IB Biology HL Exam Review Questions and Answers | Latest Version | 2025/2026 | Correct & Verified

IB Biology HL Exam Review Questions and Answers | Latest Version | 2025/2026 | Correct & Verified What is cell theory? All living organisms are made of cells, cells are the basic unit of life, and cells arise from pre-existing cells Which microscope allows viewing of living cells? Light microscope What type of microscope has the highest resolution? Electron microscope What limits the size of cells? Surface area to volume ratio Why do cells divide when they grow too large? To maintain efficient exchange with the environment What structure surrounds all cells? Plasma membrane 2 What are phospholipids arranged as in membranes? A bilayer Which part of a phospholipid is hydrophobic? Fatty acid tails Which part of a phospholipid is hydrophilic? Phosphate head What model describes membrane structure? Fluid mosaic model What is the role of membrane proteins? Transport, signaling, and cell recognition What is facilitated diffusion? Passive movement through membrane proteins What does active transport require? ATP energy What organelle modifies and packages proteins? 3 Golgi apparatus Where are proteins synthesized? Ribosomes What type of ribosome attaches to rough ER? Bound ribosomes What is the function of rough endoplasmic reticulum? Protein synthesis and transport What is the function of smooth endoplasmic reticulum? Lipid synthesis and detoxification What organelle contains digestive enzymes? Lysosome What is the function of mitochondria? ATP production Why do mitochondria have folded inner membranes? To increase surface area for respiration 4 What is the inner membrane of mitochondria called? Cristae What is the fluid inside mitochondria called? Matrix What is the function of chloroplasts? Photosynthesis What pigment absorbs light in chloroplasts? Chlorophyll Where are thylakoids located? Inside chloroplasts What structure connects plant cells? Plasmodesmata What organelle provides structure in plant cells?