Topic 4

Question 1

[cite_start]”Lipids (Defining Feature)”

Answer 1

A diverse group of hydrophobic molecules (hydrocarbon composition forms nonpolar covalent bonds), providing 9 kcal/g of energy[cite: 1453, 1455, 1457].

Question 2

[cite_start]”Major Biologically Important Lipids”

Answer 2

Triglycerides (fats and oils), phospholipids, and sterols[cite: 1458].

Question 3

[cite_start]”Key Functions of Lipids”

Answer 3

Stored energy (triacylglycerol), form lipid membranes (phospholipids, cholesterol), function as vitamins (A, D, E, K), hormones (testosterone, progesterone), and thermal insulators[cite: 1461, 1462, 1463, 1464, 1466].

Question 4

[cite_start]”Triglyceride (Fat) Structure”

Answer 4

Constructed from two smaller molecules: Glycerol (a three-carbon alcohol) and three fatty acids[cite: 1473, 1475, 1724]. [cite_start]The fatty acids link via ester linkages, making the resulting triglyceride water insoluble[cite: 1476, 1725].

Question 5

Fatty Acid Structure

Answer 5

An organic acid with a methyl group at one end and an acid group at the other. [cite_start]Typically has an even number of carbons[cite: 1537, 1538, 1539].

Question 6

[cite_start]”Long-Chain Fatty Acids (LCFAs)”

Answer 6

Contain 12 or more carbons[cite: 1547, 1548]. [cite_start]Found primarily in meat, fish, and vegetable oils[cite: 1542, 1547].

Question 7

[cite_start]”Medium- & Short-Chain Fatty Acids (MCFAs/SCFAs)”

Answer 7

Contain 2-4 or 6-10 carbons[cite: 1545, 1546]. [cite_start]Found in dairy products[cite: 1543].

Question 8

Saturated Fatty Acid (SFA)

Answer 8

Has the maximum number of hydrogen atoms possible and no double bonds. [cite_start]They are solid at room temperature[cite: 1732, 1836].

Question 9

[cite_start]”Unsaturated Fatty Acid (UFA)”

Answer 9

Has one or more double bonds[cite: 1734]. [cite_start]They are liquid at room temperature (oils)[cite: 1839].

Question 10

[cite_start]”Monounsaturated Fatty Acid (MUFA)”

Answer 10

Has one carbon-carbon double bond[cite: 1735]. [cite_start]Example: Oleic acid (18-carbon)[cite: 1809].

Question 11

[cite_start]”Polyunsaturated Fatty Acid (PUFA)”

Answer 11

Has more than one (>1) carbon-carbon double bond[cite: 1736]. [cite_start]Example: Linoleic acid (18-carbon)[cite: 1811].

Question 12

[cite_start]”Physical State of Saturated Fats”

Answer 12

Solid at room temperature (e.g., most animal fats, coconut/palm oils)[cite: 1836, 1837, 1850].

Question 13

[cite_start]”Physical State of Unsaturated Fats/Oils”

Answer 13

Liquid at room temperature (e.g., plant fats, fish fats)[cite: 1839, 1840].

Question 14

Stability/Resistance to Oxidation (SFA vs UFA)

Answer 14

Saturated fat is more resistant to oxidation; [cite_start]Polyunsaturated fat spoils most readily[cite: 1860, 1861].

Question 15

Hydrogenation (Process)

Answer 15

The process of converting unsaturated fats to saturated fats by adding hydrogen. [cite_start]Prolongs shelf life by protecting against oxidation, but also alters texture[cite: 1865, 1866, 1867].

Question 16

[cite_start]”Cis-Fatty Acid”

Answer 16

In natural unsaturated fats, the two carbons participating in a double bond bind in the cis-isomer form, causing a bend in the chain[cite: 1889, 1890, 1833].

Question 17

Trans-Fatty Acid

Answer 17

Has its hydrogens on the opposite sides of the double bond, making the molecule more linear. [cite_start]They are typically formed in partially hydrogenated foods[cite: 1892, 1893].

Question 18

[cite_start]”Metabolic Effect of Trans Fats”

Answer 18

Trans fats act like saturated fats in the body and may contribute more than saturated fats to cardiovascular disease[cite: 1896, 1897].

Question 19

[cite_start]”Omega Number”

Answer 19

Refers to the position of the first double bond, counting from the methyl end[cite: 1902].

Question 20

[cite_start]”Omega-3 Fatty Acid (Definition)”

Answer 20

The first double bond is located in the third position from the methyl end[cite: 1903]. [cite_start]Example: Linolenic acid[cite: 1905].

Question 21

[cite_start]”Omega-6 Fatty Acid (Definition)”

Answer 21

The first double bond is located in the sixth position from the methyl end[cite: 1904]. [cite_start]Example: Linoleic acid[cite: 1913].

