Module 2 Foundations in Biology Flashcards
Compound microscopes led to new discoveries essential for cell theory to be fully explained. Explain the benefit of having two lenses in a microscope. (4 marks)
- Objective lens and eyepiece lens
- Objective lens magnifies the specimen
- Eyepiece lens magnifies image (from objective lens)
- Higher magnification produced than with just one lens
Outline how a student could prepare a temporary mount of tissue for a light microscope.
1) Obtain thin section of tissue e.g. using ultratome or by maceration.
2) Plant plant tissue in a drop of water.
3) Stain tissue on a slide to make structures visible.
4) Add coverslip using mounted needle at 45* to avoid trapping air bubbles.
Describe how light microscopes work.
- Lenses focus rays of light and magnify the view of a thin slice of specimen.
- Different structures absorb different amounts and wavelengths of light.
- Reflected light is transmitted to the observer via the objective lens and eyepiece.
Describe how a transmission electron microscope (TEM) works.
- Pass a high energy beam of electrons through a thin slice of specimen.
- More dense structures appear darker since they absorb more electrons.
- Focus image onto fluorescent screen of photographic plate using magnetic lenses.
Describe how a scanning electron microscope (SEM) works.
- Focus a beam of electrons onto a specimen’s surface using electromagnetic lenses.
- Reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate.
Describe how a laser scanning confocal microscope works.
- Focus a laser bean onto a small area on a sample’s surface using the objective lenses.
- Fluorophores in the sample emit photons.
- Photomultiplier tube amplifies the signal onto a detector. An image is produced pixel by pixel in the correct order.
Why do samples need to be stained for light microscopes?
Coloured dye binds to the structures.
Facilitates absorption of wavelengths of light to produce image.
Differential staining: contrast between heavily and lightly stained areas distinguishes structures.
Outline how a student could prepare a temporary mount of tissue for a light microscope.
1) Obtain thin section of tissue e.g. using ultratome or by maceration.
2) Plant plant tissue in a drop of water.
3) Stain tissue on a slide to make structures visible.
4) Add coverslip using mounted needle at 45* to avoid trapping air bubbles.
Describe how light microscopes work.
- Lenses focus rays of light and magnify the view of a thin slice of specimen.
- Different structures absorb different amounts and wavelengths of light.
- Reflected light is transmitted to the observer via the objective lens and eyepiece.
Describe how a transmission electron microscope (TEM) works.
- Pass a high energy beam of electrons through a thin slice of specimen.
- More dense structures appear darker since they absorb more electrons.
- Focus image onto fluorescent screen of photographic plate using magnetic lenses.
Describe how a scanning electron microscope (SEM) works.
- Focus a beam of electrons onto a specimen’s surface using electromagnetic lenses.
- Reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate.
Describe how a laser scanning confocal microscope works.
- Focus a laser bean onto a small area on a sample’s surface using the objective lenses.
- Fluorophores in the sample emit photons.
- Photomultiplier tube amplifies the signal onto a detector. An image is produced pixel by pixel in the correct order.
Why do samples need to be stained for light microscopes?
Coloured dye binds to the structures.
Facilitates absorption of wavelengths of light to produce image.
Differential staining: contrast between heavily and lightly stained areas distinguishes structures.
State the magnification and resolution of a compound optical microscope.
Magnification - x 2000
Resolution - 200nm
State the magnification and resolution of a TEM.
Magnification - x 500,000
Resolution - 0.5 nm
State the magnification and resolution of an SEM.
Magnification - x 500,000
Resolution - 3 ^- 10 nm
Describe the structure of the nucleus.
- Surrounded by a nuclear envelope, a semipermeable double membrane.
- Nuclear pores allow substances to enter/exit.
- Dense nucleolus made of RNA and proteins assembles ribosomes.
Describe the function of the nucleus.
- Contains DNA coiled around chromatin into chromosomes.
- Controls cellular processes: gene expression determines specialisation, site of mRNA transcription, mitosis, and semiconservative replication.
Describe the structure and the function of the endoplasmic reticulum (ER).
Cisternae structure: Network of tubules and flattened sacs extends from cell membrane and connects to nuclear envelope.
ROUGH ER - Many ribosomes attached for protein synthesis and transport.
SMOOTH ER - Lipid synthesis.
Centrioles
Structures found in the cytoplasm made of microtubules that produce the spindle fibres during mitosis.
Chloroplast
Organelles found in plants and algae that are the site of photosynthesis.
Cilia
Small hair-like structures that project from the surface of cells.
Confocal Microscopy
A type of microscopy that uses lasers to scan a specimen point by point to produce an image.
Cytoskeleton
A mesh of protein fibres found in the cytoplasm of eukaryotic cells used for structural support and intracellular transport.
Differential Staining
Using multiple different stains to distinguish different parts of a specimen.
Eukaryotic Cell
A type of cell that contains a nucleus along with membrane bound organelles.
Flagella
A whip-like structure found on bacterial cells that is used for cell movement.
Golgi Apparatus
An organelle found in eukaryotic cells that is involved in the modification and packaging of proteins.
