Plants & Material Cycling Flashcards

Photosynthesis definition

Photosynthesis is a chemical reaction that takes place in chloroplasts in plant cells. Carbon dioxide and water react to produce glucose and oxygen.

The word equation for photosynthesis:

Carbon dioxide + water ——> glucose + oxygen

Chlorophyll role

Chlorophyll, found inside chloroplasts, absorbs sunlight energy for photosynthesis.

Where does the substance come from / how it is used:

• Carbon dioxide

• Water

• Glucose

• Oxygen

• Carbon dioxide: Diffuses from air into leaves and then into leaf cells

• Water: absorbed into roots from soil

• Glucose: Used in respiration and some is converted into starch and stored in the leaves for fuel

• Oxygen: diffuses out of leaf cells and out of leaves into the air

Tissues in a leaf with different adaptations

• The upper epidermis has a waxy cuticle to prevent water loss

• Palisade mesophyll tissue has leaf cells with many chloroplasts for photosynthesis

• The spongy mesophyll tissue has air spaces for the diffusion of gases.

(cut-out text is mesophyll)

Gas exchange occurs through…

stomata

The stomata are opened and closed by…

guard cells

Photosynthesis happens in the … cells

palisade

Stomata are found on the … side of the leaf. Why?

bottom

To minimise water loss - not exposed to sunlight which would cause transpiration - while allowing efficient gas exchange for photosynthesis.

Active transport

the movement of substances from a low to high concentration, requiring energy from respiration

Active transport works against the concentration gradient

Active transport in root hair cells

Active transport is used in root hair cells to absorb mineral ions from the soil

Concentration of mineral ions in the soil is lower than inside the cell

Xylem definition

a type of tissue that forms vessels that transport water and minerals from the roots up the plant stem and into the leaves. They are hollow and strengthened with lignin.

Describe how the palisade mesophyll is adapted to its function.

Leaf cells contain many chloroplasts to carry out photosynthesis

Describe the function of the focussing wheels.

To move the stage to focus the image of the specimen

State a difference between the light microscope and the electron microscope.

Light microscope:

• Visible light

• Lower magnification

• Lower resolution

• Lower cost

• Observe tissues and cells

Electron microscope:

• Beam of electrons

• Higher magnification

• Higher resolution

• Higher cost

• Observe organelles in cells

Magnification equation

Transpiration definition

Transpiration is movement of water through a plant from where is absorbed at the roots to where it evaporates through stomata.

xylem structure

hollow for a fast upward flow and an unobstructed tube

Rate definition

Rate is the change in a quantity per unit time

Humidity definition

Humidity is the concentration of water vapour in the atmosphere

State the plant organs that make up the transpiration system

Roots, xylem and leaf (including stomata)

State the journey water takes from the soil, through the plant and out through the leaves

Soil 🡪 roots 🡪 xylem 🡪 spongy mesophyll 🡪 stomata 🡪 atmosphere

Explain how water moves through a plant

A continuous column of water is pulled up through the transpiration system as water is being lost to the atmosphere through stomata

Explain the effect of increasing temperature on the rate of transpiration

Increasing temperature increases the rate of transpiration

• higher evaporation rate

An increase in temperature increases evaporation, so the rate of diffusion of water from inside the leaf to outside increases

State the effect of decreasing humidity on the rate of transpiration

Decreasing humidity increases the rate of transpiration

A decrease in humidity reduces the concentration of water molecules outside the leaf, so the rate of diffusion of water from inside the leaf to outside increases

State the effect of decreasing the amount of wind on the rate of transpiration

Decreasing the amount of wind decreases the rate of transpiration:

allows a thicker boundary layer of humid air to form around the leaf: acts as a barrier to water vapour diffusion

State the effect of increasing the light intensity on the rate of transpiration

Increasing the light intensity increases the rate of transpiration:

An increase in light intensity generally increases the number of open stomata, so the rate of diffusion of water from inside the leaf to outside increases

Explain how the action of guard cells can control transpiration

Guard cells change shape to open or close stomata. Water is lost through stomata during transpiration which means that the action of guard cells can control transpiration

A … shows the rate of transpiration

potometer

Explain how wind affects the rate of transpiration.

