BS161 Chapter 5 Learnsmart Questions
The diffusion of these molcules across a selectively permeable membrane is called ______.
osmosis
What makes up the bilayer of every cell membrane?
phospholipids
During receptor-mediated endocytosis, the portion of the receptor molecule that lies inside the plasma membrane is trapped in an indented ____ that is coated on the cytoplasmic side with a protein called _____
pit, clathrin
During endocytosis, the _______ ______ surrounds and envelopes smaller cells, solid particles, or liquids
plasma membrane
A major component of cell membranes that are found floating in the lipid bilayer are called _______.
Proteins
Phagocytosis, Pinocytosis, Endocytosis, an Receptor-mediated endocytosis are all forms of what?
bulk transport
Because individual lipids and unanchored proteins are relatively free to move around laterally within the membrane, the membrane is said to be ______.
fluid
Water is attracted to charged or polar solutes, forming _______ ______ around them
hydration shells
If 2 solutions have unequal concentrations of solutes, the solution with the higher solute concentration is called _______ and the solution with the lower solute concentration is called ______
hypertonic, hypotonic
The combined concentration of all ______ in a solution determines the osmotic concentration of the solution
solutes
Carrier proteins that transport 2 different types of molecules or ion in the same direction are called _____, while those that transport 2 different types of molecules or ions in opposite directions are called _______.
symporters, antiporters
Carrier proteins that transport 2 different types of molecules or ions in the same direction are called ______, while those that transport 2 different types of molecules or ion in opposite directions are called ________
symporters, antiporters
All phospholipids are composed of which of the following?
- A polar "head" and 2 nonpolar "tails" - A backbone derived from glycerol - One phosphate group
Triglycerides and phospholipids are different because only phospholipids have
- A polar "head" and 2 nonpolar "tails" - A phosphate group attached to 1 carbon atom in the backbone
What substances move across the plasma membrane of red blood cells by *simple* diffusion?
- Carbon dioxide - Oxygen
During familial hypercholesterolemia what occurs?
- Cholesterol accumulates as plaques inside the arteries - Cholesterol levels in the blood rise above normal - The risk of a heart attack increases
During endocytosis, what happens regarding food particles?
- Food particles and fluids can enter the cell without actually crossing the plasma membrane - Food particles and fluids are taken in the cell in vesicles and ingested
During coupled transport....
- energy released as one substance moves down its concentration gradient is used to move another substance up its concentration gradient - energy from ATP is used to create a concentration gradient
Sodium-potassium pump cycle:
1.) 3 Na+ bind to the cytoplasmic side of the carrier 2.) The carrier is phosphorylated by ATP 3.) The carrier changes shape and releases 3 Na+ into the extracellular fluid 4.) Two K+ bind to the extracellular side of the carrier 5.) The carrier is dephosphorylated 6.) The carrier changes shape and releases 2 K+ into the cytoplasm
Place (ions, polar molecules, nonpolar molecules) in order according to their capability to cross the lipid bilayer of the plasma membrane without the help of transport proteins. Start with molecules that cross most easily.
1.) Nonpolar molecules 2.) Polar molecules 3.) Ions
During the coupled transport of glucose, the glucose transporter is considered what?
A symporter
The sodium potassium pump can transport as many as _____ Na+ ions per second.
300
Triglycerides and phospholipids are similar because they both have which of the following?
A backbone derived from glycerol
During the coupled transport of glucose, what is the immediate source of energy needed to move glucose into the cell against its concentration gradient?
A gradient of sodium ions
During coupled transport, carrier proteins create a concentration gradient using energy from ___. When the ions or molecules diffuse back down their concentration gradient, energy is released and used to move another substance ___ its own concentration gradient.
ATP, up
Of the two types of transport proteins, carrier proteins and channels, which ones are used for active transport and which ones for facilitated diffusion?
Active transport: carrier proteins only Facilitated diffusion: carrier proteins and channel proteins
What type of cell is likely to burst when placed in a hypotonic solution?
Animal cell
Movement of water across the plasma membrane is facilitate by which of the following?
Channel proteins
True or False. Different cell types have very similar rates of endocytosis.
FALSE. Rates of endocytosis vary from one cell type to another and some have rates that are surprisingly high
What is the immediate source of the energy needed to power the sodium-potassium pump?
