The structure and function of plants Flashcards
Name four structures which are found in plant cells but not in animal cells
Chloroplasts, permanent vacuole, cellulose cell wall and plastids like amyloplasts
Describe the structure of the permanent vacuole found in plant cells
It contains cell sap surrounded by a membrane known as the tonoplast membrane
What is the function of chloroplasts?
To carry out photosynthesis
What are plasmodesmata
Cytoplasmic bridges that connect the cytoplasm of neighboring cells
Give two organelles found in animal cells which are not typically found in plant cells
Centrioles and lysosomes
What is the middle lamella?
A layer which is made up of calcium pectate and joins the cell walls of adjacent plant cells together
What are bordered pits?
Unlignified sections of xylem vessels which allow water to move laterally between cells
Describe the structure of starch
Made of amylose and amylopectin, coiled and branched
What is the function of starch?Where is it found?
A store of energy in plant cells. The majority of starch content of plant cells is found inside membrane bound plastids called amyloplasts
Describe the structure of cellulose
Straight chains of beta glucose joined by beta 1,4 glycosidic bonds. Hydrogen bonding between chains strengthens cellulose.
What does the xylem transport and in which direction?
The xylem transports water and minerals up the plant from roots to shoots
What does the phloem transport and in which direction?
Cell sap and sugars from source to sink
What is secondary thickening?
The lateral growth of cambium tissue in plants to increase the thickness of the plant stem and vascular tissue
What are the sclerenchyma fibers?
A type of supportive tissue found in plants made up of cells with lignified cell walls
How can humans use the properties of plant fibers to create materials?
Plant fibers are made of long structural polysaccharide chains. They’re joined and strengthened by many hydrogen bonds which make the fibers tough. An example is cotton
Describe the structure and function of the vascular system in the stem of dicotyledons
Vascular bundles organised around a central pith. Xylem on the inside of the bundle to provide support and flexibility, phloem on the outside. Cambium is found between the two.
Relate the structure of the xylem to its function
-Long columns made of dead tissue to transport water
-Contain bordered pits, allowing the sideways movement of water between the vessels.
-Walls impregnated with lignin, providing structural support
Define translocation
The movement of organic compounds in the phloem, from sources to sinks
Summarize the mass-flow hypothesis of translocation
-Sugar loaded into sieve tubes via active transport
-Lowers water potential causing water to move in from the xylem
-Hydrostatic pressure causes sugars to move towards the sink
Give evidence for the mass-flow hypothesis
● Sap is released when the stem is cut: must be pressure in phloem
● Sap exuding from the stylet (mouthpart) of an aphid inserted into sieve
tubes provides evidence that sugars are carried in the phloem
● There is a higher sucrose concentration in the leaves than the roots
● Autoradiographs produced using carbon dioxide labelled with
radioactive carbon provide evidence for translocation in the phloem
What is the role of Mg2+ (magnesium ions) in plants?
It’s used to produce chlorophyll
What is the role of Ca2+ in plants?
Calcium ions
It’s used to strengthen cell walls in plants
What is the role of nitrate ions in plants?
They are used in the synthesis of amino acids, which are then used to produce proteins
What are the conditions required for bacterial growth?
Sufficient nutrients, an appropriate t°, high moisture levels, high oxygen levels for aerobic bacteria, a well regulated pH
