Biology 2

Created by: willmiddleham
Created on: 20-02-14 10:21

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Biology 2
- Gas exchange in organisms
  - SA:Vol
    - As an organism gets bigger their SA:Vol gets smaller.
    - Unicelled organisms
      - Have a very large SA:Vol, so they can exchange gases directly through the cell membrane.
  - Unicelled organisms
    - Have a very large SA:Vol, so they can exchange gases directly through the cell membrane.
  - Sponges - Hollow body
    - Being hollow increases the SA:Vol so gas can be exchanged through the cell membranes.
    - SA:Vol
      - As an organism gets bigger their SA:Vol gets smaller.
  - Tapeworms - Flattened body
    - They increase their SA:Vol by having a flat body, decreasing the diffusion distance.
  - Insects
    - They have little openings in their exoskeleton called spiracles.
      - They lead to a network of tubes called trachea.
        These then branch into tracheoles that carry air directly to the cells.
        
        The trachea and tracheoles are held open by rings of chitin.
        These then branch into tracheoles that carry air directly to the cells.
    - To increase respiration rate, insects move their bodies up and down to maintain a concentration gradient.
      - Rate of diffusion increases.
  - Fish
    - Fish exchange gas through gills, which are composed of thousands of filaments. Each filaments is covered in lamallae containing blood capillaries.
      - This structure gives a large SA and a short diffusion pathway for gas exchange.
    - Water flows over the filaments and lamellae and oxygen diffuses down a concentration gradient. Carbon dioxide diffuses the opposite way.
    - They improve the efficiency of gas exchange by using a countercurrent flow system.
      - This is where the blood is flowing in the opposite direction to the flow of water.
        So a concentration gradient is maintained and it never reaches equilibrium.
- Human Circulatory System
  - Arteries
    - Composed mainly of elastic tissue.
      - So that the artery can expand and recoil depending on the pressure of the blood.
  - Arterioles
    - The muscles can contract or relax. Happens during homeostasis.
    - Contraction = Vasoconstriction
    - Relax = vasodilation
  - Capillaries
    - Where substances enter/leave the blood.
    - They have a large SA to help with diffusion.
  - Veins
    - Have large lumens to reduce resistance to blood flow. They also contain valves to stop blood flowing backwards.
  - Subsystems
    - KIDNEY
      - To kidney: Renal Artery
        From aorta, high oxygen concentration.
      - From kidney: Renal Vein
        To vena cava, low oxygen concentration.
    - LIVER
      - To liver: Hepatic Artery
        From aorta, high oxygen concentration.
      - To liver: Hepatic Portal Vein
        From small intestine, blood rich in digested food.
      - From liver: Hepatic Vein
        To vena cava, low oxygen concentration.
    - LUNGS
      - To lungs: Pulmonary Artery
        Low oxygen concentration, from heart
      - From lungs: Pulmonary Vein
        High oxygen concentration, to heart
- Tissue Fluid
  - Blood is made from; Red blood cells, white blood cells, platelets, plasma.
  - Tissue fluid is the liquid that bathes the surrounding cells. It lacks the large proteins in the plasma because they cannot pass through the capillary membrane.
    - Oxygen passes into the cells from the tissue fluid. Carbon dioxide and waste products pass into the tissue fluid from the cells.
  - Some tissue fluid does not drain back into the blood.
    - This becomes lymph
      - The lymph vessels then empty back into the subclavian veins.
  - How tissue fluid is made: Liquid leaves the capillaries at the venus end due to high hydrostatic pressure.
    - It then re-enters the blood at the other end by osmosis due to the lowered water potential in the blood.
      - The lower water potential in the blood is due to the large proteins.
- Haemoglobin
  - In the lungs
    - Haemoglobin associates with oxygen.
    - High partial pressure of oxygen.
    - Haemoglobin has a high affinity for oxygen here.
    - Haemoglobin becomes saturated with oxygen.
  - Respiring tissues
    - Haemoglobin dissociates with oxygen.
    - Low partial pressure of oxygen here.
    - Haemoglobin has a low affinity for oxygen here.
  - Oxygen-dissociation curves
    - Shift to the right
      - Low affinity for oxygen.
      - Right=releases
    - Shift to the left
      - High affinity for oxygen.
      - Left=loves
    - Exercise: Shift to the right called the 'Bohr Shift'
      - Muscles contracting more, so greater amounts of carbon dioxide produced.
        Acidity causes increase in the amount of oxygen to be released for the respiring tissues.
    - Small endotherms: Shift to the right.
      - They need to respire rapidly because they have a large SA:Vol and so lose heat quickly.
    - Low oxygen levels: Shift to the left
      - Haemoglobin can become fully saturated with oxygen even when the surroundings are at a low partial pressure.
    - Foetal haemoglobin: Shift to the left.
      - Foetal blood will become saturated when the adult haemoglobin is releasing oxygen.
    - Myoglobin: Shift to the left.
      - This is a pigment in the muscles which stores oxygen. It becomes saturated with oxygen when oxygen is released by haemoglobin.
- Transport in Plants
  - How water crosses the root.
    - The root hair cell will have a lower water potential than the soil, so water moves in by osmosis. The water potential in the xylem is the lowest so the water will move towards the xylem.
    - The APPOPLAST pathway: via the cell wall.
      - The casparian ***** causes the water to go through the cell membrane which allows for screening.
    - The SYMPLAST pathway: via the cytoplasm.
  - Th way water moves up the xylem.
    - Cohesion-tension theory.
      - Water moves into the xylem by osmosis. It is then drawn up the xylem since transpiration from the leaf causes tension.
        The molecules of water form a continuous stream due to the cohesion between the water molecules. The water diffuses out of the stomata in the leaves.
    - Root pressure
      - Cells around the xylem secrete minerals which decreases the water potential. More water moves into the xylem by osmosis. This creates a push from beneath.
  - Potometer
    - This is used to measure the rate of water uptake or the rate of transpiration by a plant.
- The Cell Cycle.
  - Interphase consists of 3 phaese; The first growth phase, Synthesis (DNA replication), Second growth phase.
  - Before a cell has divided the DNA is checked to make sure the replication is correct.
  - DNA mutations disrupt the cell cycle. This can be caused by: Radiation, smoking, chemicals, pollutants, viruses.
- Polysaccharides
  - These are long chains of many monomers joined together by glycosidic bonds.
  - Starch.
    - Plant storage polysaccharide made of ALPHA glucose.
    - It is insoluble and so does not change the water potential of the plant cell.
    - It is a mixture of amylose and amylopectin.
      - Amylose: 1-4 bonds, helix with hydrogen bonds.
      - Amylopectin: 1-4 and 1-6 bonds, more ends so broken down quicker.
  - Glycogen
    - Animal storage polysaccharide, made of ALPHA glucose.
    - Mainly in the muscle and liver cells.
    - It has 1-4 bonds with some 1-6. so it can be broken down rapidly.
  - Cellulose.
    - structure in plant cells, made of BETA glucose.
    - They had 1-4 bonds but alternate glucose molecules are inverted.
    - They form straight chains which are linked together by hydrogen bonds to form microfibrils.
      - Microfibrils are strong and rigid.
- Meiosis
  - Produces gametes which contain a haploid nucleus.
    - Responsible for variation.
  - DNA unravels and replicates so there are two copies of each chromosome called chromatids.
    - The DNA condenses to form double-armed chromosomes.
      - Meiosis I - the chromosomes arrange themselves in homologous pairs.
        The homologous pairs are then separated, halving the chromosome number.
        Meiosis II - the pairs of sister chromatids are separated.
        Four Haploid cells that are genetically different.
        
