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Total Categories: 6
Cholesterol is primarily synthesized in plant tissues and is only found in trace amounts in animals.
Answer: False
Cholesterol is the principal sterol found in all animals and is synthesized from acetyl-CoA. It is not primarily synthesized in plant tissues.
François Poulletier de la Salle identified cholesterol in gallstones in the late 18th century.
Answer: True
François Poulletier de la Salle first identified cholesterol in solid form within gallstones in 1769.
The term 'cholesterol' derives from Greek roots signifying 'solid bile alcohol'.
Answer: True
The word 'cholesterol' originates from the Ancient Greek words 'chole' (bile) and 'stereos' (solid), with the suffix '-ol' indicating its chemical nature as an alcohol.
Konrad Bloch and Feodor Lynen received a Nobel Prize for their research on cholesterol metabolism.
Answer: True
Konrad Bloch and Feodor Lynen were awarded the Nobel Prize in Physiology or Medicine in 1964 for their discoveries concerning the mechanisms and regulation of cholesterol and fatty acid metabolism.
The naturally occurring form of cholesterol with biochemical significance is called *ent*-cholesterol.
Answer: False
The naturally occurring form of cholesterol with biochemical significance is *nat*-cholesterol; *ent*-cholesterol is its enantiomer.
The word 'cholesterol' originates from Greek words for 'bile' and 'solid', reflecting its discovery context.
Answer: True
The term 'cholesterol' is derived from the Greek 'chole' (bile) and 'stereos' (solid), reflecting its initial isolation from gallstones.
According to biochemical sources, where is cholesterol predominantly found within animal organisms?
Answer: Distributed throughout the body's tissues, particularly concentrated in the brain and animal fats.
Cholesterol is the principal sterol in all animals, found distributed throughout tissues, with notable concentrations in the brain and spinal cord, as well as in animal fats and oils.
In what substance was cholesterol first identified by François Poulletier de la Salle?
Answer: Gallstones
François Poulletier de la Salle first identified cholesterol in solid form within gallstones in 1769.
The word 'cholesterol' is derived from Greek roots 'chole' (bile) and 'stereos' (solid), with the suffix '-ol' indicating its chemical nature as:
Answer: An alcohol
The suffix '-ol' in 'cholesterol' indicates its chemical classification as an alcohol, derived from the Greek roots 'chole' (bile) and 'stereos' (solid).
Konrad Bloch and Feodor Lynen received the Nobel Prize for their research concerning:
Answer: The regulation of cholesterol and fatty acid metabolism.
Konrad Bloch and Feodor Lynen were awarded the Nobel Prize for their seminal work elucidating the mechanisms and regulation of cholesterol and fatty acid metabolism.
What is a primary physiological role of cholesterol within animal cell membranes?
Answer: True
Cholesterol is an essential component of animal cell membranes, critically regulating membrane fluidity across varying temperatures and contributing to structural integrity.
Cholesterol is non-essential for animal life due to its limited role in cell membranes.
Answer: False
Cholesterol is essential for all animal life, serving as a fundamental component of cell membranes that regulates fluidity and maintains structural integrity.
Cholesterol's interaction with phospholipids increases membrane fluidity, making cells excessively rigid.
Answer: False
Cholesterol modulates membrane fluidity, increasing it at low temperatures and decreasing it at high temperatures, thereby maintaining structural integrity without making cells excessively rigid.
Phospholipase D2 (PLD2) activity is independent of cholesterol levels in cell membranes.
Answer: False
Phospholipase D2 (PLD2) activity is known to be influenced by cholesterol levels and its presence in cholesterol-dependent lipid domains within the cell membrane.
Cholesterol is crucial for cell signaling because it helps form lipid rafts that concentrate signaling molecules.
Answer: True
Cholesterol contributes to cell signaling by facilitating the formation of lipid rafts, specialized membrane microdomains that concentrate signaling proteins and receptors.
Cholesterol constitutes a small fraction of the epidermal lipid matrix.
Answer: False
Cholesterol is a major component of the epidermal lipid matrix, constituting approximately 25% by weight, and is crucial for the skin's barrier function.
