Lecture 8

Question 1

Compare and contrast the structures and functions of microtubules, microfilaments and intermediate filaments

Answer 1

Microtubules - hollow cylinders made up of many subunits of a globular protein = tubulin
(main cell structure, attach to chromosomes during cell division, very important for organising activities in the cell
Microfilaments - much thinner, consist of twisted pairs of polymers of actin subunits
(involved in cell motility and changes cell shape, supports shape of microvilli)
Intermediate filament - consists of fibrous proteins i.e. keratin arranged in supercoils
(forms nuclear lamina)

Question 2

Explain how a signal molecule that doesn’t enter the target cell can produce a large cellular

Answer 2

There are three steps:
Signal reception, in which a
signal molecule interacts with a receptor protein in the plasma membrane, causing a
change in shape which starts off a set of interactions in a relay of molecules.
This
relay is the transduction process.
Finally, the transduction pathway ends when a
response is activated at its destination. The signal molecule does not enter the cell