Quiz 2/Exam 2 Extracellular structures

Tight Junction

A connection between cells that prevents substances from passing between them; a type of seal that creates a barrier between cells.

plasmodesmata

A cytoplasmic channel through a plant cell wall that connects solutes of adjacent plant cells; together with others, forms a fluid transport system in plant tissue Plasmodesmata unify an entire plant, generating linkages among all the cells. Cytoskeletal structures at the sites of the plasmodesmata guide large molecules towards the channels, facilitating their entry into adjacent cells. The plasma membrane wraps around the channels of plasmodesmata, making this specific intracellular structure continuous. These connections are established as plant cells divide, rather than being added later by tunneling through thick cell walls. Essential materials, such as water, nutrients and minerals, pass through plasmodesmata, assisting in plant growth, development and survival.

Desmosome

A pair of plate-like structures that form adhesion points between cells; each plate, called a hemidesmosome, exists in the membrane of adjacent cells, and they are held together by a bridge of proteins; common among epithelial cells. Intermediate filaments composed of strong keratin proteins assist in the organization of this type of junction.

Integrins

A protein that are WITHIN the cell plasma membrane and mediates both extracellular signals and intracellular signals. On the inner side of the plasma membrane, these proteins simultaneously interact with the protein components of the cytoskeleton, specifically the microfilaments (actin). The integrins are linked to the microfilaments by adaptor proteins. Integrins also transmit messages between the microfilaments and the ECM, coordinating changes happening in the cell's outer and inner environments.

proteoglycans

A small protein linked to several carbohydrate chains that mix with collagen in the extracellular matrix. Proteoglycans can have a very high percentage of carbohydrates, up to 95% of the entire proteoglycan molecule. This allows them to hold great amount of water allowing them to act as flexible shock absorbers and space fillers. (differs form glycoproteins because this has larger chain/portion of proteins b/c of "proteins" in end. Proteoglycans have larger portion of carbohydrates b/c of the glyco in the end. )

Gap Junctions

An intercellular connection between adjacent cells that allows the passage of ions and other small molecules; directly connects the cytoplasm of two cells.

middle lamella

Between the primary walls lies the middle lamella, a space containing a thin polysaccharide layer made up of sticky pectins secreted by the cell. This layer is responsible for holding cells together.

What is the Extracellular Structures in Plants

Cell walls are actually extracellular structures, as they are located outside of the plasma membrane. Cell walls are prominent features that clearly distinguish plant cells from animal cells. The cell wall provides protection to the plant cell and maintains the cell's shape. It also prevents the excessive influx of water into plant cells. At a more general level, cell walls provide support to the entire plant, keeping it erect despite the absence of an internal skeleton.

extracellular matrix (ECM)

Combination of proteins that surrounds the cell in animals. It is a combination of proteins that surrounds the cell, also providing support and structure. Without a cell wall for support and adhesion within tissues, animal cells evolved a highly complex extracellular matrix (ECM) surrounding their plasma membranes.

Extracellular Matrix (ECM) consists of?

ECM consists mainly of glycoproteins, such as collagen and fibronectins, and polysaccharides produced by the cells. In animal cells, collagen appears to be the most highly produced glycoprotein, forming sturdy fibers in the region outside of the cell. Collagen constitutes almost 40% of the total amount of protein in the human body. These collagen fibers integrate into a network made up of proteoglycans, molecules consisting of one small protein molecule linked to several carbohydrate chains, produced by cells.

Fibronectin

Fibronectin, another type of glycoprotein, attaches the ECM to the plasma membrane (ECM found in animal cell).

collagen

Fibrous glycoprotein that mixes with carbohydrate-containing molecules in animal cells; important component of the extracellular matrix. Collagen constitutes almost 40% of the total amount of protein in the human body. These collagen fibers integrate into a network made up of proteoglycans

Two parts compose the extracellular layer of plant and animal cells.

