Unit 7: Cell Adhesion And Stem Cells

Front 1

Describe the two main properties of stem cells that distinguish them from other cells.

Back 1

1. They exhibit self-renewal. This means they can reproduce themselves.

2. Can exhibit asymmetric division.
- can divide to form themselves and also a differentiated cell with a specific function and fate.

Front 2

Describe the process of ESC growth in culture.

Back 2

1. Cleavage-stage embryos, produced from IVF, are used to grow blastocysts.
2. The inner cell mass is then isolated and plated onto fibroblast cells. These cells provide nourishment to the embryonic cells.
3. Replating occurs after dissociation of the inner cell mass into individual cells. Again, a layer of feeder cells are used for nourishment.
4. This results in the formation of ESC colonies, which can be stored and maintained.

Front 3

A zygote exhibits what type of stem cell properties and why is a zygote not considered a true stem cell?

Back 3

A zygote demonstrates properties of totipotent stem cells, meaning it has the potential to generate all cell types. It is not considered a true stem cell because it does not exhibit self-renewal.

Front 4

What is symmetric division as it relates to stem cells? Does this result in more or less stem cells?

Back 4

Symmetric division is cell division that results in two daughter stem cells that are identical to the parent stem cell.

Results in an increase in stem cells.

Front 5

What is the difference between a stem cell and a progenitor cell in terms of potency?

Back 5

1. A stem cell is an unspecialized cell that has the potential to reproduce themselves (self-renewal) as well as the potential to produce more specialized cells indefinitely.

2. Embryonic stem cells (ESCs) are totipotent, having the ability to give rise to specialized cells of each tissue type.

3. Adult stem cells are pluripotent.

4. Progenitor cells are the intermediate cells of a given cell lineage. Progenitor cells have the potential to give rise to different differentiated and specialized cells but are more limited than the stem cells from which they arose.

Depending on progenitor cell type, they can be classified as unipotent (ability to differentiate into 1 specialized cell type) or oligopotent.

Front 6

Briefly explain the progress of early development in terms of cell potency and cell fate?

Back 6

- The zygote is formed and undergoes first 3 round of division, known as the 8-cell stage. These 8 cells are totipotent, each having the ability to give rise to an entire animal.

- At the 16- cell stage, the cells are now pluripotent as some commit to certain differentiation paths.

- After additional divisions, a 64- cell mass is produced which separates into 2 cell types, the trophectoderm and the inner cell mass. The inner cell mass is where ESCs reside which go on to differentiate into the 3 germ layers. Each of the 3 germ layers have distinct cell fates.

Front 7

Describe the germ line restriction that occurs in animals during early development. Why did evolution select for this restriction mechanism?

Back 7

During early animal development, stem cells and precursor cells that will form the germ line are set aside.

Germ cells (egg and sperm): specialized cells that give rise to new organisms. Evolution selected for this restriction mechanism in order to protect the genetic material passed down from progeny to progeny.

Only the genome of the germ line will ever be passed on to progeny.

Front 8

What two forms do integrins exist in ?

Back 8

Integrins exist in two conformations- a low affinity (inactive) form and a high-affinity (active) form.

Front 9

Integrins act as "bridges" in what manner?

Back 9

Integrins connect epithelial cells to the basal lamina and "through adapter proteins, to intermediate filaments of the cytoskeleton" (Lodish, 833). The integrins form a bridge "between the ECM and cytoskeleton; they do the same in nonepithelial cells" (Lodish,833).

Front 10

Describe the adhesive structures of integrins.

Back 10

In nonepithelial cells, integrins are clustered into adhesive structures. These structures can be seen using fluorescent microscopy "with the use of antibodies that recognize integrins" (lodish, 833).

Front 11

Explain why a mutation in an integrin subunit can result in the dysfunction of only one cell type, despite the fact that integrins are ubiquitious throughout the various tissues of the human body.

