LIPIDS: Study Guide

Question 1

L1: What are the definitions for amphipathic and adipocyte

Answer 1

amphipathic: (lipids) have both hydrophilic and hydrophobic parts
adipocyte: a cell specialized for the storage of fat, found in connective tissue

Question 2

L1: What are the definitions for steroid nucleus and polymorphism

Answer 2

steroid nucleus: non-liner structure built on a tetracyclic platform
polymorphism: multiple stable structures/states. Facilitate membrane stability and lipid : protein interactions

Question 3

L1: What are the definitions for carboxyl terminus and omega carbon

Answer 3

carboxyl terminus: the end of a peptide or protein’s primary structure
omega carbon: the last carbon in the chain, farthest from the carboxyl group

Question 4

L1: What are the major elements required for life present in fatty acids

Answer 4

Carbon, Hydrogen, Oxygen (not NPS)

Question 5

L1: What are the four classes of lipids? (which have FAs/ involved in membranes)

Answer 5

Triacylglycerides (FA), Phospholipids (FA, membranes), Glycolipids (FA, membranes), Steroids (membranes)

Question 6

L1: Why are lipids not considered to be “true polymers”?

Answer 6

generally large biomolecule, not a lot of monomers, monomers are not interlinked

Question 7

L1: Why are lipids water-insoluble, yet amphipathic?

Answer 7

-they are primarily nonpolar (water-fearing) carbon-carbon or carbon-hydrogen bonds
-they are soluble in nonpolar organic solvents
-they have a hyrophillic polar end and a hydrophobic nonpolar

Question 8

L1: What do saturated, unsaturated, omega-3 and omega-6 fatty acids look like?

Answer 8

Saturated - composed of carbon-carbon single bonds (stearic acid)
Unsaturated - one or more carbon- carbon double or triple bonds
Omega-3 / Omega-6 - refer to the location of the first carbon-carbon double bond, if you start counting from the ω end.

Question 9

L1: Are trans fats saturated and unsaturated? What do they look like?

Answer 9

Trans fat: unsaturated fat, unnatural, has to be synthesized synthetically. Hydrogens are split across the double bond (one up and one down)
Unsaturated: one or more carbon-carbon double/triple bonds (usually cis)

Question 10

L1: Describe the naming process for fatty acids (X:X)

Answer 10

The first X (:X) is the total carbons in the fatty acid
The second X (X:) is the total carbon-carbon double bonds

Question 11

L1: Which type of saturated FA has a higher melting point: a shorter FA or a longer FA?

Answer 11

-a longer fatty acid chain would have a higher melting point
-melting point decreases when bonds are added, more carbons= higher melting points

Question 12

L1: Which type of unsaturated FA has a higher melting point: monounsaturated or polyunsaturated?

Answer 12

Monounsaturated

Question 13

L1: Compare and contrast phosphoglycerides with sphingolipids and with glycoglycerolipids.

Answer 13

phosphoglycerides(phospholipid): found in the plasma membrane
- have 2 fatty acids
-platform: glycerol

sphingolipid (phospholipid): found in the nervous system
-have 1 fatty acid
-platform: sphingosine

glycoglycerolipid (glycolipid): found in plant cell membrane
-lipid with carb monomers covalently attached

Question 14

L1: Compare and contrast glycosphingolipids with glycoglycerolipids and with sphingolipids.

Answer 14

Glycosphingolipids = animal cells, for eukaryotic membranes, a glycolipid, only 1 FA (like sphingolipids)
Glycoglycerolipds = plant cells, for eukaryotic membranes, a glycolipid
Sphingolipid = NS mainly, 1 FA, platform - sphingosine, ex. sphingomyelin, phospholipid

Question 15

L1: What is the hydrophobic effect? How does it impact membrane formation?

Answer 15

-the phenomenon by which nonpolar molecules aggregate to avoid contact with polar molecules, mainly water (entropy-driven association)
-this effect drives membrane formation (the membrane is stabilized with non-covalent interactions)
-nonpolar tails and polar heads

Question 16

L1: Explain why membranes are asymmetric, noncovalent assemblies.