        Chromatids wrap around each other. Crossing over ocurs.
- Mitosis
  - Interphase - DNA replication/growth.
  - Prophase - DNA condenses, chromosomes visicle as sister chromatids joined at the centromere, spindle apparatus forms, nuclear membrane disintegrates.
  - Metaphase - Centromeres line up on equator, spindle fibres attach to chromosomes and pull apart by centromeres.
  - Anaphase - Spindle fibres shorten, pulling chromosomes to the poles.
  - Telophase - When reach different poles nuclei membrane reforms, spindle apparatus disappears.
  - Followed by cytokinesis.
- Courtship
  - To select a healthy mate.
  - To avoid aggression especially in solitary animals.
  - To ensure mating occurs with a member of the same species.
  - To synchronise breeding behaviour.
- Classification
  - Kingdom--> Phylum--> Class--> Order--> Family--> Genus--> Species.
  - Species: A group of similar organisms that can reproduce to give fertile offspring.
  - The name given to an organism is the genus then species.
  - There are no overlap between taxonomic groups.
  - DNA hybridisaton.
    - DNA from two different species are collected and the hydrogen bonds are broken so they are only single stranded.
      - Where the base sequences are the complementary the single strands will form hydrogen bonds.
        The DNA is then heated to separate the strands. The higher the temp. the more hydrogen bonds formed so the more alike the species are.
- Antibiotics and Resistance
  - They are drugs that inhibit or kill the growth of a bacteria.
  - Inhibiting the synthesis of the protein links between the molecules in the cell wall.
    - By interfering with protein synthesis.
      - By inhibiting DNA replication.
  - Vertical gene transmission
    - Bacteria reproduce asexually, if the parent bacteria has the gene for resistance then it is passed to the daughter bacteria.
  - Horizontal gene transmission
    - Two bacteria join by a cytoplasmic bridge, a plasmid containing the resistance gene is replicated and passed to the other bacteria. Called conjugation.

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Biology 2

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