fish pt 2

Question 1

how many layers comprise the skin of fish?

Answer 1

2

Question 2

describe the layers of fish skin

Answer 2

• 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

Question 3

list some pigments that fish can have in their inner dermis

Answer 3

• melanophores = brownish
• erythrophores = reddish
• xanthophores = yellow
• iridiophores/guanophores = metallic/silvery

Question 4

describe the scales of a fish

Answer 4

ring-like shingles that emanate from the base of the dermis and traverse the outermost layer

Question 5

what’s the lateral line?

Answer 5

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)

Question 6

what’s the shape of true fishes?

Answer 6

like a torpedo, round at the head, wider in the middle, tapered at the head

Question 7

what’s the use of fins?

Answer 7

help with swimming (turning/locomotion)

Question 8

what do scales do?

Answer 8

secrete mucous as a defense mechanism

Question 9

what type of lipids are there in fish?

Answer 9

• phospholipids (structural) forms part of membranes

- triglycerides (storage) distributed in different parts of the fish

Question 10

where can you find fat deposits in a fish?

Answer 10

• muscles
• liver
• intestines

Question 11

distinguish between a fatty and lean fish

Answer 11

fatty has TGs deposited in their muscle, lean has TGs deposited mainly in their intestines or in the liver

Question 12

list some examples of fatty fish

Answer 12

• carb
• herring
• mackerel
• salmon
• troug

Question 13

list some examples of lean fish

Answer 13

liver: cod & haddock
intestines: pike, porgy

Question 14

true or false: fish are more susceptible to oxidative rancidity because of their PUFA content

Answer 14

true

Question 15

what types of proteins exist in fish?

Answer 15

• sarcoplasmic (20-30%)
• myofibrillar (65-75%)
• connective tissue (3-10%)

Question 16

why would different animals have similar levels of sarcoplasmic proteins?

Answer 16

these participate in metabolic processes, and the organisms all have the same metabolic requirements and therefore require the same enzymes/pigments to function.

Question 17

describe sarcoplasmic proteins

Answer 17

• water soluble
• globular in shape
• mostly enzymes and pigments (Mb, Hb)

Question 18

why do poultry/mammals have less myofibrillar proteins than fish?

Answer 18

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

Question 19

list examples of myofibrillar proteins

Answer 19

• myosin
• actin
• troponin
• tropomyosin

Question 20

why is the connective tissue protein in fish lower than in protein?

Answer 20

• fish have fewer bones

- the aqueous environment provides more support for fish than for land mammals/birds

Question 21

fish tend to be (more tender/tougher) than mammals/poultry because of (higher/lower) connective tissue protein content

Answer 21

more tender; lower

Question 22

what’s the shrinkage temperature?

Answer 22

temperature at which proteins begin to shrink due to heating

Question 23

the shrinkage temperature for fish is (high/lower) than for mammals/birds. why?

Answer 23

lower, because there is less connective tissue content

Question 24

fish proteins are (more/less) heat resistant than mammal/poultry proteins

Answer 24

less

Question 25

why are fish easier to break down from proteolytic enzymes

Answer 25

connective tissue proteins (collagen/elastin) are more resistant to proteolysis; having less of these makes fish easier to break down

Question 26

true or false: fish are considered a source of high quality protein

Answer 26

true - they contain all essential amino acids

Question 27

what are protamines?

Answer 27

high basic amino acid content; can react with components of bacterial cell walls that provide an antimicrobial capacity

Question 28

describe the CHO content of fish

Answer 28

• low CHO
• mainly glycogen (0.3-0.5%)
• generally found in muscle
• fish draws on glycogen stores for energy as needed

Question 29

what vitamins are fish/shellfish rich in?

Answer 29

B vitamins, A, and D

Question 30

what minerals are fish rich in ?

Answer 30

I, Se, K, P, Mg