B8 - photosynthesis

photosynthesis definition

photosynthesis is an endothermic reaction in which energy is transferred from the environment to chloroplasts by light.

process of photosynthesis

• energy is transferred from the environment to the chloroplast by light - endothermic reaction

• used to convert carbon dioxide n water into glucose

• oxygen is also released as by product

leaves adaptations

• a large surface area to maximise photosynthesis

• a thin n flat shape to increase the absorption of sunlight

• stomata for gas exchange

• a waxy cuticle to prevent water loss

• some leaves have spines/ hairs for protection against herbivores/ reduce water loss

word equation for photosynthesis

carbon dioxide + water ----→ oxygen + glucose

how does light affect photosynthesis?

• the intensity of the light available to the plant will depend on the amount of energy that it has to carry out photosynthesis

• the more light a plant receives, the faster the rate of photosynthesis

how does temperature affect photosynthesis?

• the temp of the environment affects how much kinetic energy all particles have – so temp affects the speed at which carbon dioxide n water moves through a plant

• the lower the temp, the less kinetic energy particles have, resulting in fewer collisions occurring

• increasing temp increases the kinetic energy of particles, increasing the chance of collisions between reactants n enzymes, results in the formation of products

• at higher temps, enzymes that control the processes of photosynthesis can be denatured - reduces the overall rate

how does carbon dioxide concentration affect photosynthesis?

• the more carbon dioxide that is present, the faster the reaction can occur

how does chlorophyll levels affect photosynthesis?

• the number of chloroplasts will affect the rate of photosynthesis

• the more chloroplasts a plant has, the faster the rate of photosynthesis

• the amount of chlorophyll can be affected by:

  • diseases (such as tobacco mosaic virus)

  • lack of nutrients (such as magnesium)

  • loss of leaves (fewer leaves means fewer chloroplasts)

light intensity equation -  inverse square law

light intensity = 1/ density^2

uses of glucose in plants

• used for respiration (both aerobic n anaerobic)

• converted into insoluble starch for storage in the stems, leaves n roots

• used to produce fat/ oil for storage

• used to produce cellulose, strengthens the cell wall

• combined with nitrate ions absorbed from soil to produce amino acids for protein synthesis

testing for starch - practical

what are greenhouses n their functions?

• the environment is more controlled

• the air is warmer

• greenhouses can be use to overcome limiting factors.

  • allows the plants to grow faster as they are making more food

what are hydroponics n their functions?

• hydroponics is a method of growing plants without soil, using nutrient-rich water instead

• the functions of hydroponics include faster growth rates, higher yields, n more efficient use of resources such as water n space

• also allows for greater control over the growing environment, including temperature, pH levels, n nutrient levels

what are polytunnels n their functions?

• polytunnels are structures made of polyethene that are used in agriculture to create a controlled environment for plants.

• they are designed to protect crops from harsh weather conditions, pests, n diseases.

• polytunnels also help to extend the growing season by providing a warmer environment for plants to grow in.

• the polyethene material allows sunlight to pass through, which helps to promote photosynthesis

• polytunnels can be used to regulate the amount of water n nutrients that plants receive, which can improve crop yields.