Biochem 5, 11 Flashcards
lipids are insoluble in
water
lipids are soluble in
nonpolar organic solvents
phospholipids
ampthipathic
form bilayer of biological membranes
saturation of fatty acid tails determines
the fluidity of the membrane
phospholipids structure
hydrophilic (polar) head - attached by phosphodiester linkage, determines function of phospholipid (bc interacts with environment)
hydrophobic (nonpolar) tail
saturated fatty acids vs unsaturated fatty acids fluidity
saturated less fluid thatn unsaturated
glycerophospholipids
phospholipids that contain glycerol backbone
sphingolipids
contain a sphingosine or sphingoid backbone
sphingophospholipids
sphingolipids that contain a phosphodiester bond
sphingomyelins
type of sphingophospholipids
contain a phosphatidylcholine or phosphatidylethanolamine head group
major component of myelin sheath
glycosphingolipids
attached to sugar moieties instead of a phosphate group
cerebrosides
type of glycosphingolipid
have one sugar connected to sphingosine
globosides
type of glycosphingolipid
have two or more sugars connected to sphingosine
gangliosides
contain oligosaccharides with at least one terminal N-acetylneuraminic acid (NANA/sialic acid)
waxes
contain long fatty acids esterified to long chain alcohols
used as protection against evaporation and parasites in plants and animals
glycerol
3 carbon alcohol
saturated fatty acids
have no double bonds between carbons
unsaturated fatty acid
one or more double bonds between carbons
terpenes
odiferous steroid percursors made from isoprene
isoprene
5 carbon molecule
one terpene unit (monoprene) contains
two isprene units
steroid structure
3 cyclohexane rings + 1 cyclopentane ring
steroid hormones
have high affinity receptors
work at low concentrations
affect gene expression and metabolism
cholesterol
steroid important to membrane fluidity and stability
precursor to many other molecules
prostaglandins
autocrine and paracrine signaling molecules that regulate cAMP levels
have powerful effects on smooth muscle contraction, body temp, sleep wake cycle, fever, and pain
fat soluble vitamins include
ADEK
vitamin A
aka cerotene
metabolized to retinal for vision and retinoic acid for gene expression in epithelial development
vitamin D
aka cholecalciferol
metabolized to calcitriol in kidneys
regulates calcium and phosphorus homeostasis in intestines (inc calcium and phosphate absorption)
promotes bone formation
rickets
deficiency in vitamin D
vitamin E
aka tocopherols
biological antioxidants
aromatic rings destroy free radicals, preventing oxidative damage
vitamin K
aka phylloquinone and menaquinones
important for formation of prothrombin, a clotting factor
performs posttranslational modifications on many proteins, creating calcium binding sites
triaclyglycerols
preferred method of storing energy for long term use
carbon atoms in lipids are more reduced than carbs, giving twice as much energy per gram during oxidation
very hydrophobic - not hydrated by body water and do not carry additional water weight
triaclyglycerol structure
one glycerol attached to 3 fatty acids by ester bonds
the fatty acids usually vary within the same triacylglycerol
adipocytes
storage of large triaclyglycerol deposits for animals
free fatty acids
unesterified fatty acids that travel in bloodstream
soaps
salts of free fatty acids
act as surfactants, forming micelles
saponification
ester hydrolysis of tricycglycerols using a strong base, like sodium or potassium hydroxide
micelle
dissolves lipid soluble molecules in its fatty acid core, and washes away with water because of its shell of carboxylate head groups
surfactant
lowers surface tension at the surface of a liquid, serving as a detergent or emulsifier
chemical digestion of lipids occurs in
small intestine
chemical digestion of lipids is faciltated by
bile, pancreatic lipase, colipase, and cholesterol esterase
digested lipids may form ____ for…
micelles for absorption or be absorbed directly
short-chain fatty acids are absorbed…
across intestine into blood
long chain ftty acids are absorbed as ___ and…
micelles and assembled into chylomicrons for release into lymphatic system
how are lipids mobilized?
