Unit 3 Biology Flashcards
What is the defintion of Photosynthesis?
A process carried out in organisms containing chlorophyll where light energy is used to convert carbon dioxide and water to make glucose and oxygen
What is the word equation for photosynthesis?
Carbon Dioxide + Water → Glucose + Oxygen
What is the balanced chemical equation for photosynthesis?
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
What is the use of photosynthesis?
To produce glucose for energy and growth in plants
Why is it important for plants to synthesise (produce) glucose? Name 3 points.
- Used as an an energy source for plants for growth, repair and active transport
- Glucose can be converted to starch for long-term energy storage
- To convert glucose into cellulose to make new cell walls
Describe and Explain the method to test a leaf to see if starch is present
1) Place the leaf in a beaker with boiling water using a bunsen burner to stop chemical reactions and break the cell membrane and waxy cuticle so iodine can enter the cytoplasm
2) Then, prepare a test tube with ethanol inside and place the leaf from the beaker into the test tube with ethanol
3) Place the test tube with ethanol and the leaf into a heated waterbath for 5 minutes which breaks down the chlorophyll making it easier to observe any colour change in the iodine.
4) Remove the leaf from the test tube and and rinse it in cold water to stop any chemical reactions
5) Place leaf on petri dish and add 5 drops of iodine on the leaf to test if starch is present
6) Observe the Colour Change:
* Blue-black colour = starch is present meaning photosynthesis HAS occured
* No colour change (Remains brown) = starch is not present meaning photosynthesis has NOT occured
How would you safely carry out the test for starch?
- Wear safety goggles so ethanol and boiling water wont go on eyes
- Tie up any loose hair so bunsen burners flame doesnt touch hair
Why is chlorophyll necessary for photosynthesis?
Chlorophyll absorbs light energy from sunlight and converts it into chemical energy which allows the plant to carry out photosynthesis
Why is carbon dioxide necessary for photosynthesis?
Carbon dioxide is used by plants in photosynthesis to produce glucose which plants need as a source of energy
Why is light necessary for photosynthesis?
Light provides the energy needed for the process of photosynthesis, allowing plants to convert carbon dioxide and water into glucose and oxygen
What is a limiting factor?
It is an environmental condition that directly affects the rate of photosynthesis
What are the 4 main limiting factors of photosynthesis?
- Light intensity
- Carbon dioxide concentration
- Chlorophyll levels
- Temperature
How do you preform the test to see if Chlorophyll is needed for photosynthesis?
SAME STEPS AS TEST FOR STARCH BUT STEP 6 IS WHAT GETS YOU MARKS:
1) Place the variegated leaf in a beaker with boiling water using a bunsen burner
2) Then, prepare a test tube with ethanol inside and place the leaf from the beaker into the test tube with ethanol
3) Place the test tube with ethanol and the leaf into a heated waterbath for 5 minutes
4) Remove the leaf from the test tube and and rinse it in cold water
5) Place leaf on petri dish and add 5 drops of iodine on the leaf
6) Observe the Colour Change:
- The green parts of the variegated leaf will turn blue-black, indicating that starch is present in the areas of the leaf where chlorophyll is present. This shows that photosynthesis has occurred in areas where chlorophyll is present ONLY
- Whilst the parts which used to be white will turn brown (iodine colour)
How do you preform the test to see if Carbon Dioxide is needed for photosynthesis?
1) Place a de-starched plant inside a sealed bell jar consisting of either soda lime OR sodium hydroxide in order to absorb any CO2 which is in the sealed jar so we can get accurate results (photosynthesis can only occur when CO2 is there, but we need to remove it)
2) Then, leave the plant which was in the sealed jar with some light for 1 day
3) After 1day, test the leaf for starch (boil, ethanol, etc.) using iodine
4) Observe results:
- The plants leaf in the bell jar with the soda lime/sodium hydroxide will have a brown colour when tested for starch meaning that starch has not formed meaning photosynthesis has NOT occured when CO2 is not present. So CO2 IS needed for photosynthesis
How do you preform the test to see if Light is needed for photosynthesis?
1) Prepare a de-starched plant and cover one of the leaves with black tape down the middle in order to stop any light from entering the middle part of the leaf
2) Place the plant under a light source and make sure that light is spread evenly on the specific leaf with the tape and leave the plant for 1 day
3) Extract the leaf with the black tape and test it for starch (boiling, ethanol, etc.) using iodine
4) Observe the results:
- The area of the leaf which was not covered with the black paper (green parts) will turn blue-black which indicates that starch HAS formed so photosynthesis HAS occured in areas exposed to light so light IS needed for photosynthesis
- Whilst the area which was covered in black tape will have a brown colour which indicates thst starch has NOT formed so photosynthesis has NOT occured in areas NOT exposed to light
NOTE:
If you are asked to describe how to test for the necessity of light/chlorophyll/carbon dioxide, you only need to say “test for the presence of starch”, you do not need to describe the test for starch as well
ONLY as ONE of the steps, REMEMBER ONE ONLY
What is the effect of light intensity on the rate of photosynthesis?
