paper 1 bio

Question

Answer

What is the difference between DNA and RNA?

DNA is double-stranded, stable, and stores genetic information. RNA is single-stranded, shorter, and helps with protein synthesis (mRNA, tRNA, rRNA).

How does DNA replicate?

Semi-conservative replication using DNA helicase (unwinds), free nucleotides (pair with bases), and DNA polymerase (joins nucleotides).

How do enzymes work?

Enzymes reduce activation energy by forming enzyme-substrate complexes. Their active site is specific to substrates.

How do temperature and pH affect enzymes?

Extreme temperature/pH denatures enzymes, altering their active site shape, preventing substrate binding.

How do inhibitors affect enzyme activity?

Competitive inhibitors block the active site

What food tests are used in biology?

Benedict’s (sugar), Biuret (protein), Emulsion (lipids), Iodine (starch).

How is colorimetry used?

Measures concentration of solutions based on light absorption/transmission (e.g., Benedict’s test).

How do prokaryotic and eukaryotic cells differ?

Prokaryotes lack a nucleus, have small ribosomes, and a simple structure

What are key eukaryotic organelles?

Rough ER (protein transport), Golgi (modifies/packages proteins), lysosomes (digest waste), mitochondria (ATP production).

What’s the difference between optical and electron microscopes?

Optical = lower resolution, views live cells

What is cell fractionation and ultracentrifugation?

Separates organelles based on density using homogenisation, filtration, and spinning.

What happens in the cell cycle?

G1 (growth), S (DNA replication), G2 (preparation), Mitosis (cell division).

How does binary fission work?

Prokaryotes duplicate DNA and split into two daughter cells.

What is the fluid mosaic model?

Membranes consist of phospholipids, proteins, cholesterol, and glycoproteins for selective transport.

What factors affect membrane permeability?

Temperature, alcohol, and lipid composition alter phospholipid structure.

How do temperature/alcohol affect membranes?

Break phospholipid bilayer, increasing permeability (tested using beetroot practical).

How do non-specific immune defences work?

Skin, phagocytosis, lysozymes in tears break pathogens.

How does the specific immune response work?

T-cells activate B-cells, which produce antibodies

How do vaccines work?

Contain weakened antigens, triggering memory cell response for future immunity.

What is herd immunity?

High vaccine rates protect unvaccinated individuals by limiting disease spread.

How do monoclonal antibodies work?

Artificial antibodies bind to specific antigens for disease diagnosis and treatment (e.g., ELISA).

What ethical concerns exist with vaccines?

Animal testing, safety trials, informed consent issues.

Why don’t antibiotics work on viruses?

Viruses lack metabolism, so antibiotics can’t target them.

How does HIV replicate?

HIV binds to T-helper cells, inserts RNA, uses reverse transcriptase to produce viral DNA, weakening immunity.

How do drugs treat disease?

Antivirals block viral replication

Question

Answer

What are monomers?

Monomers are small units that bond to form larger molecules. Examples include monosaccharides (carbohydrates), amino acids (proteins), and nucleotides (DNA/RNA).

How does a condensation reaction work?

A condensation reaction joins two molecules by forming a bond and removing a water molecule, linking monomers into polymers.

What are carbohydrates used for?

Carbohydrates serve as an energy source (glucose), energy storage (glycogen/starch), and structural support (cellulose in plants).

How does lipid structure relate to function?

Triglycerides store energy efficiently due to long hydrocarbon tails, provide metabolic water upon breakdown, and are insoluble, preventing osmotic imbalance.

What makes proteins unique?

Proteins consist of amino acids linked by peptide bonds, forming primary, secondary, tertiary, and quaternary structures for diverse roles like enzymes, antibodies, and transport proteins.

How is DNA structured?

DNA is a double-stranded helix composed of nucleotides with complementary base pairing (A-T, C-G), allowing genetic storage and replication.

What is the role of ATP?

ATP is the universal energy carrier, releasing energy in small, manageable amounts by hydrolysing its phosphate bonds.

How does water support life?

Water is a solvent, a metabolite in biochemical reactions, has high specific heat capacity for stable environments, and enables cohesion for transpiration in plants.

How do membranes control transport?

The phospholipid bilayer regulates transport via diffusion, osmosis, and active transport, using carrier and channel proteins to move substances.

Why is mitosis important?

Mitosis produces genetically identical cells for growth and repair, ensuring the continuity of genetic information across generations.

How do viruses reproduce?

Viruses lack cellular machinery, so they inject genetic material into host cells, forcing them to produce viral particles.

What is facilitated diffusion?

Movement of molecules across a membrane via protein channels/carriers, without ATP, down a concentration gradient.

How do antibodies fight pathogens?

Antibodies bind antigens to neutralise pathogens, stimulating immune responses like agglutination for easier phagocytosis.