bern & levy

Question 1

cytoskeleton filaments

Answer 1

actin filament
intermediate filament
microtubule

Question 2

actin filament in muscle cells and other cells

Answer 2

muscle cell: critical component of contractile apparatus

other cells: involved in locomotion..eg. macrophages

Question 3

Actin makes up core of, and links what?

Answer 3

Microvilli, and links interior of cell to adjacent cells through cell junctions.. eg. zonula adherens and zonula occludens

Question 4

Intermediate filament types …. simple examples

Answer 4

Several diff types varying by cell. eg. Keratin filament found on epithelial cells, neurofiliaments found in neurons

Question 5

intermediate filament function

Answer 5

Primarily structural in function.
can link interior of cell to adjacent cells via desmosomes
can link interior of cell to to surrounding extracellular matrix via hemidesmosomes

Question 6

Microtubule function

Answer 6

Many functions with IN the cell:

• IC transport of vesicles e.g. neurotransmitters
• Chromosome movement during mitosis and meiosis
• Movement of cilia and flagella e.g. tail of spermatozoa

Question 7

Microtubule formed from

Answer 7

alpha and beta tubulin dimers

Question 8

microtubule formation

Answer 8

its organizing center exists near the cell’s nucleus, microtubles grow out from this center toward periphery

Question 9

Microtubules use what motor proteins and how do they work

Answer 9

Kinesin: drives transport from center toward periphery

Dynein: opposite

Dynein is the motor protein that drives the movement of both cilia and flagella.

Question 10

Plasma membrane important functions… 6

Answer 10

• Selective transport of molecules in and out ( a function carried out by membrane transport proteins)
• cell recognition via surface antigens
• cell communication through NT and hormone receptors and signal transduction pathways
• tissue organization, temporary or permanent cell junctions, as well as interaction with EC matrix
• enzymatic activity
• determination of cell shape by linking cytoskeleton to plasma membrane

Question 11

lipids and proteins can diffuse withIN

Answer 11

the plane of the membrane

Question 12

the major lipids of the plasma membrane are

Answer 12

Phospholipids and phosphoglycerides

Question 13

majority of membrane phospholipids have what backbone

Answer 13

glycerol

except sphingomyelin

Question 14

Common alcohols are ?

Answer 14

Choline 
ethanolamine 
serine 
inositol 
glycerol

Question 15

sphingomyelin ( an important phospholipid ) has what as its backbone

Answer 15

it has the amino alcohol sphingosine as its back bone instead of glycerol

Question 16

phospholipids that are predominantly in the outer leaflet

Answer 16

phosphatidylcholine

sphingomyelin

Question 17

phospholipids that are predominantly in the inner leaflet

Answer 17

Phosphatidylethanolamine
phosphatidylserine
phosphatidylinositol

Question 18

Cholesterol- critical lipid component of bilayer

Answer 18

Found in both leaflets, stabilizes membrane at normal body temp ( 37c)
-it can represent as much as 50% of lipids found in membrane

Question 19

Glycolipid- minor component of bilayer

Answer 19

GPI plays an important role in anchoring proteins to the outer leaflet of the membrane

Question 20

Cholesterol, glycolipids, phospholipids are

Answer 20

amphipathic

Question 21

The presence of unsaturated fatty acyl chains in phospholipids and glycolipids will do what to membrane fluidity

Answer 21

increase

Question 22

lipids that aggregate e.g sphingomyelin and cholesterol form what

Answer 22

lipid raft

Question 23

Lipid rafts function

Answer 23

different functions, important one being to segregate signaling mechanisms and molecules.

Remember, lipid rafts often have specific proteins associated with them and diffuse in the plane of the membrane as a discrete unit

Question 24

membrane proteins

Answer 24

As much as 50% of the membrane is composed of proteins

Question 25

membrane proteins classified into 3 types

Answer 25

integral lipid anchored peripheral

Question 26

Integral membrane protein

Answer 26

Besides the obvious that they are embedded in the lipid bi layer. they are embedded where hydrophobic amino acid residues are associated with the hydrophobic fatty acyl chains of the membrane lipids

Question 27

integral membrane protein info

Answer 27

many span the bilayer and are termed Transmembrane proteins, Thus they (transmembrane proteins) must have hydrophilic and hydrophobic region

Question 28

Transmembrane proteins hydrophobic/philic regions

Answer 28

hydrophobic region often in form of alpha helix with hydrophobic A.A. facing out and spaning the membrane hydrophilic A.A. residues are then exposed to aqueous environment on either side of the membrane

Question 29

Proteins can also be attached to the membrane via lipid anchors

Answer 29

Protein is covalently attached to a lipid molecule which is then embedded in one leaflet of the bilayer

Question 30

Proteins can be attached to outter leaflet e.g. GPI and inner leaflet by?

