Photosyntheis Flashcards
Where does photosynthesis take place
In the chlorophyll in chloroplasts
What does chlorophyll do
Absorbs light
What is the word equation for photosynthesis
Carbon dioxide + water = glucose + oxygen
What is the symbol equation for photosynthesis
6Co2 + 6H2O=C6H12O6 + 6O2
What type of reaction is photosynthesis
Endothermic reaction
Define endothermic reaction
Where energy is transferred from the environment to chloroplasts by light
What is the first reason why plants want glucose
For cellular respiration
What does cellular respiration do
It breaks glucose apart to release energy
What is the second reason plants want glucose
To make cellulose
What is cellulose and how is it made
Its a complex carbohydrate that strengthens cell walls and its made by glucose molecules combining together
What is the 3rd reason plants want glucose
To make starch
How does starch help plants
It breaks down into glucose when there is less photosynthesis (e.g winter) and it is used as long term storage
What is the 4th reason for why plants need glucose
To make amino acids
How are amino acids made in plants
By combining glucose and nitrate ions (from soil)
Why do plants want to make amino acids
Because amino acids combine to make proteins
What is the 5th reason why plants want glucose
To make oils and fats
Why do plants want oils and fats
So they can be stored as a future energy source
What are the 4 factors affecting the rate of photosynthesis
- Light intensity
- Temperature
- Concentration of carbon dioxide in the air
- Chlorophyll
Where is the stomata in a plant
Scattered in the lower epidermis
What happens in the lower epidermis
Co2 diffuses through the holes to then move up the leaf into the spongy mesophyll tissue
Why does the spongy mesophyll tissue have lots of air gaps between the cells
So the gas can easily diffuse through the the next layer - paliside mesophyll layer
What layer does the most photosynthesis happen and why
The palisade mesophyll layer because palisade cells are packed full of chloroplasts
What does the upper epidermis layer do
Has transparent cells to allow sunlight to pass through to get to the chloroplasts in palisades beneath
How are sugar molecules carried to the rest of the plant after photosynthesis
By the phloem
What does the xylem do
Continually brings water up from the roots for the palisade cells to use in photosynthesis
What adaptation does the leaf have to prevent water loss
A waxy cuticle on top
What is a waxy cuticle
A thin waterproof layer of lipids that water cant get through
Why do leaves keep the stomate open for as short a time as possible
So they can maximise Co2 absorption but minimise water loss
How is each stoma formed
From the gap between 2 guard cells
What happens to the guard cells when a plant has lots of water
Guard cells will be well hydrated (turgid) which makes gap between them larger allowing more co2 to diffuse through
What happens to the guard cells when a plant is short of water
The guard cells lose water due to osmosis and become flaccid
What happens to the stomata when guard cells become dehydrated(flaccid)
The stomata close meaning the plant no longer takes in Co2 but will conserve its water vapour
What happens to guard cells at night and why
They close at night when photosynthesis isnt taking place and they dont need Co2 because they’re sensitive to light
Why are stomatas on the lower side of the of the leaf
Because its more shady which makes it cooler so less water will evaporate
Where is meristem tissue found
Found at growing tips of roots and shoots
What can meristem tissue do
It can differentiate into loads of different cell types so that the plant can grow
Define translocation
Movement of cell sap up and snd down the plant
How is translocation achieved
Achieved by phloem cells
What are phloem tubes
Phloem cells that are arranged end to end to form long columns
Why do phloem cells have pores in their walls
To allow cell sap to pass along the phloem tube
Why are xylem tubes ans what do they form
Dead xylem cells with no ends between them so they from 1 long hollow tube
What strengthens xylem tubes
Lignin
What is the role of xylem tubes
They transport both water and mineral ions from the roots up the stem to the leaves where water can be hsed in photosynthesis
Define transpiration
Evaporation of water through the leaves
What is a transpiration stream
A chain of water molecules
What are the 4 factors that influence the rate of transpiration
- Light intensity
- Temp
- Air flow
- Humidity
How does light intensity increase the rate of transpiration
The stomatas open wider to let more carbon dioxide into the leaf for photosynthesis
How does temperature affect the rate of transpiration
Particles of water will have more energy in warmer temperatures so theyre more likely to evaporate and diffuse out of stomata
How does air flow affect the rate of transpiration
Higher air flow means there is a higher concentration gradient which increases rate of transpiration
How does humidity affect the rate of transpiration
Higher humidity means there is a lower concentration gradient which decreases the rate of transpiration