Hydrolysis of ATP
What accurately describes the hydrostatic pressure inside a cell if it is transferred from a hypertonic environment to a hypotonic environment? (increase, decrease or stay the same?)
It will increase
What best describes the amount of energy used by *animal* cells in the active transport of Na+ and K+ from areas of low concentration to areas of high concentration?
More than 1/3 of all the energy expended by an animal cell that is not actively dividing is used in the transport of Na+ and K+
Why is active transport such an important cell process?
Only active transport can move a substance from an area where it has a lower concentration to an area where it has a higher concentration
How do phagocytosis and pinocytosis differ?
Only pinocytosis involves intake of liquids
Which of the following (Na+, Glucose, Water, Oxygen gas, or sucrose) can cross the lipid bilayer of a cell membrane most easily without the help of transport proteins?
Oxygen gas
_______ use contractile vacuoles to actively pump water out of the cells to maintain osmotic balance
Paramecium
What types of diffusion require the cell to expend some of its own energy, usually from ATP?
Pinocytosis, Phagocytosis, Exocytosis, Receptor-mediated endocytosis
Which type of transport proteins use energy from ATP directly?
Protein pumps
Which of the following are typical components of biological membranes? (RNA, Proteins, DNA, Lipids)
Proteins Lipids
Low-density lipoprotein (LDL) enters the cell by what process?
Receptor-mediated endocytosis
Name the type of endocytosis, during which molecules bind to specific proteins embedded in the plasma membrane before they are engulfed by the cell. The molecules that are transported into the cell have a conformation that fits snugly with the protein, to which they attach before they are engulfed.
Receptor-mediated endocytosis
In human patients with familial hypercholesterolemia, what happens regarding the LDL receptors?
The LDL receptors lack tails so they are not fastened in the clatherin-coated pits and do not trigger vesicle formation
When is ATP used directly in active transport?
The active transport of Na+ and K+ across the plasma membrane
If a phospholipid that has only phosphate as its polar head is chemically modified by attaching a sugar to the phosphate, how will the behavior of this phospholipid change if placed in water?
The modified lipid will spontaneously form bilayers, just as before the chemical modification
When phospholipids are placed in water, they spontaneously form a bilayer with what?
The polar heads on the surface and the nonpolar tails in the interior
How does facilitated diffusion by carrier proteins differ from simple diffusion?
The rate of transport by simple diffusion increases as the concentration gradient increases
Transport that occurs without a cell expending any of its own energy is called ______ transport.
passive
How do red blood cells promote the movement of glucose into the cell?
They phosphorylate glucose after it enters the cell in order to maintain a steep concentration gradient for unphosphorylated glucose
True or False: The plasma membrane contains areas with distinct lipid and protein composition
True
True or False: The plasma membrane is NOT homogeneous.
True
True or False: The use of energy from ATP during active transport may be direct or indirect
True
True or False: Virtually all eukaryotic cells carry out endocytosis.
True
True or False: Although there are a variety of transporters for glucose, they are all active transporters.
True. some glucose transporters are active, some are passive
Movement of a substance against its own concentration gradient is involved in ______ transport.
active
The ____ transport of sodium and potassium ions from areas of ___ concentration of ____ concentration requires more than one-third of all the energy expended by a non-dividing animal cell
active, low, high
While ____ transport requires the cell to expend some of its own energy, _____ transport does not.
active, passive
Carrier proteins that transport 2 different types of molecules or ions may be either ______ or _______
antiporters, symporters
Water passes by osmosis through the membrane via _______ in response to solute concentration differences and outside the cell.
aquaporins
Of the 2 types of transport proteins that mediate facilitated diffusion, only _____ proteins actually bind with the substance being transported while ______ proteins simply provide a hydrophilic space for the substance to move through.
carrier, channel
The main 2 categories of bulk transport (based on the direction of transport) are _______ and ________
endocytosis, exocytosis
Diffusion that is assisted by a channel protein or carrier protein is called _______ diffusion.
facilitated
Facilitated diffusion and diffusion are involved in ______ transport.
passive
If two solutions have the same concentration of solutes (all solutes), they are ______.
isotonic
when a cell is placed in a ______ solution, water moves across the plasma membrane in both directions but there is no net movement of water.
isotonic
Humans surround the cells with an _______ __________ fluid to maintain osmotic balance
isotonic extracellular
An aqueous solution with a higher concentration of solutes will have a ______ concentration of free water molecules.
