The Cell
Learning Objectives
The Cell: Driving Questions
• How do cells live up to the name, “the basic unit of
structure and function”?
• How do evolution and surface area : volume
relationships drive cell structure and function?
• How do the various parts of a cell work together?
• How does molecular traffic move through cell
membranes?
• What are the basic components of cell-to-cell
communication?
• Why do cells divide, and how is the cell cycle
regulated?
A word from the top…
• This unit should be be straight forward
• It should only take 2.5 weeks, even with lab
work.
• Make the lab work central to your cell unit
– Diffusion Osmosis
– ‘Scope Lab looking at different types of cells
– AP Lab 3A (mitosis simulation and ID of phases
of mitosis)
• We should continue to develop students’ microscopy
skills
Chapter 6, Students need to
know…
• The difference between prokaryotic and eukaryotic cells.
• The structure and function of eukaryotic organelles
• The way organelles work together to facilitate cell function,
with particular emphasis on the endomembrane system
and protein synthesis and secretion
• How prokaryotes perform cellular functions without
organelles
• the essential concept of surface area to volume
relationships (SA:Vol), and how that relationship drives the
evolution of cell shape and the evolution of membranebound organelles. Surface area to volume also governs
transport across membranes.
What is a cell?
• Helpful to mention what a cell is not…
• Prokaryotic
• Eukaryotic
What is a cell?
Example
Basic Unit
Cells
Can cells survive on their own?
Structure =
Function
Interactions
With
Environment
Dynamic
Balance
Evolutionary
Connections
Prokaryotic Cells:
What limits a cell’s size?
Eukaryotic Cells: What limits a
cell’s size?
It’s important to remember what
cells have in common
It’s important to realize what makes
different cells unique
•
•
•
•
What Do Cells Do?
Why Cells?
• Division of Labor
• Multiple metabolic functions
in one cell
• Multiple Functions within an
organism
• Repair and reproduction
• Increased surface area
to volume ratio!
How does a eukaryotic cell compensate for
lower surface area to volume ratio?
• INTERNAL MEMBRANES (Endo-Membrane
System)
• Partition cell into compartments
• Internal Membranes have unique Lipid and
Protein compositions, therefore…
• Participate in metabolic activities
• Provide Localized Environment for specific
metabolic processes
• Sequester, or isolate, certain reactions so they
don’t interfere with other metabolic processes
Chapter 6 cont, Students need to
know…
• The structure and function of the following:
– the various components of the cytoskeleton,
– plant cell walls,
– the animal Extra Cellular Matrix (ECM)
– intercellular junctions (plasmodesmata, tight
junctions and gap junctions).
• Why: the cytoskeleton and the intercellular
space is the place where cells
communicate.
Cytoskeleton = Mechanical Support
and Cell Motility
Continuing with the theme of what a cell is not. Check out Table 7.1
Microtubules
• largest
• made of tubulin
• Easy to make, easy
to break
• Essential for moving
things around the cell
Microtubule Monorails!
• Vessicles don’t move
by magic…
• Chromosomes aren’t
“pulled” by
microtubles, they walk
during anaphase
•
Centrosome: MTOC
Microtubules = Cilia and Flagella
• This is a great place
to discuss Unit and
Diversity
9 + 2 Ultrastructure
• The parts
matter…
• Pairs of
microtubles
connected by
Dynein,
• Everyone pulls
one way…and
the whole thing
“falls over”
tension and
release”
“9+2” + Cross linked Proteins =
• Beating of cillia
and
• Undulation of flagella
Microfilaments: Actin Filaments
• The smallest
components of the
cytoskeleton
• Provide tension for
pulling…can’t
mention actin without myosin
•
•
Microfilaments = cell motility
• Sliding filaments of
skeletal muscles*
• The reason for
cytoplasmic
streaming
Microfilaments = cell motility
• Microfilaments
provide the
possibilitity of
pseudopodia
• Microfilaments are
the reason for
cytokinesis/cleavage
Intermediate Filaments
• The name says it
all…
• The toughest
components of the
cytoskeleton
Intermediate Filaments =
Structural Integrity
Extra Cellular Matrix
• The integrins
• The Fibronectins and Collagen
• The Interstitial fluid
Extra Cellular Matrix: Plants
• 1º Cell Wall
• 2º Cell Wall
• Middle Lamella
• Plasmodesmata
Extra Cellular Matrix
aka “biofilms” or interstitial space
Cell-To-Cell Junctions
• Tight Junctions
• Desmosomes
• Gap Junctions
• Plasmodesmata
Cell-to-cell Communication
Chapter 7, Students need to
know…
• The fluid mosaic model of cell membranes
and the constituent parts.
• Cell membranes are ambiphatic and semipermeable
• Membrane proteins give cell membranes
their specific functions
• Membrane proteins have varied, yet
crucial, roles in cell function
Cell Membranes
• Irving Langmuir
(1917)
• Davidson and
Danelli (1935)
• Singer and
Nicholson (1972) =
• Fluid Mosaic Model
of Cell Membranes
Fluid Mosaic Model of Cell Membranes
Cell Membranes
are Selectively
Permeable
• Why?
• What’s Moving?
