3.3 bio

​III. Cell Membrane 3.3

​A. Forms boundary between cell and outside   environment.

B. Controls passage of materials into and out  of cell. Is selectively permeable (allows some things but not others) Helps to maintain the cells homeostasis

​C. Consists of double layer of phospholipids interspersed with other molecules (proteins and carbohydrates)

1. Phospholipid- molecule composed of 3   basic parts

a. phosphate and glycerol form “head”

b. fatty acid forms “tail”

Multiple Choice

What do receptors help transmit?

• Proteins

• Signals

• Ligands

• Glycerol

​ c. forms polar molecule (“head” hydrogen bonds to water molecules, and “tail” does not)

d. Double layered membrane had “heads” on outside and “tails” on inside.   

2. Forms double layer because of water on inside and outside of cell.

​E. Other molecules are embedded with the phospholipid layers

1. Cholesterol molecules strengthen cell membrane

2. Proteins extend through membrane and form channels

3. Carbohydrates attached to proteins act like “identification tags”

 4. Fluid Mosaic Model- describes arrangement of molecules in cell membrane.  Flexible “fluid like” lipid embedded with “mosaic” of other molecules

​F. Molecules cross membrane in several ways

1. Some methods of transport require energy and some do not.

2. Depends molecules size, polarity, and   concentration inside versus outside.

​G. Cell membrane contains receptors that help transmit signals across membrane

1. Made of proteins

 2. It detects a signal molecule and performs an action in response

​3. Receptors bind to molecules called ligands

a. When bind, they change shape

b. This changed shape affects how receptor   interacts with other molecules

​4. Two types of receptors

a. Intracellular receptors- (means “within” cell)-   can interact with DNA and start production of certain proteins

b. Membrane receptor- Molecules that cannot cross membrane can send message to inside of cell.Causes molecules inside cell to respond   

Multiple Select

What are the two types of receptors?

• Intracellular

• Membrane

• Extracellular

• Outercellular

Multiple Choice

Receptors bind to molecules called what?

• Receptors

• Phospholipids

• Ligands

• Cholesterol

Multiple Choice

How many types of receptors are there?

• 5

• 4

• 3

• 2