Biology: Cell Structure and Function

Cell Size and Structure

• Cells are small because their volume increases faster than their surface area.
• Small cells more efficiently move nutrients and waste.
• Cell size is limited by surface area-to-volume ratio, material movement, and DNA efficiency.

Cell Cycle

• S phase: DNA replicates.
• Mitosis: The nucleus divides.
• Cytokinesis: The cell divides into two.

Cell Theory

• All living things are made of cells.
• Cells are the fundamental unit of life.
• New cells arise from existing cells.

Cell Types

• Plant cells have a cell wall and chloroplasts.
• Animal cells do not have these structures.
• Both plant and animal cells contain cell membranes and mitochondria.

Cell Membrane

• Made of fats with water-loving heads and water-fearing tails.
• Controls what enters and exits the cell.

Protein Production

• Ribosomes synthesize proteins.
• The Golgi apparatus packages proteins.

Evolution and Natural Selection

• Species change over time due to natural selection.
• Example: Birds with longer beaks survive if food is deep in trees.

Speciation

• Geographic isolation occurs when a barrier separates a group.
• Reproductive isolation develops when groups stop interbreeding.

Mutations

• Mutations are changes in DNA.
• Mutations drive evolution by creating variation.

Darwin's Observations

• Island animals resemble mainland relatives but adapt to their new environments.

Classification and Characteristics of Life

• Scientific names (e.g., Felis catus) classify organisms.
• Archaea and bacteria are single-celled, with differences in cell walls.
• Characteristics common to all life forms:
  • Composed of cells.
  • Respond to surroundings.
  • Grow, reproduce, and use energy.
• Kingdom distinctions:
  • Animals move and cannot produce their own food.
  • Plants remain stationary and generate food using sunlight.