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LIFESCI 2- Midterm Exam Guide - Comprehensive Notes for the exam ( 76 pages long!)


Department
Life Sciences
Course Code
LIFESCI 2
Professor
Avedian, A.
Study Guide
Midterm

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UCLA
LIFESCI 2
MIDTERM EXAM
STUDY GUIDE

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CELL MEMBRANES
Plasma Membranesselectively permeable barriers that separate cells from external
environment
o An interface for cells where info is received
o Allows cells to maintain constant internal environment
o Has molecules responsible for binding and adhering to adjacent cells
o 2 faces = asymmetrical
o Needed to distinguish itself from surroundings & to be selective about what goes in and
out
Lipid Bilayers
o Amphipathic: have hydrophilic (polar) & hydrophobic ends (nonpolar)
o Hydrophobic molecules can diffuse freely through
o Pure LB acts as one kind of selectively permeable barrier
Cell membranes are fluid
o Permeable to water
Will move from low concentration of solute to high solute to even out the
concentration
o Frye & Edidin: showed that if 2 cells fuse together, their membrane components will
mix
Led to "fluid mosaic model"
o Some organisms increase number of double bonds in lipid bilayers when temp
decreases (increase temp = not too fluidity)
Will add "kink" in the structures so phospholipids will be more spread out rather
than tightly packed
Unsaturated = more kinks, not tightly packed, liquid at room temp.
Saturated = tightly packed, solid at room temp.
Diffusionrandom spreading of molecules from regions of high concentration to low
concentration
o Exergonic process
o Fick's First Law of Diffusion: (do not need to memorize formula or what letters stand
for. Know how to use)
D=coefficient
A=surface area
(C2-C1) = concentration gradient
Concentration will affect net movement (low concentration = more net
movement)
The size of the molecules do not matter
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Osmolarity = measure of total solute concentration
Water relations inside cell
o Hypertonic: net movement of water OUTSIDE cell (wrinkled blood cell)
o Isotonic: no net movement of water (stable)
o Hypotonic: water goes in bc there is more solute INSIDE cell (blood cell bursts)
Facilitated Diffusion: molecules move DOWN concentration gradient
o Channels form passage-way for ions to cross plasma membrane (big molecules)
o Carriers bind to molecules & carry them across
How does glucose get into bloodstream?
o Glucose is mainly absorbed by small intestine
o Glucose carriers move glucose from inside intestine cells toward blood vessels
o Active transport: molecules move AGAINST concentration gradient
Must be coupled to an exergonic process
Goes from low to high concentration (needs energy)
o Secondary Active TransportNa+ & Glucose Co-transporter
o Primary Active TransportNa+/K+ pump
Takes Na coupled with ATP and replaces it with K
K+ should be higher in the cell (pumping K+ IN)
o Glucose absorption during digestion
Enters an intestinal cell along with Na+ driven by Na+ concentration
Na+ concentration is low inside cell
Glu
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