; cellulose, proteins,
• Regulatory components:
• DNA,enzymes, hormones, neurotransmitters, etc.
• Thus:
• energy flow is tied to carbon
• life is tied to carbon
Carbon Flow: Living Systems
• Goals for you as student:
• Trace carbon
• from atmosphere
• through photosynthesis in autotrophs
• through cellular respiration in autotrophs and
heterotrophs
• back into atmosphere