Back 11

Integrins are heterodimers composed of distinct alpha and beta subunits. Humans can form 18 different alpha chains and 8 different beta chains, each of which bind to a different complementary chain. The result is a wide array of integrin types that vary by cell type. A mutation in one integrin subunit, therefore, may result in the dysfunction of only one type of cell, if that cell type is the only cell type to utilize that specific integrin type.

Front 12

Explain why a disease that inhibits integrin binding with fibrinogen can result in excessive bleeding.

Back 12

Blood clots form when platelets adhere to one another through fibrinogen bridges that are linked via platelet integrins.

Front 13

Why are some novel vaccines and antiviral drugs based upon integrin antagonists?

Back 13

Viruses employ integrins to bind and gain entry into cells. Binding to integrins allows a virus to attach to a target cell type and simultaneously gain access to the cell's signalling pathways.

Front 14

Which subunit of dystroglycan binds components of the ECM and what molecule does it use to bind these components?

Back 14

The alpha subunit binds to laminin, perlecan, and agrin in the extracellular matrix. Special O-linked oligosaccharides attached to the alpha subunit bind to these ECM components.

Front 15

What protein in the DGC is involved in the signaling pathway for muscle relaxation and explain the process.

Back 15

Nitric oxide synthase (NOS) is involved in the signaling pathway for muscle relaxation. When intracellular Ca+ rises, NOS produces the signaling molecule nitric oxide which diffuses into smooth muscle to promote muscle relaxation.

Front 16

What do studies of Duchenne Muscular Dystrophy reveal about the function of dystroglycan?

Back 16

Studies of DMD reveal that dystroglycan binds to laminin in the ECM and plays an important role in the assembly and stability of the basement membrane.

Front 17

What are the 4 classes of plant cell tissues?

Back 17

Dermal, vascular, ground and sporogenous

Front 18

.How does the cell grow at the meristems since the plant cell wall matrix is so sturdy?

Back 18

Auxins weaken the cell wall at a certain location, expanding the vacuole uptake of water which pushes the cell out. The cell expands and grows. The wall thickens around the growth.

Front 19

List 4 main functions of the cell wall.

Back 19

Many different choices such as, it communicates with adjacent cells, sends signals, responsible for growth, differentiation, cell shape, division, it provides a barrier, withstand turgidity of the cell/plant and is built for strength.

Front 20

What is the adhesive like kinase family unique to plants?

Back 20

Wall associated kinases

Front 21

What extracellular region do plant WAKs have in common with animal cell surface receptors?

Back 21

Extracellular Matrix

Front 22

Where are molecules located that allow pollen to bind to the stigma?

Back 22

Epidermal growth factor repeats

Front 23

What are the major differences in properties between type I and type II collagen?

Back 23

The differences are in 1)the fibrils of type I collagen are larger in diameter than type II fibrils; 2) Type I collagen fibrils forms long fiber vs Type II collagen fibrils form mesh; 3)type I collagen coassembles with type V and type XI collagens, vs type II collagen coassembles with type IX collagen

Front 24

In tendons, what is the orientation of type I collagen fibrils?

Back 24

The type I collagen fibrils are oriented in the direction of the stress applied to the tendon.

Front 25

What is osteogenesis imperfecta? And how is this disease related to mutation in type I collagen?

Back 25

osteogenesis imperfecta is a disease of brittle-bone. Because every third position in a type I collagen alpha chain must be a glycine for the triple helix to form, mutation of glycine to almost any other amino acids result in poorly formed and unstable helix structure, so unstable type I collagen fibrils, which lead to the bone tissue can not take much stress.

Front 26

How does the structure of Type IV collagen align in connective tissue?

Back 26

Type VI collagen monomers align antiparallel.

Front 27

What do Type V and Type XI fibrillar collagens provide in tendons?

Back 27

Type V and Type XI fibrillar collagens coassemble with type I collagen and regulates the property and structure.

Front 28

In cartilage, what do the kinks in Type IX collagen provide?

