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Biochem Exam 3
| Question | Answer |
|---|---|
| What membrane lipid is composed of sphingosine, fatty acid, and a simple sugar? | cerebroside |
| Which lipids contain a branched chain of seven sugar residues? | gangliosides |
| what is an alcohol component in cerebroside? | sphingosine |
| What is the common name of hexadecenoic acid ? | Palmitic acid |
| What is the common name of (18:3) fatty acid? | linolenic acid |
| The systematic name of linoleic acid is _______ . | octadecadienoic acid |
| What carbon atom from the carboxyl terminus of a fatty aicd is often referred to as β? | 3 |
| What lipids are referred to a polycyclic hydrocarbons? | steroids |
| Choose the compound that is composed of a chain of hydrogen-bearing carbon atoms terminated with a carboxyl group? | fatty acid |
| Choose the denotation for the double bond position and conformation in natural oleic acid? | cis-Δ^9 |
| In what form does a fatty acid exist in the physiological pH range? | anion |
| The configuration of most fatty acids in biological systems is predominantly: | cis |
| A(n)_______ in the chain length will result in a formation of _______ van der Waals interactions between the chains and a(n) ______ of the meting point. | . increase; more; increase |
| What linkages are in phosphoglycerides between fatty acids and a glycerol backbone? | ester linkages |
| the common feature of all ω-3 fatty acids is/are:? | several double bonds in the chain |
| What is a term for hydrophobic groups that are covalently attached to proteins and tether them to the membrane? | membrane anchors |
| In proteins, the glycosylphosphatidylinositol anchor is attached to the | carboxyl terminus |
| A precursor to estradiol is | cholestrol |
| How many rings are in the steroid nucleus | 4 |
| What group of living things contains in its cell membranes lipids with ether rather than ester linkages between the fatty acid chains and a glycerol backbone? | archaea |
| What is the main storage form of fatty acids? | triacylglycerols |
| What is the major site of accumulation of triacylglycerols in mammals? | adipose tissue |
| What are derived from the treatment of triacylglycerols with strong bases? | salts of fatty acids |
| Which organism's do NOT have sterols in their membranes? | bacteria |
| The GPI anchor does NOT contain a(n): | cyclopentane ring |
| Derivatives of cholesterol with an alcohol functional group are: | sterols |
| . What is one of the defects that lead to Hutchinson–Gilford progeria syndrome? | The farnesyl group is not removed from the lamin precursor. |
| The presence of cis double bonds in fatty acids limits tight packaging and the number of _____ interactions. | van der Waals |
| Which phospholipid is abundant in the myelin sheath of neural cells? | sphingomyelin |
| Unsaturation on fatty acids________ melting points of lipids, | decreases |
| What corresponds to the polar head group of phosphatidylcholine? | phosphorylcholine |
| Phosphatidylethanolamine does NOT contain a(n) _____ group. | carboxyl |
| Phosphatidylinositol does NOT contain a(n): | amino group |
| Hosphatidylcholine does NOT contain a(n): | hydroxyl group |
| . Cardiolipin does NOT contain a(n): | amino group |
| Phosphatidate does NOT contain a(n): | glucose |
| Eukaryotic cell membranes usually do NOT contain: | triacylglycerols. |
| Which is NOT a function of lipids? | structural rigidity of the cytoskeleton |
| . How many double bonds does octadecatrienoic acid have? | 3 |
| . Which fact about a fatty acid is indicated by the notation 12:2? | There are 12 carbons in the chain with two double bonds. |
| . The longer is the fatty acid, the _____ the fatty acid is/has. | higher the melting point of |
| How many carbons does palmitate have in its chain? | 16 |
| . The backbone of a phospholipid is a: | glycerol |
| At which carbon of glycerol is the polar head group of phospholipids found? | C-3 |
| . What functional group are polar head groups of phospholipids esterified to? | phosphate |
| Identify the differences in archaea membrane lipids compared to those of eukaryotes or bacteria and how these differences help them withstand extreme environmental conditions | The fatty acid chains are branched, allowing them to pack more tightly, thereby protecting membrane integrity. |
| Eating _____ rich in the ω-3 fatty acids protects from: | fatty fish; cardiovascular disease |
| Cholesterol and other steroids are not soluble in blood and therefore must be transported. Predict what chemical modifications must occur for cholesterol to move through the circulatory system | Cholesterol is esterified to a fatty acid for transport by lipoprotein particles, the surface of which is hydrophilic and the interior hydrophobic |
| Which role does the membrane play by separating the cell interior from the exterior and cell compartments from the cell interior? | an interface |
| What should be the approximate length of a phospholipid molecule, considering the average thickness of membranes? | 30–50 ·Å |
| The process of _____ has never been observed. | transverse diffusion of proteins |
| Which property is NOT associated with lipid membranes | solvent for carbohydrates |
| . Which component of membranes provides their impermeability to polar molecules and ions? | . hydrophobic tails of phospholipids |
| Which component of membranes is key to controlling membrane fluidity in prokaryotes? | hydrophobic tails of phospholipids |
| The formation of lipid bilayers is determined by: | hydrophobic interactions |
| . What role do van der Waals interactions play in membranes? | . decrease membrane fluidity |
| Choose the CORRECT statement about membrane permeability. | Entry of sodium ions in the cell can increase membrane permeability for sodium ions. |
| Tm of the membrane is lowest if it is composed of the | cis-Δ^9-hexadecenoate and a lot of cholesterol molecules |
| Lipid rafts: | are small and dynamic regions rich in cholesterol that make phase transitions of the membrane less likely |
