Question 1

In focal adhesion, large clusters of integrins bond to which component via various adaptors?
A)tubulins of the cytoskeleton
B)myosin of the cytoskeleton
C)actin of the cytoskeleton
D)dynein of the cytoskeleton
E)band III protein of the membrane

Accepted Answer

Focal adhesions are composed of large clusters of integrins that bind to the actin filaments of the cytoskeleton via various adaptors. The integrins act as transmembrane receptors, connecting the extracellular matrix to the intracellular cytoskeleton, and allowing the cell to sense and respond to mechanical forces. Therefore, integrin-actin interactions are critical for the regulation of cell adhesion, migration, and signaling.

Question 2

What kind of experiments have provided evidence that most integrins have unique functions?
A)enzyme assays
B)gene addition experiments
C)gene knockout experiments in mice
D)freeze-fracture, freeze etch experiments
E)sucrose density centrifugation

Accepted Answer

Gene knockout experiments in mice have provided evidence for the unique functions of integrins. By removing or disabling specific integrin genes, researchers can observe the resulting phenotypic changes in the mouse. This method allows for the direct study of integrin function in vivo, providing strong evidence for the diversity of integrin function.

Question 3

Why do cells flatten out as they make contact with a surface?
A)They lose water.
B)They extrude cytoplasm.
C)They send out projections that make increasingly stable attachments.
D)Their membranes stiffen.
E)They make focal assignations.

Accepted Answer

When cells make contact with a surface, they send out projections such as filopodia and lamellipodia. These projections help the cell to make increasingly stable attachments to the surface. As the cell establishes more stable attachments, it flattens out to maximize the surface area in contact with the substrate. This allows the cell to adhere more firmly and spread out to explore the surrounding environment.

Question 4

Filaments connected to the dense plaque underlying the membrane in a hemidesmosome course outward into the cytoplasm. These filaments are composed of the protein _____ and are best known as ______.
A)actin, microfilaments
B)keratin, microfilaments
C)actin, intermediate filaments
D)keratin, intermediate filaments
E)tubulin, intermediate filaments

Accepted Answer

Filaments connected to the dense plaque in a hemidesmosome are composed of keratin and are best known as intermediate filaments.

Question 5

You coat a Petri dish with fibronectin and proteoglycans and then culture cells on the dish. The cells adhere to the dish. You repeat the experiment but this time add RGD tripeptides to the culture dish as the cells are added. The result of this experiment is an example of what biochemical process?
A)competitive inhibition
B)noncompetitive inhibition
C)enzymatic activation
D)feedback inhibition
E)allosterism

Accepted Answer

The addition of RGD tripeptides, which mimic the cell adhesion sites on fibronectin and proteoglycans, competes with these molecules for binding to cell surface receptors, thus preventing the cells from adhering to the dish. This is an example of competitive inhibition, where the inhibitor (RGD tripeptides) competes with the substrate (fibronectin and proteoglycans) for the active site on the target (cell surface receptors).

Question 6

The tightest attachment between a cell and its extracellular matrix is seen at the site where an epithelial cell is attached to the underlying basement membrane. The specialized adhesive structure found at such a site is called a(n)________.
A)tight junction
B)spot desmosome
C)plasmodesma
D)hemidesmosome
E)gap junction

Accepted Answer

The specialized adhesive structure found at the site where an epithelial cell is attached to the underlying basement membrane is called a hemidesmosome.

Question 7

Cells were allowed to bind to beads that had been covered with a coating of fibronectin. When the membrane-bound beads were pulled by an optical tweezer, the resultant mechanical stimulus was transmitted into the cell interior. What response did this cause?
A)It generated a wave of Src kinase activity.
B)It caused nuclear shrinkage.
C)It caused activation of phosphofructokinase.
D)It caused inhibition of phosphofructokinase.
E)It inhibited Src kinase activity.

Accepted Answer

The mechanical stimulus generated by the optical tweezer would activate the Src kinase pathway.

