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198 Cards in this Set
- Front
- Back
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What are the five functions of membranes?
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Boundary and permeability - compartmentalize
Working platforms/surface area Transport regulation of molecules and ions Signaling Cellular growth and motility |
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What macromolecule is important for energy storage, membrane structure, and specific biological functions?
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Lipids
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What is the distinguishing feature of lipids?
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Hydrophobic Nature
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What type of molecule has three fatty acids linked to glycerol via an ester linkage?
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Triacylglycerol
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What do triacylglycerols form in the body?
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Fat
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What is the major component of cell membranes in animals?
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Phospholipids
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What is the most common form of phospholipid found in the cell?
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Phosphatidylcholine
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What type of lipid is often found in neural tissues?
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Spingolipids
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Where is spingomyelin found?
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In the membranous myelin sheath surrounding nerve cell axons.
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What is a genetic disorder caused by insufficient activity of an enzyme that breaks down sphingolipids?
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Tay-Sachs Disease
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What are most animal glycolipids?
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Sphingoglycolipids
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Where are glycolipids mostly located?
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On the extracellular surface of the plasma membrane
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What are the two functions of glycolipids?
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Protection
Cell Recognition |
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What are sterols?
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A carbon skeleton made of four linked rings. Cholesterol in animal cell membranes is one example.
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What do sterols provide when incorporated into membranes?
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Increased membrane fluidity.
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How are sterols incorporated into membranes?
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Hydrogen bound to phospholipids
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What do amphipathic phospholipids spontaneously form in water?
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A lipid Bilayer
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How are phospholipids added to the membrane?
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They are produced in the smooth ER, and then sent to the cytosolic monolayer. Flippases then facilitate the flip to the other monolayer to provide symmetric growth.
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Where are sugars added to the membrane strucure?
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In the Golgi body
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What are lipid rafts?
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localized regions of a plasma membrane where elevated levels of cholesterol, protein, and sphingolipids are found.
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What causes lipid rafts to be thicker and more viscous than the surrounding phospholipid layers?
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The longer and saturated hydrocarbon chains of sphingolipids
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Where are organizing centers for the assembly of signaling molecules, influencing membrane fluidity, membrane protein movement, and regulation of neurotransmission located on the cellular membrane?
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Lipid Rafts
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What are four functions of transmembrane proteins?
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Transporters
Anchors Receptors Enzymes |
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What are the three types of transmembrane proteins?
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Single Pass
Multi Pass Beta Barrel |
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What are three types of proteins that are associated with membranes (Integral membrane proteins)?
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Transmembrane proteins
Membrane (monolayer)-associated proteins Lipid-linked proteins |
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What are peripheral membrane proteins?
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Proteins that are bound indirectly to one or the other bilayer surfaces by weak, noncovalent interactions with other membrane proteins.
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What type of membrane proteins are difficult to isolate for studies?
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Integral membrane proteins
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What type of membrane proteins are easy to isolate for biochemical studies?
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Peripheral Membrane Proteins
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What are proteoglycans?
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Membrane proteins with long polysaccharides attached.
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What method is used for visualizing transmembrane proteins?
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Freeze Fracture w/TEM
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(T/F) Most lipid components of the membrane are rigid and immobile
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False: Most lipid components of the membrane are in constant motion
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How are lipid molecules held together?
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By weak hydrophobic and van der Waals forces
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What are the three different movements that lipid molecules can undergo in a membrane?
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lateral diffusion
rotation transverse diffusion |
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What type of evidence is given for the lateral diffusion of proteins?
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Cell Hybridization - The diffusion of differently fluoresced proteins when a mouse cell and human cell were combined into a hybrid cell.
Fluorescence Recovery after photobleaching (FRAP) |
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How can lateral mobility of plasma membrane proteins be restricted?
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They can be tethered to cell cortex inside cell
Tethered to ECM molecules outside the cell Tethered to other proteins in adjacent cell |
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What are the factors that affect membrane fluidity?
