Why do electron microscopes produce images with higher resolution?
Electrons have smaller wavelength
Pass through objects more often
Scanning electron microscope features?
3D image
100,000-500,000 x magnification
3-10nm resolution
Transmission electron microscope?
No 3D image
500,000- 2,000,000 x magnification
0.2-0.5nm resolution
Resolution:
Shortest distance between 2 objects that can be distinguished by the viewer
Formula for image size (value you get with ruler)?
Image size= magnification x Size of object in reality (very small)
value of a mm?
1 metre x 10^-3
value of a um?
1 metre x10^-6
Value of nm?
1 metre x 10^-9
Prokaryotic cell=
In single celled organisms
DNA= supercoiled
Ribosomes= 70s, not 80s
Cell wall= peptidoglycan
3 types of monosaccharides:
Triose
Pentose
Hexose (glucose)
How’s Alpha glucose structure different
Draw 2 X's and add chimney on left Carbon 1= Carbon at very right There are OH groups on C1, C2, and C4 In Alpha OH group on C1 bellow plane In Beta OH group on C1 above plane
Glycosidic bond=
When 2 monosaccharides bond to form a disaccharide undergoing a condensation reaction
Alpha glucose + Alpha glucose =
Maltose
Alpha glucose + Fructose =
Sucrose
Alpha glucose + Galactose =
Lactose
Benedict’s test for reducing and non reducing sugars
Heat with benedict’s solution, if present blue to brick red
If no colour change, boil with HCl, which hydrolyses any sucrose present into fructose, and glucose
Nuetralise with sodium carbonate
Do benedict’s test again
Test for starch?
Add Iodine solution
If present blue/black colour forms
Triglyceride structure?
1 glycerol unit
3 fatty acid side chains
Structure of glycerol?
3 carbons, each with an OH bonded on the same side, rest are hydrogen
Fatty acid structure?
Hydrocarbon chain with carboxylic acid one side, and methyl group the other
Phospholipid structure?
Same as triglycerides except one fatty acid chain replaced by phosphate group
Example of a sterol?
Cholesterol
How do synthesised proteins leave cell?
Synthesised on ribosome bonded to ER
They pass into it’s cisternae and packaged into transport vehicles
Move to Golgi apparatus with help from cytoskeleton
Proteins structurally altered and leave again via vesicles
Secretory vesicles take it to cell membrane where leave via exocytosis
3 components of cytoskeleton?
Micofilaments
Microtubules
Intermediate fibres
Structure of an amino acid?
NH2 CRH COOH
Amine group
R group
Carboxylic acid
Peptide bond:
Bond between 2 amino acids ( covalent between amine and carboxylic acid)
Condensation reaction
Peptidly transferase
Biuert test:
Sample mixed with equal amounts of NaOH solution
CuSO4 added until blue
Left still, if lilac colour appears protein is present
Primary structure:
The sequence of amino acids in a polypeptide, determines final shape of protein
Secondary strucure
The folding and coiling caused by hydrogen bonding between Nitrogen, Hydrogen and Oxygen of nearby aminos
(alpha helix, Beta pleated sheet)
Tertiary structure=
Further folding of secondary structure, by bonds and interactions between R groups
Hydrogen bonds
Hydrophobic/phallic interactions
Disulphide bonds (cysteine)
Ionic bonds
Quaternary structure:
Level of structure when 2 or more polypeptide subunits are bonded together
Denaturation of a protein:
Increase in thermal energy
Increase in Kinetic energy
Bonds in tertiary structure will start to vibrate more and break
Weakest to strongest (hydrogen to disulphide)
As bonds break tertiary structure breaks down
Nucleotide:
5 Carbon sugar
Phosphate group
Organic nitrogenous base
Prymidines:
Single ring structure
Thymine and Cytosine
Purines
Double ring structure
Adenine and Guanine
A-T
2 Hydrogen bonds
C-G
3 hydrogen bonds
Differences in DNA and RNA
DNA:
Bases are AT CG
Deoxyribose sugar
Double stranded
RNA:
Bases are AU CG
Ribose sugar
Single stranded
DNA replication
Enzyme helicase unwinds and unzips the 2 strands of DNA
By breaking hydrogen bonds between base pairs
Each new strand acts as template for new strands to be made against
Free DNA nucleotides hydrogen bond to templates via complementary base pairing
Enzyme DNA polymerase catalyses condensation between sugar and phosphate group, creating sugar phosphate backbone
= Semi conservative
Strands run in 2 opposite directions:
Leading strand=continueous replication
Lagging strand= replication done in okazaki fragments
Why is DNA replication semi conservative?
2 DNA molecules made from one molecule, with one new and one old strand
What’s replication;
DNA copies it self exactly
What’s transcription?
Making mRNA by transferring the code of the gene onto the mRNA single strand
Stages of transcription?
RNA helicase unwinds and unzips 2 strands of DNA being transcribed
Free RNA nucleotides hydrogen bond to antisense strand via complementary base pairing (AU, CG)
RNA polymerase catalyses condensation reaction between Ribose and Phosphate to form sugar phosphate backbone
mRNA leaves nucleus via nuclear pore, and travels to ribosome for translation
Stages of translation?
