PSIO 303 EXAM 1 QUESTIONS WITH 100% SOLVED SOLUTIONS
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Module
PSIO 303
Institution
PSIO 303
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 outs...
PSIO 303 EXAM 1
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? - Yes
,What 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) Amphipathic
, 2) 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
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