WJEC GCSE Biology 1.1 Cells and Movement Across Cell Membranes Exam Questions

About WJEC GCSE Biology 1.1 Cells and Movement Across Cell Membranes

This is the opening topic of WJEC GCSE Biology and the foundation for most of Unit 1. You need to know the structures in plant and animal cells, how to view cells with a light microscope, and how cells are organised into tissues, organs and organ systems. The topic then covers how substances cross membranes by diffusion, osmosis and active transport, and how enzymes work. These ideas return in gas exchange, digestion, root uptake and kidney function. Examiners like labelled cell diagrams, explanations of osmosis using Visking tubing or potato data, and graphs of enzyme activity against temperature or pH.

What you need to know

• Cell structures Animal and plant cells both have a cell membrane, cytoplasm, nucleus and mitochondria. Plant cells also have a cellulose cell wall, chloroplasts and a large permanent vacuole. Know the function of each, e.g. mitochondria are where aerobic respiration releases energy.
• Microscopy and organisation Prepare and observe animal and plant cells with a light microscope and draw labelled diagrams (a specified practical). Cells differentiate into specialised cells; similar cells form tissues, tissues form organs and organs form organ systems.
• Diffusion The net movement of particles from a high to a low concentration, down a concentration gradient. It is passive, needing no energy from respiration, and is how oxygen and carbon dioxide cross cell membranes. Visking tubing is used as a model of a living membrane.
• Osmosis The diffusion of water through a selectively permeable membrane from a dilute solution (high water concentration) to a more concentrated solution (low water concentration).
• Active transport Movement of substances against a concentration gradient, from low to high concentration, using energy from respiration and carrier proteins in the membrane, e.g. mineral ion uptake by root hair cells.
• Enzymes Enzymes are proteins that act as biological catalysts. Each has an active site with a specific shape that fits its substrate (lock and key model), forming an enzyme-substrate complex. High temperatures and extremes of pH change the shape of the active site, so the enzyme is denatured. Investigating factors affecting enzyme action is a specified practical.

Common mistakes in 1.1 Cells and Movement Across Cell Membranes

• Saying water moves from a high to a low concentration of solution in osmosis. Water moves from a dilute solution to a more concentrated solution, which is from a high to a low concentration of water.
• Writing that enzymes are killed at high temperature. Enzymes are not alive; they are denatured because the active site changes shape and the substrate no longer fits.
• Describing active transport without mentioning energy or the direction. Always say it moves substances against a concentration gradient using energy from respiration.
• Labelling the cell wall as the structure that controls what enters the cell. The cell membrane controls entry and exit; the cellulose cell wall only gives support.

Try three 1.1 Cells and Movement Across Cell Membranes exam-style questions