Photosynthesis Flashcards
Raw materials required for photosynthesis
Carbon dioxide, water and light energy
Photosynthesis
An anabolic (building up) process in which the radiant/ sunlight is captured by chlorophyll in the chloroplasts and is stored as chemical potential energy in the bonds of glucose and other organic molecules for later.
Chloroplast
Organelle where photosynthesis occurs and has a double-membrane surrounding it
Stroma
Found in the chloroplasts.
Grana / Granum
Suspended in the stroma and structures called grana. Each granum is a stack of thylakoid discs and this is where chlorophyll molecules are found
Chlorophyll
Absorbs energy from the sun in order for photosynthesis to take place in the chloroplasts.
Intergrana
Membranes that connect grana together. These keep the stacks apart from each other and move substances into and out of the thykaloids
Starch granules
Where excess glucose is stored
How chloroplasts are suited to performing photosynthesis
- Chlorophyll molecules are situated in the grana which trap radiant energy from the sun. Chlorophyll reflects the green part of the light spectrum and absorbs blue and red wavelengths - making leaves appear green in colour
- Membranes are arranged in layers called grana - which increase surface area for chemical reactions in the light dependent phase
- Stroma - contains enzymes needed to speed up the chemical reactions that take place during the light independent phase of photosynthesis
- Double membrane - selectively permeable and allows entry of water, carbon dioxide and exit of glucose and oxygen
Cuticle (leaf)
Non-cellular, water proof and transparent. Allows light to pass through
Upper epidermis (leaf)
Single layer of cells on the upper surface of the leaf. Allows light to pass to cells below
Palisade mesophyll (leaf)
Cells are vertically arranged so that many can fit into small place. Have large number of chloroplasts and are positioned a top region of leaf
Spongy mesophyll (leaf)
Have large air spaces for fast diffusion of gases to and from the photosynthesizing cells. Cells have few chloroplasts and are positioned at the lower region of leaf near stomata
Veins - vascular bundles (leaf)
Act as drain pipes distributing water and minerals to the leaves and conducting away manufactured food to other parts of a plant
Stomata (leaf)
Pores that allow gaseous exchange to take place. Carbon dioxide enters through stomata and oxygen leaves
Thin lamina (leaf)
Provides a short distance over which diffusion of gases takes place
Factors affecting rate of photosynthesis
- Light intensity = light intensity increases, photosynthesis increases
- Temperature = Increase in temperature, leads to an increase in rate of photosynthesis (too hot can cause enzymes to denature)
- Carbon dioxide concentration = more carbon dioxide, faster rate of photosynthesis until maximum is reached
- Water availability = photosynthesis is slowed down when transpiration is reduced.
Limiting factor
A factor that is not adequate / when in short supply may reduce rate of photosynthesis
Importance of photosynthesis
Produces oxygen required by all living organisms for respirating. Maintains balance of carbon dioxide in the atmosphere and reduces excess carbon dioxide, helping to prevent greenhouse effect. It also provides living organisms with organic compounds needed. Provides us with fossil fuels.
Autotrophs
Produce organic molecules from carbon dioxide and other inorganic raw materials obtained from the environment. Ultimate source of organic compounds for heterotrophs
Photoautotrophs
Use light as their source of energy to synthesize organic compounds. Occurs in all plants, algae and cyanobacteria
Chemoautotrophs
Harvest energy from oxidizing inorganic substances such as sulphur and ammonia. Is unique to prokaryotes such as bacteria
Heterotrophs
Live on organic compounds produced by other organisms. Are dependent on photoautotrophs for food and oxygen
