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Quiz about Lipids in Biochemistry I
Quiz about Lipids in Biochemistry I

Lipids in Biochemistry I Trivia Quiz


Lipids form a huge part of biochemistry and this quiz looks at just ten aspects of these biomolecules.

A multiple-choice quiz by doublemm. Estimated time: 6 mins.
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Author
doublemm
Time
6 mins
Type
Multiple Choice
Quiz #
360,780
Updated
Dec 03 21
# Qns
10
Difficulty
Tough
Avg Score
6 / 10
Plays
702
Last 3 plays: Guest 149 (4/10), Guest 180 (6/10), 4331D (4/10).
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Question 1 of 10
1. Fat is important as a storage molecule. It can provide protection to vital organs as well as warmth. As what form are lipids most commonly stored? Hint


Question 2 of 10
2. Fatty acids are long chains containing carbon and hydrogen and form part of several classes of lipid. These fatty acids are defined by the number of carbons in their chain, and this number is invariably an even number. This is because fatty acids are derived from 2-carbon units. These units are themselves derived from which molecule? Hint


Question 3 of 10
3. Lipids are useful as an energy source when glucose is scarce. Specifically, fatty acids undergo a process known as beta oxidation in order to generate energy. Where does beta oxidation take place in our cells? Hint


Question 4 of 10
4. One class of lipid - the phospholipid - is the main constituent of our cell membranes. Our cell membranes exist as bilayers, and phospholipids are able to form these bilayers because they possess both hydrophilic (the phosphate group) and hydrophobic (the fatty acids chains) components. What term is used to define this quality of the phospholipid? Hint


Question 5 of 10
5. Biochemical reactions and transporter proteins are involved in modifying the phospholipids in our membranes. These modifications are important in membrane structure, since different phospholipids have different shapes. Generally, a phospholipid can be described as either a cone, an inverted cone, or which other shape? Hint


Question 6 of 10
6. Another lipid called phosphatidylinositol (PI) is important in cell signalling. It can be phosphorylated to form PIP3, which acts as a docking site for several proteins which promote cell survival. While addition of phosphate is important for regulating this function, phosphate removal is also key. What name is given to a protein which removes phosphate groups? Hint


Question 7 of 10
7. The shape and character of the phospholipid bilayer helps to recruit dynamin, which binds to the membrane and contracts. What process is dynamin directly involved in? Hint


Question 8 of 10
8. Diabetes has long been thought of as a sugar-related disease, but the role of lipids are becoming more and more apparent. Which of the following is true of lipids? Hint


Question 9 of 10
9. The function of a protein in a cell is often dependent on its localisation. What name is given to the lipid chains which attach proteins such as small GTPases to the plasma membrane of the cell? Hint


Question 10 of 10
10. Estrogen research is an intriguing area and the role of this hormone in age-related disorders is becoming more and more realised. Which lipid molecule is an important precursor for the synthesis of estrogen and many other hormones? Hint



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Most Recent Scores
Oct 15 2024 : Guest 149: 4/10
Sep 21 2024 : Guest 180: 6/10
Sep 10 2024 : 4331D: 4/10

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quiz
Quiz Answer Key and Fun Facts
1. Fat is important as a storage molecule. It can provide protection to vital organs as well as warmth. As what form are lipids most commonly stored?

Answer: Triacylglycerides

Triacylglycerides (triglycerides) are stored in adipose cells. Adipose tissue is what makes us appear "fat" in the eyes of others. It is commonly told that we have a set number of adipose cells, and that fluctuations in our body fat are due to variation in the amount of fat stored in each cell, rather than their number.

These stores are used as energy reserves (more on this later), for warmth, and for protection (fat is a good shock absorber and lines vital organs). Lipids can perform more specialised functions also - for example, the waxy covering of some leaves makes them largely waterproof.
2. Fatty acids are long chains containing carbon and hydrogen and form part of several classes of lipid. These fatty acids are defined by the number of carbons in their chain, and this number is invariably an even number. This is because fatty acids are derived from 2-carbon units. These units are themselves derived from which molecule?

Answer: Acetyl Co-enzyme A

Acetyl Co-enzyme A (acetyl CoA) is an important molecule in biochemistry and is a product of glucose metabolism. Indeed, the amount of acetyl CoA in a cell acts as an indicator of the cell's own metabolic state. Lots of acetyl CoA is suggestive of lots of glucose metabolism and, hence, plentiful glucose.

A molecule known as malonyl CoA, which is derived from acetyl CoA and which is the direct precursor of fatty acid chains, directly inhibits fatty acid oxidation. In doing this, the use of lipid as a fuel is inhibited when glucose is abundant. Conversely, when glucose (and therefore acetyl CoA) is scarce, fatty acids are utilised as a fuel source.
3. Lipids are useful as an energy source when glucose is scarce. Specifically, fatty acids undergo a process known as beta oxidation in order to generate energy. Where does beta oxidation take place in our cells?

Answer: Mitochondria

In the cytosol, fatty acids (also known as acyl chains) are "activated" by having a coenzyme A attached to them. This makes the fatty acid (now referred to as acyl CoA) a suitable candidate for the carnatine shuttle system, which transports it from the cytosol to the mitochondria.

