Topic 4 (4.7 - 4.11) Flashcards
What does the vacuole contain
Cell sap, a fluid mostly made of sugar (and ions) dissolved in water
What is the purpose if the vacuole
To regulate the ions in a cell
To maintain turgor pressure
To separate vascular contents from the cytoplasm
Why does the vacuole need to maintain turgor pressure
It pushes the chloroplasts closer to the cell wall
Helps support the plant cell in an upright condition
Maintains cell stability
How does the vacuole regulate turgor pressure
By regulating the ions in the cell, it can control the water potential of the cell
Increasing the water content in the cell will cause it to become turgid
What is the membrane that surrounds the vacuole called
The tonoplast
What is the purpose of chloroplasts
Photosynthesis
What is the structure of the chloroplast
Contains a double membrane with a small intermembrane space between the two
Contains thylakoids stacked into granum
Contains stroma ( a liquid making up most of the chloroplasts volume)
What are thylakoids
Small interconnected sacks that contain the membranes upon which the light dependent reaction occurs
What are grana
Stacks of thylakoids
What is the stroma
An aqueous fluid in chloroplasts
It makes up the majority of the chloroplasts volume and is responsible for the light independent stage
What are amyloplasts
Small organelles responsible for the synthesis and storage of starch
It is a double bound organelle
What are pits (plant cells(
Gaps in the cell wall where lignification is not complete, allowing water to flow between xylem vessels
What is the middle lamella
A pectin layer that joins (glues) adjacent cells together
What are plasmodesmata
Thin strands of cytoplasm that hold adjacent cells together, allowing substances to be transported between them
What is the xylem
A vessel made from hollow, dead cells that transports miners ions and water from the roots to the leaves
Describe lignification
During the development of the xylem vessel, lignin impregnates the wall of xylem cells
This kills the xylem cells, and causes the end walls and cell contents to decay
This creates a long hollow column of dead cells
Other than killing the xylem cells, what does lignin do
It makes the xylem tube waterproof
It strengthens the wall, and prevents the xylem vessel from collapsing
Why is lignin deposited in a spiral
To provide strength and flexibility.
The spiral shape allows the xylem to stretch and bend as the plant grows
Why does lignification not occur in some parts of the xylem vessels
To create BORDERED PITS, allowing water to pass between adjacent xylem vessels
Why are xylem vessels needed
Without them mineral ions could not be transported around a plant
Mineral ions (e.g magnesium) are needed for the plant to function (making chlorophyll))
Water is needed for photosynthesis
Why is the xylem lumen narrow
It ensures the forces of attraction are able to pull the water up the walls of the xylem
How does water move in the xylem
Via capillary action
Hydrogen bonds form between the water molecules (cohesion)
Hydrogen bonds form between the water molecules and xylem wall (adhesion)
Due to surface tension (and cohesion / adhesion) the water is pulled upwards)
What is the phloem
The vessel responsible for the transport of assimilates (moslty organic materials) in a plant
It transports frim source to sink
What are assimilates
Substances made by plants
What makes up phloem tubes
Sieve tube elements line end to end
There are sieve plates between the sieve tube elements
Each sieve tube element is attached to a conpanion cell
What are sieve tube elements
Cells that contain no nucleus (or other organelles) and very little cytoplasm
They are mostly empty, so that cell sap can move along the phloem vessel
The end of sieve tube elements is perforated (sieve plates) so that cell sap can move between cells
Why does the phloem contain companion cells?
The sieve tube elements do not have mitochondria
The companion cell is abundant in mitochondria for cellular respiration
This produces ATP that can be used for active processes such asa loading assimilates into the phloem
How are companion cells and sieve tube elments connected
Through a plasmodesmata
Why is there a plasmodesmata between the sieve tub elements and companion cells
To allow assimilates to be transported to the companion cells (e.g so glucose can be used in respiration)
What is a vascular bundle
A structure in a plant containing, phloem tubes, xylem vessels and schlerenchyma
Where is the xylem in the vascular bundle
On the inside
Where is the phloem in the vascular bundle
On the outside
Where is the sclerenchyma in the vascular bundle
Behind the phloem
What is the purpose of sclerenchyma
To provide additional stupport and structure
Why do leaves only abosrb blue - violet and red light
Absorbing all light would cause the plant to overheat
Enzymes required for photosynthesis would dneature and the cell wall would melt
Why are phosphorous ion needed in plants
To make ADP and ATP
Why are magnesium (mg2+) ions needed in plants
To produce chlorophyll
Why are nitrate ions needed in plants
To make DNA and amino acids
Why are ca2+ ions needed in plants
Too form a metal pectate for the middle lamela
What is a pectate
A chelators that causes metal ions to bond together
