Chapter 5: Lipid Structure and Function Flashcards
Each lipid membrane component is an ____________ molecule, meaning it has both hydrophilic and hydrophobic regions.
amphipathic
Phospholipids contain what elements?
- Polar head group
- Fatty acid tail
What is the polar head group of a phospholipid made of?
- Phosphate
- Alcohol
Phospholipids can be further classified according to the ________ on which the molecule is built.
backbone
What joins the polar head group to the fatty acid tail?
Phosphodiester linkages
What do all lipids share in common?
A tail composed of long-chain fatty acids
The hydrocarbon chains of lipids vary by their degree of ____________ and ________.
separation; length
Fully ____________ fatty acid tails will ahve only single bonds.
saturated
The carbon atom is considered “saturated” when it is bonded to ____ other atoms, with no ____ bonds.
four; pi
Saturated fatty acids have greater____________ forces and a more ________ overall structure.
van der Waals; stable
Saturated fatty acids tend to form ________ at room temperature.
solids
An ____________ fatty acid includes one or more double bonds.
unsaturated
Double bonds introduce kinks into the fatty acid chain, which makes it difficult for what?
For them to stack and solidify
Unsaturated fats tend to be ____________ at room temperature.
liquids
Phospholipids with unsaturated fatty acid tails make up more ________ regions of the phospholipid bilayer.
fluid
Glycerophospholipids (or phosphoglycerides) are specifically those phospholipids that contain a ____________ backbone bonded by ________ linkages to 2 fatty acids and by a phosphodiester linkage to a highly polar head group.
glycerol; ester
Because the ________ group determines membrane surface properties, glycerophosphipids are named according to this.
head
________________ is the name of a glycerophospholipid with a choline head group.
phosphatidylcholine
____________________ is one with an ethanol-amine head group.
phosphatidylethanolamine
The head group of a glycerophospholipid can be ____________ charged, ____________ charged, or ________.
positively, negatively, neutral
The ABO blood typing system is based on cell-surface antigens on RBCs. These cell-surface antigens are some of the most well-known ________________.
sphingolipids
Sphingolipids have a ____________ or ________ backbone, as opposed to the glycerol backbone of glycerophospholipids.
sphingosine, sphingoid
Sphingolipids have long-chain, nonpolar fatty acid tails and polar head groups. Many sphingolipids are also phospholipids because they contain a ________________ linkage.
phosphodiester
Other sphingolipids contain ____________ linkages to sugars; any lipid linked to a sugar can be termed a ____________.
glycosidic; glycolipid
What are the four major subclasses of sphingolipids, as divided by their head group?
- Ceramide
- Sphingomyelins
- Glycosphingolipids (glycolipids)
- Gangliosides
The simplest sphingolipid is ____________, which has a single hydrogen atom as its head group.
ceramide
____________ are the major class of sphingolipids that are also phospholipids.
sphingomyelins
Sphingomyelins have either ____________ or ____________________ as a head group, and thus contain a ________________ bond.
phosphocholine, phosphoethanolamine; phosphodiester
What is the charge of sphingomyeline head groups?
No net charge
Sphingomyelins are major componenets in the plasma membranes of cells producing ____________, the insulating sheath for axons.
myelin
Sphingolipids with head groups composed of sugars bonded by glycosidic linkages are considered ____________, or more specifically, ________________.
glycolipids; glycosphingolipids
Sphingolipids are not phospholipids because they contain no ________________ linkage.
phosphodiester
Glycosphingolipids are found mainly on the outer surface of the plasma membrane and can be further classified as what two groups?
- cerebrosides
- globosides
Glycosphinglipids
____________ have a single sugar, whereas ____________ have two or more.
cerebrosides; globosides
Gangliosides are glycolipids that have polar head groups composed of oligosaccharides with one or more ________________________ acid (NANA) molecules at the terminus and a negative charge.
N-acetylneuraminic
Gangliosides are also considered ____________ because they have a glycosidic linkage and no phosphate group.
glycolipids
What roles do gangliosides play?
Cell interaction, recognition, and signal transduction
What do gangliosides look like?
They are gangly sphingolipids, with complex structure and functional groups
Waxes are ________ of long-chain fatty acids with long-chain ____________.
esters; alcohols
Lipids serve as ____________ in the electron transport chain and in glycosylation reactions.
coenzymes
________ are a class of lipids built from isoprene moieties and share a common structural pattern with carbons grouped in multiples of five.
terpenes
How are terprenes grouped?
Based on the number of isoprene units present
A single terpene unit contains how many isoprene units?
two
____________ contain two isoprene units.
Monoterpenes
________________ contain three isoprene units.
Sesquiterpenes
sesqui- meaning “one and a half”
____________ contain four isoprene units.
diterpenes
____________ with six isoprene units, can be converted to ____________ and various steroids.
triterpenes; cholesterol
____________, like beta-carotene and lutein, are ____________ and have eight isoprene units.
carotenoids; tetraterpenes
____________, also sometimes referred to as isoprenoids, are derivatives of terpenes that have undergone ____________ or rearrangement of the carbon skeleton.
terpenoids; oxygenation
____________ are metabolic derivatives of terpenes.
steroids
Steroids are characterized by having four ____________ rings fused together: three ____________ and one ________________.
cycloalkane; cyclohexane, cyclopentane
Steroid functionality is determined by the ____________ ________ of these rings, as well as the functional groups they carry.
oxidation status
The larger number of carbons and hydrogens make steroids ____________.
nonpolar
Steroid refers to a group defined by a particular chemical structure, but steroid hormones are what?
steroids that act as hormones, meaning they are secreted by endorcine glands into the bloodstream and then travel on protein carriers to distant sites
What do steroid hormones do?
