#Cell Structure: Your Ultimate AP Biology Review 🔬

Hey there, future AP Bio master! Let's dive into the cell, the fundamental unit of life. This guide is designed to be your go-to resource for a quick, effective review, especially the night before the exam. We'll break down everything you need to know, with a focus on clarity and key concepts.

#Cell Components: The Building Blocks of Life

Cells are complex, but they're also incredibly organized. Let's explore the main players:

# Plasma Membrane: The Gatekeeper 🚪

• Phospholipid Bilayer: The foundation of the membrane. Remember, it's a double layer with:
  • Hydrophilic Heads: Love water, point outwards.
  • Hydrophobic Tails: Fear water, tucked inside.
• Fluid Mosaic Model: The membrane is flexible and has various proteins embedded within it.
• Membrane Proteins: Act as transporters for molecules that can't pass through the hydrophobic core.

Phospholipid bilayer structure. Note the hydrophilic heads and hydrophobic tails.

# Nucleus: The Control Center 🧠

• The Brain: Directs all cellular activities.
• Genetic Information (DNA): Responsible for reproduction.
• Nucleolus: Where ribosomes are assembled.

# Ribosomes: The Protein Factories 🏭

• Made of rRNA and protein.
• Site of Translation: Synthesize proteins based on mRNA sequences.
• Free Ribosomes: In the cytosol, make proteins for use within the cell.
• Bound Ribosomes: Attached to the rough ER, make proteins for export.

# Endoplasmic Reticulum (ER): The Manufacturing Hub 🛠️

• Smooth ER:
  • Lipid synthesis
  • Carbohydrate metabolism
  • Detoxification
  • Calcium storage
• Rough ER:
  • Has ribosomes attached (hence, "rough")
  • Secretes proteins made by bound ribosomes
  • Proteins are moved to transitional ER and packaged into transport vesicles

The rough and smooth endoplasmic reticulum. Note the ribosomes on the rough ER.

# Golgi Apparatus: The Packaging and Shipping Center 📦

• Modifies, stores, and ships proteins from the rough ER.
• Modifies glycoproteins.
• Cis Face: Entry point for vesicles.
• Trans Face: Exit point for vesicles.
• Packages proteins into vesicles for transport to their final destinations.
• Involved in lysosome production.

# Mitochondria: The Powerhouse 🔥

• Double Membrane: Outer membrane (smooth) and inner membrane (folded).
• Cristae: Folds of the inner membrane, increase surface area for the electron transport chain.
• Mitochondrial Matrix: Site of the Krebs cycle.
• ATP Production: Generates energy via cellular respiration.
• Has its own circular DNA, suggesting an evolutionary origin as a separate organism.

Mitochondrial structure, showing the outer membrane, inner membrane, cristae, and matrix.

# Lysosomes: The Recycling and Cleanup Crew 🗑️

• Contain hydrolytic enzymes to break down molecules.
• Acidic Interior: Essential for enzyme function.
• Phagocytosis: Engulfs and digests nutrients.
• Recycles old or damaged cell parts.
• Apoptosis: Programmed cell death (the lysosome bursts, killing the cell).

# Vacuoles: The Storage Units 📦

• Large vesicles for storage of food, water, and other materials.
• Contractile Vacuoles: Pump water out of cells (in some unicellular eukaryotes).
• Central Vacuole: Large water storage in plant cells.

# Chloroplast: The Photosynthesis Site ☀️

• Double Membrane: Like mitochondria.
• Chlorophyll: Green pigment for absorbing light.
• Stroma: Fluid-filled space inside the chloroplast.
• Thylakoids: Flat, membrane-bound sacs where light absorption occurs.
• Photosynthesis: Converts light energy into chemical energy.

# Centrioles: The Cell Division Helpers ➗

• Cylindrical structures active during cell division.
• Produce microtubules to pull chromosomes apart.

#Plant vs. Animal Cells: Key Differences 🌿 🆚 🐾

• Cell Wall:
  • Plant Cells: Have a rigid cell wall made of cellulose for protection.
  • Animal Cells: Lack a cell wall.
• Centrioles:
  • Animal Cells: Have centrioles.
  • Plant Cells: Do not have centrioles.

#Prokaryotic Cells: The Simplest Form 🦠

• No nucleus or membrane-bound organelles (like lysosomes or Golgi).
• Have a flagella for movement.
• Essentially a capsule with DNA and ribosomes.

Be able to distinguish between prokaryotic, plant, and animal cells on the AP exam. Look for key identifiers like cell walls, centrioles, and presence of a nucleus.

#Quick Comparison Table

#Quick Quiz: Eukaryotic vs. Prokaryotic

Can you identify which cell is eukaryotic and which is prokaryotic? Look for key components!

Image courtesy of Flickr.

Image courtesy of Wikipedia.org.

💥

💥

💥

💥

💥

💥

Answer: First picture is eukaryotic, second picture is prokaryotic.

#Final Exam Focus 🎯

• High-Priority Topics: Cell membrane structure, organelle functions, differences between cell types.
• Common Question Types:
  • Multiple choice questions on identifying organelles and their functions.
  • Free-response questions requiring you to explain the roles of different organelles in cellular processes.
  • Questions comparing and contrasting prokaryotic and eukaryotic cells, and plant vs. animal cells.
• Time Management: Quickly identify the question type and focus on the key terms. Don't get bogged down in details you don't need.
• Common Pitfalls: Confusing organelle functions, misidentifying cell types, not connecting structure to function.

#Practice Questions

Practice Question

#Multiple Choice Questions

1. Which of the following structures is NOT found in prokaryotic cells? (A) Ribosomes (B) Cell membrane (C) Nucleus (D) Cytoplasm

2. The primary function of the Golgi apparatus is to: (A) Synthesize proteins (B) Produce ATP (C) Modify and package proteins (D) Store water and ions

3. Which organelle is responsible for the programmed cell death (apoptosis)? (A) Endoplasmic reticulum (B) Lysosome (C) Mitochondria (D) Vacuole

#Free Response Question

Describe the structure and function of the mitochondria, and explain how its structure is directly related to its function in cellular respiration. Include a discussion of the inner and outer membranes, cristae, and matrix. (10 points)

Scoring Breakdown:

• Structure (4 points):
  • 2 points for mentioning the double membrane (outer and inner).
  • 1 point for mentioning cristae (folds of the inner membrane).
  • 1 point for mentioning the matrix (space within the inner membrane).
• Function (3 points):
  • 1 point for stating that mitochondria are the site of cellular respiration.
  • 1 point for stating that mitochondria produce ATP.
  • 1 point for mentioning the Krebs cycle occurs in the matrix and electron transport chain occurs in the cristae.
• Structure-Function Relationship (3 points):
  • 1 point for explaining that the folded cristae increase surface area.
  • 1 point for explaining that increased surface area allows for more electron transport chains.
  • 1 point for explaining that more electron transport chains result in increased ATP production.