biology

• Cells

  All living organisms are made up of cells. Cells are the basic unit of living organisms. They provide structure and carry out certain functions. There are two different types of cell.
• Eukaryotic cells are found in plants, animals, fungi and protists. They are 10-100 micrometers in size. A eukaryote is an organism made up of eukaryotic cells
• Prokaryotic cells are 0.1-5.0 micrometers in size. A prokaryote is an organism made up of prokaryotic cells
• Prokaryotic cells have plasmids

  • Prokaryotic cells may have one or more small rings of DNA, which are called plasmids
  • These plasmids can replicate and move between cells so genetic information can be shared
• Plasmid cells have no mitochondria or chloroplasts

  • Plasmid cells store their DNA in a single DNA loop in the cytoplasm
• Animal cell contains

  • Cell membrane- separates the interior of the cell from the environment outside, it is selectively permeable (it can control substances moving in and out of the cell)
  • The nucleus contains chromosomes which contains the cell's genetic material
  • Ribosomes are responsible for synthesising proteins
  • Mitochondria is where aerobic respiration takes place, it uses glucose and oxygen to release energy
  • Cytoplasm is a jelly like fluid that fills the cell, it is where most of the cell's chemical reactions take place
• In addition to the sub-cellular structures found in an animal cell, a typical plant cell also has:

  • The vacuole is a large sac in the middle of the cell that contains a watery solution of sugars and salts (cell sap). It helps maintain the structure and shape of the cell.
  • Chloroplasts contain chlorophyll which is needed in the process of photosynthesis
  • The cell wall surrounds the cell, it is made of cellulose, increases the structural strength of the cell
• Bacterial cells contain

  • a cell membrane and a cell wall which provide structure for the cell
  • cytoplasm is a jelly like fluid that fills the cell, it is where most of the cell's reactions take place
  • some bacteria have flagella, whip like structure used for movement
  • plasmids are small rings of DNA
  • ribosomes are responsible for making proteins
• Sperm Cell


  Sperm cells are specialised to fertilise egg cells. To do this, they need to travel long distances relative to their size. They then break through to the egg cell and fertilise it (combine the sperm DNA with the egg DNA).
• The head contains the sperm's nucleus. The nucleus carries one half of the organism's genetic material. This combines with the egg's half of the genetic material to fertilize the egg.

  • Acrosome- contains enzyme needed to penetrate into an egg cell.
  • The middle section contains lots of mitochondria to provide sperm with energy it needs to travel to reach the egg cell
  • The tail allows sperm cells to travel towards egg cell

  
• Egg cell

  The egg cell is fertilised by a sperm cell to become a zygote (which grows into an embryo). An egg cell is much larger than a sperm cell and it is specialised to support the zygote as it grows.

  • The nucleus contains half the genetic information
  • cytoplasm is large and packed full of nutrients that the zygote will need to grow
  • cell membrane is adapted to change structure once the egg is fertilised so no more sperm can get into the egg cell
• 
  

  Ciliated Epithelial cells line the airways. Their function is to waft mucus (which traps harmful microorganisms) to the back of the throat to be swallowed.

  • The cells have hair like structure on them called cilia which can be moved in unison.
  • These cells contain many mitochondria to provide them with energy to move
• In osmosis:

  the concentrations become the same on both sides of the membrane, water moves where there are less water molecules
• signs of plant disease

  • spots on leaves
• signs of plant disease

  • spots on leaves
  • areas of decay
  • stunted growth
• Producing Monoclonal Antibodies

  1. A mouse is injected with the chosen antigen (obtained from pathogen
  2. The mouse's immune system responds by producing lymphocytes that produce the particular antibody
  3. The lymphocytes are extracted from the mouse and fused with myeloma cells to form hybridoma cells
  4. The myeloma grows rapidly and lots of identical cells are produced. All of the hybridoma cells produce the same antibody
  5. These monoclonal antibodies are collected, purified and then can be used to target specific cells and chemicals
• To identify a plant’s disease, you may refer to a gardening manual or website, take infected plants to a laboratory to identify the pathogen by looking through a microscope or use testing kits that contain antibodies.
• Tissue Culture

  1. A tissue sample is taken from a plant
  2. The tissue sample is sterilised
  3. The cells are grown on an agar plate and hormones that cause cell division are added
  4. Hormones that cause roots and stems to form are added to the callus
  5. The individual plants are planted into soil
• The immune system is made up of lots of different white blood cells, which each have different functions.
• Types of Pathogens

  • Virus
  • Bacteria
  • Fungi
  • Protist
• In plants, the stages of growth happen in three different regions: the zone of cell division, the zone of elongation and the zone of differentiation.
• Infections are caused whenever a foreign pathogen invades an organism.
• Consequences of sexual reproduction

  • increases genetic variation
  • increases chances of surviving natural selection
• How can we use microscopy to study the cell cycle?

  • Microscopes allow us to see things we can't with the naked eye.
  • By culturing cells and then viewing them at a high resolution under a microscope, we can identify different cells in different stages of the cell cycle.
• The Human Genome Project has advanced our knowledge, which should lead to the following:

  • advances in gene therapy
  • personalisation of medicine
  • identification of genes linked to disorders
  • improved understanding of inherited disorders
• Accommodation is the process of the eye changing lens shape in order to focus on an object as its distance from the eye changes.
• CO2 diffuses from the bloodstream into the lungs, urea is removed from cells
• Viral Reproduction

  1. Viral invade host cells
  2. The virus particle inserts its own DNA into the host cell's DNA, which is then copied and used to make more viruses
  3. Once the new viruses have been synthesised, they cause the cell to burst, releasing new viruses to invade new cells
  4. The cell damage makes us feel ill
• Phagocytosis


  A white blood cell finds the pathogen and engulfs it by changing shape. The white blood cell ingests (absorbs) and digests the pathogen, destroying it.
• Short-sightedness and long-sightedness are traditionally treated using spectacles fitted with lenses. Modern alternative treatments include contact lenses, laser eye surgery, and replacement eye lenses.
• The following can sometimes reproduce both sexually and asexually:

  • Fungi
  • Malaria parasites
  • Strawberry plants
• GM crops generally have higher yields than normal crops. They could be a solution to providing the nutrients that many people in developing nations do not consume. Golden rice is an example of this: it helps reduce Vitamin A deficiency.
• Coronary arteries can become narrowed as a result of a build-up of fatty deposits. As a consequence, blood flow is reduced, leading to a lack of oxygen being supplied to the heart muscle.
• The two main sources of evidence for evolution are:

  • antibiotic resistance
  • fossils
• Carl Woese's three-domain system includes:

  • Archaea
  • Bacteria
  • Eukaryota
• The main technique that we use to help the immune system to recognise and destroy pathogens is vaccination. Immunising a large proportion of the population will make it very hard for a pathogen to be spread. This is called herd immunity.
• Vaccination can make people immune to infection. The more individuals that are vaccinated, the less likely the disease is to spread.
• Antibiotics are designed to cure infections caused by bacteria.
• Meiosis

  1. The two pairs of chromosomes found in the parent diploid cell replicate
  2. The diploid cell then divides twice to give four genetically distinct gametes, each with half the chromosomes of the parent diploid cells (haploid)
  3. During sexual reproduction, the male gamete fertilises the female gamete, restoring the normal number of chromosomes
  4. Once the gametes have combined, the new cell divides by mitosis which increases the number of cells. As soon as the embryo reaches a threshold size, cells begin to diffrentiate
• DNA is a polymer made up of two long strands of small units that repeat throughout the structure, called nucleotides. Each of these is made up of a sugar, a phosphate and a base attached to the sugar.