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?