Answer 16

asymmetric as outer surface hydrophilic but internal space hydrophobic and certain lipids found mostly on one outer surface
noncovalent as stabilized by noncovalent interactions

Question 17

L1: Explain why membranes have polarity. Can asymmetry play a role?

Answer 17

-asymmetric as outer surface hydrophilic but internal space hydrophobic and certain lipids found mostly on one outer surface
-noncovalent assembly as stabilized by noncovalent interactions
-membranes are polar because negatively charged heads are on the exterior and uncharged tails on the interior

Question 18

L1: what do peripheral and integral membrane proteins look like?

Answer 18

Peripheral proteins are the ones outside the bilayer/membrane - on one side of the membrane of the other
integral proteins are embedded in the bilayer/membrane - span entire membrane

Question 19

L1: Do all cellular organelles have the same membrane composition?

Answer 19

No, membrane-bound organelles are only found in eukaryotic cells
-membrane composition differs depending on the organelle’s function

Question 20

L1: Why does cholesterol, FA chain length and degree of unsaturation impact fluidity

Answer 20

(eukaryotes) more cholesterol = more membrane rigidity = less fluid
(prokaryotes) shorter chain and cis unsaturation = less membrane rigidity = more fluid (adjusting Carbon-Carbon double bonds)

Question 21

L2: What is the difference between lateral and transverse diffusion

Answer 21

-lateral diffusion: move along one side of the membrane
-transverse: flipping sides on the membrane

Question 22

L2: Define what a nuclear hormone receptor is

Answer 22

Found in nucleus, can be bound to ligand lipids, and bind to DNA and alter gene expression

Question 23

L2: what is the difference between kinase and phosphatase

Answer 23

kinase: an enzyme that attaches a phosphate group to a protein
phosphatase: an enzyme that removes a phosphate group from a protein

Question 24

L2: what are the differences between simple diffusion, passive transport, and active transport

Answer 24

Passive transport :
Facilitated diffusion - with concentration gradient, moving charged and large molecule, polar, need protein to cross ((uniport) carrier-mediated and channel mediated)
Simple diffusion - don’t need protein, high to low concentration, small/uncharged, going with concentration gradient, small uncharged molecules (like CO2 and O2) cross by this

Active transport : uniport and cotransport (moving 2 molecules at once, could be with or against gradient). pump mediated, transfer from low to high, against concentration gradient, require ATP. pumps use active - also move water-soluble molecules via hydrophilic “hole”

Question 25

L2: Are transporters peripheral or integral membrane proteins? What about receptors?

Answer 25

-integral membrane proteins that function as channels or pumps -Both are integral membrane proteins that facilitate cellular functions.

Question 26

L2: How does signal transduction pathway operate

Answer 26

process by which molecular stimuli are transmitted through a cell 1. stimulus triggers release of a primary messenger 2. primary messenger is recognized by a receptor 3. information is relayed to cell's interior by second messengers 4. second messengers activate or inhibit effector molecules 5. signal cascade is terminated

Question 27

L2: what is the difference between primary and secondary messengers

Answer 27

primary messenger: -extracellular signals -do not readily diffuse across membranes -interact with receptors to initiate intracellular activity Secondary messenger: -intracellular signals -do readily diffuse across membranes, amplifying a signal -interact with effector molecules to trigger effector molecules

Question 28

L2: Why are lipid-derived primary messengers able to bind to nuclear hormone receptors but protein-derived primary messengers cannot?

Answer 28

-composition of the lipid is more suitable for binding versus the protein (TA said this?)

Question 29

L2: Compare and contrast the structure of a 7TM / GPCR with a dimeric protein receptor.

Answer 29

- Both integral membrane proteins -ligand will bind to extracellular 7TM receptors and intracellular nuclear hormones receptors **** add to this slide

Question 30

L2: What happens when a receptor recognizes a primary messenger?