Cholesterol contributes to the skin's barrier function by preventing excessive water loss.
Answer: True
In the epidermis, cholesterol is a key component of the lipid matrix, forming part of a barrier that is essential for preventing transepidermal water loss.
The myelin sheath, rich in cholesterol, insulates nerve fibers to improve impulse transmission.
Answer: True
The myelin sheath, a lipid-rich layer abundant in cholesterol, acts as an electrical insulator around nerve fibers, thereby enhancing the speed and efficiency of nerve impulse conduction.
Cholesterol reduces the permeability of the plasma membrane to small, uncharged molecules.
Answer: True
By increasing the packing density of the lipid bilayer, cholesterol reduces the permeability of the plasma membrane to small, uncharged molecules.
Cholesterol is primarily found in the cell nucleus.
Answer: False
Cholesterol is primarily found in cell membranes, where it plays a critical role in regulating fluidity and integrity, not predominantly in the cell nucleus.
Cholesterol is a key component of the epidermal lipid matrix, making up about 50% of it.
Answer: False
While cholesterol is a key component of the epidermal lipid matrix, it constitutes approximately 25% by weight, not 50%.
Cholesterol is primarily found in the cell membrane, regulating its fluidity.
Answer: True
Cholesterol is a key component of the cell membrane, where it plays a crucial role in modulating membrane fluidity and maintaining structural integrity.
The myelin sheath, vital for nerve impulse transmission, contains significant amounts of cholesterol.
Answer: True
The myelin sheath, which insulates nerve fibers to facilitate efficient impulse transmission, is notably rich in cholesterol.
What is a primary physiological role of cholesterol within animal cell membranes?
Answer: To regulate membrane fluidity and maintain structural integrity.
Cholesterol is an essential component of animal cell membranes, critically regulating membrane fluidity across varying temperatures and contributing to structural integrity.
Why is cholesterol considered essential for all animal life?
Answer: It is a fundamental component of cell membranes, regulating fluidity and integrity.
Cholesterol is essential for all animal life because it is a fundamental component of cell membranes, contributing to their structural integrity and regulating their fluidity, which is vital for cellular function.
Cholesterol's integration into cell membranes primarily serves to:
Answer: Modulate fluidity and enhance stability across temperatures.
Cholesterol integrates into cell membranes to modulate fluidity and enhance stability across a range of temperatures, contributing to overall membrane integrity.
Which enzyme's activity is influenced by cholesterol levels and its presence in cholesterol-dependent lipid domains?
Answer: Phospholipase D2 (PLD2)
Phospholipase D2 (PLD2) activity is influenced by cholesterol levels and its localization within cholesterol-dependent lipid domains in the cell membrane.
Cholesterol contributes to cell signaling by facilitating the formation of:
Answer: Lipid rafts
Cholesterol plays a role in cell signaling by contributing to the formation of lipid rafts, which serve as platforms for concentrating signaling molecules.
In the epidermal lipid matrix, what is the approximate proportion of cholesterol by weight?
Answer: 25%
Cholesterol constitutes approximately 25% by weight of the epidermal lipid matrix, contributing significantly to the skin's barrier function.
How does cholesterol contribute to the skin's barrier function?
Answer: By forming part of the lipid matrix that prevents water loss.
In the epidermis, cholesterol is a key component of the lipid matrix, forming part of a barrier that is essential for preventing transepidermal water loss.
The myelin sheath's role in efficient nerve impulse transmission is primarily due to its function as:
Answer: An electrical insulator rich in cholesterol.
The myelin sheath, which is rich in cholesterol, acts as an electrical insulator around nerve fibers, thereby enhancing the speed and efficiency of nerve impulse conduction.
In vertebrates, the primary site of cholesterol production is the brain.
Answer: False
In vertebrates, hepatic cells (liver cells) are the primary site of cholesterol production, not the brain. While astrocytes in the brain synthesize cholesterol locally for neurons, the liver produces the largest quantities.
Cholesterol synthesized by astrocytes in the brain is distributed to neurons for their metabolic needs.
