9-11

Question 1

What are Dynein and Kinesin?

Answer 1

The proteins that move along the microtubules

• dynein is a dimer and moves towards the negative end of the microtubules—> towards the centrosome (nucleus) - in 9+2 stucture moves along neighbouring doublet of microtubule dragging the other to cause bending
• Kinesin moves away from centrosome

Question 2

Structure of microtubule

Answer 2

25nm across and made of α and β tubulin

Question 3

Examples of movement mechanisms

x 7

Answer 3

1. Outer hair cell motor
2. Invertebrate photoreceptors
3. ATP synthase
4. RNA polymerase
5. Flagella/cilia
6. Actin/tubulin axonal transport
7. Myosin/actin

Question 4

Difference between parallel and series muscle unit structure

Answer 4

PARALLEL - each contract and force but then this is additive for each unit pulling so big force if parallel

SERIES - Adding contractile elements in series amplifies degree of movement as each segment shortens

Question 5

Structure of muscle -

Answer 5

Myofibrils are bundles of protein filaments and then a group of myofibrils makes a muscle fibre (one single muscle cell) and then a bundle of fibres is a fascicle (sheathed in connective tissue) and then the whole skeletal muscle is multiple fascicles

Question 6

What are the dark and light bands of striated (skeletal) muscle

Answer 6

Dark = A band = ANISOTROPIC

Light = I band = ISOTROPIC

Question 7

Structure of a sarcomere

Answer 7

• single contractile unit of a muscle cell
• Z to Z line is 2 μm
• middle is m line which is the middle of the H zone, in the middle of the A band
• next to A band is I band and the Z line is in the middle of this

Question 8

Structure of myosin

Answer 8

6 polypeptide chains

• Main is two supercoiled α helices so dimer with 2 heads and then three of these dimers per section
• the heads have the stiff neck with flexible hinge (each head has a ATP binding site)
• cocked state is the high energy state
• heads at 120 degrees and repeat every 43 nm

Question 9

Structure of actin - F actin

Answer 9

G actin dimers into filaments

• polarised with + and - ends
• Tropomodulin at negative end
• g dimers to + at 5-10 x faster than loss at -
• 40nm sections and differ from 43 of heads of myosin - maybe purposeful desynchronisation (dont actually know why)

Question 10

Other proteins of the thin actin filament

Answer 10

Tmod = tropomodulin at negative end

• Tropomyosin - cover myosin binding sites - is a dimer
• Troponin holds tropomyosin in place as its association is weak - moves it out of the way
• nebulin but do not know of function

Question 11

Troponin structure

Answer 11

2 subunits

TnI inhibitory element and binds to actin

TnT binds to tropomyosin

TnC binds to Ca2+ and this causes the troponin to make a lateral shift of tropomyosin

Question 12

What is titin?

Answer 12

largest protein in genome

• like a spring and maybe to protect against overstretching of sarcomere
• half life of roughly 3 days so continuously repaired

Question 13

Structure of sarcomere diagram (so can draw)

Answer 13

diagram

- twice as many thin filaments as thick

Question 14

What visually changes to sarcomere during contraction?

Answer 14

I band shrinks but the A band is constant size

- H zone reduces as well

Question 15

What is the cross-bridge cycle?

x 6

Answer 15

1. ATP binds to myosin heads and so dissociates from actin
2. Break to ADP and Pi which causes head to cock into high energy position
3. head attaches to myosin site on actin and releases Pi (strengthens binding and activates power stroke)
4. Power stroke
5. ADP dissociates from myosin head
6. ATP attaches to head to cause dissociation from actin

Question 16

What causes the start of contraction?

Answer 16

Release of Ca2+ from sarcoplasmic reticulum
- binds to TnC which moves tropomyosin

• force production rises rapidly for only a small rise in Ca2+

Question 17

How do muscle fibres ensure Ca2+ gets to all sarcomeres?

Answer 17

invaginating membrane as otherwise diffusion would take too long

• so near synchronous activation
• done via t-tubules

Question 18

Structure and purpose of t -tubules

Answer 18

90nm across and penetrate into fibre
- cause the shallow slope after depolarisation
- small and few ions
has Cl- ions to aid in repolarisation
- is K+ accumulates during intense activity can cause problems-volume

Question 19

What is myotonia congenita

Answer 19

inherited condition which skeletal muscle goes into contracture
- chloride channel mutation of t-tubules

Question 20

Where is Ca2+ stored?

