Week 3 MPW Lecture 1

Question 1

What is the most efficient way for evolution to use?

Answer 1

Building evolution from a series of independent events. Evolution would take any mechanism and conserve it if it is useful. Not the most efficient but works.

Question 2

What are the functions of membranes?

Answer 2

Evolutionary perspective:
a) act as a barrier between inside and outside
permit and regulate transport of nutrients (and waste) – channels
b) developed the ability to do this against a concentration gradient – pumps
c) All cells can do this. ‘original’ role of barrier
d) Later developments:
Conversion of membrane potential/gradient to energy (most cells do this)
e) Cellular recognition (eukaryotes and prokaryotes, but different)
f) Signalling from outside to inside (all cells do this, but no universal system)
g) Movement of molecules within the eukaryotic cell, contained within vesicles (membrane trafficking)
h) Compartmentalisation (only in eukaryotes)
i) Nerve impuleses

Question 3

What is the difference between a channel, a transporter, and a pump?

Answer 3

Channel:

a) Is a pore in the cell that allows some molecules through
b) Pump:
i) Requires energy to move molecules against there concentration gradient
c) Transporter
i) When 1 molecule uses the concentration gradient from another molecule to transport the molecule.

Question 4

Are cell membranes actually impermeable? What kind of molecules can travel through them?

Answer 4

Small non charged molecules. Some molecules need a channel like water, uses aquaporins.