What is the equation for magnification?
Magnification = size of image ÷ actual size
How can resolution be increased?
- Using a smaller wavelength
- e.g. electron beam
What is an artefact with reference to microscopy?
- Visible structural detail caused by processing the specimen
- -e.g bubble under cover slip
What are the key features of electron microscopy, what types are there, as well as the resolution and magnification?
- Beam of electrons ~ less than 1nm
- Black & White (digitally coloured)
- Magnification: 500,000x
- Transmission electron
- -through specimen
- -resolution: 0.5nm
- -2D image
- Scanning electron
- -across surface
- -resolution: 3-10nm
- -3D images
What are the key features of light microscopes, as well as the resolution and magnification?
- 2D coloured image
- Magnification: 1500x
- Resolution: 200nm
What type of image is produced by a laser scanning confocal microscope?
- 2D or 3D depending on different focal planes
- Laser light causes fluorescence from dye
- High resolution
What does gram staining show?
- Crystal violet
- Gram positive bacteria retain the stain
- Gram negative bacteria have thinner cell wall ⇨ lose stain
Safranin dye counterstains G negative bacteria red
What does the acid-fast technique of staining show?
- Differentiates between mycobacterium and other bacteria
- Myco ⇨ red
- other bacteria lose stain and are exposed to a blue stain
What is the Nucleus?
- Contains DNA
- Double membrane ~ nuclear envelope
- Nuclear pores ~ allow molecules in & out of nucleus
What is the Nucleolus?
- Inside Nucleus
- Produces Ribosomes
What are Mitochondria? What is their basic structure like?
- Site of final stages on cellular respiration
- Produce ATP
- Inner & outer membrane
What are vesicles?
Single membrane sacs for storage & transport
What are lysosomes?
- Contain hydrolytic enzymes
- Break down waste & pathogens
- Have a role in apoptosis
What is the cell cytoskeleton?
- Network of fibres for cell shape & stability
- Aids transport within cells
- Enables cell movement
What are Centrioles?
- 2 Centrioles form a centromere
- ~used for assembly & organisation of spindle fibres
- Found in most eukaryotic cells
- -NOT flowering plants or most fungi
What are flagella and cilia?
- Whip like
- Cell mobility
- Sensory organelle
- Large numbers
- Beat in rhythmic manner
- 9+2 arrangement ~ 2 central microtubules and 9 surrounding pairs
What is the Endoplasmic Reticulum?
Network of membranes connected to outer nuclear membrane
- Rough ER
- -ribosomes bound to surface
- -protein synthesis & transport
- Smooth ER
- -lipid & carbohydrate synthesis & storage
What are ribosomes?
- Made of RNA molecules
- Site of protein synthesis
- Found free floating in cytoplasm or on rough ER
- 70s in prokaryotes, 80s in eukaryotes
What is the Golgi-apparatus?
- Formed of cisternae
- -cis face & tans face
- Modifying & packing proteins into vesicles
What is the cell wall and what is it made of in different organisms?
- Shape & support
- Defense mechanism
- Freely permeable
- Plants ~ cellulose
- Prokaryotic cells ~ peptidoglycan
- Fungi ~ chitin
What are vacuoles?
- Membrane lined sacs in cytoplasm
- Can play role in turgor pressure
- have membrane called 'tonoplast' ~ selectively permeable
What are chloroplasts? What is their basic structure?
- Contain chloryphyll pigment
- Double membrane
- Stroma ~ fluid enclosed
- -form stacks called grana (singular granum)
- -grana joined by lamellae
- Own DNA & ribosomes
- Starch grains present
For the following categories what are the differences between prokaryotic and eukaryotic cells?
Feature | Prokaryotic | Eukaryotic
- Nucleus: No | Yes
- DNA: Circular | Linear
- DNA organisation: proteins fold & condense DNA | histones
- Extra chromosonal DNA: plasmids | present in mitochondria & chloroplasts
- Organelles: non-membrane bound | both non & membrane bound
- Cell Wall: peptidoglycan | chitin ~ fungi, cellulose ~ plants
- Robosomes: 70s | 80s ~ larger more complex proteins
- Cytoskeleton: present | present, more complex
- Reproduction: binary fission | asexual or sexual
- Cell type: unicellular | uni or multicellular
- Cell surface membrane: yes | yes
What are the following ions necessary for?
- Ca2+: Nerve impulse transmission. Muscle contraction.
- Na+: Nerve impulse transmission. Kidney function
- K+: Nerve impulse transmission. Stomatal opening
- H+: Catalysis of reactions. pH determination
- NH4+ (ammonium): Production of nitrate ions by bacteria
- NO3- (nitrate): Nitrogen supply for plants ~ amino acid & protein formation
- HCO3- (hydrogen carbonate): Blood pH
- Cl-: Balance of positive charge of Na+ and K+ ions in cells
- PO43- (phosphate): Cell membrane formation. Nucleic acid & ATP formation. Bone formation.
- OH-: Catalysis of reactions. pH determination
What elements make up the following biological molecules?
- Carbohydrates: Carbon, Hydrogen, Oxygen. Generally Cx(H2O)x
- Lipids: Carbon, Hydrogen, Oxygen
- Proteins: Carbon, Hydrogen, Oxygen, Nitrogen, Sulfur
- Nucleic Acids: Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus
What properties does the hydrogen bonding in water lead to?
- Cohesion: it sticks to itself
- Adhesion: water molecules get attracted to other molecules
- ~transport medium
- ~coolant (since large amount of energy needed to overcome H bonding)
- ~stable environment
Give the structure of α-Glucose, β-glucose and ribose.
- (Just RIBOSE)
What type of monosaccharides form the following disaccharides?
