Biology

• The nucleus contains the genetic information of the cell. The genetic information is within structures called chromosomes. Humans have 46 chromosomes, which are arranged in 23 pairs. You get 23 chromosomes from your mother and 23 chromosomes from your father. The chromosomes contain genes
• Cell division is a process in the cell cycle. This process is called mitosis.
• Mitosis is the division of one cell to form two identical daughter cells. Cell division produces the cells needed for growth and development in multi-cellular organisms
• Stage 1 of the cell cycle is called the prophase. This is the longest part of the cell cycle.

  During stage 1, a copy of each chromosome is made.

  There is also an increased number of subcellular structures getting ready for cell division
• Stage 2 in the cell cycle is called the prometaphase.

  Mitosis occurs during this stage.

  During stage 2, the nucleus of the cell divides and one set of chromosomes is pulled to each end of the cell.
• Stage 3 of the cell cycle is called the metaphase.

  During stage 3, the cytoplasm and cell membrane divide to form 2 identical daughter cells and a new nucleus is formed.
• Cytokinesis is when cells seperate
• Differentiation is the process by which cells become specialised for their roles
• Animal cells contain ribosomes, mitochondria, cytoplasm, nucleus and cell membrane
• Plant cells contain; ribosomes, mitochondria, nucleus, cytoplasm, cell membrane, vacuole, chloroplasts and a cell wall
• The nucleus is the largest structure in a cell, it contains DNA. Its function is to control all activities of the cell
• The mitochondria has an oval shaped structure. Aerobic respiration takes place in the mitochondria, which releases energy for the cell to use
• Ribosomes have a very small circular structure in the cytoplasm. Its function is the site of protein synthesis (where proteins are made)
• The cell membrane is a thin semi-permeable membrane that surrounds the structures in the cytoplasm.

  Function: it controls what substances go in and out of the cell
• The cytoplasm is a gel-like substance inside of the cell.

  Function: where most chemical reactions take place
• The cell wall (plant cells only) are made of a tough but flexible material called cellulose.

  Function: strengthens the cell and provides support
• The Permanent Vacuole (plant cell only) is a large sack which contains sugars and salts dissolved in water (sap)

  Function: stores sap, helps to keep plant cells rigid
• The chloroplasts (plant cell only) contains chlorophyll

  Function: absorbs light for photosynthesis
• Nerve cells are specialised to carry electrical impulses which provide rapid communication systems between different parts of the body of an animal.

  They have several adaptions including;

  • the synapse (nerve endings) are adapted to pass impulses to another nerve cell
  • an axon which transmits signals to nerve cells, muscles and glands
  • an axon covered in fatty sheath to speed up impulses
• Muscle cells are specialised in that they can contract and relax.

  Their adaptions include:

  • contains special proteins
  • contains many mitochondria
  • stores glycogen, a chemical that when broken down to glucose, is used in cellular respiration
• Sperm cells contain genetic information from the male parent.

  Their adaptions include:

  • a long tail that moves rapidly from side to side
  • a middle section full of mitochondria
  • the acrosome stores digestive enzymes to break down the outer layer of the egg
  • a large nucleus containing the genetic material of the father
• Chromosomes contain genetic information for the cell. The chromosomes contain genes
• when cells differentiate it means that they become specialised to perform certain functions.
• Some cells are made from adult stem cells differentiating
• Adult stem cells are found in adults. Adults have far fewer stem cells. These adult stem cells are undifferentiated and multipotent as they can differentiate into a limited number of specialised cells
• Adult stem cells are important for maintaining and repairing specific tissues in the body
• Stem cells are also used for medical purposes such as;

  • repairing damaged skin from severe burns
  • repairing damaged eyes from chemical burns
  • treating type 1 diabetes
• Stem cells are found in plant meristems. They can be used to make clones which give us many advantages such as:

  • very quick and economical
  • produces a large number of rare plants which can save them from extinction
  • Horticulture - fruits, vegetables, flowers
  • Agriculture
• Embryonic cells are present in embryos before any specialisation has occurred.
• The embryonic stem cells are able to differentiate into any type of specialised cell.
• Embryonic stem cells are the inner cells of an embryo. They are formed after fertilisation.
• Embryonic cells are undifferentiated and totipotent cells as they can differentiate into any specialised cell in the body
• What is an active site?

  the site on an enzyme where the reactions bind
• What are amino acids?

  molecules made up of carbon, hydrogen, oxygen and nitrogen that are the building blocks of protein.
• What is amylase?

  an enzyme which speeds up the digestion of starch into sugars.
• What is bile?

  neutralises stomach acid to give a alkaline pH for the enzymes from the pancreas and small intestine to work well. It is not an enzyme.
• What are carbohydrases?

  enzymes that speed up the breakdown of carbohydrates into simple sugars
• What are carbohydrates?

  molecules that are made up of carbon, hydrogen and oxygen. They provide the energy for metabolism.~

  They found in foods such as: rice, potatoes and bread.
• What is a catalyst?

  a substance that speeds up the rate of a reaction
• What is the definition of 'denatured?

  the breakdown of the molecular structure of a protein so it no longer functions