plant cells and tissues

Question 1

How is a palisade cell specialised to carry out its function?

Answer 1

-many chloroplasts to carry out efficient photosynthesis
-have a large vacuole so chloroplasts are positioned nearer to the periphery of the cells, reducing the diffusion distance of CO2.
-contain cytoskeleton threads and motor proteins to move the chloroplasts nearer to the surface of the leaf when sunlight intensity is low but further down when sunlight intensity is high
-long and cylindrical so can pack closely together but with little airspace between them for air to circulate

Question 2

How is a root cell specialised to do its job?

Answer 2

-hair-like projections increase the SA for absorption of water and mineral ions e.g. nitrates from the soil (that are actively transported)
-have special carrier proteins in the plasma membrane to actively transport the mineral ions in (need cells to produce ATP for this)

Question 3

How does a guard cell work?

Answer 3

light energy used to produce ATP which actively transports potassium ions, from the surrounding epidermal cells into the guard cells, lowering their water potential so water enters via osmosis
cells swell and become turgid, opening up the stoma gaseous exchange occurs
AND THE OPPOSITE when the water potential is higher in the guard cells than the surrounding epidermal cells

Question 4

How is a guard cell specialised to carry out its function?

Answer 4

-the cellulose cell wall is more flexible at the tips of the cell and it is more rigid where it is thicker, so tips bulge and stoma enlarges when the cell swells as water enters via osmosis

Question 5

Do guard cells contain chloroplasts?

Answer 5

Yes but the do not carry out photosynthesis as they do not have the enzymes needed for the second part of the process

Question 6

Epidermal tissue

Answer 6

-a single layer of closely packed, flattened cells
-form a protective covering over leaves, stems and roots
-some have a waxy cuticle layer which reduces water loss (especially for plants in dry areas)
-stomata are present in the epidermis - allow for gaseous exchange

Question 7

Xylem tissue

Answer 7

-a type of vascular tissue responsible for the transport of water and mineral ions through plants
-composed of vessel elements - elongated dead cells
-walls strengthened by lignin
for structural support and waterproof

Question 8

Phloem tissue

Answer 8

-a vascular tissue responsible for the transport of organic nutrients like sucrose from leaves and stems where it is made by photosynthesis to all parts of the plant where it is needed
-translocation
-composed of sieve tube cells separated by perforated walls called sieve plates