exam 3

Question 1

Types of lipids:

Answer 1

Hydrolysable ((simple as waxes and TAG) or complex as phospholipids and sphingolipids), and non hydrolysable (steroids, eicosanoids and lipid soluble vitamins)

Question 2

Properties and functions of lipids:

Answer 2

Have more energy than other nutrients, are insoluble in water but soluble in solvent, classified as hydrolizable or non hydrolyzable.

used as energy storage, thermal insulator, electrical insulator, as signaling molecule, as membrane component (cholesterol, phospholipids etc)

Question 3

Role of insulin:

Answer 3

normally only B cells are permeable to glucose, insulin increases cell permeability to glucose increasing transport in the cell recruiting glucose transporters as GLUT4, inhibits glycogenolysis and gluconeogenesis and stimulates synthesis of glycogen and FA (stimulates pyruvate dehydrogenase, acetyl coa carboxylase). Contrary to glucagon

Question 4

CLA effect for pigs:

Answer 4

alters composition (decrease fat), increase deposition of saturated fat (causing firmer bellies), improves feed conversion and is anti-inflammatory,
CLA inhibits lipogenesis by inhibiting acetyl coa carboxylase and fatty acid synthase, and decreases stearyl coa desaturase that converts stearic to oleic acid, thus increasing level of saturation

Question 5

Amino acids and their metabolites:
Norepinephrine
Carnitine
Melatonin
Melanin
Tyrosine
Serotonin
Urea
Glutamine
Nicotinic acid

Answer 5

AA Product
tyr Norepinephrine
Lys, met Carnitine
Trp Melatonin
Tyr Melanin
Phe Tyrosine
Trp Serotonin
Asp, arg urea
Glu Glutamine
Trp Nicotinic acid

Question 6

Two types of rancidity:

Answer 6

hydrolytic (hydrolysis from microbial lipase action, causes removal of 1 or more FA causing an impact in flavor. E.g. butter butyric acid is released and gives foul odor, may affect nutritional value)

Oxidative: occurs in TAG that has polyunsaturated FA, free radicals released may damage cell membrane, cause inflammation, antioxidants are added to prevent it. May alter nutritional value and cause odor

Question 7

Cite Antioxidants

Answer 7

naturally occurring: vitamin E, C and selenium
Synthetic: BHT (butylated hydroxy toluene), BHA (butylated hydroxy anisole), propyl gallate.

Question 8

Which reactions in glycolysis cannot be reversed and which enzymes are used instead in gluconeogenesis?

Answer 8

Hexokinase, PFK and pyruvate kinase. in gluconeogensis glucose 6 phosphatase, fructose 1,6 bisphosphatase, pyruvate carboxylase and Phosphoenolpyruvate (PEP) carboxykinase, respectively

Question 9

Where does the N in urea comes from?

Answer 9

Free amonia and aspartate

Question 10

Beta oxidation steps

Answer 10

Activated into acyl via by acyl coa synthetase
Exchanged for Carnitine into mitochondria
Odd number FA: last FA is released as propionyl coa then converted into succinyl coa, spending 2 ATP by propionyl coa carboxylase