Midterm 2 Flashcards
(86 cards)
What are lipids and the groups?
- Large class of organic molecules that are not soluble in water
- Contribute to texture, taste, flavour and aroma of foods
- 1 g of lipid yields 9 kcal of energy
- Fatty acids (long hydrophobia chains of carbon and hydrogen)
- Triglycerides (usually what we’re talking about when we say “fat” such as beef)
- Phospholipids
- Sterols
What are triglycerides?
- 85% of dietary lipid
- We eat triglycerides and we store our body fat as triglycerides
- Made of 1 glycerol molecule “backbone” with 3 fatty acids
What are phospholipids?
- Has a hydrophilic and hydrophobic end
- Form a lipid bilayer in cell membrane
- Maintenance of membrane integrity; regulates what passes in and out
- If there is too much saturated fat in the diet, the structure of cell membrane can change
- Made of glycerol as a backbone with 2 fatty acids
In place of a 3rd fatty acid is a phosphate group attached to a variety of other molecules (eg. lecithin in milk, eggs, lightly cooked meats, wheat germ) - Eg. egg yolk, fish, milk, beef
What are sterols?
- Large group of hydrophobic compounds found in plants and animals
- Most common in animals (eg. cholesterol)
- 90% of cholesterol in body is found in cell membranes
- Cholesterol is needed to make sex hormones and myelin sheath (insulating material on every nerve in the body)
- Too much LDL is a cardiovascular risk factor
How does length of fatty acids affect fat?
Affects how fat is digested and metabolized in body
- Short chain fatty acids: fewer than 8 C atoms
- Medium chain fatty acids: 8-12 C atoms (eg. lauric acid)
- Long chain fatty acids: 13+ C atoms
How does saturation level of fatty acids affect fat?
Affects properties at room temperature, how fat is processed in the body and their effects on the metabolism of nutrients
- Saturated: no double bonds between C atoms
- Long, straight chain
- Animal fats and tropical oils (eg. palmitic and stearic acid in meat/dairy, coconut oil)
- Have longer shelf life and are more stable - Unsaturated: 1+ double bonds between C atoms
- Monounsaturated (MUFA): 1 double bond (eg. oleic acid)
- Plant based (eg. olive oil, table olives, avocado, canola oil)
- Liquid at room temperature - Polyunsaturated (PUFA): 2+ double bonds (eg. linoleic acid and linolenic acid)
- Liquid at room temperature; the more unsaturated bonds the more liquid they are
- Mostly plant based (eg. soybean oil, safflower oil, corn oil, fish, nuts and seeds)
How does configuration of double bond of fatty acids affect fat? Discuss hydrogenation.
- Cis
- Most fatty acids have the cis configuration
- H molecules on same side rather than opposite side of double bond - Trans
- Have higher melting point and more shelf stable
- Favoured by food industry, found on nutrition labels
- Trans fat raise blood cholesterol levels and increase risk of heart disease
- Occurs naturally in meat and dairy or in partially-hydrogenated fats (eg. margarine, crisco, processed peanut butter)
HYDROGENATION:
- Some/all of double bonds in oil accept hydrogen and become saturated
- Fully hydrogenated oils are considered more like saturated fats (increased stability against rancidity and higher melting point = solid)
- Trans fatty acids are in partially hydrogenated oils (some bonds remain unsaturated and shift to trans configuration)
Discuss the location of double bonds and fatty acids.
- Where the double bonds are will change physical structure of fatty acids
- Double bond is a C-C bond with methyl (CH3) aka the omega (ω) end and the alpha end (acid)
- Position is relative to the ω end of the molecule
- Affects how our body metabolizes fatty acid
- Ratio of omega-3 to omega-6 (proinflammatory) is important for the health
- Omega-3 fatty acids: double bond between 3rd and 4th C from ω end (eg. alpha-linolenic acid; a polyunsaturated fatty acid)
- Omega-6 fatty acids: double bond between 6th and 7th carbons from ω end (eg. linoleic acid; a polyunsaturated fatty acid)
- Omega-9 fatty acids: double bond between 9th and 10th carbon from ω end (eg. oleic acid; a monounsatured fatty acid)
Discuss nomenclature of fatty acids.
Fatty acids are given common names and numerical notation
Eg. 18:2 ω-6 (Linoleic acid numerical name)
18 = number of carbon atoms
2 = number of double bonds
ω-6: where the first bond is from the omega end
Discuss fat digestion.
