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MCAT Biochem > Biochem #5 > Flashcards

Biochem #5 Flashcards

1
Q

lipids

A

characterized by insolubility in water and solubility in nonpolar organic solvents.
o Serve roles in structural, signaling, and energy storage.

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2
Q

each of the membrane components of lipids is an _____ molecule, meaning it has both hydrophilic and hydrophobic regions.

A

amphipathic

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3
Q

phospholipids

A

contain the following elements: a phosphate and alcohol that comprise the polar head group, joined to a hydrophobic fatty acid tail by phosphodiester linkages.
o Can be classified based on their backbone
 Ex: glycerol forms phosphoglycerides.

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4
Q

phosphodiester linkage

A

phosphate group in between two oxygens.

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5
Q

all lipids share the _____

A

long chain fatty acid tail

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6
Q

saturated fatty acid

A

fully single bonds, greater Van der Waals, and more stable, form solids at room temperature (butter), straight down

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7
Q

unsaturated fatty acid

A

includes one or more double bonds, which introduce kinks and make them hard to stack and solidify, liquids at room temperature (olive oil)

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8
Q

what are the two properties that determine lipid properties?

A

determined by the degree of saturation in fatty acid chains and the functional groups to which the fatty acid chains are bonded.

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9
Q

glycerophospholipids/phosphoglycerides

A

specifically, those phospholipids that contain a glycerol backbone bonded by ester linkages to two fatty acids and by a phosphodiester linkage to a highly polar head group.
o Head groups differ and glycerophospholipids are named based on their head group.
 Head can be positive, negative, or neutral.
 Ex: phosphatidylcholine (with a choline head group)

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10
Q

sphingolipid

A

o Sphingolipids have a sphingosine ORRRRR sphingoid (sphingosine-like) backbone, as opposed to the glycerol backbone of glycerophospholipids.
o Also have long-chain nonpolar fatty acid tails and polar head groups
o Can be both phospholipids or glycolipids (contain glycosidic linkages to sugars)
o Divided into four major subclasses, differing by their head groups
1. ceramide
2. sphingomyelins
3. glycosphingolipids (glycolipids)
4. ganglioside

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11
Q

ceramide

A

sphingolipid

the simplest, which has a single hydrogen atom as its head group.

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12
Q

Sphingomyelins

A

sphingolipid
major class of sphingolipids that are also phospholipids.
• Have a phosphodiester bond and the head has no net charge.
• Major components of the plasma membranes of cells producing myelin.

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13
Q

glycosphospholipids

A 
sphingolipid
head groups composed of sugars bonded by glycosidic linkages. Glycolipid.
•	NOT phospholipids. 
•	Broken down further
o	1. Cerebrosides: have a single sugar 
o	2. Globosides: have two or more sugars.  
•	no net charge at physiological pH
found on the outside of plasma membrane
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14
Q

gangliosides

A

sphingolipid
most complex sphingolipid. Also a glycolipid.
• Have polar head groups composed of oligosaccharides with one or more NANA (sialic acid) molecules and a negative charge.

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15
Q

waxes

A

esters of long chain fatty acids with long chain alcohols.
o Pliable solids at room temperature.
o Function as protection for both plants and animals. Also in animals they prevent dehydration, act as lubricant and water repellent
o Structure building: bee hives.

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16
Q

what are the precursors to steroids and other lipid signaling molecules and have varied independent function

A

terpenes and terpenoids

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17
Q

terpenes

A

: class of lipids built from isoprene moieties and share a common structural pattern with carbons grouped in multiples of five. (C5H8).
 Produced mainly by plants and insects (insect’s protective mechanism)
 Can be good smelling or bad smelling, contribute to many scents.
 Grouped according to the number of isoprene units present (with a single terpene unit containing two isoprene units):
• Monoterpene (C10H16): found in essential oils and turpentine
• Sesquiterpenes: contain three isoprene units.
• Diterpenes: contain four isoprene units
• Triterpenes: contain six isoprene units, can be converted to cholesterol and various steroids.
• Tetraterpenes: have eight isoprene units.
o Ex: carotenoids, like beta-carotene

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18
Q

diterpene has how many terprene units and how many carbons

A

2 terpene units and 4 isoprene units (20 carbons)

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19
Q

terpenoids

A

(isoprenoids): derivatives of terpenes that have undergone oxygenation or rearrangement of the carbon skeleton.
 Named similar to terpenes.
 Contribute to steroid biosynthesis and many scents.

