Cell Structure

Summary

All living cells have a basic structure including a cell membrane, cytoplasm, nucleus, mitochondria, and ribosomes. Plant cells additionally have a cell wall, chloroplast, and a large central vacuole.

• Cell Membrane — Envelops the cell contents and controls what enters and leaves the cell.
  Example: Selectively permeable to certain molecules.
• Nucleus — Contains DNA which codes for proteins controlling cell activities.
  Example: Control center of the cell.
• Cytoplasm — Gel-like liquid part of the cell where cellular reactions occur.
  Example: Site of chemical reactions.
• Mitochondrion — Organelle for aerobic respiration, providing energy.
  Example: Powerhouse of the cell.
• Ribosomes — Structures for protein synthesis, can be free or attached to ER.
  Example: Site of protein synthesis.
• Cell Wall — Supports and strengthens plant cells, made from cellulose.
  Example: Provides rigidity to plant cells.
• Vacuole — Stores water and sugars in plant cells.
  Example: Contains cell sap.
• Chloroplast — Organelle for photosynthesis in plant cells.
  Example: Contains chlorophyll for capturing light energy.

Exam Tips

Key Definitions to Remember

• Cell membrane: selectively permeable barrier
• Nucleus: control center containing DNA
• Cytoplasm: site of chemical reactions
• Mitochondrion: site of aerobic respiration
• Ribosomes: site of protein synthesis
• Cell wall: provides support and structure in plant cells
• Chloroplast: site of photosynthesis in plant cells

Common Confusions

• Confusing cell wall with cell membrane
• Thinking all cells have chloroplasts

Typical Exam Questions

• What is the function of the mitochondrion? It is the site of aerobic respiration and energy production.
• How do plant and animal cells differ? Plant cells have a cell wall, chloroplasts, and a large vacuole, unlike animal cells.
• What is the role of ribosomes? They are the site of protein synthesis.

What Examiners Usually Test

• Differences between plant and animal cells
• Functions of cell organelles
• Identification of cell structures in diagrams