N&H Exam 2

What are the 3 major classes of lipids?

1. triglycerides

2. phospholipids

3. sterols

What are major functions of lipids in the body?

1. Energy storage

2. Cushioning and insulation

3. Cell membrane structure and signaling

4. Raw materials for hormones, bile, and vitamin D

What is the structure of a triglyceride?

1 glycerol backbone + 3 fatty acids

What is the main storage form of fat in the body?

triglycerides stored in adipocytes (fat cells).

How many kcal does 1 gram of fat provide?

9 kcal/g

What are the 3 fatty acid types by saturation?

1. saturated

2. monounsaturated

3. polyunsaturated

How many double bonds do saturated fatty acids have?

0 - their carbon chains are saturated with hydrogen

How many double bonds do MUFAs and PUFAs have?

MUFA: 1

PUFA: 2 or more

How does saturation affect melting point?

More saturation generally means higher melting point and more solid fat.

How does fatty acid chain length affect properties?

Longer chains generally have higher melting points and lower water solubility.

What is the different between cis and trans fatty acids?

cis: hydrogens on same side, bent chain

trans: opposite sides, straighter chain

What do omega-3 and omega-6 designations indicate?

Position of the first double bond from the omega (methyl) end.

What is an alpha carbon in a fatty acid?

The carbon adjacent to the carboxyl carbon.

What is the structure of a phospholipid?

glycerol, 2 fatty acids, and a phosphate-containing head group

Why are phospholipids amphipathic?

They have a hydrophilic head and hydrophobic tails.

What is the main role of phospholipids in cells?

Form the cell membrane bilayer and participate in signaling.

Why lecithin useful in foods?

It emulsifies oil and water, stabilizing mixtures.

What is the basic structure of a sterol?

4 fused carbon rings

What are 4 functions of chelosterol?

1. Cell membranes

2. precursor for bile acids

3. steroid hormones

4. vitamin D

Where is dietary cholesterol found?

animal-derived foods, such as eggs, meat, and dairy.

What is a cholesteryl ester?

Cholesterol joined to a fatty acid; used for cholesterol storage and transport.

Where does most lipid digestion and absorption occur?

small intestine

Where is bile made and stored?

made in the liver; stored in the gallbladder

What is bile’s role in fat digestion?

Emulsifies fat into small droplets, increasing surface area for lipase.

Which enzyme digests dietary triglycerides?

pancreatic lipase

What are the major products of triglyceride digestion?

Free fatty acids and monoglycerides

What is a micelle’s function?

Carries long-chain lipid digestion products to the enterocyte surface.

Do intact micelles enter enterocytes?

NO - they release their lipids at the cell membrane for absorption.

How do short- and medium-chain fatty acids travel?

enterocytes → portal blood → liver

transported with albumin

What is the transport pathway for long-chain fatty acids?

micelles → enterocytes → re-esterification → chylomicrons → lymph → blood

What happens to long-chain lipids inside enterocytes?

triglycerides, phospholipids, and cholesterols are reformed.

Why do chylomicrons enter lymph before blood?

They are too large to enter ordinary intestinal blood capillaries.

What are the 4 major blood lipoproteins?

1. chylomicrons

2. VLDL

3. LDL

4. HDL

What is the main function of chylomicrons?

carry dietary triglycerides from the intestine to body tissues.

What is the main function of VLDL?

Carry liver-produced triglycerides to body tissues

What is the main function of LDL?

deliver cholesterol to body tissues; high levels increase cardiovascular risk

What is the main function of HDL?

help return excess cholesterol from tissues to the liver.

What does lipoprotein lipase (LPL) do?

hydrolyzes triglycerides in chylomicrons and VLDL, releasing fatty acids

How does VLDL eventually become LDL?

triglyceride removal converts VLDL → IDL → LDL

Which lipoproteins mainly transport triglycerides?

chylomicrons and VLDL

Which lipoprotein mainly transport cholesterol?

LDL and HDL

What are the 2 essential fatty acids?

1. Linoleic Acid (omega-6)

2. Alpha Linolenic Acid (omega-3)

Why are linoleic and linolenic acids essential?

because the body cannot synthesize them; they must come from food

What are eicosanoids?

Fatty-acid-derived signaling molecules regulating inflammation and other processes.

How do omega-3 and omega-6 fatty acids affect inflammation?

Both form signaling molecules; omega-3 derivatives are often less inflammatory.

What are important roles of DHA?

supports brain, nerve, and retinal structure and function

What does hydrogenation do to oils?

adds hydrogen to double bonds, making oils more solid and oxidation-resistant.

Why are industrial trans fats harmful?

raise LDL, often lower HDL, and increase cardiovascular risk

Which plant oils are especially high in saturated fat?

coconut oil & palm oil

Which oils are rich in monounsaturated fat?

canola oil & olive oil

What is a healthier replacement for butter?

olive oil or another unsaturated vegetable oil

What is the adult AMDR for total fat?

