138
UNIT ONE
Understanding the pathways of metabolism and the
many steps and controls of protein synthesis (gene expres-
sion) can be daunting. Advances in computational science,
however, have vastly improved our ability to tease out the
meanings from these complex processes that underlie our
physiology. From Science to Technology 4.4 provides a
glimpse of this new “systems biology” approach to dissect-
ing the controls of how the human body functions.
PRACTICE
27
Distinguish between a mutation and a SNP.
28
How do mutations arise?
29
How do mutations af
ect health or appearance?
30
Describe protections against mutation.
STARTING MATERIALS
INTERMEDIATE #1
Enzyme #1
Enzyme #2
Enzyme #3
Enzyme #4
Enzyme #5
Enzyme #6
Enzyme #8
HEME
Enzyme #7
ALA dehydratase deficiency
acute intermittent porphyria
congenital erythropoietic
porphyria
porphyria cutanea tarda
coproporphyria
erythropoietic protoporphyria
porphyria variegata
INTERMEDIATE #2
INTERMEDIATE #3
INTERMEDIATE #4
INTERMEDIATE #5
INTERMEDIATE #6
INTERMEDIATE #7
FIGURE 4.26
Seven related but distinct inborn errors oF metabolism
result From abnormal or missing enzymes that catalyze reactions oF the
pathway For the synthesis oF heme, part oF the hemoglobin molecule
that is packed into red blood cells. In each disorder, the intermediate
biochemical that a de±
cient enzyme would normally af
ect builds up.
The excess is excreted in the urine or accumulates in blood, Feces, or
inside red blood cells. Some oF the symptoms include reddish teeth,
pink urine, excess hair, and photosensitivity.
2. Catabolism
a. Catabolism breaks down larger molecules.
b. In hydrolysis, a water molecule supplies a
hydrogen atom to one portion of a molecule and
a hydroxyl group to a second portion; the bond
between these two portions breaks.
c. Complex carbohydrates are decomposed into
monosaccharides, fats are decomposed into
glycerol and fatty acids, and proteins are
decomposed into amino acids.
4.3
CONTROL OF METABOLIC REACTIONS
(PAGE 117)
Metabolic processes have many steps that occur in a
speci±
c sequence and are interconnected. A sequence of
enzyme-controlled reactions is a metabolic pathway.
CHAPTER SUMMARY
4.1
INTRODUCTION (PAGE 115)
A cell continuously carries on metabolic processes.
Enzymes are critical to the reactions and pathways of
metabolism.
4.2
METABOLIC PROCESSES (PAGE 115)
Metabolic processes include two types of reactions,
anabolism and catabolism.
1. Anabolism
a. Anabolism builds large molecules.
b. In dehydration synthesis, hydrogen atoms and
hydroxyl groups are removed, water forms, and
smaller molecules bind by sharing atoms.
c. Complex carbohydrates are synthesized from
monosaccharides, fats are synthesized from
glycerol and fatty acids, and proteins are
synthesized from amino acids.
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