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Length of the fatty acids - (Shorter the fatty acid tails, more fluid the membrane)
Degree of unsaturation - (Unsaturation hinders close packing and increases fluidity) Sterol content - (At low temperatures sterols increase fluidity) |
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What is the ability to move ions and organic molecules across membranes selectively?
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Transport
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What two factors does a selectively permeable membrane regulate?
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Type and Rate of Molecular Traffic
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What molecules can pass through the lipid bilayer without the need for transport proteins?
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Small uncharged, polar and nonpolar (gasses) molecules
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What is the direct, unaided net movement of molecules into and through the lipid bilayer according their concentration gradient?
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Simple diffusion
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How are high rates of solute movement achieved?
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Through membrane transport proteins
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What are two types of membrane transport proteins?
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Transporters and channels
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What is passive (facilitated) transport?
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Movement driven by concentration gradient of solute and electrochemical gradient
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What is active transport?
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Movement of solutes against their concentration gradients
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What type of transporter transports a single solute across the membrane passively down the concentration or electrochemical gradient?
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Uniport
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What type of transporter transports two different solutes simultaneously or sequentially?
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Coupled transporters
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What type of coupled transporter transports two solutes in the same direction?
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Symport
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What type of coupled transporter transports two solutes in opposite directions?
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antiport
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What are pumps?
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Transporters that move solutes against their electrochemical/concentration gradient via the direct input of energy from ATP hydrolysis or light.
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What side of the membrane is normally negative?
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The cytosolic side of the membrane
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What is the net force driving charged molecules and ions across a membrane (concentration and voltage gradient across a membrane)?
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The Electrochemical gradient
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How do coupled transporters overcome the energy needs of active transport?
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They couple the uphill transport of one solute across the membrane to the downhill transport of another.
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What type of pump is the Sodium and Potassium pump?
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ATP-driven Pump
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What cellular pump helps to maintain osmotic balance in animal cells in addition to the membrane potential?
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Sodium-Potassium Pump
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About how much ATP use constitutes the Sodium Potassium pump?
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Approximately 30%
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What is a coupled transporter?
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A collaboration between an ATPase pump and a symport/antiport (2 Stages, 2 separate transmembrane proteins)
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How does a coupled transporter work?
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It uses an ATPase pump to restore a concentration gradient, which is used in a symport/antiport to provide an indirect active transport of solute molecules
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What is the glucose-Na+ symport and glucose uniport functionally coupled to?
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A Na+ - K+ pump
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In the gut epithelial cells, where is the glucose Na+ symport located?
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On the apical surface
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In gut epithelial cells, where is the glucose uniport located?
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The lateral and posterior cell surfaces.
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What are the five types of transmembrane channel proteins?
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Porins, aquaporins, gap junctions, plasmadesmata, and ion channels
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What are protein-protein junctions between certain animal cell types?
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Gap Junctions
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What molecules generally pass through gap junctions?
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Small intracellular signaling molecules and ions
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How do ion channels provide selectivity?
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By the size of the pore and the distribution of the charged amino acids in the pore
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What is the rate of transport of ion channels?
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Very Fast @ almost one million ions/sec
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(T/F) Most ion channels are gated.
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True!
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What are the two types of gated channels?
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Voltage-Gated
Ligand-Gated |
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Where are mechanosensitive channels often located?
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In the auditory chambers
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What are three activated carrier molecules produced during the citric acid cycle?
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ATP
NADH FADH2 |
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What are the most important of the activated carrier molecules?
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ATP and NADH
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How does ATP store energy?
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In the readily transferable chemical groups (phosphates)
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How does NADH store energy?
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Through high-energy electrons
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About how many ATP molecules are found in a cell?
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10^9 ATP/cell
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About how long does turnover of the ATP pool take?
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1-2 mins
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What are the two ways animal cells make ATP?
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Substrate-Level phosphorylation (ADP + Pi --> ATP)
Oxidative Phosphorylation (ATP generation from NADH) |
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What are the three stages of cellular metabolism?
