3.1

Question 1

define food security

Answer 1

food security is the ability of human populations to access food of sufficient quality and quantity.

Question 2

why is food security an increasing issue in human population

Answer 2

increase in human population without increase in land available for food production.

Question 3

Define sustainable food production

Answer 3

food is produced continuously without degrading natural resources on which agriculture depends on.
e.g water supply/soil

Question 4

food production and photosynthesis

Answer 4

all food production is dependent ultimately upon photosynthesis
“all flesh is grass”

Question 5

plant crop examples ;

Answer 5

cereals, potatoes, roots, legumes

Question 6

qualities breeders seek to develop in their crops

Answer 6

high nutritional value, resistance to pest/species, characteristics suited to growth and harvesting and can thrive in particular environmental conditions low e.g drought

Question 7

control of food production ;

Answer 7

use of fertiliser - can increase yield, but pollute surrounding environments.

protecting crops from yeast - increase yield by killing crop pests, can pollute environment.

protecting crops from diseases - disease will decrease yield, may produce food unsuitable for eating.

Competition - competition from weeds can decrease yield.

breeding of higher yield cultivators - increased yield but may require more intensive farming methods and more specific growing environments

Question 8

trophic feeding level

Answer 8

only 10% of the energy from one trophic (feeding) is available to the next.

Question 9

why livestock produce less food per unit area than plant crops

Answer 9

Each step between a trophic level in a food chain, brings a loss fixed of energy. There are more trophic levels in a food chain which produces livestock, Therefore, livestock production produces far less food per unit area of land than plant crop plants.

Question 10

explain how energy is lost from the food chain but from the food web

Question 11

advantages of livestock

Answer 11

livestock production is often possible in environments unsuitable for growing crops.

Question 12

define photosynthesis

Answer 12

photosynthesis is a series of enzyme controlled reactions using photosynthetic pigments to absorb light energy and convert it to chemical energy.

Question 13

Getting the light

the three fates of light when it hits a leaf

Answer 13

1. Absorbed (can be used for photosynthesis)
2. Reflected
3. Transmitted (passes through)
   - light energy must be absorbed by photosynthetic pigments to generate ATP so it can be used in photolysis.
   The light that is absorbed is absorbed by pigments within the chloroplast.

Question 14

absorption spectra

Answer 14

Absorption means taking something in.

An absorption spectra shows how much of a specific wavelength of light is absorbed by photosynthetic pigments.

Question 15

name the colours along the spectrum (ROYGBIV)

Answer 15

Violet Indigo Blue Green Yellow Orange Red

400 500 600 700

Question 16

where light is absorbed by the pigments

Answer 16

“Diagram”

Question 17

why are chloroplasts green

Answer 17

chloroplasts absorb every light wavelength except for green which is reflected

Question 18

absorption of light. The three Different pigments

Answer 18

pigments in chlorophyll absorb light

1. chlorophyll A
2. chlorophyll B
3. carotenoids

Question 19

why is it useful for the plant to have several different pigments

Answer 19

As each pigment absorbs a different range of wavelength, the plant can absorb a wider/increased range of light wavelengths to maximise the amount of light energy absorbed.

Question 20

describe the role of carotenoids

Answer 20

carotenoids extend the range of wavelengths absorbed and pass energy to chlorophyll for photosynthesis.

Question 21

action spectra

Answer 21

the action spectra shows the wavelength of light at which there is the most photosynthetic activity.

Question 22

there are two stages in photosynthesis

1. light dependent reactions

Answer 22

• In the light dependent stage, light energy is used to synthesise ATP. Absorbed light energy excites electrons in photosynthetic pigment molecules and these electrons are transported through electron transport chain and generate ATP by ATP synthase.
• Light energy is also used to spilt a water molecule into oxygen and hydrogen (process called the photolysis of water).
• oxygen is evolved from the leaf as a product .
• The hydrogen is transferred to the calvin cycle by the hydrogen accepting coenzyme NADP that becomes reduced to form NADPH.
• The ATP from the light dependent reactions is transferred to the calvin cycle.

Question 23

two stages in photosynthesis

2. carbon fixation

Answer 23

• The enzyme RuBisCO fixes carbon dioxide from the atmosphere by attaching it to RuBP to form 3PG.
• The 3PG produced is phosphorylated by ATP and combined with hydrogen from NADPH to form G3P.
• G3P is used to produce sugars such as glucose which may be used as a respiratory substrate, synthesised into starch, cellulose or passed to other biosynthetic pathways leading to the formation of metabolites such as DNA, protein and fat.
• G3P is also used to regenerate RuBP to continue the cycle.