Biological Membranes

Question 1

Cell Plasma Membrane

Answer 1

Semi-permeable phospholipid bilayer selectivity is mediated by channels and carriers (Water soluble). The membrane permits fat soluble compounds through

Question 2

Proteins & Signaling Areas in the Membrane

Answer 2

Embedded in the bilayer to act as cell receptors during signal transduction and maintain overall cellular activity

Question 3

Phospholipids

Answer 3

Move rapidly in the plane of the membrane through simple diffusion

Question 4

Lipid Rafts

Answer 4

• Primary component of cell membranes that provide structure
• Phosphate group serves as the attachment point for other water soluble biomolecules
• Secondary messenger in signal transduction

Question 5

Membrane Components

Answer 5

(Most plentiful)
- Lipids
- Proteins
- Carbohydrates
- Nucleic Acids
(Least plentiful)

Question 6

Unsaturated Fatty Acids

Answer 6

Impart fluidity to the membrane

Question 7

Glycerophospholipids

Answer 7

Used for membrane synthesis

Question 8

Cholesterol

Answer 8

• Imparts fluidity to the membrane
• Synthesizes steroids
• Provides stability by linking adjacent phospholipids and occupying the space between them

Question 9

Waxes

Answer 9

• Serve an extracellular function in protection and waterproofing
• Provide stability / rigidity within the nonpolar tail region of the membrane

Question 10

Transmembrane Proteins

Answer 10

Pass completely through the lipid bilayer

Question 11

Embedded Proteins

Answer 11

Interior (cytoplasmic) OR Exterior (Extracellular) proteins on the surface of a cell

Question 12

Peripheral Proteins

Answer 12

They are transporters, channels and receptors bound with the lipid bilayer, lipid rafts or other transmembrane and embedded proteins

Question 13

Carbohydrates

Answer 13

• Hydrophilic
• Attached at extracellular side
• Function in signaling and molecule recognition

Question 14

Receptors

Answer 14

(De)Activate transporters for facilitated diffusion or active transport

Question 15

Cell Adhesion Molecules (CAMs)

Answer 15

Cell-Cell junctions that allow cells to recognize each other and contribute to proper cell differentiation and development

Question 16

Gap Junctions

Answer 16

• Direct Cell-Cell communication

- Connexons permits water / solutes movement

Question 17

Tight Junctions

Answer 17

Prevent solutes from leaking into intracellular space via a paracellular route. They create a physical link between cells to form a waterproof seal

Question 18

Desmosomes

Answer 18

Bind adjacent cells by anchoring to their cytoskeleton

Question 19

Hemi-Desmosomes

Answer 19

Attach epithelial cells to underlying (basement membranes)

Question 20

Simple Diffusion

Answer 20

• Passively move from a High [ ] Gradient —> Low [ ] Gradient until equilibrium is achieved
• Does not require a transporter
• Substrates move directly across membrane

Ex: Small, nonpolar molecules like O2 and CO2

Question 21

Osmosis

Answer 21

• Moves from Low [ ] Gradient —> High [ ] Gradient
• Diffusion across a selectively permeable membrane
• Move H2O Only

Question 22

Hypotonic Solution

Answer 22

Lower concentration of solution outside the cell, [Solutes] increase in the cell, Resulting in a net flow of water into the cell (cell will swell, increase in size)

Question 23

Hypertonic Solution

Answer 23

Higher concentration of solution outside of the cell, [Solutes] decrease in the cell, Resulting in a net flow of water out of the cell (cell will shrink, decrease in size)

Question 24

Isotonic Solution

Answer 24

Equimolar [Solutes] inside and outside of the cell, resulting in no net flow of water

Question 25

Osmotic Pressure Equation

Answer 25

Osmotic Pressure - iMRT

i = Van't Hoff Factor (# of molecules that a compound dissociates into)
M = Molarity of solution
R = Ideal gas constant
T = Temperature

Question 26

Facilitated Diffusion

Answer 26

• Moves from High [ ] gradient —-> Low [ ] gradient
• Transport proteins facilitate movement
• Carriers will open 1 side of the membrane at a time
• Channels are exposed to both sides of the membrane when open

Question 27

Passive Transport

Answer 27

• Positive Entropy (S) - increases
• Negative Free Energy (G) - Spontaneous
• Does not require energy

Question 28

Active Transport

Answer 28

• Positive Free Energy (G) - Nonspontaneous

- Moves [ ] against the gradient

Question 29

Primary Active Transport

Answer 29

• Uses ATP Hydrolysis (or another energy molecule) to directly transport molecules across the membrane.
• May involve Transmembrane ATPase

Question 30

Secondary Active Transport

Answer 30

• One molecule moves down the [ ] gradient which releases energy to move a different molecule up it’s [ ] gradient

Question 31

Endocytosis

Answer 31

Cell membrane invaginates and engulfs material to bring into cell

Question 32

Pinocytosis

Answer 32

Fluids and dissolved particles are engulfed by the cell membrane and brought into the cell

Question 33

Phagocytosis

Answer 33

Large solids and bacteria are engulfed by the cell membrane

Question 34

Exocytosis

Answer 34

Secretory vesicles fuse with the membrane, releasing materials from the inside of the cell into the extracellular environment

Question 35

Na+ and K+ Pump

Answer 35

• 3 Na+ out and 2 K+ in
• Leak channels (more K+) allows ions to permeate through the cell membrane
• Both maintain a stable resting membrane potential

Question 36

Outer Membrane Mitochondria

Answer 36

• Highly permeable

- large pores move ions and small proteins

Question 37

Inner Membrane Mitochondria

Answer 37

• Contain Cristae (foldings)
• Restricted Permeability
• Encloses matrix

Question 38

Osmotic Pressure

Answer 38

• Colligative Property

- Pressure applies to a pure solvent to prevent osmosis, and is related to the [ ] of the solution

Question 39

Symport (Active Transport)

Answer 39

Transport mechanism that moves two compounds simultaneously across a cell membrane in the same direction, one compound being transported down a concentration gradient and the other against a gradient

Question 40

Antiport (Active Transport)

Answer 40

Cell membrane transport mechanism that transports two molecules at once through the membrane in opposite directions.

Question 41

Countertransport (Active Transport)

Answer 41

Simultaneous transport of two substances across a membrane in opposite directions, either by the same carrier or by different carriers that are biochemically linked to each other.