- from adipocytes: by hormone sensitive lipase (HSL)
- from lipoproteins: by lipoprotein lipase (LPL)
lipoprotein lipase (LPL)
necessary for metabolism of chylomicrons and VLDL
chylomicrons
transport mechanism for dietary triacyclerol molecules
transported via lymphatic system
VLDL
transports newly synthesized triacylglycerol molecules from liver to peripheral tissues in bloodstream
IDL
aka VLDL remnant
in transition between triacylglycerol and cholesterol transport
picks up cholesteryl esters from HDL
LDL
transports cholesterol for use by tissues
HDL
reverse transport of cholesterol
apoproteins
control interactions between lipoproteins
cholesterol may be obtained through
dietary sources or de novo synthesis in liver
key enzyme in cholesterol biosynthesis
HMG-CoA reductase
fatty acids are synthesized in the ___ from __
cytoplasm from acetyl-CoA transported out of the mitochondria
fatty acid synthesis steps
activation, bond formation, reduction, dehydration, second reduction
repeated 8 times to form palmitic acid
palmitic acid
the only fatty acid that humans can synthesize
fatty acid oxidation occurs in ___ following ___
mitochondria following transport by the carnitine shuttle
beta oxidation
uses cycles of oxidation, hydration, oxidation, and cleavage
fatty acid oxidation
branched and unsaturated fatty acids
require special enzymes
unsaturated fatty acids use an isomerase and additional reductase during cleavage
ketogenesis
formation of ketone bodies
ketone bodies form during
prolonged starvation state due to excess acetyl-CoA in the liver
ketolysis
regenerates acetyl-CoA for use as an energy source in peripheral tissues
protein digestion occurs primarily in
small intestine
catabolism of cellular proteins occurs
only under conditions of starvation
protein catabolism
carbon skeletons of amino acids used for energy, either through gluconeogenesis or ketone body formation
amino groups are fed into urea cycle for excretion
fate of a side chain depends on its chemistry
urea cycle
occurs in liver
body’s primary way of removing excess nitrogen from the body
Which of the following statements about fatty acid synthesis is correct?
(A) Fatty acids can be used to synthesize glucose.
(B) Fatty acids can be synthesized from glucose.
(C) Fatty acids can be broken down to generate NADPH
(D) Fatty acids are important in nucleotide synthesis.
(B) Fatty acids can be synthesized from glucose.
Excess glucose (from dietary carbohydrates) can be converted into acetyl-CoA, which can be used to build up fatty acids.
Because the PDH reaction is irreversible, fatty acids cannot be converted back into glucose.
In the liver, fatty acids synthesized from glucose can be packaged with the chylomicron remnants to form:
(A) HDLs
(B) Chylomicrons
(C) VLDLs
(D) Albumin
(C) VLDLs
In the liver, fatty acids synthesized from glucose can be packaged with the chylomicron remnants to form very low density lipoproteins (VLDLs).
Where in the cell does fatty acid synthesis occur?
(A) Mitochondrial intermembrane space
(B) Mitochondrial Matrix
(C) Inner membrane of the mitochondria
(D) Cytoplasm
(D) Cytoplasm
Fatty acid synthesis occurs in the cytoplasm.
Triacylglyceride molecules can be broken down into glycerol and fatty acids. Glycerol can be broken down for use as energy via ______________ and fatty acid chains can be broken down for use as energy via ______________.
(A) glycolysis, beta-oxidation
(B) beta-oxidation, glycolysis
(C) pentose phosphate pathway, glycogenolysis
(D) glycogenolysis, pentose phosphate pathway
(A) glycolysis, beta-oxidation
Triacylglyceride molecules can be broken down into glycerol and fatty acids. Glycerol can be broken down for use as energy via glycolysis and fatty acid chains can be broken down for use as energy via beta-oxidation.
Compare beta-oxidation and fatty acid synthesis?
They are almost the same exact pathway except that they are going in opposite directions. The goal of beta-oxidation is to break fatty acids down into two-carbon acetyl-CoA molecules while the goal of fatty acid synthesis is to combine acetyl-CoA molecules together in the formation of a long-chain fatty acid.
Let’s Review – Where does each of the following metabolic pathways take place in the cell?
(1) Glycolysis
(2) Gluconeogenesis
(3) The Linking Step
(4) The Kreb’s Cycle
(5) The Electron Transport Chain
(6) Fatty Acid Synthesis
(7) Beta-oxidation
(1) Glycolysis - Cytoplasm
(2) Gluconeogenesis - Liver
(3) The Linking Step - Mitochondrial Matrix
(4) The Kreb’s Cycle - Mitochondrial Matrix
(5) The Electron Transport Chain - Inner Mitochondrial Membrane
(6) Fatty Acid Synthesis - Cytoplasm
(7) Beta-oxidation - Mitochondrial Matrix
CRB True or false? NADH and FADH2 produced from the breakdown of fatty acids must be shuttled before they can be used in the Electron Transport Chain.
False. Because Beta-Oxidation mainly occurs in the mitochondria, the NADH and FADH2 can easily be used by the Electron Transport Chain without relying on shuttles.
Amino acids can be used to make which of the following?
I. Protein
II. Glucose
III. Fatty Acids
(A) I Only
(B) I and II Only
(C) I and III Only
(D) I, II, and III
(D) I, II, and III
Amino acids can be used to make protein, glucose, or fatty acids.
