Bioenergetics test Year 10 Flashcards
Parts of the leaf
- palisade mesophyll
- epidermal tissue
- spongy mesophyll
- guard cells
- stoma/ stomata
- ploem
- xylem
Features of palisade mesophyll
- cell shape allows them to be tightly packed
- has lots of chloroplasts to maximise amount of light energy that can be captured in photosynthesis
Features of epidermal tissue
- single outer layer of flattened cells that protect the leaf
- waterproof waxy layer on upper epidermis - prevents water loss
- lower epidermis contains stomata and guard cells
Features of spongy mesophyll
- loosely packed
- large surface area
- lots of air gaps
- maximises rate of gas exchange for photosynthesis
- allows gases to diffuse easily through leaf to and from stomata
features of guard cells
open and close stomata
What are stomata/ stoma
pores in the leaf that gases can diffuse through
(turgid = close and flaccid = open)
What is meristem tissue?
- made of unspecialised cells that can divide repeatedly to make other cells
- new cells can differentiate into other types of plant cell, allowing for the plant to grow
What do phloem cells do?
transport sugars made in leaves to the rest of the plant
features of phloem
- elongated cells to transport sugars over long distances
- companion cells have many mitochondria for active transport
- end walls have pores to allow sugar solution to pass from cell to cell easily
What do xylem cells do?
transport water and mineral ions through the plant
Features of xylem cells
- hollow tubes (lumen) with no end walls to allow water and minerals to flow easily
- lignin in walls to provide strength and support
Describe the transport of water and minerals
- root hair cells take up water from the soil by osmosis
- takes up minerals by activie transport
- xylem carries mineral and water solution from roots to stem to leaves
- flow of water up through the plant is called the transpiration stream
- water is lost from leaves by evaporation and diffusion (transpiration)
- loss of water from leaf pulls up more water through xylem
Describe the proccess of transporting dissolved food
- movement of dissolved food molecules through phloem is called translocation
1. food molecules are produced in leaves by photosynthesis
2. food transported in phloem to the rest of the plant as dissolved sugars
3. sugar may be used by cells immediately or converted into starch for storage
4. food molecules can be transported upwards towards growing shoots or down towards roots and storage organs
What is the role of the stomata?
- without stomata there would be too little CO2 for photosynthesis and oxygen could not be released
- a major source of water loss
- water evaporates from spongy mesophyll
- water vapour diffuses out of the stomata
- water loss is controlled by pairs of guard cells
What are the environmental factors that affect the rate of transpiration?
- humidity (decrease concentration gradient)
- temperature (increases kinetic energy)
- air movement (increasees concentration gradient)
- light intensity (photosynthesis opens stomata, water is lost through open stomata)
How do you investigate the rate of transpiration?
- potometer
- measure distance that air bubble moves and divide by time in minutes
Why is photosynthesis so important?
- transfers energy from surroundings into living things
- plants use photosynthesis to make glucose molecules that provide the energy that they need
- glucose molecules are used to build all other materials that make up a plant (plant biomass)
- biomass and store of energy passes into food chain when animals feed on plants
photosynthesis supplies energy to food chain
what occurs during photosynthesis?
- takes place in chloroplasts which have chlorophyll
- traps energy tranferred by light
- allows glucose to be made with water and carbon dioxide
- glucose is a simple sugar
- oxygen is produced
- products have more energy than reactants
- energy is transferred from the environment by light
- endothermic reaction