# GCSE Biology Paper 1 & 2: Cell Biology, Organisation, Enzymes, Bioenergetics, Homeostasis & Inheritance > High-yield GCSE and IGCSE Biology revision covering eukaryotic vs prokaryotic ultrastructure, microscopy equations, mitosis, enzyme lock-and-key denaturation, photosynthesis limiting factors, reflex arcs, hormonal homeostasis, and Mendelian genetics. - **Canonical URL:** https://flashcards.world/flashcards/sets/cc664d6a-426b-473d-a7c6-882e98d33a4e/ - **Markdown URL:** https://flashcards.world/flashcards/sets/cc664d6a-426b-473d-a7c6-882e98d33a4e.md - **Level:** basic - **Languages:** en → en - **Total Cards:** 32 ## Flashcards (32 Cards) | # | Front (Term / Prompt) | Back (Definition / Answer) | Example | Multiple-Choice Options | | :--- | :--- | :--- | :--- | :--- | | 1 | How does active transport differ from diffusion in root hair cells? | Active transport moves mineral ions (such as nitrate and magnesium ions) against their concentration gradient (from dilute soil solution into concentrated root hair cell cytoplasm) using energy released from cellular respiration in mitochondria. | | | | 2 | Describe the step-by-step mechanism of evolution by natural selection (4-mark GCSE template). | 1) Random genetic mutations create phenotypic variation within a population; 2) Individuals with advantageous alleles are better adapted to selection pressures (e.g., predation, disease) and are more likely to survive; 3) Survivors reproduce and pass on the advantageous alleles to offspring; 4) Over many generations, the frequency of the advantageous allele increases. | | | | 3 | Explain the biological sequence of eutrophication when nitrate fertilisers leach into a freshwater lake. | Excess nitrates cause rapid algal growth (algal bloom) on the water surface → blocks sunlight from reaching submerged aquatic plants → submerged plants cannot photosynthesise and die → aerobic saprobionts/decomposers multiply and respire as they decay the dead plants → dissolved oxygen is depleted (anoxia) → fish and aerobic invertebrates suffocate and die. | | | | 4 | How do prokaryotic cells (e.g., bacteria) differ structurally from eukaryotic cells (plant and animal cells)? | Prokaryotic cells are much smaller, lack a true membrane-bound nucleus (DNA is a single circular chromosomal loop free in the cytoplasm plus small rings called plasmids), and lack membrane-bound organelles such as mitochondria or chloroplasts. | | | | 5 | Which three subcellular structures are present in plant palisade mesophyll cells but absent in animal cells, and what are their functions? | 1) Cellulose cell wall: provides structural support and prevents bursting under turgor pressure; 2) Chloroplasts: contain chlorophyll to absorb light for photosynthesis; 3) Permanent vacuole: filled with cell sap to maintain cell turgidity. | | | | 6 | Trace the exact pathway of a nervous impulse through a reflex arc. | Stimulus → Receptor → Sensory neurone → Synapse (chemical neurotransmitter diffuses across cleft) → Relay neurone (in CNS / spinal cord) → Synapse → Motor neurone → Effector (muscle contracts or gland secretes hormone) → Response. | | | | 7 | What are the two main functions of bile in human digestion, and where is it made and stored? | Made in the liver and stored in the gall bladder. 1) It is alkaline, neutralising hydrochloric acid from the stomach to provide the optimum alkaline pH for pancreatic enzymes in the small intestine; 2) It emulsifies fats into tiny droplets, increasing surface area for faster lipase action. | | | | 8 | Why is biomass lost between trophic levels in a food chain (typically only ~10% transferred)? | 1) Not all of the organism is eaten (e.g., bones, roots, cellulose); 2) Unabsorbed material is egested as faeces; 3) Excretory losses (urea, CO2, water); 4) Large amounts of glucose are used in cellular respiration to release energy for movement and maintaining body temperature (lost as heat). | | | | 9 | How does the inverse square law apply to light intensity in the GCSE Pondweed Photosynthesis Required Practical? | Light intensity is inversely proportional to the square of the distance from the light source: I ∝ 1 / d². If the distance between the lamp and pondweed is doubled, the light intensity decreases by a factor of four (quarter of original intensity). | | | | 10 | What are the roles of FSH, Oestrogen, LH, and Progesterone in the human menstrual cycle? | FSH (pituitary): matures an egg follicle in the ovary and stimulates