Biology
- Created by: Naomi Of Mirkwood
- Created on: 20-05-16 12:55
Water
• Water is a dipolar molecule
• Hydrogen’s slightly (delta) positive & Oxygen slightly (delta) negative
• Forms Hydrogen bonds
Water: Temperature Control
• High latent heat of vaporisation - large amount of energy required to change from liquid to gas
• Evaporation is an efficient cooling mechanism
• High specific heat capacity - large amount of energy needed to change, temperature
• Thermally stable environment for aquatic organisms
• Aquatic organisms use less energy on temperature control
• Internal temperature of organisms change slowly
Water: Transport
• Water is a good solvent - Ionic compounds dissolve in water e.g. Na+
• Cohesion - water molecules stick together (H-bonds)
• Adhesion - water molecules stick to other things (H-bonds)
• Water columns can be pulled up xylem (cohesion-tension theory)
Water: Other
• Biological / metabolic reactions require water e.g Condensation and Hydrolysis reactions
• Ice is less dense than water (it floats)
• Ice provides habitat for, organisms e.g Polar Bear
• Ice insulates water below - remains liquid - organisms don’t freeze
Transport Across Membranes: By diffusion
• Small nonpolar molecules
• From high concentration to low concentration
Transport Across Membranes: By osmosis
• From a high water potential to a low water potential
Transport Across Membranes: By facilitated diffusi
• Channel protein - small charged molecules e.g. Na+
• Carrier protein - large particles e.g. glucose
• Down concentration gradient;
Transport Across Membranes: By active transport
• Carrier protein
• Against concentration gradient;
• Using ATP/energy (from respiration)
Transport Across Membranes: By endocytosis
• Engulfing by cell surface membrane to form vesicle/vacuole
• Uses ATP
Transport Across Membranes: By exocytosis
• Fusion of vesicle with cell surface membrane;
• Uses ATP
Carbohydrate digestion
• Amylase
• Starch to maltose
• Maltase
• Maltose to glucose
• Hydrolysis
• Of glycosidic bond
Why are enzymes specific?
• Tertiary structure of enzyme (means)
• Active site is only complementary to substrate (name it if you can)
• Active site changes shape to become complementary (induced fit)
• By forming enzyme-substrate complex
Inhibitors
• Inhibitors reduce / prevent formation of ES complex
Inhibitors: Competitive inhibition
• Inhibitor similar shape to substrate
• Binds to active site of enzyme
• Inhibition can be overcome by more substrate
Inhibitors: Non-competitive inhibition
• Inhibitor binds to site on enzyme other than active site
• Prevents formation of active site / changes (shape of) active site
• Cannot be overcome by adding more substrate
Proteins & DNA: Structure of Proteins
• Polymer of amino acids
• Joined by peptide bonds
• Formed by condensation
• Primary structure is order of amino acids
• Secondary structure is folding of polypeptide chain due to hydrogen bonding
• Tertiary structure is 3-D folding due to hydrogen bonding and ionic/disulfide bonds
• Quaternary structure is two or more polypeptide chains
Proteins & DNA: How a mutation can create a non-fu
• Change/mutation in base sequence of DNA/gene
• Change in amino acid sequence/primary structure
• Change in hydrogen/ionic/disulfide bonds
• Change in the tertiary structure
• Change in active site (enzyme) or variable region (antibody)
• Substrate / antigen no longer complementary
• No Enzyme-Substrate complex or Antigen-Antibody complex formed.
