Adipose Tissue Flashcards
Adipose tissue (fat cells)
Connective tissue cells those are specialized for storage of neutral lipids
Store energy in the form of triglycerides
Gradually accumulate cytoplasmic fat which push nucleus to the periphery of the cell
Synthesize hormones such as leptin
Types of fat stored: triglycerides
Glycerol back bone with 3 fatty acid chains
Fatty acids can be identical or different
Stored in cytosol of adipocytes
Carbon atoms are more reduced (less oxygenated) in fat them sugars → thus provide more energy than carbohydrates
ESTER bond
The bond that forms between the glycerol and the fatty acids
Adipose tissue types
Brown fat
white fat
Brown fat
Thermogenesis: energy expenditure
Commonly seen in hibernating animals, embryo and newborns highest at birth)
Express UPC1
White fat
Energy storage
Develops after birth
Do not express UPC1
Aerobic respiration
Stage 1: glycolysis
Stage 2: link reaction (occurs in mitochondria): links glycolysis with Stage 3TCA
Stage 3: citric acid cycle /Kreb’s cycle/TCA occurs in mitochondrial matrix)
Stage 4: electron transport chain (ETA) occurs in inner membrane of mitochondrial matrix
Fatty acid composition
Saturated fatty acids
Monounsaturated fatty acids (mufa)
Polyunsaturated fatty acids (pufa)
Why vegetable oil is liquid but not animal fat at room temp
Fat molecules are mostly made up of long, straight hydrocarbon chains. Hence they pack neatly with their neighbors
To form a solid, molecules need to pack together nicely
In liquid state the molecules flow around eachother and there is less order
Oils generally have chains which are kinked (because of a double bond), this stops them interacting so tightly with each other and so they stay liquid
White adipose tissue function
Energy storage (lipid)
Reduce heat loss by insulation (subcutaneous fat)
Protection of internal organ (abdominal fat) by cushioning
Sources of metabolic water
Fat soluble vitamin storage
Animal seal
Secrete enzyme like leptin, adiponectin, resistin, etc.
Adipose as insulator
Adipose poor insulator
Reduce heat loss through limited surface blood flow
Adipocytes are able to maintain homeostasis with limited Blood flow
Animal form
Provides functioned shape to animals (seal, penguins)
Provides protection of organs against trama
Metabolic water
Water produced with metabolism of substrate
The camel hump myth
Fat is a very poor source of water
Adipose tissue as an endocrine organ
Leptin → control of food intake and energy expenditure, lipogenesis, improves insulin sensitivity
Adiponectin → increases sensitivity to insulin, decreases hepatic gluconeogenesis)
Resistin → inhibits adipocytes differentiation, heightens resistance to insulin
Interleukin - 6 → anti-inflammatory function
Adipogenesis during embryogenesis
Adipose tissue formation preceded by capillaries and connective tissue
Second half to final 3rd of gestation
Adipocyte growth hyperplastic
Little lipid contained in white adipocytes during gestation and at birth
Brown adipocytes form first and have most lipid in triglyceride form)
Pre-adipocyte proliferation encouraged by IGF -1 at late gestation
Adipose tissue depots (4 major)
1→ visceral (mid gestation in cattle)
2 → inter-muscular (seam fat) (early weaning in cattle)
3 → subcutaneous (back fat → waste fat) ( early weaning stage in cattle)
4→ intra-muscular (marbling-taste fat) around 250 days of age in cattle
Visceral fat
Mesenteric fat → located around the intestines
Caul Fat → Thin sheet of a dipole tissue contained in a large fold of connective tissue over the stomach and adjacent organs
Peri-renal or kidney fat → protective fat around the kidney
Lean fat → located between the lining of the thoracic cavity and the ribs in mammalian meat animals
Subcutaneous fat
Located just under the skink hide
Also referred to as “back fat”
Largest depot Of fat in pork carcasses
Outer layer → acts as insulation for animals (first to develop)
Middle layer → most metabolically active, normally thickest postnatally ( second to develop)
Inner layer → small and thin, difficult to defect in lean animals (last to develop)
Inter-muscular fat
Located around and in between individual muscles or groups of muscles
Also called “SEAM FAT”
Associated with the epimysium of muscles
Development of subcutaneous and intermuscular depots may be interchangeable
Intra-muscular fat (marbling)
Intramuscular fat includes lipids from adipose cells in the muscle (marbling) and membrane-bound lipids
However, in red meat, the term “intramuscular fat” normally denotes marbling
This is the last fat depot to form and is called marbling
Marbling is deposited more slowly and continuously throughout the life of the animal
Associated with the Perimysium that surrounds muscle fiber bundles/fascicles
Related to the eating qualify of beef
Contains high level of PUFA and MUFA compared to other beef fat depots
Contains more oleic acid and less stearic acid than subcutaneous adipose which has a positive health aspect
What does marbling do?
Juiciness, flavor, tenderness, and it keeps the meat moist during cooking, so natural juices don’t evaporate in the pan
Lubrication theory
Fat melts during heating causes a lubrication effect around the muscle fibers which make it easier to bite through → as the menu fat that melts the juicer the steak will be
Bulk density theory
Fat is less dense than lean tissues which causes soft pockets → the more fat within the muscle, the easier it will be to bite through
Insulation theory
More fat within the lean portions, the steak will be more protected from heat during cooking therefore it is less likely to be overcooked
Strain theory
The strength of intramuscular connective tissue may be decreased by the deposition of intra-muscular fat → fat loosen the structure of the connective tissue fibers enough to aid in heat penetration
Why grain feeding is necessary during finishing for marbling development in beef?
High-energy grain rations with corn or grain sorghum lead to produce more propionate which is used by the lover for glucose production and glucose is preferred substrate for intramuscular fat (marbling) in ruminants