- Maltose: 2x alpha glucose
- Sucrose: Fructose + Glucose
- Lactose: Glactose + Glucose
Describe the structure of starch
Formed from alpha glucose
- 1-4 glycosidic bonds
- helix shape supported by hydrogen bonds within molecule
- Less soluble than glucose
- 1-4 glycosidic bonds
- SOME 1-6 glycosidic bonds
- Branched structure
Describe the structure of glycogen
(equivalent storage molecule to starch, but found in animals & fungi)
- More branched than amylopectin
- More compact ~ needs less space
- Many free ends for addition/removal of glucose
What are condensation and hydrolysis reaction?
- Condensation: removal of water molecule
- Hydrolysis: addition of water molecule
Catalysed by enzymes
Describe the structure of cellulose
- Beta Glucose
- -alternate in orientation
- Straight chain ~ unable to coil/branch
- Hydrogen bond to other cellulose molecules
- -Microfibrils ⇨ macrofibrils ⇨ fibres
Give two examples of macromolecules
Triglycerides and Phospholipids
Describe the structure of a Triglyceride
- 1 glycerol & 3 fatty acids (have a COOH group)
- Ester bonds form during condensation reaction ~ esterification
- Insoluble in water
Describe the structure of phospholipids
- Modified triglycerides
- 1 fatty acid replaced with phosphate ion (PO43-)
- Hydrophilic Head
- Hydrophobic tails
- Act as surfactants ~ form a layer on water
- Form Phospholipid bilayer
What are the roles of lipids?
- Membrane formation
- Hormone Production
- Electrical Insulation
- Thermal Insulation
- Cushioning to protect organs
What is the basic structure of an amino acid?
- (Amino acid as a Zwitter ion)
How are amino acids joined together to form proteins? How are polypeptides broken down?
- Peptide bond forms between carbon & nitrogen
- Catalysed by enzyme found in ribosomes
Breakdown catalysed by proteases
Describe the different levels of protein structure and the bonding involved
- Amino acid Sequence
- -peptide bonds
- Oxygen, Hydrogen and Nitrogen interact
- β-pleated sheet
- -Hydrogen bonding
- Folding into final shape
- R-groups interact (brought together by secondary structure)
- -hydrophobic/hydrophilic interations (polar vs non-polar R groups)
- -hydrogen bonding
- -ionic bonds
- -disulphide bonds (bridges between R groups with sulfur atoms)
- Association of 2+ proteins
- -same bonding as tertairy
Describe the structure and function of Haemaglobin
- Quaternary Protein ~ 4 polypeptides ~ 2 α & 2 β subunits
- Each contain prosthetic haem group
- ~ conjugated protein ~ globular with prosthetic group
- Iron II in prosthetic group bind reversibly with O2
Describe the structure and function of Catalase
- Quaternary protein
- 4 haem prosthetic groups
- ~interact with hydrogen peroxide to speed up breakdown
Describe the structure and function of Insulin
- Hormone ~ blood concentration control
- Soluble ~ travel in blood
Describe the properties and functions of Collagen
- Connective tissue found in skin, tendons, ligaments & nervous system
- 3 polypeptides wound together
Describe the properties and functions of Keratin
- In hair, skin & nails
- High amounts of amino acid containing sulfur
- ~ lots of disulfied bonds
- Flexibility determined by proportion of disulfide bridges
Describe the properties and functions of Elastin
- Elastic fibres in walls of blood vessels & alveoli in lungs
- Made of tropoelastin
What types of bonds are involved in the following molecules?
- Carbohydrates: Glycosidic bonds
- Lipids: Ester bonds
- Proteins: Peptide bonds
- Nucleic Acids: Phosphodiester bonds
How do you test for proteins?
- Biuret Test
- Liquid sample mixed with sodium hydroxide
- Copper sulfate solution added drop by drop until solution turns blue
- Stand for 5 mins
Alkali & copper sulfate solutions are called biuret reagent
Peptide bonds form violet
complexes with copper ions in alkaline solutions
How do you test for reducing & non-reducing sugars?
- Liquid sample in boiling tube
- Add Benedict's reagent (alkaline copper II sulfate)
- Heat gently for 5 mins
ions get reduced in presence of reducing
sugars (e.g. maltose or lactose) turning red
Reagent test strips for reducing sugars
(Reducing sugars ~ all monosaccarides & some disaccarides)
How do you test for Starch
- Add iodine dissolved in potassium iodide solution
- Yellow/Brown turns purple/black if starch is present
How do you test for Lipids?
- Mix sample with ethanol
- Mix with water & shake
is positive result for lipids
Describe the structure of Nucleic Acids
- Monomers: Nucleotides
- Polymer: Nucleic Acid
- Pentose monosaccaride
- Phosphate group PO42-
- Nitrogenous Base
What are the differences between DNA and RNA
- Deoxyribose vs Ribose
- Double strand vs single strand
- Thymine vs Uracil
What are the bases of DNA
- Thymine & Adenine: 2 Hydrogen bonds
- Guanine & Cytosine: 3 Hydrogen bonds
- Pyrimidines: smaller, single carbon ring (T & C)
- Purines: larger, double carbon ring (A & G)
What word describes the directions in which the strands of DNA run?
What happens to the bonds in RNA when it breaks down after protein synthesis?
What does semi-conservative replication mean?
Each new strand of DNA consists of one old and one new
What enzymes are involved in DNA replication?
- DNA Helicase: breaks hydrogen bonds ~ unzips DNA
- DNA Polymerase: catalyses formation of phosphodiester bonds between nucleotides
Describe the nature of genetic code?
- Triplet Code: 3 bases form a codon
- Universal: to all organisms
- Degenerate: different combinations of bases can code for the same amino acid
Describe the structure of ADP and ATP
- Pentose sugar: ribose
- Nitrogenous Base: Adenine
- Inorganic Phosphates