Question 8

Focal adhesions ________.
A)may act as a type of sensory structure
B)collect information about the physical properties of the extracellular environment
C)collect information about the chemical properties of the extracellular environment
D)transmit information to the cell interior that may lead to changes in cell adhesion, proliferation or survival
E)all of these are correct

Accepted Answer

Focal adhesions serve as both mechanical anchors for a cell and as sites for information gathering about the extracellular environment. They are able to sense and respond to changes in the physical and chemical properties of their surroundings, transmitting this information to the cell interior and potentially leading to changes in cell behavior such as adhesion, proliferation, or survival.

Question 9

What proteins have been shown to be altered by genetic mutations in patients who suffer from epidermolysis bullosa? A)the $\alpha$₆ integrin subunit B)the $\beta$₄ integrin subunit C)collagen VII D)laminin-5 E)all of these are possibilities

Accepted Answer

All of these proteins have been shown to be altered by genetic mutations in patients with epidermolysis bullosa. Mutations in the F1F1F1S1F1F1F10₆ and F1F1F1S1F1F1F10₄ integrin subunits result in various forms of junctional epidermolysis bullosa. Mutations in collagen VII lead to dystrophic epidermolysis bullosa, and mutations in laminin-5 result in Herlitz junctional epidermolysis bullosa.

Question 10

Which disease is an inherited blistering disease that can occur in patients with genetic alterations in any one of a number of hemidesmosomal proteins, including the $\alpha$₆ or $\beta$₄ integrin subunit, collagen VII or laminin-5? A)epidermolysis bullosa B)bullous pemphigoid C)blisterosis D)hemidesmosomosis E)eczema

Accepted Answer

The description matches epidermolysis bullosa, which is an inherited blistering disease caused by mutations in genes coding for keratin or hemidesmosomal proteins. The listed hemidesmosomal proteins are known to be affected in different subtypes of the disease.

Question 11

Evidence strongly suggests that the bent conformation of an integrin is _______ and unable to bind its ligand.
A)loose
B)active
C)tight
D)stretched
E)inactive

Accepted Answer

Studies have shown that the bent conformation of integrins is inactive and unable to bind their ligand. Therefore, the correct choice is E - inactive.

Question 12

If experimentally linked $\alpha$/$\beta$ heterodimer integrin subunits are separated, what happens?
A)The molecules bind their ligand tightly
B)The molecules are unable to bind a ligand.
C)The molecules are cleaved.
D)The molecules denature their ligand.
E)The molecules are denatured and degraded.

Accepted Answer

The answer of If experimentally linked $\alpha$/$\beta$ heterodimer integrin subunits...

Question 13

The activation of a membrane integrin by the binding of its cytoplasmic portion to molecules in the cytoplasm and the resultant increase in its affinity for an extracellular ligand is called ________.
A)inside-out signaling
B)outside-in signaling
C)right-side-out signaling
D)simple signaling
E)integrination

Accepted Answer

This process is called inside-out signaling, where signaling molecules inside the cell activate membrane proteins to increase their affinity for extracellular ligands.

Question 14

You coat a Petri dish with fibronectin and proteoglycans and then culture cells on the dish. The cells adhere to the dish. You repeat the experiment but this time add RGD tripeptides to the culture dish as the cells are added. What happens?
A)The cells adhere as they normally do.
B)The cells die immediately.
C)The cells lyse immediately.
D)The cells do not adhere to the dish.
E)The cells immediately change their phenotype.

Accepted Answer

RGD tripeptides are known to inhibit cell adhesion by competing with fibronectin for binding to integrins on the cell surface. Therefore, if RGD tripeptides are added to the culture dish, the cells will not be able to bind to the fibronectin-coated dish and will not adhere.

Question 15

In an integrin, what structure is it that crosses the lipid bilayer?
A)a transmembrane pleated sheet
B)a transmembrane spear
C)a transmembrane plate
D)a transmembrane helix
E)a bent, curved leg

Accepted Answer

The transmembrane region of integrins is a single alpha helix that crosses the lipid bilayer.

