Biology Chapter 3 - Cell Biology

Study Notes

Cells are the basic units of all living organisms.
Two main types of cells: Eukaryotic (with nucleus) and Prokaryotic (without nucleus).

Metabolism and energy use: Cells perform biochemical processes to generate energy.
Synthesis of molecules: Cells create essential compounds for function and structure.
Communication: Cells interact and send signals to each other.
Reproduction and inheritance: Cells reproduce and pass genetic material to the next generation.

Light Microscopes: Allow observation of general cell features.
Electron Microscopes: Reveal fine structures.
- Scanning Electron Microscope (SEM): Observes surface features.
- Transmission Electron Microscope (TEM): Shows detailed internal structures.

Cilia: Cylindrical projections for movement; 10 μm long and 0.2 μm in diameter.
Flagella: Longer than cilia at 45 μm; primarily found on sperm cells.
Microvilli: Not for movement; enhance absorption, found in intestines and kidneys.

Cytoplasm: Gel-like substance containing all organelles, excluding the nucleus.
Cytosol: Fluid portion of the cytoplasm, includes cytoskeleton and inclusions.
Cytoskeleton: Composed of microtubules, actin filaments, and intermediate filaments; provides structural support and facilitates movement.

Nucleus: Largest organelle; contains the cell's DNA and acts as the control center.
- Contains chromosomes, chromatin, nucleoplasm, nuclear envelope, nucleolus, and nuclear pores.
Ribosomes: Sites of protein synthesis located in the cytosol or attached to membranes.
Endoplasmic Reticulum (ER): Network of membranes; two types:
- Rough ER: Studded with ribosomes, involved in protein synthesis.
- Smooth ER: Lacks ribosomes, synthesizes lipids, detoxifies substances, and stores calcium ions.
Golgi Apparatus: Processes, packages, and distributes materials within the cell.

Lysosomes: Contain digestive enzymes; responsible for breaking down waste and foreign material.
Mitochondria: Powerhouse of the cell; site of cellular metabolism and energy production.
Peroxisomes: Contain enzymes for detoxification, especially in the liver and kidney.

Structure: Composed of 45-50% lipids, 45-50% proteins, and 4-8% carbohydrates.
Function: Selectively permeable barrier that regulates material transport in and out of the cell.

Membrane Potential: Electrical charge difference across the membrane due to ion regulation.
Membrane Proteins: Include integral and peripheral proteins, serving roles in transport, signaling, and support.

Diffusion: Movement of solutes from high to low concentration.
- Simple Diffusion: Direct movement through the lipid bilayer.
- Facilitated Diffusion: Involves carrier proteins for polar substances.
Osmosis: Diffusion of water across a semipermeable membrane, influenced by osmotic pressure and tonicity (isotonic, hypertonic, hypotonic).

Primary Active Transport: Direct use of ATP to move substances against a concentration gradient.
Secondary Active Transport: Utilizes the movement of one substance to drive the transport of another.
Vesicular Transport: Movement of large volumes using vesicles (includes endocytosis and exocytosis).

Gene Expression: Process of producing RNA and proteins from DNA, consisting of:
- Transcription: DNA is transcribed into RNA.
- Translation: RNA is translated into proteins.

G1 Phase: Cell growth and preparation for DNA replication.
S Phase: DNA replication occurs.
G2 Phase: Cell prepares for mitosis, replenishes energy, and duplicates organelles.

Mitosis Stages:
- Prophase: Chromosomes condense; nuclear membrane dissolves.
- Metaphase: Chromosomes align at the cell center.
- Anaphase: Chromosomes are pulled apart to opposite poles.
- Telophase: Nuclear membrane reforms; cell readies for division.
Cytokinesis: Final step where cytoplasm divides, forming two new cells.