Topic 4 Flashcards
(47 cards)
List the organelles that are only found in a plant cell?
- cellulose cell wall
- middle lamella
- plasmodesmata
- pit
- amyloplast
- tonoplast, vacuolar membrane
- vacuole
- chloroplast
What is the function of a chloroplast
Site of photosynthesis
What is the function of amyoplasts?
Storage vacuoles containing starch
What is cellulose made of?
Beta glucose monomers joined by 1,4 glycosidic bonds in a condensation reaction
Describe microfibrils
- make up the cell wall
- made of cellulose chains joined by hydrogen bonds between side groups
- arranged at angles, in net shape, for strength
- laid parallel for flexibility
- microfibrils are held together by hemicellulose and calcium pectate (pectins)
Describe plasmodesmata
Narrow cytoplasm filled channels that cross cell walls
What is the difference between a pit and plasmodesmata?
A pit has a thin cell wall, plasmodesmata don’t
Is cellulose a branched molecule/
No
What is secondary thickening?
When lignin is added to the cell wall
What is found in a vascular bundle/
- xylem vessel
- phloem sieve tubes
- sclerenchyma fibres
- cambium - unspecialised stem cells
Describe the xylem structure
- lignified, lignin found in spirals and strings for strength and flexibility, water proofs the cell, secondary strengthening
- have absent cell walls
- have pits, allows lateral movement of water
- hollow, no cytoplasm
What does xylem transport
Water and mineral ions
- via transpiration ONE WAY
Describe autolysis
Cell organelles are broken down by the action of enzymes, leaves dead empty cells that form a tube
Describe the 5 stages of transpiration
- water vapour diffuses out through the stoma down a diffusion gradient
- water evaporates from the surface of cells lining the substomatal cavity, water moves by osmosis across the leaf, from cell to cell
- water replaced by Dan’s of capillary action within the cell walls
- water is drawn out of the xylem
- a continuous column of water is drawn up through the xylem
Define the transpiration stream
Unbroken chain of water molecules
Describe cohesion
- attraction between like molecules
- hydrogen bonds between the water molecules
Describe adhesion
- attraction between unlike molecules
- hydrogen bonds form between water molecules and the OH groups of the cellulose cell wall
Describe cohesion-tension theory
Water is linked by cohesion and is pulled up under tension
Water moves thorugh the xylem tube by ___________.
Mass flow system
Describe the phloem
- comprised of sieve tubes and companion cells
- a sieve tube element is a section of phloem with sieve plats at the end
- is alive
- TWO WAY
The phloem transports ________ via __________
- sucrose and water
- translocation
describe the movement of sucrose in a plant
- sugars are produced at source
- transfer cells actively pump sucrose into phloem against concentration gradient
- water is drawn into phloem via osmosis due to increased solute concentration, increasing hydrostatic pressure
- diffusion- down a conc.gradient by mass transport
- sucrose is then actively unloaded into transfer cell then sink
- water osmoses back into xylem
The plant stem relies on ________, fully ____________ parenchyma cells to maintain its shape and keep it upright
- tightly packed
- turgid
What is the plant stem comprised of?
- parenchyma- provide support
- vascular bundles
- epidermis
- collenchyma tissue- strength
