Topic A2.2 Cell Structure

Fluorescent stains

Absorb light and re-emit at a longer wavelength, creating much brighter images

Immunofluorescence

Fluorescent markers are attached to specific chemicals like antibodies. Used to track movement of chemicals within a cell.

Freeze fracture

Cells are frozen in very cold propane and then split apart and prepared. This allows cell surfaces to become visible

Cryogenic electron microscopy

Used for protein structure research, with high resolution of about 0.12nm

Magnification

How much bigger the image appears than actual size

Resolution

Ability to distinguish 2 points as separate or distinct

Field of view (FOV)

The circle you see when looking through the lens

Field diameter

The measurement of the field of view

Stage micrometer

Microscope slide with a ruler etched on it, used to calibrate an eyepiece measuring scale.

Reticule ruler

A ruler in the eyepiece that allows you to measure the specimen at any power.

Reticule

Also known as a graticule; a pattern of fine lines or markings in the eyepiece used for measurements.

Microscopy

The technique used to view specimens that cannot be seen with the naked eye. Increases magnification and resolution.

Depth of field

The vertical distance that remains in focus at any particular point.

Unicellular

All metabolic functions in one cell

Multicellular

Cells are specialized, organized, dependent

Metabolism

The web of all the enzyme-catalysed reactions in a cell or organism, e.g. respiration

Response

Living things can respond to and interact with the environment

Homeostasis

The maintenance and regulation of internal cell conditions, e.g. water, sugar levels, and pH

Growth

Living things can grow or change size/shape

Excretion

The removal of metabolic waste

Reproduction

Living things produce offspring, either sexually or asexually

Nutrition

Feeding by either the synthesis of organic molecules (e.g. photosynthesis) or the absorption of organic matter

Bacterial plasmid (DNA)

Separate from chromosomal DNA and can replicate independently. Double-stranded and circular. Found naturally in bacteria.

Binary Fission (Asexual Reproduction)

DNA is replicated semi-conservatively. Two DNA loops attach to the membrane. The membrane elongates and pinches off (cytokinesis), forming two separate cells. The 2 daughter cells are genetically identical (clones)

Red Blood Cell

Biconcave shape provides a large surface area to absorb oxygen. Mature cells have no nucleus, increasing the volume available for oxygen-binding haemoglobin molecules

Nerve Cell

Long, thin shape to transmit nerve impulses. High concentration of mitochondria to provide energy for nerve impulse transmission

Small Intestine Epithelial Cell

Large surface area of membrane lining the gut to absorb the products of digestion. High concentration of mitochondria to provide the energy required for active transport

Upper & Lower Epidermis Cells

Contain and protect the leaf and therefore contain relatively few chloroplasts.

Palisade Mesophyll Cells

Packed with chloroplasts and are long, thin, and tightly packed to absorb as much of the light energy as possible for photosynthesis.

Spongy Mesophyll Cells

Provide a large surface area to absorb carbon dioxide and allow the excess oxygen to diffuse out.

Prokaryotes

No membrane-bound organelles, no nucleus, simple structure, reproduce asexually, and have smaller ribosomes (70S). Specialized structures: nucleoid (DNA location), plasmids, capsule, pili, and flagella

Eukaryotes

Membrane-bound organelles, nucleus, complex structure, bigger ribosomes (80S), e.g., animals, plants, fungi, and protists. Specialized structures: mitochondria, smooth ER, rough ER, Golgi apparatus, lysosomes, chloroplasts, and vacuoles

Animal cells

Centrioles coordinate cell division. Cilia and flagella allow locomotion in single-celled organisms and move fluid, materials, or cells in multicellular organisms. Lysosomes carry out digestion using enzymes.

Plant cells

Cell wall is a stiff lattice-like wall that maintains structure and shape. Chloroplasts carry out photosynthesis and make glucose. Large central vacuole contains fluid or sap and provides structure to the cell and plant.

Fungi

Heterotrophic decomposers that eat decaying matter. Thick cell walls are composed of chitin. Can be unicellular or multicellular. Can grow with or without light or oxygen.