Light Microscope
A type of microscope that uses a series of lenses to magnify the visible light reflecting off a specimen.
Lysosomes
Membrane-bound vesicles found in the cytoplasm that contain a hydrolytic enzyme called lysozyme.
Magnification
How much bigger an image appears compared to the original object calculated using the following formula:
image size = actual size x magnification
Mitochondrion
An organelle found in eukaryotic cells that is the site of aerobic respiration.
Nuclear Envelope
A double membrane that surrounds the nucleus.
Nucleolus
A structure found inside the nucleus that contains proteins and RNA and is involved in synthesizing new ribosomes.
Nucleus
An organelle found in eukaryotic cells that stores the genetic information of the cell as chromosomes and is surrounded by a membrane called the nuclear envelope.
Plasma Membrane
A semipermeable lipid bilayer studded with proteins that surrounds the cell and many organelles.
Prokaryotic Cell
A type of cell that does not contain any membrane bound organelles or a nucleus.
Resolution
The ability to distinguish two different points in a specimen.
Ribosomes
Organelles found either free in the cytoplasm or membrane bound that are
involved in the synthesis of proteins.
Rough Endoplasmic Reticulum (RER)
A membrane-bound organelle that is involved in the synthesis and packaging of proteins.
Scanning Electron Microscope (SEM)
A type of microscope that passes a beam of electrons over the surface of a specimen to produce an image.
Smooth Endoplasmic Reticulum (SER)
A membrane-bound organelle involved in lipid
synthesis.
Transmission Electron Microscope (TEM)
A type of microscope that passes a beam of electrons through a sample to produce an image.
Adhesion
A property of water molecules that creates an attraction between them and surfaces that they are in contact with.
Amino Acid
The monomers containing an amino group (NH2), a carboxyl group (COOH) and a variable R group that make up proteins.
Amylopectin
A branched polysaccharide made up of alpha glucose monomers joined by α-1,6 glycosidic bonds that makes up starch along with amylose.
Amylose
An unbranched polysaccharide made up of alpha glucose monomers joined by α-1,4 glycosidic bonds that makes up starch along with amylopectin.
Anions
An ion with a negative charge.
Benedict’s Test
A biochemical test used to detect the presence of a reducing sugar in a solution and distinguish between solutions of different reducing sugar concentrations.
Biuret Test
A biochemical test that produces a purple colour when it is added to a solution containing protein.
Cations
An ion with a positive charge.
Cellulose
A linear polysaccharide that is the main component of the cell wall in plants and is made up of many beta glucose molecules joined by β-1,4 glycosidic bonds.
Chromatography
A technique used to separate different molecules in a solution by their different properties.
Cohesion
A property of water molecules that creates an attraction between them which causes them to stick together.
Collagen
A type of fibrous protein that provides strength to many different cell types and makes up connective tissues.
Condensation Reaction
A type of reaction that joins two molecules together with the formation of a chemical bond involving the elimination of a molecule of water.
Conjugated Protein
A protein with a prosthetic group bound to it.
Elastin
A type of fibrous protein that allows tissues and structures like blood vessels to stretch and return to their original shape.
Fibrous Protein
A class of long chain proteins that are generally insoluble in water and typically have structural roles.
Globular Protein
A class of spherical shaped proteins that are generally water soluble and typically have metabolic roles.
Glucose
A hexose monosaccharide that is the main respiratory substrate in eukaryotes.
Glycogen
A highly branched polysaccharide that is used as the main energy storage molecule in animals and is made up of alpha glucose monomers joined by α-1,4 glycosidic bonds.
Haemoglobin
A type of conjugated globular protein used to transport oxygen that is made up of four polypeptide chains each containing a haem prosthetic group.
Hexose Monosaccharide
A simple sugar that contains 6 carbon atoms.
Hydrogen Bond
A type of weak bond formed between an electropositive hydrogen and an electronegative atom like oxygen or nitrogen.
Hydrolysis
Breaking a chemical bond between two molecules involving the use of a water molecule.
Insulin
A globular protein hormone that is made in the pancreas in response to detection of high glucose levels in the blood.
Iodine Test
A biochemical test that produces a blue/black colour when it is added to a solution containing starch.
Keratin
A type of fibrous protein that provides strength to hair and nails.
Lactose
A disaccharide made of a molecule glucose and galactose joined by a glycosidic bond.
Lipid Emulsion Test
A biochemical test that produces a cloudy emulsion when performed on lipids.
Maltose
A disaccharide made of two molecules of glucose joined by a glycosidic bond.
Monomer
An individual unit that can be bonded to other identical monomers to make a polymer.
Monomers
The smaller units from which larger molecules are made.
Pentose Monosaccharide
A simple sugar that contains 5 carbon atoms.
Phospholipid
A type of amphipathic lipid made from a molecule of glycerol bonded to two fatty acid molecules and a phosphate group.
Polymer
A molecule made from many repeating monomers joined together.
Polymers
Molecules made from a large number of monomers joined together.
