Lipids: Triglycerides and Fatty Acids

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Questions and Answers

In the context of lipid geometry pertaining to double bonds, which of the following statements most accurately describes the distinction between cis and trans configurations and their implications for the physical state of fats at room temperature?

Cis double bonds result in a more linear structure that allows for tighter packing of fatty acids, leading to higher melting points compared to trans double bonds.
Trans double bonds are predominantly found in nature, lending to the higher prevalence of solid fats compared to the relative scarcity of naturally occurring cis fats.
Trans double bonds introduce kinks in the fatty acid chains, preventing close packing and resulting in higher melting points compared to cis double bonds.
Cis double bonds create a bend in the fatty acid chain, hindering close packing and typically resulting in lower melting points compared to saturated fats and trans double bonds. (correct)

The designation 'omega-n' in fatty acid nomenclature directly indicates the number of carbon-carbon double bonds present in the fatty acid molecule.

False (B)

Articulate the biochemical rationale explaining why humans lack the enzymatic capability to introduce double bonds beyond the ninth carbon atom (Δ9 desaturase limitation), when numbering from the carboxyl end of a fatty acid.

Humans lack the Δ12 and Δ15 desaturase enzymes required to insert double bonds beyond carbon 9.

The primary structural distinction between sterols and other lipid classes, such as triglycerides and phospholipids, lies in sterols possessing a characteristic _______ ring system, while other lipids feature a glycerol backbone.

tetracyclic Signup and view all the answers

Match each lipoprotein class with its primary function in lipid metabolism.

Chylomicrons = Transport of dietary triglycerides from intestines to peripheral tissues VLDL (Very Low-Density Lipoproteins) = Transport of triglycerides synthesized in the liver to peripheral tissues LDL (Low-Density Lipoproteins) = Transport of cholesterol from the liver to peripheral tissues HDL (High-Density Lipoproteins) = Transport of cholesterol from peripheral tissues back to the liver for excretion Signup and view all the answers

Considering the metabolic fates of fatty acids, which pathway is primarily responsible for the ATP production from excess triglycerides?

Beta-oxidation (A) Signup and view all the answers

Complete hydrogenation of unsaturated fatty acids results in the formation of trans fats.

False (B) Signup and view all the answers

Explain the mechanism by which plant sterols are effective in reducing blood cholesterol levels.

Plant sterols interfere with cholesterol absorption in the small intestine. Signup and view all the answers

The enzyme _______, situated on the endothelium of blood vessels, is crucial for hydrolyzing triglycerides in lipoproteins, facilitating the uptake of fatty acids into cells.

lipoprotein lipase Signup and view all the answers

Match the fatty acid with its corresponding shorthand nomenclature.

alpha-linolenic acid = 18:3n3 linoleic acid = 18:2n6 oleic acid = 18:1n9 arachidonic acid = 20:4n6 Signup and view all the answers

Identify the primary reason that fat replacers, such as olestra, can potentially lead to gastrointestinal side effects.

Inability to be absorbed in the small intestine. (C) Signup and view all the answers

De novo lipogenesis, the synthesis of fatty acids from non-lipid precursors, is primarily regulated by dietary cholesterol intake.

False (B) Signup and view all the answers

Outline the key steps involved in micelle formation and its significance in the context of lipid absorption within the small intestine.

Emulsification by bile, incorporation of lipids, transport across unstirred water layer. Signup and view all the answers

Following their synthesis within enterocytes, long-chain fatty acids are re-esterified into triglycerides and packaged, along with apolipoproteins, phospholipids, and cholesterol, into large lipoprotein particles called _______ for transport into the lymphatic system.

chylomicrons Signup and view all the answers

Match the lipoprotein with its role in cholesterol transport.

LDL = Transports cholesterol from the liver to peripheral tissues HDL = Picks up cholesterol from peripheral tissues and returns it to the liver VLDL = Transports endogenously synthesized triglycerides from the liver to peripheral tissues Signup and view all the answers

When considering the impact of dietary fatty acids on cardiovascular health, what is the most accurate interpretation of the research regarding saturated fats, monounsaturated fats (MUFA), and polyunsaturated fats (PUFA) as it relates to LDL cholesterol?

Replacement of saturated fats with MUFA/PUFA can reduce LDL cholesterol, suggesting that the overall fatty acid profile is more critical than individual fatty acids. (D) Signup and view all the answers

The designation 'essential' for a fatty acid implies that the human body can synthesize it de novo, but must do so under specific physiological conditions.

