Parts of the Cell
Undifferentiated Animal Cell (generic or unspecialized)
Differentiated (Specialized) Cells
Cytoplasm
• Cellular material outside nucleus and inside the plasma
membrane
• Cell activities and chemical reactions takes place here=
mostly water
• 3 parts:
a. cytosol- semi-transparent fluid
that suspends other elements
(mostly made of water)
b. organelles
c. inclusions- non-functional units in cytoplasmfat droplets, pigments, glycogen, mucus
Cell
Junctions
Tight Junctions
Desmosomes
Gap Junctions
Tight junctions
• Joins one cell membrane with
the next.
• Fuses like a zipper
Desmosome
• Cell anchors
• Prevent cells subject to stress from
being pulled apart
• Button-like connections with
filaments
Gap Junctions
• Allows for communication
between cells
• Accomplished with
chemicals
• Connected with hollow
cylinders called connexons
Cytoskeleton
Scaffolding of cell; forms internal framework
Consists of:
a. Microtubules- long, hollow
cylinders
Function::
• support structure
• Form centrioles and cilia, flagella
• helps cell change shape
b. Microfilaments- tiny, thread-like
fibers
Function:
• anchor, support
• help muscle cells contract
(actin and myosin)
c. Intermediate Filaments- tough, rope-like
proteins
Attached to desmosomes
Function:
• Act as internal “guide wires”
• Resist pulling forces on cell
Cellular Transport
Notes
Plasma Membrane
All cells have a cell membrane
Functions:
a. Controls what enters and exits the cell to
maintain an internal balance called
homeostasis
b. Provides protection and support
TEM picture of a
real cell membrane.
Structure of cell membrane
Phospholipid Bilayer –
2 layers of phospholipids
a.Phosphate head is polar
(water loving)=
hydrophilic
b.Fatty acid tails non-polar
(water fearing)=
hydrophobic
Phospholipid
Lipid Bilayer
Cell membranes have pores (holes) in it
a.Selectively permeable: Allows some molecules
in and keeps other molecules out
Water soluble
Fat soluble
Pores
Structure of the Plasma Membrane
Carbohydrate marker
4 parts of plasma membrane:
1.
2.
3.
4.
Types of Membrane Proteins
1. Integral- into or all the way through membrane
2. Peripheral- attached to the outside of membrane
Types of Cellular Transport
•Animations of Active
Transport & Passive
Transport
•
Weeee!!
!
Passive Transport
cell doesn’t use energy
1. Diffusion
2. Facilitated Diffusion
3. Osmosis
•
high
Active Transport
low
cell does use energy
1. Solute (protein) Pumps
2. Endocytosis
3. Exocytosis
This is
gonna
be hard
work!!
high
low
Passive Transport
•
•
•
cell uses no energy
molecules move randomly
Molecules spread out from an area of high concentration to an
area of low concentration.
• (HighLow)
Goes down the
concentration gradient
Weeee!!!
high
low
3 Types of Passive Transport
1. Simple Diffusion – through the phospholipid bilayer
2. Facilitative Diffusion – diffusion with the help of transport proteins
3. Osmosis – diffusion of water
Diffusion
Animation of
diffusion
random movement of particles from an area of
high concentration to an area of low concentration.
•
Diffusion continues until all molecules are
evenly spaced (equilibrium is reached)-
•
Movement is caused from random
collisions of particles
http://bio.winona.edu/berg/Free.htm
Simple Diffusion
Lipid (fat) soluble molecules pass directly through the cell membrane
Ex: fats, CO2, O2, steroids, ethanol, general anesthetics
Facilitated diffusion
Diffusion of specific particles through transport proteins
found in the membrane
a. Transport Proteins are specific – they “select” only certain molecules to cross the
membrane
b. Transports larger or charged molecules
Examples: H2O, amino acids, glucose, ions such as H+, Na+, Cl-, Ca2+
Channel Protein
Requires no energy !!!
Carrier Protein
Channel Proteins animations
Osmosis
Osmosis
animation
diffusion of water through a
selectively permeable membrane
• Water moves from high to low
concentrations
aquaporins
•Water moves freely
through pores.
•Solute (green) is too large to
move across.
Filtration
• Forces molecules through a membrane by exerting pressure
High  Low pressure
Hydrostatic pressure- will force water molecules through to the other
side of a membrane while large solid particles are left behind
Example: water in blood forced out through capillaries , but blood cells
and large particles in the plasma remain inside.
-------------------------------------------------------------------------Example: Kidneys- pressure forces solute from the
blood across a membrane and into the nephron
Active Transport
•cell uses energy
•actively moves molecules to
where they are needed
•Movement from an area of
low concentration to an area
of high concentration
This is
gonna be
hard
work!!
high
•(Low  High)
•Three Types:
low
1. Protein or Solute Pumps
require energy to transport in
and out of the cell
Sodium
Potassium Pumps
(Active Transport
using proteins)
Example: Sodium / Potassium
Pumps are important in nerve
responses.
Protein changes
shape to move
molecules: this
requires energy!
2. Endocytosis:
taking bulky material into a cell
•
•
•
•
Uses energy
Cell membrane in-folds around food
particle
“cell eating”
forms food vacuole & digests food
•
This is how white blood cells eat bacteria!
a. phagocytosis- solids
b. Pinocytosis- liquids
Exocytosis:
Forces material out of cell in bulk
• membrane surrounding the material
fuses with cell membrane
• Cell changes shape – requires
energy
• ex: Hormones or wastes released
from cell
Endocytosis &
Exocytosis
animations
Effects of Osmosis on Life
Osmosis- diffusion of water through a selectively permeable
membrane
•
Hypotonic Solution
Osmosis
Animations for
isotonic, hypertonic,
and hypotonic
solutions
Hypotonic: The solution has a lower concentration of
solutes and a higher concentration of water than
inside the cell. (Low solute; High water)
Result: Water moves from the solution to inside the cell
Cell Swells and bursts open = cytolysis
Hypertonic Solution
•
Osmosis
Animations for
isotonic, hypertonic,
and hypotonic
solutions
Hypertonic: The solution has a higher concentration
of solutes and a lower concentration of water than
inside the cell. (High solute; Low water)
shrinks
Result: Water moves from inside the cell into the solution:
Cell shrinks =Plasmolysis
•
Isotonic Solution
Osmosis
Animations for
isotonic, hypertonic,
and hypotonic
solutions
Isotonic: The concentration of solutes in the solution
is equal to the concentration of solutes inside the cell.
Result: Water moves equally in both directions and the cell remains
same size= Dynamic Equilibrium
What type of solution are these cells in?
A
B
C
Hypertonic
Isotonic
Hypotonic