Question 16

In which disease does an individual produce antibodies against proteins present in hemidesmosmes?
A)epidermolysis bullosa
B)bullous pemphigoid
C)hemidesmosomosis
D)eczema

Accepted Answer

The production of antibodies against proteins present in hemidesmosomes is characteristic of bullous pemphigoid, a chronic autoimmune skin disease. Epidermolysis bullosa, on the other hand, is a genetic disorder that affects the skin's structural proteins and causes blisters. Hemidesmosomosis is not a recognized medical condition, and eczema is a broad term used to describe various skin conditions characterized by inflammation and itching.

Question 17

Focal adhesions ________.
A)have been implicated in cell locomotion
B)contain integrins that develop transient interactions with the extracellular matrix
C)collect information about the chemical properties of the extracellular environment
D)transmit information to the cell interior that may lead to changes in cell adhesion, proliferation or survival
E)all of these are correct

Accepted Answer

Focal adhesions have been implicated in cell locomotion, contain integrins that develop transient interactions with the extracellular matrix, collect information about the chemical properties of the extracellular environment, and transmit information to the cell interior that may lead to changes in cell adhesion, proliferation, or survival. Therefore, all of the given choices are correct.

Question 18

You are investigating the interactions of integrin $\alpha$ and $\beta$ subunits and isolate the extracellular portion of an integrin as a soluble $\alpha$/$\beta$ heterodimer. The heterodimer lacks the associated transmembrane and cytoplasmic domains normally present as part of the molecule. You experimentally link the $\alpha$ and $\beta$ subunits at the bases of their legs so that the ligand-binding regions of the $\alpha$and $\beta$ subunits approach one another and the legs are in the bent conformation. Which of the following statements is the best prediction of what will happen?
A)The molecules will bind their ligand tightly.
B)The molecules will be unable to bind a ligand.
C)The molecules will be cleaved.
D)The molecules will denature their ligand.
E)The molecules will denature and degrade.

Accepted Answer

The bent conformation of integrins is associated with an inactive state, which prevents ligand binding.

Question 19

What ion is NOT known to bind to integrins?
A)calcium
B)magnesium
C)sodium
D)divalent cations
E)manganese

Accepted Answer

Sodium is not known to bind to integrins, while calcium, magnesium, divalent cations, and manganese are all known to bind to integrins.

Question 20

Epidermolysis bullosa, an inherited blistering disease, is caused by ________.
A)production of antibodies against hemidesmosome plaque proteins
B)production of autoantibodies
C)production of antibodies against spot desmosome plaque proteins
D)genetic alterations in any one of a number of hemidesmosomal proteins
E)production of antibodies against connexins

Accepted Answer

Epidermolysis bullosa is caused by genetic alterations in any one of a number of hemidesmosomal proteins, which are responsible for anchoring the epidermis to the underlying dermis. This results in fragile skin that is prone to blistering and tearing. Antibodies do not play a direct role in the development of this disease.

Quiz 7: Interactions Between Cells and Their Environment

In focal adhesion, large clusters of integrins bond to which component via various adaptors?

What kind of experiments have provided evidence that most integrins have unique functions?

Why do cells flatten out as they make contact with a surface?

Filaments connected to the dense plaque underlying the membrane in a hemidesmosome course outward into the cytoplasm. These filaments are composed of the protein _ and are best known as __.

You coat a Petri dish with fibronectin and proteoglycans and then culture cells on the dish. The cells adhere to the dish. You repeat the experiment but this time add RGD tripeptides to the culture dish as the cells are added. The result of this experiment is an example of what biochemical process?

The tightest attachment between a cell and its extracellular matrix is seen at the site where an epithelial cell is attached to the underlying basement membrane. The specialized adhesive structure found at such a site is called a(n) ________.

Cells were allowed to bind to beads that had been covered with a coating of fibronectin. When the membrane-bound beads were pulled by an optical tweezer, the resultant mechanical stimulus was transmitted into the cell interior. What response did this cause?