lower
Transmembrane domains are composed of ______ amino acids and are typically arranged into ______ helices
nonpolar, alpha
Tails on the interior of the phospholipid bilayer are ______ fatty acids, meaning they are hydro____.
nonpolar, hydrophobic
Globular proteins are inserted in the lipid bilayer with their ______ segments inserted into the lipid bilayer, and their ______ segments protruding from the membrane surface.
nonpolar; polar
The sodium-potassium pump is called an antiporter because it transports Na+ and K+ in ______ directions across the plasma membrane
opposite
The sodium-potassium pump actively pumps ______ ions into the cell and ______ ions out of the cell
potassium; sodium
During facilitated diffusion by carrier proteins, when solute concentrations are low, increasing the solute concentration causes a linear increase in the rate of diffusion. However, at high solute concentration, further increases in the solute concentration no longer increase the rate of diffusion. This means that carrier proteins exhibit ________.
saturation
Cellular membranes are said to be ______ _______ because they allow some substances to pass through easily while other substances pass through very slowly or not at all.
selectively permeable
In countertransport, the cell uses energy released as an ion of ______ moves down its concentration gradient
sodium
Each membrane-spanning region of a transmembrane protein is called a _________ ________.
transmembrane domain
Facilitated diffusion requires the assistance of ______ _____ and is a form of ______ ______.
transport proteins, passive transport
In an aqueous solution, the solvent is _____.
water
Ions and molecules in the cytoplasm of a cell are dissolved in _____.
water
What is required for the sodium potassium pump in cells to work?
- Carrier proteins - ATP
What processes require the cell to expend energy (typically from the hydrolysis of ATP)?
- Coupled transport - Bulk transport
Coupled transport of glucose:
- Energy from ATP is used to pump sodium ions out of the cell against their concentration gradient - As sodium moves back into the cell down its concentration gradient, it releases the energy needed to move glucose up its concentration gradient. - Sodium ions move back into the cell down their concentration gradient.
What 3 substances move across the plasma membrane of red blood cells by facilitated diffusion?
- Glucose - Bicarbonate ions - Chloride ions
In cell membranes, the interior of the lipid bilayer repels what?
- Ions - Hydrophilic molecules - Polar molecules
What 3 things describes the interior of a phospholipid bilayer?
- It is nonpolar -It is hydrophobic -It contains the fatty acid tails
Suppose a dialysis bag containing a 1% starch solution is placed in a beaker containing a 0.1% starch solution. Water is the solvent and water can pass through the dialysis membrane but starch cannot. Which of the following occurs before equilibrium is reached?
- Net movement of water is into the bag - Some water molecules move out of the bag
How do channel and carrier proteins differ?
- Only carrier proteins actually bind to the substance being transported - Carrier proteins can be used for active transport - Carrier proteins can be used for passive transport
Types of endocytosis:
- Pinocytosis - Receptor-mediated endocytosis - Phagocytosis
How does the sodium-potassium pump work?
- Sodium is transported out of the cell - Energy from ATP is used to actively transport sodium up its own concentration gradient - Phosphorylation of the carrier protein causes it to change shape and release sodium ions outside the cell
Suppose a hypertonic solution and a hypotonic solution are separated by a selectively permeable membrane that allows water to pass through freely but prevents the passage of solutes. Before equilibrium is reached, what is true?
- The hypertonic solution has a higher concentration of solutes - Water molecules move across the membrane in both direction - Net movement of water is from the hypotonic solution into the hypertonic solution`
Suppose a dialysis bag containing a 20% sucrose solution is placed in a beaker containing a 2% sucrose solution. Water is the solvent and both water and sucrose can pass through the dialysis membrane. *After equilibrium is reached* which of the following occurs
- There is no net movement of sucrose - There is no net movement of water
What is true regarding ions in the lipid bilayer?
- They are attracted by the hydrophilic interior of channel proteins - They are repelled by the hydrophobic interior of the lipid bilayer - They are attracted to polar molecules - They generally cross the plasma membrane with the help of channel or carrier proteins
How can cells allow large polar molecules to enter the cell?
- They can enter through channel proteins - They can enter through carrier proteins - They can enter by endocytosis
What are the methods of passive transport?
- Transport of water by aquaporins - Osmosis
Functions carried out by membrane proteins?
