fish pt 2 Flashcards
how many layers comprise the skin of fish?
2
describe the layers of fish skin
- outer epidermis: outermost membrane, high moisture content, interspersed with several gland cells that produce mucopolysaccharides that serve as a defense mechanism for fish
- inner dermis = innermost membrane, comprised of connective tissue material with several pigmented cells
list some pigments that fish can have in their inner dermis
- melanophores = brownish
- erythrophores = reddish
- xanthophores = yellow
- iridiophores/guanophores = metallic/silvery
describe the scales of a fish
ring-like shingles that emanate from the base of the dermis and traverse the outermost layer
what’s the lateral line?
comprised of scales arranged laterally in middle of fish skin that has secretory and nerve cells that enable the fish to sense changes in its environment (temp, pressure, salinity)
what’s the shape of true fishes?
like a torpedo, round at the head, wider in the middle, tapered at the head
what’s the use of fins?
help with swimming (turning/locomotion)
what do scales do?
secrete mucous as a defense mechanism
what type of lipids are there in fish?
- phospholipids (structural) forms part of membranes
- triglycerides (storage) distributed in different parts of the fish
where can you find fat deposits in a fish?
- muscles
- liver
- intestines
distinguish between a fatty and lean fish
fatty has TGs deposited in their muscle, lean has TGs deposited mainly in their intestines or in the liver
list some examples of fatty fish
- carb
- herring
- mackerel
- salmon
- troug
list some examples of lean fish
liver: cod & haddock
intestines: pike, porgy
true or false: fish are more susceptible to oxidative rancidity because of their PUFA content
true
what types of proteins exist in fish?
- sarcoplasmic (20-30%)
- myofibrillar (65-75%)
- connective tissue (3-10%)
why would different animals have similar levels of sarcoplasmic proteins?
these participate in metabolic processes, and the organisms all have the same metabolic requirements and therefore require the same enzymes/pigments to function.
describe sarcoplasmic proteins
- water soluble
- globular in shape
- mostly enzymes and pigments (Mb, Hb)
why do poultry/mammals have less myofibrillar proteins than fish?
fish are actively swimming to travel through a medium that has greater resistance, especially when travelling counter-current, so more muscle is necessary to carry out the function of locomotion
list examples of myofibrillar proteins
- myosin
- actin
- troponin
- tropomyosin
why is the connective tissue protein in fish lower than in protein?
- fish have fewer bones
- the aqueous environment provides more support for fish than for land mammals/birds
fish tend to be (more tender/tougher) than mammals/poultry because of (higher/lower) connective tissue protein content
more tender; lower
what’s the shrinkage temperature?
temperature at which proteins begin to shrink due to heating
the shrinkage temperature for fish is (high/lower) than for mammals/birds. why?
lower, because there is less connective tissue content
fish proteins are (more/less) heat resistant than mammal/poultry proteins
less
why are fish easier to break down from proteolytic enzymes
connective tissue proteins (collagen/elastin) are more resistant to proteolysis; having less of these makes fish easier to break down
true or false: fish are considered a source of high quality protein
true - they contain all essential amino acids
what are protamines?
high basic amino acid content; can react with components of bacterial cell walls that provide an antimicrobial capacity
describe the CHO content of fish
- low CHO
- mainly glycogen (0.3-0.5%)
- generally found in muscle
- fish draws on glycogen stores for energy as needed
what vitamins are fish/shellfish rich in?
B vitamins, A, and D
what minerals are fish rich in ?
I, Se, K, P, Mg
