Photosynthesis

Seite 1

Photosynthesis

carbon dioxide + water -----> glucose + oxygen

during process light energy is absorbed by chlorophyll in chloroplasts (in green part of plant)

used to convert carbon dioxide and water into sugar (glucose)

oxygen is by-product

leaves are adapted to allow the maximum amount of photosynthesis to occur

some of the glucose produced during photosynthesis is immediately used by the cells of plants.

however most of the glucose is converted into insoluble starch and stored

testing for starch- use iodide solution that is yellowy-brown and we know that photosynthesis has taken place if turns dark blue.

leaf adaptations-

leaves are broad- larger surface area

contain chlorophyll to absorb the light energy

air spaces to let carbon dioxide to get into cells and oxygen to leave them after diffusion

veins to bring lots of water to cells

The rate of photosynthesis may be limited by shortage of light, low temperature and shortage of carbon dioxide

however we can manipulate the levels of each of these artificially to increase the rate of photosynthesis in food crops

we need all these factors in order for the rate of photosynthesis to be as fast as possible as otherwise the enzymes will denature resulting in a decrease in the rate of photosynthesis

temperatures in photosynthesis affect the rate of reactions, however if the temperature reaches 40-50 degrees, the enzymes will start to denature

plants and algae make glucose when they photosynthesise- and glucose is vital for their survival

some glucose produced is used immediately by the cells- for respiration to provide energy for cell functions such as growth and reproduction

it is broken down by oxygen and carbon dioxide and water are the waste products of the reaction

the energy released is used to build smaller molecules from bigger ones

some of the glucose is stored as starch to build up the glucose into more complex carbohydrates eg cellulose

this strengthens the cell walls

plants use some glucose to make amino acids

this is down by: combining sugars with nitrate ions and other mineral ions from the soil

these amino acids are then built up into proteins to be used in the cells using energy from respiration

plants make food by photosynthesis and it is moved around the plant in the phloem

glucose is soluble in water and so lots of glucose stored in plant cells could affect the water balance of the whole plant

starch is insoluble in water so has no effect on the water balance in the plant

many plants produce tubers and bulbs to help them survive through winter as they are full of stored starch

plants and algal cells use soluble glucose in several ways:

respiration

to convert into insoluble starch- storage

to produce fats or oils for storage

fats, oils or cellulose used in cells and wall

factors such as light levels, low temperature and carbon dioxide levels affect the rate of photosynthesis

the environment can be artificially controlled to make sure these factors do not limit growth, which has a number of benefits

the more a plant photosynthesises, the more biomass it makes and the faster it grows- beneficial to farmers

instead of greenhouses farmers use polytunnels in order to make crops as big as possible- more profit

glass of plastic structure is more controllable and warmer so increases rate of photosynthesis- produces a higher yield

we cannot control a crop’s environment as it differs throughout the day and through the seasons so we use technology to do this known as hydroponics- using a computer

advantages:

turnover is fast

profits are high

crops are clean and unspoilt

no ploughing or preparing the land

system crops can be grown on poor land

perfect balance of mineral ions

crops grow increasingly quicker

physical factors that affect the distribution of living things include:

temperature

nutrients

amount of light

availability of water

availability of oxygen and carbon dioxide

you can get quantitative data on the distribution of organisms in the environment using random sampling with quadrats or sampling along a transect

you can determine the range, mean, median and mode of your data

different methods can be used to collect environmental data

validity and reproducibility must be considered carefully as it is difficult to control variables in fieldwork

sample size is an important factor in both reproducibility and validity of data