B3 - Living Together - Food Ecosystems Flashcards
what are enzymes?
living things produce enzymes which act as biological catalysts. Reduces the need for higher temperature and speeds up useful chemical reactions in body
lock and key model
substrate: molecule changed in the reaction
Every enzyme has an active site; the part where it joins on to the substrate to catalyse.
Enzymes have a high specificity, so the sub needs to fit like a lock and key
Things that affect the rate of reaction (enzymes)
temperature: higher temp increases rate as the sub and enz have more energy + optimum temp
pH: if pH is too low/high, it interferes the bonding holding the enzyme + optimum pH
The higher the substrate concentration, the faster the reaction
what is photosynthesis?
Energy from the sun is used to make glucose. Some of it is used for cellular respiration/ stored/ growth.
endothermic
which subcellular structure does photosynthesis occur and how?
Chloroplasts; contains enzymes which catalyse reactions and chlorophyll which absorbs light energy
word equation for photosynthesis?
carbon dioxide + water →glucose + oxygen
how does the rate of oxygen production correspond to the rate of photosynthesis?
oxygen is a byproduct of photosynthesis, so the more oxygen being produced, the more photosynthesis is occurring.
limiting factors of photosynthesis
- light slows down the rate of photosynthesis, will go straight when at highest point due to another limiting factor
- co2 same as light will increase but wont coz of limiting factor
- temp enzymes could get denatured after optimum temp 45
diffusion
net overall movement of particles from an area of higher concentration to an area of lower concentration
osmosis
the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concen….
active transport
movement of particles across a membrane against a concentration gradient, using energy transferred during respiration
where is the stomata and what does it do?
- in plants, the lower surface of the leaf is fully of tiny pores called stomata
- stoma let gases such as o2 and co2 diffuse in and out
- also allows water vapour to escape (transpiration)
how are plant roots adapted to be able to absorb lots of water and mineral ions from the soil?
- the cells on plant roots grow into long hairs which stick out into the soil
- each branch of a root will be covered in millions of these microscopic hairs
- this gives a big surface area for absorbing water and mineral ions from soil
by which process is water from the soil drawn into the plant/root hair cells?
osmosis, as there is a higher concentration of water in the soil than inside the plant, so the water is drawn from the root hair cell.
by which process are mineral ions drawn into the plant/root hair cells?
active transport, since the concentration of mineral ions in the root hair cells is usually higher than in the soil. the cells use molecules of ATP provide energy to actively transport the ions.
What are phloem tubes made up of? (2)
- columns of living cells called sieve tube elements.
- they have perforated end-plates to allow stuff through
how do sieve element tubes survive?
they have no nucleus, so each sieve tube has a companion cell, which carry out the living functions for both its self and the sieve tube
what do phloem vessels transport?
food substances (mainly sugars) both up and down the stem to growing and storage tissues (translocation)
how do the sugars that are translocated from photosynthetic tissues enter the phloem?
by active transport. They are pushed around by water, which enters the phloem by osmosis
how are xylem tubes made up of?
made up of dead cells joined end to end with no connecting cell walls between them (to create a long tube) and a lumen between them
adaptations on the xylem tubes?
the thick side walls are made up of cellulose. they’re strong and stiff, which gives the plant support. the cell walls are also strengthened with a material called lignin.
what do the xylem tubes carry?
water and mineral ions in aqueous solutions from the roots up the stem to the leaves in transpiration steam
What is transpiration and how is it caused?
is the loss of water from the plant
it’s caused by evaporation and diffusion of water from a plant’s surface.
water ends up diffusing from the stomata; it’s just a side affect
what do guard cells do with stomata?
stomata are surrounded by guard cells, which change shape to control the size of the pore.
what happens when the guard cells are turgid/flacid/light
when guard cells are turgid, (swollen with water) the stomata are open, when flaccid, the stomata close.
stomata auto closes when supplies of water are low
also sensitive to night light
what is plasmolysed?
if the plant’s really short of water, the cytoplasm inside its cells starts to shrink and the membrane pulls away from the cell wall.
Explain how the stomata open in response to stimuli such as light?
- Potassium ions are pumped into guard cells in response to stimuli
- increases the solute concentration of the guard cells
- water then moves into the guard cell via osmosis
- this makes the guard cells turgid and stoma opens
What are the three things transpiration rate is affected by?
increase in light intensity
increase in temperature
increase in air movement
how does an increase in light intensity play a part in the rate of transpiration?
- bright light increase the rate of photosynthesis, which means there is more demand for water in the leaves, so more water is drawn up the roots.
- bright light also causes the stomata to open to let C02 in, allowing more water vapour to diffuse out
how does an increase in temperature play a part in the rate of transpiration?
warm temperatures causes water particles to have more energy to evaporate and diffuse out of the stomata.
how does an increase in air movement play a part in the rate of transpiration?
transpiration happens faster. diffusion happens quickly.
how to work out the percentage change for the plant light practical?
final mass - initial mass / initial mass / 100
what could you measure to estimate transpiration rate?
you can measure the loss of mass with the formula
remember the practical with the plant…
What calculation do you use to calculate the rate of water uptake in a potometer practical?
distance moved / time taken
What is the potometer?
a special piece of apparatus used to measure water uptake by a plant. This gives an estimate of transpiration rate because water uptake by the plant is related to water loss from the leaves (transpiration rate)
how can you view stomata, xylem, and phloem?
you can use a light microscope to view the stomata. nail polish!!
how do you calculate the mean rate of photosynthesis from a graph?
volume over time taken
number equation for photosynthesis?
6CO2+6H2O→C6H12O6+6O2
what is stored as starch in a plant?
plants produce glucose during photosynthesis
some glucose is stored as starch
what does the starch test show?
it shows plants need light to photosynthesise