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20
Q

steroids

A

structurally, are metabolic derivatives of terpenes and are very different from phospholipids.
 Have 4 cycloalkane rings fused together (3 cyclohexane and 1 cyclopentane)
 Nonpolar
 Functionality is determined based on oxidation status of the rings and functional groups that they carry.

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21
Q

steroid vs. phospholipid structure

A

steroid has the many ring structure

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22
Q

steroid hormones

A

steroids that act as hormones, secreted by the endocrine glands into the bloodstream and then travel on protein carriers to distant sites, where they can bind to specific high-affinity receptors and alter gene expression.
 Ex: testosterone, various estrogens, cortisol, and aldosterone.

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23
Q

cholesterol

A

a steroid of primary importance.
 Part of the phospholipid bilayer and mediates membrane fluidity.
 Is amphipathic
 Adjusts membrane/keeps it intact at high and low temperatures.
 Precursor for steroid hormones, bile acids, and vitamin D

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24
Q

prostaglandins

A

unsaturated carboxylic acids derived from arachidonic acid and contain one five-carbon ring.
 Signaling molecule, can act as paracrine or autocrine signaling molecules
 Regulate the synthesis of cAMP (involved in the pathway that causes pain, as well as other pathways)
• Have powerful effects on smooth muscle contraction, body temperature, the sleep-wake cycle, fever, and pain.