False (B) Signup and view all the answers

Explain how cis and trans fatty acids differ in their chemical structure, and how this structural difference affects their physical properties, such as melting point.

Cis: same side, bent; trans: opposite sides, linear; melting - point higher in trans. Signup and view all the answers

The process of _______ involves the enzymatic modification of essential fatty acids, such as linoleic acid and alpha-linolenic acid, to produce longer-chain, more unsaturated derivatives like arachidonic acid, EPA, and DHA.

desaturation and elongation Signup and view all the answers

Match the sign of essential fatty acid deficiency with the corresponding family (n-6 or n-3).

n-6 deficient = IQ n-3 deficient = Visual acuity Signup and view all the answers

Considering the current recommendations and perceptions regarding dietary fat intake, which statement best reflects the nuanced view on saturated fats and their role in cardiovascular health?

While high intakes of saturated fats are associated with increased LDL cholesterol, the impact on cardiovascular health is complex and depends on the source of saturated fats and the overall dietary pattern. (A) Signup and view all the answers

According to current guidelines, dietary cholesterol, rather than blood cholesterol, is directly linked to increased risk of cardiovascular disease.

False (B) Signup and view all the answers

Describe the role of the lungs in fat metabolism and excretion.

Excrete CO2, a byproduct of fat breakdown. Signup and view all the answers

The liver plays a crucial role in maintaining cholesterol homeostasis by acting as a _______, synthesizing cholesterol de novo and adjusting its production based on dietary intake and bodily needs.

thermostat Signup and view all the answers

Match the term with the definition.

MUFA = Monounsaturated fatty acids. PUFA = Polyunsaturated fatty acids. SAFA = Saturated fatty acids. Signup and view all the answers

Which of the following statements best describes the physiological role of bile in lipid digestion and absorption?

Bile emulsifies fats, increasing their surface area for enzymatic digestion. (B) Signup and view all the answers

The primary function of chylomicrons is to transport lipids from the liver to peripheral tissues.

False (B) Signup and view all the answers

Explain the role of lipoprotein lipase (LPL) in the metabolism of lipoproteins.

Hydrolyzes triglycerides in lipoproteins to release fatty acids. Signup and view all the answers

In the context of essential fatty acid metabolism, _ and _ are derivatives of alpha-linolenic acid (ALA) that have been shown to play a significant role in reducing the risk of heart disease through various mechanisms, including reducing triglyceride levels and demonstrating anti-inflammatory effects.

EPA, DHA Signup and view all the answers

Match each food source with its predominant type of fatty acid.

Olive oil = Monounsaturated fatty acids (MUFA) Coconut oil = Saturated fatty acids (SAFA) Flaxseed oil = Omega-3 polyunsaturated fatty acids Corn oil = Omega-6 polyunsaturated fatty acids Signup and view all the answers

When assessing the impact of dietary interventions on blood lipid profiles, which parameter provides the most comprehensive indication of cardiovascular risk?

Ratio of total cholesterol to HDL cholesterol. (D) Signup and view all the answers

Plant sterols effectively lower blood cholesterol levels by inhibiting de novo cholesterol synthesis in the liver.

False (B) Signup and view all the answers

Describe the role of the enzyme cholesterol esterase in the digestion of lipids. Particularly, where does it act, and what is the product of its activity?

Small intestine; free cholesterol and a fatty acid. Signup and view all the answers

The presence of _______ double bonds in fatty acids decreases their melting point due to the introduction of kinks in the acyl chain, which interferes with efficient molecular packing.

cis Signup and view all the answers

Match each class of eicosanoids with its primary role:

Leukotrienes = Inflammatory mediators, particularly in asthma and allergic reactions Prostaglandins = Modulation of inflammation, pain, and fever Thromboxanes = Platelet aggregation and vasoconstriction Signup and view all the answers

What is the impact on the designation if canola oil says high oleic?

Lower ALA (D) Signup and view all the answers

The intake of eggs affect blood cholesterol for healthy individuals.

False (B) Signup and view all the answers

Give a reason why short and medium chain fatty acids aren't packaged into chylomicrons.

Easily absorbed Signup and view all the answers

The most valuable export commodity in Canada from oil is ______.

Canola Signup and view all the answers

Flashcards

What are lipids?

Molecules that are insoluble in water, found in our diet and foods.

What are triglycerides?

3 fatty acids linked to a glycerol backbone.