Biological Molecules
A positive Biuret test confirms the presence of which type of biological molecule?
Protein
Which blood vessel layer is first damaged during atherosclerosis?
Endothelium
Which molecule carries amino acids to the ribosome?
tRNA
Which protein is defective in cystic fibrosis?
CFTR
Which tissue transports sucrose?
Phloem
A triglyceride is hydrolysed completely. What three molecules are produced in the greatest number?
Fatty acids
Why does plaque formation increase the risk of thrombosis?
It promotes clot formation
What feature allows a tRNA molecule to recognize a codon?
Its anticodon
Why is mucus unusually thick in cystic fibrosis?
Less water enters the mucus
Why are xylem vessels lignified?
To prevent collapse
Why do phospholipids spontaneously form bilayers in water?
Their hydrophobic tails avoid water
A coronary artery narrows from 4 mm to 2 mm diameter. Which parameter decreases most dramatically?
Blood flow rate
A mutation changes one base in DNA but not the amino acid produced. Why?
The genetic code is degenerate
A person has one normal and one mutant CFTR allele. What is their genotype description?
Heterozygous
A plant wilts despite moist soil. Which process is most likely exceeding water uptake?
Transpiration
Two proteins have identical primary structures but different functions. Which level of structure must differ?
Tertiary structure
Why can hypertension accelerate atherosclerosis?
It increases endothelial damage
Why might a nonsense mutation have a larger effect than a missense mutation?
It causes premature termination
Why is cystic fibrosis more common in populations with higher rates of consanguinity?
Recessive alleles are more likely to pair
Why do guard cells become turgid when stomata open?
Water enters by osmosis
A membrane protein contains many non-polar amino acids in the region embedded within the membrane. Why?
Non-polar side chains interact with phospholipid tails
A patient has normal oxygen saturation but ischemic heart tissue. What is the most likely explanation?
Reduced coronary blood flow
A ribosome reaches a stop codon. Which molecule does not bind next?
tRNA
A screening programme identifies carriers rather than affected individuals. What is its main purpose?
Informing reproductive decisions
A mutant lacks companion cells. Which transport process is most directly affected?
Translocation