2a- Cell membrane structure

Question 1

Gateway to the Cell
* Acts as a boundary
* Controls what enters and leaves cell
* Regulates chemical composition
* Maintains homeostasis

Answer 1

Cell membrane

Question 2

The cell membrane
is ____ and allows a
____ ____ to
move

Answer 2

• flexible
• unicellular organism

Question 3

Biological membranes consist of

Answer 3

Lipid bilayers

Question 4

Plasma membrane models

Answer 4

• Sandwich model
• Unit membrane
• Fluid Mosaic Model

Question 5

Proposed sandwich model

Answer 5

Danielli + Davson

Question 6

2 layers of globular proteins with phospholipid inside to make a layer and then join 2 layers together to make a channel for molecules to pass

Answer 6

Sandwich model

Question 7

Outer layer of protein with phospholipid bilayer inside, -believed all cells same composition

Answer 7

Unit membrane model

Question 8

Phospholipid bilayer with proteins partially or fully imbedded, electron micrographs of freeze fractured membran

Answer 8

Fluid Mosaic Model

Question 9

The lipids in a membrane are organized into a
___ ___ ___

Answer 9

liquid crystalline lattice

Question 10

The lattice becomes a ____ ____ gel at the transition temperature

Answer 10

frozen crystalline

Question 11

Importance of two layers of lipids in plasma membrane?

Answer 11

at least a portion of
the membrane repels the water that constantly surrounds it. Too much water could burst the cell

Question 12

plasma membrane has consistency of olive oil at body temperature, due to unsaturated phospholipids.

Answer 12

Fluid

Question 13

proteins form a collage that differs on either side of membrane and from cell to cell (greater than 50 types of proteins)

Answer 13

Mosaic

Question 14

Facing out

Answer 14

Hyrophilic portions

Question 15

facing in

Answer 15

Hydrophobic portions

Question 16

Low temperature

Answer 16

Gel phase, hydrocarbons are tightly packes

Question 17

moves to fluid phase

Answer 17

At high temp., bilayer ‘melts’, movement is allowed

Question 18

Types of phospholipids movement

Answer 18

1. Flip-flop
2. Lateral
3. Flexion
4. Rotation

Question 19

The proteins move laterally within the cell membrane

Answer 19

Lateral diffusion

Question 20

While the lipids can move both laterally and rotate 360 degrees

Answer 20

Flip-flop diffusion

Question 21

Cholesterol affects fluidity

Answer 21

Lessens fluidity (body temp)
Maintains fluidity (Colder temp)

Question 22

Classifications of membrane proteins

Answer 22

• Peripheral membrane proteins
• Integral membrane proteins
• Transmembrane proteins

Question 23

are proteins that dissociate from the membrane following treatments with polar reagents that do not disrupt the phospholipid bilayer.

Answer 23

Peripheral membrane proteins

Question 24

can be released only by
treatments that disrupt the phospholipid bilayer

Answer 24

Integral membrane proteins

Question 25

span the lipid bilayer with portions exposed on both sides of the membrane.

Answer 25

Transmembrane proteins

Question 26

Types of membrane proteins

Answer 26

• Transport proteins
• Receptor proteins
• Enzymatic proteins
• Cell recognition proteins
• Attachment proteins
• Intercellular junction proteins

Question 27

Types of transport proteins

Answer 27

• Channel proteins
• Carrier proteins

Question 28

channel for lipid insoluble molecules and ions to pass freely through

Answer 28

Channel proteins

Question 29

bind to a substance and
carry it across membrane, change
shape in process

Answer 29

Carrier proteins

Question 30

Bind to chemical messengers, which sends a message into the cell causing cellular reaction

Answer 30

Receptor proteins

Question 31

Carry out enzymatic reactions right at the membrane when a substrate binds to the active site

Answer 31

Enzymatic proteins

Question 32

Glycoproteins (and
glycolipids) on extracellular surface
serve as ID tags

Answer 32

Cell recognition proteins

Question 33

Attach to cytoskeleton and or extracellular matrix

Answer 33

Attachment proteins

Question 34

protein fibers and carbohydrates secreted by cells and fills the spaces between cells and supports cells in a tissue

Answer 34

Extracellular matrix

Question 35

connect to both

Answer 35

Integrins

Question 36

can influence activity inside the cell and coordinate the behavior of all the cells in a tissue

Answer 36

Extracellular matrix

Question 37

Bind cells together

Answer 37

Intercellular junction proteins

Question 38

Types of cell junctions

Answer 38

• Tight junctions
• Desmosomes
• Gap junctions

Question 39

Transmembrane Proteins of opposite cells attach in a tight zipper-like fashion
- No leakage

Answer 39

Tight junctions

Question 40

Example of tight junctions

Answer 40

• Intestine
• Kidneys
• Epithelium of skin

Question 41

Cytoplasmic plaques of two cells bind with the aid of intermediate filaments of keratin
* Allows for stretching

Answer 41

Desmosomes

Question 42

Example of Desmosomes

Answer 42

Stomach
Bladder
Heart

Question 43

• Channel proteins of opposite cells join together providing channels for ions, sugars, amino acids, and other small molecules to pass.
• Allows communication between cells

Answer 43

• Gap Junctions

Question 44

Can Establish the Rate of Membrane Component Movement

Answer 44

FRAP (Flourescence Recovery After Photobleaching

Question 45

is not found in plant
membranes

Answer 45

Cholesterol