Materials Move Across Cell*s Membranes
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Transcript Materials Move Across Cell*s Membranes
MATERIALS MOVE ACROSS
CELL’S MEMBRANES
Chapter 2.3C
Review
What is a cell membrane??
What is the purpose of a membrane?
What are membranes primarily made up of?
For the remainder of the powerpoint, copy words
highlighted in ORANGE!
Diffusion
Molecules spread out from where there are many to
where there are fewer
They keep spreading until
they are evenly distributed
Examples:
Smelling
a scent
Oxygen (needed for respiration) and carbon dioxide
(produced by respiration)
Concentration
The number of particles of that substance in a
specific volume
Example:
Dissolving
9 grams of sugar in 1 liter of water yields the
concentration 9g/L
Diffusion in Cells
Materials are able to move into and out of the cell
Example:
Photosynthesis:
produces oxygen inside the cell
Concentration of oxygen is higher on the inside than the outside
Oxygen cells move out of the cell by diffusion
**What are some daily examples of diffusion?
Types of Diffusion
Passive transport
Active transport
Osmosis
Endocytosis
Exocytosis
Passive Transport
Materials move without using the cell’s energy
(moving from high concentration to low
concentration)
Osmosis
Diffusion of water through a membrane
Example:
Unwatered plants wither
Water leaves the plant’s roots to go to the dry soil to even out the
concentration of water molecules
When the plant is watered,
water molecules
diffuse through
the plant’s cell
membranes to
even out the
concentration again
Active Transport
Process of using energy to move materials through a
membrane (moving from low concentration to high
concentration)
Examples:
Marine
Kidneys
iguanas
Endocytosis
Moving materials too large to pass through a
membrane INTO the cell
Membrane
folds inward, creating a pocket
Membrane closes around the material, forming a
“package”
“Package” breaks away from
cell membrane, bringing the
material into the cell
Exocytosis
Moving materials too large to pass through a
membrane OUT OF the cell
“Package”
carries materials to cell membrane
Attaches to membrane and merges together
Materials are pushed out of membrane
Cell Size (and shape) Affects Transport
As cell grows, surface area is not large enough to
allow resources to travel to all parts of cell
As a result, the cell may:
Stop
growing
Divide
Shape
Thin
and flat cells (single-celled organisms) have
increased surface area
Long and skinny cells (nerve and muscle) have
increased surface area