Cell bio- cytoskeleton

Question 1

What are the three components of a cytoskeleton

Answer 1

actin filaments
microtubules
intermediate filaments

Question 2

actin filaments

Answer 2

determine the shape of a cell and are necessary for locomotion

Question 3

mictotubules

Answer 3

determine the positions of membrane-enclosed organelles, direct intracellular transport and form mitotic spindle

Question 4

intermediate filaments

Answer 4

provide mechanical strength

Question 5

microtubules structure

Answer 5

hollow. polymer of the protein tubulin= heterodimer of alfa-tubulin and beta-tubulin

Question 6

alfa-tubulin

Answer 6

GTP molecule that is trapped and never hydrolyzed

Question 7

beta-tubulin

Answer 7

GTP bound that is exchangeable with GDP

Question 8

dynamic instability

Answer 8

process of microtubules to grow and shrink.

influenced by the binding and hydrolysis of GTP on the beta-tubilin

Question 9

Microtubule organizing center (MTOC)

Answer 9

centrosome= origination or microtubules

Question 10

Microtubule-associated proteins (MAPs)

Answer 10

move along microtubules bringing transport vesicles to target organelles in the cell

Question 11

two types of MAPs

Answer 11

kinesin= travels toward plus end
Dynein= travels toward minus end

Question 12

Functions of MAPs (2)

Answer 12

Move organelles and vesicles in the cell

move vesicles with pigments (melanosomes) in the skin

Question 13

Flagella

Answer 13

used to move cells in a liquid environment

Question 14

cilia

Answer 14

move fluid above a cell

Question 15

Actin structure

Answer 15

2 parallel protofilaments in helix

Question 16

Actin filaments grow and shrink

Answer 16

polymerization of ATP= grow depolymerize= shrink

Question 17

two forms of actin crosslink

Answer 17

bundle-forming= parallel
gel-forming= weave

Question 18

actin-associated proteins (3)

Answer 18

Kinsein= moves to plus end
dynein= moves to negative end
myosin= muscle contraction

Question 19

Sarcomere structure

Answer 19

Z-disk= separates sarcomers
Dark band= myosin
Light band= actin filaments

Question 20

tropomyosin

Answer 20

bind to actin to prevent myosin from binding when CA2+ is absent, is removed with Ca2+

Question 21

Intermediate filament characteristics

Answer 21

no polarity, no ATP or GTP, no movement, no motor proteins

associated with cell-cell junctions to strengthen the cells and epithelia

Question 22

intermediate filament structure

Answer 22

16 dimers= 32 coiled monomers

Question 23

types of intermediate filament proteins in vertebrate cells (2)

Answer 23

nuclear= Lamina A,B,C
epithelial= Type 1 keratins (acidic), type 2 keratins (basic)

Question 24

majority Intracellualr ions (2)

Answer 24

K+

H+

Question 25

majority extracellualr ions (4)

Answer 25

Na+ Cl Mg2+ Ca2+

Question 26

Permeability of lipid bilayer

Answer 26

permeable: hydrophobic molecules semipermeable: small and large uncharged polar molecules nonpermeable: ions

Question 27

membrane potential

Answer 27

the membrane potential of an unstimulated cell= resting

Question 28

electrochemical gradient

Answer 28

combination of membrane potential and concentration gradient of the solute

Question 29

7 ways a protein can associate with the plasma membrane

Answer 29

1. single alfa helix 2. multiple alfa helicies 3. rolled-up bets sheet (beta barrel) 4. attached only to one layer (with one hydrophobic face) 5. attached to the membrane by covalently bound lipid chain 6. via an oligosaccharide 7. attached to other proteins (inside or outside the cell)

Question 30

transporter structural features (5)

Answer 30

built from 10+ alfa helicies (transmembrane domains) binding sites are located midway through the membrane show two different states (inward-open and outward-open conformation) binding sites are accessible by passageways from only one side of the membrane at one time could work in reverse direction if ion and solute gradients were adjusted

Question 31

two examples of transmembrane proteins

Answer 31

``` Na/glucose cotransporter (SGLT) glucose transporter (GLUT) ```

Question 32

two main classes of membrane transport proteins

Answer 32

channels and transporters (carriers)

Question 33

channels

Answer 33

form pores for specific solutes (ions, water, ammonia) | weakly interact with the solute

Question 34

transporters

Answer 34

bind the specific substrate (solute) to be transported | undergo a series of conformational changes

Question 35

4 typed of ion channels

Answer 35

``` voltage-gated (na+ Channel) ligand-gated extracellular (nicotinergic receptor) ligand-gated intracellular mechanically gated (inner ear mechanosensitive channel) ```

Question 36

passive transport

Answer 36

transports sown a concentration gradient | occurs spontaneously by diffusion

Question 37

active transport

Answer 37

require energy ans ia mediated by transporters | moves solutes against its concentration gradient

Question 38

passive diffusion

Answer 38

molecule dissolves in the phospholipid bilayer, diffuses across it, then dissolves in the qa solution at the other side no membrane proteins are involved direction is determined by the relative concentration inside and outside the cell net flow= down concentration gradient: high to low concentraiton

Question 39

facilitated diffusion

Answer 39

direction determined by relative concentrations inside and outside the cell no external source of energy passage is mediated by proteins that enable the transported molecule to cross the membrane without interacting with hydrophobic interior (allows passage of polar molecules)

Question 40

classification of active transporters (2)

Answer 40

direction: uiport, symport, antiport energy: primary, secondary, tertiary

Question 41

uniporters

Answer 41

passive transport of only one molecule

Question 42

symporters

Answer 42

coupled transporters of 2 molecules in the same direction (co-transporters)

Question 43

antiporters

Answer 43

transport of a second molecule in the opposite direction

Question 44

secondary active transporters

Answer 44

driven by a gradient that has been generated by a primary active transporter

Question 45

tertiary active transporters

Answer 45

driven by a gradient by a secondary active transporter

Question 46

example of primary active transporter

Answer 46

Na+, K+ ATPase 3 na+ molecules exit while 2 k+ molecules enter the cell use ATP

Question 47

example of secondary active symporter

Answer 47

sodium glucose cotransporter (SGLT) one glucose with 2 Na+ are transported inside the cell transports glucose against concentration gradient

Question 48

examples of secondary active antiporters (2)

Answer 48

sodium/calcium exchanger (NCX) and sodium/proton exchanger (NHE) transport against CA and H gradient

Question 49

example of tertiary active transporter

Answer 49

proton/peptide symporter

Question 50

aquporins

Answer 50

specific water channels | for cells that secrete or reabsorb high amounts of water= more efficient