Untitled Flashcard Set

Lipid

A diverse group of water-insoluble biomolecules that dissolve in nonpolar solvents.

Major Classes of Lipids

Fatty acids, triglycerides, wax esters, phospholipids, sphingolipids, isoprenoids, and lipoproteins.

Physical Nature of Lipids

Described as 'greasy stuff', often in liquid form due to weak hydrophobic interactions.

Amphipathic Molecules

Molecules like phospholipids with both polar heads and nonpolar tails.

Micelles

Structures formed by amphipathic molecules in water where hydrophobic tails are sequestered.

Fatty Acids

Monocarboxylic acids with even numbers of carbon atoms in unbranched chains.

Saturated Fatty Acids

Fatty acids containing no carbon-carbon double bonds, typically solid at room temperature.

Unsaturated Fatty Acids

Fatty acids that contain one or more double bonds.

Cis Configuration

The configuration of unsaturated fats that creates kinks in their structure.

Trans Fatty Acids

Hydrogenated fatty acids that behave like saturated fats.

Nomenclature: Delta (Δ)

Counts from the carboxylate end of the fatty acid chain.

Nomenclature: Omega (ω)

Counts from the terminal methyl end of the fatty acid chain.

Essential Fatty Acids (EFAs)

Fatty acids that must be obtained through diet, including linoleic acid and alpha-linolenic acid.

Triacylglycerols (TAGs)

The storage form of lipids, consisting of glycerol backbone and three fatty acids.

Energy Efficiency of TAGs

TAGs are anhydrous, storing 8 times more energy by volume than hydrated glycogen.

Adipocytes

Specialized cells where TAGs are stored within adipose tissue.

Lipolysis

The mobilization of fatty acids triggered by low energy or hormones.

Chylomicrons

Lipid transport particles packaged by enterocytes for transport through lymph and blood.

VLDL

Very Low-Density Lipoprotein, transports endogenous TAGs from the liver.

LDL

Low-Density Lipoprotein, primary cholesterol transporters to tissues.

HDL

High-Density Lipoprotein, scavenges excess cholesterol and returns it to the liver.

Atherogenic

Describes small dense LDLs that can easily enter arterial walls and contribute to plaque formation.

Mitochondrial Matrix

Location where β-oxidation of fatty acids occurs.

Acyl-CoA

Fatty acids are converted to this form for activation, requiring ATP.

Carnitine Shuttle

Transport system required to move acyl groups into the mitochondrial matrix.

β-Oxidation

Process that removes two-carbon fragments from fatty acids generating acetyl-CoA.

NADH and FADH₂

Electron carriers produced during β-oxidation.

Odd-chain Fatty Acids

Yields propionyl-CoA, which can be converted to glucose.

Ketone Bodies

Produced from acetyl-CoA during starvation or diabetes, including acetoacetate and beta-hydroxybutyrate.

Cytoplasm

Primary location of fatty acid biosynthesis.

Acetyl-CoA Carboxylase (ACC)

Rate-limiting enzyme in fatty acid synthesis.

Fatty Acid Synthase (FAS)

Multi-enzyme complex that builds fatty acids using NADPH.

Regulation of ACC

Activated by citrate and insulin; inhibited by palmitoyl-CoA, glucagon, and AMPK.

Fluid Mosaic Model

Describes the structure of biological membranes as flexible layers with proteins and lipids.

Unsaturation Effect on Fluidity

Higher percentages of unsaturated fatty acids increase membrane fluidity.

Lipid Rafts

Microdomains enriched in cholesterol and sphingolipids that organize signaling.

HMG-CoA Reductase

Rate-limiting enzyme in cholesterol synthesis, target for statin drugs.

Bile Salts

Detergent-like compounds derived from cholesterol that aid in fat digestion.

Eicosanoids

Signaling molecules derived from 20-carbon fatty acids, such as arachidonic acid.

TCA Cycle Regulation

The Citric Acid Cycle is regulated by energy needs and several key enzymes.

Irreversible Steps of TCA Cycle

Regulated by citrate synthase, isocitrate dehydrogenase, and α-ketoglutarate dehydrogenase.

Allosteric Inhibitors

Compounds like ATP and NADH that inhibit TCA cycle enzymes.

