MCAT · Biology 1 · Chapter 1 · Section 1.3

Chapter 1: Biological Molecules and Enzymes

Section 1.3: Lipids

STUDY

Question 1:
While the types of lipids are characterized by structures and functional groups, they all share 2 defining characteristics which are _____ and _____.
→ Low solubility in water
     High solubility in non-polar organic solvents

Question 2:
Are lipids hydrophilic or hydrophobic, polar or non-polar?
→ Hydrophobic, non-polar

Question 3:
Name 4 major roles of lipids and which type plays which role. Also, briefly explain how lipids have these roles.
→ Energy storage, thermal insulation, and padding
     Triacylglycerols
     Because lipids have long carbon chains
→ Cellular organization and structure, particularly in membrane
     Phospholipids
     Because lipids are hydrophobic and assemble into barriers separating aqueous environments
→ Provision of precursor molecules for vitamins and hormones
     Some fatty acids (eicosanoids)
     Because lipids can pass through cellular membranes, both of which are hydrophobic
→ Regulation of metabolic activities
     Steroids

Question 4:
Name 7 major groups of lipids and give an example for each.
→ Fatty acids: omega-3 (found in fish, algae, some plants, and nut oils)
     Triacylglycerols: triglyceride
     Phospholipids: phosphatidylcholine
     Glycolipids: galactocerebroside
     Sphingolipids: sphingosine
     Steroids: cholesterol
     Terpenes: vitamin A₁

     Waxes: palmityl palmitate

Question 5:
Fatty acids act as fuel for the body via _____ reaction.
→ Oxidation

Question 6:
Name 3 complex lipids of membrane that have fatty acids as their building blocks.
→ Phospholipids
     Glycolipids
     Sphingolipids

Question 7:
Fatty acids are composed of _____.
→ Long carbon chains truncated at 1 end by a carboxylic acid

Question 8:
Each fatty acid chain contains an _____ (even or odd) number of carbons.
→ Even

Question 9:
Name 2 subcategories of fatty acids and briefly describe their components.
→ Saturated: only C-C single bonds
     Unsaturated: one or more C=C double bonds

Question 10:
High concentration of _____ bonds in fatty acids allows them to store more energy per gram than any other macromolecules in the body.
→ C-H

Question 11:
Most fats reach the cell in the form of _____ which are _____ (components) rather than as _____ which are _____ (components).
→ Free fatty acids
     Fatty acid chains not attached to a backbone
     Triacylglycerols
     3 fatty acid chains attached to a 3-carbon backbone called glycerol

Question 12:
Triacylglycerols, phospholipids, and glycolipids are sometimes referred to as _____.
→ Fatty acids

Question 13:
_____ are the building blocks of phospholipids, glycolipids, and sphingolipids.
→ Fatty acids

Question 14:
Triacylglycerols are also known as _____ or _____.
→ Triglycerides
     Fats and oils

Question 15:
Triacylglycerols are composed of a _____-carbon (number) _____ backbone attached to _____ (number) fatty acid chains. 3 functions of triacylglycerols are _____.
→ 3
     Glycerol
     3
     Energy storage, thermal insulation, and padding

Question 16:
Adipocytes are specialized fat cells whose cytoplasm contains almost nothing but _____.
→ Triacylglycerols (AKA triglycerides)

Question 17:
Phospholipids are lipids attached to a _____ group.
→ Phosphate

Question 18:
The most important phospholipids are _____.
→ Phosphoglycerides

Question 19:
The simplest phosphoglyceride is _____.
→ Phosphatidic acid

Question 20:
Except phosphatidic acid, all other phosphoglycerides have a phosphatidic acid backbone, which is a _____ backbone attached to a _____ group. This characteristic allows these phosphoglycerides to be referred to ask _____.
→ Glycerol
     Phosphate
     Phosphatids

Question 21:
Triacylglycerols (AKA _____) are composed of a _____-carbon (number) backbone called _____ attached to _____ (number) fatty acid chains, whereas phosphoglycerides are composed of a _____ backbone attached to _____ (number) fatty acid chains because _____.
→ Triglycerides
     3
     Glycerol
     3
     Glycerol
     2
     A polar phosphate group replaces 1 of the fatty acid chains

Question 22:
In a phosphoglyceride, the phosphate group lies on the _____ (same or opposite) site of the glycerol from the fatty acids, making the phospholipid _____ (polar or non-polar) at the phosphate end and _____ (polar or non-polar) at the fatty acid end.
→ Opposite
     Polar
     Non-polar

Question 23:
Molecules that have polar and non-polar ends are referred to as _____.
→ Amphipathic

