Topic 4 - Specific organelles of the plant cell

Question 1

Plant specifications

Answer 1

1. Cell wall
2. Non-living cells are part of the body
3. Tiny connections between cells (plasmodesmata) - all cells interconnected
4. Plastids
5. Vacuoles
6. Inclusions

Question 2

Cell size

Answer 2

Micrometer (bacteria) 
↓
Millimeter (nettle hair) 
↓
centimeter (hemp fibers)

Question 3

Cellular compartments

Answer 3

Surrounded with a double phospholipid membrane, differences in function, interaction

Question 4

Cell membranes

Answer 4

Function: separation and transport

Double phospholipid layer
Unit membrane hypothesis → fluid mosaic membrane
Plasma membrane (plasmalemma), tonoplast (vacuoles)

Question 5

Function of membrane proteins

Answer 5

Receptor proteins
Channel proteins
Carrier protein
Transport proteins
Filaments of cytoskeleton
pH regulation (vacuoles) 
Excretion (dictyosome)

Question 6

The cytoplasm

Answer 6

Cytosol and cytoskeleton

Question 7

Cytosol

Answer 7

o	Soluble proteins
o	RNA
o	Water
o	Ions
o	Caarbohydrates
o	Fatty acids

Question 8

Cytoskeleton

Answer 8

Spiral protein filaments
Mechanical resistance, migration of cell organelles
Play role in cell

Question 9

Plant specific organelles

Answer 9

The vacuole system
Plastids
The cell wall 
Incrustations
Adcrustations
Plasmodesmata

Question 10

The vacuole system

Answer 10

A Chamber bounded with tonoplast membrane storing solid or fluid compounds and gases

Minor importance in animal cells

Question 11

Provacuole

Answer 11

Vesicles or ER and dictyosomes

Question 12

Central vacuole

Answer 12

Three provacuoles fused into a larger one

Question 13

Major functions of the vacuole system

Answer 13

Storage (isolating materials)
Cell lysis
Maintaining hydrostatic pressure (tugor) and pH
Dispersal 
Protection

Question 14

Types of vacuoles

Answer 14

Lysosomes
Vegetative (storage) vacuoles
Inclusions
Crystals

Question 15

Lysosomes (vacuole)

Answer 15

Thick membrane

Hyrdolytic enzymes in the middle - autophage

Question 16

Vegetative (storage) vacuoles

Answer 16

Diluted water solution, mildly acidic pH 5-6
Ions (e.g. high salt habitats)
By-products (important products for plant life: essenctial oils, paints, flavours)
Waste products (e.g.: glycosides, alkaloids)
Nutrient storage (protein, carbohydrates)

Question 17

Inclusions

Answer 17

o Non constant, but not essential substances
o No metabolic activity, no membranes
o Protein inclusions: in pulse grains or aleurone layer, globoid or chrystalloid forms homogeneous/heterogeneous
o Carbohydrate inclusions: mainly starch
o Oil inclusions: small droplets of oil in the cytoplasm

Question 18

Crystals

Answer 18

o Accumulation of inorganic compounds
o Oxalates, carbonates, silicates
o Digestion problems, irritation

Question 19

Plastids

Answer 19

Assimilation, synthesizing metabolic processes, storage functions
Double phospholipid layer, chloroplast DNA
Coloured plastids: chloro- and chromoplastids
Colourless plastids: leucoplastids
Originated from prokaryotes

Question 20

Development of plastids

Answer 20

Plastid initial (meristematic cell) → proplastid

Etioplastid: in cotyledons and plants have not been exposed to sunlight

Light → chloroplastid, synthesis of membrane proteins and pigments

Question 21

Types of plastids

Answer 21

Leucoplastid
Chromoplastids
Chloroplastids

Question 22

Leucoplastid

Answer 22

Colourless plastids in organs not exposed to sunlight

Storage function

The plant uses stored nutrients and plastids can turn into green ones (potato)

Globular or fusiform shape

Question 23

Types of leucoplastids

Answer 23

Amiloplastids - starch
Elaioplastids - oil, fatty acids
Proteinoplastids - protein

