Membranes 1: Structure and Function

Question 1

flippase

Answer 1

catalyzes the flipping of phospholipids from one side of the membrane to the other

Question 2

lipid rafts

Answer 2

• take advantage of the fact that the lipid membrane composition is asymmetrical.
• these are more rigid that the surrounding membrane because they are rich in cholesterol and sphingolipids dervied from the outer leaflet
• responsible for concentrating ligand-receptor complexes into coated pit regions of the plasma membrane for RME and are important in bringing together the components of signal transduction pathways

Question 3

fluidity factors

Answer 3

• due to the flexibility in the acyl chain (the head groups tend to stay in place due to hydrophilic interactions)
• temperature
• lipid chain length, increasing length decreases fluidity
• degree of unsaturation, less saturation increases fluidity by increasing the number of cis double bonds (kinks in the chain)
• cholesterol content, under most conditions cholesterol acts to decrease fluidity but this can depend on tempo and lipid composition

Question 4

walking pneumonia

• prevelance
• cause
• mycoplasma mechanism of pathogenicity and effects

Answer 4

• the most common pneumonia in humans
• caused by in increase in the fluidity of the plasma mem of specific cells
• mycoplasma go to the base of the cilia in the lung cells and feed on the cholesterol in the plasma mem of the cilia, causing the mem to become fluid
• cilia become limp and can no longer beat causing mucus accumulation (mycoplasma like to live in the mucus rich environment)
• this can cause secondary bacterial pneumonia

Question 5

Fusion:
what it is
example and general principles

Answer 5

• lipid membranes ability to spontaneously and rapidly fuse with one another
• this is how vesicles fuse with membrane bound organelles or the cell membrane
• proteins in the vesicle membrane then become part of the membrane of which it fused
• contents of vesicle spill out onto opposite side of mem

Question 6

HIV and fusion:
cells recognized
infection of cell
consequences of infections

Answer 6

• CD4 T cell receptors and macrophages recognize a viral coat protein
• when these receptors bind HIV, there is a rapid fusion between the viral coat lipids and the host cell allowing for entry of viral proteins and nucleic acids
• now the host cell will make viral coat proteins and express them on the cell surface, allowing infected cell to fuse with other CD4 cells forming dysfunctional multinucleated cells

Question 7

Measles and fusion

Answer 7

-works in exactly the same mechanism as HIV

Question 8

Phospholipids:

• composition
• property (energy)

Answer 8

• polar head, phosphate group, glycerol group (with fatty acid that make up mem interior)
• fusogenic (energetically favorable)

Question 9

Sphingolipids:

• propert
• physical comp (general)
• clinical signifigance

Answer 9

• not fusogenic
• look like phospholipids
• if not disposed of properly, lysosomal storage diseases can occur

Question 10

Tay-Sachs :
cause
effect

Answer 10

• enzyme deficiency in hexosaminidase
• disrupts sphingolipid breakdown
• build up of GM2 gangliosides which causes mental retardation, blindness, and early death

Question 11

Fabry’s:
cause
effect
treatment

Answer 11

• an alpha galactosidase A deficiency results in the build up of ceramide in lysosomes
• causes a rash on the inner lip/tongue as well as kidney failure
• treated with enzyme replacement therapy

Question 12

eicosanoids
prevelance
function
3 classes (described on separate cards)

Answer 12

• make up a small percentage of the plasma membrane
• made from phospholipids in the membrane and are precursors for major regulatory functions
• 3 classes: prostaglandins, thromboxanes, and leukotrienes

Question 13

prostaglandins
function (2)
tissue specificity

Answer 13

• carry out vasodilation/constriction, uterine contranction**, etc.
• found in many cell types like mast, kidney, spleen, and heart

Question 14

thromboxanes

function

Answer 14

induce platelet aggregation and function in clotting and vasoconstriction

Question 15

leukotrienes
function
clinical significance
tissue specificity

Answer 15

increase white blood cell motility

• play a role in asthma and anaphalaxis
• found in monocytes, mast cells, leukocytes, basophils, and epithelium

Question 16

cholesterol

Answer 16

“a wild and wacky lipid of two minds” end quote

Question 17

integral proteins:
definition (with correlate to research)
composition
EC specific note
variation
function
cell example of function

Answer 17

• emebedded in the membrane and can only be removed with detergent
• 3 domain proteins with extracellular (hydrophillic), membranes spanning (hydrophobic), and intracellular (hydrophillic) components
• extracellular doamin is glycosylated
• may span the membrane once or more than once
• on the tissue level these are important for structural integrity
• determines rigidity for cell to function (erythrocyte is good example)

Question 18

peripheral proteins

Answer 18

• proteins loosely associated with the plasma membrane

- can be removed without detergents, simply by pH changes

Question 19

glycoproteins

Answer 19

-play important role in the recognition of self which is imperative to immune function

Question 20

blood type and glycoproteins

Answer 20

• types is determined by the presence or absence of specific glycoproteins on the erythrocyte surface
• these glycoproteins are remembered by the immune system so if a foreign type is introduced it will trigger a response (often fatal)
• exception is type O, it lacks all of the immunogenic glycoproteins

Question 21

Coccidiosis:
what
native to
mode of action
identification

Answer 21

• pathogenic protozoan that can be found in water or food in developing countries
• binds to glycoproteins on the cell surface of cels in the GI tract
• these classes of glycoproteins change as you move down the GI tract and certain strains of coccidia recognize different classes of GI surface glycoproteins, thus allowing to ID the protist based upon location of infection
• treatment is the same for each protist but it is valuabe to know for the sake of public health professionals dealing with the source

Question 22

toxoplasmosis

Answer 22

• pathogen found in cat feces
• causes severe birth defect in unborn babies
• this protozoan binds to certain cells in the body based upon glycoproteins expressed