Download Chapter 7 – Metabolism

Chapter 7 – Metabolism
Metabolism – The sum of all the chemical reactions that go on in living cells.
metabolism includes all of the ways the body obtains and uses energy from food.
Energy
The liver is the most metabolically active organ in the body.
Functions of the Liver include:
Carbohydrates
 Converts fructose and galactose to glucose
 Makes and stores glycogen
 Converts glycogen to glucose
 Converts excess glucose to fatty acids
Lipids
 Makes and breaks down triglycerides, phospholipids, and
cholesterol
 Breaks down fatty acids for energy when needed (makes ketones)
 Manufactures bile
Proteins
 Makes nonessential amino acids
 Removes excess amino acids from circulation
 Removes ammonia from the blood and converts it to urea to be
excreted by the kidneys
 Makes plasma proteins such as clotting factors
Other Functions
 Detoxifies the body of alcohol, drugs, and poisons and helps them
be excreted by the body
 Stores most vitamins and some minerals
 Helps destroy old red blood cells and recycle the iron
ENERGY METABOLISM:
FEASTING (Food Excess)
 Too much food from any nutrient (carbohydrates, protein, or fat) can be stored as fat in
the form of triglycerides.
 The body uses less energy converting dietary fat to body fat, but must work harder
converting carbohydrates and protein to body fat.
 Excess carbohydrates will first be stored as
, then whatever
cannot be stored will get converted to body fat.
 Excess protein will NOT be used to make muscle. Any excess not used to replace normal
daily losses will be converted to body fat.
Carbohydrates
→
Glucose
→
Protein
→
Amino acids →
→
Body proteins
Loss of nitrogen in urine (urea)
Fat
→
Fatty acids
Body Fat stores
→
Liver and muscle glycogen stores
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FASTING (Food Deficiency)
 The brain constantly needs
as a fuel source. When carbohydrates are
not available, protein can be used to make glucose by body protein (muscle) breakdown.
 When fat is needed for energy,
are produced which provide a little
bit of fuel but cannot fuel the brain entirely.
 Health Consequences of Fasting:
o Suppression of appetite
o Slowing of Metabolism
o Lowered body temperature
o Reduced resistance to disease
o Ketoacidosis (lowered ph of the blood)
ALCOHOL:
2005 Dietary Guideline for Americans – “Those who choose to drink alcoholic beverages should
do so sensibly and in moderation”.
Alcohol needs no digestion and is quickly absorbed. About 20% is absorbed directly into an
empty stomach and can reach the brain within one minute.
Alcohol Dehydrogenase – Enzyme that can reduce the amount of alcohol entering the blood by
about 20%. Women contain less of the enzyme than men, so more alcohol is absorbed (about
1/3 more than men of the same size).
After alcohol consumption, the liver must detoxify the body of alcohol, which impairs it’s ability
to metabolize fats. This can lead to elevated triglyceride levels and fatty liver over time.
HEALTH CONSEQUENCES OF CHRONIC ALCOHOL ABUSE:
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Fatty liver, and possibly cirrhosis
Elevated triglyceride levels in the
blood
Alcohol acts as a narcotic
alters amino acid and protein
metabolism (can lead to PEM)
weakens the body’s defenses against
infection
altered metabolism of medications
brain cells die with excessive
exposure
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acts as a diuretic, which can lead to
dehydration and electrolyte losses
can lead to malnutrition
can lead to weight gain (7 calories
per gram)
depleted folic acid levels
elevated homocysteine levels in the
blood
higher risk of colon and breast
cancers
higher risk of stomach ulcers
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