Fundamentals:
All living things are composed of cells.
Cells are the basic unit of structure and function.
New cells arise from existing cells.
Light Microscopes:
Samples can be alive.
Uses light and lenses to magnify images.
Requires dyes or fluorescent labels for visibility.
Electron Microscopes:
Samples must be dead and chemically fixed.
Uses electrons for high magnification.
Two types:
Scanning Electron Microscopy (SEM): Surface examination.
Transmission Electron Microscopy (TEM): Examines thin cross-sections.
General Features:
Enclosed by a membrane.
Contains cytoplasm, which includes water, salts, ions, macromolecules, and organelles.
Organelles:
Specialized components that perform specific functions.
Can be membrane-bound or non-bound.
Types of Cells:
Prokaryotes: Smaller, lack a nucleus.
Eukaryotes: Larger, possess a nucleus.
Cell Wall: Provides structure and protection (plants).
Chloroplast: Site of photosynthesis (plants).
Central Vacuole: Stores materials and helps maintain cell structure (plants).
Nucleus: Contains DNA; controls cellular activity.
Ribosomes: Sites of protein synthesis.
Endoplasmic Reticulum (ER):
Rough ER: Synthesizes proteins.
Smooth ER: Synthesizes lipids; detoxifies.
Mitochondrion: Produces ATP through cellular respiration.
Golgi Body: Modifies and sorts proteins and lipids for secretion.
Lysosomes: Digest waste materials.
Maintenance of homeostasis through selective permeability.
Transport proteins and vesicles are used for materials that cannot pass freely.
Passive Transport:
Does not use energy; moves substances down the concentration gradient.
Diffusion: Movement from high to low concentration.
Facilitated Diffusion: Requires special proteins for larger molecules.
Osmosis: Diffusion of water through selectively permeable membranes.
Active Transport:
Uses energy; moves substances against their concentration gradient.
Protein Pumps: Transport ions using ATP.
Bulk Transport: Vesicles move large molecules in/out of cells;
Endocytosis: Materials into the cell.
Exocytosis: Materials out of the cell.
Organisms maintain a relatively stable internal environment.
Unicellular Organisms: Grow, respond to stimuli, and reproduce independently.
Multicellular Organisms: Specialized cells that communicate and collaborate for overall organism function.
Levels of Organization:
Atoms → Molecules → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere
Chemical Signals: Cells communicate through chemical signals and proteins.
Cell Junctions: Physical connections facilitating communication between cells.
Receptor Proteins: Translate external signals into cellular responses, altering cellular activity based on the stimulus.