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Digestion
Partial Oxidation (Glycolysis) Complete Oxidation (Citric Acid Cycle) |
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Where does the citric acid cycle take place?
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Inside the mitochondial matrix
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Where does glycolysis take place?
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In the cytosol
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Does glycolysis require oxygen to take place?
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No
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What is the net outcome of glycolysis?
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2 molecules of Pyruvate
2 ATP molecules (4 are produced and 2 are used) 2 Molecule of NADH |
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During glycolysis what is created when the 6-carbon sugar is cleaved?
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Two 3-carbon sugars
Glyceraldehyde-3-phosphate |
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What three purposes do the phosphate groups on sugars serve?
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The negatively charged phosphates render the intermediates impermeable through the cell membrane
Serve as binding/recognition groups during the formation of enzyme-substrate complexes Provide a level of conservation in terms of energy. |
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What is the central reaction of glycolysis (Where 1 molecule of ATP and NADH are produced)
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The conversion of Glyceraldehyde 3-phosphate to 3-phosphoglycerate
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What is the result of the oxidation of glyceraldehyde 3-phosphate with Pi and NAD+?
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1,3- bisphosphoglycerate
NADH H+ |
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What enzyme is required for the oxidation of glyceraldehyde 3-phosphate?
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Glyceraldehyde 3-phosphate dehydrogenase
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What enzyme catalyzes the creation of 3-phosphoglycerate + ATP from 3-bisphosphoglycerate + ADP?
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phosphoglycerate kinase
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During which steps of glycolysis does substrate level phosphorylation take place?
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Step 7 and Step 10
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Which steps during glycolysis are examples of coupled reactions?
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Steps 6 and 7 (When G3P is converted to 1,3-bisphosphoglycerate coupled with the oxidation of G3P and adding a Pi & 1,3-bisphosphoglycerate is converted to 3-phosphoglycerate through hydrolysis (coupled with ATP generation))
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What is produced from Pyruvate in the absence of oxygen?
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Lactate
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Where are the enzymes required for the oxidation of pyruvate and fatty acids to acetyl-CoA and for the citric acid cycle located?
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In the mitochondrial matrix
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Where are the enzymes for nucleotide phosphorylation located?
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In the intermembrane space
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Where are transport proteins that allow the passage of metabolites into and out of the matrix located?
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The inner membrane
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Where does the electron transport chain take place?
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The inner mitochondrial membrane
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Where is the ATP synthase located?
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The inner membrane
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Where are most porins located in the mitochondria?
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Outer Membrane
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Where are the enzymes of lipid synthesis located?
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Outer Membrane
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What causes the intermembrane space of mitochondria to be chemically equivalent to the cytosol?
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The transport proteins called Porin
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What enzyme complex aids in decarboxylating pyruvate?
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Pyruvate dehydrogenase complex
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How many enzymes are found in the pyruvate dehydrogenase complex?
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Three
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(T/F) The conversion of pyruvate to acetyl CoA is reversible
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False, this reaction is irreversible.
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Why is acetyl CoA an activated carrier?
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It has a high-energy linkage in the thioester bond
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How many carbon atoms are found in the second molecule citrate in the citric acid cycle?
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Six
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How many carbon atoms are found in the last step of the citric acid cycle, oxaloacetate?
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4
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Why are there so many steps in the citric acid cycle?
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The purpose of the citric acid cycle is to harvest energy. Therefore the oxidizing of many different molecules provides the greatest potential for energy harvest.
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What does one turn of the citric acid cycle produce?
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3 NADH
1 FADH2 1 GTP 2 CO2 |
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Why is oxygen required for the citric acid cycle when oxygen is not utilized in any of the reactions in the cycles?
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Oxygen is required for the regeneration of NAD+
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What types of diseases are the result of mutations in succinate dehydrogenase and fumarase genes?
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Neurodegenerative diseases (encephalopathy)
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In what direction is mRNA read during translation?
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5' to 3'
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What are adaptor molecules used in translation?
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tRNA
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Where can mismatches often be tolerated during translation?