Proteins & DNA: DNA Replication
• Strands separate / H-bonds break
• DNA helicase • Both strands act as templates
• Free DNA nucleotides attach
• Complementary/specific base pairing e.g. AT and GC
• DNA polymerase joins nucleotides
• Forming Phosphodiester bonds
• H-bonds reform
• Semi-conservative replication
Protein Synthesis: Transcription
• Strands separate / H-bonds break
• DNA helicase
• Template strand is copied into mRNA
• Free RNA nucleotides attach
• Complementary/specific base pairing e.g. AU and GC
•RNA polymerase joins nucleotides
• Forming Phosphodiester bonds
• H-bonds reform
Protein Synthesis: Translation
• mRNA moves to ribosome in the cytoplasm
• tRNA binds to mRNA
• tRNA anticodons pair with mRNA codons
• Specific amino acid attached to tRNA
• Formation of peptide bond between amino acids
Meiosis
• Cell division to form gametes (eggs and sperm)
• Two divisions forming Four Haploid Daughter cells
• Genetically non identical (due to crossing over and independent assortment)
• Crossing over - creates a new combination of alleles
• Independent assortment - creates a new combination of chromosomes
Meiosis: Prophase I
• Nuclear membrane breaks down
• Chromosomes condense
Meiosis: Metaphase I
• Homologous pairs of chromosomes line up next to each other on the equator
• Spindle attaches to chromosomes at the centromere
• Crossing over of chromatids takes place
Meiosis: Metaphase I
• Homologous pairs of chromosomes line up next to each other on the equator
• Spindle attaches to chromosomes at the centromere
• Crossing over of chromatids takes place
Meiosis: Anaphase I
• Homologous pairs separate - one to each pole (independent assortment)
Meiosis: Telophase I
• Nuclear membranes reforms
• Cell divides (cytokinesis)
Meiosis: Prophase II
(They never ask about this xD)
Meiosis: Metaphase II
• Chromosomes line up on the equator
• Spindle attaches to chromosomes at the centromere
Meiosis: Anaphase II
• Centromeres split
• Chromatids move to opposite poles
Meiosis: Telophase II
• Nuclear membranes reforms
• Chromosomes uncoil
• Cell divides (cytokinesis)
Cell Cycle: Interphase
• G1 – Cell grows and organelles multiply
• S – DNA replicates
• G2 - Organelles multiply ready to Divide
Cell Division
Mitosis or Meiosis
Immune Response
• Phagocyte recognise antigens on bacteria as foreign
• Engulf bacteria • Bacteria in vacuole
• Lysosome fuses with / empties enzymes into vacuole
• Bacteria digested / hydrolysed
• Phagocytes present pathogens antigen (antigen presenting cell)
• Antigens on phagocyte active T-cells (T-lymphocytes) • T-Killer cells – destroy pathogen
• T- Helper cells present antigens and activate B-cells
• Clonal Selection – B-cell with required antibody divides by mitosis to form plasma cells
• antibodies are complementary to antigen (form antigen-antibody complex)
• B-cells from memory cells • Secondary response if infected again with same antigen
Immune Response: Vaccines
• Vaccines contain antigens #
• Dead / weakened pathogens
• Clonal selection of B-cells (mitosis)
• B-cells produce antibodies
• Memory cells produced
• On second exposure - Rapidly produce antibodies / produces more antibodies
• Antibodies destroy pathogen
• Secondary response – don’t feel symptoms
Immune Response: Heart Disease
• Atheroma is cholesterol / plaque / LDL / fatty material
• In artery wall / endothelium of artery
• Atheroma linked to blood clot / thrombosis
• Blocks coronary artery (to heart muscle/ tissue / cells)
• Reduces oxygen & glucose supply (to heart muscle / tissues / cells)
• (Heart muscle / tissue / cells) unable to respire
Immune Response: Control of Mammalian Heartbeat
• SAN initiates heartbeat / acts as a pacemaker
• SAN sends electrical impulses across atria causing atrial contraction
• AVN delays electrical impulses
• Allowing atria to empty before ventricles contract
• AVN sends wave of electrical impulses down Bundle of His / Purkyne fibres
