Transcript Cell Movement How Does Stuff Get Into and Out of the Cell.

Cell Movement
How Does Stuff Get Into and Out of the Cell
Major Factor Cell Membranes
1.All cells have a cell membrane
2.Functions:
a. Controls what enters and exits
the cell to maintain an internal
balance called homeostasis
b.Provides protection and support
for the cell
About Cell Membranes
• Cell membranes have pores (holes) in it
a. Selectively permeable: Allows some molecules in and
keeps other molecules out
b.The structure helps it be selective!
Pores
Define selectively permeable membrane
• A membrane that allows only certain materials to
cross it
• Materials pass through pores in the membrane
– Small molecules pass through – ex: water
– Large molecules can’t pass through – ex: proteins
and complex carbohydrates
KEY CONCEPT… Materials move across
membranes because of concentration
differences.
HIGH to LOW
NO ENERGY
Energy NOT REQUIRED for particles to
move from areas of HIGH
concentration to areas of LOW
concentration. (Passive Transport)
Energy REQUIRED for particles to
move from areas of LOW
concentration to HIGH concentration.
(Active Transport)
LOW to HIGH
ENERGY
Types of Cellular Transport
•
Passive Transport
- cell does not use energy
1. Diffusion (of small particles)
2. Osmosis
Weeee!
!!
high
low
•
Active Transport
- cell does use energy
1. Endocytosis
2. Exocytosis
high
This is
gonna
be hard
work!!
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)
Passive Transport:
1. Diffusion
1. Diffusion: random movement of particles from an
area of high concentration to an area of low
concentration.
(High to Low)
•
Diffusion continues until all molecules are evenly
spaced (equilibrium is reached)-
•
Note: molecules will still move around but stay
spread out.
Diffusion
•
The movement of molecules from a area in which they are highly
concentrated to a area in which they are less concentrated.
• Occurs without control or energy use
• Affected by:
• Size of molecules
• Size of pores in a membrane
• Temperature
Passive Transport:
2. Osmosis
Osmosis
animation
• 2. Osmosis:
– diffusion of water through
a selectively permeable
membrane.
– Water moves from high to
low concentrations
•Water moves freely
through pores.
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
•(Low  High)
Endocytosis
• Very large molecules or substances must enter the
cell by the membrane pinching inward:
Types of Active Transport
Endocytosis
•
1. 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!
Endocytosis in action…..
Exocytosis
• The cell gets rid of secretions or wastes
Types of Active Transport
2. 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
Why are osmosis & diffusion
important?
Why are osmosis & diffusion important?
• All living things have certain requirements they must satisfy
in order to remain alive – maintain homeostasis
• These include exchanging gases (usually CO2 and O2),
taking in water, minerals, and food, and eliminating wastes.
• These tasks happen at the cellular level.
• Molecules move through the cell membrane by diffusion.