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The third position of the codon
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What enzyme is responsible for the recognition and attachment to the correct amino acid in tRNA?
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Aminoacyl-tRNA synthases
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(T/F) Each amino acid has its own synthetase enzyme.
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True
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How does the aminoacyl-tRNA synthetase activate an amino acid for protein synthesis?
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It provides for the AMP linkage to the carboxyl group of the amino acid, which provides the ester linkage to the tRNA.
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In what direction does the protein chain grow?
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The N-Terminal to the C-Terminal End
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What subunit of the ribosome catalyzes the formation of the peptide bonds that link the amino acids together?
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The large subunit
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What subunit of the ribosome matches the tRNAs to the codons of the mRNA?
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The small subunit
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What happens to the subunits of the ribosome when the protein synthesis is finished?
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They separate
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What are the three sites located in the ribosome?
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The E-site
The P-site The A-site |
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Where does the tRNA enter in the ribosome?
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The A-site
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In what site of the ribosome is the polypeptide chain held?
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The P-site
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Where can deactivated tRNA's often be found in the ribosome?
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The E-site
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What is a ribozyme?
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RNA that possesses catalytic activity
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What is the start codon sequence?
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AUG
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What is required for the initiation of translation?
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initiator tRNA
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What amino acid is always found on the initiator tRNA?
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methionine
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What is the first step in protein synthesis initiation?
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Initiator tRNA and translation initiation factors bind to the P-site of the small ribosomal subunit, which then binds to the 5' end of the mRNA
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What is the second step in protein synthesis initiation?
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The small subunit moves 5'-3' searching for AUG
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When does the large subunit bind to complete the ribosome?
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After the small subunit finds AUG and loses the translation initiation factors
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What are the three stop codons?
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UUA
UAG UGA |
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What recognizes the stop codons?
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The Ribosome
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What happens when the ribosome encounters a stop codon?
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Causes release factors to bind to the stop codon that reaches the A-site
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What frees the carboxyl end of the polypeptide chain during translation?
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The addition of a water molecule instead of an amino acid
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What are polyribosomes?
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Large cytoplasmic assemblies of several ribosomes spaced as close as 80nt pairs apart along mRNA
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What are inhibitors of procaryotic protein synthesis used as?
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Antibiotics
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What molecule is employed to repair damaged or partially denatured proteins caused by temperature increases?
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Molecular Chaperones
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What are two examples of eucaryotic molecular chaperones?
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Hsp70 and Hsp60
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How does Hsp protein help the target protein to refold?
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The repeated binding and releasing with the help of ATP
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What enzyme degrades proteins?
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Proteases
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What is a proteasome?
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A protein destruction machine (complex protease - ATP dependent)
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What signals protein destruction?
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The attachment of ubiquitin
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How is ATP produced from NADH and FADH2?
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Through the electron transport chain
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What does the transfer of electrons along the inner mitochondrial membrane generate?
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An electrochemical proton gradient
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What is chemiosmotic coupling?
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The process of ATP synthesis based on the energy of proton gradient
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What does the electron transfer power?
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The proton pump
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Who won the nobel prize in Chemistry 1978 for the discovery of the chemiosmotic theory?
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Peter D Mitchell
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What are the essential requirements for chemiosmotic coupling?
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Inner mitochondrial membrane
Source of high-energy electrons (NADH) Two sets of protein complexes in membrane (to transfer electrons, pump protons, and to synthesize ATP) Protons |
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What is a usual lipid in the inner mitochondrial membrane?
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Cardiolipin
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Why is cardiolipin found in the inner mitochondrial membrane?
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It helps to make the membrane especially impermeable to ions
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What is a hydrogen atom with an extra electron called?
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A Hydride Ion
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What is the final acceptor of electrons in the electron transport chain?
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Oxygen
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What is the pathway of the electron transport chain?
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NADH Dehydrogenase Complex -->
Ubiquinone --> Cytochrome b-c1 complex --> Cytochrome c --> Cytochrome Oxidase Complex |
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(T/F) Each complex of the electron transport chain is the site of proton pumping.
