4.4 Flashcards
list the three basic principle plants use to build tall structures:
- produce strong cell walls out of cellulose (polymer made form sugar molecules)
- build columns and tubes from specialised cells
- stiffen some of these specialied cells with another polymer called lignin
what is cellulose?
makes up the thin walls of plants
what is cellulose made of?
lots of B-glucose molecules join together in a condensation reaction to make a glucose chain also know as cellulose
what are microfibrils?
when hydrogen bonds form between the -OH groups of neighbouring cellulose chains, microfibrils are formed
what are hemicelluloses and pectins?
the glue that holds microfibrils is composed of hemicellulose and pectins
what is plasmodesmata?
narrow fluid channels that makes the cytoplasm of one cell continuous well the cytoplam of the next
what is a pit?
at some places the cell wall become thin becaus the first layer of cellulose is deposited, this is calle a pit
what is a xylem vessel and what does it do?
these form tubes for transport of water and minerals, and their stiffened cell walls help to support the plant
what are sclerenchyma fibres and what do they do?
columns of the cells with their stiffened cell walls also provide support for the plant
what are phloem sieve tube cels and what do they do?
these form long tubes for transport of organic solutes, such as sugars and amino acids (they do not help to support the plant)
what is a vascular bundle?
the colection of xylem vessels, sclerenchyma fibres and phloem sieve tubes on the inside if the plant
what is autolysis?
when the cell organelles,cytoplasm and cell surface membrane are broken down by the action of enzymes and are lost , leaving dead empty cells taht form a tube
what is transpiration?
when water leaves the plant by evaporation
what is a transpiration stream?
the continuous stream of water passing into and out of the plant
what is the cohesion theory?
water molucule have cohesive tension between them and pull each other up the plant
what is translocation?
the movement of organic molecules within the phloem tubes
what is a companion cell?
cells next to the sieve tubes that maintain it (they still have nucleus, mitochondria, ribosomes and rough endoplasmic rectillium)
