Introduction to cells and how we study them

Question 1

What are cells?

Answer 1

Cells are an organism’s basic units of structure and function
The cell is the smallest unit of organization that can perform all the activities required for life

Question 2

What can cells do?

Answer 2

• Are enclosed by a membrane
• Use DNA as their genetic information
• Cells can divide, this is the basis of all reproduction, growth, and repair of uni- or multi-cellular organisms
• all cells arise from cells

Question 3

What does cell theory states?

Answer 3

• All organisms are composed of one or more cells
• Cells are the smallest living things – the basic units of structure organisation of all organisms
• Cells arise only by division of a previously existing cell

Question 4

Light Microscope

Answer 4

visible light is used to
illuminate the specimen, the light then passes
through glass lenses, magnifying the image

Question 5

Microscope staining

Answer 5

Staining enhances contrast
Disadvantage: cells must be fixed
– kills them

Question 6

Microscope staining techniques.

Answer 6

Fluorescence: Detect the locations of
specific molecules in cells;stains bind to
specific molecules, absorb
UV light and emit visible
light
Phase-contrast: Enhances contrast in unstained cells
by amplifying variations in density; unpigmented cells
Differential-interference-
contrast (Nomarski): Uses optical modifications to
exaggerate differences in density –
making the image appear almost 3-D
Confocal: Fluorescent “optical sectioning”; uses a pinhole aperture; creating a single plane of
fluorescence in the image.
By capturing sharp images atmany different planes, a 3-D reconstruction obtained

Question 7

Electron Microscope

Answer 7

Scanning electron microscopes (SEMs): focus a
beam of electrons onto the surface of a specimen,
providing images that look 3-D
Transmission electron microscopes (TEMs): occurs a beam of electrons through a specimen

Question 8

Preparation of samaples

Answer 8

TEM:Specimen embedded in plastic and cut very
thin.Stained with atoms of heavy metals, which
attach to certain structures – enhance density * Preparation can introduce artifacts
SEM: coated with a thin layer of gold

Question 9

Cell fractionation

Answer 9

Process used to separate cellular
components while preserving individual
functions of each component.
– centrifugation of broken up cells
– subcellular structures separate according to
their size and density