Photosynthesis Flashcards
What is photosynthesis?
Photosynthesis is the process by which green plants use sunlight to convert carbon dioxide and water into glucose and oxygen.
Where does photosynthesis take place in a plant?
It takes place in the chloroplast of plant cells, mainly in the leaves which contains chlorophyll which absorbs energy from sunlight.
What are the products of photosynthesis?
Oxygen - released into the air
and
Glucose- a sugar used for energy or stored
What is the equation for photosynthesis ?
Sunlight
Carbon + water ——> Glucose + Oxygen
Dioxide Chlorophyll
Sunlight
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Chlorophyll
What are the 2 stages of photosynthesis?
1) The light dependent stage
Here is where the chlorophyll in the chloroplast traps light energy from the sun. The energy is used to split water (H2O) into Hydrogen (H) and Oxygen (O2). Oxygen is a waste product and diffuses out of the leaf. Energy is also stored in ATP
2) The light independent stage
Using energy from ATP, The hydrogen (H) from the above is combined with Carbon dioxide (CO2) to form glucose (C6H12O6).
Which pigment is primarily responsible for capturing light energy in plants?
Chlorophyll
What gas is taken in by plants during photosynthesis?
Carbon Dioxide
What is the primary function of water in photosynthesis?
Water provides electrons and protons for the light-dependent reactions and produces oxygen as a byproduct.
Fill in the blank: Photosynthesis primarily occurs in _____ leaves.
green
What is the significance of photosynthesis to life on Earth?
Photosynthesis is crucial because it produces oxygen for breathing and organic compounds that are essential for most life forms on Earth. Also forms the base of the food chain.
What is the end product of the light independent stage?
The end product is glucose.
What is the effect of increasing temperature on the rate of photosynthesis?
Increasing temperature generally increases the rate of photosynthesis up to a certain point, after which it may decrease due to enzyme denaturation.
What is the function of the stomata in plants?
Stomata are small openings on the surface of leaves that allow for gas exchange, including the intake of carbon dioxide and the release of oxygen.
Fill in the blank: The light-dependent reactions convert _____ energy into chemical energy.
light
Through which part of the leaf does carbon dioxide enter?
Stomata
How does water reach the leaf cells?
Water is absorbed by roots, moves through the xylem, and enters leaf cells by osmosis.
What happens to the glucose produced in photosynthesis?
Used in respiration for energy
Stored as starch
Converted to sucrose and transported
Used to build fats, proteins, and other carbohydrates
converted into cellulose or other organic compounds.
How can farmers increase the rate of photosynthesis in crops?
By providing more light, increasing carbon dioxide levels, and controlling temperature in greenhouses.
What test is used to prove that photosynthesis occurred?
The starch test: using iodine to test for the presence of starch in leaves.
Why must a leaf be boiled in alcohol before testing for starch?
To remove chlorophyll and make the leaf pale so the color change with iodine can be seen.
What are the main parts of a leaf involved in photosynthesis?
Waxy Cuticle, upper epidermis, palisade layer, spongy mesophyll, stomata, guard cells, and veins.
How does a large surface area help a leaf photosynthesize?
It allows the leaf to absorb more sunlight for photosynthesis.
Why is the leaf thin?
To allow gases to diffuse quickly to cells.
What is the function of the transparent cuticle and upper epidermis?
To allow sunlight to penetrate to the photosynthetic cells below.
Why are chloroplasts mostly found in the palisade layer?
Because this layer is at the top of the leaf and gets the most light.
What role do stomata play in photosynthesis?
They allow carbon dioxide to enter and oxygen to exit the leaf.
What do guard cells do?
They control the opening and closing of the stomata.
How does increasing light intensity affect photosynthesis?
It increases the rate of photosynthesis until a maximum rate is reached.
How does increasing carbon dioxide affect photosynthesis?
It increases the rate up to a certain level, then it levels off.
What happens to photosynthesis if the temperature is too high?
The enzymes denature, and the rate of photosynthesis drops.
What would happen without photosynthesis?
There would be no oxygen or food for most living organisms, leading to extinction.
How does photosynthesis help regulate the atmosphere?
It removes carbon dioxide, helping to control the Earth’s temperature.
Do plants do both photosynthesis and respiration?
Yes, they photosynthesize during the day and respire all the time.
How can you show that chlorophyll is needed for photosynthesis?
Use a variegated leaf (green and white), do the starch test, and only the green parts will turn blue-black.
How can you prove light is needed for photosynthesis?
Cover part of a leaf with foil, leave it in sunlight, then test for starch—only exposed areas turn blue-black.
What do you count in the Elodea (aquatic plant) experiment to measure the rate of photosynthesis?
The number of oxygen bubbles released per minute.
What does the starch test prove in a leaf?
That photosynthesis has occurred, producing starch (glucose stored as starch).
What are the steps to test a leaf for starch?
Boil in water → Boil in alcohol → Rinse in warm water → Add iodine.
Why do you boil the leaf in water first?
To kill the cells and stop all chemical reactions
Why do you boil the leaf in alcohol?
To remove chlorophyll so the iodine test result is clearly visible.
Why do you rinse the leaf in warm water after the alcohol?
To soften the leaf, as alcohol makes it brittle.
What does a blue-black color after adding iodine indicate?
That starch is present and photosynthesis occurred.
What adaptations make the leaf efficient at photosynthesis?
Large surface area to absorb more sunlight
Thin structure allows gases to diffuse quickly
Stomata allow gas exchange
Chloroplasts are concentrated in the palisade layer
Transparent cuticle allows light in
Vascular tissues (xylem and phloem) transport water and food
What are guard cells and what do they do?
Guard cells are specialized cells that surround stomata and control their opening and closing, helping regulate gas exchange and water loss.
What is the role of chlorophyll in photosynthesis?
Chlorophyll traps sunlight energy, which is essential for the light-dependent stage of photosynthesis.
What is needed for photosynthesis to occur?
Light, chlorophyll, carbon dioxide, and water.
How does carbon dioxide reach the leaf cells?
It diffuses through the stomata into air spaces, then into the cells.
How does light reach the chloroplasts?
Light passes through the transparent cuticle and upper leaf layers to reach chloroplasts, especially in the palisade layer.
What happens to the oxygen produced in photosynthesis?
Some is used in plant respiration, and the rest diffuses out through the stomata.
What is a limiting factor?
A condition that, if in short supply, slows the rate of photosynthesis even if other conditions are ideal.
What are the main limiting factors of photosynthesis?
Light intensity
Carbon dioxide concentration
Temperature
Availability of water
How does temperature affect photosynthesis?
It affects enzyme activity; too low or too high can slow or stop photosynthesis.
Why is carbon dioxide often a limiting factor?
Because its concentration in the atmosphere is low; in greenhouses, extra CO₂ is often added to increase yield.
How does light intensity affect photosynthesis?
Low light reduces the rate; photosynthesis increases with more light, up to a point.
When can water be a limiting factor?
During drought or dry conditions, water shortage limits photosynthesis.
What is etiolation?
Etiolation is the abnormal growth of plants in darkness, where stems become long and pale with small yellow leaves due to lack of chlorophyll.
Why does etiolation occur?
The plant uses stored food to grow and stretch towards light, trying to reach sunlight and resume normal photosynthesis.
