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Definition
-Separate cell contents from environment.
-Isolate cellular compartments.
-Regulate entry and exit of materials.
-Detect and transmit signals.
-Composed mainly of lipids and proteins. |
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Definition
| Used to describe phospholipid bilayer. Hydrophilic phosphate heads pointed outwards and hydrophobic tails inside membrane. |
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Definition
Contain carboxyl group at end of hydrocarbon chain. In unsaterated fatty acids, most of the double bonds are in the cis formation.
Trans fats can increase the risk of cardiovascular disease.
Hydrogenation can convert double bonds to singe bonds, but can also convert some cis bonds to trans bonds. |
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Definition
| Fats are linked to glycerol molecule via condensation reactions that form ester bonds. Used for storage of fats and are a precursor to phospholipids (have no function). Usually 3 different fatty acids are attached to the glyceride. |
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Term
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Definition
| Phospholipids that are based on glycerol. Are named after the R-group (phosphatidyl-"R-group"). Fatty acid not taken into account when naming. The polar headgroup is oriented in the opposite direction to the fatty acid (due to hydrophobic.hydrophilic interactions). Examples: phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylserine. |
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| Packing of Membrane Lipids |
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Definition
| TAG's and fatty acids not suited for membrane construction (there shape leads to gaps). Phospholipids have ideal shape. |
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Definition
Dominant phospholipid in animal cells. Sphingosine backbone (composed of serine and a palmetic acid derivative. Equivalent of fatty acid on C1. Needs fatty acid to be linked to C2 via amine bond.
Sphingomyelin: Present in myelin sheath. |
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Definition
| 4-ring/hydrocarbon tail structure. Sterols vary in the length/branching of the hydrocarbon tail and in the position and number of methyl groups on the rings. Have hydroxyl group on the the C3. |
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Definition
| Chains of five carbon isoprene (can also form rings). No functional role in membranes. Vitamins A,D, and K synthesized from isoprene. Ubiquinone is a co-enzyme that contains an isoprenoid unit (it carries e-/protons in e- transport chain). |
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Term
| Structure of Phospholipid Bilayer |
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Definition
| Held together via van der waals interactions. Phospholipids constantly detaching/reattaching. Greater variety in phospholipids broadens transition (melting) range. Cholesterol broadens transition range. |
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Term
| Action of Cholesterol in Membranes |
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Definition
| Inserts into membranes and creates spaces that reduce hydrophobic interactions (increases fluidity at low temperatures). OH group on cholesterol bonds with fatty acid. reducing it's motility (decreases fluidity at high temperatures). |
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Term
| Movement of Phospholipids in Membrane |
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Definition
| Phospholipids undergo rapid lateral diffusion and very slow transverse diffusion (flip-flop). Transverse diffusion carried out by proteins called flipases (or translocases). |
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Term
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Definition
Integral/Intrensic proteins: Are amphipathic and can pass all the way through the membrane or part way through the membrane.
Peripheral/extrinsic proteins: entirely hydrophobic. Are on protein surface.
Lipid-linked/Anchored: Attached to membrane via protein or oligosaccharide. |
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Term
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Definition
Attachment via amino acids: Hydrocarbon tail linked to cysteine of glycine. Iso-prenoid always linked to cysteine (prepylated).
Attachment via oligosaccharides: Only found on outside of cell. Protein linked to phospholipid via chain of sugars. Lipid raft: Combined cholesterol and sphingophospholipids +lipid anchored proteins. |
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Definition
| Only cell membrane has glycoproteins/glycoproteins on outer surface. Follows fluid mosaic model. |
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Term
| Permeability of Membranes |
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Definition
| Gases and small hydrophobic molecules can pass through. Small uncharged polar molecules will sometimes pass through (water has a lot of trouble going through membrane). Larger uncharged polar molecules will not cross molecule. Ions will not cross membrane. |
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Term
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Definition
| Passive transport. Found in bacteria, chloroplast, and mitochondria membranes. Consist of three beta barrels that can allow diffusion (center channel may or may not allow for diffusion). OmpF porins can allow matter as larger as 600 M.W. though. OmpF channel contains loop of amino acids with negatively charged carboxyl groups on them (means that positively charged molecules cannot pass through. Specificity of porins based on molecular weight and charge. Aquaporin allows H20 diffusion. |
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Term
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Definition
| Facilitated diffusion. Very specific, usually only allow one type of ion through. Have amino acids that act as selective filter. Have maximum rate of diffusion (become saturated). Are regulated to allow passage of ions only when needed and only in the quantity needed. |
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Term
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Definition
-Can be blocked with protein "plug".
-Can change shape to close.
-Can be voltage gated (regulated via membrane potential).
-Ligand gated (intrensic and extrensic).
-Mechanically gated (hair cells in inner ear).
-The substance transported is the stimulus to open the channel. |
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Term
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Definition
Direct active transport (uses ATP) antiporter. Moves ions from low to high concentration. Has small beta subunit that is mostly external and functions in regulation. Alpha subunit crosses membrane multiple times and acts as transporter.
Three Na+ enters transporter from inside cell, transporter is phosphorylated, Na+ is released outside of cell and two K+ enter transporter, phosphate group comes off, K+ is released into cell. |
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Definition
| Indirect active transport (Na+ gradient provides energy). Pump is initially open to outside of cell, Na+ binds allowing glucose to bind, binding causes transporter to change shape and Na+and glucose are released into cell (Na+ is then transported back outside cell via sodium-potassium pump). |
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Term
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Definition
| All signal transduction systems are unique in both the stimulus and the response. Receptor either becomes enzyme or interacts with with other proteins. One reaction in the system usually involves an enzyme that creates a product (second messenger) that effects the behaviour of other proteins. Protein kinases/phosphotases are involved at some point because they can easily regulate other proteins. |
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Term
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Definition
| Beta cells on the islets of langerhans in the pancreas create insulin. Insulin effects muscle cells (increases number of glut 4 proteins that are transporting glucose into cell), liver cells (take in glucose and convert it into glycogen), and adipose cells (stop releasing fatty acids and use the enzyme lipoprotein lipase to take up fats). |
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Term
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Definition
| In both liver and adipose cells: glucagon/epinephrine bind to receptor > receptor interacts with G protein > adenylyl cyclase activates large amounts of cAMP (second messenger), cAMP activates protein kinase A > liver cells stop taking up glucose and instead start releasing it, adipose cells start use the protein hormone-sensitive lipase to convert TAG's into fatty acids that are released into the blood. |
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