Key Concepts in Biology - Edexcel Biology GCSE

Overview

This document provides detailed notes on the first topic of Edexcel Biology GCSE, covering key concepts like cell functions, specialized cells, microscopy, enzyme action, and cell transport.

1.1 - Eukaryotic and Prokaryotic Cell Functions

• Eukaryotic Cells: Found in animals and plants, include organelles like the nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes.
• Prokaryotic Cells: Found in bacteria, smaller, include cell wall, cell membrane, cytoplasm, single DNA strand, and plasmids.
• Organelles: Structures with specific functions within cells.

1.2 - Specialized Cells and Their Functions

• Differentiation: Process where cells gain new structures to perform specific roles.
• Specialized Animal Cells:
  • Sperm cells: Streamlined for swimming, many mitochondria, digestive enzymes in acrosome.
  • Egg cells: Specialized membrane, large cytoplasm, many mitochondria.
  • Ciliated epithelial cells: Cilia to move bacteria trapped in mucus.
• Specialized Plant Cells:
  • Root hair cells: Large surface area, mitochondria for active transport.
  • Xylem cells: Transport water, lignin causes them to become hollow.
  • Phloem cells: Transport photosynthesis products; rely on companion cells for energy.

1.3 - Microscopy

• Light Microscopes: Max magnification ~2000x, resolving power 200nm.
• Electron Microscopes: Use electrons, greater magnification (up to 2,000,000x). Types:
  • Scanning Electron Microscope (SEM) for 3D images.
  • Transmission Electron Microscope (TEM) for detailed 2D images.
• Allowed discovery and study of viruses and proteins.

1.4 & 1.5 - Size, Scale, and Units

• Magnification Calculation: Eyepiece lens magnification x Objective lens magnification.
• Standard Form: Useful for very large/small numbers.
• Order of Magnitude: Comparing sizes.
• Estimations: Useful in biology for counting large populations.

1.6 - Core Practical: Investigating Biological Specimens

• Microscope Use: Know parts and steps (focus wheel, magnification).
• Slide Preparation: Use thin cell layers and chemical stains.
• Magnification Calculation: Measured size / Actual size.

1.7, 1.8, and 1.9 - Enzymes

• Function: Biological catalysts that speed up reactions without being used up.
• Lock and Key Hypothesis: Specificity of enzymes to substrates.
• Denaturation: Loss of enzyme function due to changes in temperature/pH.
• Factors Affecting Enzymes: Optimal temperature, pH, and substrate concentration.

1.10 - Core Practical: Effect of pH on Enzyme Activity

• Amylase Experiment: Observing starch breakdown with iodine.
• Control Variables: Maintaining constant temperature.

1.11 - Rate Calculations

• Formula: Rate = Change / Time
• Example: Calculation of enzyme activity rate using protease.

1.12 - Enzymes as Biological Catalysts

• Types of Enzymes:
  • Carbohydrases: Convert carbohydrates to sugars.
  • Proteases: Convert proteins to amino acids.
  • Lipases: Convert lipids to fatty acids and glycerol.

1.13B - Core Practical: Investigating Macronutrients

• Food Tests: Identifying starch, sugars, proteins, and lipids using chemical reactions.

1.14B - Calorimetry

• Measuring Energy: Used to measure calories in food by observing temperature changes in water.

1.15 - Transport in and Out of Cells

• Diffusion: Passive transport from high to low concentration.
• Osmosis: Water movement across a membrane from dilute to concentrated solution.
• Active Transport: Requires energy to move substances against a gradient.

1.16 - Core Practical: Osmosis in Potatoes

• Experiment: Observing osmosis by measuring mass change in potato disks.
• Variables: Independent (sucrose concentration), Dependent (potato mass change).