Plant Cellular Organelles and Structures

Question 1

Middle Lamella

Answer 1

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

Question 2

Pectin

Answer 2

A complex set of polysaccharides… is used in the middle lamella, also used in jams; works like glue

Question 3

Cell Walls

Answer 3

Made of cellulose; provide structure, rigidity, and protection

Question 4

Plasmalemma

Answer 4

• the plasma membrane
• semi-permeable
• made up of a phospholipid bilayer of cells
• forms a continuum throughout the plant thanks to the plasmodesmata

Question 5

Plasmodesmata

Answer 5

• occur through the cell wall & and allow a continuum of cytoplasm and membrane material from one cell to another

Question 6

Symplastic Pathway

Answer 6

• continuum of living materials

- minerals and metabolites can be transported throughout the plant without ever leaving the cytoplasm

Question 7

Apoplastic Pathway

Answer 7

• 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

Question 8

What are the three major components of the Plasmolemma?

Answer 8

1) Lipids 40%
2) Proteins 40%
3) Carbohydrates 20%

Question 9

What are the different ways phospholipids can move about the membrane?

Answer 9

• flexion
• rotation
• lateral diffusion
• bobbing
• flipping

Question 10

What are the different lipids found in the plasmalemma called?

Answer 10

• phospholipids (most common)
• sterols
• glycolipids

Question 11

What are the different sterols found in the membrane?

Answer 11

• Sitosterol
• Camposterol
• Cholesterol
• Stigmasterol

Question 12

What are the function of proteins in the cell membrane?

Answer 12

• peripheral and integral proteins

- most are enzymes that transport metabolites across the membrane

Question 13

How do plants have chilling resistance?

Answer 13

• 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

Question 14

How do cold temperatures hurt plants?

Answer 14

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.

Question 15

Nucleus

Answer 15

• 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

Question 16

Endoplasmic Reticulum

Answer 16

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

Question 17

Dictyosomes (Golgi apparatus)

Answer 17

• 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

Question 18

Mitochondria

Answer 18

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

Question 19

Vacuoles

Answer 19

• 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

Question 20

Proplastids

Answer 20

• precursors of all other plastids

- small, undifferentiated plastids, later specialize into other plastids depending on cues/triggers

Question 21

Amylopoast

Answer 21

• contain starch granules
• unpigmented
• common in storage organs, like potato
• in root tip cells; involved in gravity perception

Question 22

Leucoplasts

Answer 22

• 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

Question 23

Chromoplasts

Answer 23

• synthesize and accumulate carotenoid and xanthophyll pigments
• carotenoid = red, orange
• xanthophyll = yellow
• found in ripe tomatoes, carrots, red peppers

Question 24

Etioplasts

Answer 24

• plastids where development from proplastids to chloroplasts has been arrested by the absence of light (or very little light)
• not an intermediate stage

Question 25

Chloroplasts

Answer 25

• responsible for energy capture and photosynthesis
• green due to chlorophyll pigment
• bounded by double unit membrane