Answer: True
Astrocytes, a type of glial cell in the brain, synthesize cholesterol locally and then distribute it to neurons, ensuring their requirements are met.
The mevalonate pathway is significant in cholesterol biosynthesis primarily because it represents the initial, rate-limiting, and irreversible stage.
Answer: True
The mevalonate pathway is crucial as it represents the initial, rate-limiting, and irreversible steps in cholesterol synthesis, making it a primary target for cholesterol-lowering drugs like statins.
A 68 kg human male synthesizes approximately 10 grams of cholesterol daily.
Answer: False
A typical human male weighing approximately 68 kg synthesizes about 1 gram (1,000 mg) of cholesterol daily, not 10 grams.
The body increases its own cholesterol synthesis when dietary cholesterol intake is high.
Answer: False
The body typically decreases its own cholesterol synthesis in response to high dietary cholesterol intake as a regulatory mechanism.
Almost all animal tissues synthesize cholesterol starting from glucose.
Answer: False
Nearly all animal tissues synthesize cholesterol starting from acetyl-CoA, a fundamental molecule in cellular metabolism, not glucose.
HMG-CoA reductase catalyzes the rate-limiting step in cholesterol synthesis.
Answer: True
The enzyme HMG-CoA reductase catalyzes the production of mevalonate, which is the rate-limiting step in the cholesterol biosynthesis pathway.
SREBP proteins are located in the cell membrane and directly transport cholesterol into the cell.
Answer: False
SREBP proteins are located in the endoplasmic reticulum and act as sensors for intracellular cholesterol levels, regulating synthesis and uptake, but they do not directly transport cholesterol.
Cholesterol synthesis is regulated by SREBP, which is activated when intracellular cholesterol levels are high.
Answer: False
SREBP is activated when intracellular cholesterol levels are low, prompting increased synthesis and uptake of cholesterol. High levels lead to its inactivation.
Statins work by inhibiting the enzyme responsible for the final step of cholesterol synthesis.
Answer: False
Statins inhibit HMG-CoA reductase, which catalyzes the rate-limiting step in cholesterol synthesis (the production of mevalonate), not the final step.
The body's own cholesterol production increases significantly when dietary cholesterol intake is low.
Answer: True
The body regulates endogenous cholesterol synthesis; when dietary intake is low, the body typically increases its own production to maintain homeostasis.
Astrocytes are responsible for producing the majority of cholesterol in the vertebrate liver.
Answer: False
Hepatic cells (liver cells) are responsible for producing the majority of cholesterol in the vertebrate liver. Astrocytes produce cholesterol within the brain.
Which type of cell in vertebrates is responsible for producing the largest quantities of cholesterol?
Answer: Hepatic cells (liver cells)
In vertebrates, hepatic cells, which constitute the liver, are the primary site responsible for producing the largest quantities of cholesterol.
How is cholesterol synthesized and distributed to neurons within the brain?
Answer: Astrocytes synthesize it locally and then distribute it to neurons.
Within the brain, cholesterol is synthesized by astrocytes, a type of glial cell, which then distribute it to neurons, ensuring local availability.
The mevalonate pathway is significant in cholesterol synthesis primarily because:
Answer: It is the initial, rate-limiting, and irreversible stage.
The mevalonate pathway is crucial as it represents the initial, rate-limiting, and irreversible steps in cholesterol synthesis, making it a primary target for cholesterol-lowering drugs like statins.
What is the approximate daily synthesis of cholesterol in a 68 kg human male?
Answer: 1000 mg (1 gram)
A typical human male weighing approximately 68 kg synthesizes about 1 gram (1,000 mg) of cholesterol each day.
How does the body typically adjust its own cholesterol synthesis in response to high dietary cholesterol intake?
Answer: It decreases its own synthesis.
The body typically decreases its own cholesterol synthesis in response to high dietary cholesterol intake as a regulatory mechanism to maintain homeostasis.
Nearly all animal tissues synthesize cholesterol starting from which fundamental molecule?
Answer: Acetyl-CoA
Nearly all animal tissues synthesize cholesterol starting from acetyl-CoA, a fundamental molecule derived from carbohydrate and fatty acid metabolism.
