characteristics of living organisms Flashcards
fungi
body organised into mycelium made from hyphae (contain many nuclei
chitin cell walls
saprotrophic- feed by extracellular excretion of digestive enzymes onto food material
carbohydrates as glycogen
virus examples
tobacco mosaic virus- discolours leaves, prevent formation of chloroplasts
HIV- causes AIDs
what are enzymes
Biological catalysts in metabolic reactions.
What is the function of the waxy cuticle?
To stop water escaping
The waxy cuticle helps in reducing water loss from the plant surface.
What is the role of the upper epidermis in a leaf?
Transparent to allow light through to the lower levels
The upper epidermis protects the leaf while facilitating light penetration for photosynthesis.
What type of cells are found in the mesophyll layer and what are their characteristics?
Palisade cells and spongy cells
Palisade cells are denser and contain many chloroplasts, while spongy cells are arranged loosely for gas exchange.
What is the function of spongy cells in the mesophyll layer?
Arranged loosely to allow gas exchange
Spongy cells help in the diffusion of gases such as oxygen and carbon dioxide.
What structures are found in the lower epidermis?
Stomata and guard cells
Stomata facilitate gas exchange, while guard cells regulate their opening and closing.
Fill in the blank: The palisade cells in the mesophyll layer are denser than the _______ below.
layer below
This indicates the arrangement and density of cells in the mesophyll.
adaptations for gas exchange- plant
stomata, guard cells, thickness, broadness, airt spaces
stomata
with guard cells to open/ close them = allows O2 to enter and CO2 to exit. Close when supply of water dries up from roots, stops plant from drying out. Allow transpiration. Close in the dark.
guard cells
increase in volume to open the stomata and decrease in volume to close it. When lots of water is available, the cell fills and opens the stomata
thin
so gases travel a small distance to cells they’re needed in. Allows light to pass through to reach all chlorophyll.
broad
create large surface area for diffusion and light absorption.
air spaces
allow gases like CO2 to move easily between cells. Increases area for gas exchange.
mineral ions required for a plant
magnesium (small amounts): chlorophyll production
deficiency: leaves turn yellow
nitrate: production of amino acids
deficiency: stunted growth, older leaves turn yellow
potassium: help enzymes neede for P and R
deficiency: poor flower and fruit growth, disclouored leaves
phosphates: making DNA and cell membranes, respiration and growth
deifciency: poor root growth, older leaves turn purple
alveoli adaptations for gas exchange
thin cell walls: one cell thick, shorter diffusion distance
folded: increase surface area
large network of capillaries: increases conc gradient between air and blood
small organisms
can use diffusion to trsnaport molecules in their bodies as large SA: V ratio and low metabolic demands
adaptations of phloem
transports sucrose and amino acids to other parts of plants (transloaction)
- found in roots, stems and leaves
- elongated cells with holes in cell walls (sieve plates)
- organelles from cells removed to transport sap. many mitochondria in companion cells provide them with energy required
- food can be moved in both directions
adaptations of xylem
water and mineral ions travels up from roots into leaves
- chemical lignin deposited which causes cells to die- strengthens plant to withstand pressure of wateer movement
- cells become hollow and join ends to form a continous tube
- water molecules attarcted to each other by hydrogen bonding
- water evaporates with transpiration
- contain bordered pits which are holes allowing mineral ions and water to enter in certain areas
