Week 22 Flashcards
(25 cards)
Why do plants need transportation systems?
To move water from roots to leaves:
Required for photosynthesis.
Provides cellular turgidness.
To move sugars from leaves to other cells:
Required for cellular respiration (ATP production).
Needed for starch storage in roots for long-term energy storage.
What are the vascular tissue types in plants and their functions?
Xylem tissue:
Moves water and water-soluble materials up from roots through stems into leaves.
Phloem tissue:
Transports sugars from photosynthetic material (source) to respiring tissues or roots (sink).
Flow in xylem is upwards.
Flow in phloem is multi-directional.
How is water moved through the xylem?
Xylem consists of narrow tubes that move water and dissolved minerals via capillary action.
Xylem cells lack nucleus, ribosomes, and other organelles to increase volume and ease water movement.
External structure made of lignin rings/spirals that:
Prevent xylem collapse.
Allow stretching and bending during growth.
Small gaps in lignin allow water to spread into neighboring tissues.
What is capillary action in plant xylem?
Intermolecular forces (hydrogen bonds and ion-dipole) cause water molecules to stick together.
Chains of water molecules move together.
Water absorbed from the soil moves through the stems to leaves.
Water is used for photosynthesis or lost via transpiration.
What roles does water movement from roots to leaves serve?
Fuels photosynthesis:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Provides substrate for other reactions.
Enables mass flow of minerals and co-enzymes.
Maintains and regulates osmotic pressure.
Cools the plant and prevents photosynthetic overheating.
How are ions and minerals transported within root cells?
Water absorbed by osmosis is transported by osmotic pressure.
Minerals, ions, and nutrients are absorbed via active transport using ATP hydrolysis.
Root cells maintain ion concentrations 10,000x higher than soil concentrations, preventing passive diffusion.
How do water and minerals enter the xylem from root cells?
Water and minerals move between root cells to reach the nearest xylem branch.
Ions/minerals actively transported into xylem using ATP hydrolysis.
Alters osmotic pressure to control water volume entering xylem.
Endodermal cells around xylem are surrounded by suberin and lignin (Casparian strip), forcing water to move through cells (controlled osmosis).
What processes help water move up the stem against gravity?
Root pressure: Active transport of minerals into xylem creates an osmotic gradient.
Capillary action: Bonds between water/solutes allow chains to move via tension upwards.
Transpiration pull: Evaporation from leaf cells reduces hydrostatic pressure, pulling water upward.
Why is balancing water loss important in plants, and how is it achieved?
Transpiration (~90% of water loss) is necessary for gas exchange (O₂/CO₂).
Adaptations:
Waxy (hydrophobic) cuticle on the upper leaf surface prevents non-stomatal evaporation.
Stomata on underside reduce direct heating evaporation.
Stomata close during peak heat or night when photosynthesis isn’t occurring.
Deciduous plants lose leaves in colder months to conserve water.
What are xerophyte adaptations for living in dry conditions?
Sunken stomata and leaf hairs create local humidity to reduce air currents.
Thicker waxy cuticle reduces evaporation.
Fewer stomata per leaf.
Broad, shallow root systems to quickly absorb water.
What are hydrophyte adaptations for living in water or humid areas?
Reduced or absent waxy cuticles.
Increased number of stomata, often always open.
Stomata located on the upper leaf surface to maximize gas exchange.
Smaller root systems.
How is translocation of photosynthetic sugars organized seasonally?
Summer:
Source: Photosynthesis in leaf material.
Sink: Respiring tissues and roots (starch storage).
Winter:
Source: Breakdown of starch in roots.
Sink: Maintenance of respiring tissues and development of new leaves in spring.
Describe the cellular mechanism of translocation of photosynthetic sugars .
H⁺ ions are pumped from companion cells into photosynthetic cells using ATP.
Sucrose binds to H⁺ ions and is co-transported back into companion cells.
Sucrose is actively loaded into the phloem sieve tubes.
This loading lowers water potential, causing water to enter by osmosis, generating pressure.
Sucrose moves in bulk flow toward sink tissues (e.g. roots) for storage or respiration.
What are the physical barriers of the immune system?
Skin: epithelial cells are tightly connected; skin contains keratin.
Mucous: catches pathogens.
Cilia: maintain flow out of the body.
Chemical defences: lysozyme in sweat breaks down bacterial cell walls.
What is the role of blood clotting (coagulation) in the immune system?
Plugs gap in damaged blood vessel wall.
Maintains the physical barrier.
Reduces spread of infection.
Prevents blood loss.
What regulates clotting and why must clotting be tightly controlled?
Clotting is tightly regulated to prevent unnecessary clotting.
Why?
Blood clots can travel through the blood and cause strokes (brain) or heart attacks.
What is Haemophilia and how does it affect blood clotting?
Genetic disease where clotting factor VIII is not produced.
Blood does not clot properly.
Sex-linked inheritance (on X chromosome).
What happens during the body’s “alarm system” response?
Inflammation: first response to tissue damage.
Signs: Redness, Heat, Swelling, Pain.
Histamine is produced by damaged tissue cells and basophils.
Increases inflammation.
Attracts white blood cells.
What is phagocytosis and which cells perform it?
Phagocytosis is carried out by white blood cells:
Neutrophils.
Macrophages (Phagocytes).
Major histocompatibility proteins bind to the phagocyte surface in response to bacterial proteins.
What are examples of long-term defence mechanisms of the immune system?
Antibodies can pass through the placenta to the fetus.
Breastmilk contains antibodies.
How do vaccinations help the immune system?
Vaccinations help develop memory cells to build up immunity.
Insert dead or weakened pathogen into the body.
Stimulate the same immune response as the disease.
Lead to production of pathogen-specific antibodies and memory cells.
Most vaccinations are by injection, but some are oral and absorbed through the intestine lining.
Why is it important to match blood groups during a transfusion?
Red blood cells (RBCs) express antigens on their surfaces.
A person needs to be given blood from a donor with the same blood type to avoid immune reaction.
Which blood groups are the universal donor and universal recipient?
Universal donor: Blood group O.
Universal recipient: Blood group AB.
What happens when the immune system over-functions?
Auto-immune diseases: immune cells cannot distinguish between host cells and pathogens, or cannot distinguish between “safe” cells and pathogens.
Example: Type I diabetes.
