Lecture 14: Flashcards
describe micro level of F&V structure
individual cells w/ specific functions (Pro, CHO, fat synth)
descrie macro level of F&V structure
collective functions, formation of large group of similar cells
describe cell wall
- outermost layer of cell
- comp of cellulose and other polymeric materials
- main functions: structural support and containing all cell components
describe middle lamella
- cell membrane more rich in pectic substances
- pliable
- has role in holding and binding cell components
describe plasmaderma
- communicates w/ adjoining cells
- semi permeable membrane w/ selective permeability
- imp in plant water relationship (osmosis)
- responsible for turgidity of plant cell
describe vacuole
- fluid reservoir of cell
- contains soultes
- surrounded by semi-permeable membrane called tonoplast
- has a role in cell turgidity
describe cytoplasm
- fluid matrix
- where all major metabolic activities take place
- functions controlled by nucleus and coordinated through organells
describe endoplasmic reticulum
- responsible for synthesis and transport b/w nucleus and cytoplasm
- implicated in protein synthesis
describe the golgi complex
- implicated in cell wall synthesis
- modification and transporation of proteins and fats built in the ER
describe nucleus
- overall control of all metabolic activities, esp protein synthesis and DNA/RNA transformation
- control center
what does the ribosome contain?
RNA rich organnel responsible for protein synthesis
what are 3 types of plastids?
chloroplast (photosynthesis)
chromoplast (color)
amyloplast (starch)
what are 3 systems in plant tissue at a macro level?
- dermal system
- ground system
- vascular system
describe the dermal system
- protective tissue belonging to outer surface of produce
- offers protection from: loss of H2O, invasion of pathogens, mechanical injuries, temp stress, volatilization of aromatic compounds, texture loss
- facilitates gas exchange (O2 in; CO2 out)
what are types of dermal cells?
- cuticle (cutin or wax)
- epidermis
- corky tissue
- stomata
- lenticels
- peel
describe cutin
- polymerized pdt of hydroxycarboxylic acids and their esters
describe wax (dermal cell)
ester of aliphatic wax alcohols and their corresponding FAs
fruits has ___ (more/less) wax/cutin than veg
more
leafy veg have ____ (more/less) wx/cutin than root veg
more
describe epidermis
- cells along outermost layer of the organ
- fits together compactly
- cell walls have lipid like materials
describe the cuticle or cuticular membrane
- extracellular water impermeable surface layer
- cutinization dictates functional properties
- consists of cutin or waves
describe corky tissue
- surface of underground storage organs
- contains lipid-like material called suberin
- found in serial fruits (eg. apples)
describe stomata
- small pores in epidermal layer
- surrounded by specialized guard cells
- serve as minute valves for gas exchange
describe lenticels
pores in corky tissues
describe peel
modification of outer protective cell
what is the role of collenchyma and sclerenchyma cells?
supports tissues
provides mechanical support to the cell
describe collenchyma
- series of separate longitudinal strands
- cells elongated parallel to long axis
- unevenly thickened
- cell walls rich in petin and hemicelluloses
- have unusual pliability
what are functions of ground system?
- major metabolic activities
- chief edible portion of produce (~80% of plant tissue)
- provides mechanical support for the tissue
describe parenchyma cells
- most common ground tissue
- has mostly undifferentiated cells
- has a large vacuole
describe schlerenchyma tissue
- have uniform thickened walls
- 60-80% cellulose
- normally lignified
- low tensile strength
- greater rigidity and hardness
- provides better impact resistance
what are 2 types of sclerenchyma cells?
- fibers:
- long and pointed
- unchanged after cooking
- nutrition importance - sclereids
- not long or pointed
- abundant in hard structures
- occurs as scattered clusters in parenchyma tissue
- responsible for grittyness or grainyness
what are the 6 diff types of cells in plant tissue?
- phloem
- parenchyma
- sclerenchyma
- collenchyma
- xylem
- protective
describe the vascular system
- transport tissues (eg. transport of H2O and minerals)
- highly specialized
what is the role of xylem?
conducts H2O and minerals
what is the role of phloem?
conducts organic pdts of metabolism and photosynthesis
what contributes to texture?
- physical properties and structual organization of tissue constituents
- relative proportions and distribution of types of tissues
- cell wall, cellulose, hemicellulose…
firmness results from what?
- turgidity of thin walled parenchyma tissue
or 2. high proportion of thick walled mechanical tissue
crispiness results from what?
- turgidity of the cells (extent to which the cells are burst open by teeth during mastication)
define turgidity
balance between elastic nature of cell wall and the hydrostatic pressure of the cell (resulting from osmotic process within)
fibrousness of stringiness results from what?
presence of bundles of mechanical tissues that resist shearing forces applied by the teeth
grittiness results from what?
by the presence of small particles or clusters of cells with thick and rigid walls (sclereids)
what does turgidity depend on?
- cell wall strength to counter hydrostatic pressure within the cell
- hydrostatic water pressure is moderated by the osmotic process (composition). Thus turgidity is influenced by structure and composition of the produce
turgidity is synnonymous with what?
freshness
define osmosis
selective movement of active components like h2o across a semi permeable membrane
define a semi permeable membrane
allows free passage of solvent molecules but retains solutes
what are the most imp membranes controlling osmosis?
tonoplast and plasmalemma
____ plays a key role in making produce turgid
osmosis
describe the osmosis phenomenon
- one side of semi permeable membrane has high kinetic energy while the other side has low kinetic energy
- water/active component must move from higher to lower kinetic energy region for equilibrium
describe how h2o moves into a plant cell
- h2o is sucked in from roots
- h2o moves into cell and increases hydrostatic pressure (HP) of the cell
- cell inflates
- pressure is exerted against cell wall
- turgidity increases but is limited by turgor pressure
what is HP
hydrostatic pressure
increased when h2o moves into cell
what is TP
turgor pressure
what limits the turgidity of a cell?
turgor pressure
what is OP
osmotic pressure
when applied, causes influx/efflux of water
weak cells rupture due to what?
high osmotic inflation
normal cells have a balance between what?
HP and TP
strong cells have cell wall strength greater than ____
this allows what?
HP
allows more resistance to moisture loss
describe the transpiration process
results in
- loss of h2o from the cell
- loss in HP
- incr conc of solutes
- incr osmotic potential
- causes pressure difference (OP - TP)
- establishes dynamic equilibrium
OP - TP = ?
suction pressure (SP)
describe the post harvest behaviour of a cell
- no water influx
- HP continuously goes down
- shrivelling when the cell wall collapses
- turgidity or freshness is lost forever
how is an example of how structure influences textural properties?
course of ripening
eg. hard green banana becomes soft ripe banana
what is instron universal testing machine?
texture measuring instrument
what is Magnes Taylor Puncture Probe
a fruit pressure tester
used to measure firmness of produce
hardness = ?
max force / max deformation
stiffness = ?
(force/cross sectional A) / (deformation/initial length)
firmness = ?
slope of linear section of force x deformation curve
