Upload
arnold-hampton
View
214
Download
0
Tags:
Embed Size (px)
Citation preview
Cell Theory
• Every organism is composed of one
or more cells
• Cell is smallest unit with properties of
life
• Continuity of life arises from growth
and division of single cells
• Smallest unit of life
• Is highly organized for metabolism
• Senses and responds to environment
• Has potential to reproduce
Cell
Structure of Cells
All start out life with:– Plasma membrane – Region where DNA
is stored– Cytoplasm
Two types:– Prokaryotic– Eukaryotic
Surface-to-Volume Ratio
• Bigger cell, less surface area per unit
volume
• Above a certain size, material cannot
move in or out of cell fast enough
0.5 1.0 1.5
0.79
0.06
3.14 7.07
0.52 1.77
diameter (cm):
surface area (cm2):
volume (cm3):
surface- to-volume ratio: 13.17:1 6.04:1 3.99:1
Fig. 3-5, p.41
• Create detailed images of something that is too small to see
• Light microscopes– Simple or compound
• Electron microscopes– Transmission EM or Scanning EM
Microscopes
Limitations of Light Microscopy
• Cells must be thin enough for light to pass through
• Structures are usually stained
• Light microscopes can see details 200 nm in size
Electron Microscopy
• Uses beams of electrons rather than light
• Electrons are focused by magnets rather than glass lenses
• Can resolve structures down to 0.5 nm
Structure of Cell Membranes
• Fluid mosaic model
• Mixed composition:– Phospholipid bilayer – Glycolipids– Sterols– Proteins
Membrane Proteins
Adhesion proteins
Communication proteins
Receptor proteins
Recognition proteins
Passive transporters
Active transporters
• Archaebacteria and eubacteria
• DNA is not enclosed in nucleus
• Generally the smallest, simplest cells
Prokaryotic Cells
Eukaryotic Cells
• Have a nucleus and other organelles
• Eukaryotic organisms– Plants– Animals– Protistans– Fungi
Eukaryotic Cell Features
• Plasma membrane• Nucleus• Endoplasmic
reticulum• Golgi body• Vesicles• Mitochondria• Ribosomes• Cytoskeleton
• Keeps the DNA molecules separated from metabolic machinery of cytoplasm
• Makes it easier to organize DNA and to copy it
The Nucleus
Fig. 3-9a, p.46
DNA in nucleus
rough ER
smooth ER
Golgi body
chromatin nucleolusnuclear envelope(two lipid bilayers)
cytoplasm
pore
the cell nucleus
RNA messages
The Nucleus
• Related organelles where lipids are assembled and new polypeptide chains modified
• Sorts and ships products to various destinations
• Consists of endoplasmic reticulum, Golgi bodies, vesicles
Endomembrane System
Endoplasmic Reticulum
• Starts at nuclear membrane and
extends throughout cytoplasm
• Rough ER: ribosome covered,
processes proteins
• Smooth ER: no ribosomes, builds lipids
Golgi Body
• Puts finishing touches on proteins and
lipids that arrive from ER
• Packages finished material for shipment to
final destinations
• Material arrives and leaves in vesicles
Fig. 3-9e-f, p.46
budding vesicle
Golgi body
plasma membrane
Secretory pathway ends.
Endocytic pathway begins.
Golgi Body
• ATP-producing powerhouses
• Membranes form two distinct
compartments
• ATP-making machinery embedded
in inner mitochondrial membrane
Mitochondria
Chloroplasts
• Convert sunlight energy to ATP through photosynthesis
• Found in plants and some protistans
Organelle Origins
• Nucleus and ER– Infolding of membranes formed
compartments
• Mitochondria and chloroplasts– Endosymbiosis
• Present in all eukaryotic cells
• Cell shape and internal organization
• Allows organelle movement within cells and, in some cases, cell motility
Cytoskeleton
Microtubules
• Largest elements
• Composed of tubulin
• Involved in shape, motility,
cell division
tubulinsubunit
Microfilaments
• Thinnest elements
• Composed of actin
• Take part in movement,
formation, and
maintenance of cell
shape
actinsubunit
Intermediate Filaments
• Only in animal cells of certain tissues
• Most stable cytoskeletal elements
• Helpful in determining tissue types
onepolypeptidechain