This acyl CoA is here converted to acetyl CoA - this is beta oxidation - which can then enter the citric acid cycle, eventually yielding energy.
4. One class of lipid - the phospholipid - is the main constituent of our cell membranes. Our cell membranes exist as bilayers, and phospholipids are able to form these bilayers because they possess both hydrophilic (the phosphate group) and hydrophobic (the fatty acids chains) components. What term is used to define this quality of the phospholipid?

Answer: Amphipathicity

Life may have first been thought to spring to life (for want of a better word) after molecules arose that were capable of replication. This refers to nucleic acid (e.g. RNA and DNA). A dichotomy exists in that nucleic acids are fragile and cannot exist without the protective cell.

However, the cell is made up of components that only exist because the DNA codes for them. How can this paradox be resolved? Lipids are not coded for by DNA, and pre-existed nucleic acid. Amphipathic lipids spontaneously form bilayers (or single-layered entities called micelles) due to the hydrophobic effect.

It was these pre-existing (non-living) lipid shells that may have been hijacked by nucleic acids, eventually morphing into what we recognise today as cells.
5. Biochemical reactions and transporter proteins are involved in modifying the phospholipids in our membranes. These modifications are important in membrane structure, since different phospholipids have different shapes. Generally, a phospholipid can be described as either a cone, an inverted cone, or which other shape?

Answer: Cylindrical

A phospholipid is a glycerol molecule which has two fatty acids chains ligated to it. A phosphate group is also ligated to the glycerol, and it is this phosphate group that is modified. Variations include phosphatidylcholine, phosphatidylserine, and phosphatidylethanolamine. Mercifully, these are usually denoted by PC, PS, and PE, respectively.

Their shape is important in generating the correct type of curvature in the membrane. Additionally, the headgroups may be chemically interesting in that they can be charged (positive or negative), involved in signalling, or be pro-apoptotic (i.e. induce cell death).
6. Another lipid called phosphatidylinositol (PI) is important in cell signalling. It can be phosphorylated to form PIP3, which acts as a docking site for several proteins which promote cell survival. While addition of phosphate is important for regulating this function, phosphate removal is also key. What name is given to a protein which removes phosphate groups?

Answer: A phosphatase

While phospahtases remove phosphate groups, kinases add them. In the case of PI, PI3K (PI-3 kinase) is the major kinase, and PTEN is the major phosphatase. The activities of PI3K and PTEN are tightly regulated and dysregulation in this system is often implicated in cancer. PIP3 binds proteins with a so-called plecstrin homology domain.

This includes protein kinase B, which has a plethora of targets within the cell. For example, protein kinase B inhibits proteins which induce apoptosis and so promotes cell survival.
7. The shape and character of the phospholipid bilayer helps to recruit dynamin, which binds to the membrane and contracts. What process is dynamin directly involved in?

Answer: Vesicular budding

Vesicular budding is a major form of transport within the cell. It packages proteins and other substances into membrane-bound vesicles which can then fuse with other compartments of the cell, releasing the cargo. Dynamin is a GTPase - it hydrolyses GTP, which is similar to ATP - and binds to highly curved membrane regions that possess PIP3 (discussed in the II section of the previous question). Specifically, dynamin is involved in vesicular budding that is promoted by the molecule clathrin. Other types of vesicular budding (for example those mediated by COPI or COPII proteins) do not tend to use dynamin.
8. Diabetes has long been thought of as a sugar-related disease, but the role of lipids are becoming more and more apparent. Which of the following is true of lipids?

Answer: Lipid deposits kill pancreatic cells, reducing insulin production

Lipids play an essential and subtle role in insulin secretion and, therefore, in the pathology of diabetes. Certain lipids such as free fatty acids actually induce insulin secretion from pancreatic cells in normal circumstances, but an excess of these molecules can induce apoptosis of the pancreatic cells and so reduce the ability to produce insulin. For more information on the molecular basis of diabetes, please play my quiz "Keeping an Eye on Your Blood Sugar".
9. The function of a protein in a cell is often dependent on its localisation. What name is given to the lipid chains which attach proteins such as small GTPases to the plasma membrane of the cell?

Answer: A lipid anchor

Prenylation is a term used to describe the attachment of hydrophobic groups to proteins, such as the attachment of a farnesyl or geranyl group (both lipids), which can then link the associated protein to the plasma membrane. The benefit of this localisation is that certain proteins are in close proximity to one another and so can communicate rapidly upon receiving the appropriate stimulus.
10. Estrogen research is an intriguing area and the role of this hormone in age-related disorders is becoming more and more realised. Which lipid molecule is an important precursor for the synthesis of estrogen and many other hormones?

Answer: Cholesterol

Cholesterol is usually referred to as either good (high density) or bad (low or very low density). Despite this, it is generally seen as a bad thing, since its levels are elevated in many human beings. This stigma is undeserved however, as cholesterol is an important component of our cell membranes and we would quickly die without it.

It forms the basis for the synthesis of several hormones such as testosterone and estrogen. Estrogen in particular has been shown in recent years to contribute to wound repair and its reduction following menopause is believed to be the primary cause of related diseases such as osteoporosis.
Source: Author doublemm

This quiz was reviewed by FunTrivia editor WesleyCrusher before going online.
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