SB6, SB8, SB9 Biology (paper 2) 📍 Flashcards
Chloroplast definition
site of photosynthesis
organelles in a plant cell
cell wall, vacuole, chloroplast, mitochondria, ribosomes, nucleus, cell membrane, cytoplasm
Reagent used to test for starch
Iodine
What are the plant organs
Stem, root and leaves
what are the tissue layers in a leaf?
• Cuticle
• Upper epidermis
• Palisade mesophyll
• Spongy mesophyll
• Lower epidermis
What tissue layer does photosynthesis occur in?
Palisade mesophyll
What is the cuticle?
• A waxy waterproof, transparent layer
• Reduces water loss during evaporation
• Acts as a layer of protection
What is the upper epidermis?
Transparent layer in order to allow light to be absorbed
Palisade mesophyll tissue layer
Large number of palisade cells are found here to maximise rate of protein synthesis
Adaptation of the spongy mesophyll
Contains air spaces to maximise surface area and increase gas exchange
Function of the guard cells
• Controls the opening and closing of the stomata
• Allows gases to diffuse in or out
• Also allows water vapour to leave
What are the 2 transport vessels in a plant?
Xylem and phloem
Function of xylem
Transports water and dissolved mineral ions
Function of phloem
Transports sucrose (sugar) and amino acids
Endothermic reaction
Chemical reaction where heat is absorbed
Function of roots
Absorb water and nutrients from the soil
Photosynthesis definition
the process by which plants convert sunlight, water, and carbon dioxide into oxygen and glucose.
Autotroph meaning
Plants can make complex molecules (glucose) from simple molecules (co2 and water)
Producer meaning
Organisms (plants) that are able to make their own food and therefore are at the start of all food chains
Word equation for photosynthesis
Carbon dioxide + Water
—> Glucose + Oxygen
Function of glucose in plants
• Produces starch for storage
• Helps with respiration
• Synthesises lipids to provide seeds with energy
• Form cellulose to make cell walls
Function of oxygen in plants
Helps with respiration or it diffuses out
Diffusion definition
Movement of particles from high to low concentration
What is a limiting factor?
Factor that slows down rate of a process (eg photosynthesis)
3 factors that can affect rate of photosynthesis
Temperature, C02 concentration and light intensity
Denatured meaning
When the active site of an enzyme loses its shape and is no longer complementary to the substrate
Pigment found in chloroplasts
Chlorophyll
Factors that affect amount of chloroplasts
Amount of leaves, amount of nutrients, diseases
Equipment that can be used to measure light intensity
Light meter
What is light measured in?
Lux
Why is there a higher concentration of carbon dioxide at night in plants?
there’s a higher rate of respiration as it doesn’t photosynthesise. This produces more carbon dioxide.
How does a high temperature affect the rate of photosynthesis?
Enzymes become denatured [state meaning]
How do low temperatures affect the rate of photosynthesis?
Less kinetic energy is present therefore less collisions occurs between molecules meaning that less reactions happen
What’s the optimum temperature for photosynthesis
25 degrees Celsius
How do guard cells control the opening and closing of the stomata?
When the plant has a sufficient amount of water, the guard cells take in the water and swell (turgid) causing the stomata to open to allow gas exchange.
Inverse square law calculation
1/d² - Light intensity is inversely proportional to distance
Method to measure volume of gas released in photosynthesis
[might come soon]
adaptations of root hair cells
• Absorbs water (by osmosis) and mineral ions (active transport)
• Has extensions to increase its surface area and increase absorption
What organelle do roots hair cells not have and why?
Chloroplast because they are underground and cannot absorb light for photosynthesis
Active transport meaning
An energy requiring process where substances are moved across a cell membrane against their concentration gradient
Osmosis meaning
Movement of water molecules across a semi permeable membrane from a high concentration to low concentration
Direction of flow in xylem
Upwards and unidirectional
Location of xylem in relation to phloem in a vascular bundle
Xylem is on the inside whereas the Phloem is on the outside
function of sucrose
transports amino acids
How is water transported in a plant
Absorbed through osmosis in the root and then up the xylem through transpiration
Define transpiration
The pull of water from the root to the leaves to replace the evaporated water
Monomer of sucrose
Glucose
Function of sodium hydrogen carbonate
Provides plant with Co2 when added to water to support with photosynthesis
Function of protease
Breaks down proteins in cell membrane
adaptations of the xylem
• No end walls (to form hollow tubes for water to be drawn)
• Contains no cytoplasm (for free passage of water)
• Lignin thickens the outer walls (to strengthen tubes)
Adaptations of the phloem
• Cells have few organelles (to aid the flow of sugars and amino acids)
• Cells are joined end to end by sieve plates (forming tubes to allow translocation)
• Small pores in end walls let substances through
Companion cell function
Supports the transport of sugars and amino acids from the leaves to phloem by providing energy
Translocation meaning
Active transport of sugars from leaves into phloem
Direction of flow in phloem
Bidirectional
Xerophytic plant meaning
Plant adapted to survive in extreme conditions
Examples of xerophytic plants
Cacti and Marram grass
Adaptations of xerophytic plants
• stem stores water • stomata opens at night (because it’s cooler and reduces water loss) • hairs on stem (to trap water vapour) • waxy, thick cuticle
Structural adaptations of marram grass in a hot, windy and dry environment
Its leaves roll up to reduce exposure to wind (minimising water loss) • Thick cuticle to reduce water loss • Hairs on inner surface of the leaf (trapping air to reduce water loss)
Plant adaptations of marram grass in a hot, windy and dry environment
• Long thin leaves to reduce air resistance • strong root structure to prevent being uprooted • flexible to avoid breaking (in windy conditions)
Pathway of water in a plant
Root hair cells -> Root cortex cells -> Xylem -> Leaf mesophyll cells
Why does the stomata open during the day?
• Higher light intensity allows for gas exchange (photosynthesis) • which allows water vapour to leave during transpiration
Why does the stomata close during the night?
To conserve water as the rate of transpiration is reduced (photosynthesis can’t occur)
Turgid meaning
Swollen
What happens when water leaves the guard cells?
The guard cells become flaccid • Stomata also closes
Cohesion meaning
When water molecules stick together
Function of transpiration
• Transports mineral ions • Provides water to keep cells turgid for photosynthesis • Keeps leaves cool (water evaporates)
How is the flow of water continuous
Due to the cohesion of water it creates a continuous unbroken column
Factors that affect the rate of transpiration
• Temperature • Light intensity • Air movement • Humidity
How does temperature affect transpiration?
• A higher temperature increases kinetic energy of water molecules • This makes transpiration through evaporation faster
How does light intensity affect transpiration?
• A higher light intensity would increase the rate of photosynthesis by opening more stomata for co2 to diffuse in • This allows more water to evaporate
How does air movement affect transpiration?
• Moving air removes water vapour in the air and increases the concentration gradient • Allows evaporation to happen faster
How does humidity affect transpiration?
• A lot of water vapour in the air reduces the water concentration gradient • This decreases the rate of evaporation
Potometer meaning
Apparatus used to measure the rate of transpiration
Why is the shoot (upper part of plant) cut under water?
To prevent air entering the xylem
Why are the leaves of the shoot dried?
To remove any excess water
Equation to work out the rate of transpiration
Rate = Distance moved by air bubble (m) / Time (min)
How can we reduce leaking in a potometer?
Assemble equipment underwater
Source meaning
Where the products are made