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transport across membranes
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Cards (33)
What is the fluid mosaic model of membranes?
A model describing
membrane structure
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What does the term "fluid" refer to in the fluid mosaic model?
Phospholipid
bilayer
allows
movement
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What does the term "mosaic" refer to in the fluid mosaic model?
Proteins
of
different
sizes and shapes
embedded
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What is the role of cholesterol in membranes?
Reduces
fluidity
and
stabilizes
bilayer
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What is the role of glycolipids in membranes?
Cell signaling
and
recognition
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What are the functions of extrinsic proteins in membranes?
Binding
sites
/
receptors
,
antigens
(glycoprotein),
binds
cells together and cell
signaling
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What are the functions of intrinsic proteins in membranes?
Electron
carriers
(respiration / photosynthesis),
carrier
proteins
(facilitated diffusion) and
channel
proteins
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What is one function of membranes within cells?
Provide
internal transport system
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How do membranes regulate the passage of molecules?
They are
selectively
permeable
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What is one function of the cell-surface membrane?
Isolates
cytoplasm
from
extracellular
environment
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What are three factors that affect membrane permeability?
Temperature - denatures membrane proteins
pH
- changes tertiary structure of membrane proteins
solvents
- may dissolve membrane
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How does temperature affect membrane permeability?
High temperature denatures
membrane proteins
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How does pH affect membrane permeability?
Changes
tertiary structure
of membrane proteins
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How can solvents affect membrane permeability?
Solvents
may
dissolve
the
membrane
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How can colorimetry be used to investigate membrane permeability?
Use plant tissue with soluble pigment.
Disrupt tonoplast and cell-surface membrane.
Select colorimeter filter with complementary color.
Measure absorbance or % transmission value.
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What is osmosis?
Water diffusion across semipermeable membranes from an area of high water potential to an area of low water potential
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What is water potential (ψ)?
Pressure
created by
water
molecules
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What is the water potential of pure water at 25℃ and 100 kPa?
0
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How does osmosis affect plant cells?
Protoplast
swells
, making cell
turgid
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How does osmosis affect animal cells?
Causes
lysis
when water enters
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What is simple diffusion?
Passive
movement of molecules (no atp)
down
a
concentration
gradient
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What is facilitated diffusion?
Passive transport of
charged
ions
or
polar
molecules
using
specific
proteins
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How do channel proteins work?
hydrophilic
channels
bind
to
specific
ions and open/close channels
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How do carrier proteins work?
binds to
complimentary
molecule through
conformational
changes, transports molecules across
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What are five factors that affect the rate of diffusion?
Temperature
,
distance
, surface area,
size
of molecule ,
concentration
difference
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What is Fick’s law?
Surface
area
x
concentration
difference
/
diffusion
distance
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How are cells adapted to maximize transport rates?
Many proteins and
folded
membrane
to
increase
surface
area
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How does the graph of concentration vs. rate differ for simple vs. facilitated diffusion?
Simple diffusion is
linear
; facilitated
levels
off
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What is the process of active transport?
ATP hydrolysis releases phosphate group that binds to carrier protein causing it to change shape. This carrier protein transports molecules and ions against the concentration gradient.
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How do active transport and facilitated diffusion compare?
Active transport requires
energy
from
atp
; facilitated is
passive
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What is co-transport?
Coupled movement of
substances
across
membranes
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How does co-transport aid in glucose absorption?
Na+ gradient drives glucose into cells
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What are the steps of glucose absorption via co-transport?
Na+ actively transported out of epithelial cells into blood stream.
Lower Na+ concentration in epithelial cells than gut lumen.
Glucose/ amino acids from lumen to epithelial cells is 'coupled' to facilitated diffusion of Na+ down eletrochemical gradient
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