Download Sometimes a cell must force molecules in or out of the cell, and use

3.2.1.1a and 3.2.1.2a
Transport Within Cells
Everything that moves into or out of a cell must go through the cell membrane. The cell
membrane is made of two layers of lipid molecules with proteins embedded. If the molecules
are small and nonpolar, they may be able to move between the lipid molecules to enter or leave
the cell. When molecules move from an area of higher concentration to an area of lower
concentration across the membrane, it is called diffusion. It occurs without the cell spending any
energy. When water diffuses through the cell membrane, it is called osmosis.
Some molecules can diffuse through membrane proteins. These molecules are too large
to move between the lipid molecules, but can move through special channels inside the
membrane protein. This is called facilitated diffusion.
Diffusion, osmosis, and facilitated diffusion all require no energy from the cell.
Together, they are referred to as passive transport.
Sometimes a cell must force molecules in or out of the cell, and use
energy to do it. When a cell uses energy to move something across its
membrane, it is called active transport. Some membrane proteins are
built to help move molecules from a low concentration toward a high
concentration. These proteins are called carrier proteins. Molecules bind
to them. Then ATP molecules bind to them. The ATP is used to change the
shape of the protein so that the molecule is moved through to the other
side.
Sometimes a cell must use vessicles to move a great number of molecules across the
membrane at once. The processes called endocytosis and exocytosis both use vessicles to
transport molecules in great quantities. Endocytosis occurs when the cell membrane is wrapped
around some large particle outside of the cell. For example, an amoeba obtains food by
endocytosis. Exocytosis occurs when a vessicle fuses with the cell membrane. The vessicles
contents are dumped to the outside of the cell as the vessicle membrane becomes fused with the
cell membrane. Vessicles that are used in exocytosis might contain wastes. They might also
contain a substance, like adrenalin, that is used outside of the cell.
Matching
_____1. diffusion
a. the movement of substances out of a cell using vessicles
_____ 2. osmosis
b. movement of substances across the cell membrane
using energy
_____ 3. facilitated diffusion c. the movement of a substance from an area of high
concentration to an area of low concentration
_____ 4. passive transport d. the movement of substances into a cell using vessicles
_____ 5. active transport
e. diffusion of molecules through special protein channels
_____ 6. carrier proteins
f. the diffusion of water
_____ 7. endocytosis
g. the movement of substances into or out of a cell without
using energy
_____ 8. exocytosis
h. proteins that move molecules from an area of low
concentration to an area of high concentration
True or False
_____ 1. Everything that moves into or out of a cell must go through the cell membrane.
_____ 2. Molecules cannot move between the lipid molecules in a cell membrane.
_____ 3. Small, nonpolar molecules can move between the lipid molecules in a cell
membrane.
_____ 4. A cell membrane is made of three layers of lipid molecules with proteins
embedded.
_____ 5. A cell membrane is made of two layers of lipid molecules with proteins
embedded.
_____ 6. Diffusion occurs when molecules move from an area of high concentration to
an area of low concentration.
_____ 7. Diffusion occurs when molecules move from an area of low concentration to
an area of high concentration.
_____ 8. Diffusion occurs only when the cell uses energy.
_____ 9. Diffusion occurs without the cell using energy.
_____ 10. Osmosis is the diffusion of water.
Fill in the Blank - One word may be used twice.
passive transport
high concentration
facilitated diffusion
proteins
diffusion
low concentration
large
osmosis
lipids
small
1. A cell membrane is made of two layers of ______________ with _______________
embedded.
2. If molecules are _____________ and nonpolar, they may be able to move between the lipid
molecules.
3. If molecules are ________________ , they may be able to move through ____________ in
the cell membrane. This process is called ______________________.
4. _____________________ is the movement of molecules from an area of
_______________________________ to an area of ___________________________.
5. _____________________ is the diffusion of water through a cell membrane.
6. Diffusion, osmosis, and facilitated diffusion are called ________________________
because none of these processes requires energy.
True or False
_____ 1. Passive transport occurs when a cell uses energy to move something across its
membrane.
_____ 2. Active transport occurs when a cell uses energy to move something across its
membrane.
_____ 3. Carrier proteins move molecules from an area of high concentration to an area
concentration.
_____ 4. Carrier proteins move molecules from an area of low concentration to an area
concentration.
_____ 5. Endocytosis uses vessicles to help move many molecules at once from the
of a cell to the outside.
_____ 6. Endocytosis uses vessicles to help move many molecules at once from the
of a cell to the inside.
_____ 7. Exocytosis uses vessicles to help move many molecules at once from the
of a cell to the outside.
_____ 8. Exocytosis uses vessicles to help move many molecules at once from the
of a cell to the inside.
____ 9. Endocytosis may be used to remove wastes from a cell.
____ 10. Exocytosis may be used to remove wastes from a cell.
____ 11. An amoeba uses endocytosis to obtain food.
____ 12. An amoeba uses exocytosis to obtain food.
of low
of high
inside
outside
inside
outside
Fill in the Blank
endocytosis
active
low concentration
exocytosis
carrier proteins
energy
vessicles
high concentration
adrenalin
1. Sometimes a cell must expend ___________ to move molecules in or out of a cell. .
2. In the cell membrane, _____________________ will change shape when they bind to specific
molecules and to ATP.
3. This is an example of __________ transport.
4. Endocytosis and exocytosis are forms of transport that require ________________.
5. ____________________ occurs when a vessicle fuses with the cell membrane and dumps its
contents outside of a cell.
6. ______________________ is an example of a substance that is released by exocytosis.
7. ______________________ occurs when a cell membrane encloses a substance outside of the
cell and then brings the substance into the cell in the form of a vessicle.
8. A cell must expend energy when it must move substances from a
_________________________ to a ___________________________.
Answer the Following
1. Describe the composition of a cell membrane.
2. What is diffusion?
3. What is osmosis?
4. What is facilitated diffusion?
5. What is the difference between passive transport and active transport?
6. What is a carrier molecule?
7. What is endocytosis?
8. What is exocytosis?