chapter 5 launchpad

a beaker is divided by a membrane that is permeable to water and glucose, but not to sucrose. equal volumes of solutions are added to side a and b with the initial concentration as shown below. initially, the liquid levels on both sides are the same Side A : 1.0 M sucrose, 0.5 M glucose Side B : 0.5 M sucrose, 1.0 M glucose after the system described above reaches equilibrium, what will be the concentration of glucose on side B

0.75 M

which of the substances would be an example of a peripheral membrane protein associated with the plasma membrane of a cell? -the epidermal growth factor receptor, which binds to signals outside the cell and phosphorylates proteins in the inside of the cell -Grb2, a protein that binds to the intracellular domain of the epidermal growth factor receptor when it is activated -MEK, an enzyme that activates other proteins in the cytoplasm -Myc, a transcription factor that binds to DNA and activates transcription of specific genes

Grb2, a protein that binds to the intracellular domain of the epidermal growth factor receptor when it is activated

the image illustrates our understanding of how typical cell membranes are structured. which arrow is pointing at a cholesterol?

Line D ; the thicker lines inside the hydrophobic tails

the small red dots in the simulation could represent which of the answer choices? Na+, O2, Cl-, glucose

O2

which part of cholesterol molecule is polar?

OH group

in the image, an active transport protein pump drives protons out of the cell using energy from ATP. under some circumstances pumps like this can be run in reverse. if this pump could be reversed, what would be the result in the cytoplasm?

a decrease in pH and an increase in ATP

in the example illustrated here, a substance is moved _____ its concentration gradient using the energy of ____

against ; electrochemical gradient

the defining characteristics of active transport are that this category of transport moves substances ______ their concentration gradient and requires ______

against ; energy

why does active transport of molecules across a membrane require ATP?

an input of energy is needed to allow the movement of molecules from an area of low concentration to one of higher concentration

how do eukaryotic plant and animal cells differ from one another?

animal cells do not have chloroplasts and cell walls, and plant cells do

which of the answer choices would be the best analogy for an electrochemical gradients across a cellular membrane? -waterfall -electric generator -light bulb -battery -water pump

battery

a phospholipid molecule in a membrane can :

both spin (rotate around its vertical axis) and move side-to-side (lateral movement).

carriers can move certain molecules across a membrane. which of the answer choices is not a property of carriers? -carriers can transfer any molecules as long as it is not larger than the diameter of the carrier -carriers have regions with my hydrophobic amino acids -some carriers bind a single molecule and others can bind multiple molecules simultaneously -carriers have high specifically for a single molecule

carriers can transfer any molecules as long as it is not larger than the diameter of the carrier

Prokaryotes absorb their nutrients from the environment. however, prokaryotes also have cell walls. What can you conclude from these statements?

cell walls are permeable, allowing nutrients to pass through

Some lipid rafts are characterized by an accumulation of cholesterol. What does this mean for the fluidity of the raft domain?

cholesterol decreases the fluidity of the membrane at normal temperatures

An amphipathic molecule is one that:

contains both polar and nonpolar regions

a bacterial cell, a plant cell and an animal cell have which of the following structures in common? -cytoplasm -cell wall -vacuole -nucleus -nucleoid

cytoplasm

imagine a cell that has a membrane composed mostly of lipids with saturated fatty acid tails, and that this membrane also has low cholesterol content. what are the characteristics of this cell membrane?

due to its low cholesterol content, the cell membrane would lose its fluidity at cold temperatures

the controlled release of cellular material stored in membrane bound vesicles to the outside of the cell is an example of :

exocytosis

release green molecules outside the cell with channels but without carriers. watch them over time. by what process are they crossing the plasma membrane? select all that apply -facilitated diffusion -active transport -passive transport -simple diffusion

facilitated diffusion and passive transport

true or false : if a molecule can freely cross the membrane, then at equilibrium there will be no further movement of molecules across the membrane?

false

true or false : molecules that can move freely across the membrane can also move across the membrane by going through channels

false

true or false : simple diffusion of a molecule down its concentration gradient requires an input of energy to the system

false

The interior region of a phospholipid bilayer is characterized as:

hydrophobic

molecules that are _____ and _____ are able to move across the cell membrane via simple diffusion

hydrophobic ; small

consider a protein that is targeted to be excreted to the outside of the plasma membrane. where would this protein be located in the endoplasmic reticulum?

in the lumen (inside) of the E.R

consider a protein that is targeted to be excreted to the outside of the plasma membrane. where would this protein be located in the Golgi?

in the lumen (inside) of the golgi

which type of molecules depicted in the figure is amphipathic?

integral membrane proteins, cholesterol and phospholipids

as molecules move down their concentration gradient, from a more ordered state to a less ordered state, entropy :

is increasing

why is the transporter in the figure considered to be an example of "secondary transport"?

it is driven by the proton gradient that was created by energy from ATP

why is the energy from a molecule of ATP required by the sodium potassium pump?

it provides the energy required to move sodium and potassium ions against their concentration gradients

consider a protein that is targeted to be an integral membrane protein on the surface of a cell. it has a specific functional domain (domain x) facing the external environment of the cell. how will this protein be oriented in the E.R?

it will be embedded in the E.R membrane with domain x facing the lumen of the E.R

consider a protein that is targeted to be an integral membrane protein on the surface of a cell. it has a specific functional domain (domain y) facing the cytoplasm of the cell. how will this protein be oriented in the golgi?

it will be embedded in the golgi membrane with domain y facing the cytoplasm of the cell

many cell functions involve communication between cells via molecular signals that must be sent from one cell to be received by a target cell. suppose the signal to be sent is a small protein. where would you expect to find the protein in the golgi?