Answer 30

Information is then relayed to cell's interior by second messenger

Question 31

L2: How does the insulin signal transduction pathway work

Answer 31

1. High glucose triggers insulin (primary msg) release 2. insulin interacts with insulin receptor 3. activated receptor facilitates the synthesis of PIP3 (second msg) 4. PIP3 facilitates activation of AKT 9 (an effector)

Question 32

L2: Explain how insulin increases glucose uptake in muscle cells, focusing on activated protein kinase B (Akt) and GLUT4.

Answer 32

GLUT moves glucose into the cell & protein kinase helps GLUT move to the surface Insulin (hormone) released by pancreatic β-cells when blood glucose-rich Stimulates liver to synthesize glycogen Stimulates muscle and fat cells to uptake glucose

Question 33

L2: How is the insulin signal transduction pathway shutdown?

Answer 33

termination of insulin signaling depends on dephosphorylation - dephosphorylation of the second messenger

Question 34

L3: What is the definition of catabolism and peroxisome

Answer 34

catabolism: breaking down - breaking 1 molecule down to liberate energy peroxisome: organelle containing oxidative enzymes

Question 35

L3: what are some examples of edible items that contain lipids and some that do not

Answer 35

-found within foods that contain vegetable oils or fats (some spices or herbs) -inorganic food additives (like sugar/salt) lack this biomolecule

Question 36

L3: Do digestive enzymes cleave covalent bonds or noncovalent interactions?

Answer 36

cleave covalent bonds using water

Question 37

L3: how are lipids digested (name the lipases/where)

Answer 37

Lipids are digested by a set of digestive enzymes, which cleave bonds using water -Mouth: saliva contains lingual lipase -Stomach: gastric lipase cleave TAGS -Small intestine: bile salts insert into lipid droplets Small intestine: pancreatic lipases cleave TAGS/DAGS

Question 38

L3: How are FAs transported across the mitochondrial inner membrane?

Answer 38

requires activation and channels - organelle has 2 membranes; inner one is highly impermeable activation by attaching FA to coenzyme A, catalyzed by enzyme acyl CoA synthetase, reaction reversible but driven forward by ATP hydrolysis

Question 39

L3: what are the four steps of the B-oxidation pathway (where/ what organelles/ does it occur in humans)

Answer 39

-this pathway primarily occurs within the mitochondria of skeletal muscle cells 1. Oxidation by FAD by dehydrogenase 2. Hydration by hydratase 3. Oxidation by NAD+ dehydrogenase 4. Thiolysis by coenzyme A -yes it occurs in humans, lipid synthesis

Question 40

L3: How do you calculate how many rounds of b-oxidation are necessary to metabolize a FA

Answer 40

you divide the number of carbons by 2 and subtract 1 ex. 15/2 = 7.5 -1 = 6.5 (round down if half carbon)

Question 41

L3: The ß-oxidation pathway generates acetyl CoA and propionyl CoA. What happens to each of these products?

Answer 41

With an odd fatty acid chain, propionyl CoA is converted to succinyl CoA (which enters cellular respiration via the citric acid cycle)

Question 42

L3: Can the human body metabolize very long-chain fatty acids? What about unsaturated fatty acids?

Answer 42

Yes, it's just difficult. Very long chain (22+ Carbons) sent to peroxisome first then acyl group shortened via peroxisomal B-oxidation pathway, then transported to mitochondria for standard B-oxidation pathway. Yes, unsaturated fatty acids can be metabolized

Question 43

L3: Glycerol metabolism generates glyceraldehyde 3-phosphate. What happens to this product? Where [organ(s)] does glycerol metabolism occur in humans?

Answer 43

during lipid digestion/lipolysis, glycerol is separated from fatty acids in TAGS -sent to the liver, which is phosphorylated by glycerol kinase -G3P is an intermediate of glycolysis and gluconeogenesis

Question 44

L3: Ketolysis generates acetyl CoA. What happens to this product? Where [organ(s) and organelle(s)] does ketolysis occur in humans?