Question 24:
When forming bilayer membranes, the _____ (polar or non-polar, heads or tails) of phospholipids face toward the watery environment within and outside the cell, while the _____ (polar or non-polar, heads or tails) create an inner layer within the membrane. Generally, the lipid bilayer has _____ (high or low) permeability to polar molecules and _____ (high or low) permeability to non-polar molecules. In other words, the lipid bilayer is _____.
→ Polar heads
     Non-polar tails
     Low
     High
     Semi-permeable

Question 25:
Polar molecules are water-_____ (soluble or insoluble) and fat-_____ (soluble or insoluble), whereas non-polar molecules are fat-_____ (soluble or insoluble) and water-_____ (soluble or insoluble).
→ Soluble
     Insoluble
     Soluble
     Insoluble

Question 26:
Phosphoglycerides are composed of a _____-carbon (number) _____ backbone attached to _____ (number) fatty acid chains because _____, whereas glycolipids are composed of a _____ backbone attached to one or more _____ instead of to the _____.
→ 3
     Glycerol
     2
     A polar phosphate group replaces 1 of the fatty acid chains
     Glycerol
     Carbohydrates
     Phosphate group

Question 27:
Both phospholipids and glycolipids have polar ends and non-polar ends, making them _____.
→ Amphipathic

Question 28:
Glycolipids are abundant in membranes of _____ cells in human nervous system.
→ Myelinated

Question 29:
Phosphoglycerides are composed of a _____ backbone attached to _____ (number) fatty acid chains because _____, whereas sphingolipids are composed of a _____ backbone attached to _____ (number) fatty acid chain.
→ Glycerol
     2
     A polar phosphate group replaces 1 of the fatty acid chains
     Sphingosine
     1

Question 30:
In a sphingolipid, the sphingosine backbone molecule is an _____.
→ Amino alcohol

Question 31:
Phospholipids, glycolipids, steroids, and sphingolipids make up part of the cell's _____.
→ Membrane

Question 32:
Steroids are a _____-ringed (number) structure. 4 examples of steroids are _____.
→ 4
     Membrane component, hormones, vitamin D, and cholesterol

Question 33:
Terpenes are often part of _____ in the body. 1 example of terpenes is _____ which is important for _____.
→ Pigments
     Vitamin A
     Vision

Question 34:
Waxes are formed by _____ linkage between a long-chain _____ and a long-chain _____. 1 example of waxes  in the human body is _____.
→ Ester
     Alcohol
     Fatty acid
     Ear wax

Question 35:
A characteristic texture of waxes is _____.
→ Water-repellence

Question 36:
A minor group of lipids is eicosanoids, which includes _____, _____, and _____.
→ Prostaglandins
     Thromboxanes
     Leukotrienes

Question 37:
Eicosanoids are released from cell membranes as local _____ that regulate, among other things, _____, _____, and _____.
→ Hormones
     Blood pressure
     Body temperature
     Smooth muscle contraction

Question 38:
_____ is a commonly used inhibitor of prostaglandin synthesis.
→ Aspirin

Question 39:
Because lipids are _____ (soluble or insoluble) in aqueous solution, they're transported in the blood via _____.
→ Insoluble
     Lipoproteins

Question 40:
Lipoprotein contains a _____ core surrounded by _____ and _____. Thus, the lipoprotein is able to dissolve lipids in its _____ (hydrophobic or hydrophilic) core and then move freely through the aqueous solution due to its _____ (hydrophobic or hydrophilic) shell.

(Source: https://www.mabtech.com/sites/default/files/apolipoprotein-detail_2.png)

→ Lipid
     Phospholipids
     Apoproteins
     Hydrophobic
     Hydrophilic

Question 41:
Lipoproteins are classified by their density. The greater the ratio of lipid to protein, the _____ (lower or higher) the density.
→ Lower

Question 42:
Because proteins weigh more than an equivalent volume of lipids, the greater the ratio of protein to lipid, the _____ (greater or lesser) the density of that lipoprotein.
→ Greater

Question 43:
Name 4 major classes of lipoproteins.
→ Chylomicrons
     Very low density lipoproteins (VLDL)
     Low density lipoproteins (LDL)
     High density lipoproteins (HDL)

Question 44:
Vitamins are a particular type of _____ (organic or inorganic) molecule that are essential. Being essential means that they _____ (can or cannot) be produced by the body. Vitamin _____ (letter) and vitamin _____ (letter) are examples of fat-soluble vitamins. Fat-soluble vitamins are transported in the body along with _____ (proteins, carbohydrates, fats, or nucleic acids) obtained from the diet, and also _____ (assist or hinder) the absorption of these macromolecules.
→ Organic
     Cannot
     A
     D
     Fats
     Assist

PRACTICE

Question 1:
While the types of lipids are characterized by structures and functional groups, they all share 2 defining characteristics which are _____ and _____.

Question 2:
Are lipids hydrophilic or hydrophobic, polar or non-polar?