• Wind increases the rate of transpiration

Because more wind moves water vapour away more quickly, so there is a greater concentration gradient and a greater rate of diffusion of water vapour out of the leaf

Explain how temperature affects the rate of transpiration.

• Temperature increases the rate of transpiration

Because a higher temperature means that more particles have enough energy to evaporate from the leaf

Explain how humidity affects the rate of transpiration.

• Humidity decreases the rate of transpiration

Because more humidity means there is a  smaller concentration gradient and a lower rate of diffusion of water vapour out of the leaf

Explain how light intensity affects the rate of transpiration.

An increase in light intensity generally increases the number of open stomata, so the rate of diffusion of water from inside the leaf to outside increases

Describe how mineral ions and water are transported around a plant.

• Mineral ions are absorbed into root hair cells from soil by active transport.
  

• Water is absorbed into root hair cells from soil by osmosis.

• Mineral ions dissolved in water are transported from roots through xylem vessels to the leaf.

• As water evaporates through stomata the continuous column of water if pulled up so water and minerals can be transported around the plant.

What is lignin?

A molecule found in plants that strengthens xylem vessels.

Describe the transport of water through a plant from the soil to water vapour in the atmosphere.

• Water enters xylem vessels - hollow tubes strengthened with lignin- after being absorbed into root hair cells from soil, by osmosis

• Water is transported upwards through the xylem vessels because of the ‘pull’ from above caused by evaporation from leaves

• water then moves into the spongy mesophyll cells where it is evaporated into the air spaces within the leaf

• the water vapour in the leaf air spaces diffuses out of the leaf into the atmosphere through the stomata.

Compare the processes of boiling and evaporation.

Boiling and evaporation are similar because they both involve the change of state of water from a liquid to a gas.

However, boiling occurs in a liquid when particles have sufficient energy to overcome the forces between them whereas evaporation happens at the surface of a liquid as it boils. 

Evaporation can occur over a large range of temperatures whereas boiling only happens at the boiling point.

Suggest why stomatal density is much lower in plants from hotter climates.

In hotter climates water evaporates at a greater rate. To prevent water from being lost there are less stomata which means that there is less opportunity for water vapour to diffuse out.

Define diffusion.

The movement of particles from a high concentration to a low concentration. 

Describe the function of mitochondria.

To carry out aerobic respiration to release energy for the cell

Translocation definition

Translocation is the movement of dissolved sugars/food molecules to where they are needed through phloem tissue

Phloem definition

Phloem is a tissue that forms vessels to transport dissolved sugars and other nutrient molecules around the plant.

Substances in solution can be transported in both directions

adaptations of a phloem ves=el

• Elongated cells

• Pores in end walls

• Hollow tube-like vessel to transport solution long distances. Pores to allow liquid to flow through in both directions.

describe difference between transpiration & translocation

Transpiration transports water and minerals whereas translocation transports dissolved sugars and nutrient molecules

Transpiration happens through xylem tissue where as translocation happens through phloem tissue

Transpiration only transports in one direction from roots to leaf whereas translocation transports dissolved sugars and nutrient molecules in both directions depending on where it is needed.

State where sugar molecules are produced in a plant

Sugar molecules are produced as glucose during photosynthesis which is carried out in the leaves.

Xylem adaptations

• Hollow tube structure: allows water to flow with minimal resistance

• Strong wall made from lignin: helps plant stand upright

Compare the structure of xylem and phloem.

• Both form vessels, or tube-like structures with a hollow interior

Xylem vessels are hollow tubes strengthened with lignin, whereas phloem vessels have end walls containing pores

Compare the function of xylem and phloem.

• Both transport solutions around a plant

• Transpiration transports water and minerals whereas translocation transports dissolved sugars and nutrient molecules

• Transpiration happens through xylem tissue whereas translocation happens through phloem tissue

Transpiration only transports in one direction from roots to leaf whereas translocation transports dissolved sugars and nutrient molecules in both directions depending on where it is needed.

Chlorophyll definition

A green pigment used to convert sunlight energy into chemical energy through the process of photosynthesis.

Photosynthesis definition

Photosynthesis is an endothermic reaction that requires light and takes place in chloroplasts in plant cells. 

