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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?
- Triglycerides (marbling)
- Phospholipids (mems)
- Glycolipids (nerves)
- Cholesterol (mems, fluidity, sex hormones)
What are the 5 principal phospholipids?
- Phosphatidyl choline
- Phosphatidyl ethanolamine
- Phosphatidyl inositol
- Diphosphotidyl glycerol
- Phosphatidyl serine
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)
- Intramuscular (marbling)
- Cell mems
- Body cavity (perirenal, vascular, carcass)
What are the 2 form of carbs?
- Glycogen/Lactic acid
What are the 2 main minerals?
- Heme iron
- Zinc - wound healing, immunity, DNA synth
Importan points about Conjugated Linoleic Acid
- Mix of linoleic acid positional & geometric isomers
- Anti-cancer properties
- 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?
- 6 subunits
- 2 globular heads
- 1 alpha-helical tail
When does myosin hydrolyze ATP to ADP?
In the presence of Mg2+
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
- 1. Actin
- 2. Tropomyosin
- 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
- Power stroke
What are the 2 types of Ca binding sites on TnC and which is responsible for a power stroke?
- High affinity
- Low affinity - power stroke, allows easy release
What is like a line-dance at a wedding? Why?
- Myofibrillar structure
- 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?
- Dihydropyridine receptors
- Transverse tubule mem
What effect does an action potential have on DHPR?
- Changes conformation
- 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?
- Ryanodine receptor
- 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?
- In SR
- 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?
- Mg2+, Ca2+-ATPase
- Facilitated by dense coverage of SR by ATPase
Muscle contracts but does not shorten
Muscle contracts and shortens, tension remains constant
How does the Ca2+-ATPase pump work?
- Mg-ATP binds to ATPase
- ATPase changes conformation
- 2 Ca2+ bind to ATPase
- ATP hydrolyzed
- ATPase changes conformation
- Ca released to SR lumen