Unit 2 (Week 4 Assignment Questions) Flashcards
What separates the internal contents of a cell from the extracellular environment?
The nucleus
The extracellular matrix
The nuclear envelope
The plasma membrane
The plasma membrane
The three main types of macromolecules that comprise the plasma membrane are
Phospholipds, proteins, carbohydrates
What is the basic structure of the plasma membrane?
Multiple choice question.
A phospholipid bilayer
Arrangement of subunits into a tubule
A double helix
A phospholipid monolayer
Phospholipid bilayer
Which labeled region(s) of the plasma membrane is(are) hydrophilic?
The heads on both sides of the phospholipid bilayer.
Which of the following statements best describes the chemical composition of biological membranes?
Biological membranes are bilayers of proteins with associated lipids and carbohydrates.
Biological membranes are composed of two layers—one layer of phospholipids and one layer of proteins.
Biological membranes are bilayers of phospholipids with associated proteins and carbohydrates.
Biological membranes are composed of equal numbers of phospholipids, proteins, and carbohydrates.
Biological membranes are composed of lipids with proteins attached to the outer surface.
C
Which of the following events can never be energetically favorable in a biological membrane and therefore will not occur spontaneously?
the rotation of phospholipids
the lateral movement of phospholipids
the flip-flop of phospholipids to the opposite leaflet
the rotation of membrane proteins
the lateral movement of membrane proteins
C
Let’s suppose an insect, which doesn’t maintain a constant body temperature, was exposed to a shift in temperature from 60°F to 80°F. Which of the following types of membrane changes would be the most beneficial in helping the insect cope with the temperature shift?
increase the number of double bonds in the lipid tails of phospholipids
increase the length of the lipid tails of phospholipids
decrease the amount of cholesterol in the membrane
decrease the amount of carbohydrate attached to membrane proteins
decrease the amount of carbohydrate attached to phospholipids
B
Carbohydrates of the plasma membrane
are bonded to a protein or lipid.
are located on the outer surface of the plasma membrane.
can function as cell markers for recognition by other cells.
All of the above are true of the carbohydrates.
Only a and c are true.
D
A transmembrane protein in the plasma membrane is glycosylated at two sites in the polypeptide sequence. Where in this protein would you expect these two sites to be?
in transmembrane segments
in hydrophilic regions that project into the extracellular environment
in hydrophilic regions that project into the cytosol
could be anywhere
b and c only
B
The tendency for Na+ to move into the cell can be due to
the higher numbers of Na+ outside the cell, resulting in a chemical concentration gradient.
the net negative charge inside the cell attracting the positively charged Na+.
the attractive force of K+ inside the cell pulling Na+ into the cell.
all of the above.
a and b only.
E
Let’s suppose the solute concentration inside the cells of a plant is 0.3 M and the concentration outside is 0.2 M. If we assume that the solute does not readily cross the membrane, which of the following statements best describes what will happen?
The plant cells will lose water, and the plasma membrane will push against the cell wall.
The plant cells will lose water, and the plasma membrane will pull away from the cell wall (plasmolysis).
The plant cells will take up a lot of water and undergo osmotic lysis.
The plant cells will take up a little water, and the plasma membrane will push against the cell wall.
both a and b.
D
What features of a biological membrane are major contributors to its selective permeability?
phospholipid bilayer
transport proteins
glycolipids on the outer surface of the membrane
peripheral membrane proteins
both a and b
E
What is the name given to the process in which solutes are moved across a membrane against their concentration gradient?
simple diffusion
facilitated diffusion
osmosis
passive diffusion
active transport
E
Large particles or large volumes of fluid can be brought into the cell by
facilitated diffusion.
active transport.
endocytosis.
exocytosis.
all of the above.
C
Why do shorter tails make membranes more fluid?
Multiple choice question.
Shorter tails have more nonpolar character.
Shorter tails attract each other more strongly.
Shorter tails create clumps of lipids.
Shorter tails interact less with each other.
D
The Frye and Edidin experiment demonstrated that lateral protein movement within the membrane is affected by
temperature, heat, high temperature, or temp
The smooth endoplasmic reticulum is where most eukaryotic membrane _____________ are synthesized.
Phospholipids
What property of biological membranes describes the ability of individual molecules to move within the membrane?
Mosaic composition
Fluidity
Permeability
Rigidity
B
When they are synthesized, transmembrane proteins are first inserted into the _____________ membrane before being transferred via vesicles to other regions of the cell.
Endoplasmic reticulum
Why is it more appropriate to describe membranes as semifluid rather than fluid?
Molecules move laterally within the membrane leaflet.
Phospholipids usually move in two dimensions.
T/F Lipids with shorter tails contribute to decrease plasma membrane fluidity.
False. It increases.
A key similarity between simple and facilitated diffusion is that both require ______.
Concentration gradients.
Identify functions of the selectively permeable plasma membrane.
Remove waste products from within the cell
Maintain a proper balance of ions within the cell
Maintain a proper supply of essential molecules such as glucose and amino acids
The Frye and Edidin experiment demonstrated that lateral protein movement within the membrane is affected by
Temperature
To move a substance through a membrane against a concentration gradient, which of the following are necessary?
a source of energy
a transport protein
a membrane vesicle
a vacuole
A and B
What happens during osmosis?
Multiple choice question.
Water moves from areas of high solute concentration to areas of low solute concentration
Water moves from areas of low solute concentration to areas of high solute concentration
Water moves from areas of low solute concentration to areas of high solute concentration
When a plant cell is placed into a hypertonic extracellular solution, water leaves the cell, and the plasma membrane pulls away from the cell wall in a process called
Plasmolysis
Proteins that assist in the movement of substances across membranes can be classified into two types based on how they move solutes across a membrane:
Transporters and channels
Channel proteins are transmembrane proteins that are used for what?
Multiple choice question.
Antiporters
Active transport
Symporters
Facilitated Diffusion
D
Transporter proteins transport solutes across the membrane via ______.
Multiple choice question.
aquaporins that allow the passage of substances dissolved in water
channels that are always open
an open passageway that allows facilitated diffusion
a conformational change triggered by solute binding
D
Which of the following move solutes in only one direction?
Symporters
Antiporters
Uniporters
Symporters
Uniporters
Which of the following best describes the process of active transport?
Particles moving across a membrane without energy expenditure.
Particles moving freely down a concentration gradient.
Particles moving across a membrane against a concentration gradient.
Particles moving freely down a concentration gradient, facilitated by a transmembrane protein.
Particles moving across a membrane against a concentration gradient.
What is the result of placing a plant cell into a hypertonic solution?
Osmotic lysis
Crenation
Phagocytosis
Plasmolysis
Plasmolysis
What are the categories of proteins that assist in the movement of molecules and ions across membranes?
Multiple select question.
Channels
Scaffolds
Coenzymes
Ligands
Transporters
Channels and transporters
What two processes are coupled across animal cell membranes?
Multiple select question.
The import of K+ ions
The import of Na+ ions
The export of Na+ ions
The export of K+ ions
The import of K+ ions
The export of Na+ ions
What type of proteins form an open passageway for facilitated diffusion of ions or molecules across the membrane?
Multiple choice question.
Pumps
Transporters
Symporters
Channels
Channels
The primary difference between endocytosis and exocytosis is ______.
Multiple choice question.
the type of cargo available to transport
one occurs in eukaryotes the other occurs in prokaryotes
the direction of transport
one deals with cell “drinking,” the other with cell “eating”
C
