General Structure of Eukaryotic Cells

Introduction

• Eukaryotic cells are one of the two main categories of living organisms.
• Examples include animals, plants, and fungi.
• The other category is prokaryotes, which include bacteria and archaea.
• This lecture focuses on eukaryotic cells.

Key Features of Eukaryotic Cells

Nucleus

• Eukaryotic cells have DNA contained within a membrane-bound nucleus.
• "Membrane-bound" means surrounded by a membrane.
• The nucleus often has a double membrane structure.
• Most eukaryotic cells maintain their nucleus throughout their lifespan, except some like human red blood cells.

DNA Structure

• DNA in eukaryotic cells is wrapped around proteins known as histones.
• This combination of DNA and histones forms chromosomes.
• Chromosomes allow efficient packing of DNA within the nucleus.
• Eukaryotic DNA is linear, meaning the DNA strands do not connect end-to-end to form loops.

Organelles

• Eukaryotic cells have several membrane-bound organelles:
  • Mitochondria
  • Golgi apparatus
  • Endoplasmic reticulum
  • Chloroplasts (in plant cells)
  • Vacuoles (in plant cells)
• These organelles perform various essential functions.

Ribosomes

• Eukaryotic cells contain ribosomes that are not membrane-bound.
• Involved in protein synthesis.
• Larger than ribosomes in prokaryotes, termed as 80S ribosomes.
• "S" indicates a unit of measure based on sedimentation rate during centrifugation.

Cell Surface Membrane

• Eukaryotic cells are enclosed by a cell surface membrane.
• It controls the movement of molecules in and out of the cell.

Cell Wall

• Present in plant and fungal cells, but not in animal cells.
• Provides structural support.
• Plant cell walls are made of cellulose.
• Fungal cell walls are made of chitin.

Next Steps

• The next video will cover the key features of prokaryotic cells.