Transcript Function of the Cell Membrane

CELLS
Structure and Function
Cell = smallest unit of life
Cell Theory
1. All living things are made of cells
2. Cells are the basic unit of structure
and function
3. All cells come from pre-existing cells
Two Major Cell Types
Cell Type
Prokaryotic
Eukaryotic
Example
Bacteria
Protists
Fungi
Plants
Animals
Prokaryotic Cell
Eukaryotic Cell
(protist, animal)
Eukaryotic Cell
(plant)
Differences Between Cell Types
Prokaryotic Cell
Single circular
chromosome
Eukaryotic Cell
Multiple linear
chromosomes
Chromosome found Chromosomes found
in a cytoplasmic
in a membraneregion called the
bound nucleus.
nucleoid.
No internal
membranes
Some infolded
plasma membrane
Extensive network of
internal membranes
Common Components
and Cellular Organization
• Plasma Membrane
– boundary surrounding the cell
• Genetic material: DNA
– located in a membrane-bound nucleus
for eukaryotic cells
• Cytoplasm
– Semi-fluid matrix containing enzymes
and organelles
(enzyme = biological catalyst)
• Cytoskeleton
– network of filaments and tubules in cytoplasm
that maintains cell shape, allows movement
Features of
Prokaryotic Cells
All prokaryotic cells contain
Structure
Plasma
Membrane
Nucleoid
Cytoplasm
Function
Regulates flow of
substances into and out
of cell
Cytoplasmic region
containing genetic
material
Cytosol: fluid
Ribosomes
Enzymes
Features of
Prokaryotic Cells
Other possible prokaryotic structures
Structure
Cell Wall
Capsule
Infolded Plasma
Membranes
Function
Supports cell
Maintains shape
Protects from drying
Protects against
white blood cells
Metabolism
Cell division
Features of
Prokaryotic Cells
Other possible prokaryotic structures
Structure
Bacterial
Flagellum
Plasmid
Function
Movement
Small circular DNA
Replicates
independently
Applying Your Knowledge
1.
2.
3.
4.
5.
Cell Wall
Flagellum
Capsule
Plasmid
Nucleoid
In bacterial cells
• where is the genetic material located?
• which one is used for movement?
• which one provides structural support
for the cell?
Thought Questions
1. What are similarities for
a. eukaryotic and prokaryotic cells?
b. animal and plant cells?
2. What are differences between
a. eukaryotic and prokaryotic cells?
b. animal and plant cells?
Functions of Eukaryotic Cell Features
Structure
Function(s)
1. Regulates passage of
Plasma
materials into and out of cell
Membrane
2. Cell-Cell Recognition
END DAY 1
Function of the Cell Membrane:
• Cell membrane separates the components of a cell
from its environment—surrounds the cell
• “Gatekeeper” of the cell—regulates the flow of
materials into and out of cell—selectively permeable
• Cell membrane helps cells maintain homeostasis—
stable internal balance
Passive Transport
A process that does not require energy to move
molecules from a HIGH to LOW concentration
 Diffusion
 Facilitated Diffusion
 Osmosis
• Diffusion is the movement of small particles across a
selectively permeable membrane like the cell membrane
until equilibrium is reached.
These particles move from an area of high concentration
to an area of low concentration.
outside of cell
inside of cell
• Osmosis is the diffusion of water through a selectively
permeable membrane like the cell membrane
Water diffuses across a membrane from an area of high
concentration to an area of low concentration.
Semi-permeable
membrane is
permeable to water,
but not to sugar
• Facilitated Diffusion is the movement of larger
molecules like glucose through the cell membrane –
larger molecules must be “helped”
Proteins in the cell membrane form channels for large
molecules to pass through
Proteins that form channels (pores) are called protein
channels
outside of cell
inside of cell
Glucose molecules
Click
Hypertonic Solutions: contain a high concentration of solute
relative to another solution (e.g. the cell's cytoplasm). When
a cell is placed in a hypertonic solution, the water diffuses
out of the cell, causing the cell to shrivel.
Hypotonic Solutions: contain a low concentration of solute
relative to another solution (e.g. the cell's cytoplasm). When
a cell is placed in a hypotonic solution, the water diffuses
into the cell, causing the cell to swell and possibly explode.
Isotonic Solutions: contain the same concentration of solute
as another solution (e.g. the cell's cytoplasm). When a cell is
placed in an isotonic solution, the water diffuses into and
out of the cell at the same rate. The fluid that surrounds the
body cells is isotonic.
Click
Active Transport
Active transport is the movement of molecules from LOW to HIGH
concentration.
Energy is required as molecules must be pumped against the
concentration gradient.
Proteins that work as pumps are called protein pumps.
Ex: Body cells must pump carbon dioxide out into the surrounding
blood vessels to be carried to the lungs for exhale. Blood vessels are
high in carbon dioxide compared to the cells, so energy is required
to move the carbon dioxide across the cell membrane from LOW to
HIGH concentration.
outside of cell
inside of cell
Carbon Dioxide
molecules
ANALOGY:
ENERGY NEEDED:
Active Transport
NO ENERGY NEEDED:
Diffusion
Osmosis
Facilitated Diffusion
• Endocytosis and Exocytosis is the mechanism by which
very large molecules (such as food and wastes) get into
and out of the cell
Food is moved into the
cell by Endocytosis
Wastes are moved out
of the cell by
Exocytosis
END DAY 2
Analogy
If the cell were a factory
the ____________________ would be
(name a cell component)
a _____________________________.
(name a part of a factory)
Part of Cell
Part of Factory
Capsule
Security Gate
Cell Wall
Outer Fence around the factory
Chloroplast
Solar Panel
Cytoskeleton
Moving Belt where items are inspected
Steel Support, Interior Walls
Cilia/Flagella
Conveyor Belt, Elevator/Escalator
Enzyme
Worker; Assemblage Machinery
Golgi Complex
Distribution/Packaging Department
Mailroom
Mitochondrion
Generator, Engine Room, Power Source
Nucleoid
Storage of pre-production material
Nucleus
Supervisor’s Office, Boss
Corporate Office, Central Operations
Plasma Membrane
Loading/Unloading Dock, Inner Wall, Door
Ribosomes
Assembly Line Track
RER
Production Line
SER
Shipping Dock
Cellular Interactions
 Signal Transduction: passing a signal
from the cell surface to the interior
 First messenger binds to
Cell Surface Receptor
 Receptor signals nearby
Regulator Protein
 Regulator activates
nearby enzyme
 Enzyme catalyzes formation
of Second Messenger
 Second Messenger initiates
Cellular Response
Cellular Interactions
 Cell Adhesion: joining of cells
controlled by proteins called
Cellular Adhesion Molecules
(CAMS)
important in
 Inflammatory Response
 Placenta Formation
 Learning and Memory
Lack of cell adhesion is
implicated in cancer
and arthritis.