Question 24

Amiloplastids

Answer 24

Starch

In ground tissues, roots, modified stems, endosperm of seeds
Chrystalline center (hilum) → amorphous and crystalline regions
Simple and compound starch

Question 25

Elaioplastids

Answer 25

Oil, fatty acids Stored nutrients in different organs Essential for germination Drying (linseed, poppy), semi-drying (sunflower) and non-drying (castor bean) oils

Question 26

Proteinoplastids

Answer 26

Protein Simple or compound In modified stems, seeds

Question 27

Chromoplastids

Answer 27

Originated from proplastids or amiloplastids or chloroplastids (ripening, ageing leaves) Less developed inner membranes Carotenoid pigments: carotene, xanthophylls Globular, fibrillary or crystalline forms In flowers, fruits, leaves, roots Pollination, dispersal

Question 28

Chloroplastids

Answer 28

Thylakodis | Stroma

Question 29

Structure and function of thylakodis

Answer 29

Outer membrane similar to cell membrane Photosystems: integral proteins and pigments Electron transport chain: proteins ATP and NADPH production photosynthesis (light dependent reactions)

Question 30

Compounds and functions of stroma

Answer 30

RuBisCO enzyme (protein complex) Photosynthesis (light independent reaction) – production of glucose and intermediate products

Question 31

Plastids of C3 and C4 plants

Answer 31

For C4 plants mesophyll cells has a granum structure, but it's absent form the bundle-sheath cells

Question 32

the cell wall

Answer 32

Similar in fungi cell but with different composition ``` Importance in everyday life Woods Fibers Cooking quality Nutrients Cell wall proteins - hay fever ```

Question 33

Major functions of the cell wall

Answer 33

Protection (environmental stress, pathogens, water loss) Gives a definite shape Enables transport information to the exterior Helps in osmotic-regulation, prevents water loss Transport processes Ion exchange, mineral uptake (root hairs)

Question 34

Skeletal substances in the cell wall

Answer 34

Cellulose 1,4 linked ß-D-glucose chain Synthesised by the rosette enzyme of the plasma membrane Primary cell wall Web of microfibrils + auxin → loosened structure, formation of new fibrils → increasing cell wall surface Secondary cell wall New transverse layers of cellulose fibrils (increased strength) Cellulase enzymes → decomposition of cell wall (secretory ducts, transport vessels)

Question 35

Matrix substances

Answer 35

Pectins (soluble fiber) – linear chain of galacturonic acid polymers: high proportion in fruits and storage organs Hemicellulose (glucose chain + oligosaccharides): cross-link between pectins and cellulose (e.g. arabinoxylan) Proteins Soluble (hydrolitic enzymes, peroxidases) Insoluble (= extensins) – web-like structure

Question 36

Incrustations

Answer 36

Lignin (wood) Suberin (cork) Pigments Mucilage - storage of water, gelling effect Inorganic compounds - in plant hairs → irritation

Question 37

Lignin

Answer 37

Phenolic polymers consists of Coumaryl alcohol Coniferyl alcohol Sinapyl alcohol Mainly in the secondary wall (lignification) Increase rigidity Decrease digestibility

Question 38

Suberin

Answer 38

Polymers of aromatic and aliphatic compounds Waterproof layer, decreasing evaporation Decreasing digestibility

Question 39

Adcrustations

Answer 39

On cell wall surface Wax, cutie Water insulators, decreasing evaporation

Question 40

Plasmodesmata

Answer 40

Channels traverse the cell walls - smooth ER tubes and protein filaments Direct transport between cells Large number in young cells, later decreasing abundance

Question 41

The secondary wall

Answer 41

After the end of cell growth Generally in mature cells with no cytoplasm (e.g.: fibers) Increasing amount of incrustations decreasing digestibility

Question 42

Outer (centrifugal) thickening

Answer 42

In case of spores and pollens Spikes, grains, appendages

Question 43

Inner (centripetal) thickening

Answer 43

Strengthening, protection (e.g.: transport tissues) Total – complete cell wall (sclerenchyma) Local – some part of a cell wall (e.g.: tracheids) Partial – some of the cell wall (collenchyma) General – whole cell wall except plasmodesmata