Motor Proteins and Muscles

Question 1

structure for moving in single-celled animals vs multicellular

Answer 1

use motor porteins and cytoskeleton!
single-celled use flagella and cilia
multicellular use skeleton and muscles

Question 2

cytoskeleton

Answer 2

network of filaments that support plasma membrane, give cell overall shape, correct positioning of organelles, tracks for transport of vesicles, allow cells to move
microfilaments, intermediate filaments, microtubules

Question 3

motor proteins

Answer 3

microfilaments and microtubules are tracks for their movement
motor proteins use energy in the form of ATP to walk along te filaments

Question 4

microfilaments aka actin filaments

Answer 4

actin portein subunits, tracks for myosin motor portein

Question 5

sarcomeres

Answer 5

organized structures of overlapping filaments of microfilaments -> control muscle movement

Question 6

microtubules

Answer 6

tubulin proteins, hollow, straw-like tube for tracks for kinesin and dyenin motor proteins; important for cellular structural integrity and cell movement; cell movement via cilia and flagella (dynein) while kinesin is for movement of vesicles and intracellular cargoes

Question 7

Flagella

Answer 7

long, hair-like structures that extend from cell surface to move entire cell; sperm; usually one or few on a cell

Question 8

Motile cilia

Answer 8

shorter, large numbers on the cell surface; cilia in upper respiratory system moves dust out towards nostrils

Question 9

9 +2 Array

Answer 9

cilia and flagella - 9 pairs of microtubules in a circle with 2 other tubes in the cross-section
pairs are connected by protein bridges and dyneins that move along the microtubules - causes the flagellum or cilium to beat; causes the entire structure to bend

Question 10

3 types of muscle tissues

Answer 10

skeletal, smooth, cardiac

Question 11

skeletal muscle

Answer 11

control locomotion and any conciously controlled movement
voluntary muscle
long and cylindrical, striped or striated appearance -> regular arrangement of contractile proteins (actin and myosin); also multiple nuclei in one cell

Question 12

smooth muscle

Answer 12

hollow organs like intestines, stomach, urinary bladder, passages like respiratory tract and blood vessels
not voluntary control - involuntary muscle
no striations
one nucleus per cell

Question 13

cardiac muscle

Answer 13

heart only - pump blood and maintain blood pressure; also involuntary muscle

Question 14

pacemaker cells

Answer 14

spontaneously initate cardiac muscle contraction so that heart can beat without nervous system (nerves can slow or speed up heart rate tho..)
one nucleus per cell, branches

Question 15

intercalated disks

Answer 15

allow rapid passage of action potentials from one cardiac muscle cell to the next

Question 16

skeletal muscle fiber

Answer 16

single skeletal muscle cell - incredible large, up to 30 cm

Question 17

myofibrils

Answer 17

within each muscle fiber
long cylindrical structures that lie parallel to muscle fiber
contains repeating units of sarcomeres (contractile units); give muscles a banded appearance

Question 18

myosin

Answer 18

thick dark filament

Question 19

actin

Answer 19

thin light filament

Question 20

Z discs or lines

Answer 20

structures at the end of each sarcomere where actin filaments are physically anchored

Question 21

M line

Answer 21

center of the myosin filament

Question 22

when the sarcomeres contract individually:

Answer 22

myofibrils and muscle cells shorten BUT the actin and myosin fibers are the same length they just slide past each other

Question 23

tropomyosin and troponin

Answer 23

strands of tropomyosin block the binding sites and prevent actin-myosin interactions when the muscles are at rest
troponin regulates tropomyosin
calcium ions regulate troponin: binding calcium to troponin causes the troponin-tropomyosin complex to move away from myosin binding sites on the actin filament, allowing myosin to bind to actin and initiate contraction

Question 24

sliding filament model

Answer 24

the thick and thin filaments slide by one another causes sarcomere to shorten while the filaments remain the same length
done by the cross-bridge cycle of actin-myosin binding

Question 25

cross-bridge cycle

Answer 25

1. myosin binds to ATP but it is not bound to actin
2. Myosin turns ATP into ADP and inorganic phosphate and myosin is still bound to both molecules; now it can attack to myosin-binding site on actin if available (remains in this state if there even aren’t any available)
3. myosin releases inorganic phosphate, still bound to ADP, intiates the Powerstroke and pulls the actin filament towards the M line and causes muscle contraction
4. then ADP is released and it remains stuck to the actin filament until another ATP molecule is bonded - depletion of ATP due to muscle fatigue will cause muscles to remain locked in contracted state

Question 26

importance of troponin and tropomyosin

Answer 26

determine where myosin binds to actin or not by blocking the binding sites without nervous input during a resting state
calcium changes conformation and makes the binding site available

Question 27

sarcoplasmic reticulum

Answer 27

endoplasmic reticulum in muscle cells where calcium is stored; nervous system regulates availability of calcium

Question 28

neuromuscular junction or synapse

Answer 28

structure that receive signals from efferent neurons to control muscles
receives acetylcholine as its neurotransmitter -> intiates an action potential like in a normal nueron with depolarization; spreads through structures T-tubules which carry action potential to SR -> release calcium
afterwards when muscle cell is returning back to membrane potential, calcium is pumped back into SR