20-35% total daily calories

Why does fat type matter more than fat amount alone?

Replacing saturated/trans fats with unsaturated fats generally improves blood lipids.

What is the debate about dietary cholesterol and eggs?

Dietary cholesterol matters, but saturated fat and genetics often have greater effects.

What are major benefits and risks of eating fish?

omega-3 fatty acids and protein; some species contain mercury

What is metabolism?

the sum of chemical reactions that build and break down molecules.

How do catabolism and anabolism differ?

catabolism: breaks down molecules and releases energy

anabolism: builds molecules

What is ATP?

Adenosine Triphosphate: the cell’s immediate energy currency

What happens when ATP is hydrolyzed?

ATP → ADP + phosphate, releasing usable energy

How is ATP produced from carbohydrates?

glycolysis → acetyl-CoA → citric acid cycle → electron transport chain

How are fatty acids used to produce ATP?

beta-oxidation produces acetyl-CoA, which enters aerobic energy pathways.

How can proteins be used to produce ATP?

Amino acids are deaminated; carbon skeletons enter energy pathways

What is the main fuel state after eating?

Postprandial (fed) state: insulin rises; glucose use and nutrient storage increase

What happens during the post-absorptive state?

Insulin decreases; glucagon promotes glycogen breakdown and fat mobilization.

What happens during the prolonged fasting?

glycogen declines; gluconeogenesis, fat oxidation, and ketone production increase

What is glycogenolysis?

breakdown of stored glycogen to supply glucose

What is gluconeogenesis?

production of glucose from noncarbohydrate precursors

What is lipolysis?

breakdown of stored triglycerides into fatty acids and glycerol

What is ketosis?

As glycogen runs low, the body transitions to burning fat and producing ketones for fuel through a process

What is energy balance?

relationship between energy intake and energy expenditure

What happens during positive energy balance?

energy intake exceeds expenditure; excess energy is stored

What happens during negative energy balance?

energy expenditure exceeds intake; stored fuels are mobilized

What are the 3 main components of energy expenditure?

basal metabolism, physical activity, and thermic effect of food

What is basal metabolic rate (BMR)?

energy requried to maintain vital functions at rest

What is the thermic effect of food (TEF)?

Energy used to digest, absorb, and process food; approximately 10%.

What is the thermic effect of food (TEF)?

Energy used to digest, absorb, and process food; approximately 10%

What is body composition?

properties of fat mass and fat-free mass, including muscle, bone, and water.

How is BMI calculated?

Weight (kg) / height (m)²

What is an important limitation of BMI?

It does not distinguish muscle from fat or show fat distribution?

What is the difference between visceral and subcutaneous fat?

visceral surrounds internal organs; subcutaneous lies beneath the skin

Why is excess visceral fat concerning?

associated with inflammation, insulin, resistance, and cardiometabolic disease.

What are adipocyte hypertrophy and hyperplasia?

Hypertrophy: fat cells enlarge

Hyperplasia: fat cell number increases

Which hormone stimulates hunger?

ghrelin, produced mainly by the stomach

Which hormone helps suppress appetite?

Leptin, released by adipose tissue.

What is the set-point theory of body weight?

Body regulation tends to defend a weight range through appetite and expenditure changes

What external factors contribute to increased body fat?

food environment, inactivity, stress, sleep disruption, and socioeconomic conditions

What health risks can occur with too little body fat?

Hormonal disruption, poor insulation, nutrient deficiencies, and impaired immunity

What are key features of effective behavior change?

specific goals, self-monitoring, realistic habits, social support, and relapse planning

How does fatty acid saturation affect cell membrane fluidity?

More unsaturated fatty acids increase fluidity; saturated fatty acids pack tightly.

Why are short-chain fatty acids more water-soluble?

Their short hydrocarbon chains allow the polar carboxyl group (hydrophilic) to dominate

What is the carbon length of a short-chain fatty acid?

fewer than 8 carbons

How much dietary fat can the intestine absorb?

up to approx. 98%

How does dietary fat affect digestion time?

fat slows digestion, so higher-fat meals take longer to digest

What activates lipoprotein lipase (LPL)?

ApoC-II on the surface of chylomicrons

What happens when LPL acts on chylomicrons?

Triglycerides are hydrolyzed, releasing fatty acids and leaving remnants

What happens to chylomicron remnants?

They are taken up by the liver

How does hydrogen improve oil shelf life?

it reduces double bonds, making oils more resistant to oxidation

What is the recommended limit for saturated fat?

Less than 10% of daily calories

Why is soluble fiber recommended for cholesterol management?

It helps lower LDL cholesterol.

Why is waist circumference useful alongside BMI?

It helps assess abdominal fat and cardiometabolic risk.