Cell Biology Concepts

Key Terms & Concepts

• Selectively Permeable: Only certain molecules are able to pass through cell membranes.
• Fluid Mosaic: The cell membrane resembles a "fluid soup" where proteins float within a lipid layer.
• Hydrophilic: Describes substances that are water-loving (polar).
• Hydrophobic: Describes substances that avoid water (non-polar).
• Amphipathic: Molecules, such as phospholipids, that possess both water-loving and water-fearing regions.
• Glycocalyx: A sugar-rich layer on a cell's surface that provides protection and aids in cell recognition.
• Concentration Gradient: The difference in solute concentration that drives diffusion.
• Resting Membrane Potential: The electrical charge difference across a cell membrane when the cell is inactive.

The Three Parts of a Cell

• Cell Membrane: Regulates the movement of substances into and out of the cell.
• Cytoplasm: Contains organelles and the cytoskeleton within the cell.
• Nucleus: Contains the genetic material in eukaryotic cells.

Cell Membrane Composition & Function

• Phospholipids form the basic bilayer structure of the cell membrane, possessing a hydrophilic head and a hydrophobic tail.
• Glycolipids are lipids with sugar groups that aid in cell recognition.
• Cholesterol regulates the fluidity of the cell membrane.
• Peripheral proteins are attached to the membrane surface and function in signaling or structural support.
• Integral/Transmembrane proteins span the entire membrane and act as channels or carriers.
• Glycoproteins are proteins with sugar chains attached.

Cell Junctions

• Desmosomes provide strong cell-to-cell adhesion.
• Gap junctions allow small molecules and signals to pass between cells.
• Tight junctions seal cells together to prevent unwanted passage of materials.

Transport Mechanisms

• Simple Diffusion: Substances move from an area of high concentration to an area of low concentration without energy.
• Facilitated Diffusion: Utilizes channels or carriers to transport specific molecules across the membrane.
• Primary Active Transport: Uses ATP directly, like the sodium-potassium pump.
• Secondary Active Transport: Uses ion gradients to transport molecules (symporters and antiporters).
• Endocytosis: The process of bringing substances into the cell.
• Exocytosis: The process of releasing substances out of the cell.
• Receptor-Mediated Endocytosis: Specific uptake of substances using receptors.
• Pinocytosis: "Cell drinking".
• Phagocytosis: "Cell eating".

Osmosis & Tonicity

• Osmosis: Water moves towards areas with higher solute concentrations.
• Hypertonic: Higher solute concentration outside the cell, causing the cell to shrink.
• Hypotonic: Lower solute concentration outside the cell, causing the cell to swell, potentially leading to bursting.
• Isotonic: Equal solute concentration inside and outside the cell, resulting in no net change in cell size.

Cytoplasm & Organelles

• Cytosol: The fluid component inside the cell.
• Organelles: Specialized structures within the cell that perform specific functions.
• Cytoskeleton: Provides structure to the cell and aids in movement.
• Mitochondria: Produces ATP.
• Ribosomes: Synthesizes proteins.
• Rough ER: Involved in protein production and modification.
• Smooth ER: Involved in lipid production and detoxification.
• Golgi Complex: Packages and ships proteins and lipids.
• Lysosomes: Used for waste digestion.
• Peroxisomes: Breaks down fats and detoxifies harmful substances.

Cytoskeleton & Cellular Extensions

• Microtubules: Facilitate transport within the cell and are involved in cell division.
• Intermediate Filaments: Provide strength and help maintain cell shape.
• Microfilaments: Involved in cell movement.
• Cilia: Short, hair-like structures that move fluids.
• Microvilli: Increase surface area for absorption.
• Flagella: Long structures that help with cell movement.

Nucleus

• Chromatin: DNA wrapped around proteins; condenses to form chromosomes.
• Nucleolus: Produces ribosomes.

Cell Cycle & DNA Replication

• Interphase:
• G1 Phase: The cell grows.
• S Phase: DNA is replicated.
• G2 Phase: Final preparations for cell division occur.
• Mitosis: Division of the nucleus into two identical cells, consisting of prophase, metaphase, anaphase, and telophase.
• Cytokinesis: Division of the cytoplasm, resulting in two separate cells.
• DNA Replication: It is semiconservative, each new DNA molecule include one original and one newly synthesized strand.

Test your knowledge of cell biology. This quiz covers topics such as tonicity, organelles, cell cycle, and cell membrane structure. See how well you understand these fundamental concepts.