CH 5 Cell
aquaporin
A channel protein in the plasma membrane of a plant, animal, or microorganism cell that specifically facilitates osmosis, the diffusion of free water across the membrane.
hydrophobic interactions
A membrane is held together primarily by _____________
Unsaturated
A membrane with _________ hydrocarbon tails would be more fluid and flexible
Plasmolysis
A phenomenon in walled cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall; occurs when the cell loses water to a hypertonic environment.
Plasma membrane
A prokaryotic cell has which of the following?
peripheral protein
A protein loosely bound to the surface of a membrane or to part of an integral protein and not embedded in the lipid bilayer.
Glycoproteins
A protein with one or more covalently attached carbohydrates.
concentration gradient
A region along which the density of a chemical substance increases or decreases.
View 2 because the rate of water movement into the RBCs equals the rate of water movement out of the cells
A sample of human blood was placed in a test tube containing a physiological saline solution (0.9% sodium chloride). This type of solution is often used intravenously to quickly rehydrate patients. A drop of the blood from the test tube was placed on a slide and red blood cells (RBCs) were observed under a microscope. Three possible outcomes are diagrammed below. Which of the following best predicts which diagrammed microscope view the laboratory worker would see and best explains why?
The bacterial cell, because it has the largest surface-to-volume ratio.
A spherical bacterial cell has a radius of 3μm. The human egg cell has a radius of 100μm. Which statement correctly indicates the cell that is able to more efficiently exchange materials with the external environment and provides a correct explanation?
ion channels
A transmembrane protein channel that allows a specific ion to diffuse across the membrane down its concentration or electrochemical gradient.
transport protien
A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.
integral protein
A transmembrane protein with hydrophobic regions that extend into and often completely span the hydrophobic interior of the membrane and with hydrophilic regions in contact with the aqueous solution on one or both sides of the membrane (or lining the channel in the case of a channel protein).
polar
Adhesion is the attracted of water molecules to molecules other than water. to do this the molecule it is attracted to must be _________
nuclear envelope
All of the following cell components are found in prokaryotic cells EXCEPT (DNA, ribosomes, cell membrane, nuclear envelope, enzymes)
proton pump
An active transport protein in a cell membrane that uses ATP to transport hydrogen ions out of a cell against their concentration gradient, generating a membrane potential in the process.
electrogenic pump
An active transport protein that generates voltage across a membrane while pumping ions.
Exocytosis. When a transport vesicle fuses with the plasma membrane, the vesicle membrane becomes part of the plasma membrane.
As a cell grows, its plasma membrane expands. Does this involve endocytosis or exocytosis? Explain.
Endocytosis
Cellular uptake of biological molecules and particulate matter via formation of new vesicles from the plasma membrane.
int- penetrate hydrophobic interior of the lipid bilayer per- are not embedded in the lipid bilayer at all
Contrast integral and peripheral proteins of a cell membrane
Osmosis
Diffusion of water through a selectively permeable membrane
Each ion is being transported against its electrochemical gradient. If either ion were transported down its electrochemical gradient, this process would be considered cotransport.
Explain why the sodium-potassium pump in Figure 5.14 would not be considered a cotransporter.
Add more of the proteins to the plasma membrane and measure the rate of the particle movement.
Figure 1 shows a model of how a channel protein influences the movement of a particle across a cell's plasma membrane.An investigator wants to understand whether a newly found membrane protein is involved in membrane transport of a certain particle. Which investigation will help determine whether the new membrane protein is a channel protein involved in membrane transport?
Amphipathic
Having both a hydrophilic region and a hydrophobic region
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. (This is the opposite of the case for O2, described in this section of the text.)
How do you think a cell performing cellular respiration rids itself of the resulting CO2?
The grasses living in the cooler region would be expected to have more unsaturated fatty acids in their membranes because those fatty acids remain fluid at lower temperatures. The grasses living immediately adjacent to the hot springs would be expected to have more saturated fatty acids, which would allow the fatty acids to "stack" more closely, making the membranes less fluid and therefore helping them to stay intact at higher temperatures. (Cholesterol could not moderate the effects of temperature on membrane fluidity in this case because it is not found within plant cell membranes.)
How would the membrane lipid composition of a native grass found in very warm soil around hot springs compare with that of a native grass found in cooler soil? Explain.
Passage of a solute against its concentration gradient
If ATP breakdown (hydrolysis) is inhibited, which of the following types of movement across cell membranes is also inhibited?
The activity of Paramecium caudatum's contractile vacuole will decrease. The vacuole pumps out excess water that accumulates in the cell; this accumulation occurs only in a hypotonic environment.