Back 28

The kinks prevents the type IX collagen from assembling into fibrils.

Front 29

What does the random insertion of type II collagen fibril into the viscous proteoglycan matrix do?

Back 29

It provides rigidity, strength and resistance to deformation for shock absorption in cartilage.

Front 30

What is unusual about type VI collagen?

Back 30

Type VI collagen consists of a short triple helix (comparatively) with globular domains at both ends.

Front 31

Describe the mutations that cause osteogensis imperfecta, a brittle-bone-disease.

Back 31

Mutations in the genes encoding type I collagen α1(I) or α2 (I) chains can cause osteogensis imperfecta. Mutations in glycine to other amino acids result in poorly formed and unstable triple helices. One defective α chain can disrupt the whole molecule’s triple-helix structure. A mutation of α1(I) or α2 (I) genes can cause osteogensis imperfecta.

Front 32

Describe the general structure of GAGs.

Back 32

GAGs are linear polymers that contain two sugars: one sure is either uronic acid or D-galactose, the second sugar is N-acetylglucosamine or N-acetglygalactosamine. At least one sugar contains at least one anionic group.

Front 33

Using heparain as an example, describe how sets of sugar-residue sequences, rather than single unique sequences, are responsible for specifying distinct GAG functions

Back 33

A set of five-residue sequences found in a subset of heparin GAGs is responsible for controlling the activity of ATIII. The pentasaccharide sequences in heparin must be sulfated at two specific positions in order for heparin to be able to activate ATIII. Although other sulfates can be present in a number of different combinations, they are not essential for the anticlotting activity of heparin.

Front 34

Briefly describe how chondroitin sulfate is synthesized.

Back 34

The synthesis of chondroitin sulfate is initiated by the transfer of a xylose residue to a serine residue on the core protein in the Golgi complex. Next, two galactose residues are added. Glucuronic acid and N-acetylgalactosamine residues are then sequentially added to the linking sugar.

Front 35

Describe the physical role of GAGs.

Back 35

GAGs' structure and composition trap and impede flow of water molecules which prevents deformation by compression in locations such as cartilage.

Front 36

What functional groups in GAGs make them highly acidic?

Back 36

The combination of multiple sulfate and carboxyl groups.

Front 37

What does the basal laminal protetoglycan perlecan often have attached?

Back 37

The basal laminal proteoglycan perlecan is a heparin sulfate proteoglycan commonly with three or four GAG chains or a bound chondroitin sulfate chain attached.

Front 38

Describe syndecans and what they bind to.

Back 38

Syndecans are cell-surface proteoglycans expressed by epithelial and nonepithelial cells. The cytosolic domain interacts with the actin cytoskeleton and extracellular domain binds collagens and multiadhesive matrix proteins, which anchor the cells to the extracellular matrix.

Front 39

How do syndecans in the hypothalamic region of the brain modulate feeding behavior in response to food deprivation?

Back 39

Syndecans in the hypothalamic region of the brain bind to cell-surface receptors of antisafety peptides that help control feeding behavior.

Front 40

What are the two types of cell-surface proteins?

Back 40

The two types of cell-surface proteins are integral membrane proteins (syndecans) and GPI-anchored proteins (glypicans).

Front 41

How do cells avoid premature assembly of collagen within the cell?

Back 41

Collagen molecules are secreted by cells in a precursor form known as procollagen. Procollagen features additional peptides at each end that prevent assembly. Extracellular procollagen proteinases cut off the terminal peptides to allow for collagen assembly once the molecules have been secreted from the cell.

Front 42

Explain how a genetic defect in Type 1 Collagen formation can lead to hyper-elastic skin and joints.

Back 42

Abnormally stretchable skin is part of a genetic syndrome, known as Ehlers-Danlos syndrome, that arises from a defect in collagen cross-linking or assembly. Without the resistance provided by aligned collagen formation in the connective tissues, as with Ehlers-Danlos syndrome, skin and joints become more elastic and hypermobile.

