Download Powerpoint Slides for Chapter Seven

Chapter seven
Metabolism: Transformations and
Interactions
Issues to address in this chapter:







What is metabolism?
What are the types of metabolic reactions
and where do they occur?
How do we get energy from glucose?
What happens if we don’t have enough
oxygen?
Where do proteins and lipids come in?
How does the system adapt to feasting?
How does metabolism adjust to fasting?
What is metabolism?


The sum of all
chemical reactions in
a living system
Our emphasis will be
on harvesting
energy from nutrient
molecules
Language of metabolism






Pathway
Intermediate
Anabolic
Catabolic
Aerobic
Anaerobic




Coupled reaction
Enzyme
Coenzyme
ATP
Catabolism vs. Anabolism
Figure 4.1
ATP and Coupled Reactions
Where do these reactions occur?




Nucleus
Cell membrane
Mitochondria
cytoplasm
Results of digestion: counting
carbons



Carbohydrates  glucose
(6 carbons)
Protein  amino acids
(2 or 3 carbons)
Lipids  glycerol (3 C) +
fatty acids (even #C)
Metabolism of carbohydrates




Sugars (6 carbon molecules) enter cell via insulin.
In cytoplasm molecule is broken in half—made
into two three carbon molecules (pyruvate)
Three carbon fragment moves into mitochondria
losing a carbon in the process. (acetyl CoA)
Inside the mitochondria, the two carbon piece left
from the sugar is converted to carbon dioxide,
water, and lots of ATP (TCA & ETS)
Glycolysis
Figure 4.9
TCA
ETS
Figure 4.5
What if not enough oxygen is
present?



Cori cycle
Glucose  pyruvate lactic acid or
lactate  blood  liver  new glucose
(gluconeogenesis)
(process starts all over again.)
Protein metabolism




Proteins are digested to amino acids in
digestive system.
Amino acids move into blood, and then
to liver.
In liver the nitrogen is removed
(deamination) and three carbon
fragment produced.
Three carbon fragment blood  cell
 fits in at pyruvate.
Lipid metabolism






Most dietary lipids are triglycerides (broken
down into glycerol + 3 fatty acids)
Fatty acids move from blood into cell (lipoprotein
lipase) and into cytoplasm.
Progressively broken into two carbon fragments
(lipolysis or beta oxidation)
Two carbon fragments move into mitochondria
as acetyl Co A and are metabolized.
Glycerol moves from blood to cell.
As 3C molecule is made into pyruvate
Figure 4.13
Eating too much
feasting
Too many carbs




Glucose is converted to pyruvate
Pyruvate converts to acetyl Co A
Acetyl Co A fragments combine to make
fatty acids (lipogenesis)
Fatty acids stored as fat (triglyceride)
Too many proteins





Amino acids deaminated in liver
Come into metabolic process at pyruvate
Pyruvate converted to acetyl Co A
Acetyl Co A fragments joined together to
make fatty acids
Fatty acids stored as fat (triglyceride)
Too much fat




Fatty acids leave small intestine via
lymph
Lymph converges with blood stream
Fatty acids taken directly to fat cells
and stored as fat (triglyceride)
No metabolism involved
Eating too little
Fasting
fasting


First-- draw sugars from glycogen stored in
liver (glycogenolysis) several hours
Second-- muscle is degraded, deaminated,
and made into glucose (gluconeogenesis)
up to 10 days

Third—without glucose fatty acid oxidation is
abnormal making ketone bodies instead of
acetyl Co A (ketosis) from about 10 days to
2 months
Figure 4.15
Overall results of fasting

These metabolic consequences




Depletion of liver glycogen
Loss of muscle mass and vital body proteins
Ketosis
Cause these symptoms






Wasting
Slowed heart rate, metabolism, respiration
Lower body temp.
Impaired vision
Organ failure
Decreased disease resistance
Overview of Metabolism
Some Important Coenzymes
Figure 4.20