Interactions Between Cells and their Environment

What are tissues? How are they made?

• Epithelial cell sinteract with one another through junctions to form tissues

All junctions from top of the epithelial cell to the bottom - 5 parts

• Which junctions holds the sheets together

• Only name them

• What functions are cell-cell anchoring junctions

• Which are cell-ECM anchoring junctions

• Polarity of epithelial cells: naming

• Tight junctions

• Adherens junctions

• Desmosomes

• Gap junctions

• Hemidesmosome

Top three holds the sheets together

• Cell to cell: adherens junctions and desmosomes

• Cell to ECM: Hemidesmosomes

Polarity

• apical vs basal

• Apial towards extracellular matric

• Basal towards the basal lamina

tight junctions

• Functino of tight junctions (two functions)

• What do tight junctions form

• What two transmembrane proteins make up the tight junctions

  • How do the proteins bind and what do they do

• Create a seal between cells to prevent the mixing of extracellular matrixs

• Prevent the mixing of membrane protein (recall the slices with glucose and Na pumps)

• Forms a sealing strand or tight junction belt

Transmembrane proteins

• claudin and occludin (namming cluaudia and occula)

• For the interactions between the two extracellular domains

• Homophilic binding

  • O with O

  • C with C

Anchoring Junctions

• adheren junctions/desmosome - what do they do/achor

• Hemidesmosomes - what do they do/anchor

• What proteins are involved in anchoring

  • Two types of proteins and their functions

  • One type of protein has two domains explain what they do

  • Second type: what kind of protein are they - referring to the types from the previous lecture

• Do the types of proteins differ according to the type of anchoring junctions?

  • Type of protein for adheren, desmosome, hemidesmosomes

  • What does the linker protein bind to what kind of filament

• Adheren junctions/desmosomes: anchor the cytoskeletons of the neighbouring cells together

• Hemidesmosomes - anchor the cutoskeleton of one cell to the basal lamina

Proteins

• transmembrane adhesion proteins

  • Extracellular domain links with other adhesion proteins or the matrix

  • Intracellular domain links with the linker proteins

• Linker proteins

  • They are cytosolic proteins

  • Links the adhesion proteins to the cytoskeleton filaments

differs: yes

• adheren: cadherins

  • Homophilic binding

  • Linker binds to actin

• Desmosomes: desmoglein and desmocollin

  • Homophobic and heterphilic binding

  • Linker proteins link to keratin filaments - intermediate filaments

• Hemidesmosomes: integrins

  • No philic, phobic binding

  • Linker proteins binds to the keratin filaments - intermediate filament

Gap junctions

• Structure building block

• What does it allow - what kind of structure entails if the function is turned on or off

• Coupling cells

  • How does it couple cells

    • What does it allow in

• Gated function

  • How does doapmine work with the gates

  • Why do we have gates?

• 1 subunit = connexin

• 6 connexin = connexons

• 2 connexons = channel

• Channel forms = communication between cells

• Only one connexon = no communication

• Coupling through metabollical and electrically

• Allow passahe of metabolites and ion but only very small

  • e.g. AA, glucose, nucleotides, cAMP

• Gated function

  • Allows the opening and closeing state based on extracellular ot intracellular signals

  • Dopamine closes gate

  • Very important to protect the cell if neighbouring cell dies e.g. Ca leaves very quickly = cell dies = neighbouring cell must close or else loses their own Ca as well and dies

Intercellular Junctions in plant cells

• What is unique compared to epithelial cell junctions

• What is one cell junction do they have and why is it super unique

  • How is the movement of things regulated - how do gates work

• do not have cell junction similar to the ones in animal cells

• Plasmodesmata

  • Communication between cells

  • Movement

    • Smaller electrically charged molecules allow to move freely

    • Larger soluble molecule controlled by gating

  • uniqueness: sharing to the cytoplasm, ER, plasma membrane, and cell wall

• Gating

  • Works by the control of cellulose composition, control by its reverse

Parts of an animal tissue

• 3 main parts - only name

• epithelium

• Basal lamina

• Connective Tissue

Epithelial tissue

• cell compositions and how they interact

• Amount of ECM access

• What provides resistance to mechnical stress

• cells are closely together and attached to one another

• Limited access to ECM by only the basal lamina

• The cytoskeleton filaments provide resistance to mechincal stress

Connective tissue

• cell composition and what do they interact with

• Amount of ECM

• What provides resistance to mechanical stress

• Cell not close to each other, very closely interacting with ECM

• Lots of ECM

• ECM provides resistance to mechanical stress

Extracellular matrix

• 3 macromolecules of the extracellular matrix

• Only list

1) glycosaminoglycans and proteoglycans

2) Fibrous proteins

3) Glycoproteins

Glycosaminoglycans (GAGs)

• What is it

• Its charge

• What does it help in

• What is hyaluronan?

  • Where is it made in

• a repeating disaccharide sugar

• negatively charged

• Form gels that resist compression

• Hyaluronan

  • Made specifically by the plasma membrane enzyme complex and is up to 25000 subunits long and disaccarides

Proteoglycans

• what makes them unique from glycoproteins

• How much of its weight is sugar

• proteoglycans are a type of glycoproteins that have at least on GAG bound to it

• 95 percent of its body weight is just sugar

Fibrous proteins

• what are the two types; just list

• collagen

• elastin

What does collagen do? - fibrous protein

• what is it made out of

• What is it function (2)

• Where is the site of synthesis (example building block structure)

• Explain its interaction with the ECM

  • How does it bind (two proteins and how do they bind and what else do they bind to?)

• Made out of ribrous protein

• Provides tensile strength

• Resist Stretching

• Site of synthesis from fibroblasts and osteoblasts as procollagen

  • Procollagen into collagen and then collagen fibrils which can then form collagen fibers

• Interaction with ECM

  • Integrin (adhesion receptor): binds to the fibronectin (glycoprotein) outside and binds to adaptor proteins inside

  • Fibronectin: will bind to the collgen and bind to integrin

elastin

• What type of protein

• What does it help with the tissues

• fibrous protein

• Provides elasticity and resilience

Basal lamina

• main function 3 functions

• Three parts of the lamina and what they do (as well as what kind of protein are they)

• separates the pithelial with the connective tissue

• prevent interactions to fibroblost with epithelial tissue

• Allows the passage of macrophages and lymphocytes (both are releated to the immune cell)

• Laminin (glycoprotein): interacts with the ECM components

• Type IV collagen (fibrous protein): provides strength

• Integrin (transmembrane adhesion protein): binds to the laminin and epithelial cells

Plant cell wall

• main components

  • What function do they help with the cell wall

  • What synthesizes them

• rigidity compared to animal tissue

• main components

  • Cellulose provides tnesile strength

    • Produced by the cellulose synthease complex and made parallel to the microtubules

  • Pectin

    • space filling to resistance to compression

  • Rest synthesized by the golgi and exocytosis