Chapter 7 Flashcards
What are lipid rafts?
specific lipids in groups of proteins that are in specialized patches within membrane
compare the speed of protein to lipid movement on the membrane
proteins move slowly because they are larger, some are even immobile by attachment to cytoskeleton or ECM
Describe the membrane of a fish that lives at extreme cold temperatures
high portion of unsaturated carbon tails to remain fluid at low temperatures
Describe how peripheral proteins are attached to the lipid bilayer
NOT embedded, loosely bound to surface
Membrane carbohydrates are important because
they function as markers that distinguish one cell from the other
Describe the synthesis of membrane components in the ER
secretory proteins, membrane proteins, lipids synthesized in ER.
Carbohydrates are added to transmembrane proteins to make glycoproteins.
Materials then transported to golgi via vesicles
Describe the synthesis of transmembrane components in the golgi
glyoproteins have more carb modification and lipids become glycolipids
After transmembrane components have left the golgi, they are transported to the plasma membrane via _____
vesicles
What occurs when the vesicles fuse with the plasma membrane after leaving the golgi?
As vesicles fuse with the plasma membrane, the outside face of the vesicle becomes continuous with the inside (cytoplasmic) face of the plasma membrane. This releases the secretory proteins from the cell, a process called exocytosis
positions the carbohydrates of membrane glycoproteins and glycolipids on the outside (extracellular) face of the plasma membrane
A small, non polar molecule has ___ permeability across the membrane
high
What types of molecules would require transport proteins?
some ions and polar molecules
How do channel proteins function?
a hydrophilic channel that certain molecules or ions use as a tunnel through the membrane
What are carrier proteins
hold on to their passengers and change shape in a way
that shuttles them across the membrane
What occurs when a cell with a cell wall is immersed in a hypotonic solution?
it helps maintain the water balance, as the cell wall will expand before it exerts turgor pressure back onto the cell, keeping it firm
What will occur if a plant cell is in an isotonic solution?
there is no net tendency for water to enter and the cells become flaccid
If kidneys didn’t have high numbers of aquaporins, what would happen?
the massive levels of diffusion of water would not be regulated, you’d be peeing all the time
The two proteins primarily responsible for facilitated diffusion are
channel and carrier
Compare ion proteins to carrier proteins
ion proteins: open and close due to an electrical or chemical stimulus
carrier: undergo a subtle change in shape
Speculate about how a cell performing cellular respiration
might rid itself of the resulting CO2
CO2 is a nonpolar molecule that can diffuse through the plasma membrane.
As long as it diffuses away so that the concentration remains low outside the
cell, it will continue to exit the cell in this way.
If a Paramecium swims from a hypotonic to an
isotonic environment, will its contractile vacuole become
more active or less? Why?
Paramecium’s contractile
vacuole will become less active. The vacuole pumps out excess water that accumulates in the cell; this accumulation occurs only in a hypotonic environment.
What is voltage? Describe the charges of the cytoplasmic side of the membrane relative to ECM
voltage: electrical POTENTIAL energy
cytoplasmic side is negative because of unequal districution of anions and cations on both sides
Why does membrane potential favor the passive transport of cations into the cell and anions out of cell?
because inside of cell is negative compared to outside
Two forces drive the diffusion of ions across a membrane. What are they?
a chemical force (ion’s concentration gradient)
And electrical force (membrane potential)
Why is the sodium potassium pump a good example of an electrogenic pump?
Notice that the pump does not translocate Na + and K + one
for one, but pumps three sodium ions out of the cell for every
two potassium ions it pumps into the cell. With each “crank”
of the pump, there is a net transfer of one positive charge
from the cytoplasm to the extracellular fluid, a process that
stores energy as voltage
Na+/K + pumps help nerve cells establish a voltage across their plasma membranes. Do these pumps use ATP or produce ATP? Explain.
These pumps use ATP. To establish a voltage, ions have to be pumped against
their gradients, which requires energy
Explain why the Na+/K + pump would not be considered a cotransporter.
Each ion is being transported against
its electrochemical gradient. If either ion were transported down its electrochem-
ical gradient, this would be considered cotransport.
Bulk transport across the plasma membrane occurs by which two processes?
exocytosis and endocytosis
Describe the process of exocytosis
cell secretes certain molecules by fusion of vesicles with plasma membrane.
The vesicles came from the golgi and moved along a microtubule to reach plasma membrane.
Describe process of endocytosis
the cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane.
- small area of plasma membrane sinks inward to form a pocket
- it pinches in and forms a vesicle containing material from ECM
Phagocytosis involves forming a vesicle around a ____ to be __ in the cell
food or other particle
digested
Pinocytosis involves ___ in a vesicle. The vesicles are often lined with ___
droplets of extracellular fluid
often lined with fuzzy layer of coat protein, the vesicles are called coated pits
As a cell grows, its plasma membrane expands. Does this
involve endocytosis or exocytosis? Explain
Exocytosis. When a transport vesicle fuses with the plasma membrane, the
vesicle membrane becomes part of the plasma membrane
In Concept 6.7, you learned that
animal cells make an extracellular matrix (ECM). Describe
the cellular pathway of synthesis and deposition of an ECM
glycoprotein.
The glycoprotein is synthesized in the ER lumen,
moves through the Golgi apparatus, and then travels in a vesicle to the plasma membrane, where it
undergoes exocytosis and becomes part of the ECM
In what way do the membranes of a eukaryotic cell vary?
(A) Phospholipids are found only in certain membranes.
(B) Certain proteins are unique to each membrane.
(C) Only certain membranes of the cell are selectively permeable.
(D) Only certain membranes are constructed from amphipathic
molecules.
Q1 B
According to the fluid mosaic model of membrane structure,
proteins of the membrane are mostly
(A) spread in a continuous layer over the inner and outer
surfaces of the membrane.
(B) confined to the hydrophobic interior of the membrane.
(C) embedded in a lipid bilayer.
(D) randomly oriented in the membrane, with no fixed inside-
outside polarity.
(C) embedded in a lipid bilayer.
Which of the following processes includes all the others?
(A) osmosis
(B) diffusion of a solute across a membrane
(C) passive transport
(D) transport of an ion down its electrochemical gradient
Q5 B