Answer 30

Proteins can be attached to inner leaflet via their N-terminus by fatty acids e.g. palmitate or via their C terminus by prenyl anchors

Question 31

Peripheral proteins

Answer 31

May associate with the polar head groups of the membrane lipids or lipid-anchored proteins.

Question 32

ICF and ECF are composed primarily of ?

Answer 32

H2O in which solutes (e.g. ions, glucose, A.A.) are dissolved.

Question 33

Amount of H20 that can enter or leave the cell via AQPs can be regulated by ?

Answer 33

Altering the # of AQPs in the membrane, OR by changing the permeability ( i.e. gating). -changes in pH have been indentifies as one factor that can modulate the permeability of AQPs.

Question 34

Ion channels

Answer 34

found in all cells, especially important in excitable cells e.g. neurons and muscle cells

Question 35

Ion channel selectivity

Answer 35

can be highly selective- only letting one specific ion pass | or non selective-allow all or a group of ions pass. e.g. cations or anions

Question 36

Ion channel conductance

Answer 36

- another way to characterize ion channels - expressed in picosiemens (pS) - For some channels conductance varies depending on which direction the ion is moving. e. g. if the channel has greater conductance when ions are moving into the cell versus out of the cell, the channel is said to be an inward rectifier.

Question 37

Ion channels can be classified by what 3 ways?

Answer 37

Selectivity conductance mechanism of gating `

Question 38

Ion channels mechanism of gating

Answer 38

the fluctuate between an open or closed state (gating) Factors that can control gating: - membrane voltage - extracellular agonist/antagonist e. g. acetylcholine is an EC agonist - intracellular messengers e. g. Ca2+, ATP, cGMP - mechanical stretch of the plasma membrane

Question 39

Transmembrane ion flux can be regulated by?

Answer 39

Changing # of ion channels in membrane or by gating the channels

Question 40

Solute carriers

Answer 40

Represent a large number of membrane transporters They are divided into 3 major functional groups: - Uniporters e.g. GLUT2 - Symporters (co-transport) - Antiporter (exchangers, counter transporter)

Question 41

ATP dependent transporters

Answer 41

ATPase ion transporter | ATP-binding cassette transporters (ABC-transporters)

Question 42

ATPase transporters sub types

Answer 42

P-type ATPase: being phosphorylated during the transport cycle e.g. N/K ATPase V-type ATPase: e.g. H+ ATPase is found in the membranes of several intracellular organels ( e.g. endosomes, lysosomes)

Question 43

ABC trasporters found in

Answer 43

both prokaryotic and eukaryotic cells and share a common feature of having A.A. domains that bind ATP 7 sub groups transport diverse group of molecules/ ions, including Cl-, Cholesterol, Bile acids, Drugs, Iron, and Organic anions.

Question 44

Na/K ATPase

Answer 44

has 3 subunits: - Alpha - Beta - Gamma

Question 45

the 3 types of endocytosis

Answer 45

pinocytosis phagocytosis receptor-mediated endocytosis

Question 46

Endocytosis involves a number of accessory proteins including...

Answer 46

(in order) | adaptin, clathrin, and the GTPase dynamin

Question 47

Exocytosis can be either

Answer 47

constitutive or regulated constitutive e.g. plasma cells secreting immunoglobin or fibroblast secreting collagen regulated occurs in endocrine cells, neurons, exocrine glands (pancreatic acinar cells)

Question 48

exocrine cells secretory product is

Answer 48

after synthesis and processing is stored in secretory granules until a signal is received to be released -signal may be hormonal or neural

Question 49

Fusion of secretory vescile/granule is mediated by

Answer 49

a nummber of accessory proteins -one important one being SNARE's (membrane proteins help target the vesicle to the plasma membrane, process of secretion usually triggered by an increase in Ca2+

Question 50

Receptor mediated endocytosis

Answer 50

- a receptor on the surface of the cell binds to the ligand-- clathrin coated pit is formed with adaptin linking the receptor molecules to the clathrin. - Dynamin a GTPase, assist the separation of the endocytic vesicle from the membrane

Question 51

Diffusion

Answer 51

a random process driven by the thermal motion of the molecules

Question 52

Fick's first law of diffusion

Answer 52

rate at which a molecule diffuses from point A to point B

Question 53

diffusion coefficient takes into account

Answer 53

The thermal energy of the molecule, size, and viscocity of the medium through which the diffusion is taking place.

Question 54

diffusion coefficient for spherical molecule

Answer 54

it is approximated with the stokes einstein equation