Download Cell Membrane and Transport

Transport
Aim: How are molecules transported into
and out of a cell?
I. Why is transport important?
A. Transport - the process by which substances
move into or out of cells or are distributed
within cells.
B. Provides:
1. Circulation: movement of materials throughout
an organism.
2. Absorption: the passage of material across a cell
membrane into a cell.
a. Process by which usable materials are taken into
an organism.
II. Cell Membrane
A. Selectively (semi) permeable
1. Only lets certain things into and out of cell.
2. CAN PASS THROUGH: water, glucose, amino
acids, carbon dioxide, fatty acids, glycerol.
3. CANNOT PASS THROUGH: starch, protein,
lipids.
III. Structure of the Cell Membrane
A. Composed of proteins, lipids and carbohydrates.
B. Made up of a bi-layer (2 layers) of lipids (fats).
C. Proteins run between lipid bi-layer on the inside of
cell and outside of cell.
D. “Fluid Mosaic Model”
1. Represents the various molecules attached
together in the cell membrane.
2. Mosaic: pieces or parts; different pieces put
together to make a final product.
3. Fluid: move freely; moving all the time.
Cross Section of a Cell Membrane
IV. Movement of Materials
A. Passive and Active Transport
1. Passive Transport: transport that does not require
energy from the cell. Materials can pass right
through.
a. Diffusion: the movement of molecules or particles
from an area of high concentration to an area
of low
concentration.
High
Just sit back
and enjoy!
Hill
Low
a. Diffusion Continued….
i. Concentration gradient: difference between
high and low concentration *must be present in
order for diffusion to occur.
ii. Molecules become evenly distributed throughout
available space.
1. Passive Transport – continued…
B. Osmosis: Diffusion of water molecules.
i. High concentration of water molecules to low
concentration of water molecules.
ii.Water molecules are highest in pure (distilled)
water.
iii. As water enters a cell, pressure will cause the cell
to expand = osmotic pressure.
iv. Isotonic solution: concentration of water molecules
is the same inside and outside of cell.
(a) No movement, concentration gradient is zero.
C. Osmosis Continued…
v. Hypertonic solution: more water molecules inside the
cell causing the cell to shrink.
(a) Movement of water out of cell.
(b) Animal cell shrinks.
(c) Plant cell vacuole collapse and cytoplasm shrinks.
**Plasmolysis: shrinking of the cytoplasm
vi. Hypotonic solution: less water molecules inside the
cell causing the cell to expand.
(a) Movement of water is into the cell.
(b) Animal cell bursts.
(c) Excessive water causes RBC’s to lyse (break).
(d) Plant cell collects water in the vacuole.
Plant Cell
Hypotonic Solution Hypertonic Solution
Isotonic
Hypertonic
2. Active Transport
A. When movement of molecules or particles across a cell
membrane requires cellular energy.
B. Usually involves movement of materials against the
concentration gradient. Going from low to high
concentration.
High
Hill
Low
“Oh no, look at
that hill! Its
going to take a
lot of energy to
get up it!”
2. Active Transport - continued
C. Use of transport proteins.
D. Membrane vesicles: materials become enclosed within an
inpocketing of the cell membrane.
1. Endocytosis: transporting materials into a cell by
vesicles.
a. Phagocytosis: solid particles are ingested into the cell.
b. Pinocytosis: small amounts of liquid are taken into the
cell.
Phagocytosis
Pinocytosis
V. Transport in Organisms
A. Simple Organisms: cells are in close contact
with outside environment.
B. Large or Complex organisms: need a
circulatory system.
C. Circulatory system: system that links the cells
of a complex organisms with its environment.
VI. Circulatory System
Made up of 3 parts:
A. A fluid in which materials are transported.
Ex. Blood
B. A network of tubes or body spaces through which
fluid flows.
Ex. Arteries, Veins, & Capillaries
C. A means of driving the fluid through the tubes or
spaces.
Ex. Pumping Heart