Transcript Section 2.3 - Father Michael McGivney Catholic Academy

Section 2.3: Related Pathways
• Carbohydrates are the first nutrients most
organisms catabolize for energy.
However, when necessary, most
organisms can metabolize proteins, lipids
and nucleic acids.
Related Pathways
• Protein
Catabolism
• Lipid
Catabolism
• Anaerobic
Pathways
Protein Catabolism
Protein  amino acids  deamination  ammonia (NH3)
• The remaining portions of amino acids are converted into
various components of glycolysis or Kreb cycle.
• Examples:
• Leucine  acetyl-CoA
• Alanine  pyruvate
• Proline  α ketoglutarate
Lipid Catabolism
• Triaglycerides  glycerol + fatty acids
• Glycerol  Glucose (gluconeogenesis) or DHAP
then G3P
• Fatty acids  β-oxidation (matrix)  acetyl-CoA
– Each cleavage uses 1 ATP and produces 1 NADH and 1
FADH2
• Produces more ATP than Glucose (see pg. 118)
Concepts in Biochemistry Interactive Animations
ATP used
12 Carbon Atoms
from 2 Glucose
molecules
12 Carbon Atoms from
Laurate (fatty acid)
4 (2X2)
5
ATP produced 76 (2X38)
97
Theoretical
yield of ATP
72 (2X36)
92
Actual Yield of 60 (2X30)
ATP
75
Energy Yield
(kJ/g)
38
16
Anaerobic Respiration
• During oxygen deficient periods, the
process of cellular respiration can get
backed up.
• NADH cannot get recycled back to NAD+
to pick up more electrons.
• Organisms have evolved a way to recycle
NAD+ and allow glycolysis to continue.
Fermentation: ATP from
Glucose, without O2
• Many organisms and some cells live
without O2, deriving energy from glycolysis
and fermentation. Together, these
pathways partly oxidize glucose and
generate energy-containing products.
Fermentation reactions anaerobically
oxidize the NADH + H+ produced in
glycolysis.
Anaerobic Pathways
• Required to recycle NADH when oxygen levels are
low.
• Ethanol Fermentation
– NADH passes it H atoms to acetaldehyde
(formed when CO2 is removed from pyruvate),
this forms ethanol.
– NAD+ can be recycled and glycolysis continues.
• Lactic Acid Fermenatation
– NADH transfers its H atoms to pyruvate forming lactate
Figure
7.15
Lactic Acid Fermentation
Lactic Acid Fermentation
• NADH transfers its
hydrogen atoms to
pyruvate to form lactate
• Lactate can be
oxidized back to
pyruvate when the
strenuous exercise
stops
• Extra oxygen (oxygen
debt) is required to
catabolize lactate into
CO2 and H2O
Figure
7.16
Alcoholic
Fermentation
Ethanol Fermentation
• CO2 is removed from
pyruvate to form
acetaldehyde
• NADH passes its
hydrogen atoms to
acetaldehyde to form
ethanol
• Carried out by yeast
• Breads, wine, beer,
liquor, soy sauce
Videos\Fermentation (Anaerobic
respiration) Lactic Acid and Ethanol.flv
Contrasting Energy Yields
• For each molecule of glucose used,
fermentation yields 2 molecules of ATP. In
contrast, glycolysis operating with
pyruvate oxidation, the citric acid cycle,
and the respiratory chain yields up to 36.
Figure 7.17
– Part 1
Energy Yields
Figure 7.17
– Part 2
Energy Yields
Metabolic Pathways - Metabolic Mill
• Catabolic pathways feed into the respiratory
pathways. Polysaccharides are broken down
into glucose, which enters glycolysis. Glycerol
from fats also enters glycolysis, and acetyl CoA
from fatty acid degradation enters the citric
acid cycle. Proteins enter glycolysis and the
citric acid cycle via amino acids.
• Anabolic pathways use intermediate
components of respiratory metabolism to
synthesize fats, amino acids, and other
essential building blocks for cellular structure
and function.
Figure
7.18
The Metabolic
Mill
VO2 Max and Lactate Threshold
Aerobic fitness
• the ability of the heart, lungs, and bloodstream to
supply oxygen to the cells of the body during
physical activity.
VO2 max:
• The max.volume of oxygen (mL) that the cells of
the body can remove from the bloodstream in
one minute/kg of body mass while the body
experiences maximal exertion
• Typical value: 35 mL/kg/min
• Elite athletes: 70 mL/kg/min
Videos\VO2 Max Test.flv
Lactate Threshold
Videos\Lactate Threshold.flv
Homework
1. Prep for Investigation 2.2.1, pp. 128,
download worksheet
2. pp. 124, # 1-13
3. Chapter 2 Quiz: Monday October 19th
4. Prep for Quiz: pp. 133, Self-Quiz
5. Prep for Quiz: pp. 134, try answering
Review questions