Structure and Function of the
Cell
Cells make up all living things
Resolution is important for cell
research
Cells are the basic unit of life
Cells
Tissues
Organs
Organ systems
Organisms
CELL THEORY
• 1665 – Robert Hooke observes cork is
made of little compartments he calls
“cells”
• 1674 – Leeuwenhoek observes living
cells for the first time - animalcules
• 1838 – Schleiden determines all plants
are made of cells
• 1839 – Schwann determines animals are
made of cells
CELL THEORY
• 1850 – Brown discovers the dense
centers of certain cells and names the
nucleus
• 1855 – Virchow discovers cells make
more cells
THREE POINTS OF THE
CELL THEORY
• All living things are made up of one or
more cells
• Cells are the basic unit of structure
and function in living things
• Cells come from previously existing
cells – NO spontaneous generation!
There are two major types of cells:
Prokaryotes: literally means “before
nucleus”
 primitive single celled life, the first!
example: all bacteria
 DNA lives in cytoplasm
no membrane bound organelles
extremely small (even for a cell!)
http://learn.genetics.utah.edu/content/begin/cells/scale/
Prokaryotes Vs. Eukaryotes
Eukaryotes:
- literally means “true nucleus”
- DNA enclosed by the nuclear membrane
- Can be single celled like protists
(amoebas, paramecium)
- Or can be part of a multicellular
organism like: plants, animals or fungi
Prokaryotes Vs. Eukaryotes
Eukaryotes:
- significantly larger than prokaryotic cells
- have many more organelles than
prokaryotic cells
All cells must perform certain tasks to stay
alive
Just how they go about it might be a little
different depending on what organelles
they have to work with.
Study of the Cell:
1.Cells must regulate what enters and leaves
the cell.
2. Cells must obtain and metabolize nutrients
for the purpose of energy.
3. Cells must grow and reproduce.
4. Cells must synthesize, modify and ship
proteins to their destinations.
Will talk about along the way
5. Cells must be able to store nutrients, isolate
and digest damaged organelle and potentially
harmful chemicals
6. Cells must be structured in a particular way
and be mobile if necessary.
Regulating what goes in and out
of the cell
• Cell Membrane
•
http://www.northland.cc.mn.us/biology/biology1111/animations/index_page_for_animations.htm
•
http://www.youtube.com/watch?v=gOxRXn5r9Jo
Movement with no energy
• Diffusion – through the phospholipid
bilayer
• Facilitated diffusion – through proteins that
require no energy (channel proteins)
• Osmosis – transport of WATER through
channel proteins
Active Transport – Energy
required
• Movement across membrane goes through
special proteins that require energy to work
• These proteins pump ions (mostly) from
areas of LOW concentration to areas of
HIGH concentration (against a gradient)
• Exocytosis and endocytosis also require
energy (movement of LARGE molecules)
Exocytosis (Golgi and vesicles)
Endocytosis (Phagocytosis)
Obtaining Energy – Eucaryotes,
not plants
• Many protists use endocytosis
• Humans foods are broken down to
monomers which are small and do not
require endocytosis
• Plants make their own food (so don’t need
to bring in food, they make it!
Obtaining energy: Plants
Leaves are the organ, that contain
cells that contain chloroplasts
Obtaining energy - Plants
Chloroplasts capture the sun’s energy -------------- glucose
Plants can create proteins and
lipids too!
Animals eat carbs. proteins and
lipids
Metabolize Nutrients – Animals
can use what they eat and “revise”
mitochondria
Purpose of vesicles (as related to
cell membrane)
• To move food and hormones into the cell
(endocytosis),
• These vesicles are called endosomes
• To move material out of the cell (exocytosis)
– These vesicles are called secretory vesicles
– To provide a “reaction location” that is separated
from the cytosol (lysosomes, peroxisomes)
Cell Growth and Reproduction
• DNAchromosomes
• duplicate and
divide
New cells
formed
Cell Growth leads to….
• Larger number of cells, cell differentiation
Cells must be able to synthesize
protein
Cells must be able to modify and
ship proteins (and lipids)
Microscopes
• Tools
– Objects used to improve the performance of a
task
• Microscopes
– Extend human vision by enlarging, with high
resolution, things that might be impossible to
see.
Light Microscopes
• Use light (photons) to view specimens
– Two types
• Stereo (dissecting) microscope
– 40x – 70x magnification (in general)
– 3D view (two eye pieces)
– Live specimens can be viewed, but often used to
compare two things (ballistics, etc)
• Compound Light Microscope
– Magnifies using two lenses – 1000x – 2000x
– Thick objects must be sliced thin enough so that light
passes through
Paramecium – Light microscope
Magnification vs. Resolution
• Magnification
– Increase in an object’s apparent size
• Resolution
– Minimum distance between two objects at
which the objects can just be determined as
separate.
– No resolution in light microscopes beyond
2000x
Electron Microscopes
• A beam of electrons produces an enlarged image
• Higher magnification (up to 2,000,000x) and
resolution (use electrons rather than photons) than
light microscopes
• Always black and white (color is added by
computer, electrons do not emit a color)
• Always ,dead (specimen must be in a vacuum
chamber so… no air)
Scanning EM
• Surface scanning
• 3D
• Gold coated and electrons are “fired” at the
metal coating (metal emits other electrons
and these are projected onto a photographic
plate (100,000 – 200,000x)
Paramecium – SEM
SEM
Transmission
• Transmits electrons THROUGH a very
thinly sliced specimen
• Magnetic lenses enlarge the impage
• Magnification 200,000x to 2,000,000x
TEM cross- section
Paramecium Organelles
Units of measure in Microscopy
• Metric system
– Consists of base unit
• Length = meter (m)
• Mass = gram (g)
• Volume = liters (l)
• We will use units of length (meters) to
describe the size of organisms
Prefixes
Prefix
prefix abbr
• Nano
n
• Micro
u or m
• Milli
m
• Centi
c
• NO prefix
A
unit
nm
mm
mm
cm
= 1 x ____ meters
10-9
10-6
10-3
10-2
Angstrom
10-10