Which enzyme, targeted by statins, catalyzes the rate-limiting step in cholesterol synthesis?
Answer: HMG-CoA reductase
HMG-CoA reductase catalyzes the rate-limiting step in cholesterol synthesis, the conversion of HMG-CoA to mevalonate, and is the primary target of statin medications.
What is the function of the SREBP protein in relation to cholesterol?
Answer: It senses intracellular cholesterol levels and regulates synthesis/uptake.
SREBP proteins act as transcription factors that sense intracellular cholesterol levels and regulate the expression of genes involved in cholesterol synthesis and uptake.
The body recycles cholesterol primarily by excreting it directly into the bloodstream from the liver.
Answer: False
The body recycles cholesterol primarily through excretion into bile, followed by reabsorption from the small intestine, not direct excretion into the bloodstream.
The LDL receptor's primary role is to remove excess cholesterol from peripheral tissues.
Answer: False
The LDL receptor's primary role is to bind LDL particles and facilitate their uptake into cells, thereby removing cholesterol from the bloodstream, not directly from peripheral tissues.
Chylomicrons and VLDL are types of lipoproteins involved in cholesterol transport.
Answer: True
Chylomicrons and Very-low-density lipoproteins (VLDL) are indeed major classes of lipoproteins crucial for the transport of cholesterol and other lipids in the body.
LDL particles are called "good cholesterol" because they help remove cholesterol from arteries.
Answer: False
LDL particles are commonly referred to as "bad cholesterol" due to their association with increased risk of atherosclerosis. HDL particles are associated with removing cholesterol from arteries.
HDL particles are thought to be protective because they transport cholesterol from the liver to peripheral tissues.
Answer: False
HDL particles are considered protective because they facilitate reverse cholesterol transport, moving cholesterol from peripheral tissues back to the liver, not from the liver to tissues.
How does the body primarily recycle cholesterol?
Answer: Through excretion into bile, followed by reabsorption from the small intestine.
Cholesterol is primarily recycled via excretion into bile by the liver, followed by reabsorption from the small intestine, a process known as enterohepatic circulation.
The LDL receptor plays a critical role in cholesterol homeostasis by:
Answer: Binding LDL particles and facilitating their uptake into cells.
The LDL receptor binds to LDL particles circulating in the blood, mediating their endocytosis into cells and thus playing a key role in cholesterol homeostasis.
Which of the following is NOT one of the five main types of lipoproteins involved in cholesterol transport mentioned in the source?
Answer: Albumin
Albumin is a protein found in blood plasma but is not classified as one of the five main types of lipoproteins involved in cholesterol transport (chylomicrons, VLDL, IDL, LDL, HDL).
What is the proposed protective function of HDL particles?
Answer: Facilitating reverse cholesterol transport from tissues back to the liver.
HDL particles are considered protective due to their role in reverse cholesterol transport, which removes excess cholesterol from peripheral tissues and returns it to the liver for excretion.
Cholesterol is a precursor molecule exclusively for vitamin D synthesis.
Answer: False
Cholesterol is a precursor for multiple vital compounds, including all steroid hormones, bile acids, and vitamin D, not exclusively vitamin D.
Cortisol and testosterone are synthesized from cholesterol.
Answer: True
Cholesterol serves as the essential precursor for the synthesis of all steroid hormones, including cortisol and testosterone.
Oxysterols are cholesterol derivatives that stimulate cholesterol biosynthesis.
Answer: False
Oxysterols, which are cholesterol derivatives, are known to inhibit cholesterol biosynthesis, suggesting a feedback regulatory mechanism.
Cholesterol is essential for the formation of steroid hormones like cortisol and aldosterone.
Answer: True
Cholesterol is the fundamental precursor for the synthesis of all steroid hormones, including cortisol and aldosterone produced by the adrenal glands.
Cholesterol serves as a vital precursor for the synthesis of which group of compounds?
Answer: Steroid hormones, bile acids, and vitamin D
Cholesterol is the essential precursor for the synthesis of all steroid hormones, bile acids, and vitamin D.