Answer 20

sarcoplasmic reticulum

• has a system where wraps around tubule system
• in SR is calsequestrin which is a calcium buffer
• calcium channels are ryanodine receptors

Question 21

Triadic regions of t tubules

Answer 21

two SR terminal cisternae either side of t-tubule in triad form
- t tubule dihydropyridine receptors are voltage sensors on surface of t tubule and line up with ryanodine receptors on both SR membranes so quick release of Ca2+ when membrane depolarisation

Question 22

What delays force production in muscles?

Answer 22

Ca2+ build in concentration and then the binding of 4 Ca2+ to troponin as require all 4 to be full activation

Question 23

What is SERCA

Answer 23

the pump that transports Ca2+ back into SR to stop muscle contraction
- activated when ca2+ released

Question 24

What does temporal summation of calcium concentration

Answer 24

tetanus from multiple action potentials and calcium cannot be taken up quickly enough between AP

Question 25

Describe a motor unit

Answer 25

the nerve and innervated muscle fibres | - and each motor unit can be low or high force by containing a smaller number of muscle fibres

Question 26

What is asynchronous activation?

Answer 26

Different motor units recruited one after another usually in order of size when force increases - controlled by central pattern generations

Question 27

What are muscle spindles?

Answer 27

Muscle spindles are proprioceptors that consist of intrafusal muscle fibers enclosed in a sheath - they provide information on muscle length and positioning

Question 28

Cardiac muscle

Answer 28

striated with no tendons as pull on next cell (the intercalated disks) - contract around the chambers and the cells have gap junctions between then to allow for conduction between cells - part between two intercalated disks is a myocyte

Question 29

Smooth muscle

Answer 29

striation is less obvious and wrapped around vessels and organs - efficient and long lasting contraction - dont have an end plate, have gap junctions and are thin and spindle like cells

Question 30

Insect asynchronous muscle

Answer 30

contraction of antagonist muscle activates contraction in the muscle which then causes antagonist to contract

Question 31

atrophy vs hypertrophy

Answer 31

``` at = disuse hyper = with use ```

Question 32

What affects the speed of muscle twitches?

Answer 32

Temperature and the types of muscle fibre

Question 33

4 types of muscle fuel (providing atp)

Answer 33

1. ATP store 2. Phosphocreatine 3. Lactic acid system 4. Aerobic respiration GRAPH (pg 10 lecture14)

Question 34

How does phosphocreatine work?

Answer 34

can phosphorylate ADP to make more ATP

Question 35

What is VO2 max?

Answer 35

the max oxygen taken in per kg per minute

Question 36

What is myoglobin?

Answer 36

the oxygen binding protein in muscles similar to haemoglobin | - a lot in red muscle and not as much in white muscle

Question 37

Properties of slow oxidative fibres - type 1 of red muscle x 8 and example

Answer 37

1. small diameter 2. low force per area 3. low Vmax 4. low myosin ATPase activity 5. High fatigue resistance 6. A lot of mitochondria 7. high oxidative capacity 8. low number of oxidative enzymes example = postural muscles in humans

Question 38

Properties of fast oxidative fibres - type 2 red muscle x 8 and examples

Answer 38

1. Medium diameter 2. medium force per unit area 3. medium Vmax 4. High myosin ATPase activity 5. medium fatigue resistance 6. a lot of mitochondria 7. high oxidative capacity 8. medium number of glycolytic enzymes example is flight muscles in migratory birds

Question 39

Properties of fast glycolytic fibres - white muscle x 8 and examples

Answer 39

1. large diameter 2. high force per unit area 3. high Vmax 4. high myosin ATpase activity 5. Low fatigue resistance 6. Few mitochondria 7. low oxidative capacity 8. High number of glycolytic enzymes example is chicken breast

Question 40

The length-tension relationship for a whole muscle

Answer 40

graph

Question 41

Using a single fibre length to explain active tension relationship

Answer 41

graph

Question 42

What is isometric contraction

Answer 42

Tension increase but not movement so not work done | - lifting something that is too heavy

Question 43

What is isotonic contraction?

Answer 43

when the muscle shortens and there is the same tension throughout the movement - bicep curl

Question 44

what is Work?

Answer 44

Work in joules is force x distance | - force is mass x acceleration

Question 45

How can isometric contraction still cause fatigue?

Answer 45

as no work but as there is tension then ATP is being used and therefore muscle fatigues

Question 46

What is power (watts)

Answer 46

joules per second = force x velocity

Question 47

Force velocity relationship

Answer 47

graph

Question 48

How do muscle shapes help alter mechanics of movement? | 2 examples

Answer 48

different types of movement with different force and speed of contraction 1. strap muscle like the bicep has lots of series elements and produces large movement with high velocity but low force 2. unipennate like intercostal muscle with lots of parallel elements produce small movement with low velocity but high force