Allosteric Activators

Compounds like ADP, AMP and calcium ions that activate TCA cycle enzymes.

PDH Complex

Links glycolysis to TCA cycle; regulated by acetyl-CoA and phosphorylation.

ETC Components

Four complexes involved in the electron transport chain, includes Complex I-IV.

Mobile Electron Carriers

Coenzyme Q and cytochrome c ferry electrons between ETC complexes.

Proton Gradient

Created by the ETC to drive ATP synthesis via ATP synthase.

Chemiosmotic Theory

Describes how protons are pumped to create a gradient for ATP production.

ATP Synthase

Enzyme that uses the proton gradient to synthesize ATP from ADP.

ETC Inhibitors

Compounds that block electron transport, affecting ATP synthesis.

Dinitrophenol (DNP)

A compound that uncouples oxidative phosphorylation, dissipating the proton gradient.

Brown Fat

Fat tissue rich in mitochondria that can generate heat instead of ATP.

Reactive Oxygen Species (ROS)

Damaging molecules formed by electron leakage from the electron transport chain.

Superoxide

A primary reactive oxygen species formed when electrons leak from the ETC.

Antioxidants

Molecules that help detoxify ROS, including vitamins C and E.

Lactic Acid Accumulation

A consequence of anaerobic metabolism during a heart attack, resulting in acidosis.

Reperfusion Injury

Damage caused by the reintroduction of oxygen to ischemic tissues, leading to ROS formation.

Heart Attack Metabolism

Shift from aerobic metabolism to anaerobic glycolysis due to lack of oxygen.

Ion Imbalance

Result of low ATP levels during a heart attack, leading to calcium overload.

Glycolytic Flux

Increased flow through glycolysis driven by reduced TCA cycle activity.

Hydrophobic Interactions

Interactions that lead lipids to dissolve in nonpolar solvents.

Triacylglycerols vs. Glycogen

TAGs store more energy than glycogen due to their anhydrous nature.

Palmitic Acid

Common fatty acid represented as 16:0, used in various biological contexts.

Insulin's Role in Fat Storage

Hormone that promotes fatty acid synthesis and fat storage.

Glucagon's Role in Fat Mobilization

Hormone that promotes lipolysis and release of fatty acids from adipose tissue.

Fatty Acid Binding Protein

A protein that transports free fatty acids in the bloodstream.

Acetyl-CoA Formation

The process of converting fatty acids for use in energy production.

Oxaloacetate

A TCA cycle intermediate that can leave the cycle for gluconeogenesis.

NADPH Sources for FA Synthesis

Primary sources include the pentose phosphate pathway and malic enzyme.

Fat Storage Cells

Adipocytes that store energy in the form of triglycerides.

Eicosanoids Functions

Hormone-like substances that regulate various physiological responses.

Hydrolyze Fatty Acids

The process facilitated by phospholipases to release fatty acids from phospholipids.

Fat Entry into Cells

Requires hydrolysis and transport proteins to facilitate movement across membranes.

Beta-Oxidation of FA

The metabolic pathway for fatty acid breakdown to produce acetyl-CoA.

Cost of Fatty Acid Activation

2 ATP equivalents are consumed to activate fatty acids to acyl-CoA.

Acetyl-CoA's Fate

Enters the TCA cycle or can be converted to ketone bodies.

Uses of Ketone Bodies

Alternative energy source for organs during fasting or low glucose availability.

Formation of Acetoacetate

A ketone body formed in the liver from excess acetyl-CoA.

Role of Propionyl-CoA

Intermediate in the metabolism of odd-chain fatty acids.

Implications of a Heart Attack

Metabolic shifts leading to increased lactate and energy failure.

Biochemical Mechanism of Hormone Action

Hormones like epinephrine activate or inhibit metabolic pathways.

Blood Fat Transport Dynamics

The transport of dietary and endogenous fats through lipoproteins.

Enzymatic Action in Lipolysis

Enzymes like HSL that break down triglycerides into fatty acids and glycerol.

Clinical Significance of Metabolic Pathways

Understanding these pathways is crucial for diagnosing and treating metabolic disorders.

Hydrophobic vs. Hydrophilic

Lipids are hydrophobic; they do not dissolve in water but dissolve in fat-like solvents.