Module 2 Glossary

Fixing

Preserving specimens in as near natural state as possible in chemicals eg Formaldehyde

Sectioning

Dehydrating of specimens with alcohols then placed in a mould with wax or resin to form a hard block which is then sliced thinly with a knife.

Microtome

A type of knife for slicing wax or resin

Staining

Treating specimens with stains to show different structure

Mounting

Securing a sample to a slide with a cover slip

Differential staining

A type of staining which can distinguish between two types of organism which would otherwise be difficult to identify

Gram stain technique

Used to separate bacteria into two groups: gram positive bacteria and gram negative.

Acid fast technique

Staining technique used to differentiate mycobacteria from other types

Dry mount

A specimen is placed straight onto a slide with a cover slip on top

Wet mount

Specimens are suspended in a liquid, and a cover slip is placed on top at an angle

Squash slides

Used to get a sample only one cell thick from a soft sample to prevent damage to a cover slip. Specimen is squashed between two slides.

Smear slides

Edge of a slide is used to smear the sample to create a thin even coating on another slide. Used for blood samples.

Crystal violet

Positively charged blue/purple stain

Methylene blue

Positively charged blue stain

Nigrosin

Negatively charged stain

Congo red

Negatively charged stain

Safranin dye

Bright red stain

Counterstain

An additional dye used to create contrast

Penicillin

An antibiotic

Mycobacterium

A type of harmful bacterium

Magnification

How many times larger the image is than the actual size of the object

Resolution

The level of detail that can be seen – the ability to see individual objects as separate entities.

Eyepiece graticule

A glass disc marked with a fine scale that goes in the eyepiece of microscope

Stage micrometer

A slide with scale markings on used to calibrate an eyepiece graticule

Exocytosis

The release of substances from the cell

Secretory vesicles

The tubes which carry proteins out of the cell

Biological molecule

Made from carbon, hydrogen and oxygen

Condensation reaction

A reaction where two molecules are combined by the removal of water

Hydrolysis reaction

Any reaction where a molecule is split into two smaller molecules by the addition of water

Monomer

Small molecules that bond together to make larger polymers eg amino acid

Polymer

A repeating chain of monomers eg protein

Disaccharide

Sugar formed when two monosaccharides are joined together

Polysaccharide

Sugar formed when more than two monosaccharides join together

Glycosidic bond

A molecule of oxygen joining two sugars

Cohesive

The attraction of molecules for other molecules of the same kind, eg hydrogen bonding in water

Adhesive

Attraction of molecules for other molecules of a different kind

Smooth ER

Responsible for lipid and carbohydrate synthesis and storage

Rough ER

Ribosomes bound to surface, for synthesis and transport of proteins

Cilia

Stationary or mobile, on surface of many cells

Flagella

Used mainly for cell movement

Ribosome

Site of protein synthesis, made from RNA molecules

Golgi apparatus

Compact structure of cisternae, modifies proteins and packages into vesicles

Cisternae

Flattened sacs

Transport vesicle

Vesicle carries proteins around the cell

Excretory vesicle

Vesicles carries proteins to cell surface membrane

Transient

Not permanent

Vacuole

Membrane lined sac containing cell sap

Tonoplast

Membrane of permanent vacuole

Turgor

Pressure exerted on cell by internal fluids

Chloroplast

Plant cell organelle of photosynthesis

Stroma

Fluid in the inner membrane of chloroplast

Thylakoid

Sacks containing chlorophyll

Granum

Stack of thylakoids

Chlorophyll

Pigment which absorbs light for photosynthesis

Homopolysaccharide

Polysaccharide containing a single type of monomer

Heteropolysaccharide

Polysaccharide containing two or more types of monomers

Macromolecule

Large organic compounds

Trigylceride

Molecule consisting of a glycerol group and three fatty acid chains

Phospholipid

Contain glycerol, phosphate group, two fatty acid tails

Steroid

Lipid involved in membrane structure

Hydrophobic

Insoluble in water

Saturated

Single bonds

Unsaturated

Double bonds

Polyunsaturated

More than one double bond

Monounsaturated

One double bond

Hydrophilic

Attracts water

Cholesterol

Lipid regulating fluidity of membranes

Peptide bonds

Bonds between amino acids

Polypeptide

Protein, lots of amino acids joined by peptide bonds

Buffer

Maintains pH of solution by mopping up or donating hydrogen ions

Amphoteric

Amino group acting as hydrogen acceptor and carboxyl group acting as hydrogen donator

Covalent bond

Shared pair of electrons between two non metals

Ionic bond

Transfer of electrons between two oppositely charged ions

Cation

Positively charged ion

Anion

Negatively charged ion

Electrolyte

Ions in a solution

Carbohydrates

C, H and O

Lipids

C, H and O

Proteins

C, H, O, N and S

Nucleic acid

C, H, O, N and P

Primary structure

Sequence of amino acids that have not been folded

Secondary structure

The coiling ror folding of an amino acid chain, caused by hydrogen bonding. Alpha helix or beta pleated sheet

Tertiary structure

Overall 3D shape of a protein molecule, as a result of interactions between the R groups of amino acids, most commonly hydrogen bonds, disulphide bridges, ionic bonds and hydrophobic interactions.

Quaternary structure

Arises when two or more polypeptide chains join together/interact to form a single protein.

Disulphide bridge

Bond between two sulphurs on amino acids.

Prosthetic group

Non protein part of a protein

mRNA

Carries message between DNA in nucleus and ribosome

tRNA

Transfers amino acids to a growing polypeptide chain

rRNA

What ribosomes are made from

Triplet code

3 bases in DNA code for one amino acid

Universal

Found in all organisms

Degenerate

More than one codon for each amino acid

Non-overlapping

Each base in genetic code is only read once

Codon

A group of three bases which code for one amino acid

Start and stop codon

Non coding codon

Transcription

The formation of mRNA from DNA antisense strand

DNA helicase

Unwinds double helix (breaks H bonds) in DNA replication

RNA polymerase

Creates phosphodiester bonds between RNA bases on mRNA

Template/antisense strand

The strand mRNA pairs to

Sense strand

The strand of DNA containing genes which code for proteins