If a Paramecium caudatum cell swims from a hypotonic to an isotonic environment, will its contractile vacuole become more active or less? Why?
okay
Know how to draw a water molecule
amphipathic
Like membrane lipids, most membrane proteins are ______
flaccid
Limp. Lacking in stiffness or firmness, as in a plant cell in surroundings where there is no tendency for water to enter the cell.
Organelles isolate specific reactions, increasing metabolic efficiency.
Membrane-bound organelles have been an important component in the evolution of complex, multicellular organisms. Which of the following best summarizes an advantage of eukaryotic cells having internal membranes?
An ancestral cell most likely engulfed anaerobic prokaryote in a relationship that proved beneficial for both cells.
Mitochondria are found in most eukaryotic cells and contain their own DNA and ribosomes that are similar to those typical of many prokaryotic cells. Which of the following statements is justified by these observations?
Diffusion
Movement of molecules from an area of higher concentration to an area of lower concentration.
both plant cells and fungal cells, the cell wall surrounds the outside of the cell membrane.
Plant cell walls are composed of cellulose, while fungal cell walls are composed of chitin. A group of scientists hypothesize that this difference means the cell wall has largely different functions in plant cells and fungal cells. Alternatively, another group of scientists hypothesize that despite their biochemical differences, plant and fungal cell walls serve similar functions. Which of the following observations would best support the alternative hypothesis described above?
They are on the inner side of the transport vesicle membrane.
Plasma membrane proteins have carbohydrates attached to them in the ER and Golgi apparatus and then are transported in vesicles to the cell surface. On which side of the vesicle membrane are the carbohydrates?
Isotonic
Referring to a solution that, when surrounding a cell, causes no net movement of water into or out of the cell.
Hypertonic
Referring to a solution that, when surrounding a cell, will cause the cell to lose water.
Hypotonic
Referring to a solution that, when surrounding a cell, will cause the cell to take up water.
The internal environment of a lysosome is acidic, so it has a higher concentration of H+ than does the cytoplasm. Therefore, you might expect the membrane of the lysosome to have a proton pump such as that shown in Figure 5.16 to pump H+ into the lysosome.
Review the characteristics of the lysosome discussed in Concept 4.4. Given the internal environment of a lysosome, what transport protein might you expect to see in its membrane?
The pump uses ATP. To establish a voltage, ions have to be pumped against their gradients, which requires energy.
Sodium-potassium pumps help nerve cells establish a voltage across their plasma membranes. Do these pumps use ATP or produce ATP? Explain.
turgid
Swollen or distended, as in plant cells. (A walled cell becomes turgid if it has a lower water potential than its surroundings, resulting in entry of water.)
False
T/f all cell membrane are created equal in terms of fluidity and lipid composition
endoplasmic reticulum (ER) and Golgi apparatus.
The asymmetric arrangement of proteins, lipids, and their associated carbohydrates in the plasma membrane is determined as the membrane is being built by the ___________
Exocytosis
The cellular secretion of biological molecules by the fusion of vesicles containing them with the plasma membrane.
Contransport
The coupling of the "downhill" diffusion of one substance to the "uphill" transport of another against its own concentration gradient.
The organism does not have a nuclear membrane surrounding its genetic material.
The diagram above represents a typical rod-shaped bacterium. Which of the following best describes a feature shown in the diagram that is unique to archaea and bacteria?
electrochemical gradient
The diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane (a chemical force) and the ion's tendency to move relative to the membrane potential (an electrical force).
B
The following questions refer to the following diagram. For each phrase or sentence, select the labeled part to which it is most closely related. Each option may be used once, more than once, or not at all for each group. Evolved from a photoautotrophic prokaryote
D
The following questions refer to the following diagram. For each phrase or sentence, select the labeled part to which it is most closely related. Each option may be used once, more than once, or not at all for each group. Site of transport of materials into and out of the cell
integral proteins
The hydrophobic regions of an _____consist of one or more stretches of nonpolar amino acids usually coiled into α helices
H+ ions will stop moving through the protein.
The illustration shows the active transport of hydrogen ions through a membrane protein.Which of the following best predicts the effect of not having atp available to supply energy to this process?
Na+ transport out of the cell requires ATP hydrolysis.
The manner in which several different ions and molecules move through a cell membrane is shown in the diagram above. For each ion or molecule, the relative concentration on each side of the membrane is indicated. Which of the following accurately describes one of the movements taking place?
active transport
The movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and requiring an expenditure of energy.
facilitated diffusion
The passage of molecules or ions down their electrochemical gradient across a biological membrane with the assistance of specific transmembrane transport proteins, requiring no energy expenditure.