it would be in the lumen of the golgi

the image illustrates our understanding of how typical cell membranes are structured. which line is pointing to a protein?

line a ; the big masses on top of the hydrophilic heads

the image illustrates our understanding of how typical cell membranes are structured. which arrow is pointing at the hydrophilic head group of a phospholipid?

line b

how can lysosomal enzymes that work best at a pH of 5 be fully functional if the pH pf the cytoplasm is 7?

lysosomal enzymes are separated from the cytoplasm by the membrane surrounding the lysosome

a cell has a mutation that prevents it from breaking down unwanted proteins present in vesicles. which cellular structure is most likely to be disrupted by this mutation?

lysosomes

which of the answer choices is not considered to be a part of the endomembrane system? -plasma membrane -endoplasmic reticulum -lysosome -mitochondria -golgi

mitochondria

which component is part of the endomembrane system of a eukaryotic cell? -chromosomes -ribosomes -nuclear envelope, golgi apparatus, and the endoplasmic reticulum all make up the endomembrane system -plasma membrane

nuclear envelope, golgi apparatus, and the endoplasmic reticulum all make up the endomembrane system

researchers seldom find prokaryotic cells that are greater than 100 micrometers in diameter. why would the size of the prokaryote cells be restricted?

prokaryotic cells must absorb all of their nutrients from their environment and therefore require a high surface area to volume ratio

the process of diffusion requires :

random movement of molecules

to move a specific molecule across a membrane, carrier proteins :

require that the molecule specific to the carrier bind and cause a change in conformation

release green molecules outside the cell with carriers but without channels. watch them over time. by what process are they crossing the plasma membrane? select all that apply -facilitated diffusion -passive transport -simple diffusion -active transport

simple diffusion or active transport

a container is divided into two compartments by a membrane that is fully permeable to water and small ions. water is added to one side of the membrane (side a) and a 5% solution of sodium chloride (NaCl) is added to the other side (side b). if allowed to reach equilibrium, which of the answer choices would you predict? -the level of solution on side b will be higher than side a -the level of solution on side a will be higher than side b -the NaCl concentration on side a and side b will each be 5% -the NaCl concentration on side a and side b will each be 2.5%

the NaCl concentration on side a and side b will each be 2.5%

imagine that you have two blades of grass. one is from a normal plant, and the other is from a mutant plant that cannot absorb water into its vacuoles. how will the structure of these two blades of grass compare?

the grass blade from the mutant plant will appear limp compared to that from the normal plant

Although the phospholipid molecules can be constant lateral movement, they very rarely flip from one side of the bilayer to the other. Which of the following could explain this?

the head groups are repelled by the hydrophobic membrane interior

in the experiment that showed membrane fluidity, what was the purpose of shining a laser on the membrane?

the laser light destroys the dye fluorescence

release green molecules outside the cell with channels but without carriers. what happens over time?

the molecules are found both inside and outside of the cell

release red molecules inside the cell without any channels or carriers. what happens over time?

the molecules are found both inside and outside of the cell

release purple molecules inside the cell with channels but without carriers. what happens over time?

the molecules are only found inside the cell

release purple molecules inside the cell without any channels or carriers. what happens over time?

the molecules are only found inside the cell

release green molecules outside the cell without any channels or carrier. what happens over time?

the molecules are only found outside the cell

release red molecules inside the cell without any channels or carriers. click on the graph button at the bottom left. observe what happens over time. when there are equal numbers of molecules on the two sides of the membrane, what happens next?

the molecules continue crossing the membrane

in the example of secondary active transport, what would happen if ATP suddenly became unavailable for step 1 in panel a of the figure shown?

the movement of the molecules through the antiporter would continue for a while until the proton gradient was depleted

based on the two step model of glucose transport, what would happen if the rate of function of the sodium potassium pump increased?

the sodium potassium pump would make a stronger sodium gradient, so more glucose could be transported across the membrane

in the kidney, glucose transport across the cell membrane is the result of a combination of two steps of active transport. refer to the figures shown. the first step involves a primary active transport system preformed by the sodium potassium pump. it uses the energy from ATP hydrolysis to move sodium ions out of the cell and potassium ions into the cell. the second step involves a secondary active transport symporter that uses the energy in the sodium that uses the energy in the sodium gradient created by the first step. this second step moves glucose, as well as sodium ions that move down their concentration gradient, into the cell. based on the two step model of glucose transport, what would happen if the supply of ATP was depleted from the cell?

the sodium potassium pump would make less of a sodium gradient, so less glucose could be transported across the membrane

diffusion is best described as the random movement of molecules influenced by :

the thermal energy of the environment and energy transferred from molecular collisions in the cell

a container divided into two compartments by a membrane that is fully permeable to water but not to larger molecules. water is added to one side of the membrane (side a) and an equal volume of a 5% of glucose is added to the other side (side b). what would you predict to happen?

the water level on side b will increase and on side a will decrease

a beaker is divided by a membrane that is permeable to water and glucose, but not to sucrose. equal volumes of solutions are added to side a and side b with the initial concentration as shown below. initially, the liquid levels on both sides are the same Side A : 1.0 M sucrose, 0.5 M glucose Side B :0.5 M sucrose, 1.0 M glucose after the system described above reaches equilibrium, what can you predict about the water levels?

the water will be higher on side a than on side b

release red molecules inside the cell without any channels or carriers. observe what happens over time. what can you infer about these molecules?

they are hydrophobic

which of the following would be synthesized on the rough endoplasmic reticulum? -transmembrane protein receptors -nuclear proteins -cytoskeleton proteins -mRNAs

transmembrane protein receptors

true or false : at equilibrium, there will be no net movement of molecules across the cell membrane

true

most elements of the endomembrane system are connected by:

vesicular trafficking