CHAP10 Lipids, Membrane & Membrane Protein Structure , &Lipid Utilization & Transport of Fath Cholesterol/ CHAP 17 & CHAP 19

Lipids, Membranes, and Lipid Metabolism Flashcards

What are the two main components of lipids?

A polar head group (hydrophilic) and a nonpolar tail (hydrophobic, consisting of fatty acids)

What are monolayers, bilayers, micelles, and vesicles?

Structures formed when amphipathic membrane lipids are in contact with an aqueous solution.

What are fats/triacylglycerols?

Triesters of fatty acids and glycerol used for long-term energy storage

What is the role of adipocytes?

Animal fat storage cells.

What is saponification?

The hydrolysis of fat with a strong base (NaOH/KOH) to produce soap. Fatty acids are released as Na/K salts which become fully ionized.

What are waxes composed of?

Esters of fatty acids and long-chain alcohols, characterized by long hydrophobic chains making them insoluble in water.

Name the four major classes of membrane-forming lipids

Glycerophospholipids, sphingolipids, glycosphingolipids, and glycoglycerolipids.

How do cylindrical molecules contribute to the formation of bilayer membranes?

They easily pack in parallel, forming extended sheets.

What is the stereochemical numbering system for glycerophospholipids?

The sn-stereochemical numbering system. It assigns pro-s to C1.

What is ceramide?

A long-chain hydrophobic tail attached to one fatty acid, formed by linking a fatty acid to the NH2 group with an amide bond.

What are cerebrosides and Gangliosides?

Glycosphingolipids found in brain cell membranes (cerebrosides) and neural tissue (gangliosides).

List the components of the fluid mosaic model

The membrane is a fluid mixture of lipids and proteins.

How temperature impacts membrane fluidity

Increase heat absorption by the membrane. The temperature that this transition occurs it Transition temperature. Transition temperature broadened at 40%.

How do longer saturated tails influence transition temperature?

They increase transition temperature.

How do shorter tails and more cis double bonds influence transition temperature?

They decrease transition temperature.

What is the function of bacteriorhodopsin?

A light-driven proton pump in certain bacteria.

How is the insertion and folding of transmembrane proteins accomplished?

Transmembrane exit translocon & insert to bilayer a fold opening and closing of Secy-2 red helices more apart opening the gap allows nascent peptide sequence in translocon access to hydrophobic core of membrane

What is the role of the translocon?

To facilitate the insertion of integral membrane proteins into the bilayer.

What are membrane rafts?

Regions of the cell membrane that are rich in cholesterol, sphingolipids, and GPI-linked proteins.

What is hydrophobic mismatch?

When the thickness of bilayer core and the hydrophobic area of embedded protein do not match, adjustment occurs either in the protein or the bilayer.

List 3 ways equalization of concentration can be overcome

binding substance to macromolecule, maintain membrane potential, coupling transport to exergonic process

What is Valinomycin?

An antibiotic that acts as an ion carrier. It's a hydrophobic spherical cyclic polypeptide which can complex with ions.

How does Gramicidin A function?

It forms an ion pore through the membrane with two molecules adopting a helical conformation with hydrophobic side chains in contact with lipids.

What is the function of aquaporins?

Tetramers of specific monomers. They transport water across the cell membrane

How is ion selectivity achieved in ion channels?

By the optimal geometry of a chelating group in the ion channels

How does the voltage-gating channel work?

The depth of the helices changes as a function of the membrane potential due to its Arg/Lys rich helices.

Describe active transport

Moves substances across the membrane against a concentration gradient, coupled directly or indirectly to ATP hydrolysis

What are cardiotonic steroids?

They inhibit the Na+/K+ pump, which increases Ca2+ ion concentration in heart muscle for stronger contraction.

Describe cotransport

Unfavorable movement of a substance through the membrane is coupled with the favorable transport of another substance (e.g., sodium-glucose cotransport).

How does transport by modification work?

A substance diffuses through the membrane and is then modified so it cannot return, typically seen in bacterial sugar uptake via phosphorylation.

What are clathrin-coated vesicles and caveolae?

Structures involved in bulk transport across membranes, formed by coated pits (clathrin) or insertion of caveolin into the membrane leaflet (caveolae).

How do neurons conduct electrical impulses?

By membrane potential changes in regions of the cell membrane. Dendrites receive signals, which transmit to the axon, and then through synaptic termini.

How do Schwann cells assist in neural transmission?

They cover the axon with a myelin sheath, separated by nodes of Ranvier.

What causes the action potential?

Small polarization of the nerve cell membrane that opens voltage-gated channels, allowing ion flow.

What is FRAP?

Fluorescence recovery after photobleaching in which fluorescent dye diffuses and fades the bleach spot.

