this funny test (student taught content) Flashcards
What are the adaptations of leaves for gas exchange? (5)
- Large surface area
- Thin structure
- Stomata
- Air spaces in spongy mesophyll
- Moist surfaces
These adaptations increase the efficiency of gas diffusion and exchange in leaves.
List the parts of a transverse section of a dicotyledonous leaf. (5)
- Upper epidermis
- Palisade mesophyll
- Spongy mesophyll
- Vascular bundle (xylem and phloem)
- Lower epidermis (with stomata)
Understanding the structure helps in studying plant physiology.
Outline the process of transpiration. (3)
- Water evaporates from spongy mesophyll
- Water vapor diffuses out through stomata
- Water is drawn up from xylem to replace it
Transpiration is essential for nutrient transport and temperature regulation.
What factors affect the rate of transpiration? (5)
- Light
- Temperature
- Humidity
- Wind
- Stomatal density
Each factor influences the evaporation rate and gas exchange.
How do you determine stomatal density?
Use clear nail polish on leaf underside, peel when dry, place on slide, count stomata in a known field of view
This method allows for a quantitative assessment of stomatal distribution.
What are the mechanisms of seed dispersal? (4)
- Wind
- Water
- Animals
- Mechanical
Different plants utilize various methods to ensure species propagation.
What are the requirements for seed germination? (4)
- Water
- Oxygen
- Temperature
- (Some seeds also require light/darkness)
Each requirement activates essential biological processes for growth.
Explain how water is transported from roots to leaves. (3)
- Water enters roots by osmosis
- Moves into xylem
- Pulled up by transpiration pull, aided by cohesion, adhesion, and root pressure
This process is crucial for maintaining plant hydration and nutrient transport.
Outline the adaptations of xylem vessels for water transport. (4)
- Lignified walls
- No end walls
- No cytoplasm
- Narrow tubes
These adaptations minimize resistance and enhance water flow.
What changes occur to plant tissues in hypotonic and hypertonic solutions?
- Hypotonic: Cell becomes turgid
- Hypertonic: Plasmolysis occurs
These changes affect cell structure and function significantly.
Define the term water potential.
Water potential (Ψ): The tendency of water to move
Pure water has a potential of 0; more negative values indicate lower potential.
In what direction does water move in terms of water potential?
From higher (less negative) to lower (more negative) water potential
This movement is essential for plant hydration.
How do solute and pressure potentials affect water potential? (3)
- Ψ = Ψs (solute) + Ψp (pressure)
- Solutes lower Ψ
- Turgor pressure raises Ψ
Understanding these potentials is key to grasping plant physiology.
Explain the effects of hypotonic and hypertonic solutions using solute and pressure potentials.
- Hypotonic: Ψp increases (turgid cell)
- Hypertonic: Ψp drops, Ψs dominates (plasmolysis)
These effects are critical in understanding osmotic balance.
How is root pressure generated in xylem vessels? (2)
- Active transport of ions into xylem lowers Ψ
- Water follows by osmosis
This process contributes to the upward movement of water in plants.
Outline adaptations of phloem sieve tubes and companion cells for translocation. (2)
- Sieve tubes: No nucleus, perforated end walls
- Companion cells: Dense cytoplasm, many mitochondria
These adaptations facilitate efficient transport of nutrients.
Describe transcription as RNA synthesis using DNA as a template. (3)
- RNA polymerase binds to promoter
- DNA strands separate
- RNA strand synthesized
Transcription is a vital step in gene expression.
What is hydrogen bonding and complementary base pairing in transcription? (2)
- A–U, T–A, G–C, C–G pairing
- Hydrogen bonds form between complementary bases
This ensures accurate RNA synthesis.
How does DNA remain stable and unchanged during transcription? (3)
- Only one strand is used
- DNA rewinds after RNA synthesis
- DNA is not consumed
This stability is crucial for genetic fidelity.
What is the role of transcription in gene expression? (2)
- Specific genes are transcribed in specific cells
- Controls protein production
This process determines cell function and identity.
Explain post-transcriptional modification of mRNA in eukaryotes. (3)
- Capping (5’ cap)
- Poly-A tail (3’)
- Splicing: Introns removed, exons joined
These modifications enhance mRNA stability and translation efficiency.
How does alternative splicing produce protein variants? (2)
- Exons can be included/excluded
- Leads to different mRNA
This process allows a single gene to code for multiple proteins.
Describe translation as using mRNA to synthesize polypeptides. (3)
- mRNA binds to ribosome
- tRNA brings amino acids
- Ribosome joins amino acids
Translation is the final step in protein synthesis.
What are the roles of mRNA, ribosomes, and tRNA in translation? (3)
- mRNA: Template with codons
- tRNA: Brings amino acids
- Ribosome: Site of protein synthesis
Each component plays a critical role in assembling proteins.
