Edexcel Biology GCSE: Cells and Microscopy

Cell Types

• There are two main types of cells: eukaryotic (found in animals and plants) and prokaryotic.

Differences between Eukaryotic and Prokaryotic Cells

• Eukaryotic cells have a nucleus and membrane-bound organelles, while prokaryotic cells do not.

Cell Components

• Both plant and animal cells have five common components: nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes.

Genetic Information Storage

• In eukaryotic cells, genetic information is stored within the nucleus, arranged in chromosomes.
• In prokaryotic cells, genetic information is found free within the cytoplasm as chromosomal DNA (single large loop of circular DNA) and plasmid DNA.

Nuclear Function

• The nucleus controls cellular activities.

Cytoplasm

• Cytoplasm is a fluid component of the cell that contains organelles, enzymes, dissolved ions, and nutrients.
• Its function is to provide a site for cellular reactions, such as the first stage of respiration.

Cell Membrane

• The cell membrane controls the entry and exit of materials into and out of the cell.

Mitochondria

• Mitochondria are responsible for generating energy for the cell.

Permanent Vacuole

• The permanent vacuole supports the cell, maintaining its turgidity.

Chloroplasts

• Chloroplasts are the site of photosynthesis.
• They appear green under a light microscope due to the presence of chlorophyll.

Prokaryotic Cell Organelles

• Prokaryotic cells have six organelles: chromosomal DNA, plasmid DNA, cell wall, cell membrane, ribosomes, and flagella.

Sexual Reproduction

• Sexual reproduction involves the fusion of two haploid gametes, resulting in a diploid embryo with two chromosomes for each gene and two copies of each allele.

Egg Cell Adaptations

• Egg cells are adapted to their function with a haploid nucleus containing genetic material, mitochondria providing energy, cytoplasm containing nutrients, and a hardened cell membrane after fertilization.

Sperm Cell Adaptations

• Sperm cells are adapted to their function with a haploid nucleus containing genetic information, a tail for movement, mitochondria providing energy, and an acrosome containing enzymes that digest the egg cell membrane.

Ciliated Epithelial Cells

• Ciliated epithelial cells are found in the respiratory, reproductive, and digestive systems.

Microscopy

• Electron microscopes are used to observe cells and organelles in detail, enabling scientists to develop more accurate explanations about cell structure and function.
• The disadvantages of electron microscopes include being expensive, large, requiring training to use, and only being able to observe dead specimens.

Unit Conversion

• To convert from meters (m) to millimeters (mm), multiply by 1000.
• To convert from meters (m) to micrometers (μm), multiply by 1,000,000.
• To convert from meters (m) to nanometers (nm), multiply by 1,000,000,000.
• To convert from nanometers (nm) to meters (m), divide by 1,000,000,000.