Biology, 1.1, 1.2, 1.3 1.4, 1.5, 1.6 of AS unit 1

• A polar molecule, which has no overall charge.
• When 2 water molecules contact, opposites attract, forming a Hydrogen bond.
• The sticking together of water molecules is called Cohesion.
• High surface tension.
• Water is a solvent.
• Water has a specific heat, a large anount of water is needed to heat water.
• High latent heat.
• Maxium density is 4 degrees.
• Ice is less dence than water.

Water potential

• The higher WP implies a greater tendency of water to leave a system. Water will diffuse from a region of less negative (higher) WP to one of more negative (lower) WP.

• Contain carbon, hydrogen, oxygen.
• Two main functions,
  • Act as a source of energy for plants + animals.
  • To play a structural role in plant cell walls, eg Cellulose.
• Monosaccharides
• Relitivly small molecules, (CH20), building blocks for bigger ones.
  • When n= 3 Triose- metabolism.
  • When n= 5 Pentose- Nucleic acid.
  • When n=6 Hexose- eg glucose, main source of energy.
• Disaccharides
• Two Monosaccharides linked together.
• Formed by a Glycosidic bond, this eliminates water, this is called a Condensation reaction.

           Monosaccharides     Disaccaharides           Found

• Glucose+Glucose=         Maltose:             Malt sugar
• Glucose+Fructose=        Sucrose:            Cane sugar
• Glucose+Galactose=       Latose:              Milk sugard
• Polysaccharies
• Large complex molecules. Many monosaccharides together.
• 2 types: Starch (plants) and Glycogen ( animals)

Nucleus

• Controles the cells activity and retains chromosomes.
• Bound by a double membrane, the nuclear memebrane (Nuclear envelope) has pores in it to allow transport or mRNA and nucleotides.
• Contains coils of chromatin. The nucleolous makes RNA needed for Ribosomes.

Mitohondria

• Double membrane,
•  
• Aerobic respiration occurs here.
• Production of ATP.

Endoplasmic reticulum

• Rough ER and Smooth ER.
• Rough ER has Ribosomes on the out side of it. Transports protiens made by the ribosomes, found in large cells.
• Smooth ER has membranes with less ribosomes. Concerned with the nucleolous.

Ribosomes

• 1 large + 1 small sub unit. Made in the nucleolous, from ribosomal RNA and protein. Improtant in protein synthisis.

Golgi body

• Similar to the ER but more compact. Formed by rought ER.
• It is like a packaging center, as it packages and then sends of proteins.

Lysosomes

• Small vacuoles are formed when portions of the golgi body are pinched off.
• Contains digestive enzymes.
• Destroy worn out cells.

Centrioles

• Found in animal cells.
• 
• Located outside the nucleous.

The following things are all found in plants.

Chloroplast

• Found in photosynthesising tissue.
• They have a double membrane.
• Used to make energy from light energy.

Vacuole

• A large fluid- filled membrane sac, with a single membrane (The tonoplast)
• Contains cell sap.
• Used as structural support for the cell.

Cellulose cell wall

• Cell wall consits of cellulose microfibrils.
• Main functions:
  • Provide strenghts+ support
  • Permit the movement of water from the cell to cell.

Prokaryote                                                                   

·       No membrane bound organelles.

·        Found in plants, animals, fungi and protocists.

·       DNA lies free in the cytoplasm.

·         Membrane bound organelles.

·       No nuclear membrane in ER.

Eukaryotic

·       DNA located in chrosomes.

·       Ribosome’s are smaller.

·       Distinct membrane bound nucleus.

·       Cell wall containing marein.

·       Ribosome’s are larger.

        Cell wall in plants made of cellulose

Mitosis

• Mitosis produces two daughter cells geneticaly identical to the parent cell.
• Interphase- Longest part, produces organelles. DNA is doubled during this period.
• Prophase:
  • Chromosomes condense, to long thin threads.
  • The centrioles devide, and move to opposite ends of the cell.
  • Protein microtubules form from each centriole and a spindle develops from pole to pole.
  • Nuclear membrane distegates and nucleolus disappears.
  • Pairs of chromatids can be clearly seen.
• Metaphase-Chromosomes arange themselves at the center of the spindle.
• Anaphase- Rapid stage.
  •   Centromere splits and spindle fibers contract and pull chromatids to the poles.
• Telophase- The final stage.
  • Chromsomes at the poles, they then uncoil and lengthen,
  • spindle brakes down,
  • centrioles replicate, Nucleoli appears.
  • A new cell wall is laid down.

Meiosis

• Two devisons resulting in 4 daughter cells. The number of chromosomes are halved.
• Homologous chromosomes pair up.
• Daughter cells are genetically different.

Meiosis and variation

• Sources of variation are essential.
• Three different ways to create variation.
  • Each of the chromosomes carry different genetic material.
  • Pairs of homologous chromosomes arrange themselves randomly on the spindle during metaphase. 
  • Crossing over during chiasmata formation during prophase.+