Nutrition Ch 5 -Lipids
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123 Terms
What are lipids?
Fats, oils, phospholipids, and sterols
What percent of body lipids are triglycerides?
95%
What are the three major classes of lipids?
Triglycerides, phospholipids, sterols(cholesterol)
What are triglycerides made of?
3 fatty acids + 1 glycerol
What is the main function of triglycerides?
energy storage
Why are triglycerides efficient for energy storage?
They store tightly without water and provide more than twice the energy per gram as carbs or protien.
What role does fat play as fuel?
Provides most energy for the resting body and muscular work.
What is fat’s role as an emergency reserve?
Supplies energy during starvation or severe illness.
How does fat protect organs?
Cushions organs and absorbs shock.
How does fat help regulate body temperature?
Insulates the body and slows heat loss.
Why are fats essential to cell membranes?
They form the major structural material of membranes.
How do fat cells act like endocrine organs?
They secrete hormones that regulate appetite, energy use, and balance.
Why are fats important nutrients?
They provide essential fatty acids and fat-soluble vitamins.
Which vitamins require fat for absorption?
A, D, E, and K
How do fats affect appetite and satiety?
Increase appetite and promote feelings of fullness.
How do fats improve food quality?
Enhance flavor, aroma, texture, and crispness
What does “saturation” mean?
Whether fatty acids are holding all possible hydrogen atoms.
What is a saturated fatty acid?
No double bonds; fully hydrogenated.
What is an unsaturated fatty acid?
One or more double bonds
What is a monounsaturated fatty acid?
One double bond
What is a polyunsaturated fatty acid (PUFA)?
Two or more double bonds
How does saturation affect melting point?
More saturated = higher melting point
Why are saturated fats solid at room temperature?
Straight chains pack tightly
Why are unsaturated fats liquid at room temperature?
Kinks from double bonds prevent tight packing.
Why does cream rise to the top of milk?
Milk fat is saturated and floats above watery fluid.
What is homogenization?
Forcing milk under pressure to break fat droplets into smaller particles.
Where are polyunsaturated fatty acids commonly found?
Vegetable oils and fish oils.
Which fats are generally the most saturated?
Animal fats
How do phospholipids differ from triglycerides?
Phospholipids have 2 fatty acids + 1 phosphate group, not 3 fatty acids.
Why are phospholipids water-soluble on one end?
The phosphate-containing head is water loving (hydrophilic).
What allows phospholipids to act as emulsifiers?
They have both water-loving and fat-loving parts.
What is lecithin and why is it important?
A phospholipid that helps form stable emulsions(ex: mayonnaise).
Why doesn’t the body need lecithin supplements?
The body can make all the lecithin it needs.
What structural role do phospholipids play?
They form the double-layered cell membranes.
How do phospholipids help with cell signaling?
Some generate signals inside cells in response to hormones like insulin.
What are sterols?
Lipids with interconnected carbon rings.
What is cholesterol used for in the body?
Cell membranes, bile production, vitamin D, and steroid hormones.
Why is bile important?
It acts as an emulsifier for fat digestion.
How is cholesterol related to heart disease?
It contributes to plaque buildup in arteries(atherosclerosis)
What are plant sterols and why are they beneficial?
They resemble cholesterol and reduce cholesterol absorption.
Where are plant sterols found?
Nuts, seeds, legumes, whole grains, fruits, and vegetables.
Where does fat digestion begin?
In the mouth, but one minimally.
Why is fat digestion limited in the stomach?
Fat separates from water and stomach churning can’t fully disperse it.
Where does most fat digestion occur?
The small intestine.
What substance emulsifies fats?
Bile (made by liver, stored in gallbladder)
How does bile work?
One end attracts fat; the other attracts water, suspending fat droplets
What enzymes digest fat?
Pancreatic enzymes (lipases).
What do lipases break triglycerides into?
Free fatty acids, monoglycerides, glycerol.
How do fats cross the watery mucus layer of the intestine?
Bile shuttles them across.
Where are fats absorbed?
Intestinal villi
About what percentage of dietary fat is absorbed?
95%
Which fats enter the bloodstream directly?
Glycerol and short-chain fatty acids.
Why can’t large fats enter the blood directly?
