Semester 1 Final: Membrane Structure and Function

Question 1

Plasma Membrane

Answer 1

• selectively permeable
• composed of phospholipid bilayer (hydrophobic regions (tails) facing each other and hydrophilic regions (head) facing the exterior)

Question 2

Cholesterol

Answer 2

embedded in phospholipid bilayer - resists changes in membrane fluidity

Question 3

glycolipids & glycoproteins

Answer 3

carbohydrate attached to protein or lipid on the surface of membrane that serves as identification tag, aiding in cell-to-cell recognition

Question 4

integral protein

Answer 4

a transmembrane protein with the hydrophobic region extending into and often completely spanning the hydrophobic interior of the lipid bilayer. The hydrophilic regions are exposed to the aqueous solutions on either side of the membrane.
carry out transmembrane movement (ex, facilitated diffusion, active transport, intercellular joining, signal transduction)

Question 5

peripheral protein

Answer 5

not embedded in the lipid bilayer and loosely bound to the membrane or to the exposed parts of integral proteins (ex. enzymes that carry out sequential steps of a metabolic pathway, cell communication, conduct signals from the exterior to the interior or vice versa)

Question 6

selective permeability: ions

Answer 6

no permeability because ions are charged: must pass through ion channels or integral proteins

Question 7

selective permeability: large, polar biomolecules

Answer 7

some permeability with difficulty because of polarity and large size

Question 8

selective permeability: small, polar molecules

Answer 8

some permeability because of small size and polarity

Question 9

selective permeability: small, nonpolar molecules

Answer 9

high permeability because of non-polarity and small size

Question 10

passive transport

Answer 10

Does not require energy: diffusion, osmosis, and facilitated diffusion

Question 11

diffusion

Answer 11

the tendency for molecules of any substance to spread out evenly into the available space; down the concentration gradient from an area of high to low concentration; spontaneous process

Question 12

facilitated diffusion

Answer 12

when a transport protein embedded in the membrane assists in the passive transport of polar molecules and ions impeded by the lipid bilayer

Question 13

osmosis

Answer 13

diffusion (net movement) of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Question 14

active transport

Answer 14

the expenditure of energy (usually from ATP) to pump a substance across a membrane against its concentration gradient

Question 15

protein pumps

Answer 15

Electrogenic pumps: proteins that establish and maintain voltage across a membrane (Na+ /K+ pumps in animals)
• Proton pumps: actively transport H+ ions out of the
cell (in plants, fungi, & bacteria)

Question 16

endocytosis

Answer 16

various types of active transport that move particles into a cell by enclosing them in vesicle made out of plasma membrane.

Question 17

exocytosis

Answer 17

form of bulk transport in which materials are transported from the inside to the outside of the cell in membrane-bound vesicles that fuse with the plasma membrane

Question 18

phagocytosis

Answer 18

cell eating

cell engulfs a particle collecting food which is digested by lysosome

Question 19

pinocytosis

Answer 19

cell drinking
cell gulps droplets of extracellular fluid
• Non specific type of transport

Question 20

receptor-mediated endocytosis

Answer 20

cell acquires bulk quantities of a specific substance

• Ligands attaches to receptors inducing vesicle creation

Question 21

Enzymatic Activity

Answer 21

proteins are embedded in the sequence of the metabolic pathway, increasing efficiency and productivity

Question 22

Signal Transduction

Answer 22

protein receptor binds to chemical messenger; the signal may cause the conformational change in the protein (receptor) that relays the message to the inside of the cell

Question 23

Cell to Cell recognition

Answer 23

glycoproteins and glycolipids act as markers that indicate information to surrounding cells
ex. blood type

Question 24

Intercellular Joining

Answer 24

proteins of adjacent cells hook/join together

Question 25

Attachment to cytoskeleton and ECM

Answer 25

microfilaments of cytoskeleton bond to proteins, maintaining cell shape
protein attaches to extracellular matrix to stabilize location of certain membrane proteins

Question 26

Membrane Protein Functions

Answer 26

• Transport
• Enzymatic Activity
• Signal Transduction
• Cell-cell recognition
– Glycoproteins and
glycolipids
• Intercellular joining
• Attachment to
cytoskeleton &
extracellular matrix