They regulate gene expression and metabolism
____________ is a steroid of primary importance. It is a major component of the phospholipid bilayer and is responsible for mediating membrane fluidity.
Cholesterol
Cholesterol, like a phospholipid, is an ____________ molecule, which allows it to maintain relatively constant fluidity in cell membranes.
amphipathic
Cholesterol also serves as a precursor to many important molecules like?
Steroid hormones, bile acids, vitamin D
____________ are 20-carbon molecules that are unsaturated carboxylic acids.
prostaglandins
Prostaglandins are derived from ________________ ________ and contain one ____-carbon ring.
arachidonic acid; five
Prostaglandins act as ____________ or ____________ signaling molecules.
paracrine, autocrine
The biological function of prostaglandins is to regulate the synthesis of ____________, which is a ubiquitous intracellular messenger, and in turn, mediates the actions of many other hormones.
cAMP
A ____________ is an essential nutrient that cannot be adequately synthesized by the body and therefore must be consumed in the diet.
vitamin
Vitaimins are commonly divided into ________-soluble and ________-soluble categories.
water, lipid
What are the fat-soluble vitamins?
A, D, E, and K
Vitamin ____, or ____________, is an unsaturated hydrocarbon that is important in vision, growth and development, and immune function.
A; carotene
The most significant metabolite of vitamin A is the aldehyde form, ____________, which is a component of the light-sending molecular system in the human eye.
retinal
____________ , the storage form of Vitamin A, is also oxidized to ________ ________, a hormone that regulates gene expression during epithelial development.
retinol; retinoic acid
Vitamin ____, or ____________, can be consumed or formed in a UV light-driven reaction in the skin.
D, cholecalciferol
In the liver and kidneys, vitamin D is converted to ____________, the biologically active form of vitamin D.
calcitriol
Calcitriol increases ________ and ________ uptake in the intestines, which promotes bone production.
calcium and phosphate
A lack of vitamin D can result in ________, a condition seen in children and characterized by underdeveloped, curved long bones as well as impeded growth.
rickets
Vitamin E characterizes a group of closely related lipids called ____________ and ____________.
tocopherols and tocotrienols
Vitamin E lipids are characterized by a ____________ aromatic ring with a long ____________ side chain and are characteristically hydrophobic.
substituted; isoprenoid
Tocopherols are biological ____________. The aromatic ring reacts with ________ ____________, destroying them.
antioxidants; free radicals
When tocopherols destroy free radicals, it prevents ________ ________.
oxidative damage
Vitamin ____ is actually a group of compounds, including ____________ and the ________________
K; phylloquinone and menaquinones
Vitamin K is vital to the posttranslational modifications required to form ____________, an important clotting factor in the blood.
prothrombin
The aromatic ring of vitamin K underoges a cycle of redox during the formation of prothrombin. Vitamin K is also required to introduce ________-binding sites on several calcium-dependent proteins.
calcium
________________ are a class of lipids specifically used for energy storage.
triacylglycerols
Why are lipids a good way to store energy?
- Carbon atoms of fatty acids are more reduced than those of sugars
- Triacylglycerols are hydrophobic
Because fatty acids are more reduced than those of sugars, the oxidation of triacylglycerols yields ________ the amount of energy per gram as carbohydrates, making them very energy dense.
twice
Because triacylglycerols are hydrophobic, they do not draw in water and do not require ____________ for stability. This helps decrease their ________, especially in comparison to hydrophilic polysaccharides.
hydration; weight
Triacylglycerols, also called ____________, are composed of three fatty acids bonded by ________ linkages to ____________.
triglycerides; ester, glycerol
Overall, triacylglycerols are ________ and ________, which contributes to their insolubility in water, as the ________ ____________ groups of the glycerol component and the ________ ____________ of fatty acids are bonded together, decreasing their polarity.
nonpolar, hydrophobic; polar hydroxyl, polar carboxylates
Special cells in animals, known as ____________, store large amounts of fat and are found primarily under the skin, around mammary glands, and in the abdominal cavity.
adipocytes
Triacylglycerols travel ____________ in the bloodstream between the liver and adipose tissue.
bidirectionally
The physical characteristics of triacylglycerols are primarily determined by the ____________ (or ____________) of the fatty acid chains that make them up, much like phospholipids.
saturation, unsaturation
Free fatty acids are ____________ fatty acids with a free ____________ group.
unesterified, carboxylate
In the blood, free fatty acids circulate in the blood bonded noncovalently to ________ ____________.
serum albumin
____________ is the ester hydrolysis of triacylglycerols using a strong base.
Saponification
Traditionally, the base that is used is ____, the common name for sodium or potassium hydroxide.
lye
The result of saponification is the basic ____________ of the fatty acid, leaving the sodium salt of the fatty acid and glycerol. This salt is known as soap.
cleavage
Soaps can act as surfactants. A surfactant lowers what?
surface tension at the surface of a liquid
IF we were to add a soap between the two phases in a mixture of vinegar and olive oil, the two phases would combine into a single phase, forming a ____________.
colloid
