Download The basic unit of life

The Cell
The basic unit of life
Cell Theory: states the following
3 things
1) all living things are
cellular
2) cells are the smallest
functioning unit in all
living things and
3) cells come from preexisting cells
Cell Theory: states the following
3 things
Think – Pair - Share
• Is it called a theory
because we are still not
sure?
• Has this been “Proven”?
• Will it become a law
when it is “proven”?
This knowledge came out of the
following work:
• Hans Janssen- 1590, 1st compound microscope
• Robert Hooke -1665, First to use the word “cell”, could
only see cell wall of cork.
• Anton van Leeuwenhoek- 1680, First to observe living
cells (teeth scrapings). He called them “animalcules”.
• Matthias Schleiden-1838, First to observe that plants
are made of cells
• Theodor Schwann-1839, First to put concept that all
living things are cellular
• Rudolph Virchow-1855, Discovered that cells come
from other cells, discredited “spontaneous generation”
(Redi too!)
What’s the fuss?
• People thought that life spontaneously
generated if the substances of life were
present. Not a miraculous process!
2 main types of cells
Prokaryotes
Eukaryotes
Break Down the Words
Karyo = NUCLEUS
What could the pre-fixes mean??
Talk to a partner and see if you can guess
Pro = Before
Eu = True
2 main types of cells
Prokaryotes
Eukaryotes
No Nucleus or other
membrane-bound
organelles
Smaller in overall size
Contains a nucleus and
other membrane-bound
organelles
Larger in overall size
Cell wall (when present)
contains pepidoglycon,
complex
Cell wall when present
contains cellulose, simpler
Circular DNA
Helical, linear, double
stranded DNA
EX:Bacteria
Ex: Human cells, plant cells
The prokaryote
Fimbriae
Cillia
Location of
DNA/RNA
Cellular movement
• 3 ways cells move (if they can)
Cilia- hair-like projections
Flagella- whip-like projections
Pseudopod-false foot, like the
blob!
The 2 energy organelles
Comparing plant and animal cells
Cell Wall
Plastids
Shape
Vacuoles
Centrioles
Division
Plant
Animal
Present
Absent
Present
Absent
Generally more
Generally more
rectangular due to spherical due to
ridgid cell wall
lack of cell wall
One large
Absent
Build Cell Plate
Many small
Present
Lack cell plate
The Cell Membrane
Cell membranes are
composed of two
phospholipid layers.
(bilayer)
The cell membrane has
two major functions.
1. Forms a
boundary
between inside
and outside of
the cell
2. controls
passage of
materials
Present in all cells
•Phospholipid is a specialized lipid (fat) that
has one of it’s fatty acid tails removed so a
phosphate can be added.
•This causes a normal lipid that is ALWAYS
hydrophobic, to become partially
hydrophilic.
•Terms that describe this are;
hydrophilic/polar, hydrophobic/non-polar
•Why do we want to have modified lipids
(fats) in the cell membrane?
Properties of the membrane
The fluid mosaic model describes the
membrane.
With a partner, define the two words and discuss how
this might relate to the cell membrane:
FLUID – bendable, movable, not solid
MOSAIC – made up of many pieces
The fluid mosaic model describes the membrane.
There are other molecules embedded in the
membrane – this makes the surface bumpy
cell membrane
carbohydrate
chain
protein
cholesterol
protein
protein channel
5 specialized proteins
•
•
•
•
•
•
Adhesion
Communication (cell to cell)
Receptor
Pull out your fold, I
Recognition
will call randomly to
Passive Transport share what each of
Active Transport the protein do!
The cell membrane is selectively permeable.
Some molecules can cross the
membrane while others cannot.
• Chemical signals are
transmitted across the
cell membrane.
– Receptors bind with
ligands and change
shape.
– A ligand is a specific
molecule that binds with
a receptor to make
something happen.
There are two types of receptors.
1) intracellular receptor
• Ligand moves through the
cell membrane to reach
receptor on inside of cell.
• Example: hormones
2)membrane receptor
• Ligand on outside of cell
binds with a receptor within
the cell membrane.
• Ex: Neurotransmitters,
growth factors
Basic movement across cell membrane:
Materials move across the membrane in a variety of ways:
• Passively: (no energy required) moved based on
concentration gradient.
• Actively: moving items against a concentration gradient,
energy is required
• Facilitated diffusion: No energy, just using helpers (like
proteins) to move things in or out of a cell that are large.
• The two most common passive movement processes are
diffusion (solutions) and osmosis (water)
• Solutions are substances (solutes) dissolved in a solvent
(water) to form a solution.
Example
Think – Pair - Share
Solutions are solutes dissolved in
a solvent to form a liquid.
Think about Kool-Aid:
• What are the solutes?
• What’s the solvent?
• What’s the end solution?
Diffusion
• No solute likes to be crowded. Therefore, they will move from
area that is very saturated (crowded) to one that is not so
saturated (uncrowded). This process of widely spreading out is
called diffusion.
• Who has been in a room where someone sprays perfume?
Does it stay in just one area?
• NO!! The perfume is moving from high concentration to low
concentration
• Diffusion takes no energy, so it is passive.
• Osmosis is the passive movement of water.
Let’s Practice: Which way would the
solute move?
Think about it…
• How do you think these processes
could speed up or slow down?
Terms to describe solutions
Hypo=less than
Hyper=more than
Tonic =solution
Osmotic = Water
Iso = equal
Try these:
more solution (higher concentration of solute)
less solution (lower concentration of solute)
Equal amounts of solute
So if there is more solute then what does that say about the
amount of water?
Now try these:
More solute = less water = ?
Less solute = more water = ?
Which way would the water move?
• In osmosis water will move from high WATER
concentration to low WATER concentration.
REMEMBER, YOU ARE COMPARING 2
ENVIRONMENTS! INSIDE (intracellular) AND
OUTSIDE THE CELL (extra-cellular)
Effects of water movement:
• If a cell loses to much water it will shrink and die! That’s called
crenate or plasmolyze.
• If a cell gains to much water it will burst and die! This is called
cytolysis. (lysis for short)
• Both are bad!
• Cells try to maintain homeostasis when it comes to water and
solutes and solutions. Homeostasis means a stable internal
environment. (Biological balance)
Think of 2 other ways that cells
can maintain homeostasis.
Active Transport
• But what happens if we want solutes to go from an area of
low concentration to high concentration?
• Must use ENERGY!
• It’s like putting the smell back in the can! (Active transportgoing from low concentration to highly concentrated)
Movement by vesicle
What is a vesicle?
•
•
•
•
Endocytosis: Moving things into the cell using a vesicle
Exocytosis: Moving things out of the cell using a vesicle
Pinocytosis: Bringing in of or removing liquids
Phagocytosis: Bringing in or removing of solids or large
particles.
These are not exclusive! You can combine
them to describe the type of movement!!
Exocytosis in paramecium