Biochemistry 8: Biological Membranes

Question 1

glycoprotein coat

Answer 1

created by carbohydrates associated with membrane-bound proteins

Question 2

lipid rafts

Answer 2

collections of similar lipids with or without associated proteins that serve as attachment points for other biomolecules

often serve roles in signaling

Question 3

flippases

Answer 3

specialized enzymes that assist in the transition or flip of lipids between layers of the cell membrane

Question 4

free fatty acids

Answer 4

carboxylic acids that contain a hydrocarbon chain and a terminal carboxyl group

very few within the cell membrane

Question 5

the “healthier” fats

Answer 5

unsaturated fatty acids

have one or more double bonds

exist in liquid form at room temp

impart fluidity to cell membrane

Question 6

essential fatty acids

Answer 6

alpha - linolenic acid

linoleic acid

Question 7

saturated fatty acids

Answer 7

the main components of animal fats

exist as solids at room temp

Question 8

what’s the difference between a micelle and a liposome?

Answer 8

a micelle is a small monolayered vesicle of phospholipids

a liposome is a bilayered vesicle of phospholipids

Question 9

triacylglycerols

Answer 9

three fatty acid chains esterified to a glycerol molecule

fat storage molecules

act as phospholipid precursors

Question 10

glycerophospholipids

Answer 10

two fatty acids + phosphate group + glycerol head

used for membrane synthesis

Question 11

sphingolipids

Answer 11

lipids without a glycerol

two fatty acids tails with a sphingosine backbone

Question 12

cholesterol

Answer 12

present within the membrane in large amounts

contributes to membrane fluidity and stability

Question 13

waxes

Answer 13

present within the membrane in small amounts

most prevalent in plants

function in waterproofing and defense

Question 14

gap junctions

Answer 14

cell-cell junctions that allow for direct cell-cell communication

formed by alignment of pores composed of connexin molecules

also called connexons

permit movement of water, ions, solutes directly between cells

Question 15

tight junctions

Answer 15

prevent solutes from leaking between cells

prevent paracellular transport but don’t provide intercellular transport

link cells as they form a single layer of tissue

must form a continuous band around the cell in order to be effective

Question 16

desmosomes

Answer 16

bind adjacent cells by anchoring to their cytoskeletons

formed by interactions between transmembrane proteins associated with intermediate filaments

anchor layers of epithelial tissues

Question 17

occluded state

Answer 17

a brief state of a carrier when it binds to a substrate, undergoes a conformational change

it is not open to either side of the phospholipid bilayer

Question 18

primary active transport

Answer 18

active transport that uses ATP or another energy molecule to directly power the transport of molecules across a membrane

generally uses a transmembrane ATPase

Question 19

secondary active transport

Answer 19

active transport that harnesses the energy released by one particle going down its electrochemical gradient to drive a different particle up its gradient

Question 20

outer mitochondrial membrane

Answer 20

highly permeable mitochondrial membrane

many large pores that allow the passage of ions and small proteins

Question 21

inner mitochondrial membrane

Answer 21

mitochondrial membrane that surrounds the mitochondrial matrix

lacks cholesterol and is less permeable

Question 22

Nernst equation

Answer 22

equation to determine the membrane potential from the intra- and extracellular concentrations of ions

= (61.5/z) log([ion]_out/[ion]_in)