### layer:

Cell wall
* Most cell walls act as barriers.
* Most cell walls consist of layers
  - substances
  - contain layers
  - have layers
* Some cell walls absorb nutrients.
* Some cell walls are made of cellulose
  - chitin
  - hydrate silica
* Some cell walls contain carbohydrate cellulose
  - indigestible cellulose
  - contribute to ability
* Some cell walls cover cell membranes
* Some cell walls have patterns
  - pits
* Some cell walls make up of cellulose
  - phosphate
  - support rigid structures.
  * A 'cell wall' is the wall of a cell in plants, bacteria, fungi, algae, and some archaea. Animal cells do not have cell walls, nor do protozoa. Cell walls protect the cells from damage. It is also there to make the cell strong, to keep its shape, and to control the growing of the cell and plant
* are also fully permeable to water and solutes
  - composed mostly of chitin
  - found in plants, bacteria, fungi, algae, and some archaea
* are made of specialized sugars called cellulose
  - up of sugar polymers, such as pectin and cellulose
* are part of cells
  - plant cells
* break down, esters dissipate.
* can make plant material difficult to digest.
* characteristic feature to cells of plants, bacteria, fungi, algae and some archaea.
* consist almost entirely of cellulose and glucans, NO chitin.
* consists of cellulose.
* contain cellulose
  - peptidoglycan
* contains cellulose and glucans.Chitin is absent.
* contribute to the functional specialization of cell types.
* follows path of cell membrane.
* form around each group of three nuclei.
* give plant cells their structural strength.
  - lots of cellulose and lignin
  - receptors that detect a specific hormone from the outside
* help support and protect the plant.
* is composed of chitin, a polymer that consists of subunits of a nitrogen-containing sugar
  - made up of chitin and chitosan
  - outermost layer, which is rigid and consists of two layers
  - present only in spores
  - required for fixation of the embryonic axes in Fucus zygotes
  - the rigid structure that surrounds the plant cell
* lacks chitin and instead it is composed of glucan and cellulose.
* occur in Fungi.
* possess peptidoglycan.
* prevent rearrangement of cells and thus asymmetric divisions are an obvious fact.
* provide protection
  - structural rigidity and protection from osmotic lysis
* rigid, multilayered sheet.
* surround plant cells and provide structure.

Different layer
* can have different thicknesses.
* means that water ebbed and flowed over millions of years.
* represent clouds made of gases that condense at different temperatures.

Double layer
* Most double layers consist of layers.
* have special prominence in the field of astrophysics.

Outer layer
* Most outer layers absorb water.
* Some outer layers are made of collagen.
* Some outer layers become ectoderms
  - placentas
  - protect eyes
* heat and expand.
* is made up of pectin or cellulose and inner layer is of cellulose.
* shell, which blocks wind and rain.
* stay cooler than the center and cause uneven kill of disease organisms.

Outermost layer
* contain primary protective structures
* have bumpy texture
* is dentine surrounding an inner pulp cavity.

Ozone layer
* Some ozone layers absorb harmful rays
* Some ozone layers are part of skies
  - stratosphere
* develops, providing protection from UV radiation.

Rock layer
* Some rock layers are made of dense materials
  - contain water
* are bent to extreme degrees, suggesting they folded rapidly while still soft.
* become deformed at the edges of plates.
* develop under very localized conditions.
* dip in the direction of the V made by the contacts when crossing a valley.
* form at right angles to the source of pressure.
* lengthen horizontally.
* shorten horizontally.
* vary in resistance to erosion, producing bluffs, waterfalls, and rapids.

Soft layer
* erode faster than hard layers.
* tend to form slopes and harder layers form cliffs.