Lipids Flashcards
What are lipids composed of?
Carbon, hydrogen, oxygen
How percentage of diet should be fat?
30%
Less than 9% saturated
Less than 1% trans
What does hydrophobic and hydrophilic mean?
Hydrophobic - avoids water (most lipids)
Hydrophilic - soluble
What are fatty acids biological composition?
Fats are an organic acid, with a carbon backbone
Chain of carbon and hydrogen atoms and an acid group (COOH) at one end, and a methyl group (CH3) at the other
What is the difference between a small and long carbon chain?
small - 6-10 carbon bonds, primarily in diary
Med/large - 12/24, in meats, fish
What is the omega end and what is the alpha end?
Omega end - methyl group (CH3)
Alpha end - carboxyl acid (-COOH)
What is a triglyceride?
Lipids composed of three fatty acids attached to glycerol.
Condensation reactions must occur to combine hydrogen atom (from glycerol) and hydroxyl group (from fatty acid) - forms water molecule and bond between other two molecules.
Most contain more than one type of fatty acid
What is a saturated fat?
Fat that is fully loaded with hydrogen bonds
What is an unsaturated fat?
A fat with missing hydrogen bonds
What is the difference between monounsaturated and polyunsatured?
mono - one double bond
Poly - more than one double bond
(Also triple bonds)
What is the difference between Trans and cis unsaturated fat?
Trans - H atoms opposite sides. (Chain is straight - solid at room temp)
Cis - H atoms same side (bent configuration - liquid at room temp)
What are some characteristics of solid fats and oils?
Firmness - shorter the carbon chain, the softer far is at room temp
Stability - oxidation of fats spoils them, saturated fats most resistant to oxidation
Hydrogenation - unsaturated fats become saturated (adds H)
What are phospholipids?
2 fatty acids joined to a glycerol backbone.
Lecithin (eggs, liver, soybeans, wheat germ)
Used as emulsifiers - fat suspended in blood/body fluids
Soluble in water/fat - helps fat-soluble substances (vitamins, hormones) pass easily in and out of cells.
Hydrophilic head and hydrophobic body
What are sterols?
Compounds with a multiple ring structure
Cholesterol!! Cannot be used for energy - body’s make 75% of it (endogenous)
Found in bile acids, sex hormones, vitamin D
Serves at starting material/structural component of cell membranes
Is cholesterol essential in the diet?
No, nearly all cells are capable of synthesising cholesterol
What is the goal of lipid digestion?
To dismantle triglycerides into monoglycerides, so the body can absorb
What are the three main processes of lipid digestion?
Mouth - linguinal lipase
Stomach - gastric lipase, HCI acid
Small intestine - CCK, bile
How is fat digested in the intestine?
When fat enters SI, triggers release from duodenal cells of hormone cholecystokinin, which signals to gall bladder to release bile
How do micelles work?
bile emulsifies fat in GI tract, breaking it into smaller droplets
Bile surrounds fat, forms it into micelles - transport fats to the intestinal wall for absorption
How are lipids absorbed?
Small molecules easily diffuse into intestinal cells
Larger micelles diffuse into intestinal cells, where they are reassembled, packed with protein into transport vehicles known as chylomicrons
Released into lymphatic system
Glides through lymph, entry into bloodstream at thoracic duct near heart
What do lipoproteins do?
transports fat through watery bloodstream
Makes 4 types (size, dense)
More lipids - less dense
More proteins - denser
What are chylomicrons?
largest/densest lipoproteins, transports diet-derived lipids
Cells over body remove triglycerides from them as they pass
What are VLDL?
Very low density Iipoproteins
Cells in liver synthesise cholesterol, fatty acids and other lipid compounds
What is the difference between LDL and HDL?
LDL - low density lipoproteins, ‘bad’ cholesterols
HDL - high density lipoproteins, ‘good’ cholesterol
Factors that lower LDL/raise HDL:
Weight control
Monounsaturated, polyunsaturated fat
Soluble dietary fibres
Phytochemicals
Moderate alcohol consumption
Physical activity
What are the roles of triglycerides?
provide energy
Insulate against temp
Protect against shock
Maintain cell membranes
Vital to produce compounds - hormones, absorb vitamins, etc
What is adipose tissue?
storage for fat, secretes hormone adipokines, proteins that regulate energy balance
How many essential fatty acids are there?
9
Must be supplied by diet
What is the linoleic acid?
Primary member of omega-6 family
Pro-inflammatory
Body makes other members from omega-6 with this from diet
In meat, vegetable oils
What is lenolenic acid?
primary member of omega-3 family
Anti inflammatory
Found in eyes, brain
Essential for growth, vision, cognitive development
What are eicosanoids?
Made of arachiodonic acid and eicosapentaenoic acid (EPA)
Diverse - more than 100 compounds ity response
Omega 3 - reduce inflammation
Omega 6 - blood clots
what are phytosteols?
present in high concentration in unrefined vegetable oils (sitosteol, camperterol)
Plant sterols - lower blood cholesterol
What can occur with fatty acid deficiencies?
growth retardation
Reproductive failure
Skin lesions
Kidney and liver disorders
Subtle neurological and visual problems
How is fat stored as fat?
When meal delivers more energy than body needs, excess stored as fat in adipose cells for later use
LPL enzyme hydrolyses triglycerides from circulating lipoproteins, releasing fatty acids, di/monoglycerides into adipose cells
Accumulation of fat in adipose tissue allows humans to survive when food is unavailable
How is fat used for energy?
Fat supplies 60% of body’s energy needs during rest
During energy deprivation, hormone-sensitive lipase enzymes dismantle stored triglycerides and release glycerol and fatty acids directly into blood
What happens when you eat fat without carbs?
Fats break down to ketone bodies.
What are the health effects of saturated fats?
increased risk of heart disease, obesity, cancer
Promotes blood clotting
What are some ways to reduce fat intake?
Trimming fat, grass fed, soy protein
Eggs, flaxseed, fish oil
Fat free/low fat
Fermented yoghurt
Avocados, olives
What are fat replaces?
ingredients that provide taste/texture of fats, with fewer kJ
Thickeners, stabiliser, emulsifiers, olestra