Answer 44

acetyl CoA enters cellular respiration via the citric acid cycle -metabolism occurs primarily within the mitochondria of the brain, heart, and skeletal muscle cells -products enter cellular respiration (ketogenesis occurs primarily in the liver)

Question 45

L3: Refer to the cellular respiration pathway, where are fatty acids and glycerol entering

Answer 45

fatty acids: come from fats, enter as an intermediate into pyruvate oxidation, and prepares to enter the citric acid cycle glycerol: come from fats, and enter into glycolysis as the "backbone" (G3P) and prepares to enter pyruvate oxidation

Question 46

L4: what is the definition of anabolism and committed step

Answer 46

Anabolism: building up (make more complex molecules) committed step: irreversible reaction that "dedicated" atoms to that pathway and the final product. in fatty acid synthesis, used to regulate overall pathway

Question 47

L4: what are the four repeating steps in fatty acids synthesis

Answer 47

1. Condensation 2. reduction of the carbonyl group 3. dehydration 4. reduction of the double bond (steps repeat until palmitate (16:0) made- extending fatty acids by 2 each time)

Question 48

L4: To synthesize an odd chain FA, would acetyl CoA or propionyl CoA be activated? What about for an even chain FA?

Answer 48

Propionyl CoA would be activated, not acetyl CoA Even chain first reaction is condensation of malonyl ACP with acetyl ACP

Question 49

L4: Why are PUFAs an essential dietary component?

Answer 49

Polyunsaturated fatty acids are mainly localized in cell membranes. -they play a role in membrane fluidity, reduce inflammation, and blood clotting, regulate blood pressure and cell signaling

Question 50

L4: Can the human body synthesize trans fats? If not, where are they coming from?

Answer 50

No, we cannot synthesize them on our own. They come from our diet

Question 51

L4: How can you tell if a FA was synthesized by human enzymes

Answer 51

(IDK!) triacylglycerides, most synthesis (80%) occurs in ER of intestinal cells via monoacylglycerol pathway. Phospholipids synthesis occurs in ER of most cells vis kennedy pathway glycolipds synthesis occurs in most cells and involves the ER and golgi complex -look for trans fatty acids (our body can’t synthesize) or if there are double bonds past a certain point

Question 52

L4: How is fatty acid synthesis regulated

Answer 52

The committed step in fatty acid synthesis consequently, will be used to regulate overall pathway

Question 53

L4: Where [organ(s) and organelle(s)] does cholesterol synthesis occur in humans?

Answer 53

part 1 occurs in the cytoplasm; part 2/3 occur in the ER -synthesized in the liver from acetyl CoA

Question 54

L4: How are statins able to lower cholesterol? why are diet changes recommended for someone taking statins?

Answer 54

They're a competitive inhibitor of HMG CoA reductase, mimic enzymes substrate so compete for binding in active site, if statin is bound, then cholesterol synthesis declines

Question 55

L4: How is cholesterol synthesis regulated

Answer 55

-cholesterol synthesis is controlled via HMG CoA reductase 1. HMG CoA reductase gene expression 2. hormones (insulin/ glucagon) 3. oxygenated-cholesterol derivatives 4. phosphorylation

Question 56

L4: How do LDL and HDL differ, in terms of cholesterol destination?

Answer 56

LDL - low density; transporters cholesterol from liver to body - labeled "bad cholesterol" as contributes to artery cholesterol buildup HDL - high density; transports cholesterol from body to liver - labeled "good cholesterol" as scavenges cholesterol from arteries

Question 57

where are triacylglycerols made?

Answer 57

majority occurs in the ER of intestinal cells via the monoacylglycerol pathway

Question 58

where are phospholipids made?

Answer 58

synthesis occurs in the ER of most cells via the Kennedy pathway

Question 59

where are glycolipids made? what is the enzyme?

Answer 59

synthesis occurs in most cells and involves the ER/Golgi -key enzyme (ceramide glucosyltransferase)