Focal adhesions ________.

What proteins have been shown to be altered by genetic mutations in patients who suffer from epidermolysis bullosa?

Which disease is an inherited blistering disease that can occur in patients with genetic alterations in any one of a number of hemidesmosomal proteins, including the $\alpha$ ₆ or $\beta$ ₄ integrin subunit, collagen VII or laminin-5?

Evidence strongly suggests that the bent conformation of an integrin is _______ and unable to bind its ligand.

If experimentally linked $\alpha$ / $\beta$ heterodimer integrin subunits are separated, what happens?

The activation of a membrane integrin by the binding of its cytoplasmic portion to molecules in the cytoplasm and the resultant increase in its affinity for an extracellular ligand is called ________.

You coat a Petri dish with fibronectin and proteoglycans and then culture cells on the dish. The cells adhere to the dish. You repeat the experiment but this time add RGD tripeptides to the culture dish as the cells are added. What happens?

In an integrin, what structure is it that crosses the lipid bilayer?

In which disease does an individual produce antibodies against proteins present in hemidesmosmes?

Focal adhesions ________.

What ion is NOT known to bind to integrins?

Epidermolysis bullosa, an inherited blistering disease, is caused by ________.

Quiz 7: Interactions Between Cells and Their Environment

In focal adhesion, large clusters of integrins bond to which component via various adaptors?

What kind of experiments have provided evidence that most integrins have unique functions?

Why do cells flatten out as they make contact with a surface?

Filaments connected to the dense plaque underlying the membrane in a hemidesmosome course outward into the cytoplasm. These filaments are composed of the protein _____ and are best known as ______.

You coat a Petri dish with fibronectin and proteoglycans and then culture cells on the dish. The cells adhere to the dish. You repeat the experiment but this time add RGD tripeptides to the culture dish as the cells are added. The result of this experiment is an example of what biochemical process?

The tightest attachment between a cell and its extracellular matrix is seen at the site where an epithelial cell is attached to the underlying basement membrane. The specialized adhesive structure found at such a site is called a(n) ________.

Cells were allowed to bind to beads that had been covered with a coating of fibronectin. When the membrane-bound beads were pulled by an optical tweezer, the resultant mechanical stimulus was transmitted into the cell interior. What response did this cause?

Focal adhesions ________.

What proteins have been shown to be altered by genetic mutations in patients who suffer from epidermolysis bullosa?

Which disease is an inherited blistering disease that can occur in patients with genetic alterations in any one of a number of hemidesmosomal proteins, including the α\alphaα 6 or β\betaβ 4 integrin subunit, collagen VII or laminin-5?

Evidence strongly suggests that the bent conformation of an integrin is _______ and unable to bind its ligand.

If experimentally linked α\alphaα / β\betaβ heterodimer integrin subunits are separated, what happens?

The activation of a membrane integrin by the binding of its cytoplasmic portion to molecules in the cytoplasm and the resultant increase in its affinity for an extracellular ligand is called ________.

You coat a Petri dish with fibronectin and proteoglycans and then culture cells on the dish. The cells adhere to the dish. You repeat the experiment but this time add RGD tripeptides to the culture dish as the cells are added. What happens?

In an integrin, what structure is it that crosses the lipid bilayer?

In which disease does an individual produce antibodies against proteins present in hemidesmosmes?

Focal adhesions ________.

What ion is NOT known to bind to integrins?

Epidermolysis bullosa, an inherited blistering disease, is caused by ________.

Filaments connected to the dense plaque underlying the membrane in a hemidesmosome course outward into the cytoplasm. These filaments are composed of the protein _ and are best known as __.

Which disease is an inherited blistering disease that can occur in patients with genetic alterations in any one of a number of hemidesmosomal proteins, including the $\alpha$ ₆ or $\beta$ ₄ integrin subunit, collagen VII or laminin-5?

If experimentally linked $\alpha$ / $\beta$ heterodimer integrin subunits are separated, what happens?