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25
vitamin
an essential nutrient that cannot be adequately synthesized by the body and therefore must be consume in the diet.
26
what are the fat soluble vitamins
ADEK
27
vitamin A
A (carotene): important in vision, growth and development, and immune function • Retinal: component of light-sending molecular system in the human eye • Retinol: the storage form of vitamin A • Retinoic acid: a hormone that regulates gene expression
28
Vitamin D
(cholecalciferol): can be consumed or formed in UV light-driven reaction in the skin • In the liver and kidneys, it is converted to calcitriol, biologically active Vitamin D. • Calcitriol increases calcium and phosphate uptake in the intestines, which promotes bone production. • Rickets: a condition seen in children and characterized by underdeveloped, curved long bones as well as impeded growth.
29
Vitamin E
characterizes tocopherols and tocotrienols. | • Antioxidant, destroys free radicals and prevents oxidative damage.
30
Vitamin K
``` includes phylloquinone (K1) and menaquinones (K2). • Important for blood clotting. • Also introduces calcium binding sites on several calcium-dependent proteins ```
31
triacylglycerols (triglycerol)
class of lipids specifically used for energy storage. 1. The carbon atoms of fatty acids are more reduced than those of sugars, and therefore oxidation of triacylglycerols yields 2x the energy. 2. They are hydrophobic which helps decrease their weight because they do not need hydration for stability like hydrophilic polysaccharides. o Composed of three fatty acids bonded by ester linkages to glycerol  Rare for all 3 fatty acids to be the same. o Adipocytes: store large amounts of fat and are found primarily under the skin, around mammary glands, and in the abdominal cavity. o Storage of triacylglycerols in adipose tissue.
32
adipocytes
cells in animals that store large amounts of fat and are found primarily under the skin, around mammary glands, and in the abdominal cavity. o Storage of triacylglycerols in adipose tissue.
33
storage of triacylglycerols occurs where?
adipose tissue
34
saponification
: the ester hydrolysis of triacylglycerols using a strong base. o Lye: the base that is commonly used. Sodium/potassium hydroxide. o The fatty acid salt is what is known as soap. o Soaps can act as surfactants: lowers the surface tension at the surface of a liquid, serving as a detergent or emulsifier.
35
colloid
when two different liquids that usually don’t join end up appearing to combine into a single phase with the addition of soap. Occurs due to micelles.
36
micelle
tiny aggregates of soap with the hydrophobic tails turned inward and the hydrophilic heads turned outward, thereby shielding the hydrophobic lipid tails and allowing for overall solvation (hydrophilic heads to interact with the environment) • Nonpolar compounds can dissolve in the hydrophobic interior of the water-soluble micelle, meaning that our cleaning agents can dissolve both water-soluble and water insoluble messes and then wash them away.
37
what are 3 main roles of lipids in the body
structure, signaling, and energy storage
38
do saturated fats or unsaturated fats form solids at room temperature?
saturated because they have greater van der waals forces
39
all glycerophospholipids are a type of ____
phospholipid (but not all phospholipids are glycerophospholipids)
40
what is another name for glycerophospholipids
phosphoglycerides
41
glycerophospholipids are named according to their ____
head group
42
the head group of glycerolphospholipids can take on what charge?
+, -, 0
43
what characteristic of glycerophospholipid fatty acid tails makes them highly diverse?
their degree of saturation and their length
44
the cell surface antigens on red blood cells are _____
sphingolipids
45
what characteristics of phospholipids make them so diverse?
they can be bonded to various head groups and fatty acids
46
sphingolipids have a _____ backbone
sphingosine/sphingoid
47
sphingolipids can be phospholipids when they have a ______ but when they have a glycosidic linkage, they are ____
phosphodiester linkage | glycolipids
48
glycolipid
sphingolipid with a glycosidic linkage, also known as glycosphingolipids
49
what are the 4 types of sphingolipids?
1. ceramide 2. sphingomyelins 3. glycosphingolipids (glycolipids) 4. ganglioside
50
what is the major class of sphingolipids that are also phospholipids?
sphingomyelins
51
what type of head groups do sphingomyelins have?
phosphatidylethanolamine and phosphatidylcholine
52
phosphatidylethanolamine head group has ____
ethanol-amine head group
53
phosphatidylcholine has _____
choline head group
54
what are further classifications of glycosphingolipids?
cerebrosides and globosides
55
cerebroside
glycosphingolipid: | single sugar
56
globoside
glycosphingolipid: | two or more sugars
57
what do the head groups of gangliosides have?
oligosaccharides with one or more N-acetylneuraminic acid (NANA, sialic acid) molecules at the terminus and a negative charge
58
a single terpene unit consists of _____ isoprene units
2
59
what type of terpene is vitamin A?
diterpene
60
what can triterpenes be converted to?
cholesterol and various steroids
61
how do terpenoids related to terpenes?
terpenoids are derivatives of terpenes that have undergone oxygenation or rearrangement of the carbon skeleton.
62
of the 4 rings in steroid molecules, how many are cyclohexane rings?
3 cyclohexane rings and 1 cyclopentane ring
63
cortisol is a type of ___
steroid
64
how does cholesterol function in the cell membrane at high and low temperatures?
at high temperatures, it holds the membrane intact and prevents it from becoming too permeable at low temperaturem it keeps it from solidifying
65
cholesterol plays a vital role in cell membrane ____
fluidity
66
what are prostaglandins derived from?
arachidonic acid
67
can a vitamin be adequately synthesized by the body?
no, so it must be consumed
68
lipid soluble vitamins can accumulate in ____ while excess water soluble vitamins _____
in fat | excreted through the urine
69
what are the fat soluble vitamins and their general roles in the body
A: light sensing in the eye D: absorption of calcium in the intestines E: anti-oxidant K: important for blood clotting
70
what is the larger group of molecules that cholesterol is a part of?
steroids
71
what is the formal name of vitamin A
carotene
72
what is the formal name of vitamin D
cholecalciferol
73
what is the formal name of vitamin E
tocopherols
74
what is the formal name of vitamin K
phylloquinone and menanquinones
75
why are triacylglycerols preferred to carbohydrates as a source of energy?
- they are more reduced so when they get oxidized to produce energy they yield more energy per gram - they are hydrophobic and can be stored in fat so they do not draw water in or require hydration for stability (decrease weight) - they can also play a role in insulation
76
triacylglycerols travel bidirectionally from the ___ to the ___
liver to adipose tissue
77
fatty acid salt micelles are responsible for the formation of ____ in soap?
bubbles
78
does the steroid hormone itself bind to DNA?
no. the hormone-receptor complex does
79
does cholesterol always increase membrane fluidity?
no, it depends on the temperature. High temp, decrease membrane fluidity to keep it intact.
80
cholesterol is a precursor for vitamin ___
D
81
prostaglandins are ___ or ___ signaling molecules
autocrine or paracrine
82
are waxes produced in humans or just plants and insects?
yes produced in humans for protective effects

MCAT Biochem (12 decks)

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