AN SC 420 Quiz 1
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AN SC 420 Quiz 1
AN SC 420 University Alberta Carcass Meat Quality
Carcass and Meat Quality
What are the 3 main proteins in meat?
Myofibrillar (myosin, actin)
Sarcoplasmic (enzs, myoglobin, forms gel around cooked meat)
Connective (collagen, elastin)
What provides glysine to meat?
Every 3rd AA is gly in collagen
What are the 4 lipids in meat?
Cholesterol (mems, fluidity, sex hormones)
What are the 5 principal phospholipids?
What are the 2 essential FAs?
What is the limited FA?
What FAs are present in grain-fed animals?
Oleic acid (C18:1 c-9)
Linoleic acid (C18:2)
Linoleic acid (C18:3)
What FAs are present in grass-fed animals?
Long-chain n-3 polyunsaturated FAs
What are the 5 fat depots in an animal?
Intermuscular (seam fat)
Body cavity (perirenal, vascular, carcass)
What are the 2 form of carbs?
What are the 2 main minerals?
Zinc - wound healing, immunity, DNA synth
Importan points about Conjugated Linoleic Acid
Mix of linoleic acid positional & geometric isomers
C9, t11 most common
Precursor to stearic acid
^ linoleic acid in diet = ^ CLA in meat
1. Myofilament - thick & thin filaments
2. Myofibril - sarcoplasmic reticulum
3. Muscle fibre - endomysium
4. Muscle fibre bundle / Fascicles - perimysium
5. Muscle - epimysium
1. Thick filament
2. Thin filament
3. Z disc
4. I band
5. A band
6. H zone
7. M line
What is the basic structure of myosin?
2 globular heads
1 alpha-helical tail
When does myosin hydrolyze ATP to ADP?
In the presence of Mg
What does myosin bind to?
What are the 2 light chain types of myosin?
ELC - essential light chain, essential for binding to actin
RLC - regulatory light chain, non-essential, phosphorylated
What drives the formation of thick filament?
Tail region of myosin
What are the 2 most abundant myofibrillar proteins?
What are the 2 forms of actin?
Globular (G) - in low salt more attracted to water than self so forms individual units
Filamentous (F) - in physiological salt, in muscle
What is the structure of F actin?
Helix of actin molecules, looks like string of pearls twisted on itself
1. Myosin binds to actin
1a. Inorganic phosphate released
2. Ca from nerve impulse, myosin swivels on actin, pulls thin/thick fils past e/o, POWER STROKE
2a. ADP released
3. No ATP, myosin & actin bound, RIGOR
3a. ATP added
4. Actin detaches
4a. ATP hydrolyzed
5. Close to e/o, myosin head cocked, REST
3. Troponin complex
What are the 3 troponin complexes?
TnI - binds to actin
TnC - binds to Ca ions
TnT - binds to tropomyosin
What is the relationship between Ca, TnC, tropomyosin, and a power stroke?
Ca binds to TnC
Tropomyosin has less affinity for actin, moves out of the way
Myosin binds to actin
What are the 2 types of Ca binding sites on TnC and which is responsible for a power stroke?
Low affinity - power stroke, allows easy release
What is like a line-dance at a wedding? Why?
Mitochondria/nuclei = feed protein synthesis, tables along outer wall of dance floor, move out of the way for the line-dance
Filament movement = line-dance
Na-K pump ratio
3 Na out
: 2 K in
Returns to original location via diffusion
Resting mem potential
-85 to -90 mV
What happens to mem potential as nerve impulse travels down axon?
Depolarization - Na flow in
Repolarization - K flow out
Impulse reaches voltage gated channels
Returns to Na/K pump
How many neuromuscular junctions are there per muscle fiber and where are they located?
Mid-secion of each muscle fiber, outside plasma mem
What are DHPRs and where are they located?
Transverse tubule mem
What effect does an action potential have on DHPR?
Triggers release of Ca from Ryr1 in SR
Where is Ryr1 located?
Junctional region of SR mem
What is Ryr1 and what role does it play?
Controls release of Ca that causes muscle contraction
How does transverse tubule depolarization effect Ca release?
Triggers DHPR to change conformation
This triggers Ryr1 linked to DHPR to release Ca
Ca triggers release of Ca from Ryr1 not linked to DHPR
What are the main properties of Calsequestrin?
Binds releasable Ca, high capacity
Random conformation, becomes helical as Ca binds
Low ionic strength - inhibits Ryr1
High ionic strength - increased Ryr1 activity
How is Ca retrieved from the sarcoplasm?
Facilitated by dense coverage of SR by ATPase
Muscle contracts but does not shorten
Muscle contracts and shortens, tension remains constant
How does the Ca
-ATPase pump work?
Mg-ATP binds to ATPase
ATPase changes conformation
bind to ATPase
ATPase changes conformation
Ca released to SR lumen