Lipids Flashcards
Name two classes of lipids.
Storage and membrane
Name a primary function of membrane lipids.
They form boundaries around the cell and intracellular organelles
True or false: membrane lipids are semi-permeable barriers.
True
Membrane proteins are involved in ________ processes.
Signalling
True or false: all membrane lipids contain carbohydrates.
False
Membrane lipids may be amphipathic or ___________.
Amphiphilic
How many polar, or hydrophilic, heads does a membrane lipid have?
One
True or false: lipids may have one or two nonpolar, or hydrophobic, tails.
True
The polar phosphorylated headgroup, the three-carbon glycerol backbone, and the two nonpolar, hydrocarbon fatty acid chains are components of which type of membrane lipid?
Glycerophospholipid
The phosphorylated headgroup of a glycerophospholipid varies by membrane lipid, and is attached to the _____ of the lipid’s backbone.
C3
Two fatty acid chains are attached to C1 and ____ of the membrane lipid’s backbone.
C2
Name the simplest glycerophospholipid.
Phosphatidic acid
Sphingolipids have a __________ backbone.
Sphingosine
Sphingolipids have one fatty acid tail, but two __________ chains.
Hydrocarbon
True or false: different sphingolipids can be formed by varying headgroups.
True
What is the most abundant type of sphingolipid?
Sphingomyelin
What is the simplest sphingolipid, with a hydrogen headgroup?
Ceramide
Name the headgroups observed on sphingolipids.
Choline and ethanolamine
Cerebrosides and gangliosides are also derived from sphingosine, and have one or more ______ residues in their headgroup
Sugar
Galactocerebrosides have a single galactose residue and are predominately found in ________.
Neurons
Most of the cholesterol in the body is ________ in origin
Dietary
Cholesterol is insoluble in blood, so it is transported in the circulatory system, bound to one of a variety of ___________.
Lipoproteins
True or false: water-soluble proteins can carry cholesterol in the blood.
True
Name the main two types of cholesterol found in the body.
Low-density lipoprotein (LDL) and high-density lipoprotein (HDL)
Large numbers of _____ __________ _________ molecules are associated with the presence of atheromatous disease within the arteries
Low-density lipoprotein
Name the hard substance formed by inordinate levels of high-density lipoprotein, which can cause strokes and heart attacks.
Plaque
High-density lipoprotein molecules transport cholesterol back to the _______ for excretion, and a large amount of high-density of lipoprotein is congruent with better outcome.
Liver
True or false: cholesterol imbalances can be restored, in many cases, via diet and lifestyle changes.
True
Fatty acids are _______ acids with hydrocarbon chains of 4-36 carbons
Carboxylic
Saturated acids contain no double bonds, and the tail is __________.
Straight
Unsaturated acids have one or more double bonds, and the tail is __________.
Twisted
True or false: almost all naturally-occurring unsaturated fatty acids are in the trans configuration.
False
What accounts for the poor solubility of fatty acids in water?
Nonpolar hydrocarbon chains
When required, phospholipase-A cleaves arachidonic acid from the _________ backbone.
Glycerol
Eicosanoids are used for ________ hormones, reproductive function, inflammation, pain, fever, etc.
Endocrine
Name three forms of lipid aggregates.
Micelles, bilayers, and liposomes
The following describes which type of lipid aggregate?
‘Fatty acid salts, which contain only one fatty acid chain. Hydrophobic fatty acids are hidden in the interior. Hydrophilic headgroups interact with the surrounding water molecules, and the aggregates are usually very small, but the size varies by length of fatty acid chain.’
Micelles
The charged head of a bilayer is aimed towards the _________ environment, and the tails point towards each other.
Aqueous
When are stable, water-enclosing liposomes formed?
They are formed when a lipid bilayer folds back on itself to create a hollow sphere.
Bilayers lead to the formation of _________ sheets.
Bilipid
True or false: inner and outer leaflets are formed within a bilayer.
True
True or false: bilayer leaflets are induced by proteins to self-assemble in aqueous conditions.
False
Name a force which holds bilayer leaflets together.
van der Waals
No _________ bonds exist between lipids.
Covalent
Name two methods by which lipids may move in within the plane of either the outer or inner leaflet.
Lateral and rotational
True or false: transverse movement between bilayer leaflets is readily achieved.
False
Name the type of enzyme that allows for the movement of polar headgroups.
Flippase
State three ways in which membrane fluidity can be altered.
Heating the lipid to a gel consistency, increasing the degree of unsaturation, and transition temperature
What does the fluidity mosaic model display?
Membranes are free to diffuse laterally, but cannot move from one side of the bilayer to the other
Integral membrane proteins are tightly bound to the membrane, through interactions with the __________ core of the bilayer.
Hydrophobic
Most integral proteins have one or more regions of the _____________ chain that span the lipid bilayer, and interact noncovalently with the hydrophobic fatty acid chains.
Polypeptide
True or false: lipids, integral proteins are amphipathic, having both hydrophobic and hydrophilic regions.
True
How do peripheral membrane proteins bind to the lipid bilayer, compared to integral membrane proteins?
They are usually bound to the membrane by hydrogen bonding and ionic attraction. Some are attached to the bilayer via an embedded fatty acid. This anchors the protein to the membrane.
Name two characteristics of the phospholipid bilayer.
Permeability to water, gases, and small, uncharged molecules, as well as impermeable to large molecules, such as amino acids.
True or false: passive transport requires energy.
False
Which type of transport does the following describe? ‘Requires an input of metabolic energy, as molecules are being transported against their concentration gradient. This energy can be derived from either the hydrolysis of ATP, or by coupling the movement of the molecule to the movement of an ion down its concentration gradient. In the case of ATP-driven active transport, the energy is derived from the sodium-potassium-ATPase pump.
A high internal concentration of potassium, and a low internal concentration of sodium is maintained.’
Active transport
Name a type of transport used in the phospholipid bilayer.
Facilitated diffusion
What is a uniporter, and what is its purpose?
Facilitated diffusion of a molecule is dependent on specific integral membrane proteins, called uniporters.
The protein undergoes a conformational change, and the transporter is specific for one particular molecule, or a group of molecules.
Symporters move molecules and ions in the ______ direction.
Same
Antiporters move molecules and ions in the ______ direction.
Opposite
What is the technical term for a signaling molecule?
Ligand
What does the binding of a molecule to a ligand induce?
A conformational change in the receptor, which initiations a series of reactions, termed ‘signal transduction’, leading to a change in cellular function.
Endogenous ligands are generally _________.
Hormones
List three functions of membranes.
Structure, conduction of nerve impulses, and signal transduction
Triacylglycerols are the scientific term for:
Storage lipids
Simple triacylglycerols have _____ identical fatty acids; mixed triacylglycerols have two or three different fatty acid chains.
Three
___________ store large amounts of triacylglycerols, in the form of fat droplets. They are used as energy stores, and as insulation.
Adipocytes
True or false: triacylglycerols are nonpolar lipids.
True
Triacylglycerols serve what purpose?
Fuel storage