| . Why do liposomes have high clinical importance? | Different molecules can be trapped inside such vesicles. |
| What is the typical protein content of mitochondrial membranes? | 75% |
| Associations of proteins with membranes that do NOT exist are: | integral membrane-spanning α helices with polar side groups outside. |
| What property of membranes makes the transverse diffusion of phospholipids across the membrane energetically unfavorable? | . hydrophobic interior of the membrane |
| What type of transport can proceed against a concentration gradient? | active transport |
| What is the origin of the free energy of the Na+ ion gradient | free energy of phosphoryl transfer |
| What will happen upon hydrolysis of 3 ATP molecules by the Na+-K+pump? | 9 Na+ will be transported outside the cell, and 6 K+ will be transported inside the cell |
| . Through which type of ion channels do neurotransmitters usually act? | ligand-gated ion channels |
| Which statement about P-type ATPases is FALSE? | Na+-K+ ATPase binds two ATP molecules to exchange Na+and K+ions. |
| Choose the CORRECT statement about flippases. | Transverse diffusion of phospholipids from the inner to the outer leaflet is accomplished by the ABC transporter |
| The slowest type of molecule transport is: | transverse diffusion of proteins. |
| Potassium ion channels facilitate diffusion because: | the channel provides a concentration gradient. |
| How many carbonyl groups are required to "resolve" a potassium ion in the selectivity filter of the K+ ion channel? | 8 |
| Sodium ions can't pass through the K+ ion channel because they | are too small to be efficiently rehydrated by the channel |
| . What is the driving force for ion movement in the Knock-On model, which suggests that the ions never occupy adjacent sites? | charge repulsion |
| Some tumor cells become more sensitive to a range of drugs as they become resistant to only one drug because they: | obtain the multidrug-resistance protein that transports different drugs from the cell |
| What does NOT determine whether a small molecule will cross a membrane? | replacement of the solvation shell of polar water molecules by nonpolar interactions with the membrane interior |
| Valinomycin is an amphipathic antibiotic that is capable of facilitating diffusion of potassium ions. What would happen in the thought experiment if all of the potassium ion channels were blocked and valinomycin was added to the cells immediately after? | K+ would be transported from the neuron, which would increase the resting potential |
| How would the action potential on a neuron in the resting state change if all of the sodium ion channels were blocked? | action potential wouldn't be generated or propagated |
| What would happen to the neuron if the Na+-K+ ATPase activity would be completely inhibited? | The resting potential wouldn't be restored after the action potential. |
| What is the first step of the action potential? | The flow of Na+out of the cell |
| What would happen to the resting potential if neurons were treated with tetrodotoxin? | no significant changes |
| What is the main cause of repolarization? | The flow of K+ out of the cell |
| The _______ of small molecules is correlated with their relative solubilities in water and nonpolar solvents | permeability |
| Fluorescence recovery after photobleaching has been used to study: | lateral diffusion in membranes. |
| The MOST fluid would be a bilayer made of lipids with | polyunsaturated 16-carbon fatty acids. |
| What describes the role of a protein in the selective permeability of a membrane? | Na+-K+ ATPase activity that sets up an electrical potential across the membrane |
| Which statement is consistent with the structure of biological membranes? | The membrane lipids self-assemble to form the lipid bilayer. |
| . Digitalis is a cardiotonic steroid that does not act like a steroid. Instead, its function is to inhibit: | the Na+-K+ pump |
| An antiporter and a symporter are examples of: | a secondary transporter |
| The MOST common motif found in membrane-spanning proteins is: | . α helices of nonpolar amino acids that pass through the membrane. |
| . Would you agree that a peripheral membrane protein can act as Na+-K+ ATPase? Why? | . No, because a peripheral protein does not form a transporter across the entire membrane |
| What evidence exists to show that membrane asymmetry can be preserved for long periods | Transverse diffusion of proteins has not been observed. |
| . If you want to study how membranes regulate their curvature and budding processes, what membrane structures would you study? | presence of lipid rafts |
| What force(s) stabilize(s) lipid bilayers? Select all that apply. | van der Waals interactions, electrostatic bonding between the polar heads and surrounding water, hydrogen bonding between the polar heads and surrounding water |
| . Choose the proper order of permeability of molecules across a membrane, from the most to the least permeable molecules | water, indole, glucose, sodium ion |
| What is the main fuel for the brain and red blood cells? | glucose |
| Taking into account the daily glucose requirement in a typical adult human being, calculate the weekly requirement for the whole body. | 1120g |
| . What are the glycolytic enzymes? | pyruvate kinase and phosphofructokinase |
| What is the reason active skeletal muscle forms lactate through lactic acid fermentation? | The rate of glycolysis exceeds the rate at which muscle can process pyruvate aerobically. |
| Why is gluconeogenesis not a reversal of glycolysis? | . Glycolysis comprises irreversible steps which are bypassed in gluconeogenesis by gluconeogenic enzymes. |
| Which of the following statements is TRUE? | Pyruvate carboxylase requires biotin during carboxylation of pyruvate |
| What are the consequences of biotin deficiency? | lethargy and depression |
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