Cell membrane and Transport
Jan 13, 2016
Cell membrane and Transport
Cell membrane = plasma membrane• is semi-permeable or selectively permeable
because it controls what enters and exits the cell
Cell membrane is selectively permeable
Small molecules such
as water and non-charged
molecules can easily pass through the
phospholipid bilayer of the membrane
The cell membrane is described as a Mosaic Fluid Model
1) Mosaic = the membrane is made up of many different types of molecules.• A double layer of phospholipids make up the bulk of the membrane.• Proteins are used for transport of things in and out of the cell.• Carbohydrates are used for cell to cell communication (talking).• Cholesterol is used to keep the membrane stable.
2) Fluid = the different parts of the membrane are free to move around in the membrane. For example, the proteins will move from one spot to another in the membrane.
Structure Properties
Phosphate group
Hydrophilic = water loving
Fatty acid tail Hydrophobic= water hating
Phospholipids molecules of Cell membrane
https://www.youtube.com/watch?v=LKN5sq5dtW4
Overview of Passive & Active Transport
Cell Transport
PassiveTransport
Diffusion OsmosisFacilitated Diffusion
ActiveTransport
Carrier Proteins
Endocytosis Exocytosis
• no cell energy needed• molecules move with the
concentration gradient (high to low) due to random molecular motion
• cell energy needed• molecules move against the
concentration gradient (low to high)
molecules enter or leave one at a time
many molecules enter or leave together i.e. bulk transport
The Cell MembraneThere are two important parts of the cell membrane that should be mentioned when talking about transport.
1. phospholipids2. proteins
1.2.
Diffusion Demo
2. Smelly balloons
1. Predict what is going to happen next when the bag of iodine is placed in the starch solution?
Types of Passive Transport
There are three types of passive transport:
1.Diffusion2.Osmosis3.Facilitated Diffusion
Passive Transport1. Diffusion:• even spreading of molecules
from an area of high concentration to an area of lower concentration
• move with the concentration gradient
2. Osmosis:• diffusion of water molecules
across a selectively permeable membrane
• move with the concentration gradient
3. Facilitated Diffusion
a) molecule bounces into a specific carrier protein
b) carrier protein binds molecule
d) carrier protein resumes its shape
• used for molecules that are too big to pass directly
through cell membrane or protein channelhigh concentration outside cell
lower concentration inside cell
c) carrier changes shape & flips over, bringing molecule into cell
Passive Transport – How do molecules get inside the cell?
1. directly through phospholipid bilayerex. • O2
• CO2 • H2O• diffusion
and osmosis
2. protein channels• charged ions & water• ex. Na+, Ca2+, K+, Cl-
• diffusion and osmosis
3.carrier protein • facilitated diffusion• larger molecules• ex. glucose, amino acids
higher concentration outside of the cell
1 2 3
Lesson Recap
https://www.youtube.com/watch?v=svAAiKsJa-Y
Good interactive quiz:http://imc02.hccs.edu/BiologyLabs/GB1/04Diffusion/04DiffusionImages/DiffusionOsmosis_Quiz/index.html
Diffusion Demo
Predict in which beaker will diffusion of dye occurs faster?