Download Section: 2.6 Name:

Section: 2.6
Name:
Question of the Day:
Latin Root Word:
Review of Old Information:
A cell cannot survive if it is totally isolated from its environment. All cells must take in nutrients and
other materials, and they must also dispose of the wastes they produce. Therefore, both nutrients and
wastes must pass through the cell membrane. From the information that was studied yesterday you
should be able to describe the structure, composition, and function of the cell membrane.
How is the cell membrane selectively permeable?
What are the major components of the cell membrane?
New Information: pg. 95-100
Notes:
The function of the cell membrane is to maintain ______________________ by
controlling what enters and leaves the cell. Substances can cross over the cell
membrane through two processes known as _____________________ and
_____________________ transport. Active transport requires ____________ to
moves substances in and out of the cell. However, today we will discuss passive
transport which allows substances to move across the cell membrane without any input
of ____________.
1.
2.
3.
The three types of passive transport that will be discussed today are:
Passive Transport– “no energy required” – moves with the gradient
Diffusion -­‐ the movement of molecules from high concentration to low concentration Diffusion through the Cell Membrane (Selectively Permeable) Cologne diffusing through a Room Small Particle diffusing over the Cell Membrane Outside of Cell Inside of Cell Inside of Cell Inside of Cell Inside of Cell Before After Before After High Concentration Low or Even Concentration High Concentration Low or Even Concentration Concentration Gradient – The difference in particle concentration across a space Equilibrium – the concentration is the same through space Facilitated Diffusion - The movement of large molecules with a concentration gradient using a carrier protein
3 Steps
-­‐ Step 1 – A particle binds to the carrier protein Questions: Does facilitated diffusion need energy? -­‐ Step 2 -­‐ The carrier protein changes shape Does it move with the concentration gradient? -­‐ Step 3 -­‐ The molecule is released on the other side PASSIVE TRANSPORT CONTINUED - “no energy required” – moves with the gradient
Diffusion Through Ion Channels Ion Channels – the movement of ions that cannot move across the lipid bilayer without assistance - Some ion channels are always open Questions: Do Ion Channels need energy? - Others have gates Does it move with the concentration gradient? -­‐ Move ions such as Na+, K+, Ca2+, Cl-­‐ 1. Toward what condition does diffusion eventually lead, in the absence of other influences?
2. What role do carrier proteins play in facilitated diffusion?
3. How is facilitated diffusion similar to diffusion through ion channels?
Activity:
Today you will be learning about another important type of passive transport. In this process, water
moves down the concentration gradient across your cell membranes. This in turn provides your cells with
the water they need to remain in homeostasis and survive. Use pages 96-99 in your textbook to help
answer the questions below:
The type of passive transport where water diffuses across the cell membrane is called _______________.
Water typically diffuses across the membrane towards the area where the solute is higher or lower
(circle one).
When the concentration of solute molecules is HIGHER inside the cell than outside, the situation is called
_______________. In this case, water diffuses into or out of the cell (circle one).
When the concentration of solute molecules is LOWER inside the cell than outside, the situation is called
_______________. In this case, water diffuses into or out of the cell (circle one).
When the concentration of solute molecules is equal inside and outside of the cell, the situation is called
_______________. In this case, water diffuses into and out of the cell at EQUAL rates.
Study the diagram below to help understand these processes better:
While some cells have an easy time keeping the water in balance, other types of organisms have a
much harder time adjusting. For example, unicellular organisms that live in freshwater are in a hypotonic
condition, where water freely moves into their cells. Therefore, these organisms must use a
____________________ ____________________ to pump excess water out of their bodies and
maintain homeostasis.
Osmosis can have many effects on different cells. For example, if plant roots are surrounded by
water and in a hypotonic condition, water will move into the plant root cells, creating _______________
pressure. If this pressure becomes to great, it can cause the cell to burst or explode, known as
_______________. On the other hand, if it were a time of drought and the plant root cells were instead
in a hypertonic condition (where water would move out of the cell), the cells will shrink or shrivel up
through a process known as _______________.