oestrogen release. Oestrogen (ovaries): thickens uterus lining, inhibits FSH, and stimulates LH surge. LH (pituitary): triggers ovulation (release of egg on day 14). Progesterone (corpus luteum): maintains uterus lining and inhibits both FSH and LH. | | | | 11 | Define osmosis in exact GCSE mark-scheme terminology. | Osmosis is the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution) across a partially permeable membrane. | | | | 12 | What is 'oxygen debt' (EPOC) after vigorous exercise and how does the body remove lactic acid? | Oxygen debt is the extra volume of oxygen required after exercise to oxidise accumulated lactic acid. Blood transports lactic acid from muscles to the liver, where it is converted back into glucose (using oxygen) and then stored as glycogen or respired into CO2 and water. | | | | 13 | What are the key biological stages of the carbon cycle? | Photosynthesis removes CO2 from the atmosphere to make plant carbohydrates; feeding passes carbon along food chains; aerobic respiration by plants, animals, and decomposers (microorganisms) returns CO2 to the atmosphere; combustion of fossil fuels or wood also releases CO2. | | | | 14 | In human genetics, if two heterozygous carriers of Cystic Fibrosis (Ff × Ff) have a child, what is the probability the child has Cystic Fibrosis? | 25% (or 1 in 4, or 0.25). Cystic fibrosis is caused by a recessive allele (f). The Punnett square gives genotypes 1 FF (unaffected) : 2 Ff (unaffected carriers) : 1 ff (affected with cystic fibrosis). | | | | 15 | Compare aerobic respiration with anaerobic respiration in human muscle cells and in yeast. | Aerobic (with O2): C6H12O6 + 6O2 → 6CO2 + 6H2O (releases large amount of energy/ATP). Anaerobic in muscles (no O2): Glucose → Lactic acid (causes muscle fatigue and oxygen debt). Anaerobic in yeast/plants (fermentation): Glucose → Ethanol + Carbon dioxide. | | | | 16 | How do vaccinations provide immunity against specific pathogens? | A vaccine introduces a dead, attenuated (weakened), or antigenic fragment of a pathogen, stimulating white blood cells (B-lymphocytes) to produce specific complementary antibodies and memory cells. Upon secondary exposure to the live pathogen, memory cells rapidly produce high concentrations of antibodies before symptoms develop. | | | | 17 | What is the magnification equation used in GCSE Biology microscopy, and how do you convert millimetres (mm) to micrometres (μm)? | Magnification = Image size ÷ Actual (real) size (M = I / A). To convert millimetres (mm) to micrometres (μm), multiply by 1,000 (1 mm = 1,000 μm; 1 μm = 1,000 nm). | | | | 18 | Where are amylase, protease, and lipase produced in the human digestive system, and what are their products? | Amylase (salivary glands, pancreas, small intestine): hydrolyses starch into maltose/glucose. Protease (stomach pepsin, pancreas, small intestine): digests proteins into amino acids. Lipase (pancreas, small intestine): digests lipids into glycerol and 3 fatty acids. | | | | 19 | Explain the 'lock and key' model of enzyme action and what happens during denaturation. | The substrate has a specific 3D shape complementary to the enzyme's active site, binding to form an enzyme-substrate complex. Extreme high temperatures or pH changes break intramolecular bonds, irreversibly changing the 3D shape of the active site so the substrate can no longer fit (denaturation). | | | | 20 | How does auxin control phototropism in plant shoots vs gravitropism in plant roots? | In shoots, auxin accumulates on the shaded side, stimulating cell elongation so the shoot bends towards light (positive phototropism). In roots, auxin accumulates on the lower side due to gravity, where high auxin concentration inhibits cell elongation, causing the root to bend downwards (positive gravitropism). | | | | 21 | Contrast Type 1 and Type 2 diabetes in terms of cause and clinical treatment. | Type 1: Autoimmune destruction of insulin-producing pancreatic beta cells; early onset; treated with regular insulin injections and carbohydrate monitoring. Type 2: Body cells become resistant/insensitive to insulin (linked to obesity/diet); treated with low-carbohydrate diet, regular exercise, and drugs. | | | | 22 | How does ADH (antidiuretic hormone) regulate blood water potential in the kidney nephron (Triple Science)? | When blood water potential is too low (dehydration), osmoreceptors in the hypothalamus signal the pituitary gland to release more ADH. ADH increases the