What are lipid bodies?

Fat storage in plant seedling ,After germination lipid bodies is degraded , oxidized , convert into carbohydrate to support growht

How liver transport triacylglycerols?

transport triacylglycerols by bloodstream vid very low density lipoprotein some ↑ = adipose tissue

What are bile salts?

Emulsifying agents in the intestine (e.g., cholic acid). Their hydrophobic surfaces associate with triacylglycerol and polar surfaces face outward, allowing micelle association with pancreatic lipase/colipase.

What is the function of lipoprotein lipase?

Lipoprotein lipase hydrolyzes triacylglycerol in chylomicrons, allowing uptake of glycerol and free fatty acids into cells. Chylomicron is anchor by lipoprotein lipase apolysaccharide chain attach to endothelial surface of cell, when activated by apoprotein II.

Define atherosclerosis

Liver dysfunction -> leads to inability to synthesize apolipoprotein to transport fat out of liver cell cholesterol accumulation is related to atherosclerotic plaque

What is the function of LCAT?

Catalyzes the synthesis of cholesterol esters in plasma from cholesterol and acyl chains in phosphatidylcholine. It is secreted by the liver and bound to HDL/LDL

What is the effects of LDL on HMG CoA reductase activity?

HMG CoA reductase activity is normal after removal of lipoprotein, but wit + LDL it decrease nonsterol from high to low

How do intracellular cholesterol regulate their own levels?

By controlling de novo cholesterol biosynthesis, formation and storage of cholesterol esters, and LDL receptor density

What is lipolysis?

The process liberates glycerol and fatty acids. Fatty acids control by cAMD-mediated cascade system

Describe FA Oxidation - Knoop experiment

when fed even number FA chain it form phenylacetic acid, odd number FA chain form benzoic acid , Oxidation is stepwise fashion.

How fatty acids are activated for oxidation

by ATP-Dependent Acylation of Coenzyme A, loss of pyrophosphate = 2 ATP used for activation

What is the importance of the fatty acyl-CoA

carnitine fatty acyl CoAc fatty acy) carnitine Cot transport to Mitochondria for exidation

Outline Reaction 1 (Initial Dehydrogenation)- FA oxidation

Catalyze by acy-CoA dehydrogenase dat catalyze removal of 2 H from &B (to form trans ap unsaturated acyl CoA

What happens in the last step in FA oxidation?

last step, attack of nucleophilic thio sulfur on e-poor Keto of 3-ketoacyl-CoA w/ cleavage of bond & release of acetyl-CoA , and Shortened fatty acyl-CoA is ready for oxidation again

Outline the beta-oxidation of polyunsaturated FA

action site of enonyl Cot isomerase & 2-4 dienoyl-CoA reductase

Where in fasting/starving situations, what happens and what it catalyzed by?

carbohydrate intake is low, oxaloacetate level drop a flux throught citric synthase is impaired, Acetyl-CoA level ↑ Catalyze by HMG-CoA synthase

What is FA Biosynthesis?

when carbohydrate catabolism is limited . Acetyl-CoA is convert to ketone bodies mainly acetoacetate & B-hydroxybutyrate as limp metabolic fuel

Where does translocation happen and what is formed during Palmitate biosynthesis?

translocation from ACP & enter cycle 2w/malonyl-ACP , => cycle form palmitoyl-ACP

Discuss FADesaturation

FADesaturation = desaturases enzyme convert saturated FA to unsaturated FA by introducing double bond

What is the rate limiting enzyme for synthesis in FA Synthesis?

Acetyl-CoA carboxylase (ACC) is control by allosteric (citrate & along-chainFA) & covalent modification mechanism phosphorylation in AMP

Discuss Polyketide Biosynthesis

series of pathway in bacteria Hungi dat involve in biosynthesis of polyketide (class of antibiotics) polyketide is potent inhibitors of bacterial protein Synthesis.

Outline Triglycerol biosynthesis

glycerol backbone is form through gloroneogenesis , reaction catalyze by pyruvate carboxylase,phosphonolpyruvate carbokinase DHAP is reduce to glycerol 3-phosphate lysophophatidic acid (LPA),phosphatidic acid (PA), sn-1.2-diacylglcerol (DAG) intermediate in TG resynthesis pathway

Where are phospholipid synthesized?

primarily as component of membrane. They are synthesized in SER-transport vesicle pinch off from SER & bcome absorb golgi complex

What is phosphotidyl ethand amine?

product of the Metabolism of Glycerolphospholipid where ransporter vesicle bring phospholipid to other cell

Outline phosphatidic acid 3 route in Eukaryote

Glycerol 3-phos, DHAP & reduce the OH group