2.2 Membrane Structure and Functions

Question 1

The Fluid Mosaic Model

Answer 1

States the membranes are NOT rigid with molecules locked in place

Membranes contain lipid molecules (phospholipid bilayer) in which a wideassortment of proteins (“mosaic”) are
embedded

Membranes are “fluid”

Lipid and protein molecules are free to move
laterally within the two layers

Question 2

Glycolipid

Answer 2

A membrane lipid
attached to a
carbohydrate group

Question 3

Glycoprotein

Answer 3

A membrane protein
attached to a
carbohydrate

Both are involved in cell
recognition and cell-cell
interactions

Question 4

The Role of
Phospholipids/phopholipids make up…

Answer 4

Make of the majority of
the plasma membrane

Question 5

Phospholipids Contains

Answer 5

2 fatty acid tails
(hydrophobic, non-polar)

Glycerol group +
phosphate group + polar
alcohol (hydrophilic, polar)

Question 6

Phospholipids form a ________ when in an aqueous solution

Answer 6

Bilayer

Question 7

Membrane Fluidity is dependent on;

Answer 7

1. Composition of lipid molecules
   (i.e., saturated vs. unsaturated)
2. Temperature

Question 8

Sterols (commonly cholesterol)
found in animal cells (not plants
or prokaryotes) act as…

Answer 8

membrane stabilizers

Question 9

At high temperatures sterols…

Answer 9

stop lipid movement to hold
the membrane together

Question 10

At low temperatures, sterols…

Answer 10

occupy space between lipid
molecules preventing the
membrane from becoming too
rigid

Question 11

The Role of Membrane Proteins

Answer 11

Membrane proteins can be separated into 4 functional categories:
1. Transport
2. Enzymatic Activity
3. Triggering Signals
4. Attachment and Recognition

Question 12

1. Transport

Answer 12

Hydrophilic protein
channels embedded in the
phospholipid bilayer allows
for molecules to move from
outside to inside of the cell
and vice versa

Question 13

2. Enzymatic Activity

Answer 13

Some membrane proteins,
such as those associated with
respiration and
photosynthesis, are enzymes

Question 14

3. Triggering Signals

Answer 14

Membrane proteins may
bind to specific chemicals,
like hormones

This can cause changes within
the cell to occur

Question 15

4. Attachment and Recognition

Answer 15

Proteins exposed to both internal and external environment act as
attachment points for the cytoskeleton, as well as components involved in cell-cell
recognition

Ex. Surface proteins can
recognize disease-causing
microbes that try to invade
cells, triggering an immune
response

Question 16

Integral Membrane Proteins

Answer 16

Membrane proteins embedded in the phospholipid bilayer

Most are transmembrane proteins, spanning the
entire bilayer and have parts exposed to the internal
and external environment

Question 17

Peripheral Membrane Proteins are on the surface

Answer 17

On the surface of the phospholipid bilayer

Question 18

Peripheral membrane proteins do not interact with…

Answer 18

DO NOT interact with the hydrophobic core of the bilayer

Most are on the cytosol side (internal) and some are
part of the cytoskeleton

Question 19

Peripheral membrane proteins are held to the _______ by ________ ______

Answer 19

Held to the bilayer via (hydrogen and ionic bonds)