unit 2 - membrane structure + function

Question 1

Membrane glycoproteins are most important for_____

Answer 1

distinguishing foreign cells from “self” cells.

Question 2

Spherocytosis is a genetic disease in which ___

Answer 2

the membrane of red blood cells cannot anchor to the cell cortex, red blood cells are destroyed by the patient’s spleen, red blood cells lose their shape, patients develop anemia

Question 3

Which statement best describes how cholesterol affects cell membrane fluidity?

Answer 3

Cholesterol decreases fluidity at high temperatures and increases fluidity at low temperatures

Question 4

unsaturated phospholipids…

Answer 4

increase fluidity – higher concentration in cell membranes exposed to colder temperatures

Question 5

saturated phospholipids…

Answer 5

decrease fluidity – higher concentration in cell membranes exposed to warmer temperatures

Question 6

Transmembrane proteins can span the lipid bilayer as _____

Answer 6

α helices and β sheets

Question 7

The unique functions of different membranes are primarily due to their______

Answer 7

proteins

Question 8

The most common phospholipid present in most cell membranes is____

Answer 8

phosphatidyl choline

Question 9

Detergents are used to disrupt and break plasma membrane because_____

Answer 9

they compete and substitute phospholipids

Question 10

glycerophospholipids

Answer 10

glycerol + 2 fatty acids + phosphate and X alcohol group

Phosphatidyl choline, Phosphatidyl ethanolamine, Phosphatidyl serine, Phosphatidyl inositol, diphosphatidyl glycerol (different groups that bind to the phosphate)

Question 11

sphingophospholipids

Answer 11

sphingosine + 1 fatty acid + phosphate and X alcohol group

X is either choline or ethanolamine

Question 12

Phosphatidylcholine (PC) (lecithin)

Answer 12

most common phospholipid in cell membranes
Its primary role is to provide a structural framework for the membrane and maintain the permeability barrier. It also plays a role in membrane mediated cell signaling.

Question 13

Phosphatidylethanolamine (PE)

Answer 13

cell membranes from the nervous tissue. In brain tissue, PE accounts for approximately half of the phospholipid content.

Question 14

Phosphatidylserine (PS)

Answer 14

negatively charged phospholipid component of cell membranes
very abundant on blood platelets
Important for coagulation cascade.

Question 15

Phosphatidylinositol (PI)

Answer 15

cell membranes that are involved in cell signaling (receiving signals).
It can be phosphorylated by a variety of kinases to form phosphatidy linositolphosphate (PIP).

Question 16

diphosphatidyl glycerol (cardiolipin)

Answer 16

mitochondrial inner membrane of mitochondria. Involved in the electron transport process.

Question 17

cholesterol is found in

Answer 17

animal cells, absent in prokaryotes and plant cell membranes

Question 18

structure of cholesterol

Answer 18

small hydrophyllic hydroxyl group head, carbon rings, nonpolar tail

Question 19

cholesterol at high temperatures

Answer 19

rigid hydrocarbon portion associates with fatty acid tails of phospholipids and decreases their mobility

Question 20

cholesterol at low temperatures

Answer 20

interferes with interactions between fatty acid tails of phospholipids and maintains their fluidity

Question 21

membrane proteins…

Answer 21

carry out most membrain functions, make up 50% of total membrane mass

Question 22

types of integral proteins

Answer 22

transmembrane proteins - spans bilayer either as an alpha helix or a beta pleated sheet
monolayer associated proteins - mainly in cytosol, attached by an alpha-helix to one layer of the bilayer
lipid-linked (lipoproteins) - on surface, covalently attached to lipid groups

Question 23

types of peripheral proteins

Answer 23

protein-linked - associated with other membrane proteins

Question 24

transmembrane protein pores

Answer 24

either a) several alpha helices orb) beta barrel that forms a large channel (ex: porin proteins in mitochondrial membrane) with both hydrophilic and hydrophobic side chains. all hydrophilic side chains face inside the pore, hydrophobic side chains face phospholipids. allow for passage of water soluable molecules through the membrane

Question 25

N-linked oligosaccharides

Answer 25

attached through asparagine sugar is attached starting in ER then completed in the golgi

Question 26

O-linked oligosaccharides

Answer 26

attached through serine or threonine sugar is attached in the golgi alone

Question 27

proteoglycan

Answer 27

proteins with chains of sugars >10

Question 28

glycolipids

Answer 28

least common type of membrane lipid, make up 2% of membrane. all located on outer surface of membrane

Question 29

glycero-glycolipid

Answer 29

glycerol backbone, 2 fatty acids, carbohydrate head

Question 30

sphingo-glycolipid

Answer 30

sphingosine backbone, 1 fatty acid, carbohydrate head either cerbroside (1 sugar residue) or ganglioside (branched chain of several sugars)

Question 31

cerebroside

Answer 31

sphingosine backbone, 1 fatty acid, 1 sugar residue (glucose or galactose)

Question 32

ganglioside

Answer 32

sphingosine backbone, 1 fatty acid, branched chain of many sugar residues with one being sialic acid. function as cell markers in cell-cell recognition ex: blood types

Question 33

functions of carbohydrate layer

Answer 33

protect from mechanical and chemical damage, absorb water and lube up the cells, serve as cell identification (especially in immune system)

Question 34

sialic acid

Answer 34

used by immune cells as self-markers, viruses use them to invade undetected

Question 35

use of liposomes

Answer 35

targeted cancer drug delivery. travel through bloodstream and penetrate leaky tumor cell vaculature but not healthy cells

Question 36

inositol phospholipids function

Answer 36

relay signals from cell surface to the inside of the cell. found only on the side of the membrane that faces the cytosol

Question 37

how are membrane proteins isolated for study?

Answer 37

because they are amphipathic, detergents are used so that they don't lose their structure. hydrophobic tails of the detergent face into the hydrophobic side chain hydrophilic parts of both face the solution

Question 38

cell cortex

Answer 38

framework of fibrous proteins that are attached to the cytosolic surface of the membrane via transmembrane proteins help keep shape of the cell and give strength to the membrane ex: cell cortex in red blood cells help them withstand the mechanical pressures exerted

Question 39

structure of cell cortex

Answer 39

spectrin: dimers of long, flexible proteins that form a meshwork, providing support and maintaining cell shape actin: links the spectrin to the cytoskeleton continuously polymerized and depolymerized, which makes the membrane grow or shrink

Question 40

when are membrane proteins not able to laterally diffuse?

Answer 40

integral membrane proteins attached to the cytoskeleton are completely fixed in place proteins between 2 gap junctions are restricted to only move in the space between them creates specialized regions/membrane domains on cell/organelle surface!

Question 41

which membrane components can flip-flop?

Answer 41

phospholipids occasionally glycolipids never (sugars are only on outside) proteins never

Question 42

tight junctions

Answer 42

impermeable junctions--cells are fused together. serves as a barrier to prevent molecules from passing through the intercellular space

Question 43

desmosomes

Answer 43

anchoring junctions, bind to adjacent cells like velcro. proteins are associated with intermediate filaments of the cytoskeleton. water/solutes can move freely through

Question 44

gap junctions

Answer 44

intercellular channels. allow for intercellular communication via direct diffusion of ions and small molecules from one cell to the next. found in tissues that need fast communication ex: gap junctions allow cardiac muscle to contract as a unit

Question 45

hemidesmosomes

Answer 45

instead of connecting 2 cells together, connects a cell to the basement membrane