Transcript A Tour of the Cell - Montgomery College

A Tour of the Cell
Chapter 6
Objectives
• Be familiar with the regions of the cell and
the overall role of each region
• Be familiar with the basic organelles and
their function
• Be familiar with the way neighboring cells
can communicate
Cell Types
• All living organisms
are made of cells
• Two kinds of cells
– Prokaryotic: lacks
membrane bound
structures other than
plasma membrane
• Bacteria
– Eukaryotic: contains
membrane bound
organelles enabling
compartmentalization
leading to
specialization
• animals, plants, protists,
fungi
Cell Size
• Limits on cell size
determined by ability
to perform metabolic
processes
– Lower: can all
necessary components
fit
– Upper: can we regulate
supplies adequately
(surface to volume
ratio)
Regions of a Eukaryotic Cell
• Nucleus: contains genetic material (DNA)
necessary for cell regulation. Reference
library
• Cytoplasm: consists of cytosol (cell fluid)
and organelles (specialized structures that
carry out metabolic activities of cell)
• Plasma Membrane: contains the cell and
regulates movement of materials into/out of
the cell
Cell Overview
Nucleus
• Control center of cell
• Dual membrane
system that fuse to
form nuclear pores
• DNA and Protein
complexes called
Chromatin
• Nucleolus: region of
RNA within the
Nucleus
Nuclear Pore Structure
• To get materials into the
nucleus there is a 27
Amino Acid tag (zip code)
added onto molecules and
are assisted by proteins
called importins
• To leave the nucleus
exportin proteins, a
specific zip code, GTP
and Ran are required
Import Summary
Ribosomes
• Sites of Protein
synthesis
• May be free or bound
– Free make proteins
typically used in the
cell
– Bound are attached to
membrane (ER) and
make proteins typically
for export
Endoplasmic Reticulum (ER)
• Part of the
endomembrane system
• Smooth ER: site of
lipid synthesis, detox,
carbohydrate
metabolism
• Rough ER: site of
protein synthesis
(contains bound
ribosomes)
Golgi Apparatus
“When it absolutely, positively, has to leave the cell”
• Finishes, sorts, and
packages
manufactured products
of the cell
• cis: receives products
from “ER”
• trans: ships materials
to other parts of cell
(often the plasma
membrane)
Lysosomes
• Membrane bound
structures responsible
for the degradation of
“spent” organelles and
“food” items
• Contain hydrolytic
enzymes
Vacuoles
• Membrane bound
storage areas for
resources
• Named after the
resource they contain
Mitochondria, Chloroplast
• Mitochondria: site of
most ATP synthesis
• Chloroplast: site of
carbohydrate synthesis
Peroxisomes
• Modify molecules
through redox
reactions (fatty acid)
• Produce peroxide as a
result (H2O2)
• Split into two as they
grow
Cytoskeletal
elements
• Provide structural
framework for the cell
• Movement of materials
inside and on the surface of
the cell
• Microtubules
– grow from centrosome
– load bearing
• Microfilaments
– pulling forces
• Intermediate filaments
– pulling forces
Organelles of Motility
• Flagellum: moves the entire cell
• Cilium (cilia): moves things along the surface of
the cell
Extracellular Surfaces
• Most cells have a
combination of proteins,
lipids and sugars that form
an extracellular matrix
• Plants have a cell wall
What distinguishes one cell’s
function from another?
• The quantity and type
of organelles
determine how the cell
can function.
Communication is Critical
• Connections between cells
are called junctions
– Tight junctions: leakproof connections
between cells
– Desmosomes: fasten
cells together
strengthening the tissue
– Gap junctions:
provide cytoplasmic
channels between cells
– Plasmodesmata: plant
cell channels
• In order for many cells to
function as a unit (as in
multicellular organisms)
there must be a minimal
level of communication