Cells are surrounded by cell membrane-layered structure made up of lipids&proteins-lipoprotein,called plasmalemma.Electrostatic attraction,selectively permeable

Firmness is due to turgor pressure(water pushing out),the strength of cell wall,efficiency of adjacent cell placement.Wall is microfibrils embedded by pectin to matrix

Pectin is most easily affected.It consists of galacturonic acid&little rhamnose.If acid is ester matrix is weaker.When heated pectin becomes H2O soluble

Animal muscles

Skeletal(normal),cardiac(heart),smooth(surrounds organs)

Connective tissue proteins contributing to structure are collagen(polypeptide chains in triple helix that stand side by side to form fibrils)and elastin(can roll like ball)

Each muscle fibre consist of myofibrils |actin(I)myosin(A)actin|zline|sacromere|

A-thick filaments of myosin polymer(connected to Z by titin),I-thin filaments of actin

When animal dies rigor mortis occurs,so it is allowed to stand couple of days(tenderisation due to enzyme calpain or added papain(found in fruits)