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bio topic - Coggle Diagram
bio topic
uses of glucose
- energy source. glucose molecules can be stored as starch (they link together and store it as grains) and then broken down when needed using energy created through respiration.
- cellulose. this is a tough molecule that is used to built the cell wall. it gives strength and rigidity to the cell, and is composed of thousands of glucose molecules.
- lipids. plant cells can convert the carbohydrate glucose (consisting of carbon, hydrogen and oxygen) to other types of evergy storages, like fat and oils.
- proteins. combining glucose with nitrates creates amino acids, which are then used to create proteins, often used for growth repair.
limiting factors
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in a plant, these could be temperature, light intensity, water or carbon dioxide.
if one of these factors are restricted, the rate of photosynthesis will be below the maximum possible rate.
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the rate/factor graph is different for temperature because at a certain temperature (about 40°c), the enzymes in a plant stop functioning, causing the rate to decline.
these enzymes repair themselves so after a while, so if the temperature returns to normal, the rate will start to increase.
specialised cells
xylem cells
xylem cells destroy their interior cell walls to become a vessel, allowing for faster movement of the water that runs through it
adaptations:
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the cells kill their outer wall so that water cannot leak from the sides, though osmosis
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phloem vessel
this moves products created by photosynthesis to areas of the plant which need it; such as for growing and creating seeds
Transport in the phloem is both up and down the stem. Transport of substances in the phloem is called translocation.
specialised cells:
Sieve tubes – specialised for transport and have no nuclei. Each sieve tube has a perforated end so its cytoplasm connects one cell to the next.
companion cells - are attached to each sieve tube to provide the energy needed for translocation. a sieve tube is completely dependant on these companion cells
guard cells
cover the stomata and have control over its contractions and expansions. when turgid, it is closed whereas when its turgidity declines, the cells open
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pondweed practical
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method:
Set up a boiling tube containing 45 cm3 of sodium hydrogencarbonate solution (1%). Allow the tube to stand for a few minutes and shake to disperse any air bubbles that might form.
cut a piece of the pondweed, Cabomba. The pondweed should be 8 cm long.
use forcepts to place the pondweed in the boiling tube carefully. Make sure that you don't damage the pondweed, or cause the liquid to overflow.
Position the boiling tube so that the pondweed is 10 cm away from the light source. Allow the boiling tube to stand for five minutes. Count the number of bubbles emerging from the cut end of the stems in one minute. Repeat the count five times and record your results.
Calculate the average number of bubbles produced per minute. Repeat the experiment at different distances away from the light source.
variables:
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Control variables – concentration of sodium hydrogencarbonate solution, temperature, using the same piece of Cabomba pondweed each time.
transpiration
transpiration is when water travels from the roots of a plant, through the xylem and out of the stomata.
this process is able to take place because the water molecules are cohesive, meaning they are "stuck together", and are pulled along
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structure of a leaf
waxy cuticle
upper epidermis
palisade mesophyll
spongy mesophyll
lower epidermis
this layer contains the stomata, which are small gaps controlled by the movement of guard cells. they allow water to exit the leaf and evaporate; they are the end of the transpiration cycle
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this layer has large gaps of air to allow gas exchanges to take place easier. this layer has less chloroplasts
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the transparent layer between the mesophyll and waxy cuticle. it is adapted to be transparent so that light can get through to the chloroplasts in the mesopyhll
coats the top and bottom of a plant with wax to stop water from evaporating in higher temperatures. plants in hot temperatures will have a thicker coating of wax whereas ones in colder climates often don't need it
in addition, plants underwater don't need a waxy cuticle as the water wont evaporate
gas exchange in alveoli
the human lungs provide an exchange surface adapted for absorbing oxygen and transferring carbon dioxide
Gaseous exchange occurs in the alveoli by simple diffusion. The blood flowing past the alveoli is rich in carbon dioxide and very poor in oxygen. The gas molecules naturally flow in the direction of lower concentration through the thin gas exchange membrane, which is only two cells thick.
adaptations:
- steep concentration gradient
- high surface area:volume ratio
- moist lining dissolves gases
- thin walls, short diffusion
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