- Transport specific ions and molecules across the membrane - Receive external chemical messages - Functions as cell-surface identity markers - Catalyze specific chemical reaction on the surface of the membrane
If a cell is placed in a hypotonic solution which of the following occurs?
- Water moves into and out of the cell - Net movement of water is into the cell.
Place (small polar molecules, large polar molecules, and nonpolar molecules) in order according to their capability to cross the lipid bilayer of the plasma membrane without the help of transport proteins. Start with molecules that cross most easily.
1.) Nonpolar molecules 2.) Small polar molecules 3.) Large polar molecules
Cell membranes are assembled by four components:
1.) Phospholipid bilayer 2.) Transmembrane proteins 3.) Interior protein network 4.) Cell-surface markers
When the concentration of a substance varies from one region to another, the net movement of the substance will continue down what until the concentrations the same is all regions?
A concentration gradient
In phospholipids, a phosphate is attached to the third carbon of glycerol. What is typically attached to the phosphate?
A polar or charged organic molecule
Transport that requires a cell to expend some of its own energy, typically from ___, is called ______ transport.
ATP, active
What best describes the relationship between solute concentration and rate of diffusion during facilitated diffusion by carrier proteins?
As solute concentration increases, the rate of diffusion increases but eventually it remains constant once it reaches a maximum rate.
During receptor-mediated endocytosis, what triggers the formation of an endocytic vesicle?
Binding of the target molecules to their matching receptors
Channel proteins (do or do not ) use energy from ATP to facilitate net movement of a substance up its concentration gradient.
Channel proteins DO NOT use energy from ATP to facilitate net movement of a substance up its concentration gradient.
_____ proteins form a hydrophilic pore through the membrane for ions, while ____ proteins bind to the transported molecule.
Channel, carrier
Net movement of a substance from a region where it has a higher concentration to a region where it has a lower concentration is called which of the following?
Diffusion
Phagocytosis is one of the major types of which of the following?
Endocytosis
Which isn't one of the four main components of a cell membrane? ( Phospholipid bilayer, Transmembrane proteins, Extracellular Matrix, Interior protein network, Cell-surface markers)
Extracellular matrix
All membranes have essentially the same composition and degree of fluidity. True or False.
FALSE. The degree of membrane fluidity varies depending on the composition of the membrane.
True or False: The distribution of lipids within the plasma membrane is symmetrical.
FALSE. The distribution of lipids within the plasma membrane is NOT symmetrical.
The surface of the phospholipid bilayer is hydrophobic and the interior of the phospholipid bilayer is hydrophilic. True or False?
FALSE. The surface of the phospholipid bilayer is *hydrophilic* and the interior of the phospholipid bilayer is *hydrophobic*
Some channel proteins use energy from ATP to facilitate net movement of a substance up its concentration gradient. Is this statement true or false regarding channel proteins?
False
True or False: Phosphorylation of the protein which reduces its affinity for Na+ occurs after dephosphorylation of the protein reduces its affinity for K+
False. Phosphorylation of the protein causes conformational changes in the protein, reducing its affinity for Na+ and increasing its affinity for K. Na diffuses out. Binding of K+ causes dephosphorylation of the protein and triggers change back to the original conformation with a low affinity for K. K diffuses out, and the cycle repeats
Which region of a phospholipid molecule is hydrophobic?
Fatty acid hydrocarbon chains
Diffusion is caused by which of the following?
The constant random motion of all atoms and molecules
Large molecules and particle that cannot cross the hydrophobic barrier created by the plasma membrane (either on their own or with the help of a protein) enter or leave the cell by ______ ______
bulk transport
Substances enter or leave the cell packaged inside membranous vacuoles or vesicles that either fuse with or pinch off from the plasma membrane during a process called _______ _______.
bulk transport
The coupled transport of glucose molecules across the cell membrane uses energy released from the concentration gradient of ______.
sodium
Transporting both sodium and potassium ions against their respective gradients, and using energy from ATP to alter the conformation of the carrier protein are features of the _____-______ _____.
sodium-potassium pump
An oak tree does what to maintain osmotic balance?
surround the cells with a rigid cell wall that can withstand the pressure that builds up due to the inflow of water by osmosis
The diffusion of these molecules across a selectively permeable membrane is called osmosis.
water
When 10 grams of sugar are dissolved in 1L of water, _____ is the solvent and _____ is the solute.
water, sugar`
