Cell Processes Lecture 1

Question 1

Fluid mosaic model:

Answer 1

“Sea of lipids in which proteins float like icebergs

Question 2

Membrane is held together by _____

Answer 2

hydrogen bonds

Question 3

The lipid is a ____

Answer 3

barrier to entry or exit of polar substances

Question 4

Lipid bilayer:

Answer 4

Proteins are inserted into different areas of the bilayer. Two back to back layers of 3 types of lipids molecules. Cholesterol and glycolipids scattered among a double row of phospholipid molecules.

Question 5

Phospholipids polarity:

Answer 5

Amphipathic

Question 6

Lipids flip flop:

Answer 6

Rarely between membrane leaflets therefore the lipid composition of the leaflets can be asymmetric.

Question 7

Fluidity is determined by:

Answer 7

• Lipid tail length (the longer the tail, the less fluid)
• Number of double bonds - more double bond increases fluidity

Amount of cholesterol - more decreases fluidity

Question 8

Membrane proteins: (2 types)

Answer 8

Integral proteins: extend into or completely across cell membrane (transmembrane protein)

-Peripheral proteins: attached to either inner or outer surface of cell membrane.

Question 9

Integral membrane proteins x3:

Answer 9

-Amphipathic

Question 10

Functions of membrane proteins:

Answer 10

• Receptor proteins
• Cell identity markers
• Linkers
• Enzymes
• Ion channels
• Transporter proteins

Question 11

Channels:

Answer 11

-Allows specific substance move through water filled pore. Most plasma membranes include specific channels for several common ions.

Question 12

Transporters:

Answer 12

Transports specific substances across membrane by changing shape.

Question 13

Selectivity permeability:

Answer 13

Permeable to nonpolar, uncharged molecules.

Permeable to small uncharged polar