Cell Structure and Membranes
Common microscopic techniques
1. Light microscope (LM)
a. Magnify 1000x than specimens actual size
b. Cannot refine detail finer than 0.2 micrometre (um)
c. Great for studying living cells
2. Scanning electron microscope
a. Detailed study (topography)
b. Monitor viewing
c. Methods used to prepare kills the cells
3. Transmission electron microscope (TEM)
a. Study internal cell structure
b. Monitor viewing
c. Methods used to prepare kills the cells
Other techniques
1. Cell fractionation
a. Studies cell structure and function
Microscopic terms
● Magnification - Ratio between an object's image size to its real size
● Resolution - Measure of clarity of the image. Minimum distance of two points are
separated and still distinguished as individually
● Contrast - Difference in brightness between light and dark areas.
Prokaryotic
● DNA in a nucleoid, non membrane enclosed
● Absence of membrane bounded organelles
Eukaryotic
● DNA in nucleus, double membrane
● Generally larger in size
Similarities between the two
➔ Cytosol - semifluid
➔ Plasma membrane - selective barrier
➔ Chromosomes
➔ Ribosomes
➔ Cytoplasm
, Cell size limits: Each square micrometre of membrane, a limited amount of
substances can cross in a second. This is why the ratio of surface volume to area
is crucial. As cells grow, their volume grow exponentially quicker than the surface
area.
Compartmentalization in eukaryotic cells: Cells divided into compartment -
organelles. Helps specific metabolic functions and the cell to function
simultaneously.
Cell organelles:
➔ Nucleus
◆ Houses cells DNA
◆ Nuclear envelope:
● Encloses the nucleus
● separates contents from cytoplasm
● double membrane (lipid bilayer)
● Perforated by pore structures
● Pore complex: protein structure, lines each pore, regulates
entry/exit of proteins and RNA molecules
◆ Nuclear lamina:
● Protein filaments to help maintain shape of nucleus by
mechanically supporting pore complex
➔ Chromosomes
➔ Ribosomes
◆ Uses information to make proteins
Mitochondria:
● Uses oxygen to drive ATP by extracting energy from sugars, fats and other fuels.
● Animal cells
Structure
● Double membraned
○ Phospholipid bilayer
● Outer membrane = smooth; inner membrane = tangled with foldings called
cristae
● Two internal compartments formed by membrane
○ Intermembrane space: Narrow region between the inner and outer
membrane.
Common microscopic techniques
1. Light microscope (LM)
a. Magnify 1000x than specimens actual size
b. Cannot refine detail finer than 0.2 micrometre (um)
c. Great for studying living cells
2. Scanning electron microscope
a. Detailed study (topography)
b. Monitor viewing
c. Methods used to prepare kills the cells
3. Transmission electron microscope (TEM)
a. Study internal cell structure
b. Monitor viewing
c. Methods used to prepare kills the cells
Other techniques
1. Cell fractionation
a. Studies cell structure and function
Microscopic terms
● Magnification - Ratio between an object's image size to its real size
● Resolution - Measure of clarity of the image. Minimum distance of two points are
separated and still distinguished as individually
● Contrast - Difference in brightness between light and dark areas.
Prokaryotic
● DNA in a nucleoid, non membrane enclosed
● Absence of membrane bounded organelles
Eukaryotic
● DNA in nucleus, double membrane
● Generally larger in size
Similarities between the two
➔ Cytosol - semifluid
➔ Plasma membrane - selective barrier
➔ Chromosomes
➔ Ribosomes
➔ Cytoplasm
, Cell size limits: Each square micrometre of membrane, a limited amount of
substances can cross in a second. This is why the ratio of surface volume to area
is crucial. As cells grow, their volume grow exponentially quicker than the surface
area.
Compartmentalization in eukaryotic cells: Cells divided into compartment -
organelles. Helps specific metabolic functions and the cell to function
simultaneously.
Cell organelles:
➔ Nucleus
◆ Houses cells DNA
◆ Nuclear envelope:
● Encloses the nucleus
● separates contents from cytoplasm
● double membrane (lipid bilayer)
● Perforated by pore structures
● Pore complex: protein structure, lines each pore, regulates
entry/exit of proteins and RNA molecules
◆ Nuclear lamina:
● Protein filaments to help maintain shape of nucleus by
mechanically supporting pore complex
➔ Chromosomes
➔ Ribosomes
◆ Uses information to make proteins
Mitochondria:
● Uses oxygen to drive ATP by extracting energy from sugars, fats and other fuels.
● Animal cells
Structure
● Double membraned
○ Phospholipid bilayer
● Outer membrane = smooth; inner membrane = tangled with foldings called
cristae
● Two internal compartments formed by membrane
○ Intermembrane space: Narrow region between the inner and outer
membrane.