• Causing ventricles to contract from base up / ventricular systole
Immune Response: Control of Mammalian Heartbeat
• SAN initiates heartbeat / acts as a pacemaker
• SAN sends electrical impulses across atria causing atrial contraction
• AVN delays electrical impulses
• Allowing atria to empty before ventricles contract
• AVN sends wave of electrical impulses down Bundle of His / Purkyne fibres
• Causing ventricles to contract from base up / ventricular systole
Immune Response: Adaptations of Arteries
• Elastic tissue stretches under pressure/when heart beats
• Recoils/springs back
• Evens out pressure/flow
• Have muscle that can contract to
• Reduces diameter of lumen/vasoconstriction
• Changes flow/pressure
• Epithelium smooth
• Reduces friction/blood clots/less resistance
Gas Exchange: How is X adapted for efficient diffu
• Large surface area
• So fast diffusion
• Thin epithelium
• So short diffusion distance
• So fast diffusion
• Ventilation & Circulation
• Maintain a high concentration gradient
• So fast diffusion
Gas Exchange: Fish Gills
• Large surface area provided by lamellae/filaments
• Increases diffusion/makes diffusion efficient
• Thin epithelium/distance between water and blood
• Water and blood flow in opposite directions (countercurrent)
• Maintains a high concentration gradient along all of the lamellae
• As water always next to blood with lower concentration of oxygen
• Circulation replaces blood saturated with oxygen
• Ventilation replaces water (as oxygen removed)
Gas Exchange: Insects
Gas Exchange:
• Air enters through spiracles
• Through tracheae
• Diffusion gradient in trachea
• Tracheae closely associated with cells
• Oxygen diffuses into cells
• Ventilation replacing air in tracheae
Prevent Water loss:
• Body covered with (waterproof) waxy cuticle
• Spiracles are able to close
Gas Exchange: Formation and Return of Tissue Fluid
Formation:
• High blood / hydrostatic pressure / pressure filtration
• Forces water / fluid out
• Large proteins remain in capillary
Return:
• Low water potential in capillary / blood
• Due to (plasma) proteins
• Water enters capillary / blood
• By osmosis
• Correct reference to lymph
Oxygen Loading and Unloading in Lungs
• Haemoglobin has a high affinity for oxygen and forms oxyhaemoglobin
• Haemoglobin is found in red blood cells
• Oxygen loading in lungs
• at high p.O2
• Unloads/ releases O2 to respiring cells/tissues
• at low p.O2
• Unloading linked to higher carbon dioxide concentration
Cell Fractionation
• Cell homogenisation to break open cells
• Filter to remove debris/whole cells
• Use isotonic solution to prevent damage to organelles
• Keep cold to prevent/reduce damage by enzymes
• Centrifuge pellets formed
1. Nuclei
2. Chloroplasts (if present)
3. Mitochondria
Last Ribosomes
Bohr Effect
• Increased respiration
• Increased CO2 in blood
• Blood becomes more acidic which
• Lowers haemoglobin’s affinity for oxygen / haemoglobin releases more oxygen / oxygen dissociates/unloads more readily
• To muscles/tissues/cells
• For rapid respiration
• Oxyhaemoglobin dissociation curve shifts to the (BohR – Right)
Transmission Electron Mircoscopes
Advantages:
• Small objects can be seen
• Wavelength of electrons shorter
• TEM has high resolution
Limitations:
• Cannot look at living cells
• Must be in a vacuum
• Must cut section / thin specimen
• Preparation may create artefact
• Does not produce colour image
• Does not form a 3D image
Mitosis
• Cell division for growth and repair
• One Division forming Two Daughter cells
• Genetically Identical
Mitosis: Prophase
• Nuclear membrane breaks down
• Chromosomes condense
Mitosis: Metaphase
• Chromosomes line up on the equator
• Spindle attaches to chromosomes at the centromere
Mitosis: Anaphase
• Centromeres split
• Chromatids move to opposite poles
Mitosis: Telophase
• Nuclear membranes reforms
• Chromosomes uncoil
• Cell divides (cytokinesis)
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