Primary Structure
The individual sequence of amino acids in a protein.
Quaternary Structure
A structure only applicable to proteins with multiple polypeptide chains that describes the interactions of the different chains.
Ribose
A pentose monosaccharide which composes the backbone of RNA.
Saturated Fatty Acid
A type of fatty acid molecule containing only single bonds between the carbon atoms.
Secondary Structure
The local interactions of the amino acids in the polypeptide chain.
Solvent
A liquid that solutes can dissolve in to form a solution.
Starch
A polysaccharide used for energy storage in plants that is made up of alpha glucose joined together in the forms of amylose and amylopectin.
Sucrose
A disaccharide made of a molecule glucose and fructose joined by a glycosidic bond.
Tertiary Structure
The way that the whole protein folds to make a three dimensional structure.
Triglyceride
A type of lipid formed from a molecule of glycerol joined by ester bonds to three fatty acid molecules.
Unsaturated Fatty Acid
A type of fatty acid molecule containing at least one double bond in the carbon chain.
Adenosine Triphosphate (ATP
A nucleotide consisting of a molecule of ribose joined to the nitrogenous base adenine and three phosphate groups.
Degenerate (Genetic Code)
A term used to describe the fact that some amino acids can be coded for by multiple different codons.
Deoxyribonucleic Acid (DNA)
A double stranded polynucleotide that contains the genetic material of an organism and is made up of deoxyribonucleotide monomers joined together by phosphodiester bonds.
DNA Nucleotide
The monomer that makes up DNA and consists of deoxyribose, a nitrogenous base and a phosphate group.
DNA Polymerase
An enzyme that catalyses the formation of phosphodiester bonds between nucleotides during the synthesis of a new DNA strand.
RNA Polymerase
An enzyme that catalyses the formation of phosphodiester bonds between nucleotides during the synthesis of a new RNA strand.
Helicase
An enzyme that catalyses the unwinding and unzipping of DNA in many processes like replication and transcription.
Messenger RNA (mRNA)
A type of RNA that carries genetic information from the DNA in the nucleus to the ribosomes for translation.
Non-Overlapping (Genetic Code)
A term used to describe the fact that each base is only part of one codon and that each codon is read one at a time in order.
Nucleotide
The monomer from which nucleic acids are made that consists of a pentose sugar, nitrogenous base and phosphate group.
Phosphodiester Bond
A type of bond that joins nucleotides together to create polynucleotides.
Purines
A class of nitrogenous bases which are made up of two rings that adenine and guanine are members of.
Pyrimidines
A class of nitrogenous bases which are made up of a single ring that cytosine, thymine and uracil are members of.
Ribosomal RNA (rRNA)
A type of RNA that makes up ribosomes
RNA nucleotide
The monomer that makes up RNA and consists of ribose, a nitrogenous base and a phosphate group.
Semi-Conservative Replication
The replication of DNA to produce two new DNA molecules which both contain one new strand and one old strand from the original DNA molecule.
Transcription
The process of synthesising a new mRNA strand from a molecule of DNA.
Transfer RNA (tRNA)
A type of RNA that has three hairpin loops, an anticodon for attachment to the mRNA codon and an amino acid binding site and is used to carry amino acids to the ribosome.
Translation
The process of protein synthesis where complementary tRNAs carrying amino acids are brought to each codon in an mRNA molecule as it moves through a ribosome.
Triplet (Genetic Code)
A term used to describe the fact that DNA is grouped into three base long codons that are read together and code for an amino acid.
Universal (Genetic Code)
A term used to describe the fact that the same codons code for the same amino acids in all organisms.
Facilitated Diffusion
The net movement of substances from a high concentration to a lower concentration (down their concentration gradient) through transport proteins without the use of energy.
Fluid Mosaic Model
A model that describes membrane structure as a sea of mobile phospholipids studded with various proteins.
Hydrophilic
A molecule which is attracted to water.
Hydrophobic
A molecule which repels water.
Integral Membrane Protein
A type of protein bound to the membrane with strong interactions.
Osmosis
The net movement of water molecules across a partially permeable membrane from a region of high water potential to a region of lower water potential without the use of energy.
Peripheral Membrane Protein
A type of protein that is weakly bound to the surface of the membrane.
Phagocytosis
The ingestion of solid material (particularly pathogens and foreign material) by phagocytic cells.
Phospholipid
A type of lipid formed by the condensation of one molecule of glycerol, two molecules of fatty acid and a phosphate group.
Pinocytosis
The bulk uptake of liquids into the cell using energy in the form of ATP.
Simple Diffusion
The spreading out of substances from a high concentration to a lower concentration (down their concentration gradient) without the use of energy.
Turgid
A term used to describe a cell that is swollen due to large amounts of fluid uptake.
Water Potential
A measure of the tendency of water molecules to move from one area to another measured in kilopascals (kPa) and given the symbol Ψ.
Plasmolysis
The effect produced by placing plant cells in a hypertonic solution causing the cell to shrivel from water loss, resulting in the membrane pulling away from the rigid cell wall