Question 3:
Name 4 major roles of lipids and which type plays which role. Also, briefly explain how lipids have these roles.

Question 4:
Name 7 major groups of lipids and give an example for each.

Question 5:
Fatty acids act as fuel for the body via _____ reaction.

Question 6:
Name 3 complex lipids of membrane that have fatty acids as their building blocks.

Question 7:
Fatty acids are composed of _____.

Question 8:
Each fatty acid chain contains an _____ (even or odd) number of carbons.

Question 9:
Name 2 subcategories of fatty acids and briefly describe their components.

Question 10:
High concentration of _____ bonds in fatty acids allows them to store more energy per gram than any other macromolecules in the body.

Question 11:
Most fats reach the cell in the form of _____ which are _____ (components) rather than as _____ which are _____ (components).

Question 12:
Triacylglycerols, phospholipids, and glycolipids are sometimes referred to as _____.

Question 13:
_____ are the building blocks of phospholipids, glycolipids, and sphingolipids.

Question 14:
Triacylglycerols are also known as _____ or _____.

Question 15:
Triacylglycerols are composed of a _____-carbon _____ backbone attached to _____ (number) fatty acid chains. 3 functions of triacylglycerols are _____.

Question 16:
Adipocytes are specialized fat cells whose cytoplasm contains almost nothing but _____.

Question 17:
Phospholipids are lipids attached to a _____ group.

Question 18:
The most important phospholipids are _____.

Question 19:
The simplest phosphoglyceride is _____.

Question 20:
Except phosphatidic acid, all other phosphoglycerides have a phosphatidic acid backbone, which is a _____ backbone attached to a _____ group. This characteristic allows these phosphoglycerides to be referred to ask _____.

Question 21:
Triacylglycerols (AKA _____) are composed of a _____-carbon (number) backbone called _____ attached to _____ (number) fatty acid chains, whereas phosphoglycerides are composed of a _____ backbone attached to _____ (number) fatty acid chains because _____.

Question 22:
In a phosphoglyceride, the phosphate group lies on the _____ (same or opposite) site of the glycerol from the fatty acids, making the phospholipid _____ (polar or non-polar) at the phosphate end and _____ (polar or non-polar) at the fatty acid end.

Question 23:
Molecules that have polar and non-polar ends are referred to as _____.

Question 24:
When forming bilayer membranes, the _____ (polar or non-polar, heads or tails) of phospholipids face toward the watery environment within and outside the cell, while the _____ (polar or non-polar, heads or tails) create an inner layer within the membrane. Generally, the lipid bilayer has _____ (high or low) permeability to polar molecules and _____ (high or low) permeability to non-polar molecules. In other words, the lipid bilayer is _____.

Question 25:
Polar molecules are water-_____ (soluble or insoluble) and fat-_____ (soluble or insoluble), whereas non-polar molecules are fat-_____ (soluble or insoluble) and water-_____ (soluble or insoluble).

Question 26:
Phosphoglycerides are composed of a _____-carbon (number) _____ backbone attached to _____ (number) fatty acid chains because _____, whereas glycolipids are composed of a _____ backbone attached to one or more _____ instead of to the _____.

Question 27:
Both phospholipids and glycolipids have polar ends and non-polar ends, making them _____.

Question 28:
Glycolipids are abundant in membranes of _____ cells in human nervous system.

Question 29:
Phosphoglycerides are composed of a _____ backbone attached to _____ (number) fatty acid chains because _____, whereas sphingolipids are composed of a _____ backbone attached to _____ (number) fatty acid chain.

Question 30:
In a sphingolipid, the sphingosine backbone molecule is an _____.

Question 31:
Phospholipids, glycolipids, steroids, and sphingolipids make up part of the cell's _____.

Question 32:
Steroids are a _____-ringed (number) structure. 4 examples of steroids are _____.

Question 33:
Terpenes are often part of _____ in the body. 1 example of terpenes is _____ which is important for _____.

Question 34:
Waxes are formed by _____ linkage between a long-chain _____ and a long-chain _____. 1 example of waxes  in the human body is _____.

Question 35:
A characteristic texture of waxes is _____.

Question 36:
A minor group of lipids is eicosanoids, which includes _____, _____, and _____.

Question 37:
Eicosanoids are released from cell membranes as local _____ that regulate, among other things, _____, _____, and _____.

Question 38:
_____ is a commonly used inhibitor of prostaglandin synthesis.

Question 39:
Because lipids are _____ (soluble or insoluble) in aqueous solution, they're transported in the blood via _____.

Question 40:
Lipoprotein contains a _____ core surrounded by _____ and _____. Thus, the lipoprotein is able to dissolve lipids in its _____ (hydrophobic or hydrophilic) core and then move freely through the aqueous solution due to its _____ (hydrophobic or hydrophilic) shell.

