A&P Ch 3: The Cellular Organization of Life

Name all the parts/organelles of the cell

1. Nucleus

2. Nucleolus

3. Nuclear Envelope

4. Ribosomes

5. Rough ER

6. Smooth Er

7. Golgi Apparatus

8. Mitochondria

9. Lysosomes

10. Peroxisomes

11. Vacuoles

12. Plasma Membrane

13. Cytoplasm/Cytosol

14. Cytoskeleton

15. Centrioles

Function of the Nucleus and Nucleolus

Nucleus: The control center of the cell. Contains the cell's DNA and provides blueprints for all cellular activities.

Nucleolus: Found inside the nucleus; responsible for making ribosomes.

Function of Ribosomes

The protein factories of the cell.

Synthesize proteins by linking amino acids together using genetic code.

Can float freely in the cytoplasm or attach to the Rough ER.

Rough ER vs Smooth ER

Rough ER: Covered in ribosomes; folds and modifies proteins meant for export or membrane use.

Smooth ER: Lacks ribosomes; synthesizes lipids (fats/steroids) and detoxifies drugs and poisons.

Function of the Golgi Apparatus

The "post office" of the cell.

Modifies, sorts, and packages proteins and lipids from the ER into vesicles for transport to their final destination.

Function of Mitochondria

The "powerhouse" of the cell.

Site of cellular respiration; converts energy from food (glucose) into ATP, the cell's usable energy currency.

Function of Lysosomes and Peroxisomes

Lysosomes: The cellular garbage disposal. Contain digestive enzymes to break down waste, old organelles, and foreign invaders.

Peroxisomes: Neutralize dangerous toxins (like hydrogen peroxide and alcohol) and break down fatty acids.

Function of Plasma Membrane and Cytoplasm

Plasma Membrane: A semi-permeable phospholipid bilayer that acts as a gatekeeper, controlling what enters and leaves the cell.

Cytoplasm (Cytosol): The jelly-like fluid filling the cell that suspends and cushions the organelles.

Function of Cytoskeleton and Centrioles

Cytoskeleton: A network of protein fibers that gives the cell its shape and acts as an internal highway for moving items.

Centrioles: Direct cell division by organizing spindle fibers to pull chromosomes apart.

What are the Two Main Processes of Protein Synthesis

Transcription: Rewriting DNA into mRNA. Occurs in the nucleus.

Translation: Decoding mRNA into a protein. Occurs in the cytoplasm at a ribosome.

The Central Dogma: DNA ——→ RNA ——→Protein.

Define DNA

Permanent master blueprint. It contains the specific gene sequence that acts as the template for making a protein.

Define mRNA

Mobile copy of the gene blueprint. It carries the genetic message from the nucleus out to the ribosome.

Define tRNA

The "molecular bridge." It brings the correct amino acid to the ribosome by matching its anticodon to the mRNA's codon.

Define Ribosome

(rRNA): The factory floor. It holds the mRNA and tRNA together and physically links amino acids into a chain.

Explain step-by-step Transcription

1. Unwinding: RNA Polymerase unzips the specific gene section of DNA.

2. Copying: RNA Polymerase matches RNA nucleotides to the DNA template (replacing Thymine with Uracil).

3. Release: The newly formed mRNA strand detaches, exits through a nuclear pore, and enters the cytoplasm.

Explain Translation Step 1

Initiation

The mRNA strand binds to a ribosome in the cytoplasm.

The ribosome reads the mRNA starting at the specific Start Codon (AUG).

The first tRNA molecule arrives, carrying the amino acid Methionine.

Explain Translation Step 2

Elongation

The ribosome reads the next 3-letter mRNA codon.

A matching tRNA brings the corresponding amino acid.

The ribosome forms a peptide bond between the amino acids, building a growing protein chain.

The empty tRNA leaves, the ribosome shifts over, and the process repeats.

Explain Translation Step 3

Termination

The ribosome reaches a Stop Codon (UAA, UAG, or UGA) on the mRNA.

No tRNA matches this code; instead, a release factor binds to the ribosome.

The completed polypeptide (protein) chain is released, and the translation machinery disassembles.

Define Diffusion

The passive movement of particles from an area of high concentration to low concentration.

Driven by natural kinetic energy; requires no cellular energy (ATP).

Goal: Continues until particles are evenly distributed (dynamic equilibrium).

Define Mitosis

A process of nuclear division where a single somatic (body) cell divides to produce two genetically identical daughter cells.

Purpose: Essential for growth, tissue repair, and asexual reproduction.

Stages: Prophase, Metaphase, Anaphase, Telophase (PMAT).

Define Apoptosis

Programmed cell death ("cellular suicide").

A clean, controlled process where a cell shrinks, fragments, and is quietly removed by immune cells.

Purpose: Eliminates old, damaged, or unneeded cells without harming surrounding tissue (e.g., losing the webbing between fingers during embryonic development).

Define Necrosis

Unprogrammed, accidental cell death caused by external injury, infection, toxins, or lack of oxygen/blood flow.

The cell swells and bursts, spilling its contents into surrounding tissue.

Outcome: Always triggers a harmful inflammatory response in the body.

Define Cellular Differentiation

The process by which an unspecialized stem cell becomes a specialized cell type with a specific structure and function.

How it works: All cells keep the exact same DNA, but they turn specific genes "on" or "off."

Example: A stem cell differentiating into a dedicated heart muscle cell, skin cell, or red blood cell.