Single-celled organisms will use various mechanisms to counteract the increased flow of water from cells to the environment.
The salinity of a small inland lake has recently started to increase. Researchers are planning to study the lake over several decades to investigate how freshwater organisms survive significant changes in their natural habitat. Which of the following physiological mechanisms will the researchers most likely observe among the surviving organisms in the lake?
To have the ability to determine or allow substances in and not others
What does it mean to be selectively permeable
O2 and CO2 are both nonpolar molecules that can easily pass through the hydrophobic interior of a membrane.
What property allows O2 and CO2 to cross a lipid bilayer without the help of membrane proteins?
facilitated diffusion
When a substance moves across the plasma membrane along a concentration gradient at a rate faster than would be expected by simple diffusion alone but without the expenditure of metabolic energy, the process is best described as
Eukaryotes have organelles that allow for compartmentalization of cellular processes, which increases the efficiency of those processes.
Which of the following best describes an advantage that eukaryote organisms have over prokaryote organisms?
Mitochondria and bacteria possess similar ribosomes and DNA.
Which of the following best supports the statement that mitochondria are descendants of endosymbiotic bacteria-like cells?
it has a cell wall exterior to the plasma membrane and contains ribosomes.
Which of the following is true about the structure of the prokaryotic cell represented in the figure?
Some organelles contain their own DNA that is more similar to prokaryotic DNA in structure and function than to the eukaryotic DNA found in the cell's nucleus.
Which of the following statements best supports the claim that certain organelles within eukaryotic cells evolved from free-living prokaryotic cells?
Ions are unable to move through the phospholipid bilayer because the nonpolar tail regions of the phospholipids are hydrophobic.
Which of the following statements is true regarding the movement of substances across cell membranes?
Water molecules will still be able to move across the cell membrane but at a slower rate.
Which statement best describes the effect on water transport across the cell membrane if the aquaporin in the figure ceases to function?
Interactions of the hydrophobic and hydrophilic amino acids help to anchor the protein in the membrane.
Which statement best explains why correct protein folding is critical in the transmembrane protein shown above?
Water is a polar molecule, so it cannot pass very rapidly through the hydrophobic region in the middle of a phospholipid bilayer.
Why is a transport protein needed to move many water molecules rapidly across a membrane?
Polar
______ molecules such as glucose and other sugars pass only slowly through a lipid bilayer
transport proteins
________ is specific for the substance it translocates allowing only a certain substance to cross the membrane.
Channel proteins
_________ function by having a hydrophilic channel that certain molecules or atomic ions use as a tunnel through the membrane
membrane potential
__________ affects the activity excitable cells and the transmembrane movement of all charged substances
Glycolipids
a lipid with one or more covalently attached carbohydrates
selectively permeability
a property of biological membranes that allows them to regulate the passage of substances across them
gated channel
a transmembrane protein channel that opens or closes in response to a particular stimulus
soduim-potassium pump
a transport protein in the plasma membrane of animal cells that actively transports sodium out of the cell and potassium into the cell
spontaneous
diffusion is a _____ process
Active transport
enables a cell to maintain internal concentrations of small solutes that differ from concentrations in its environment.
gated channels
for some ______ the stimulus is electrical
glycolipids and glycoproteins
list two types of recognition carbohydrates of a cell membrane
okay
membranes are selectively permeable and therefore have different effects on the rates of diffusion of various molecules. In the case of water, aquaporins allow water to diffuse very rapidly across the membranes of certain cells
membrane lipids
natural selection has apparently favored organisms whose mix of _________ ensures an appropriate level of membrane fluidity for their environment.
Osmoregulation
regulation of solute concentrations and water balance by a cell or organism
discriminating barrier of the lipid bilayer and the specific transport proteins built into the membrane
selective permeability of a membrane depends on both the
Tonicity
the ability of a surrounding solution to cause a cell to gain or lose water
other water molecules
the cohesion of water is when water molecules are attracted to _______
fluid mosaic model
the currently accepted model of cell membrane structure, which envisions the membrane as a Mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids
membrane potential
the difference in electrical charge across a cell's plasma membrane due to the differential distribution of ions.
passive transport
the diffusion of a substance across a biological membrane with no expenditure of energy
a chemical force (the ion's concentration gradient) and an electrical force (the effect of the membrane potential on the ion's movement).
two forces drive the diffusion of ions across a membrane:
Small and non polar O2 and CO2
what property of oxygen and carbon dioxide allows them to cross the membrane without help of proteins
it facilitates osmosis the diffusion of free water across the membrane and also allows single file passage of up to 3 billion water molecules
why does water need an aquaporin transport protein