- Mouth
- Chewing and lingual lipase begins to do some digestion
- Important for babies who do not have full set of digestive enzymes in small intestine to break off fats - Stomach
- Churning into small droplets and gastric lipase
- Mainly proteins get digested here because it is acidic - Small intestine (majority of fat digestion)
- Pancreatic lipases break fatty acids off glycerol to form free fatty acids and monoglycerides/monoacylglycerols
- Bile from gallbladder emulsifies fat into smaller droplets called micelles
- Allows products of fat digestion to get close to brush border, where there is access to lymph system
- Very little fat lose in stool; most is absorbed otherwise problem
How is fat absorbed?
- The products of triglyceride digestion (cholesterol, esters, monoglycerol, free fatty acids and fat soluble vitamins) mix with bile to form micelles
- Nutrients move through the blood made of water
- Lipoproteins allow fat to mix with blood
Discuss lipoproteins in the blood stream.
- Membrane made of protein and phospholipids
- Phospholipids are on outside = hydrophilic and can float easily through blood stream
- Chylomicrons: type of lipoprotein made in cells of small intestine to bring fat closer to brush border
- Carries dietary fat to the liver and rest of the body for burning or storage
Other types of lipoproteins are made in the liver
- Once chylomicrons arrive at liver, disassembled into very low density lipoproteins (VLDL)
- Some triglycerides get knocked off by circulatory lipase to form intermediates (IDL)
- Eventually turn into low density lipoproteins (LDL) in the bloodstream - LDL circulates around the bloodstream to cells (necessary to make hormones and myelin sheath)
- High density lipoproteins (HDL) takes excess cholesterol out of circulation to ensure never too much
- Extremes in cholesterol and insulin are both associated with heart and metabolic disease
- Want moderate amount of LDL and high amount of HDL
Process from chylomicrons to HDL involves increasing density, decrease size, decreasing amounts of triglycerides and increasing amounts of cholesterol
What are the functions of lipids?
- Structure and lubrication
- Provide insulation: adipose tissue (fat cells) insulate body from changes in temperature
- Protect bones, joints and organs: provide cushion to protect internal organs against shock
- Make and protect nervous system: form mytelin shealth made out of cholesterol
- Lubricate body surfaces: glands secrete oils lubricate tissues - Cell structure
- Lipids make up cell membranes
- Phospholipids keep membranes fluid (especially if more unsaturated fatty acisd)
- Cholesterol prvents membrane from being too fluid/permeable - Regulation of body processes
- Vitamin absorption (A, D, E, K) need fats to be absorbed
- Make hormones using adequate cholesterol
- Blood pressure regulation using cholesterol
- Some fats are essential (can’t be synthesized in body) to make other fats
- Regulate blood clotting and inflammation - ATP production for energy
- High fat foods have high energy content
- Burned more doing moderate intensity activity
- High intensity activity = glucose and glycogen used
- Fatty acids are transported into mitochondria, where beta-oxidation splits carbon chains into 2 C units that form acetyl-CoA and produce high energy electrons
- Note: cannot make glucose from fatty acids
- Then, if oxygen and carbohydrates are available, acetyl-CoA combines with oxaloacetate to enter citric acid cycle
- If carbohydrates are not available, ketone bonds are produced - Energy storage
- Triglycerides stored in adipose tissue to give you energy reserves
- Protect against starvation
What are ketone bodies and cautions about it?
- Acetoacetate, beta-hydroxy butyrate, acetone
- Alternative source of energy for brain cells if glucose is insufficient
- Ketogenic diets: brain no longer accesses glucose as fuel and uses ketone bodies from fat instead
- Ketosis seems to halt some forms of unrelenting seizure disorders
KETOACIDOSIS:
- Ketoacidosis: ketone bodies accumulate in blood; if prolonged may lead to coma and death
- Can be excreted in urine but if excess ketone bodies; kidneys can be overwhelmed
- Ketones build up in bloodstream
Discuss fat and weight distribution.
- Excess body fat in upper half (apple body shape) associated with a higher risk of high blood pressure, type - 2 diabetes, heart disease, stroke
- Layer of fat putting pressure on stomach puts pressure on organs and blood vessels
What are the essential fatty acids? Discuss omega-3.
- Linoleic acid (aka omega-6)
- 18:2 w-6
- Gotten by oils, margarine, nuts, seeds - Alpha-linolenic acid (aka omega-3)
- 18:3 w-3
- Necessary for regulating blood clotthing, inflammation in the body and normal brain development
- Gotten by canola oil, flax seed oil, soy oil, fatty fish, omega eggs
- DHA and EPA are premade in fish oil; plant sources (flax, hemp, chia seed) require chemical conversion using enzymes that some of us may not have a lot of
- Note: omega-3 chickens do not eat fish oil but rather use flax seed oil
How much fat do we need?
