Video Transcript
Which of the following best
describes the structure of an actin filament? (A) A thick filament with a
globular head and a cylindrical tail. Or (B) a thin filament that is made
up of two molecules twisted around each other.
Actin is a protein filament that is
found in muscle fibers. To answer this question, let’s take
a look at these filaments in more detail. Muscle fibers contain rodlike
organelles called myofibrils, which in turn are made up of repeating sections of
different types of protein filaments: a thin protein filament called actin and a
thicker protein filament called myosin. They also contain another thick
filament called tropomyosin, which helps to regulate the interaction of actin and
myosin and control muscle contraction.
The thin protein filament actin is
made up of two strands that are twisted around each other. The thicker filament, myosin,
consists of long rod-shaped fibers that have a globular head and a cylindrical
tail. This provides us with enough
information to answer our question correctly. The answer choice that best
describes the structure of an actin filament is (B): a thin filament that is made up
of two molecules twisted around each other.