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True
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What is the measure of electron affinities?
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The Redox Potential
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What is an example of a redox pair?
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NADH and NAD+
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A large negative redox potential would indicate?
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A weak affinity for electrons and a strong tendency to donate electrons. (NADH/NAD+)
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What would a large positive redox potential indicate?
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A strong affinity for electrons and a strong tendency to accept electrons.
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Why do electrons flow along the electron transport chain?
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The Redox potential increases along the mitochondrial electron-transport chain
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What is the rate of ATP production of the ATP synthase protein?
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more than 100molecules of ATP/sec
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About how many protons need to pass through the synthase to make one molecule of ATP?
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About 3 protons
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What is the total ATP yield per molecule of glucose?
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30
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About how many molecules of ATP are produced from 1 molecule of NADH?
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2.5
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Where are heme groups found in the electron transport chain?
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In the cytochromes
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Where are the iron-sulfur centers found in the electron transport chain?
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NADH dehydrogenase complex
Cytochrome b-c1 |
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Where are copper atoms found in the electron transport chain?
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Cytochrome oxidase complex
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What is the only molecule in the electron transport chain that is not a protein and does not use metals to carry electrons?
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Ubiquinone
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What reaction uses about 90% of the oxygen we breathe?
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The cytochrome oxidase catalyzing oxygen reduction
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What is electron tunneling?
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The jumping of elections (between the metal atoms in the electron transport chain)
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What makes cyanide and azide poisonous?
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They bind to cytochrome oxidase to stop electron transport
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What do uncoupling agents do?
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They render the innermitochondiral membrane permeable to protons.
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What is an example of an uncoupling agent?
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2,4-dinitrophenol
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Where can uncoupling be naturally found?
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In brown fat cells
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What is the most prominent organelle of the plastid family?
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The Chloroplast
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What is the inner membrane system called in chloroplasts?
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Thylakoids
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What is the term for stacked thylakoids?
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Grana
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Where is the site of photosynthesis?
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In Chloroplasts
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What is NADPH used in?
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Reductive Biosynthetic Reactions
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In what photosynthesis step do electron-transfer reactions take place?
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The light reactions
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In what part of photosynthesis do the carbon-fixation reactions take place?
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The dark reactions
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Where does the chlorophyll obtain its electrons?
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Water
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How does the light reaction produce oxygen?
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From water via the water-splitting enzyme
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What is used to convert CO2 to carbohydrate?
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ATP and NADPH
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Where in the chloroplast does carbon fixation take place?
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In the stroma
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What is formed from carbon fixation?
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glyceraldehyde-3-phosphate
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Where do the light reactions take place?
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In the thylakoid membrane
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What are the primary colors absorbed by chlorophylls?
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Blue and Red light
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What are photosystems?
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Large multi-protein complexes with antenna and photochemical reaction centers
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What is the term for the cluster of chlorophyll and accessory molecules?
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Antenna Complex
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What are accessory molecules in photosynthesis?
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Carotenoids
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What is the term for the virtual photon passing?
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Forester resonance energy transfer
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Where do the virtual photons get passed to from the antenna complex?
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The photochemical reaction center
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In what photosystem is ATP synthesized?
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Photosystem II
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In what photosystem is NADPH synthesized?
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Photosystem I
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What is the pathway of photosynthesis?
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PS II -->
Plastoquinone --> Cytochrome b6-f complex --> Plastocyanin --> PS I --> Ferredoxin --> Ferrodoxin NADP+ reductase |
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What enzyme in the photosynthesis pathway serves as a proton pump?
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Cytochrome b6-f complex
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What enzyme catalyzes the dark reaction?
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Rubisco
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What does carbon dioxide react with to begin the calvin cycle?
|
ribulose 1,5-bisphosphate
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How many molecules of carbon dioxide will produce one new molecule of glyceraldehyde 3-phosphate?
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Three
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What is the net cost of generating one new molecule of glyceraldehyde 3-phosphate?
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nine molecules of ATP and six molecules of NADPH
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