PSIO 303 EXAM 1 QUESTIONS WITH 100% SOLVED SOLUTIONS

What are sphingomyelins? - Sphingolipids where the head group is phosphocholine or phosphoethanolamine. What prevents cells from actually swelling? - It is effectively impossible for sodium to enter the cell (due to pump and lack of sodium channels). There is a high sodium ion concentration outside the cell which prevents water from entering in the cell Why would cells have a tendency to swell? - Because cytoplasm contains negatively charged proteins that cannot exit, so cells naturally gain water and swell What happens when Na+ homeostasis fails? - Cells gain water and swell What is paracrine signaling? - When the hormone released from a cell acts on a neighboring cell What is endocrine signaling? - hormones released from a cell affect other cells throughout the body What is autocrine signaling? - cell signals itself What is the response of a typical cell when potassium channel close? - Depolarization Why is sodium ion concentration low inside the cell? - 1) Impermeability of the membrane 2) Na+/K+ pump that pumps 3 Na+ out and 2 K+ in *Low sodium inside the cell = a healthy cell Do vesicles have lipid membranes? - YesWhat are peripheral membrane proteins? - proteins that bind to the membrane without passing through it (usually noncovalently bonded to an integral membrane protein) What are integral proteins? - -Proteins that penetrate the hydrophobic core of the lipid bilayer. -Have membrane spanning domains -Some are linked to membrane phospholipids or fatty acids What are the characteristics of phosphoglycerides (phospholipids)? - 1) Amphipathic 2) Main lipid constituent of plasma membrane 3) Glycerol backbone + 2 fatty acyl tails in ester linkage + one polar head group (can have various sizes of head groups) What are sphingolipids? - phospholipids built on a sphingosine backbone What are glycosphingolipids? - They have a sphingosine backbone, a sugar, and a fatty acid tail What are the characteristics of sphingolipids? - 1) Amphipathic 2) Sphingosine backbone (1 tail) + 1 fatty acid tail + polar head group composed of a carbohydrate (ganglioside) or a phosphate ester of an alcohol (sphingomyelin) What is the width of the lipid bilayer? - 5-6nm What are the characteristics of cholesterol? - 1) Amphipathic2) Is a sterol 3) Essential to the membrane 4) Wedges into bilayer and has effect on fluidity by interacting with hydrocarbon groups on phospholipid tails What are the two ways that lipids can move within the bilayer? - Lateral diffusion and rotation What is the difference between saturated and unsaturated fatty acids? - Saturated = no double bonds Unsaturated = one or more double bonds What are the two parameters that the resting membrane potential depends on? - 1) Ion gradients 2) Ion channels (membrane permeability) What are the concentrations of Na+ and K+ inside and outside the cell? - Na+: Low inside the cell, high outside the cell K+: High inside the cell, low outside the cell Are K+ channels present in all cells? - Yes What is the purpose of NaK-ATPase? What does it do? Is it found in all cells? - -Na/K-ATPase develops and maintains steady state ion gradients in cells (NOT EQUILIBRIUM) -It hydrolyzes ATP to do this-Yes it is found in all cells Explain how membrane voltages are established by potassium leak channels - - Potassium is pumped into the cell by the Na/K-ATPase. - Potassium can then leak out of the cell through the K+ leak channels. Potassium is going down its concentration gradient by doing this, which causes a voltage to occur across the membrane. There is a net negative charge established inside the cell and a net positive charge established outside the cell