The Cell in Its Environment
A Selective Barrier
In what way is the cell membrane like a gatekeeper?
How Do Materials Move Into
and Out of Cells?
To live and function cells must let certain
materials into and out of the cell
Cell membrane consists of a double layer of
lipid molecules lined up side by side
Selectively permeable – some substances can
move across the membrane and others cannot
Passive Transport
The movement of dissolved materials across a
cell membrane without using the cells energy
Diffusion
A drop of food coloring in a plate of gelatin gradually spreads as molecules
of the dye diffuse. How would the third plate look if diffusion continues?
Diffusion
High concentration
Low concentration
Equilibrium
Osmosis
Facilitated Diffusion
Blocks and shapes color coded example
Sugars do not cross easily through the
membranes lipid molecules, so proteins in the
cell membrane form channels through which the
sugars can pass
Active Transport
The movement of materials across a cell
membrane using energy
Low concentration to high concentration
Crossing the
Cell Membrane
Molecules move into and out of
a cell by means of passive or active transport. Complete the boxes, and describe where
the concentration of each substance is high or low.
Large Cell and Small Cell
How does the difference in the size of cells affect their processes?
Moving Large Particles
Endocytosis – sometimes the particle the cell
needs ingest are too large to cross the cell
membrane, the cell membrane then changes
shape and engulfs the particle.
Exocytosis – allows large particles to leave the
cell
Water Molecule
Imagine that the yellow line is the cell membrane. What is the overall
direction in which water will travel as a result of osmosis?