Which of the following is a key steroid hormone synthesized using cholesterol as a precursor?
Answer: Cortisol
Cortisol is a key steroid hormone synthesized from cholesterol, serving vital functions in metabolism and stress response.
What does the 'oxysterol hypothesis' suggest about oxysterols?
Answer: They inhibit cholesterol biosynthesis.
The 'oxysterol hypothesis' posits that oxysterols, which are oxidized derivatives of cholesterol, can inhibit cholesterol biosynthesis, acting as a feedback mechanism.
High levels of cholesterol bound to HDL are strongly linked to an increased risk of cardiovascular disease.
Answer: False
High levels of cholesterol bound to LDL (low-density lipoprotein) are associated with an increased risk of cardiovascular disease, whereas HDL (high-density lipoprotein) is generally considered protective.
Phytosterols enhance cholesterol absorption in the intestines.
Answer: False
Phytosterols compete with cholesterol for absorption in the intestines, thereby reducing the absorption of cholesterol.
Cholesterol is the primary component of most gallstones.
Answer: True
Cholesterol is indeed the primary constituent of the majority of gallstones, forming when it crystallizes out of bile.
Foods such as red meat, egg yolks, and shellfish are major dietary sources of cholesterol.
Answer: True
Animal-derived foods, including red meat, egg yolks, and shellfish, are recognized as significant dietary sources of cholesterol.
The "lipid hypothesis" suggests that low cholesterol levels are the primary cause of atherosclerosis.
Answer: False
The lipid hypothesis posits that elevated cholesterol levels, particularly LDL cholesterol, contribute to the development of atherosclerosis, not low levels.
The 1987 National Cholesterol Education Program guidelines considered total blood cholesterol levels between 200-239 mg/dL as desirable.
Answer: False
According to the 1987 NCEP guidelines, total blood cholesterol levels between 200-239 mg/dL were classified as 'borderline high,' not desirable.
Hypocholesterolemia refers to abnormally high levels of cholesterol in the blood.
Answer: False
Hypocholesterolemia is a medical term for abnormally low levels of cholesterol in the blood.
A desirable LDL cholesterol level is typically considered to be above 130 mg/dL.
Answer: False
A desirable LDL cholesterol level is typically considered to be below 100 mg/dL, with levels above 130 mg/dL often indicating an elevated risk.
Elevated LDL cholesterol levels are associated with a reduced risk of cardiovascular disease.
Answer: False
Elevated LDL cholesterol levels are strongly associated with an increased risk of cardiovascular disease, whereas HDL cholesterol is considered protective.
An increased risk of cardiovascular disease is associated with which condition?
Answer: Elevated levels of cholesterol bound to LDL.
Elevated levels of cholesterol transported by low-density lipoproteins (LDL) are strongly associated with an increased risk of developing cardiovascular disease.
What effect do phytosterols have on cholesterol absorption in the intestines?
Answer: They compete with cholesterol, reducing its absorption.
Phytosterols compete with cholesterol for absorption in the intestines, thereby reducing the absorption of cholesterol.
Cholesterol is the main component of which common condition?
Answer: Gallstones
Cholesterol is the primary component of most gallstones, forming when it crystallizes out of bile.
Why are LDL particles commonly referred to as "bad cholesterol"?
Answer: High concentrations are linked to the development of atherosclerosis.
LDL particles are commonly termed "bad cholesterol" because elevated blood concentrations are strongly associated with the pathogenesis of atherosclerosis.
Which of the following is a major dietary source of cholesterol?
Answer: Egg yolks
Egg yolks, along with other animal products like red meat and shellfish, are recognized as major dietary sources of cholesterol.
According to the 1987 National Cholesterol Education Program guidelines, what was considered a 'borderline high' total blood cholesterol level?
Answer: 200–239 mg/dL
According to the 1987 NCEP guidelines, total blood cholesterol levels between 200–239 mg/dL were classified as 'borderline high'.
Hypocholesterolemia is a condition characterized by:
Answer: Abnormally low levels of cholesterol in the blood.
Hypocholesterolemia is a medical term referring to abnormally low levels of cholesterol in the blood.