- DRIs have adequare intakes (AIs) for linolenic acid and alpha-linolenic acids (essential fatty acids)
- Linoleic acid: 12g/day for females, 17g/day for males
- Alpha-linolenic acid: 1.1g/day for females, 1.6g/day for males
- AIs are based on how much essential fat you need to keep clotting under control
- For a healthy adult, use AMDR for fat generally (20-35% of calories)
- AMDRs state that keep cholesterol, saturated and trans fat as low as possible
What is cardiovascular disease?
- Disease of the heart and blood vessels
- Includes heart disease, high blood pressure, heart attacks and strokes
- 30% of all deaths in Canada are from CVD
- 2nd leading cause of death in Canada after cancer
- Largely lifestyle factors in CVD which cannot be said for cancer
- CVD costs Canadian economy more than $20.9 billion every year
What is atherosclerosis?
- Inflammatory response to injury within the artery walls
- Lipids and fibrous materials are deposited within artery walls due to action of immune system
- Reduces elasticity of blood vessels or responsiveness to changes of blood flow = blockage
- Blockage of blood flow to heart leads to heart attack (cerebral hemorrage, aneurysm) and to brain leads to stroke
What is the process of atherosclerosis?
- Injury to normal artery causes arterial wall to become permeable
- LDL cholesterol can infiltrate artery walls and get oxidized to become even worse cholesterol - Macrophages in white blood cells engulfs LDL cholesterol and get puffed out, cannot leave
- Other platelets come and form foam cells (lots of macrophases with LDL) in arterial walls that can burst
- If foam cells burst, leaves fatty streak on inside of arterial wall = plague = platelets come and cause fibrous cap to keep everything under control
- If fibrous cap ruptures, you can get blood clot
What are the risk factors for CVD?
- Age (more plaque as we age)
- Gender (men appear to be at higher risk, perhaps due to estrogen)
- Family history of CVD
- Being overweight/obese
- Being physically inactive
- Smoking (oxidative stress = free radicals = damage blood vessels)
- Diabetes
- Diet
- Saturated and trans fat increase risk of heart disease by adding rigidity to cell membranes
- Trans fat is not needed but saturated fat is needed in small amounts
- Omega-3 and omega-6 polyunsaturated fats decrease risk of heart disease
How is CVD risk measured?
Blood lipids are measured to assess CVD risk:
- LDL-cholesterol: measure # of LDL particles
- Don’t want too high - HDL-cholesterol: measure # of HDL particles
- Want to be very high
- LDL to HDL ratio measures which “dump-trucks” are winning - Triglycerides: measure # of triglyceride-rich particles
- More associated with blood sugar level management
Discuss factors affecting blood lipids.
- Saturated fats increase LDL
- Trans fat increase LDL and decrease HDL
- Added sugars increase triglycerides (VLDL)
- MUFA decrease LDL
- Omega-3 PUFA fats decrease LDL and triglycerides (VLDL)
- Omega-6 PUFA fats decrease LDL; some types can raise HDL
- Exercise increases HDL and can decrease LDL
- Thyroid function can affect LDL cholesterol levels (hyperthyroidism = fast metabolism = low LDL cholesterol)
Discuss fats and how they are gotten from the diet. Discuss risks.
- Cholesterol
- Gotten through animal foods (meat, milk, eggs)
- However, liver can make more cholesterol than we take in if eating a normal healthy diet
- Dietary cholesterol is not associated with higher blood levels of cholesterol - Omega-3 polyunsaturated fats
- Affect cell function
- Helps infant brain develop, prevents cognitive decline with aging in the elderly, decreases risk of CVDs (improve blood lipid levels, decrease blood clotting, resolves inflammation) - Long chain omega-3 fats
- Eicosapentaenoic acid or EPA: (20:5) and docasahexaenoic acid or DHA: (22:6)
- Most heart healthy, reduce inflammation (reduce atherosclerosis)
- Fully formed omega-3 fats are found in fish from algae they eat (eg. sardines, salmond, trout, herring, mackerel)
- Canada’s Food Guide recommends eating at least 2 servings of fish per week
- If you dislike fish, eat eggs or eggs fortified with DHA, fish oil capsules or microencapsulated fish oil
- Vegetarians and vegans can obtain alpha-linoleic acid (ALA) from flax seed and canola, soy and walnut oils
- Conversion is not very efficient; assocation with CVD benefits is not clear
- Closer source would be algae
- Eating too many omega-3 fats due to fortification can lead to adverse health effects (possible dysfunction of immune system, weight gain from fat)