topic 3

definitions ial as biology unit 2

Light Microscope (Optical Microscope)

A tool that uses a beam of light and optical lenses to magnify specimens up to 1500 times life size.

Magnification

A measure of how much bigger the image you see is than the real object.

Electron Microscope

A tool that uses a beam of electrons and magnetic lenses to magnify specimens up to 500000 times life size.

Resolution (Resolving Power)

A measure of how close together two objects must be before they are seen as one.

Artefacts

Things observed in a scientific investigation that are not naturally present; they occur as a result of the preparation or investigation.

Graticule

A series of lines in the eyepiece of a microscope which help you measure specimens accurately.

Transmission Electron Micrographs (TEMs)

Micrographs produced by the electron microscope that give 2D images like those from a light microscope, but magnified up to 500000 times.

Scanning Electron Micrographs (SEMs)

Micrographs produced by the electron microscope that have a lower magnification than TEMs, but produce a 3D image.

Cytoplasm

A jelly-like liquid that makes up the bulk of the cell and contains the organelles.

Nucleus

An organelle containing the nucleic acids DNA (the genetic material) and RNA, as well as protein, surrounded by a double nuclear membrane with pores.

Protoplasm

The cytoplasm and nucleus combined.

Ultrastructure

The detailed organisation of the cell, only visible using the electron microscope.

Chromatin

The granular combination of DNA bonded to protein found in the nucleus when the cell is not actively dividing.

Nucleolus

An extra-dense region of almost pure DNA and protein found in the nucleus; it is involved in the production of ribosomes and control of growth and division.

Mitochondria

Rod-like structures with inner and outer membranes that are the site of aerobic respiration.

Cristae

The infoldings of the inner membrane of the mitochondria which provide a large surface area for the reactions of aerobic respiration.

Eubacteria

True bacteria (prokaryotic organisms).

Centrioles

Bundles of tubules found near the nucleus and involved in cell division by the production of a spindle of microtubules that move the chromosomes to the ends of the cell.

Spindle

A set of overlapping protein microtubules running the length of the cell, formed as the centrioles pull apart in mitosis and meiosis.

80S Ribosomes

The main type of ribosome found in eukaryotic cells, consisting of ribosomal RNA and protein, made up of a 60S and 40S subunit; they are the site of protein synthesis.

70S Ribosomes

The ribosomes found in the mitochondria and chloroplasts of eukaryotic cells and in prokaryotic organisms.

Endosymbiotic Theory

A theory that suggests mitochondria and chloroplasts originated as independent prokaryotic organisms that began living symbiotically inside other cells as endosymbionts.

Lysosomes

Organelles full of digestive enzymes used to break down worn-out cells or organelles or digest food in simple organisms.

Apoptosis

(Programmed cell death) The breakdown of worn-out, damaged, or diseased cells by the lysosomes.

Endoplasmic Reticulum (ER)

A 3D network of membrane-bound cavities in the cytoplasm that links to the nuclear membrane and makes up a large part of the cellular transport system as well as playing an important role in the synthesis of many different chemical substances.

Rough Endoplasmic Reticulum (RER)

Endoplasmic reticulum that is covered in 80S ribosomes and which is involved in the production and transport of proteins.

Exocytosis

The movement of large molecules out of cells by the fusing of a vesicle containing the molecules with the surface cell membrane; the process requires ATP.

Smooth Endoplasmic Reticulum (SER)

A smooth tubular structure similar to RER, but without the ribosomes, which is involved in the synthesis and transport of steroids and lipids in the cell.

Golgi Apparatus

Stacks of membranes that modify proteins made elsewhere in the cell and package them into vesicles for transport, and also produce materials for plant cell walls and insect cuticles.

Peptidoglycan

A large, net-like molecule found in all bacterial cell walls made up of many parallel polysaccharide chains with short peptide cross-linkages.

Capsule

A layer formed from starch, gelatin, protein, or glycolipid, found around the outside of some bacteria.

Pili

Thread-like protein projections found on the surface of some bacteria.

Bacteriophage

A virus that attacks bacteria.

Flagella

Many-stranded helices of the contractile protein flagellin found on some bacteria; they move the bacteria by rapid rotations.

Mesosomes

Infoldings of the cell membrane of bacteria.

Nucleoid

The area in a bacterium containing the single circular loop of coiled DNA.

Plasmids

Small, circular pieces of DNA that code for specific aspects of the bacterial phenotype.

Gram Staining

A staining technique used to distinguish types of bacteria by their cell wall.

Gram-Positive Bacteria

Bacteria that contain teichoic acid in their cell walls and stain purple/blue with Gram staining.

Teichoic Acid

A chemical substance found in the cell walls of Gram-positive bacteria.

Gram-Negative Bacteria

Bacteria that have no teichoic acid in their cell walls; they stain red with Gram staining.

Cocci

Spherical bacteria.

Bacilli

Rod-shaped bacteria.

Spirilla

Bacteria with a twisted or spiral shape.

Vibrios

Comma-shaped bacteria.

Obligate Aerobes

Organisms that need oxygen for respiration.

Facultative Anaerobes

Organisms that use oxygen if it is available, but can respire and survive without it.

Obligate Anaerobes

Organisms that can only respire in the absence of oxygen and are killed by oxygen.

Tissues

Groups of specialised cells carrying out particular functions in the body.

Organs

Structures made up of several different types of tissue to carry out particular functions in the body.