Topic 6: Photoysnthesis Flashcards
What is photosynthesis?
A series of enzyme catalysed chemical reactions carried out in the chloroplast. Carbon dioxide combine/react to form glucose. The process requires energy transferred by light.
What type of reaction is photosynthesis?
Endothermic reaction.
How to animals get energy from plants when they eat them?
Glucose and substances made from glucose during photosynthesis are stores of energy. When animals eat plants they get their energy from these stores.
What does biomass mean?
The materials on an organism.
Why are plants and algae producers in food chains?
Because they produce their own biomass and so produce the food for all other life on Earth.
What is the word equation for photosynthesis?
Water + carbon dioxide ➡️ glucose + water
(Energy transferred by light)
Where does photosynthesis occur and why?
Photosynthesis occurs in the chloroplast because the chloroplast contains chlorophyll which absorbs light for photosynthesis to occur.
What is an endothermic reaction?
A reaction where energy from the surroundings is transferred to the products.
Why is photosynthesis an endothermic reaction?
The products of photosynthesis have more energy than the reactants so it is therefore endothermic.
What does the glucose from photosynthesis form?
The glucose molecules formed, link together to form a polymer called starch. This stays in the chloroplasts until photosynthesis stops. The starch is then broken down into simpler substances, which are then moved into the cytoplasm to make sucrose (another type of sugar). This is then transported around plant.
What can sucrose be used for in plants?
- starch(in a storage organ such as a potato)
- other molecules for the plants such as, cellulose, lipids pr proteins
- glucose for respiration (to release energy)
How are leaves adapted?
- leaves are broad and flat giving them a large surface area to absorb sunlight.
- palisade cell’s are near the top of the cell and are packed with chloroplast. Both these factors allow the leaf to absorb a great deal of sunlight.
- leaves are thin so the carbon dioxide doesn’t have to diffuse far.
What is the stomata?
Leaves contain microscopic pores called the stomata (singular stoma). Stomata allow carbon dioxide to diffuse into leaf. Stomata are opened and closed by specialised guard cells.
How are guard cells adapted?
Th stomata are opened and closed by specialised guard cells. In the light, water flows into pairs of guard cells making them rigid. This opens the stomata so carbon dioxide can flow through for photosynthesis to occur. In the dark, in the night water flows out of the guard cells, causing them to loose their rigidity, shutting the the stomata.
How does the stomata cause gas exchange?
Stomata allows oxygen and water vapour to escape into the air. Carbon dioxide flows into the stomata. The flow of different gases into and out of the stomata is an example of gas exchange.
Why is it harder for plants to photosynthesise at the top of a mountain and easier nearer the sea?
There are fewer molecules in each cubic centimetre of air at the top of a mountain than at the bottom. This reduced concentration of air molecules causes a lower rate of photosynthesis in high mountains compared to by the sea.
Also the reaction is catalysed by enzymes that work better at warmer temperatures.
How is photosynthesis catalysed and why?
The reaction is catalysed by enzymes that work better at higher temperatures. This is another reason why photosynthesis at the top of mountains is slower than at the bottom because it’s colder at the top.
What is a meant by a limiting factor?
A single factor that when in short supply can limit the rate of a process, such as photosynthesis.
What are the limiting factors in photosynthesis and how does this affect the rate of photosynthesis?
One of:
- carbon dioxide concentration.
- water
- light intensity
- temperature
The maximum rate of photosynthesis is controlled by the factor in shortest supply - therefore this is the limiting factor.
What is the inverse square law and what is the equation to work out new light intensity?
To calculate a new light intensity (I new) when the distance of the light source changes we use:
I new = I original x d squared original / d squared new
D is distance. I new is inversely proportional to d squared new (light intensity is inversely proportional to the new distance squared) light intensity varies with distance according to the inverse square law.
How are buttress roots adapted to the rainforest?
Some trees are adapted to the rainforest by having huge buttress roots. Like all roots they absorb water and minerals from the soil. However they also help the tall trees from falling over in thin rainforest soil, by acting as props. They also trap leaves and other dead vegetation, which rot to provide additional nutrients to the tree.
The water absorbed by plant roots are used for:
- carrying dissolved minerals
- keeping cells rigid (otherwise plants wilt- their leaves and stems droop)
- cooling the leaves (when water evaporates from them).
- photosynthesis
How are root hair cells adapted to carry out their function?
- The hairs are extensions to the root to absorb lots of water and mineral ions very quickly by providing a large surface area.
- the ‘hairs’ also have very thin cell walls so that the flow of water into cells is not slowed down.
- water enters by osmosis and diffusion.
- tiny tubes join the cytoplasm of some cells together allowing water to diffuse.
- mitochondria needed for active transport.
- no chloroplast as they do not need sunlight as they are underground meaning more space for more useful parts.
What is a concentration gradient?
The difference between 2 concentrations. There will be an overall movement of particles down a concentration gradient from a higher concentration to lower a concentration.
Why do particles in a liquid/fluid move down a concentration gradient?
Particles constantly move in random directions so particles in a fluid spread down a concentration gradient. This is diffusion.
How does water diffuse in plant root cells?
Inside plant roots, the cell walls have an open structure allowing water particles to diffuse towards the middle of the root. (From where the are more of them to where there are fewer.)
What is osmosis?
When solvent molecules (such as water) diffuse through a semi permeable membrane. They diffuse from where there are more of them (a dilute solution of solutes) to where there are fewer (a more concentrated solution).
What is diffusion?
The random movement and spreading of particles. There is a net movement of particles from a high concentration to a low concentration.
Can a solvent pass through a cell membrane by osmosis in a root hair cell?
Yes because cell membranes are semi permeable and so water can pass through to the cytoplasm of root hair cells by osmosis.
Why do plants need mineral salts?
Mineral salts are naturally occurring ionic compounds. Plants need ions from these compounds to make produce new substances. For example plants need nitrate ions to produce proteins.
What are mineral salts?
Naturally occurring ionic compounds that plants need to create new substances in order to survive.
Why do mineral ions move into cells via active transport?
The concentrations of ions in a root hair cell is greater than in the soil. Mineral ions cannot diffuse against this concentration gradient so proteins in the cell membrane pump the ions into the cell.