Fluid Mosaic:
The Lipids
Why the change in lipid
components?
What organelle is responsible
for these changes?
Fluid Mosaic Model of Cell Membranes
The cell is able to take up many varieties of small
Molecules and ions and exclude others.
The fluid mosaic model helps explain how membranes
regulate the cell’s molecular traffic.
Fluid Mosaic: The Proteins I
The Proteins II
Fluid Mosaic: The Proteins II
Chapter 7, Students need to
know…
• The concept of diffusion
• The concept of tonicity, and they need to be able
to differentiate between hypotonic, isotonic and
hypertonic environments. They need to do this for
the cytoplasm as well as the extracellular space.
• How to predict if a molecule will move across the
cell membrane and which direction it will move
across the cell membrane
• The difference between diffusion, osmosis,
facilitated diffusion, and active transport
• Two or three examples of active transport
• Bulk transport including endo- and exocytosis
How do molecules move
across membranes?
What is osmosis?
What the heck is “water potential”?
What is Tonicity?
•
•
•
What is water balance?
How do molecules move across a membrane?
• Diffusion:
Net movement of
molecules along a
concentration gradient
from an area of
[hi] to [lo]
• Osmosis:
The net movement of
water molecules along
a [gradient] across a
(semi-permeable)
membrane
•
•
Facilitated Diffusion
• This is still passive
transport…with a
twist.
• Specific solutes
move through
specific integrins
• Think of integrins as
“phsyical catalysts”
Active Transport
• What?
• The cell uses energy
(ATP) to pump a
molecule across a
membrane, against its
concentration gradient.
• So What?
• Examples:
Speeds the transport of a solute
(by providing an
efficient passage),
does not change the
direction of diffusion
Na/K Pump = Membrane Potential
• How it works:
• Membrane Potential is…
A chemo-electric gradient
Proton Pumps: A more “primitive”
Active Transport
• What it is:
• It also generates a…
• Electrochemical gradient:
Cotransport
• Using a proton pump
to pump something
else into a cell…
• Uses the potential
energy of a H+
gradient to drive active
transport of other
solutes.
Vesicle Transport or “Bulk Transport”
• Endocytosis
– Phagocytosis
– Pinocytosis
– Receptor Mediated
• Exocytosis = secretion
Fluid Mosaic: Membrane Synthesis
Chapter 10, Students need to
know…
• The Signal Transduction pathway.
• The difference in structure and function of
a G protein communication pathway vs. a
Tyrosine-kinase pathway.
• All signals will be amplified by a cascade
of enzymes; so only a small amount of
signal is needed.
Cell Signaling Basics
• Almost all cells communicate
– Locally: cell-cell
– “Regionally”
– Long-Distance
• Small set of signaling mechanisms show up
throughout the Domain Eukarya
– Development, Hormone Action, Cancer, Immune
Response, CNS/PNS, Plant response
• Cells most often communicate chemically
• Cells receive, process, and respond to signals
Types of Cell Signaling
Don’t forget Cell-to-cell: gap jcts., plasmodesmata, immune cells
Cell Signaling: The Big Picture
What does “cellular response” mean?
•
•
•
And now…a little more detail.
Signal molecule
Is not passed along
And now…even more detail
Another Response:
2nd Messengers
2nd Messengers are…
Small, nonprotein,
water-soluble molecules
Because 2nd messengers
are small and water
soluble, they diffuse easily
within the cytosol and
amplify a response.
Chapter 11, Students need to
know…
• The phases of mitosis and their relationship
to the Cell Cycle.
• The phases of the Cell Cycle and their
relationship to mitosis.
• The internal controls of the cell cycle. Special emphasis
should be placed on Checkpoints (see Figure 12.14) and
the importance of cyclins and kinases in pushing the cell
through these checkpoints.
• The basics of external influences on cell division
• The basic characteristics of cancer cells
The Cell Cycle (formerly Mitosis)
• Rudolf Virchow (1855)
– Where a cell exists…
• Omina cellula e cellula
The Cell Cycle: Nuts and Bolts
Pg. 219 Campbell and
Reese (7th Ed.)…
Chromosomes
The Cell Cycle
Phases of Mitosis (nuclear division)
• Interphase
• Prophase
• Prometaphase
• Metaphase
• Anaphase
• Telophase and Cytokinesis
Microtubules = Mitotic Spindle
Cytokinesis: Animal Cells
• Cleavage furrow
Cytokinesis: Plant Cells
• New Cell Wall along
the cell plate (the
former metaphase
plate)
of Kinetichores and microtubules
Cell Cycle Regulation
(cell cycle control):
A cyclically operating set of molecules in the cell that triggers and
coordinated key events in the cell cycle.
Internal Regulation
• Check points: a critical
control point…
• Go-ahead Signals…
• Whose responsible?
Kinases are responsible…
…Sort of.
• Kinase…
• Cdk…
• MPF…
Internal Control: Three checkpoints
G1: The “restriction pt.”
G2: (MPF)
M: (kinetichores
and intracellular signaling)
Cell Cycle: External Regulation
• Chemical:
• Physical:
Cancer: When Cycle Short Circuits
Cancer Cells:
What?
Why?
Other characteristics:
How?
But what about bacteria?