Question 22

[cite_start]”Essential Fatty Acids (The Two Families)”

Answer 22

Linoleic Acid (Omega-6) and Linolenic Acid (Omega-3)[cite: 2334, 2337].

Question 23

[cite_start]”Omega-3 Derivatives (Key Products)”

Answer 23

Can make EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), important for eyes, brain, and heart[cite: 2339, 2340].

Question 24

Eicosanoids (Role)

Answer 24

Made from arachidonic acid (Omega-6) and EPA (Omega-3). [cite_start]They act like hormones and include prostaglandins, thromboxanes, and leukotrienes[cite: 2345, 2348, 2349].

Question 25

[cite_start]"Phospholipid Structure"

Answer 25

Two fatty acids and a **phosphate group** attached to glycerol[cite: 1935]. [cite_start]This structure creates a **hydrophobic tail** and a **hydrophilic head**[cite: 1936].

Question 26

[cite_start]"Phospholipid Primary Role"

Answer 26

Major component of all **cell membranes**, forming a **bilayer** structure[cite: 1981, 1982]. [cite_start]Also function as emulsifying agents and aid in lipid transport across membranes[cite: 1983, 1984].

Question 27

[cite_start]"Lecithin (Phospholipid Example)"

Answer 27

A well-known phospholipid found in eggs, liver, soybeans, wheat germ, and peanuts[cite: 1995, 1997].

Question 28

[cite_start]"Sterols (Definition)"

Answer 28

Terpene-based molecules [cite: 2004] [cite_start]characterized by a multi-ring structure[cite: 2059, 2065]. [cite_start]Example: Cholesterol[cite: 2031].

Question 29

Sterol Roles

Answer 29

Starting material for **bile acids**, **sex hormones**, **adrenal hormones**, and **vitamin D**. [cite_start]Also a structural component of cell membranes[cite: 2034, 2035].

Question 30

[cite_start]"Sterols in Foods"

Answer 30

Found in plant and animal foods[cite: 2043]. [cite_start]**Cholesterol** is found in **animal foods only** (meat, eggs, dairy)[cite: 2044].

Question 31

[cite_start]"Atherosclerosis (Lipid-Related Disease)"

Answer 31

Caused by cholesterol forming deposits (plaque) in the artery wall, restricting blood flow and raising blood pressure[cite: 2037, 2038, 2388].

Question 32

[cite_start]"Lipid Digestion Challenge"

Answer 32

Fats are hydrophobic while digestive enzymes are hydrophilic; the challenge is to keep fats mixed in the watery GI fluids[cite: 2101, 2102].

Question 33

[cite_start]"Goal of Fat Digestion"

Answer 33

To dismantle triglycerides into absorbable small molecules: **monoglycerides, fatty acids, and glycerol**[cite: 2103].

Question 34

[cite_start]"Digestion: Mouth"

Answer 34

**Lingual lipase** is secreted, initiating slight lipid hydrolysis (significant role only in infants for milk fat)[cite: 2109, 2111, 2112, 2146, 2147].

Question 35

Digestion: Stomach

Answer 35

Churning mixes fat with water/acid. [cite_start]**Gastric lipase** hydrolyzes a very small amount of fat[cite: 2113, 2114, 2152].

Question 36

[cite_start]"Digestion: Small Intestine (Hormone Trigger)"

Answer 36

Fat entry triggers the release of the hormone **Cholecystokinin (CCK)**, signaling the gallbladder to release bile[cite: 2155].

Question 37

[cite_start]"Digestion: Small Intestine (Bile Role)"

Answer 37

Bile acts as an **emulsifier**, drawing fat molecules into the surrounding watery fluids to create smaller droplets[cite: 2156, 2173, 2175].

Question 38

[cite_start]"Digestion: Small Intestine (Enzymes)"

Answer 38

**Pancreatic and intestinal enzymes** hydrolyze lipids into monoglycerides and fatty acids[cite: 2157, 2158].

Question 39

[cite_start]"Bile's Route (Enterohepatic Circulation)"

Answer 39

Most bile is **reabsorbed** in the small intestine and sent back to the liver to be reused[cite: 2210, 2220].

Question 40

[cite_start]"Bile's Route (Excretion)"

Answer 40

Some bile can be trapped by **dietary fibers** in the large intestine and **excreted**, which effectively reduces blood cholesterol[cite: 2211, 2212, 2218].

Question 41

[cite_start]"Lipid Absorption: Directly into Bloodstream"

Answer 41

**Glycerol** and **short- and medium-chain fatty acids** diffuse easily into intestinal cells and are absorbed directly into the bloodstream[cite: 2226, 2227, 2255].

