Structure of primary cell wall
- fibrous components of cell wall consist of long strands of cellulose which are bundled into stout, cable like structures
- cable like structures called microfibrils
- microfibrils cross-linked by other polysaccharide filaments
- space between microfibrils is filled with gelatinous polysaccharides such as pectin.
Name the two layers of a plant cell wall
- Primary cell wall
2. Secondary cell wall
Primary cell walls define _____________________.
the shape of the plant cell
Turgid pressure
The force exerted by the incoming water that increases the cell’s volume
Why is turgor pressure especially important in young cells actively growing?
- Young plant cells secrete proteins called expansins into their cell wall.
- Expansins disrupt hydrogen bonds that cross-link the microfibrils in the wall, allowing them to slide past one another.
- Turgor pressure then forces the wall to elongate and expand.
- The result is cell growth
Secondary cell wall structure
Structure depends on the plant cell type and their function.
- In leaves they contain waxes that form waterproof coating
- Cells that support the stem have lots of cellulose
- Cells that form wood contain lignin - helps plant withstand forces of gravity and wind.
The Extracellular Matrix (ECM) function and structure
A fibre composite created by animal cells on the exterior of their cells.
- Structural support is one of the ECMs most important functions
- fibrous component of animal ECM is collagen
Proteoglycans
Consist of protein cores and many large polysaccharides attach to them.
Surrounds collagen and other fibrous components of ECM
Integrins
Membrane proteins that bind to extracellular proteins, including laminins, which in turn bind to other components of the ECM
Epithelium (plural: Epithelia)
A tissue that forms external and internal surfaces forming barriers between different environments
-separates organs to prevent the mixing of solutions from adjacent organs
Indirect intercellular attachments
The extracellular space between adjacent plant cells comprising of a substance that sticks together the cells
In plants: area is called middle lamella, glue is called pectin
In animals: glue is a gelatinous polysaccharide
Tight junctions
A cell-cell attachment composed of specialized proteins in the plasma membrane of adjacent animal cells
Watertight
Looks like quilt stitches
Gap junctions
Connect animal cells together via protein channels. Signals and other substance get passed between these gap junctions
Plasmodesmata
Connects plant cells via membrane channels
At these connections, the plasma membrane and cytoplasm are continuous. A smooth Endoplasmic reticulum passes through.
Symplast
a continuous network of cytoplasm connected by plasmodesmata
Apoplast
Is the region outside the plasma membrane
Consists of: cell wall, middle lamella and air spaces
What is the function of a plants root system?
- Anchors pant in soil
- Absorbs water and ions from the soil
- Conducts water and selected ions to the shoot
- Obtains energy in the form of sugar from the shoot
- Stores material produced in the shoot for later use
How can root system diversity be analysed?
- Morphological diversity among species
- Phenotypic plasticity, or changed in the structure of an individual’s root system in response to the environment
- Modified root that are specialized for unusual functions
What are herbaceous plants?
Seed plants that lack woody tissue
Define perennial root systems
Root systems that live for many years
Modified root examples
- Anchor roots - advantageous roots anchor stems to walls and to other plants
- Prop roots - stabilize the stem
- Pneumatophores - allow gas exchange between roots and atmosphere
What are nodes and internodes?
Nodes = where leaves are attached Internodes = segment between nodes
What are stolons and rhizomes?
Stolones: produce new individuals at nodes above ground
Rhizomes: produce new individuals at nodes underground
Tubers
are storage site for plants, potatoes store carbs