permeability of the kidney collecting ducts, so more water is reabsorbed into the blood by osmosis, producing a small volume of concentrated urine. | | | | 23 | What are the food test reagents and positive colour changes for starch, reducing sugars, proteins, and lipids (GCSE Required Practical)? | Starch: Iodine solution turns orange-brown to blue-black. Reducing sugars (glucose): Benedict's reagent + heat (80°C water bath) turns blue to brick-red precipitate. Protein: Biuret reagent turns blue to purple/lilac. Lipids: Ethanol emulsion test forms a cloudy white emulsion. | | | | 24 | How do xylem and phloem tissues differ in structure and transport mechanism in plants? | Xylem consists of dead, hollow cells strengthened with lignin rings/spirals, transporting water and mineral ions unidirectionally from roots to leaves via the transpiration stream. Phloem consists of living sieve tube elements and companion cells, transporting dissolved sugars (sucrose) bidirectionally via translocation (requiring energy). | | | | 25 | State the balanced symbol equation for photosynthesis and identify whether it is endothermic or exothermic. | 6CO2 + 6H2O → C6H12O6 + 6O2 (in the presence of light and chlorophyll). It is an endothermic reaction because energy is transferred from the environment (light) to chloroplasts. | | | | 26 | How do you estimate the population size of daisies in a field using quadrats (GCSE Ecology Required Practical)? | Generate random coordinates (using a random number generator along two tape measures) to avoid bias, place a quadrat of known area (e.g., 0.25 m² or 1 m²) at ≥10 random locations, count the mean number of daisies per quadrat, and multiply by (Total field area ÷ Quadrat area). | | | | 27 | Explain the stages of genetic engineering used to produce human insulin in bacteria. | 1) Isolate the human insulin gene using a restriction enzyme (creating sticky ends); 2) Cut a bacterial plasmid vector with the same restriction enzyme; 3) Join the insulin gene into the plasmid using DNA ligase enzyme to form recombinant DNA; 4) Insert the recombinant plasmid into host bacteria and culture in industrial fermenters. | | | | 28 | How do insulin and glucagon interact in negative feedback to regulate blood glucose concentration? | When blood glucose is too high, the pancreas secretes insulin, causing liver and muscle cells to absorb glucose and convert it into insoluble glycogen for storage. When blood glucose is too low, the pancreas secretes glucagon, causing liver cells to break down glycogen back into glucose and release it into the blood. | | | | 29 | Compare mitosis and meiosis in terms of chromosome number, divisions, and genetic variation. | Mitosis: 1 division, produces 2 genetically identical diploid (2n = 46 in humans) somatic cells for growth and repair. Meiosis: 2 divisions, produces 4 genetically non-identical haploid (n = 23) gametes (sperm/egg) with half the chromosome number. | | | | 30 | What happens during the three main stages of the eukaryotic cell cycle leading to mitosis? | 1) Interphase (Growth & DNA replication): cell grows, increases subcellular structures (ribosomes, mitochondria), and duplicates DNA to form X-shaped chromosomes; 2) Mitosis: chromosomes line up and are pulled apart to opposite poles; 3) Cytokinesis: cytoplasm and cell membranes divide to form two genetically identical diploid daughter cells. | | | | 31 | Compare the structure and function of arteries, veins, and capillaries in the mammalian circulatory system. | Arteries carry high-pressure blood away from the heart (thick muscular/elastic walls, narrow lumen, no valves except aorta/pulmonary artery). Veins carry low-pressure blood back to the heart (thinner walls, wide lumen, semilunar valves to prevent backflow). Capillaries have one-cell-thick walls for short diffusion pathways. | | | | 32 | What are the four main environmental factors that affect the rate of transpiration in plants? | 1) Temperature (higher temperature increases kinetic energy and evaporation rate); 2) Humidity (lower humidity increases the water vapour concentration gradient); 3) Air movement/wind (blows water vapour away, maintaining a steep gradient); 4) Light intensity (causes guard cells to open stomata for photosynthesis). | | | --- Study this deck interactively with FSRS-6 spaced repetition, audio review, and multiple-choice mode at [Flashcards World](https://flashcards.world/flashcards/sets/cc664d6a-426b-473d-a7c6-882e98d33a4e/).