Plants Lesson 4 Flashcards
(63 cards)
What are plant cell walls made of?
Cellulose
Cell walls
Outside the cell membrane and has a set of functions to stabilize the plant.
Cellulose
Polysaccharide of glucose units. Made by the membrane. Most common organic polymer.
Cell wall increasing in size
Cellulose microfibril (made of parallel cellulose molecules, connected by a hydrogen bond), then 36 chains of these can make a microfibril, then cellulose fibril, then they are laid down in sheets in all different directions to make a cell wall.
Plant cell walls
Extracellular—outside of membrane.
2 kinds:
Primary wall—thin, in all cells
Secondary wall—thicker, in some cells (strength) and only in some plants.
Functions of plant cell wall
- determines & maintains cell shape.
- provides support and mechanical strength (allows plants to get tall, hold out thin leaves to obtain light).
- prevents the cell membrane from bursting and calapsing (i.e., resists water pressure).
- controls the rate and direction of cell growth and regulates cell volume.
- ultimately responsible for the plant architectural design (shape).
- physical barrier to: (a) pathogens and (b) water in suberized (waxy) cells. However, remember that the wall is very porous and allows the free passage of small molecules.
- carbohydrate storage — the components of the wall can be reused in other metabolic processes (especially in seeds).
Two many functions of waxy cells in the cell wall?
Allow fluids to flow through the plant. Prevent fluid from flowing through the walls.
3 Kinds of polysaccharides (plant cell wall compositions)?
- Cellulose: Polymer (chain) of up to 25,000 glucose molecules and ~36 chains bond to make microfibril. Gives the cell its strength.
- Cross-linking glycans (hemicellulose)—bond with
cellulose. - Pectin—jellylike; glue. A polysaccharide.
The two things that hold the cellulose together?
Pectin and hemicellulose
Middle Lamella
Material between cells. Made of pectic substances. Holds the cells together.
Plasmodesmata
Connection between cells that cytoplasm flows through.
Which cell wall is made first?
The primary then the secondary because both is made by the cell membrane.
The 3 tissue systems in vascular plants
Dermal, Vascular, Ground
Dermal tissue
Single layer; secretes cuticle (waxy). On the outside. The epidermis.
Vascular tissue
Xylem & phloem; support & supply. Moves fluids around. Moves fluid around.
Types: Tracheids & vessel elements, and Sieve elements
Ground Tissue
Tissue other than dermal or vascular; bulk of young plant; fills space between dermal & vascular tissues;
mostly parenchyma; storage, photosynthesis, support.
Types: Parenchyma, Collenchyma, Sclerenchyma
How many cell types in plants?
6
Epidermal cells
Outermost cells. Single layer (single sheet) covering leaves, stems & roots of non-woody plants or plant
parts. If woody this gets replaced. All plants have them. Forms the epidermis of shoots.
Epidermal cells functions
Waterproofing. Protection from pathogens: viruses, bacteria, fungi. Other specialized roles: Hairs (trichomes), make nectary, Guard cells: gas exchange (open and close).
Cuticle
Formed by the epidermal cells, outermost part is wax. Cuticle protects against: Water loss, Pathogens,
Ultraviolet (UV) radiation, because of the wax.
Wax on chamomile petal does what?
Makes it white because of how it reflects the light.
Pitcher plant
Eats insects. They get trapped in there because they fall down it because the way the wax is arranged because the insects can’t climb back up. When it falls down it gets digested because of acidic fluid.
Secretory trichomes
Means hair. They have smells from the oils in the Epidermal cells. Or has fluid to make you sting.
Cannibis
Secretory trichomes that have Epidermal cells filled with THC.