As light intensity increases, the rate of photosynthesis increases, but only up to a certain point. After reaching a maximum, further increases in light intensity do not affect the rate because another factor becomes limiting.
What is the effect of carbon dioxide concentration on the rate of photosynthesis?
Increasing carbon dioxide concentration causes an increase in the rate of photosynthesis, but only up to a certain level. Beyond this level, the rate of photosynthesis no longer increases as other factors limit the process
What is the effect of temperature on the rate of photosynthesis?
The rate of photosynthesis increases with temperature up to an optimal point. As the tempeature increases from the optimal temperature, the rate decreases because enzymes for photosynthesis get damaged by excessive heat
How many layers are there on a leaf and what are they? (in order)
1) Waxy Cuticle
2) Upper Epidermis
3) Palisade Layer
4) Spongy Mesophyll
5) Lower Epidermis (Has stomata)
What is the vascular bundle?
The vascular bundle is a part of the plant’s transport system, made up of tube-like structures that carry water, minerals, and nutrients throughout the plant using the Xylem and Phloem
What is the use of the Waxy Cuticle?
It is a protective layer on top of the leaf which protects the leaf as it is waterproof and allows water to slide off
What is the use of the Upper Epidermis?
It is thin and transparent to maximize the amount of light intake into the palisade layer underneath it
What is the use of the Palisade Layer?
Has loads of plant cells which are tightly packed together with loads of chloroplasts to ABSORB more light, maximizing photosynthesis
What is the use of the Spongy Mesophyll?
It contains many air spaces which increase the surface area to volume ratio for diffusion of CO2
What is the use and adaptation of the Vascualr Bundle?
Contains xylem and phloem to transport substances TO the leaf and AWAY the leaf (will go more in depth about xylem and phloem later)
What is the use of the Lower Epidermis?
Allows for gas exchange as it has stomata + guard cells
What is the use of the Stomata (Stoma)
The opening bellow the leaf that allows CO2 to diffuse into the leaf and allows oxygen and water (transpiration for water) to leave the leaf by diffusion
What is the use of the Guard Cell?
Allows for the stomata to open and close to allow CO2 to diffuse in, and oxygen to diffuse out
How is the Waxy Cuticle adapted for photosynthesis?
It is transparent to let light through and get absorbed by the palisade layer and also reduces water loss for efficient photosynthesis
How is the Upper Epidermis adapted for photosynthesis?
It is transparent to allow light to pass through to the palisade layer
How is the Palisade Layer adapted for photosynthesis?
It contains tightly packed plant cells with many chloroplasts to maximise light absorption for photosynthesis
How is the Spongy Mesophyll adapted for photosynthesis?
Has loosely packed cells with lots of air spaces to allow efficient gas exchange for photosynthesis
How is the Lower Epidermis adapted for photosynthesis?
The lower epidermis contains stomata, which allow gas exchange and control water loss through transpiration
How is the Guard Cell adapted for photosynthesis?
Guard cells have a thick inner wall and a flexible outer wall, allowing them to change shape and control the stomata opening and closing
How is the Stomata adapted for photosynthesis?
Because their size can be adjusted by guard cells so they can control the amount of air in and oxygen out
How do Guard cells open and close?
Guard cells open and close the stomata through osmosis. When water enters the guard cells by osmosis, they become turgid which causing them to swell which opens the stoma. They also close when water leaves the guard cells as they become flaccid which causes them to shrink and the stomata to close
Why do plants need minerals?
For healthy growth and development of plants
What are the 4 essential plant minerals?
- Nitrates
- Calcium
- Magnesium
- Phosphates
What is the use of Nitrates in a plant?
They are used to make amino acids, which create proteins and proteins are essential for plant growth. Nitrates are also necessary for making DNA in plants
What happens when Nitrates are defficient in plants?
Their growth is stunted and they also have older leaves that turn yellow and die eventually
What is the use of Calcium in a plant?
Calcium forms calcium pectate and this substance hold the plant cells together
What happens when Calcium is defficient in plants?
The leafs of the plant will turn yellow and start to crinkle (leafs will curl)
What is the use of Magnesium in plants?
Magnesium is essential for producing chlorophyll to absorb light and are also needed for enzymes to function
What happens when Magnesium is defficient in plants?
The leaves will turn yellow and will have stunted growth
What is the use of Phosphates in plants?
They are needed to produce ATP for the active transport of substances (minerals, ions, etc) in and out of cells
What happens when Phosphates are defficient in plants?
The leafs of the plant will have purple veins and stunted growth
Where do plants get thier minerals?