Ribosome binds to mRNA at the beginning of strand at start codon
mRNA carries the code for synthesising the polypeptide
Sequence of bases on mRNA read in 3’s, (triple codons)
tRNA molecules each carry a specific amino acid, and have an anticodon on other side
tRNA lines up with opposite to correct codon via base pairing rule
Ribosomes catalyse reaction between adjacent amino acids forming peptide bonds
Process continues until stop codon reached
Polypeptide created
4 Factors which affect rate of reaction in enzymes?
pH
Temp
Substrate conc
Enzyme conc
Facillitated diffusion=
movement of molecules from a region of high concentration to low
Down a conc gradient
Uses carrier and intrinsic proteins
How do carrier proteins work
Molecule/ion being transported binds to receptors of the channel of the carrier protein
Atp binds to carrier protein, and is hydrolysed into ADP and phosphate
Binding of Phosphate causes protein to change shape, opeining it up to inside of cell
Molecules/ions released into cell
Phosphate released and binds with ADP to form ATP
Cytolysis
Animal cell bursting
Crenation
Animal cell shrinking
Plasmolysis
Plant cell shrinkning, protoplast pulled away from cell wall
Stages of interphase
G1,S,G2
G1
Protein synthesis
Organelles replicate
Cell grows
S phase
DNA replicated in nucleus
G2:
Cell continues to grow
Duplicated DNA checked for errors
Prophase:
Chromatin condenses to form chromosomes, nucleolus and nucleus break down
Spindle fibres move centromers into centre of cell
Nuclear envelope disappears
Metaphase:
Chromosomes moved by spindle fibres to form metaphase plate
Anaphase:
Centromers holding pair of chromosomes divide
Shortening spindle fibres pull them to opposite ends of cell
Telophase
Chromatids reached poles and are now chromosomes
2 new sets of chromosomes assemble at each pole
Chromosomes uncoil, nucleolus forms
Cytokinesis occurs
Order of cell division?
Prophase, metaphase, anaphase, telophase, cytokenesis
Prophase 1:
Chromosomes condense
Homologous chromosomes pair up in a process called synapsis to form bivalents
Crossing over occurs, arms of chromatids mix
Metaphase 1:
Bivalents attach to spindle fibres, and are randomly arranged along spindle
Anaphase 1:
Homologous chromosomes separated
Centromers pulled to opposite sides of cell
Telophase 1:
Chromatids uncoil, nuclear envelope forms
Mitosis forms?
2 Genetically indentical haploid cells
Meitosis forms?
4 genetically different diploid cells
What’s a totipotent cell?
Can differentiate into any cell eg. zygote
What’s a pluripotent cell?
Can form all tissue types, but not whole organism eg. early embryos
Multipotent cell?
Can only form a range of cells within a tissue type eg.bone marrow
Inspiration:
Diaphragm contracts, flattening and lowering
Intercostal muscles contract, ribs move upwards
Volume of thorax increased, pressure decreased
Air moves in
Expiration
Diaphragm relaxes, moves to dome shape
Intercostal muscles relax, ribs move downwards
Volume of thorax decreased, pressure increased
air forced out
Tidal volume=
air that moves in and out of lungs with each resting breath
Vital capacity=
volume of air that can be breathed when strongest exhalation followed by strongest inhalation
Inspiratory reserve volume=
Maximum volume you can breathe in over and above normal inhalation
Expiratory reserve volume=
Extra amount of air you can force out of lungs above tidal volume
Residual volume=
Volume of air left in lungs after strongest exhalation
Total lung capacity=
Sum of vital capacity and residual volume
How do fish maintain water flow when they stop moving?
Mouth opens, increasing volume of buccal cavity, pressure drops water moves in
Operculum valves containing, cavity containing gills expands and lowers
Buccal cavity moves back up, increasing pressure so water flows over gills
Counter current system=
Water and blood flow in opposite directions maintaining concentration gradient
Blood going through heart:
Vena cava to Right atrium
To right ventricle through tricuspid valve
To pulmonary artery and lungs through semi lunar valve
Enters via pulmonary vein, to left atrium, to left ventricle through mitrial valve
Then Aorta though semi lunar valve then the rest of the body
How CO2 transferred in blood?
CO2 + Water = carbonic acid
Carbonic acid dissociates into H+ ions and HCO3 - ions
HCO3 - ions move out of cell via diffusion Cl - ions move in, maintain electrical balance= chloride shift
This maintains conc gradient for more CO2 to move in
When erythrocytes reach lungs carbonic acid back to it’s reactants, CO2 and Cl- move out
Cardiac cycle=
Diastole-atria then ventricles fill up with blood
Systole- atria and ventricles contract, blood goes out of aorta and pulmonary artery
How is heart beat maintained
Sino-atrial node sends out electrical excitation, atria contract
Non conducting tissue prevents it reaching ventricles
Electricity picked up by atrio ventricular node, reaches bundle of his (conducting tissue in septum)
Branch out from bottom of ventricles causing them to contract
Late blight
fungus
Black sigatoka
fungus
TB
bacteria
Meningitus
Bacteria
What substance seperates of infected plant cells
callose
Blood clotting
Tissue damaged
Platelts activated
Fibrin causes clot
Inflamation
Mast cells produce cytokines which attract phagocytes
Mast cells make histamines which make blood vessel walls more leaky leading to swelling
Dilation of blood vessels= increased temp
Humoral response
Pathogen enters body, engulfed by macrophages, non self antigens now present on it
B and T cells which are complementary to non self antigens bind on and are cloned T helper cells secrete cytokines, and B cells make clones
B cells become plasma cells and secrete antibodies killing infection, or become memory cells
Cell meditated response
Self antigens turned into non self
Virus invades host cell, non self antigen present on cell
Complementary T cell binds to non self antigen, and divides my mitosis
Differentiates into killer helper and memory cells
Killer kill
helper cytokines
Antibody
C= constant never changes binds to phagocyte V= variable where antigens bind to