biology chapter 7
TRANSCRIPT
Chapter 7
Cellular Function and
StructureWasilla High School
Mrs. Ragsdale
2014 - 2015
Robert Hooke and
Anton van Leeuwenhoek
The first true microbiologists
Hooke and Leeuwenhoek were the first two scientists to use microscopes to view life
Occurred in the 1700’s
Called what they saw “animalcules”
Cell Theory
All living things are made of cells
Cells are the basic unit of structure and life
Cells can only come from cells that already exist. They
have to receive DNA and pass it on to their offspring.
How did cells become cells?
People used to believe in spontaneous
generation, the idea that life just came
into being all by itself.
While we now know that this isn't the
case, scientists still can't all agree on
exactly how the first cell came into
being
Prokaryotic Cells: Bacteria
First cells
Small
Have no nucleus to house DNA
No membrane bound organelles (we'll talk more about this later)
Organelles – little specialized structures (like the nucleus) that have a specific function
Eukaryotic Cells: Plants, animals and
other complex life forms
Much, MUCH larger than prokaryotic cells
More complex, evolved version of the cell
Contain membrane bound organelles
DNA housed inside the nucleus
What do all cells need?
Plasma Membrane
Also known as the phospholipid bilayer
Made up out of phospholipids
Hydrophilic heads (water loving)
Hydrophobic tails (water hating)
Let's draw it! (Refer to page 188 in your
notes)
Fluid Mosaic Model
The protein channels, enzyme binding sites and cell recognition sites are able
to move around the plasma membrane like life rafts on a sea
https://www.youtube.com/watch?v=Qqsf_UJcfBc
Selective Permeability
Selective means the ability to choose
Permeability means allowing things to pass
through
So…. Selective permeability means that the
plasma membrane can pick and choose what
passes through
Passive Transport
No energy is expended
Diffusion = particles naturally move from a high to low
concentration gradient until equilibrium is reached
You want the same amount of particles on both sides of the membrane
Facilitated Diffusion What happens if the particles that want to cross the
plasma membrane are just too large to make it?
Using channels or carrier proteins to cross the plasma
membrane
No energy is used
Osmosis: Diffusion of Water
Water naturally is drawn to wherever high levels of Na+ and other
ions are
Osmosis is the movement of water across a membrane towards
the high level of concentrated ions
Tonicity
Hypertonic solution = more solute present outside of the
cells than what is inside
Water is drawn out of the cell
The cell shrivels
Hypotonic = less solute present outside of the cells than
what is inside
Water is pulled into the cell
The cell bursts (lyses)
Isotonic = the same amount of solute is present inside and
outside the cell
Water is balanced
Tonicity
Active Transport
Requires energy input
Sodium/Potassium
Pumps = requires ATP
to function
Active Transport: Endocytosis and
Exocytosis
Transportation of large molecules
into and out of the cell
A small piece of the plasma
membrane pinches off and
becomes a carrier called a vesicle
The vesicle merges with the
plasma membrane and either
opens outside the cell (exocytosis)
or inside the cell (endocytosis)