Microscope Types and Functions

The Microscope

• Biologists use microscopes as a tool to study living organisms.
• Microscopes reveal the secrets of cells.
• Magnification makes things look bigger.
• Resolution is the ability to distinguish between two separate points.
• Resolving power affects how much detail a microscope can show.
• The limit of resolution for optical light microscopes is approximately 200 nanometers (1 nm = 1 × 10⁻⁹ m), while the human eye can only resolve down to about 0.1 mm (1 mm = 1 × 10⁻² m).
• Electron microscopes increase detail because they use an electron beam.
• Electron microscopes demonstrate greater resolving power than light microscopes, allowing objects 0.3 nm apart to be seen separately.

Types & Functions of Microscopes

• Light microscopes are beneficial in viewing biological specimens, typically slides of cells, tissues, or organisms, often treated and stained, and also living materials directly.
• Stains are essential for enhancing visibility of particular cells/parts.
• Staining kills cells.
• Living cells are not as easy to view.
• Specimens in light microscopes are placed on the stage and illuminated.
• Light passes through the specimen and lenses, creating a magnified, upside down, right to left image at the eyepiece.
• To calculate the magnification of a specimen multiply the magnification of the objective lens by the magnification of the eyepiece lens.
• A light compound microscope uses two lenses, the eyepiece and the objective, allowing it to produce more efficient magnification.
• Living specimens can be seen directly with light microscopes.
• Light microscopes can be used without electricity.
• Light microscopes are small and can be moved.
• Resolving power in light microscopes is limited by wavelength.
• Living cells cannot be magnified as much as dead tissue, which limits what we can learn from living cells.

Preparing Slides

• Using a mounted needle, gently lower the cover slip to avoid trapping air bubbles, which show up as black ringed circles.
• To look at cells, start with the lowest power objective lens.
• It is important that mounted tissue should be a single later thick, with NO air bubbles.

Electron Microscope

• Electron microscopes use an electron beam to form an image, rather than relying on light.
• Electron microscope resolving power is improved as wavelength decreases.
• Specimens for an electron microscope are fixed, stained, and thinly sliced, similarly to preparations for light microscopes, however, the materials and stains that are used differ.
• Electron beams are focused with magnetic lenses.
• The final image is captured on a television screen, called an electron micrograph.
• It is impossible to look at living material using an electron microscope
• Electron microscopes take up a lot of space.
• Only dead tissue can be used with electron microscopes.

The cell

• Cells are the basic structural and functional units found in all living organisms.
• Cell theory says cells are the fundamental units of life.
• All living organisms have their own characteristics, which they carry out with either one cell or millions.
• The seven life processes are nutrition, respiration, excretion, growth, irritability, movement, and reproduction.
• Plant and animal cells contain a nucleus, cell membrane, mitochondria, ribosomes, endoplasmic reticulum, and cytoplasm.
• Organelles contain enzymes and chemicals.

Cell structures & functions

• The nucleus controls all the activity of a cell, containing the instructions for making all new organisms in the form of chromosomes.
• Cytoplasm is a liquid gel where chemical reactions happen.
• The cell membrane is a barriers around the outside of the cell that controls which substances pass through.
• The Mitochondria is the cells' powerhouse.
• Endoplasmic reticulum is a 3D system of tubules that spreads throughout the cytoplasm.
• Ribosomes are needed for protein synthesis.

Functions of plant cells

• Cell walls are made of the carbohydrate cellulose, which strengthens the cell.
• The cell wall contains large hols that allow substances to move freely through it.
• Chloroplasts are found in green parts of a plant.
• The vacuole contains liquids that keep the cell rigid.

Cell Specialization

• Specialized cells are adapted to carry out bodily functions.
• Undifferentiated cells are cells that have not yet assumed their final functional characteristics.
• Embryonic stem cells are cells from the early embryo that has the potential to form almost any other type of cell.
• Differentiated cells are special cells which carry out specific functions.
• Epithelial cells protects tissues from damage or injusry
• Muscle cells are elongated contractile cells that form muscle
• Muscle fibres are strands of protein that enable muscles to contract

Active and Passive Transport

• Both plant and animal cells rely on diffusion for gaseous exchange in lungs, absorption of digested foods from gut, and entry of carbon dioxide into leaves.
• Plants and animal cells rely on the process of osmosis.
• Cell membranes are selectively permeable for osmosis to happen in, and are needed by both plant and animal cells