Biology Unit 1 AOS 1

• The nucleus is the control centre of the cell, containing DNA.
• A prokaryotic cell are small and simple cells
• Eukaryotic cells are complex
• Osmosis is from a high concentration of water to a low concentration of water
• Facilitated diffusion is from high to low concentration through protein channels
• Simple diffusion is from an area of high concentration to low concentration
• Active transport is from an area of low concentration to high concentration
• Bulk transport consists of two ways: endocytosis and exocytosis
• Endocytosis is when large particles enter the cell
• Exocytosis are large particles exiting the cell
• When solids are taken into the cell through endocytosis its called Phagocytosis
• When fluids are taken into a cell by endocytosis it is known as Pinocytosis
• The smaller the cell the larger the surface area to volume ratio
• Hypotonic is less solute and more water
• Hypertonic is more solute and less water
• Isotonic are solutions with the same concentration
• Animal cells losing water is called crenation
• Plasma membrane is mainly composed of 2 chemicals: phospholipids and proteins
• The fluid mosaic model explains the semi permeable nature of the plasma membrane
• The phospholipid bilayer make up the structure of the plasma membrane
• Passive transport:

  Diffusion (simple and facilitated) and Osmosis
• Active:

  Active transport and Bulk transport (endocytosis and exocytosis)
• When plant cell loose water its called Plasmolysis
• When an animal cell takes in water until it bursts its called cytolysis
• When a plant cell takes in solution until its tight with it, its called turgid
• DNA is a macro molecule
• Polymers and made with a large number of monomers
• A monomer of DNA is called a nucleotide
• A nucleotide has three components, phosphate group, pentose sugar and a nitrogen base. There are four nitrogen bases: adenine, thymine, cytosine and guanine.
• Two strands of DNA are anti parallel as they are next to each other but run in different directions
• When DNA replication happens, the DNA helicase breaks the hydrogen bonds between the strands exposing the nitrogen bases. The DNA polymerase which works only on 3' to 5' direction starts joining complimentary nucleotides to make a new strand. The strand that runs from 5' to 3' makes a new strand in pieces called Okazaki fragments. The DNA ligase joins the fragments to make one complete strand.
• The strand that runs from 3' to 5' is called the leading strand, the one that runs from 5' to 3' is called the lagging strand
• Mitosis is in body cells and meiosis is in reproductive cells
• In mitosis there are two daughter cells with identical chromosomes while in meiosis there are four haploid daughter cells with half the number of chromosomes
• The head of the a phospholipid molecule loves water therefore is called hydrophilic, whereas the tail hates water and is called hydrophobic
• In mitosis, two genetically identical daughter cells are made
• In meiosis, four genetically different daughter cells are made
• In animal cells, the cleavage furrow occurs from the outside and moves towards the center, this is called Centripetal.
• In plant cells, the cell plate forms in the center and moves laterally, this is called Centrifugal.
• During DNA replication a single DNA strand is wrapped around a histone protein