Plant Cellular Organelles and Structures Flashcards
Middle Lamella
non-living area between adjacent cells, filled with Ca and Mg pectates which cement adjacent cells together
- important to fruit ripening
- during ripening enzymes called pectinases are secreted into this area
Pectin
A complex set of polysaccharides… is used in the middle lamella, also used in jams; works like glue
Cell Walls
Made of cellulose; provide structure, rigidity, and protection
Plasmalemma
- the plasma membrane
- semi-permeable
- made up of a phospholipid bilayer of cells
- forms a continuum throughout the plant thanks to the plasmodesmata
Plasmodesmata
- occur through the cell wall & and allow a continuum of cytoplasm and membrane material from one cell to another
Symplastic Pathway
- continuum of living materials
- minerals and metabolites can be transported throughout the plant without ever leaving the cytoplasm
Apoplastic Pathway
- non-living portions of plant tissue called the apoplast
- e.g. middle lamella and dead xylem vessels
- transport water and materials easily dissolved in water
What are the three major components of the Plasmolemma?
1) Lipids 40%
2) Proteins 40%
3) Carbohydrates 20%
What are the different ways phospholipids can move about the membrane?
- flexion
- rotation
- lateral diffusion
- bobbing
- flipping
What are the different lipids found in the plasmalemma called?
- phospholipids (most common)
- sterols
- glycolipids
What are the different sterols found in the membrane?
- Sitosterol
- Camposterol
- Cholesterol
- Stigmasterol
What are the function of proteins in the cell membrane?
- peripheral and integral proteins
- most are enzymes that transport metabolites across the membrane
How do plants have chilling resistance?
- by having a higher proportion of unsaturated phospholipids in their membrane
- this maintains membrane fluidity, because the kinks in the hydrocarbon tails (caused by Carbon double bonds) prevent the phospholipids from packing closely together and gelling
How do cold temperatures hurt plants?
It affects membrane fluidity by moving the plant cells from a liquid crystalline state to a solid gel phase state, which impedes membrane permeability and can cause the cells to lose their contents. The colder temperatures also slow down enzymes and metabolic pathways, or alter tertiary/quaternary structure of these enzymes which disallows appropriate substrates from binding to active sites.
Nucleus
- surrounded by porous, double membrane called the nuclear envelope
- contains the DNA (chromosomes)
- has one or more nucleoli made up of protein and nucleic acids involved in rRNA synthesis
Endoplasmic Reticulum
Smooth ER & Rough ER, rough ER studded with ribosomes
- synthesizing, processing, and sorting proteins targeted to membranes, vacuoles, or the secretory pathway
- also synthesizes lipids
- critical role in regulating cytosolic concentrations of calcium; influences many other cellular activities
Dictyosomes (Golgi apparatus)
- gives rise to vesicles
- involved in assembling complex carbohydrates for the cell wall (cellulose)
- synthesizing carbohydrate side chains for glycoproteins in the membrane, cell wall and vacuole
Mitochondria
POWER HOUSE OF THE CELL
- surrounded by double unit membrane
- likely an endosymbiont
- centers of respiration, responsible for converting carbohydrates into ATP to support metabolic activity
Vacuoles
- enclosed by a membrane called the tonoplast; single unit membrane
- large central vacuole usually more than 30% of plant cell volume
- storage; water, pigments, acids, proteins, sugars
- digestion; contains proteases, nucleases, glycosidases, and lipases
- pH and ionic homeostasis
Defense against microbial pathogens and herbivory:
- sequestration of toxic compounds
- cell-wall degrading enzymes, such as chitinase and glucanase
- latexes, wound-clogging emulsions of hydrophobic polymers that possess insecticidal and fungicidal properties; also serve as antiherbivory agents
Proplastids
- precursors of all other plastids
- small, undifferentiated plastids, later specialize into other plastids depending on cues/triggers
Amylopoast
- contain starch granules
- unpigmented
- common in storage organs, like potato
- in root tip cells; involved in gravity perception
Leucoplasts
- colorless plastids, involved in synthesis of monoterpenes (volatile compounds found in essential oils)
- found in secretory gland cells associated with leaf and stem trichomes (hairs), also found in citrus peels
Chromoplasts
- synthesize and accumulate carotenoid and xanthophyll pigments
- carotenoid = red, orange
- xanthophyll = yellow
- found in ripe tomatoes, carrots, red peppers
Etioplasts
- plastids where development from proplastids to chloroplasts has been arrested by the absence of light (or very little light)
- not an intermediate stage
Chloroplasts
- responsible for energy capture and photosynthesis
- green due to chlorophyll pigment
- bounded by double unit membrane