Uses of glucose

• Reactant in respiration: essential because it releases energy for life processes

• Storage as starch (e.g. in leaves or tubers)

• Storage as oils/fats (e.g. in seeds)

• Synthesis of cellulose for strengthening cell walls

• Produce amino acids for protein synthesis. This requires nitrate ions from soil

Define synthesis.

Synthesis is producing a compound by a chemical reaction of simpler substances.

glucose chemical formula

C₆ H₁₂ O₆

 Testing a leaf for starch using iodine

Explain what this result for the starch test shows about photosynthesis.

1. Put the leaf in boiling water for 1 min

2. Transfer the leaf to boiling tube containing ethanol for 5 min

3. Dip the leaf in hot water.

4. Spread the leaf on a white tile.

5. Test with iodine solution.

• If starch is present, the iodine will turn from orange to blue-black

• Iodine has turned black in the areas where starch is present

• This means that photosynthesis is happening in these areas because the product of glucose is stored as starch.

Explain how a leaf is well adapted to carrying out photosynthesis

A leaf has a large surface area to absorb light because light is required for photosynthesis.

A leaf has contains palisade cells which are packed with chloroplasts that carry out photosynthesis.

A leaf contains stomata and spongy mesophyll which means that gas exchange can happen. This means that the palisade mesophyll can obtain carbon dioxide which is a reactant of photosynthesis.

A leaf contains access to xylem vessels which means that the palisade mesophyll can obtain water which is a reactant of photosynthesis.

explain how genetic mutation could causes unique leaf patterns

Mutations can be random changes in the DNA code that may cause a new phenotype, such a unique leaf pattern.

State how to calculate the total magnification of a light microscope

Total magnification = Objective lens mag. x eyepiece lens mag

Describe how to focus the image seen in the eyepiece lens

Use the lowest magnification objective lens then place the lens close to the slide and move the stage downwards by turning coarse focussing wheel and then the fine focussing wheel until the image is clear

Describe what the stomatal density tells you about a leaf

The (average) number of stomata in a particular area

preparing the specimen method

1. Paint a thin, even layer of clear nail varnish on the under surface of one part of the leaf

2. When dry, stick a small piece of clear tape over the nail varnish

3. Peel the clear tape off gently

4. Stick the clear tape on a glass slide. Ensure it is smooth with no folds.

5. Use the microscope to observe the stomata

6. Once focussed, count the number of stomata seen in the frame. Only include those fully visible in the frame.

Describe how to observe a sample under a microscope.

• Place the slide on the stage underneath the clips.

• Use the lowest magnification objective lens to start.

• Use the coarse focusing wheel to move the stage close to the objective lens.

• Whilst looking in the eye piece lens, rotate the coarse focusing wheel away from you so the stage slowly moves down.

• Rotate the fine focusing wheel to sharpen the image.

Change the objective lens to change the magnification.

label

explain why there might be differences in stomatal density in different areas of a leaf

Stomatal density could be greater where xylem are positioned to make transpiration efficient.

Stomatal density could be greater where there are more palisade cells because more carbon dioxide is needed for photosynthesis.

Which axis does the independent variable go on?

X axis

Which axis does the dependent variable go on?

Y axis

Explain what is meant by the gradient of a graph.

The steepness of the line.

SI of time

Seconds (s)

Name the piece of equipment used to measure time.

Stopwatch, stopclock, clock

Bar charts and pie charts are used if the independent variable is…

categoric

Line graphs are used if both the independent variable and dependent variable are…

continuous

centimeters to next three units

The further from the light source…

the greater the area the same light intensity acts over

what does inverse square law mean

the intensity decreases with distance

limiting factor definition

A limiting factor is a variable in the environment that when in limited supply stops the maximum rate of a process.

Limiting factors of the rate of photosynthesis are:

• Carbon dioxide concentration

• Light intensity
  

• The amount of chlorophyll

• Temperature

Graphs show limiting factors of photosynthesis – light intensity

Graphs show limiting factors of photosynthesis – temperature

Photosynthesis is an enzyme-controlled reaction

Using greenhouses to maximise photosynthesis

• Greenhouses are used by farmers to grow crops

• Need the maximum rate of photosynthesis to grow more crops

• Profit is the money gained when a product is sold for more than it cost to produce

Limiting factors are important in the economics of enhancing the conditions in greenhouses to gain the maximum rate of photosynthesis while still maintaining profit.

