Bio 160- Inside the Cell

What is the path of protein production in a cell?

DNA → RNA → Protein.
mRNA leaves the nucleus → binds ribosomes on the rough ER → protein enters the ER lumen to fold and be processed → moves to the Golgi apparatus (cis → trans) for tagging and sorting → transported in vesicles → to plasma membrane, lysosome, or secretion

What is the endomembrane system?

The network of membrane-bound organelles that produce, process, and transport proteins, lipids, and carbohydrates.
Includes ER, Golgi apparatus, and lysosomes

How are proteins sorted and sent to the correct destination?

Proteins get molecular “tags” in the Golgi.
Receptors recognize these tags → vesicles bud off → cytosolic and membrane proteins guide them to fuse at specific destinations (membrane, lysosome, etc.)→ vesicles deliver contents

What organelles are found in eukaryotic cells and what do they do?

• Nucleus: Stores DNA, makes ribosomes.

• Rough ER: Synthesizes and folds proteins.

• Smooth ER: Lipid synthesis, detoxification.

• Golgi apparatus: Sorts, modifies, ships molecules.

• Lysosome: Digestion/recycling (animals).

• Mitochondria: ATP synthesis.

• Peroxisome: Breaks down toxins.

• Chloroplast (plants): Photosynthesis.

• Vacuole (plants): Storage & turgor.
  Plant cells have cell wall, chloroplasts, and vacuole; animal cells have centrioles and lysosomes

What are key differences between eukaryotic and prokaryotic cells?

• Eukaryotes: Have nucleus & organelles, linear DNA, larger, complex.

• Prokaryotes: No nucleus, DNA in nucleoid, circular DNA, smaller, simpler.
  Eukaryotic cytoplasm is compartmentalized; prokaryotic is not

What genetic elements do prokaryotes have?

• Chromosome: Circular DNA with proteins.

• Plasmids: Small circular DNA molecules carrying extra genes (e.g., antibiotic resistance).
  DNA in prokaryotes is supercoiled and circular, not linear

Are there any “generalized” cells?

No. Cells are specialized for specific functions (e.g., muscle cells for contraction, neurons for signaling). Specialization allows multicellular organisms to perform diverse, coordinated functions efficiently

How do prokaryotes perform respiration or photosynthesis without organelles?

They use infoldings of the plasma membrane containing enzymes for electron transport or photosynthesis. These membrane folds act like internal organelles for energy transformation

What are isotonic, hypotonic, and hypertonic solutions?

• Isotonic: Equal solute concentration → no net water movement.

• Hypotonic: Lower solute outside → water enters cell → swelling.

• Hypertonic: Higher solute outside → water leaves cell → shrinkage.
  Cells maintain homeostasis by controlling osmotic balance.

What are facilitated diffusion, passive, and active transport?

• Passive diffusion: Molecules move down concentration gradient; no energy.

• Facilitated diffusion: Uses channel or carrier proteins, no energy.

• Active transport: Moves substances against gradient using ATP or ion gradients.

• Water enters via osmosis (aquaporins).

• Glut1 transporter: A carrier protein that changes shape to move glucose down its gradient into the cell