Question 42

[cite_start]"Lipid Absorption: Lymphatic System Route"

Answer 42

**Monoglycerides** and **long-chain fatty acids** combine with bile to form **micelles**[cite: 2229, 2250, 2252]. [cite_start]Micelles release lipids into the cell, where they are re-formed into triglycerides and packaged into **chylomicrons** for transport via the lymph[cite: 2230, 2231, 2249, 2257].

Question 43

[cite_start]"Lipoproteins (Function)"

Answer 43

Vehicles that transport lipids through the watery fluids of the blood (made possible by surrounding hydrophobic core with hydrophilic shell)[cite: 2259, 2303].

Question 44

[cite_start]"Lipoprotein Density Principle"

Answer 44

The more lipids (triglycerides) present, the **lower** the density; the more proteins present, the **higher** the density[cite: 2265].

Question 45

Chylomicrons (Type 1)

Answer 45

**Largest and least dense**. [cite_start]Transport **diet-derived lipids** from the intestines to the cells and liver[cite: 2263, 2264, 2266].

Question 46

VLDL (Very-Low-Density Lipoproteins) (Type 2)

Answer 46

Composed primarily of **triglycerides**. Made by the **liver**. [cite_start]Transport lipids to the tissues[cite: 2268, 2269, 2270].

Question 47

LDL (Low-Density Lipoproteins) (Type 3)

Answer 47

Composed primarily of **cholesterol**. Transport lipids to the tissues. [cite_start]Known as 'bad' cholesterol[cite: 2276, 2277, 2318].

Question 48

HDL (High-Density Lipoproteins) (Type 4)

Answer 48

Composed primarily of **protein**. Transport **cholesterol from the cells to the liver** (for removal or recycling). [cite_start]Known as 'good' cholesterol[cite: 2279, 2280, 2320].

Question 49

Blood Lipid Desirable Levels

Answer 49

Total Cholesterol: $<200~mg/dL$; LDL Cholesterol: $<100~mg/dL$; HDL Cholesterol: $\ge60~mg/dL$; [cite_start]Triglycerides: $<150~mg/dL$[cite: 2378, 2379, 2380, 2381].

Question 50

[cite_start]"Saturated/Trans Fat Effect on Lipoproteins"

Answer 50

High intake of saturated and trans fat raises **LDL cholesterol**[cite: 2319, 2391, 2396].

Question 51

[cite_start]"Trans Fat Effect on HDL"

Answer 51

Trans-fatty acids also **decrease HDL cholesterol**[cite: 2396].

Question 52

[cite_start]"Dietary Cholesterol Effect"

Answer 52

Dietary cholesterol has **less effect** on blood cholesterol than saturated fat and trans fat[cite: 2401].

Question 53

[cite_start]"Monounsaturated Fat Effect"

Answer 53

Tends to lower **LDL** but **not HDL**[cite: 2050].

Question 54

[cite_start]"Polyunsaturated Fat Effect"

Answer 54

Tends to lower **both LDL and HDL**[cite: 2050].

Question 55

[cite_start]"Best Dietary Strategy to Prevent Heart Disease"

Answer 55

Replacing saturated fat and trans fat with **monounsaturated fat and polyunsaturated fat**[cite: 2459].

Question 56

[cite_start]"Factors that Lower LDL and Raise HDL"

Answer 56

Weight control, replacing SFA/Trans Fat with MUFA/PUFA, soluble fibers, phytochemicals, moderate alcohol consumption, and physical activity[cite: 2325, 2326, 2327, 2328, 2329, 2330].

Question 57

Fat and Cancer Risk

Answer 57

Dietary fat is associated with risks for some types of cancer, but the link is not as strong as heart disease. [cite_start]Fat may act as a **promoter** once cancer has developed; saturated fat from meat is implicated[cite: 2478, 2479, 2480].

Question 58

[cite_start]"Adipose Tissue (Fat Storage)"

Answer 58

Readily stores fat[cite: 2356]. [cite_start]Stores excess energy (twice that of carbohydrate/protein)[cite: 2355].

Question 59

[cite_start]"Lipoprotein Lipase (LPL)"

Answer 59

Hydrolyzes triglycerides from lipoproteins as they pass and directs the resulting parts into the cells for energy or storage[cite: 2357].

Question 60

[cite_start]"Hormone-Sensitive Lipase"

Answer 60

Inside adipose cells; hydrolyzes stored triglycerides when needed for energy[cite: 2359].

Question 61

Using Fat for Energy (Metabolism)

Answer 61

Fasting metabolizes fat, but fat requires **carbohydrate and protein** for complete breakdown. [cite_start]Fat fragments can be converted into **ketone bodies**[cite: 2360, 2361].