(Source: https://www.mabtech.com/sites/default/files/apolipoprotein-detail_2.png)

Question 41:
Lipoproteins are classified by their density. The greater the ratio of lipid to protein, the _____ (lower or higher) the density.

Question 42:
Because proteins weigh more than an equivalent volume of lipids, the greater the ratio of protein to lipid, the _____ (greater or lesser) the density of that lipoprotein.

Question 43:
Name 4 major classes of lipoproteins.

Question 44:
Vitamins are a particular type of _____ (organic or inorganic) molecule that are essential. Being essential means that they _____ (can or cannot) be produced by the body. Vitamin _____ (letter) and vitamin _____ (letter) are examples of fat-soluble vitamins. Fat-soluble vitamins are transported in the body along with _____ (proteins, carbohydrates, fats, or nucleic acids) obtained from the diet, and also _____ (assist or hinder) the absorption of these macromolecules.

ANSWER KEY

Question 1:
→ Low solubility in water
     High solubility in non-polar organic solvents

Question 2:
→ Hydrophobic, non-polar

Question 3:
→ Energy storage, thermal insulation, and padding
     Triacylglycerols
     Because lipids have long carbon chains
→ Cellular organization and structure, particularly in membrane
     Phospholipids
     Because lipids are hydrophobic and assemble into barriers separating aqueous environments
→ Provision of precursor molecules for vitamins and hormones
     Some fatty acids (eicosanoids)
     Because lipids can pass through cellular membranes, both of which are hydrophobic
→ Regulation of metabolic activities
     Steroids

Question 4:
→ Fatty acids: omega-3 (found in fish, algae, some plants, and nut oils)
     Triacylglycerols: triglyceride
     Phospholipids: phosphatidylcholine
     Glycolipids: galactocerebroside
     Sphingolipids: sphingosine
     Steroids: cholesterol
     Terpenes: vitamin A₁

     Waxes: palmityl palmitate

Question 5:
→ Oxidation

Question 6:
→ Phospholipids
     Glycolipids
     Sphingolipids

Question 7:
→ Long carbon chains truncated at 1 end by a carboxylic acid

Question 8:
→ Even

Question 9:
→ Saturated: only C-C single bonds
     Unsaturated: one or more C=C double bonds

Question 10:
→ C-H

Question 11:
→ Free fatty acids
     Fatty acid chains not attached to a backbone
     Triacylglycerols
     3 fatty acid chains attached to a 3-carbon backbone called glycerol

Question 12:
→ Fatty acids

Question 13:
→ Fatty acids

Question 14:
→ Triglycerides
     Fats and oils

Question 15:
→ 3
     Glycerol
     3
     Energy storage, thermal insulation, and padding

Question 16:
→ Triacylglycerols (AKA triglycerides)

Question 17:
→ Phosphate

Question 18:
→ Phosphoglycerides

Question 19:
→ Phosphatidic acid

Question 20:
→ Glycerol
     Phosphate
     Phosphatids

Question 21:
→ Triglycerides
     3
     Glycerol
     3
     Glycerol
     2
     A polar phosphate group replaces one of the fatty acid chains

Question 22:
→ Opposite
     Polar
     Non-polar

Question 23:
→ Amphipathic

Question 24:
→ Polar heads
     Non-polar tails
     Low
     High
     Semi-permeable

Question 25:
→ Soluble
     Insoluble
     Soluble
     Insoluble

Question 26:
→ 3
     Glycerol
     2
     A polar phosphate group replaces 1 of the fatty acid chains
     Glycerol
     Carbohydrates
     Phosphate group

Question 27:
→ Amphipathic

Question 28:
→ Myelinated

Question 29:
→ Glycerol
     2
     A polar phosphate group replaces 1 of the fatty acid chains
     Sphingosine
     1

Question 30:
→ Amino alcohol

Question 31:
→ Membrane

Question 32:
→ 4
     Membrane component, hormones, vitamin D, and cholesterol

Question 33:
→ Pigments
     Vitamin A
     Vision

Question 34:
→ Ester
     Alcohol
     Fatty acid
     Ear wax

Question 35:
→ Water-repellence

Question 36:
→ Prostaglandins
     Thromboxanes
     Leukotrienes

Question 37:
→ Hormones
     Blood pressure
     Body temperature
     Smooth muscle contraction

Question 38:
→ Aspirin

Question 39:
→ Insoluble
     Lipoproteins

Question 40:
→ Lipid
     Phospholipids
     Apoproteins
     Hydrophobic
     Hydrophilic

Question 41:
→ Lower

Question 42:
→ Greater

Question 43:
→ Chylomicrons
     Very low density lipoproteins (VLDL)
     Low density lipoproteins (LDL)
     High density lipoproteins (HDL)

Question 44:
→ Organic
     Cannot
     A
     D
     Fats
     Assist