Front 43

What are the 2 main differences between ESCs and adult SCs?

Back 43

There are 2 main differences between ESCs and adult SCs. One is their different abilities in the number and type of differentiated cell types they can become. ESCs can differentiate into all cell types of the body, where as adult SCs are limited to differentiating into different cell types of their tissue of origin. The second major difference is that ESCs are more easily grown in culture than adult SCs. This is due to the fact that adult SCs are rare in mature tissues, making isolation of these cells very difficult. Also, methods to expand their numbers in cell culture are still being developed, adding to the difficulty.

Front 44

What are induced pluripotent stem cells and why are they so important in the field of stem cell biology?

Back 44

Induced pluripotent stem cells (iPSCs) are adult SCs that have been genetically reprogrammed to an ESC-like state by being forced to express genes and factors that are crucial for maintaining the characteristic properties of ESCs. However, it is important to note that iPSCs are NOT ESCs! iPSCs are important to the field of stem cell biology because of their great potential in many aspects of biology. iPSCs are useful tools for drug development and modeling of diseases. The study and creation of iPSCs will help researchers learn how to reprogram cells to repair damaged tissues in the human body, which will greatly advance the field of regenerative medicine.

Front 45

What are the two cell types that the early embryo develop into?

Back 45

trophectoderm (TE) and the inner cell mass (ICM)

Front 46

Briefly describe the difference between plurioptent and totipotent.

Back 46

Pluripotent-Cell can divide into any of the germ layers. Totipotent-All differentiated cells in an organism.

Front 47

What is an example of a macromolecule located in the ECM that are important for adhesion?

Back 47

A protein called chymocyanin works with SCA to direct the movement of the sperm-containing pollen tube to the ovary.

Front 48

Do adhesive molecules in plants have homologous animal counterparts?

Back 48

"plants do not produce homologs of the common adhesive molecules found in plants. Only a few adhesive molecules unique to plants have been well documented to date" (Lodish, 842)

Front 49

1. About how many rounds of cell division does it take to create an adult C. elegans?

Back 49

~10 Rounds

Front 50

How many types of founder cells orchestrate the development of C. elegans?

Back 50

Six

Front 51

What role does Wnt signaling play in C. elegans development?

Back 51

Controls the division of the EMS founder cells into E and MS cells

Front 52

What does the name “EMS” stand for with respect to the EMS founder cell?

Back 52

Since it is the precursor to the E (gut) and MS (other cells), it is called the EMS founder cell

Front 53

What type of molecule is lin-4 and let-7 and what is their function?

Back 53

Lin-4 and let-7 are micro-RNAs that block translation of heterochronic genes such as lin-14 by binding to the DNA.

Front 54

What happens to C. elegan development events in heterochronic mutants?

Back 54

In heterochronic mutants, development either happens to early (precocious development) or too late (retarded development).

Front 55

How do cells avoid premature assembly of collagen within the cell?

Back 55

Collagen molecules are secreted by cells in a precursor form known as procollagen. Procollagen features additional peptides at each end that prevent assembly. Extracellular procollagen proteinases cut off the terminal peptides to allow for collagen assembly once the molecules have been secreted from the cell.

Front 56

Explain how a genetic defect in Type 1 Collagen formation can lead to hyper-elastic skin and joints

Back 56

Abnormally stretchable skin is part of a genetic syndrome, known as Ehlers-Danlos syndrome, that arises from a defect in collagen cross-linking or assembly. Without the resistance provided by aligned collagen formation in the connective tissues, as with Ehlers-Danlos syndrome, skin and joints become more elastic and hypermobile.

Front 57

What are the long repeating linear polymers in proteoglycans called?

Back 57

Glycosaminoglycans (GAGs)

Front 58

How are heparan sulfate or chondrotitin sulfate chains formed?

Back 58

By the sequential addition of repeating units to a three sugar linker that is attached to serine residues in a core protein molecule.