Biochemistry Chapter 8: Biological Membranes

Question 1

Fluid mosaic model

Answer 1

Accounts for the presence of lipids, proteins, and carbohydrates in a dynamic, semisolid plasma membrane that surrounds cells.

Question 2

lipid rafts

Answer 2

assemblies of lipids that move freely in the plane of the membrane

Question 3

flippases

Answer 3

specific membrane proteins that maintain the bidirectional transport of lipids between the layers of the phospholipid bilayer in cells.

Question 4

Triacylglycerols and free fatty acids

Answer 4

phospholipid precursors and are found in low levels in the membrane

Question 5

glycerophospholipids

Answer 5

replace one fatty acid with a phosphate molecule which is often linked to other hydrophilic groups

Question 6

cholesterol

Answer 6

present in large amounts and contributes to the membrane fluidity and stability

Question 7

Waxes

Answer 7

present in very small amounts, if at all; they are most prevalent in plants and function in waterproofing and defense.

Question 8

Transmembrane proteins

Answer 8

can have one or more hydrophobic domains and are most likely to function as receptors or channels.

Question 9

Embedded proteins

Answer 9

most likely part of a catalytic complex or involved in cellular communication.

Question 10

Membrane-Associated proteins

Answer 10

May act as recognition molecules or enzymes

Question 11

Carbohydrates

Answer 11

can form a protective glycoprotein coat and also function in cell recognition.

Question 12

Gap junctions

Answer 12

allow for the rapid exchange of ions and other small molecules between adjacent cells.

Question 13

Tight junctions

Answer 13

prevent paracellular transport, but do not provide intercellular transport

Question 14

Desmosomes and hemidesmosomes

Answer 14

anchor layers of epithelial tissue

Question 15

Concentration gradients

Answer 15

Help to determine appropriate membrane transport mechanisms in cells

Question 16

Osmotic pressure

Answer 16

the pressure applied to a pure solvent to prevent osmosis and is used to express the concentration of the solution

Question 17

Passive transport

Answer 17

does not require energy because the molecule is moving down its concentration gradient or from an area with higher concentration to an area with lower concentration

Question 18

osmosis

Answer 18

describes the diffusion of water across a selectively permeable membrane

Question 19

Facilitated diffusion

Answer 19

uses transport proteins to move impermeable solutes across the membrane.

Question 20

Active transport

Answer 20

requires energy in the form of ATP or an existing favorable ion gradient
- Can be primary or secondary

Question 21

Symport

Answer 21

both molecules flow in the same direction across the membrane

Question 22

Antiport

Answer 22

Molecules flow in opposite direction across the membrane

Question 23

Primary active transport

Answer 23

directly transports molecules across a membrane.

Question 24

Secondary active transport

Answer 24

aka coupled transport
uses energy to transport molecules across the membrane w/o direct coupling to ATP. Instead it uses energy from one particle going down concentration to another going up.

Question 25

Pinocytosis

Answer 25

The ingestion of liquid into the cell from vesicles formed from the cell membrane and phagocytosis.

Question 26

How is membrane potential maintained?

Answer 26

by the sodium-potassium pump and leak channels

Question 27

Nernst equation

Answer 27

the equation that can determine the electrical potential created by one ion

Question 28

Goldman-Hodgkin-Katz Voltage Equation

Answer 28

resting potential of a membrane at physiological temperature can be calculated using this equation