From soil
What does the Xylem do?
Transports water and mineral ions from the roots to the leaf (ONLY UPWARDS IN A ONE-WAY SYSTEM)
What does the Phloem do?
Transports sugars (MAINLY SUCROSE) and amino acids from the leafs to the rest of the plant in a 2-way system (BOTH UPWARDS AND DOWNWARDS)
Why do plants need transport systems?
Because they are multicellular therefore have a small surface area to volume ratio so they need to transport minerals and nutrients effectively
Note: An example of a small SA:V ratio is 1:6
Why can unicellular organisms rely on diffusion, and why do multicellular organisms need a transport system?
UNICELLULAR organisms have a LARGE surface area to volume ratio, allowing diffusion to efficiently move substances in and out. MULTICELLULAR organisms need a transport system because their SMALL surface area to volume ratio makes diffusion too slow for efficient movement of substances to all cells
How is the Xylem adapted to its function?
- The Xylem consists of long, hollow tubes formed by dead cells, which allows water to flow freely through them.
- The cell walls are thickened with lignin, which strengthens the vessel and prevents the vessel from collapsing under high water pressure and lignin also provides support to the plant
- The Xylem has no ends between each xylem cell which creates a continuous tube for water to flow easily, without resistance
What is Transpiration?
It is the process where water is absorbed by the roots and goes to the leaf where the water is then evaporated through the stomata
What is the use of Transpiration? (2 uses)
- Transpiration helps pull water and minerals. This is caused by the water loss from evaporation of water as water vapour leaves the stomata. This results in water and nutrients moving up the stem and into the leaves to replace the water lost by evaporation.
- It also helps cool the plant
What are the factors which affect the rate of transpiration? (just name them)
- Light Intensity
- Temperature
- Wind
- Humidity
How does light intensity affect the rate of transpiration?
An increase in light intensity causes the rate of photosynthesis to increase so more CO2 is needed to photosynthesise so the stomata will be open and causes more water to evaporate from the leaves
So: High light intensity = High rate of transpiration
How does Temperature affect the rate of transpiration?
An increase in temperature causes more stomata to be open as hot temperatures causes the rate of photosynthesis to be increased. The water molecules also move faster as they gain more kinetic energy so diffusion happens more quickly (evaporates and leaves the leaf quicker)
So: High Temperature = High rate of Transpiration
How does Wind affect the rate of transpiration?
Windy conditions help maintain a steep concentration gradient by moving the water vapour outside of the leaf away so a HIGH concentration of water will be INSIDE the leaf and a LOW concentration of water will be OUTSIDE the leaf so water vapour diffuses OUT of the leaf
So: Strong Winds = High rate of transpiration
How does Humidity affect the rate of transpiration?
As humidity increases, the rate of transpiration decreases because the air outside the leaf contains more water vapour and this reduces the concentration gradient between the inside and outside of the leaf which SLOWS down the diffusion of water vapour OUT of the stomata
So: High Humidity = Low rate of Transpiration
How can we investigate the rate of transpiration using a mass potometer?
1) Fill the conical flask with water and ensure that there are no air bubbles and place a plant inside the flask with the stem submereged underwater
2) Place a layer of oil above the surface of water
3) Record the Initial mass of the entire setup
4) Place the potmeter in different conditions (Changes in: Temp, light intens, humidity, wind)
5) Leave the plant for 2 hours and then record the new mass (final mass)
6) Then do: Final mass - Initial mass = Water that has evaporated through transpiration is this correct
How can we investigate the rate of transpiration using a bubble potometer?
ill do it later
What organelles are found in root hair cells? (7)
- Nucleus
- Vacuole
- Cell wall
- Cell membrane
- Ribosomes
- Mitochondria
- Cyptoplasm
How does the root hair cell absorb water?
Root hair cells have projections that stick into the soil and have a large surface area to volume ratio and the water moves from the soil to the root hair cell by osmosis as there is a higher concentration of water outside the root and a lower concentration of water inside the root
How is the Phloem adapted to its function?
- The phloem has sieve plates which are thin cells that have holes and allow easy flow of substances
- The phloem are also supported by companion cells, which are packed with mitochondria to provide ATP for active transport
- The sieve tube lack a nucleus, creating more space for transporting sugars.
What is translocation?
It is the movement of food molecules (sucrose and amino acids) around the plant in phloem vessels
What are the main differences between the Xylem and Phloem?
- Xylem cells are dead whereas phloem cells are living
- Xylem transports water and mineral ions from ROOTS TO LEAVES whereas phloem transports sugars (sucrose) and amino acids FROM THE LEAVES to the rest of the plant
- Xylem in found on the inside of vascular bundles whereas phloem is found on the outside of the vascualr bundle
- Xylem has a 1-way flow whilst phloem has a 2-way flow
