Cell Biology
What is the function of the cell membrane in terms of transport?
Controls movement of substances in and out of the cell
What is translocation in plants?
Movement of sugars through the phloem
What is the role of haemoglobin in red blood cells?
Binds to oxygen to transport it around the body
What is the difference between a dominant and recessive allele?
Dominant is expressed if present; recessive only if both alleles are recessive
What is meant by a trophic level?
The position an organism occupies in a food chain
Why do cells with a larger surface area to volume ratio exchange substances more efficiently
There is more surface area available per unit volume for diffusion
What is the role of stomata in gas exchange?
They allow CO₂ in and O₂ out, controlled by guard cells
How does enzyme specificity relate to its active site?
The active site has a specific shape complementary to the substrate
What is a mutation?
A random change in DNA sequence
What role do decomposers play in ecosystems?
They break down dead material and recycle nutrients
What is osmosis?
Movement of water across a partially permeable membrane from high to low water concentration
Why does increasing temperature only increase photosynthesis up to a point?
Enzymes involved denature at high temperatures
What is the difference between aerobic and anaerobic respiration?
Aerobic uses oxygen and releases more energy; anaerobic does not and releases less
Why is genetic variation important for natural selection?
It provides differences that may give survival advantages
Why do pyramids of biomass decrease at higher trophic levels?
Less energy is available at each level due to losses
What happens to cells in a hypotonic solution?
Water enters by osmosis, increasing pressure until the cell lyses
Why is magnesium deficiency harmful to plants?
Magnesium is needed to make chlorophyll, so photosynthesis decreases
Why do arteries have thick muscular walls?
To withstand and maintain high pressure from the heart
What is speciation?
The formation of new species due to reproductive isolation
What is eutrophication?
Nutrient enrichment causing algal blooms and oxygen depletion
Why is active transport important in the small intestine?
It allows absorption of nutrients (like glucose) against a concentration gradient using energy
Which plan hormone is responsible for stimulating stem elongation, seed germination, and flowering?
Gibberellins
How does the structure of alveoli maximise gas exchange?
Large surface area, thin walls, and good blood supply
How can antibiotic resistance develop in bacteria?
Mutations give resistance, and resistant bacteria survive and reproduce
How much energy is passed between trophic layers in a food chain?
10%