Meat Science Exam 3

70-75

percentage of water in meat

20-25

percentage of proteins in meat

1-6

percentage of lipids in meat

1

percentage of carbohydrates in meat

1

percentage of inorganic constituents in meat

sarcoplasmic, myofibrillar, stromal

three groups of muscle proteins

25-30

what percentage of proteins are sarcoplasmic?

sarcoplasmic proteins

proteins that are water soluble and make up enzymes and myoglobin

50-60

what percentage of proteins are myofibrillar proteins?

myofibrillar proteins

proteins that are salt soluble and make up actin and myosin

10-20

what percentage of proteins are stromal proteins?

stromal proteins

proteins that are insoluble and make up collagen and elastin (connective tissue)

30-40%

how much of a animal’s body mass does muscle make up?

movement, support, maintenance of body temperature, dietary protein source

primary function of muscle

epimysium

connective tissue that surrounds skeletal muscles

muscle fascicle/bundle

makes up skeletal muscle and is surrounded by the perimysium and is made up of muscle fibers

perimysium

connective tissue that surrounds muscle fascicle/bundles

muscle cell (fiber)

makes up muscle bundles, is surrounded by the endomysium, and contain myofibrils

endomysium

connective tissue that surround muscle cells (fibers)

myofibril

makes up muscle cells and consists of sarcomeres, surrounded by the SR

sarcomeres

contractile unit of muscle and makes up myofibrils

the perimysium

where is marbling located in meat?

tropocollagen

structural unit of a collagen fibril

hydroxyproline

unique peptide to collagen

glycine, proline, hydroxyproline

peptides that make up collagen

tropocollagen molecule

a triple helix consisting of three polypeptide chains

forms stable cross links which make meat tougher

what happens to collagen as an animal ages?

more tender

less collagen makes meat…

elastin

rubbery protein that is abundant in structures that require the ability to stretch

desmosine and isodesmosine

unique amino acids of elastin

elastin

is elastin or collagen more stable?

myofiber

muscle cell=

sarcolemma

muscle cell membrane

sarcoplasm

cytoplasm if muscle cell

mitochondria

powerhouse of the cell

multi

muscle cells are ___ nucleated

sarcoplasmic reticulum and transverse tubules

highly developed ER, unique to muscle cells

sarcoplasmic reticulum (SR)

membrane around the myofibril, sits under endomysium, stores Ca in relaxed muscles

transverse tubules (t-tubules)

invagination of the sarcolemma that form a “communication channel” into the interior of a muscle fiber

A band

darker band of sarcomere consisting of myosin and actin overlap

I band

lighter band of sarcomere consisting of majority actin

Z line

dense, thin line bisecting the I band

one sarcomere

one z line to another z line

H zone

lighter band within the dark A band consisting of only myosin

M line

very thin, dark line within the H zone; important structurally

contractile, regulatory, structural/cytoskeletal

major proteins in myofibril

myosin, actin

contractile proteins

troponin, tropomyosin

regulatory proteins

⍺ actinin, titin, nebulin, myomesin, desmin

structural/cytoskeletal proteins

myosin

70-80% of the myofibrillar protein, burns ATP, head performs muscle contraction

actin

20-25% of the myofibrillar protein, globular protein, arranged like a twisted pearl necklace

thin filaments

composed of super helix of f-actin, troponin and tropomyosin

g-actin

globule protein, single units of actin

f-actin

chain of actin, makes up the filament

tropomyosin and troponin

regulatory proteins

tropomyosin

thin protein that lays around the actin proteins

troponin

regulatory protein comprised of 3 subunits and works to bind to Ca and expose myosin binding sites

troponin t

subunit of troponin that is bound to tropomyosin

troponin c

subunit of troponin that binds to Ca

troponin I

inhibitory subunit that prevents interaction between actin and myosin (inhibits muscle contraction by pushing tropomyosin back over binding sites)

z line

part of sarcomere that is composed of alpha actinin and anchors thin filaments

titin

largest protein discovered, extends from z line to m line, attaches thick filaments to z line, acts as molecular spring

z filaments, titin, nebulin

regulatory proteins

nebulin

structural protein that originates at z line and extends along thin filaments (string of beaded necklace)

acetylcholine

chemical that is released into synaptic cleft to depolarize sarcolemma and begin muscle contraction

sarcoplasmic reticulum to release Ca into the cytosol

what does depolarization of the sarcolemma cause?

Na fluxes in, K leaves (depolarization)

what does ACH binding to sarcolemma cause?

neuromuscular junction

motor end plate where action potentials from neurons reaches muscle receptors

via the t tubules

how is the action potential transmitted to the SR?

myosin ATPase

enzyme that breaks ATP into ADP

to disconnect cross bridge

what is ATP needed for?

type I muscle

muscle with high myoglobin content, slow contraction speed, small diameter, high oxidative metabolism, and greater lipid content

type IIa

muscle with moderate myoglobin content, moderate contraction speed, small fiber diameter, moderate lipid content, and moderate oxidative metabolism (still uses anerobic pathways)

type IIx

muscle with low myoglobin content, moderate fiber diameter, moderate contraction speed, moderate glycogen and glycolytic activity, and low lipid content

type IIB

muscle with low myoglobin content, large fiber diameter, fast contraction speeds, high glycogen content and glycolytic metabolism and very little lipid content

type I

muscle that is for slow speed

type IIB

muscle that is very fast

type I

muscle that relies on oxidative metabolism

type IIB

muscle that relys on glycolytic metabolism

lactate

without oxygen, pyruvate becomes…

ATP (eventually)

with oxygen, pyruvate becomes…

lactic acid

lactage + H

accumulation of H ions

what causes the decline of muscle pH

delay, onset, completion, resolution

phases of rigor mortis

delay phase

phase of rigor mortis which muscle remains extensible and elastic

onset phase

phase of rigor mortis which muscle begins to lose extensibility

completion phase

phase of rigor mortis which ATP is depleted and muscle is inextensible

rigor mortis

when CP and glycogen stores have been exhausted and muscle slowly depletes ATP forming permanent actomyosin cross-bridges; results in loss of extensibility and muscle shortening

15-20 C

optimal rigor temperature for minimal sarcomere shortening

cold shortening

this happens which muscles are chilled to temperatures below 15 C while ATP is still present

electrical stimulation

what can you do to prevent cold shortening?

aging

refrigeration of meat for a fixed amount of time to improve tenderness

resolution of rigor

4th state of rigor mortis that is the breakdown of things cuasing rigor

actin-myosin bonds weaken, enzymatic degradation of structural proteins, weakened perimysium and endomysium

changes during postmortem aging that improve tenderness

calpain protease system

group of enzymes that break down proteins that are dependent on Ca for activity

desmin, titin, nebulin, costameres

calpains degrade…

desmin

intermediate filaments that link myofibrils to one another

releases it from z line

what does calpains do to alpha actinin?

costameres

group of proteins that help maintain structure (linkage of myofibrils to sarcolemma)

no

are actin and myosin bonds influenced by calpains?