Cell Biology: Structure to Systems

Compound Light Microscope:
- Uses objective and eyepiece lenses.
- Total magnification = objective lens power \times eyepiece lens power.
- Maximum clear magnification: approx. x1000.
Electron Microscopes:
- Use a beam of electrons instead of light.
- Provide much higher magnification (up to x250000 and higher) and clarity.
- Transmission Electron Microscope (TEM): Sends electrons through a thin specimen, showing internal ultrastructure.
- Scanning Electron Microscope (SEM): Provides a surface view of the specimen.

Animal Cells:
- Cell (Plasma) Membrane: Outer boundary.
- Protoplasm: All living parts, includes nucleus and cytoplasm.
- Cytoplasm: Jelly-like substance where reactions occur, outside the nucleus.
- Nucleus: Control center.
- No cell wall or large vacuole.
Plant Cells:
- Cell Wall: Rigid outer layer made of cellulose, for strength and support.
- Cell Membrane: Just inside the cell wall.
- Vacuole: Large, fluid-filled (cell sap), gives strength/shape, stores materials.
- Cytoplasm and Nucleus present.
- Chloroplasts: (in green plants) Sites of photosynthesis.

Prokaryotic Cells:
- No nucleus; circular DNA loop not membrane-enclosed.
- No membrane-enclosed organelles (e.g., mitochondria, chloroplasts).
- Small and single-celled.
- Examples: Bacteria.
Eukaryotic Cells:
- Have a nucleus (DNA enclosed by a membrane).
- Have membrane-enclosed organelles (e.g., mitochondria, chloroplasts).
- Large cells.
- Examples: Animals, plants, fungi.

Cell (Plasma) Membrane:
- Composed of phospholipid bilayer and proteins.
- Functions: Retains cell contents, recognizes molecules, selectively permeable (controls entry/exit).
Nucleus:
- Control center, surrounded by a double membrane with nuclear pores.
- Contains DNA arranged into chromosomes (elongated as chromatin when not dividing).
- Genes: Sections of DNA that instruct protein synthesis, units of inheritance.
- Nucleolus: Dark-staining area within nucleus, makes ribosomes.
Cytoplasm:
- Jelly-like liquid suspending organelles.
Mitochondria:
- Sites of respiration, supply energy.
- Double membrane with inner infoldings (cristae) for increased surface area.
- Contain their own loop of DNA.
Chloroplasts (Plants Only):
- Sites of photosynthesis.
- Double membrane, contain membrane stacks with chlorophyll.
- Contain their own loop of DNA.
Ribosomes:
- Tiny structures made of RNA and protein.
- Function: Make proteins by combining amino acids.

Definition: Group of similar cells adapted to carry out specific function(s).
Plant Tissues:
- Dermal Tissue (e.g., Epidermis): Outer covering, protects the plant.
- Vascular Tissue (Xylem & Phloem): Transports materials (water/minerals via xylem, food via phloem).
Animal Tissues:
- Connective Tissue: Joins and supports structures (e.g., blood, bone, fat).
- Nervous Tissue (Neurons): Carries electrical impulses to/from brain and spinal cord.

Definition: Growth of cells/tissues outside the body in a sterile nutrient medium.
Micropropagation:
- Growing large numbers of genetically identical plants from small plant pieces.
Applications:
- Cancer Research: Producing monoclonal antibodies (MABS) to detect/target cancer cells.
- Skin Grafts: Growing new skin for burn patients from stem cells.

Definition: Structure composed of multiple tissues working together for one or more functions.
Plant Organs: Roots, stems, leaves, flowers, seeds, fruits.
- Example (Leaf): Contains dermal, vascular, and ground tissues for photosynthesis.
Animal Organs: Stomach, brain, lungs, liver, kidney, heart.
- Example (Heart): Contains muscular, epithelial, connective, and nervous tissues to pump blood.

Definition: Number of organs working together to carry out one or more functions.
Examples (Animal):
- Circulatory System: Heart, blood vessels, blood; transports materials and fights infection.
- Digestive System: Mouth, esophagus, stomach, intestines; breaks down food and absorbs nutrients.