What would happen if we could keep increasing the carbon dioxide concentration and the light intensity, whilst providing the optimum temperature for photosynthetic enzymes?

The rate of photosynthesis would be limited by the amount of chlorophyll in the plant.

Between 1500 lux and 5000 lux, the photosynthesis rate increases proportionally. Explain why.

Light is required for photosynthesis to be carried out. A greater light intensity causes a greater photosynthesis rate.

light intensity unit

lux

define ‘rate of photosynthesis’

How much photosynthesis happens per unit time.

e.g. bubbles of oxygen per minute

State which substances can be synthesised from glucose.

Cellulose, amino acids, starch, fats

Tobacco Mosaic Virus

a viral disease of plants that causes a distinct ‘mosaic’ pattern of discolouration on leaves.

Rose black spot

Rose black spot is a fungal disease where purple/black spots form on leaves.

This means that leaves cannot absorb light for photosynthesis, so the plant has stunted growth

The fungus that causes rose black spot is spread by water and by wind

Fungicides are used to treat

Plant diseases can be detected by:

• stunted growth

• spots or discolouration on leaves

• areas of decay

• abnormal growths

• the presence of pests.

Identification of the exact disease can be made by:

• reference to a gardening manual or website

• identifying microorganisms in a laboratory 

• using testing kits that contain monoclonal antibodies

Plant defences

• Chemical defences: such as poison and antibacterial chemicals

• Physical defences: prevent microorganisms from entering the plant so they don’t cause infection, eg. protective waxy cuticle on leaves which prevents microorganisms from entering. Each plant cell is surrounded by a strong cellulose cell wall which is another barrier to stop microorganism from entering the cell.

• Mechanical defences: prevent herbivores & insects from eating plants, rather than preventing entry of microorganism. e.g. some plants have thorns, some have hairs that act as a deterrent, some have leaves that curl/droop

Explain why a tomato plant infected with tobacco mosaic virus has stunted growth

• Cells infected with TMV do not produce as much chlorophyll.

• Chlorophyll is required to absorb the light needed to carry out photosynthesis, therefore less photosynthesis is carried out in infected plants.

• This means that there is less glucose made so less energy is released to grow.

• Glucose is also used to synthesise cellulose and amino acids, which are both needed to build new cells. So with less glucose being produced there are less of the building blocks needed for growth.

Write the word equation for aerobic respiration.

Glucose + oxygen 🡪 carbon dioxide + water

decay definition

Decay is the breakdown of larger substances into smaller building blocks.

Decomposers

Decomposers are organisms that carry out decay using enzymes

Microorganisms, such as some bacteria and fungi, are decomposers

Importance of decay in an ecosystem

Decay is essential for the cycling of substances in an ecosystem

Many different substances cycle through the biotic and abiotic parts of an ecosystem

Mineral ions are returned to the soil

Carbon dioxide is released as decomposers respire

factor meaning

A factor is something that has an effect.

Biotic factors

Biotic factors are living parts of the environment that can affect the community. 

Biotic factors include predators, availability of food (prey or producers), competition and disease.

Abiotic Factors

Abiotic factors are non-living parts of the environment that affect the community.

This includes all the environmental things that make up the non-living parts of an ecosystem. 
Abiotic factors include water availability, sunlight, wind, pH, temperature and availability of carbon dioxide and oxygen.

Explain why material cycling is important.

• Substances such as nitrates and carbon are released through material cycling 

• These substances allow the growth of new organisms 

Explain the role of microorganisms in decay.

• Decomposers, such as bacteria and fungi, are essential in decay because they break down dead organisms using enzymes.

Explain the importance of decay in an ecosystem.

• When decomposers, such as bacteria and fungi, carry out decay, they break down dead organisms.

• This means that the large molecules that make up an organism are broken down into smaller molecules.

This is important because materials such as nitrate ions and carbon must be cycled in an ecosystem to support the growth of new organisms.

The rate of decay is…

The rate of decay is a measure of how much decay occurs per unit time.