CH 6 Pearson guide from Study Guide

Cell Structure and Function

Introduction

This study guide covers essential concepts in cell biology, focusing on cell theory, cell structure, and the differences between prokaryotic and eukaryotic cells. It also addresses the endosymbiotic theory and the functions of major organelles.

The Cell Theory

• Definition: The cell theory is a fundamental principle in biology stating that all living organisms are composed of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.

• Key Points:

  • All organisms are made of one or more cells.

  • The cell is the basic unit of structure and function in living things.

  • All cells come from pre-existing cells.

• Example: Both Escherichia coli (a bacterium) and human cells follow the cell theory.

Surface Area to Volume Ratio

• Definition: The surface area to volume ratio (SA/V) is a measure that affects the efficiency of transport of materials into and out of the cell.

• Key Points:

  • As cell size increases, the SA/V ratio decreases.

  • Smaller cells have a higher SA/V ratio, allowing for more efficient exchange of materials.

  • Limits cell size due to transport and metabolic constraints.

• Formula:

• Example: Bacterial cells are small to maximize their SA/V ratio for efficient nutrient uptake.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotic Cells:

  • Lack a nucleus and membrane-bound organelles.

  • DNA is located in the nucleoid region.

  • Examples: Bacteria and Archaea.

  • Cell structures include: cell wall, plasma membrane, ribosomes, flagella, pili, and sometimes plasmids.

  • Shapes: spirillum, coccus, bacillus.

• Eukaryotic Cells:

  • Contain a nucleus and membrane-bound organelles (e.g., mitochondria, chloroplasts).

  • Examples: plant, animal, fungal, and protist cells.

  • Cell structures include: plasma membrane, nucleus, nucleolus, endoplasmic reticulum, Golgi apparatus, mitochondria, lysosomes, peroxisomes, cytoskeleton, and in plants, chloroplasts and cell wall.

• Comparison Table:

Major Cell Structures and Organelles

• Plasma Membrane: Semi-permeable barrier controlling entry and exit of substances.

• Nucleus: Contains genetic material (DNA); site of transcription.

• Nucleolus: Site of ribosome synthesis.

• Ribosomes: Sites of protein synthesis; found in both prokaryotes and eukaryotes.

• Endoplasmic Reticulum (ER):

  • Rough ER: Studded with ribosomes; involved in protein synthesis and processing.

  • Smooth ER: Lacks ribosomes; involved in lipid synthesis and detoxification.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

• Lysosomes: Contain digestive enzymes for breaking down macromolecules.

• Peroxisomes: Break down fatty acids and detoxify harmful substances.

• Mitochondria: Site of cellular respiration and ATP production; present in animal and plant cells.

• Chloroplasts: Site of photosynthesis; found in plant cells.

• Central Vacuole: Large storage organelle in plant cells; maintains cell turgor.

• Cytoskeleton: Network of protein filaments providing structural support and facilitating cell movement.

• Centrioles: Involved in cell division in animal cells.

Endosymbiotic Theory

• Definition: The endosymbiotic theory proposes that eukaryotic cells originated through a symbiotic relationship between primitive eukaryotes and certain prokaryotes.

• Key Points:

  • Mitochondria and chloroplasts are believed to have evolved from free-living bacteria engulfed by ancestral eukaryotic cells.

  • Evidence includes double membranes, their own DNA, and similarities to prokaryotic cells.

• Example: Mitochondria in animal cells share similarities with aerobic bacteria.

Functions of Major Organelles (Matching)

Additional info:

• Cells in muscle tissue require high concentrations of ATP, which is produced by mitochondria through cellular respiration.

• Plant cells contain unique structures such as chloroplasts, a large central vacuole, and a cell wall, which are not found in animal cells.