| what is food security | the ability of human populations to access food of sufficient quality and quantity |
| what are the three strains of food security | quantity
quality
access |
| what does increase in human population and concern for food security lead to | a demand for increased food production |
| what must food production be | sustainable
not degrade the natural resources on which agriculture depends |
| what does agricultural lproduction depend on | factors that control photosynthesis and plant growth |
| is the area to crow crops limited or unlimited | limited |
| what four factors does increased food production depend on | breeding of higher yielding cultivars
use of fertiliser
protecting crops from pests
diseases and competition |
| what is all food production dependent ultimately upon | photosynthesis |
| what are some plant crop examples | cereals
potato
roots
legumes |
| What kind of crops do breeders intend to develop | crops with:
higher nutritional values
resistant to pests and diseases
physical characteristics suited to rearing and harvesting
the ability to thrive in particular environmental conditions |
| where is livestock production often possible | in habitats unsuitable for growing crops |
| what part of the electromagnetic spectrum drives photosynthesis | visible light |
| what happens to light energy that is not absorbed by leaf pigments | it is transmitted or reflected |
| what happens to light energy that is absorbed by photosynthetic pigments | it generates ATP
it is used for photolysis |
| what are substances in a leaf that absorb light called | pigments |
| what are the four photosynthetic pigments found in plants | chlorophyll A
chlorophyll B
Carotene
Xanthopyll |
| what is the function of choloropyll A | initiates the light reactions / photolysis |
| what is the function of chlorophyll B | accessory pigment |
| what is the function of carotene | accessory pigment / carotenoid |
| what is the function of xanthophyll | accessory pigment/carotenoid |
| what is the function of the accessory pigments | capture light energy and then pass energy on to chlorophyll A |
| how can we measure the proportion of a particular wavelength absorbed by a pigment | using a spectrophotometer / spectroscope |
| what will be seen on a spectroscope if a wavelength/colour is absorbed | there will be a black band over that wavelength/colour |
| what is an absorption spectrum | a graph plotting a pigments visible light absorption |
| what is an action spectrum | graph of the rate of photosynthesis over all visible wavelengths of light |
| what does each pigment absorb | a different range of wavelengths of light |
| what do carotenoids do | extend the range of wavelengths absorbed and pass energy to chlorophyll for photosynthesis |
| what structures are present in chloroplasts | thylakoid
stroma |
| what is found in the thylakoid membrane | chlorophyll |
| where does photolysis/the light dependent reaction take place | the membrane of the thylakoids in the chloroplasts |
| describe photolysis | light energy strikes the thylakoid membranes and is absorbed by the pigment molecules
absorbed light energy excites electrons in the pigment molecule
the transfer of these electrons through the electron transport chain releases energy to generate ATP by ATP synthase
energy is also used to split water into oxygen (which is evolved/released) and hydrogen ions, which are transferred to the coenzyme NADP, forming NADPH. |
| what is produced at the end of the light reaction | ATP
NADPH
oxygen |
| where does the calvin cycle (carbon fixation stage) take place | the stroma of the chloroplast |
| describe the calvin cycle | the enzyme RuBisCO fixes carbon dioxide by attaching it to ribulose bisphosphate (RuBP) producing 3-phosphoglycerate (3PG) The 3PG is phosphorylated by ATP and combined with hydrogen ions from NADPH to form glyceraldehyde-3-phosphate (G3P) G3P is used to regenerate RuBP and for the synthesis of glucose |
| what is glucose used for in the calvin cycle | as a respiratory substrate
synthesised into starch or cellulose
passed to other biosynthetic pathways (which can lead to the formation of a variety of metabolites such as DNA, protein and fat) |