They are not water-soluble.
What are chylomicrons?
Lipoproteins that transport fats through lymph and blood
Where do chylomicrons travel first?
Through the lymph system, then into the bloodstream
Where is body fat stored?
Subcutaneous fat (under skin) and intestinal fat pads (abdomen, breasts)
What form is fat stored as?
Triglycerides in fat cells
Why is converting carbs to fat inefficient?
It requires many chemical steps and energy.
Why is storing dietary fat efficient?
It requires fewer chemical steps.
What happens when tissues need energy?
Fat cells release fatty acids into the blood.
How is energy released from fatty acids?
They are broken down into fragments and combined with glucose products.
What are the final byproducts of fat breakdown?
Carbon dioxide, water, and energy
Why are carbohydrates needed for efficient fat metabolism?
They help fat break down completely.
What happens if carbs are too low?
Ketones form from incomplete fat breakdown.
What types of fats are most strongly associated with cardiovascular diseases (CVD)?
Saturated and trans fats
What happens to blood lipids when saturated fats are replaced with unsaturated fats?
Blood lipid profiles improve and heart disease risk decreases.
What percentage of daily calories should come from fat?
About 20-35% of total daily energy.
How much saturated fat should be consumed daily?
Less than 10% of daily energy.
How much trans-fat should be consumed?
As little as possible
Why do Mediterranean diets have lower heart disease rates despite high fat intake?
Most fat comes from unsaturated fatty acids.
Why is consuming too little fat harmful?
It causes low energy and deficiencies in vitamins and essential fatty acids.
What are chylomicrons?
Lipoproteins that transport dietary fat from digestion through the bloodstream.
Why do lipoproteins contain protein and phospholipids?
To allow fat to travel in watery blood.
Which lipoprotein is the least dense?
Chylomicrons
Name the four major lipoproteins.
Chylomicrons, VLDL, LDL, HDL
What is the major function of VLDL(very-low-density lipoprotein)?
To transport triglycerides made in the liver to body cells.
What is the main function of LDL(low-density lipoprotein)?
To deliver cholesterol to body tissues
What is the main function of HDL(High-density lipoprotein)?
To remove excess cholesterol and return it to the liver.
Why is LDL(low-density lipoprotein) considered “bad” cholesterol?
High LDL leads to cholesterol buildup in arteries
Why is HDL(High-density lipoprotein) considered “good” cholesterol?
It helps remove cholesterol and lowers heart disease risks.
What happens when HDL(High-density lipoprotein) levels are low?
Heart disease risk increases.
Which affects blood cholesterol more saturated fats or dietary cholesterol?
Saturated fat.
How can LDL cholesterol be lowered through diet?
Replace saturated fats with unsaturated fats.
What is the most effective way to raise HDL cholesterol?
Regular physical activity.
What makes linoleic and linolenic acids essential?
The body cannot make them.
Which essential fatty acid is omega-6?
Linoleic acid
Which essential fatty acid is omega-3?
Linolenic acid
What are eicosanoids?
Biologically active compounds that regulate inflammation, clotting, and blood vessels.
How do omega-3 eicosanoids affect blood vessels?
They relax vessels and lower blood pressure.
Why is balance between omega-3 and omega-6 important?
It supports normal blood pressure and heart health.
What are EPA and DHA?
Long-chain omega-3 fatty acids.
Why does the body make limited EPA and DHA?
Conversion from linolenic acid is inefficient.
What foods provide the best sources of EPA and DHA?
Fatty fish and seafood.
Why is DHA important for brain function?
The brain is lipid-rich and DHA supports communication and development.
Where are unsaturated and saturated fats commonly found?
Unsaturated fats are found in vegetable oils and fish; saturated fats are mostly found in animal fats and tropical oils like coconut and palm oil.
What role do phospholipids play in the body?
They form cell membranes and act as emulsifiers to keep fat dispersed in water
Why are phospholipids able to mix with both fat and water?
They have a water loving head and fat-loving tails.
What is cholesterol used for in the body?
Making bile, vitamin D, steroid hormones, and maintaining cell membranes.
How do plant sterols affect cholesterol levels?
They reduce cholesterol absorption in the digestive tract.
Where does most fat digestion occur?
In the small intestine