CELL MEMBRANE

Structure Fits Function(applied to the cell membrane)

The way the cell membrane is shaped and the parts it has

allows it to do its job.

Phospholipidmain molecule of the cell membrane

“likes” water (hydrophilic)(is attracted to water molecules)

doesn’t “like” water (hydrophobic)(repels water molecules)

How would many of these arrange themselves to be the cell membrane (considering there is water inside the cell AND outside the cell)?

Phospholipidmain molecule of the cell membrane

Does your model look like this?

Phospholipid Bilayer thin membrane made of two layers of lipid molecules

The cell membrane must be a good barrier

between the watery environment

inside the cell and the

watery environment outside the cell.

1

What TWO qualities make the membrane a good barrier?

1.Form a film of bubble solution on your straw device. Bend and fold the straws. What quality of the soapy membrane are you observing?

2. Float a small rubber band on the bubble film. Then pop the film inside the circle. Now gently remove the rubber band. What happens?

TWO qualities the cell membrane has…

1a. Flexible

1b.Self sealing

Would you describe the soapy membrane as

strong?The membrane needs to be strong in order to be a

good barrier.

Cholesterol Moleculesprovide strength and prevent freezing

The cell membrane must let substances in and out

2

Set-up and observe.

1. Fill the bag with starch solution. 2. Tie off the end tightly.3. Wash the outside of the bag. 4. Put the bag in a beaker of iodine.

What happened?

What can we infer about the cell membrane from this?

Which of these photos is most like the cell membrane?

Selective Permeabilityproperty that allows some substances to pass through more easily than others (based on size and charge)

The cell membrane must let substances in and out

2

WHAT GOES IN? WHAT COMES OUT?

How do larger substances get across?

Transport ProteinMoves larger or charged molecules across the membrane

The cell membrane receives signals

3

Receptor ProteinReceives signals from hormones or neurotransmitters

They receive signals based on shape.

What are “signals” in the body?HORMONES

chemical substances that act like messenger molecules throughout the

body (brain, blood, etc.)

NEUROTRANSMITTERSchemical substance, that transmits nerve signals across a nerve cell. Are found in

the brain and the nervous system. INSULIN – (pancreas cells have insulin receptor proteins on them which then allows sugar to enter the cells)

TESTOSTERONE – (male reproductive organs have receptor proteins on their cells which allows puberty to occur along with growth and strength of muscles)

ESTROGEN – (female reproductive organs have receptor proteins on their cells which allows puberty to occur)

DOPAMINE - is responsible for motivation, interest, and drive. It is associated with positive stress states such as being in love, exercising & listening to music.

SEROTONIN is key to our feelings of happiness and very important for our emotions because it helps defend against both anxiety and depression.

The cell membrane identifies the cell

4

CARDIAC MUSCLE CELL

Marker ProteinAct like name tags for a cell

Blood Type – ex of Marker Proteins

KarlLandsteiner

1901

Result = safe blood transfusions

AgglutinationClumping of red blood cells > crack and release toxins

Blood TypeWhat are the four main blood types?

Caucasians African American

Hispanic Asian

O + 37% 47% 53% 39%O - 8% 4% 4% 1%A + 33% 24% 29% 27%A - 7% 2% 2% 0.5%B + 9% 18% 9% 25%B - 2% 1% 1% 0.4%

AB + 3% 4% 2% 7%AB - 1% 0.3% 0.2% 0.1%

BLOOD GROUPS IN THE WORLD

Blood type O: the AmericasMost common blood type in populations around the world, including the USA and Western Europe. Among indigenous populations of Central and South America, the frequency of O blood type is extremely high, approaching 100%. It is also high among Australian aborigines.

Blood Type A: Central and Eastern EuropeType A is common in Central and Eastern Europe. In countries such as Austria, Denmark, Norway, and Switzerland, about 45-50% of the population have this blood type, whereas about 40% of Poles and Ukrainians do so. The highest frequencies are found in small, unrelated populations. For example, about 80% of the Blackfoot Indians of Montana have blood type A.

Blood type B: AsiaBlood type B is relatively common in Chinese and Indians, being present in up to 25% of the population. It is less common in European countries and Americans of European origin, being found in about 10% of these populations.

Blood type AB is the least commonIt is the rarest of the blood groups. It is most common in Japan, regions of China, and in Koreans, being present in about 10% of these populations.

Antigenany substance to which the immune system can respond

What do you notice about these antigens?

RBC Antigens- marker proteins on the RBC

AntibodyProtein used by the immune system to identify and destroy foreign objects

ANTIGENS AND ANTIBODIES

FIT TOGETHER LIKE A LOCK AND KEY

RBC Antibodies- proteins in our blood plasma (NOT on the RBC)

AgglutinationWhy it happens…

Antigens and Antibodiesin the Immune System

DiscoveryS. Singer and G. Nicolson in 1972

FLUID MOSAIC MODEL

Define in 3 phrases:

1. 2. 3.

FLUID MOSAIC MODELA model of the cell membrane that

describes it as made of little parts that are flexible & constantly moving.

1. 2. 3.

FLUID MOSAIC MODEL

Transport protein

Marker proteins

Markerprotein

Receptor protein

Watch this video of the cell membrane in action.

http://www.youtube.com/watch?v=Qqsf_UJcfBc