A.) Compare and contrast collagen in animals to cellulose in plants. B.) Explain

Question

A.) Compare and contrast collagen in animals to cellulose in plants.

B.) Explain the difference between laminins and lamins.

C.) What is one of the most abundant proteins found in animals?

D.) Compare and contrast intercellular attachments between plant and animal cells.

E.) Compare and contrast tight junctions and desmosomes.

F.) Compare and contrast plasmodesmata and gap junctions.

G.) Explain the difference between symplast and apoplast

H.) Where would you find tight junctions?

I.) Define paracrine signaling

Explanation / Answer

A) Comparison between cellulose and collagen

Cellulose is the glucose polymer that is formed by beta glucose units connected with beta (1à4) glycosidic bonds. Collagen is a protein polymer formed by linking of amino acids with peptide bonds.

Cellulose is unbranched single chain while collagen consists of three polypeptide chains.

The monomer present in cellulose is only one type while in collagen many types of amino acids are present proline, glycine, hydroxylysine and hydroxyproline.

Cellulose is the polysaccharide present in plants while collagen is the structural protein that is present in animals, tendons, connective tissue, ligaments, bone and teeth.

B) Difference between laminins and lamins

Laminins are glycoproteins involved in the formation of structural scaffolds in the tissues of the organism. They are present in the extracellular matrices and form a major component in the basal lamina. Laminins are important for the survival and maintenance of the tissues.

Lamins are fibrous proteins that provide structural components and regulation of transcription in the nucleus. Nuclear lamins interact with the membranous proteins to form internal nuclear lamina below the nuclear envelope. Lamins participate in the disassembling and reformation of nuclear envelope at the time of mitosis as well as during the nuclear pore positioning.

C) Abundant protein found in animals

Collagen is found to be one of the abundant proteins present in animals and constitute 30 percent of the total proteins.

D) Intercellular attachments between the cells in plants and in animals

Plasmodesmata are the junctions present between two adjacent cells in plants. Plasmodesmata are the cell wall openings connecting the membranes.

In animal cells, tight junctions, gap junctions, adherens junctions and desmosomes are the junctions present between two adjacent cells.

E) Compare tight junctions and desmosomes

Tight junctions seal two adjacent epithelial cells with a network of claudins and other proteins. Tight junctions help in choosing the molecules and ions that can pass through the tissue. They control the type of substances that are allowed through the space between the tissues. These junctions also help in the movement of the integral proteins of the membrane in between the baso-lateral surface and apical surface of the cell.

Desmosomes are just the patches that attach two cells together. They are connected to the intermediate filaments of cytoplasmic keratin.

F) Comparison between plasmodesmata and gap junctions

Gap junctions are present in animal cells while plasmodesmata are present in plant cells. Gap junctions are the connections between the cells with a diameter of about 1.5nm to 2nm. They help in the passage of ions and small molecules of 1000daltons Mol. Wt. They are cylindrical structures that are constructed from six copies of transmembrane proteins known as connexins. They show changes in membrane potential as they allow ions to pass through.

Fine cytoplasmic strands of the plant cell extending through the pores of the cell wall and connecting the cytoplasm of the two cells are called plasmodesmata. They help in the movement of ions, small molecules and even macromolecules between the cells. Plasmodesmata are covered by plasma membrane that is continuous with the adjacent cell forming the basis for a syncytium.

G) Difference between symplast and apoplast

Symplast constitutes living portion of the plant that includes protoplasts while apoplast constitutes non-living portion of the plant like cell wall and intercellular spaces. Resistance exists in the flow of water in symplast while there is no resistance in the water flow in the case of apoplast. Root metabolism influences the symplast pathway while it does not affect the apoplastic pathway.

H) Where are tight junctions found?

They are found in the epithelial cells.

I) Define Paracrine signaling

Paracrine signaling is a type of cell to cell communication by sending the signals from one cell to another and induce some alterations in their differentiation and behavior.

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