In plant cell walls, cellulose microfibrils sit within a matrix of polysaccharides and proteins to compose. In animal cells, the fibrous glycoprotein collagen mixes with a matrix made up of carbohydrate-containing molecules. Glycoproteins are proteins bonded to one or more carbohydrates.

cell junctions

It turns out that neighboring cells develop ways of communication, sending messages from one unit to the next using physical connections. Animal cells have three major types of cell junctions, namely tight junctions, gap junctions and desmosomes.

extracellular structures in plants made of?

Sugar chains called cellulose make up the microfibrils in plant cell walls. Cellulose is produced from glucose monomers by the enzyme cellulose synthase. Cellulose is deposited in the extracellular space of plants cells, where it forms microfibrils through hydrogen bonding between the cellulose chains. Cellulose microfibrils then combine with other sugars and proteins, generating a matrix or structural foundation of the plant cell wall

Extracellular structure in plant cells summary

The cell wall provides protection to the plant cell and maintains the cell's shape. It also prevents the excessive influx of water into plant cells. At a more general level, cell walls provide support to the entire plant, keeping it erect despite the absence of an internal skeleton. Sugar chains called cellulose make up the microfibrils in plant cell walls. Three layers surround a plant cell. The primary and secondary cell walls serve as the outer covering of the plasma membrane, while the middle lamella acts as the intermediate partition between two adjacent plant cells.

How would an animal cell be impacted by the absence or depletion of an extracellular matrix?

The cell would have difficulty facilitating interactions between the internal and external cellular environments. For example, the cell might be less sensitive to changes in its environment if the extracellular matrix were not present. The cell might also experience greater damage due to extreme fluctuations in external factors.

Primary cell wall

The deposition of cellulose in the cell wall changes over time. During early plant development, a young plant produces a thin wall, known as the primary cell wall. Further growth of the plant requires the expansion of this flexible wall, with its cellulose fibers positioned perpendicular to the direction of its expansion. Early remodeling of the structural rigidity of the primary cell wall is required for cell growth. Microtubules assist in this specific activity, guiding the enzyme cellulose synthase during its synthesis of the cellulose microfibrils.

ECM Structure in animals cell and cell junctions.. even shorter summary

The extracellular matrix (ECM) surrounds the plasma membrane of animal cells and consists mainly of the glycoprotein collagen and sugar macromolecules called proteoglycans. The proteins of the ECM, including fibronectin, associate with protein receptors integrated into the cell surface, collectively known as integrins. The interactions between the ECM of neighboring cells permit the transfer of information (cell junctions).

The extracellular matrix functions

The extracellular matrix functions to communicate by sending messages from one unit to the next using physical connections called cell junctions. The three types of cell junctions are tight junctions, desmosomes and gap junctions. The extracellular matrix also plays roles in shape, support, and adhesion.

The ECM in a nutshell explained (look at diagram for extra help)

The extracellular matrix sits directly outside the plasma membrane, but is still connected to it. Collagen fibers are embedded in a network of proteoglycans. The proteins of the ECM, including fibronectin, associate with proteins called integrins that are embedded in the cell membrane. On the inner side of the plasma membrane, integrins simultaneously interact with actin microfilaments in the cytoskeleton of the cell. Integrins, membrane proteins, are attached to fibronectins which anchor collagen fibers to the plasma membrane. Internally, these integrins are associated with proteins that attach to the network of microfilaments that are part of the cytoskeleton of the cell.

basal lamina

Thick mat of ECM which separates epithelial tissues from underlying tissues.

Secondary cell wall

Upon cell maturation, a secondary cell wall develops between the primary wall and the plasma membrane. This structure confers a greater degree of durability because it consists of multiple laminated layers.

Which of the following functions in connecting the extracellular matrix (ECM) to proteins within the plasma membrane?

fibronectin fibronectin is a protein that binds to the integrins of animal cells and anchors cells to the ECM.

extracellular layer

the region right above the outer side of the plasma membrane, varies from one organismal group to another.