Cell Biology Overview

Definition: Study of the structure, function, and behavior of cells, the basic units of life.

Prokaryotic Cells:
- Lack a nucleus and membrane-bound organelles.
- Example: Bacteria.
- Genetic material is circular DNA.
Eukaryotic Cells:
- Contain a nucleus and membrane-bound organelles.
- Example: Plant and animal cells.
- Genetic material is linear, organized in chromosomes.

Nucleus:
- Contains genetic material (DNA).
- Site of transcription (DNA to RNA).
Mitochondria:
- Powerhouse of the cell.
- Site of ATP production through cellular respiration.
Ribosomes:
- Sites of protein synthesis.
- Can be free in the cytoplasm or attached to the endoplasmic reticulum.
Endoplasmic Reticulum (ER):
- Rough ER: Studded with ribosomes; synthesizes proteins.
- Smooth ER: Lacks ribosomes; synthesizes lipids and detoxifies.
Golgi Apparatus:
- Modifies, sorts, and packages proteins and lipids for secretion or delivery to organelles.
Lysosomes:
- Contain digestive enzymes for breaking down waste materials and cellular debris.
Chloroplasts (in plant cells):
- Site of photosynthesis.
- Contain chlorophyll, which captures light energy.
Cell Membrane:
- Phospholipid bilayer that regulates what enters and exits the cell.
- Contains proteins, cholesterol, and carbohydrates.

Metabolism:
- All chemical reactions occurring within a cell, including catabolism (breaking down molecules) and anabolism (building up molecules).
Cell Division:
- Process of cell reproduction.
- Mitosis (somatic cells) and meiosis (gametes).
Cell Communication:
- Cells communicate through chemical signals (hormones, neurotransmitters).
- Receptors on cell membranes receive signals and elicit responses.

Transport Mechanisms:
- Passive Transport: Movement without energy (e.g., diffusion, osmosis).
- Active Transport: Movement requiring energy (e.g., sodium-potassium pump).
Cell Cycle:
- Phases: Interphase (G1, S, G2), Mitosis, Cytokinesis.
- Regulation by checkpoints and cyclins.
Apoptosis:
- Programmed cell death, essential for development and maintenance of healthy tissues.

ATP (Adenosine Triphosphate):
- Main energy currency of the cell.
- Produced during cellular respiration, primarily in mitochondria.
Photosynthesis (in plants):
- Conversion of light energy into chemical energy (glucose).
- Occurs in chloroplasts.
- Equation: 6CO2 + 6H2O + light energy -> C6H12O6 + 6O2.

DNA Replication:
- Process of copying DNA before cell division.
- Semi-conservative mechanism.
Gene Expression:
- Process of converting genetic information into functional products, typically proteins.
- Involves transcription and translation.

Three Main Tenets:
1. All living organisms are composed of cells.
2. The cell is the basic unit of life.
3. All cells arise from pre-existing cells.

Study focuses on structure, function, and behavior of cells, the fundamental units of life.

Prokaryotic Cells:
- Do not possess a nucleus or membrane-bound organelles.
- Genetic material is organized as circular DNA.
- Example includes bacteria.
Eukaryotic Cells:
- Contain a nucleus and various membrane-bound organelles.
- Genetic material is linear and organized into chromosomes.
- Examples include plant and animal cells.

Nucleus:
- Houses genetic material (DNA).
- Primary site for transcription (conversion of DNA to RNA).
Mitochondria:
- Known as the powerhouse of the cell.
- Responsible for ATP production via cellular respiration.
Ribosomes:
- Sites for protein synthesis.
- Can be found free in the cytoplasm or bound to the endoplasmic reticulum.
Endoplasmic Reticulum (ER):
- Rough ER: Characterized by ribosomes; involved in protein synthesis.
- Smooth ER: Lacks ribosomes; involved in lipid synthesis and detoxification.
Golgi Apparatus:
- Modifies, sorts, and packages proteins and lipids.
- Prepares materials for secretion or delivery to specific organelles.
Lysosomes:
- Contain digestive enzymes for breaking down waste and cellular debris.
Chloroplasts (specific to plant cells):
- Sites for photosynthesis.
- Contain chlorophyll for capturing light energy.
Cell Membrane:
- Comprised of a phospholipid bilayer that regulates entry and exit of substances.
- Includes proteins, cholesterol, and carbohydrates.

Metabolism:
- Encompasses all chemical reactions in the cell, including catabolism and anabolism.
Cell Division:
- Essential for reproduction; includes mitosis (for somatic cells) and meiosis (for gametes).
Cell Communication:
- Cells utilize chemical signals (such as hormones and neurotransmitters) for communication.
- Receptors on cell membranes respond to these signals.

Transport Mechanisms:
- Passive Transport: Movement across membranes without energy (e.g., diffusion and osmosis).
- Active Transport: Requires energy for transportation (e.g., sodium-potassium pump).
Cell Cycle:
- Consists of phases: Interphase (G1, S, G2), Mitosis, and Cytokinesis.
- Regulated by checkpoints and proteins known as cyclins.
Apoptosis:
- Programmed cell death; critical for tissue development and homeostasis.

ATP (Adenosine Triphosphate):
- Serves as the primary energy currency of the cell.
- Generated mainly in mitochondria during cellular respiration.
Photosynthesis (in plants):
- Conversion of light energy to chemical energy in the form of glucose.
- Takes place in chloroplasts, following the equation: 6CO2 + 6H2O + light energy -> C6H12O6 + 6O2.

DNA Replication:
- Involves copying of DNA prior to cell division using a semi-conservative mechanism.
Gene Expression:
- Process of translating genetic information into proteins through transcription and translation.

Three Main Tenets:
- All living organisms are made up of cells.
- The cell is the smallest unit of life.
- New cells arise only from pre-existing cells.